Review of molten carbonate-based direct carbon fuel cells

MCFC is a commercial fuel cell. Its scale is gradually expanded from kilowatt to megawatt [84]. Besides gaseous fuel, solid carbon is also used ... Skiptomaincontent Advertisement SearchSpringerLink Search Reviewofmoltencarbonate-baseddirectcarbonfuelcells DownloadPDF DownloadPDF AbstractDirectcarbonfuelcell(DCFC)isapromisingtechnologywithhighenergyefficiencyandabundantfuel.Todate,avarietyofDCFCconfigurationshavebeeninvestigated,withmoltenhydroxide,moltencarbonateoroxidesbeingusedastheelectrolyte.Recently,therehasbeenparticularinterestinDCFCwithmoltencarbonateinvolved.Themoltencarbonateiseitheranelectrolyteoracatalystindifferentcellstructures.Inthisreview,weconsidercarbonateasthecluetodiscussthefunctionofcarbonateinDCFCs,andstartthepaperbyoutliningthedevelopmentsintermsofmoltencarbonate(MC)-basedDCFCanditselectrochemicaloxidationprocesses.Thereafter,thecompositeelectrolytemergingsolidcarbonateandmixedionic–electronicconductors(MIEC)arediscussed.HybridDCFC(HDCFCs )combiningmoltencarbonateandsolidoxidefuelcell(SOFC)arealsotouchedon.Theprimaryfunctionofcarbonate(i.e.,facilitatingiontransferandexpandingthetriple-phaseboundaries)inthesesystems,isthendiscussedindetail.Finally,someissuesareidentifiedandafutureoutlookoutlined,includingacorrosionattackofcellcomponents,reactionsusinginorganicsaltfromfuelash,andwettingwithcarbonfuels. IntroductionFuelcells(FCs)offeranenvironmentallyfriendlyandhighlyefficientapproachtoenergy-conversiontechnologyforpowergeneration.Thisapproachhasbeenintensivelyinvestigatedforoverahundredyears,sinceGroveetal.[1]developedthefirstFCin1839.Thistechnologyissteadilyevolvingandimproving,asthedemandforelectricityandnewelectricitygenerationtechnologiescontinuestogrow.TheFCdevicegenerateselectricpowerfromgaseousfuels(hydrogenorsyngas)byreformingliquefiedpetroleumgasorliquidfuels.However,thecomplexsynthesisprocessandthestorageandtransportationrequirementsincreasethecost.Atpresent,theutilizationofcarbonfuelsisstillapreferredoptionforthedevelopmentofFCs,duetotheabundantresources,easyaccessandrelativelyhigh-energydensity.Directcarbonfuelcells(DCFCs),asanenergy-conversiontechnology,generateelectricityfromsolidcarbonfuelsthroughelectrochemicalreactions[2,3].Thedevicehasahigherenergy-conversionefficiencyratethantraditionalpowergenerationdevicesofheatengines,whichminimizesystemcomplexityandthusensurealowercost[4].ThefirstDCFCwasreportedbyBecquerel[5]inthemiddleofthenineteenthcentury;theconfigurationwasacarbonrodinaKNO3solutioninsideaplatinumcontainer.In1896,WilliamJacques[6]developedalarge-scaleDCFCusing100singlecells,andbakedcoalastheanode.TheelectrolytewasanunspecifiedmixtureofKOHand/orNaOHandthecathodewasironpots.Initially,theactualreactioninthissystemwasonlydeemedtobethechemicalreactionofcarbonwithnitrate[7].Laterresearchreportedthatgasesfromsolidcarbonpyrolysisareinvolvedintheelectrochemicalreaction[8,9].OtherresearchersfromStanfordResearchInstitute(SRI,International)investigatedthistechnologythoroughlyandinventedtheactualdevicesforelectricitygenerationbytheelectrochemicaloxidationofcarbon[10,11].DCFCtechnologyisagainreceivinginterest,especiallyintermsofthedirectcarbonoxidationmechanism.Gür[12,13]proposedthatitisappropriatetonamethecarbonfuelcella“direct”carbonfuelcellifthereactionisachievedinasingleprocedureorasinglechamber.Thisproposalisbasedonthesimplifiedreactionsintheanode.However,itismuchmorecomplicatedinpractice.Generally,morethanonereactionhappensintheanodesimultaneously.Amongthosereactions,carbonisoftenoxidizedintocarbonmonoxideasanintermediateproduct,andthenCOisoxidizedintoCO2asthefinalproduct.Weusetheterm“directcarbonfuelcells”formostcarbonfuelcellstobeconsistentwithmostpublications.OneadvantageofDCFCistheemissionofpureCO2,unlikeothercoal-firedpowerplants,whichreducethetechnicaldifficultiesofCO2captureandseparation[14].Notably,theDCFCpowerstationhasamodularstructuredesign,whichcanbeadjustedregardingthecost[15].ThedirectutilizationofvarioussolidcarbonaceousmaterialsasfuelsisthemostdistinctivefeatureofDCFC.Somesolidcarbonfuels,likegraphite,carbonblack[16,17,18,19,20,21,22,23]anddifferenttypesofcoalfuel[24,25,26,27,28,29]havebeenusedinvariousDCFCconfigurations.Thecarbonaceousmaterialsobtainedfromrenewableresources(e.g.,biomassandorganicwaste)aresustainablefuelsduetoabundant,cheapandnaturalcharacteristics[30].Inrecentdecades,manyresearchershavefocusedontheapplicationsofbiocharintheenvironmentandcatalysisfields[31,32,33,34].BiomassandmunicipalwastearealsosuggestedasrawmaterialstoproducecleanenergyinDCFCs[35,36,37].Bio-charissuitableinDCFCforelectricenergygenerationbecausethebiocharobtainedbypyrolysisisamorphous,whichisconducivetotheexposureofcarbonfuelsurfaceactivesites.Anotherfeatureisthehighporosityofthiskindofbiochar,promotinggastransportationinthereactionprocess[38].Furthermore,somenaturalmetalionsdisperseuniformlyinbiochar,whicharenaturalcatalystsforthecarbongasificationreaction[39].Itisworthmentioningthattheefficiencyofbiomass-fueledDCFCisgenerally50–60%,whileitisupto80%ifheatandelectricityco-generationisapplied[40].TherearethreetypesofDCFC;thesearecategorizedaccordingtotheelectrolytematerial,i.e.,hydroxide,carbonateandsolidoxide.Ofthese,themoltencarbonatedirectcarbonfuelcell(MC-DCFC)wasoneoftheearliestcells,andithasbeenwidelystudied[41].Themoltencarbonatealsoremainsstablecomparedtohydroxide-basedcells,eveninanenvironmentrichinCO2,whichhelpstopreventelectrolytedamage[42,43].Recently,aninvestigationwasdoneonhybriddirectcarbonfuelcells(HDCFCs),usingmixedsolidcarbonandcarbonateintheanode[21].Thisovercomescorrosionissuesassociatedwiththemoltencarbonatefuelcell(MCFC)andyieldsslightlyfasterkineticscomparedtothesolidoxidefuelcell(SOFC)system[21].SomereviewshavebeendoneinDCFC,withtheearliestreviewsofDCFCdonebyHoward[44]andLiebhafsky[45].Later,Caoetal.[46,47]andGiddeyetal.[48]summarizedthefundamentalelectrochemicalperformanceandthedevelopmentsofDCFCtechnology.ThereactionmechanismofdirectcarbonoxidationandtheconversionwasexplainedbyCooperetal.[49]andGür[13,50].Then,Radyetal.[51]reviewedtheperformanceofvariousfuelsusedinMCFCsandSOFCs,andZhouetal.[52]publishedareviewpaperthatdiscussedtheanodeusedinDCFCs.Recently,Jiangetal.[53]presentedanoverviewoftheimpactofdifferentparametersontheresistanceandpoweroutputandtheelectrochemicalbehaviorofDCFCs,andalsosummarizedthechallengesassociatedwithdevelopingDCFCs.Glennetal.[54]reviewedthecarbonelectro-catalysismechanismofalkalimetalmoltencarbonatesinDCFCs.Thispaperfocusesonprovidingabroadandtimelysummaryofthecarbonate-basedDCFC:MC-DCFC,CO32− + mixedionic–electronicconductors(MIEC)andCO32− + SOFC.TheconfigurationsofthreecellsystemsandsomepossiblereactionsrelatedtocarbonateareshowninFig. 1.Thisreviewstartswithanintroductiontomoltencarbonatespecies.Then,thefundamentalmechanismsofdifferenttypesofDCFCareprovided,withthefocusbeingonthefunctionsofcarbonate:(1)transportionsasanelectrolyte;(2)catalyzecarbonoxidationasacatalyst;(3)enlargethereactionarea,thatis,theanode/electrolytereactioninterfacezone.Thereviewconcludeswithasynopsisofsomeissuesregardingcorrosion,compatibilityandwettability,andapossiblefutureoutlookregardingtheutilizationofcarbonateinDCFC.Fig.1SchematicofaDCFCinthepresenceofcarbonate,includingthreecellsystems(MC-DCFC,CO32− + MIECandCO32− + SOFC)andsomepossiblereactions.Theprimaryreactionbetweencarbonateandcarbonisshowninlightblue;theelectro-catalyticreactionofcarbonatewithcarbonisshownindarkblue;andthepossiblesidereactionisshowningreenFullsizeimageSpeciesofmoltencarbonateinDCFCMoltencarbonateiscommonlyusedinMCFC,andhasreceivedwideattentioninDCFC[4,49].ItshowsgoodcompatibilitywithCO2whenusedasanelectrolyte[55,56],andprovidesexcellentionicconductivityatarelativelylowtemperature[57].Furthermore,themoltencarbonateintheanodechambercansignificantlyenlargetriple-phaseboundaries(TPBs),whichfavorsiondiffusiontotheelectrochemicalreactionsites[21].ManystudieshaveshownthatdopingalkalimetalionsinmoltencarbonatecaneffectivelyacceleratethereactionrateofcarbongasificationinaCO2gasstream[58,59,60].Inparticular,potassiumsaltdelivershighcatalyticactivityforthecarbongasificationreaction[61].TheoperatingtemperatureofDCFCsisreducedbychangingthecarbonatecompositionwhilemaintainingcellperformance,whichisanotherpositivefactorwhenusingmoltencarbonateastheelectrolyte[62,63].Asuitableamountofothercarbonatesoroxidescanalsofurtherreducethemeltingtemperatureofthecarbonate[64].Forexample,addinganappropriateamountofRu2CO3andSrCO3toabinarycarbonatereducesthesurfacetensionofmoltencarbonate,which,inturn,increasesthesolubilityofgasandreducesthemeltingtemperature[65].Therefore,usingcarbonatewithdifferentcomponentsinDCFCisdiscussedindetail.BinaryBinarycarbonateeutectichasbeenwidelyusedasanelectrolytematerialinFCs.Itiswellknownthatalowermeltingpointisobtainedwithabinarycarbonateeutectic(Li2CO3–Na2CO3,Li2CO3–K2CO3,K2CO3–Na2CO3)thanwithasinglecarbonate[66,67].Ofthethreebinarycarbonates,Li–Kcarbonatehasthelowestmeltingpoint(below550 °C).Therefore,itismoresuitableforuseasanelectrolyteforthecell.However,anearlystudysuggestedthataLi–NacarbonateeutecticexhibitedcertainbenefitsincomparisonwithaLi–Kcarbonateeutectic,suchasahigherionicconductivity(theionicconductivityof43.5 mol%Li2CO3-31.5 mol%Na2CO3-25 mol%K2CO3,52 mol%Li2CO3-48 mol%K2CO3and72 mol%Li2CO3-28 mol%Na2CO3at600 °Cis1.20Scm−1,1.15Scm−1,and1.79Scm−1,respectively)[68].TheLi–Nacarbonateeutectichasalowerdissolutionrateofinthecathode(NiO)thanthatofNigeneratedbyNiOreduction,anditisquicklyoxidizedtonickeloxide[69].Thecelllifeofdifferentcarbonatecomponentsispredictedbasedontheevaporatedcarbonatelost.Li–Nacarbonatehasagreaterprojectedlifetimeof10.3 × 105 hat600 °C,comparedtothe6.4 × 105 hforLi-Na–Kcarbonateandthe6.3 × 105 hforLi–Kcarbonate[70].Therefore,Li–NacarbonatehasoftenbeenusedasanelectrolyteinMCFCtosubstitutetheLi–Kcarbonate.Nevertheless,theremaybeariskofarapiddecreaseincellvoltagewithLi–Nacarbonateatatmosphericpressureandlowtemperature(≤ 600 °C)becauseoftherelativelylowsolubilityofoxygeninthiseutectic[71].Na–Kcarbonateeutecticshowedtheworstcellperformanceofthevariousbinarycarbonate-basedDCFCs,probablyduetoitshighmeltingtemperature[72].Oneinvestigationshowedthat,whenusingsawdustbiofuel,HDCFCwithaLi–Kcarbonateeutecticasthemediuminanodeshowedexcellentcellperformance(789 mW cm−2)at750 °C[46].ThelowmeltingpointofLi–Kcarbonateisoneoftheinfluencingfactorsonexcellentcellperformancebecausetheviscosityofitssolutioncanbereducedwhenthetemperaturereachesthemeltingpoint,therebyimprovingthediffusionofsolidfuelinthemedium.Andalso,Li–Kcarbonateisagoodcatalystforgasificationreactions[22].Table1providesthemeltingtemperaturesofthecommoncarbonates.Table1MeltingpointofvariouscarbonatesFullsizetableTernaryAternarycarbonateeutecticoflithium,sodiumandpotassiumcarbonateasthecarbonoxidationmediumisapotentialchoiceinDCFCs.Initially,theternarycarbonateeutecticwasselectedasanelectrolyteinDCFCduetoitsgoodcompatibilitywithunexpectedpollutants,suchassulfurandashcontentsincoal[10].Furthermore,comparedwiththebinarycarbonateeutecticmixedDCFC,theternarysystem(Li2CO3–Na2CO3–K2CO3)hasthelowestmeltingpoint[73].(SeeTable1.)Vutetakisetal.[74]employedaternarycarbonateofLi2CO3–K2CO3–Na2CO3withaweightratioof32.1:34.5:33.4inDCFCwithcoalasthefuel,andfoundthatitwascapableofreducingthecelloperatingtemperatureto500 °C.Jiangetal.[75]alsoappliedaternarycarbonateofLi2CO3,Na2CO3andK2CO3inamoleratioof43.5:31.5:25incoal-fueledHDCFC.Thecellgeneratedamaximumpowerdensityof50.02 mW cm−2withanopen-circuitvoltage(OCV)of1.1 Vat700 °C.CarbonateinDCFCInDCFC,carbonatecancontactcarbonparticlesintheelectrolyteoranodecompartmentdirectly,tocatalyzethereactionofcarbonoxidation.ItcanalsobeusedasanelectrolyteforiontransportationinMC-DCFCandCO32− + MIEC.Thedifferenceisthat,inthemoltenstate,carbonatehasacatalyticeffectoncarbonoxidation,duetocarbonatemixingwithcarbonparticlesintheformersystem,butcarbonatecombineswithMIECmaterialsisasolidelectrolyteforminthelatter.ByintroducingcarbonateintheHDCFCanode,cellperformanceisimproved,possiblyduetothecatalyticeffectoncarbonoxidationandtheenlargementofthereactioninterface.Therefore,itiscriticaltodiscusstheroleofcarbonateinDCFC. Table2summarizessomeconfigurationsusedincarbonate-basedDCFCs.Table2VariousconfigurationsforthedirectcarbonfuelcellFullsizetableMC-DCFCMCFCisacommercialfuelcell.Itsscaleisgraduallyexpandedfromkilowatttomegawatt[84].Besidesgaseousfuel,solidcarbonisalsousedasfuelinthiscellsystem.SomeprogresshasbeenmadewithdevelopingdifferentcellstructuresandmaterialsofMC-DCFC,followedbydifferentelectrodereactionmechanisms.ConfigurationBauretal.[85]replacedallthemoltenhydroxideelectrolyteswithmoltencarbonateelectrolytes,whichopenedupthestudyofMCFCs.Inthe1970s,researchersfromSRIInternationalfirstdispersedacarbonparticleinamoltenPbusingamoltenalkalimetalcarbonateastheelectrolyte[86,87].Followingthefirsttrial,theresearchersusedcoalastheanodeinanMC-DCFCwithLi–Na–Kternarycarbonateelectrolyte[10].Somereportsclaimedthatsomealkalimetalsalts(suchasLi2CO3)areregardedasacatalyticagentforacceleratingcarbongasification[88,89],whichfurthersuggeststhepossibilityofusingcarbonateinDCFC.SomeresearchersfromLawrenceLivermoreNationalLaboratoryintheUnitedStates(LLNL,USA)thenmadesignificantprogressinMC-DCFC,particularlyintermsofthematerialsrelatedtocathodecatalysts,aerogelsandxerogelcarbonanodes[82,83,84,85,94].TheunconventionaltilteddesignwasinventedbyCooperetal.[95]usingmoltencarbonate(32 mol%Li2CO3-68 mol%K2CO3)astheelectrolyte(SeeFig. 2a).ThecellcathodeiscomposedofalithiatedNiO,whiletheanodeismadeofthecarbon-carbonateslurrymixtureandtheNicurrentcollector.ThekeyaspectofthisdeviceistheelectrolytebedofZrO2fabricfilledwithmoltensaltthatconductsionswhilepreventingashortcircuitoftheelectrodes.Thisdevicepresentsa5–45°inclinedangle,whichfavorsacontinuousfuelsupplyandfacilitatesthedischargeofexcesselectrolytetopreventtheelectrolytefromfloodingthecathode.Thecellsurfaceareawasexpandedfromtheconventional2–60 cm2withnosignificantpolarizationloss[48].Fig.2DifferentconfigurationsofMC-DCFC:aUnconventionaltiltedMC-DCFCfavoringthecontinuoussupplyoffuelthatensuresthereisnocorrosionofthecathode;bPlanarMC-DCFCwiththemixtureofcarbonandcarbonatelocatedabovetheanodetoensurelowcellresistance;cMC-DCFCwithastirringrodinthemoltencarbonatetoensureuniformdistributionofcarbonparticlesandimprovethemasstransferprocessinsidethecell;dFBEDCFCusingthebubblinggastoagitateamixtureofcarbonandmoltencarbonatetoacceleratemassandheattransfer;eTMC-DCFCwithaclosed-endstructurethatensuresthereisnoshortcircuitandthatthereisacontinuoussolidfuelsupply.Reproducedfromrefs.[41,95,96,98,99]FullsizeimageLater,researcherspresentedanothercarbon/airmoltencarbonatecell,asillustratedinFig. 2b.Thecompositeelectrodecomposedoffoamnickelandstainlesssteelmadeagreatcontributiontothestabilityofthecellstructure[41].Thisdesignwascalled‘planarMC-DCFC’duetothemixtureofcarbonandcarbonatelocatedabovetheanodewheretheredoxreactionsoccur.Alowcellresistance(theresistanceofcarbonaerogelandtheanodecurrentcollectorwas0.4 Ω cm2)wasobtainedinthisconfiguration,andthereforeimprovedcellperformance.AschematicoftheMC-DCFCpreparedbyLietal.[96]isshowninFig. 2c.ThemethodappliedwassimilartothatusedbyVutetakisetal.[74].ThisMC-DCFCconsistsofthreeelectrodes:aworkingelectrode(WE);agoldcounterelectrode(CE);anda12 mmdiameteraluminasheaththatservesasthereferenceelectrode(RE).AnInconelstirringbarisalsointroducedintothemoltencarbonateelectrolytetoensuretheuniformdistributionofcarbonparticlesandimprovemasstransferprocessinsidethecell.However,thepowerdensityinthisconfigurationisnotgoodenoughbecausethereactionarea(fuel/electrode/electrolytecontactarea)isseverelylimited.Inthiscase,thereactionareaisonlyafewsquarecentimetersinthe250 gmeltcarbonatebath[97].InanefforttoextendtheformationzoneofTPBs,afluidizedbedcellwithathree-dimensional(3D)electrodewasadoptedbyGürandHuggins[100].Zhangetal.[98,101]showedanotheronewithaself-designedfluidizedbedelectrodeanode,asshowninFig. 2d.Inthisdesign,thebubblinggasisappliedinDCFCtoensuremassandheattransfer.Recently,atubularDCFCwithaclosed-endstructurewasconceivedbyIdoetal.[99],usingcarbonateastheelectrolyte(SeeFig. 2e).Thisdesigncaneffectivelyprotecttheshortcircuitbetweentheelectrodesusingcarbonpowder.Additionally,thecontinuoussolidfuelsupplycanberealizedthroughcalcinatingtheanodenickelparticlesoutsidetheDCFC.MechanismsIntheMC-DCFCsystem,thesolidcarbonfuelcanbeoxidizeddirectlytoCO2(asgiveninEq. 1).Thereafter,itiscirculatedtothecathodecompartmentthroughthemoltencarbonateelectrolytetoachievemassbalance(asgivenbyEq. 2).Thereactionsaredetailedbelow[102,103].$${\text{Anode}}:{\text{C}}+{\text{2CO}}_{3}^{{2-}}={\text{3CO}}_{{\text{2}}}+{\text{4e}}^{-}$$ (1) $${\text{Cathode:}}\,{\text{O}}_{{\text{2}}}+{\text{2CO}}_{{\text{2}}}+{\text{4e}}^{-}={\text{2CO}}_{{\text{3}}}^{{{\text{2}}-}}$$ (2) ThetotalreactionisshowninEq. (3).$${\text{Overallreaction}}:{\text{C}}+{\text{O}}_{{\text{2}}}={\text{CO}}_{{\text{2}}}$$ (3) Theaboveequationsalsoindicatethat\({\text{P}}_{{\text{CO}}_{\text{2}}}\)couldinfluencetheopen-circuitvoltage(OCV)ofthecell,asshowninEq. (4)[41].$${\text{E=E}}^{{\text{o}}}+{\text{RT}}/{\text{4Fln[P}}_{{{\text{O}}_{{\text{2}}}}}{\text{][P}}_{{{\text{CO}}_{{\text{2}}}}}{\text{]}}_{{{\text{cathode}}}}^{{\text{2}}}/{\text{[P}}_{{{\text{CO}}_{{\text{2}}}}}{\text{]}}_{{{\text{anode}}}}^{{\text{3}}}$$ (4) ThepossibleoxidationreactionsofcarboninMC-DCFCandthegasproducedareshowninFig. 3,whichshowsthat:thedecompositionofcarbonatecanalsoproduceCO2;ithasaninfluenceontheDCFCperformance(Eq. 5)[104].Oneinvestigationshowedanoticeableincreaseinover-potentialatahighercurrentdensity,owingtothemasstransferprocessbeingprevented,butitwaseasyforthereleasedCO2gastomakecontactwiththecarbonandionsattheanodeagain,withalong-termdischargerecorded[105].Fig.3SchematicoftheMC-DCFCsystem:CO2andO2gainelectronstoproducecarbonateionatthecathode;carbonateionandcarbongenerateCOorCO2andelectronsattheanode.Atthesametime,carbonateionislikelytodecomposeintoO2−andCO2FullsizeimageGenerally,itrequiresahighoperatingtemperaturetoenhancetheanodereactionrate.EarlyexperimentalresultsshowthatthepredominantproductwithacarbonanodeisCOabove700 °CandthisisdependentonthereversaloftheBoudouardreaction(asgivenbyEq. 6).Expectedenergyfromreaction(Eq. 1)ishalved,becauseonlytwoequivalentchargesareobtainedfromonemoleofcarbonwithoutasignificantvoltagechangeat750 °C.$${\text{CO}}_{3}^{{2-}}={\text{CO}}_{{\text{2}}}+{\text{O}}^{{{\text{2}}-}}$$ (5) $${\text{C}}+{\text{CO}}_{{\text{2}}}={\text{2CO}}$$ (6) OtherreactionsbesidestheBoudouardreactionarepossible,suchaspartialoxidationofcarbon,asshowninEqs.(7)and(8)[106].$${\text{2C}}+{\text{CO}}_{3}^{{2-}}={\text{3CO}}+{\text{2e}}^{-}$$ (7) $${\text{C}}+{\text{CO}}_{3}^{{2-}}={\text{CO}}+{\text{CO}}_{{\text{2}}}+{\text{2e}}^{-}$$ (8) ThemainproductofthecarbonanodeisidentifiedasCO2throughoff-gasanalysis[107].TheelectrochemicalformationofCOisnotaninsurmountableprobleminDCFC,asthisreactionintheanodecompartmentoccursonlyintheprocessofcelloperation[74].TheOCVvaluecanbediminishedoreveneliminatedifpureCO2isblownintotheanodecompartmentunderthecellwhenoperatingabove700 °C,orwhentheCO2residueintheopen-circuitconditionisminimal(Table2). Cooperetal.[41,108]proposedthatthemechanismsofcarbonoxidationinMCFCarethesameasintheHallprocess,asgivenbyEqs.(9–14),whileMCFCalsoformsoxygenions.TheoxygenionsareformedbythereadydecompositionofthemoltencarbonateattheDCFCoperatingtemperature(asgivenbyEq. 5),whichtriggersthesubsequentoxidationreactionsofcarbon.$${\text{C}}_{{{\text{RS}}}}+{\text{O}}^{{2-}}={\text{C}}_{{{\text{RS}}}}{\text{O}}^{{{\text{2}}-}}\quad{\text{Fastadsorptiononcarbonreactivesites}}$$ (9) $${\text{C}}_{{{\text{RS}}}}{\text{O}}^{{{\text{2}}-}}={\text{C}}_{{{\text{RS}}}}{\text{O}}^{-}+{\text{e}}^{-}\quad{\text{Fastdischarge}}$$ (10) $${\text{C}}_{{{\text{RS}}}}{\text{O}}^{-}={\text{C}}_{{{\text{RS}}}}{\text{O}}+{\text{e}}^{-}\quad{\text{Fastdischarge}}$$ (11) $${\text{C}}_{{{\text{RS}}}}{\text{O}}+{\text{O}}^{{{\text{2}}-}}={\text{C}}_{{{\text{RS}}}}{\text{O}}_{{\text{2}}}^{{{\text{2}}-}}\quad{\text{Slowadsorption:Ratedeterminingstep}}$$ (12) $${\text{C}}_{{{\text{RS}}}}{\text{O}}_{{\text{2}}}^{{{\text{2}}-}}={\text{C}}_{{{\text{RS}}}}{\text{O}}_{{\text{2}}}^{-}+{\text{e}}^{-}\quad{\text{Fastdischarge}}$$ (13) $${\text{C}}_{{{\text{RS}}}}{\text{O}}_{{\text{2}}}^{-}={\text{CO}}_{{\text{2}}}{\text{(g)}}+{\text{e}}^{-}\quad{\text{Fastdischargeandoutgassing}}$$ (14) Theabovereactionsindicatethatoxidationofcarbonmonoxideiskeytothewholecarbonoxidationprocess,becausecarboniseasilyoxidizedtoCOwiththeone-electrontransfer.ThecombinationofcarbonandO2−isaffectedbythenumberandconcentrationofcarbonactivesites,dependingonthecarbonsurfacearea.Lietal.[96]useddifferentcarbonsourcesasthefuelandproposedthattheredoxreactionrateincarbonateslurryismainlydeterminedbythecrystallinityandsurfaceproperties,especiallythesurfaceareaandthequantityofthecarbonsurfacefunctionalgroup.TheseresultsalsoverifytherationalityofCherepy'selectrochemicalmechanismtoacertainextent.Recently,moreattentionhasbeenpaidtotailoringthecellstructuretoimprovetheperformanceofMC-DCFC.Leeetal.[109]proposedthattheadditionofGd2O3toaNianodeimprovedcellperformanceduetotheenlargedTPBsandthereducedcharge-transferresistance.TheyalsoconcludedthattheNi:Gd2O3 = 1:5anodewasanoptimalvaluebetweenthewettabilityandtheelectronicconductivity.Then,Leeetal.[78]alsoreportedthattheadditionoflanthanumstrontiumcobaltferrite(LSCF)andMIECtotheNianode,atamolarratioof1:1,showedabetterpowerdensityof111 mW cm−2at700 °CcomparedtothesingleNianode.Theexcellentpoweroutputisattributedtothedecreasedohmicandcharge-transferresistanceandtheexpansionofTPBs.Additionally,Bieetal.[110]designedanovelsyringe-typeanode,whichensuredextendedregionTPBsbypressingthecarbonpowderintothemoltenelectrolyte,andpreventingcarbonoxidation.CO3 2− + MIECItiswellknownthatceria-basedoxideisatypicaltransitionmetaloxidewithmixedelectronicandionicconductivity(MIEC).Itsdopedoxides,includingGd-dopedceria(GDC)andSm-dopedceria(SDC),havebeenappliedtoanintermediatetemperature(IT)SOFCrangingfrom400to700 °C[111].TheSDC-carbonatecompositeelectrolyteshowsexcellentconductivityof10–2to1.0Scm−1intherangeof400–700 °C,whichisbetterthanapureGDCorSDC(5 × 10–3–10–2 S cm−1),andsimilartothetraditionalsolidoxideelectrolyte—yttrium-stabilizedzirconia(YSZ)at1000 °C[112,113].Additionally,thiscompositeelectrolyteisnotsubjecttocorrosionissuesin thenormalMCFC.ThistypeofcompositeelectrolytehasalsonowbeenpopularizedinDCFCandhasshownacceptableperformance.ThecellperformancewasimprovedwhenusingthecompositeelectrolyteofSDCandcarbonatebecausemoltencarbonatewithmobilitycanexpandtheTPBattheanode.Therefore,reducedelectrodepolarizationresistancewasoftenachieved.Itwasalsofoundthattheredoxreactionofcarbonfuelwasenhancedwhenusingdopedceriamaterials.AdiagramoftheelectrochemicalprocessbetweentheelectrolyteandtheelectrodeispresentedinFig. 4.ItshowsthattwoelectrochemicalmechanismsmightberesponsibleforformingcarbonateionsandoxygenionsinthecathodechamberfilledwithO2andCO2(Eqs.2and15).Fig.4SchematicofDCFCwithacompositeelectrolyte:CO2andO2receiveelectronsandproducecarbonateion;onlyO2receiveselectronsandproducesO2−atthecathode.Then,theO2−andcarbonateionsaretransferredtotheanodethroughacompositeelectrolyte,andreactwithcarbontoproduceCO,CO2andelectronsFullsizeimageInthecompositeelectrolyteofSDC-carbonate,itisapparentthatthechargedspeciesarecarbonateionsandoxygenionsandthatcarbonateionsaretransferredinthemoltenelectrolyte,whileoxygenionsaretheconductingspecieswithintheSDC[114,115].Thecarbonparticlesintheanodecavity,partofwhichisimmersedinmoltencarbonate,combinewithcarbonateions,whileothersareincontactwiththeelectrolyteofSDCdirectlyandreactwithoxygenions,whichsimultaneouslyreleaseCOorCO2andgenerateelectrons(Eqs.1,7,16and17).COcanalsobeproducedfromEq. (6)throughtheBoudouardreaction,withfurtheroxidationbyoxygenions[116].Despitemanystudiesdoneonthemoltencarbonatesystemtoexploretheoxidationreactionsofcarbon,thereactionmechanismisstillnotfullyunderstood[117].$${\text{O}}_{{\text{2}}}+{\text{4e}}^{-}={\text{2O}}^{{{\text{2}}-}}$$ (15) $${\text{C}}+{\text{2O}}^{{{\text{2}}-}}={\text{CO}}_{{\text{2}}}+{\text{4e}}^{-}$$ (16) $${\text{C}}+{\text{O}}^{{{\text{2}}-}}={\text{CO}}+{\text{2e}}^{-}$$ (17) VarietiesofcarbonaceousfuelsusedinDCFCwiththedopedceria-carbonatecompositeelectrolytehavebeenreportedinliterature.Elleuchetal.[79]usedlow-costsolidcarbon-containingcoalcoke,petroleumcokeandalmondshellcarbonizationasfuelforDCFCwithanSDC-NiOanode,anSDC-(66 mol%Li2CO3-33 mol%Na2CO3)electrolyteandLixNi1-xO-SDCasthecathode.Theresultsshowedthatthecarbonized-almondshellwithmoreoxygen-containingfunctionalgroupshasgoodcellperformanceat700 °C,withapoweroutputof127 mW cm−2.Theresearchersfurtherexploredtheelectrochemicaloxidationofcarbonusinggraphiteinthesamecell[113].Theyfoundthatcellperformancewasimprovedwithamaximumpowerdensityof59 mW cm−2at700 °Cwhenadjustingtheanodeenvironment(N2atmosphere).InCO2atmosphere,thevaluereached37 mW cm−2[113].Recently,adual3DceramictextileelectrodewasintegratedintoaGDC-carbonatecompositeelectrolyte-supportedDCFC,andthus,theTPBregionwasexpanded[118].Bianetal.[81]developedauniqueelectrolyte-supportedDCFCconsistingofaGDC-(67 mol%Li2CO3-33 mol%Na2CO3)electrolyte,aNiO-GDCanodeandaSm0.5Sr0.5CoO3-GDCcathode.Itexhibitedunprecedentedcellperformanceat600 °C,withapoweroutputof392 mW cm−2whenusinggraphiticfuel,duetotheenhancedchargeandmasstransferontheelectrodebelow600 °C[81].Highfuelutilizationof87.3%wasalsoachieved,asthecarbonfuelcouldquicklyreachtheTPBsviatheflowingmoltencarbonateinthecelloperationprocess.CO3 2− + SOFCRecently,HDCFCwascombinedwithSOFCtechnologyandMCFCtechnologytoprovideanewwayforcarbonfueltoreachthereactionregion[21].Thismethodensuresthatthemoltencarbonateisincorporatedintotheanodecavity,whichsignificantlyexpandsthereactionregionfromatwo-dimensionaltoathree-dimensionalregion,andthisacceleratesthemasstransfertothesolidanode/electrolyte.Thecarbonateservesasamediumtopromotethecompleteoxidationofcarbon[23,119].Inthissystem,thesolidoxideelectrolyteseparatestheanodefromthecathodeandpreventsthediffusionofcarbonatetothecathodewithnoriskofcarbonatecorrosiononthecathode.AnotherfeatureisthatnoneedfortheCO2cycle.Thecathodeisexposedtoair,whichsimplifiesthecellstructure.ThefirstHDCFCwasdemonstratedbySRIInternational[120],andwasfurtherdevelopedbytheUniversityofStAndrews[21,121,122],ContainedEnergy[123]andTechnicalUniversityofDenmark[124,125].AnearlytubularHDCFCusingaPtcathodeandYSZelectrolytewasdesignedbytheUniversityofStAndrews,withtheanodenickelmeshplacedinamixtureofcarbonateandcarbon[126].However,itisdifficulttoobservethereactionattheanodeinthisconfiguration,astheactivezonesoftheelectrolyte/electrodeareuncertaininaclosed-cellabovethemeltingpointofthelithiumandpotassiumcarbonate[126,127].TheresearchersattheUniversityofStAndrewsalsodevelopedaplanarbuttoncellwithbettersealingforimprovedgaspurification[128].Theelectrochemicalreactionmechanismintheanodewasalsoinvestigatedindetail[21,122].Todate,thehighestpowerdensitywasobtainedbyJiangetal.[15]usingpyrolyzedmedium-densityfiberboardinHDCFC,whichreached878 mW cm−2at750 °C.ReactionmechanismHDCFCisbasedontwotypicalfuelcells—SOFCandMCFC—inwhich:thesolidoxideelectrolyte(whichincludesYSZ,GDCorSDC)separatestheelectrodechambers;themoltencarbonateelectrolytehasfluidityatahightemperatureandexpandstheoxidationreactionarea[21].Theoxygenionsreducedfromtheoxygenmoleculearetransmittedfromthecathodetotheanodecompartmentthroughthesolidoxideelectrolyte(asgivenbyEq. 15).Intheanodecompartment,carbonparticlesmaybecompletelyoxidizedtoCO2orpartiallyoxidizedtoCO(Eqs.16and17)[129,130].TheOCVvaluewouldbe1.02 V,ifEq. 16wastheonlyanodereaction,regardlessoftemperature.AnOCVofapproximately1.5 Vwasobservedbyacurrentstudy,whichishigherthanthetheoreticalvoltagewithworkingtemperaturesof550–700 °CinHDCFC[119].AhigherOCVvalueindicatesthatotherreactionsarealsounderwayapartfromthedirectelectrochemicaloxidationofcarbontoCO2.Figure 5showsthatsomereactionsandsomegasproductionoccurintheanodecompartmentofHDCFC,whichisfullofCO2andCOatthesametime.Intheanodechamberfilledwithnitrogen,thereactionprocessesofcarbon(bothelectrochemicalandchemical)arecomplicated.Intheanode,bothoxygenionsandcarbonateionsareactivespeciesofelectrochemicaloxidationintheslurryofcarbon/carbonate[21].Whenthenumberofoxygenionsissufficientlyhigh,theCO2couldbeconvertedtocarbonateions,whichwouldresultinaslowdeclineofCO2activityinthemoltencarbonate,asindicatedbyEq. (18).Withcontinuedconsumptionoftheoxygenions,thecarbonateionsoxidizecarbontoCO2orCO,asindicatedbyEqs.(7and8).CarbonateionsthenregeneratefromoxygenionsandCO2asindicatedbyEq. (18),whichmaintainstheelectricchargebalanceinthemoltencarbonatesolution.SomereportshaveclaimedthatthelowactivityofCO2couldbeduetoitbeingdissolvedinmoltencarbonatebyphysicalorchemicalmethods[131,132],whichmayincreasetheNernstpotential.Nevertheless,thepresenceofmoltencarbonate,whichfacilitatestheflowofcarbonparticlestotheanodechamberandexpandstheTPBs,isexpectedtoactasanelectrochemicalmediatorandacceleratetheoxidationreactionkineticsofthecarbonparticles[13,41].$${\text{O}}^{{{\text{2}}-}}{\text{+CO}}_{{\text{2}}}{\text{=CO}}_{{\text{3}}}^{{{\text{2}}-}}$$ (18) $${\text{CO+O}}^{{{\text{2}}-}}={\text{CO}}_{{\text{2}}}{\text{+2e}}^{-}$$ (19) $${\text{CO}}+{\text{CO}}_{{\text{3}}}^{{{\text{2}}-}}={\text{2CO}}_{{\text{2}}}+{\text{2e}}^{-}$$ (20) Fig.5SchematicdiagramoftheSOFC + MCFCsystem:O2gainselectronsandthenproducesO2−atthecathode;O2−thenpassesthroughasolidoxideelectrolyteandarrivesattheelectrolyte/anodeinterface,whereitreactswithcarbontoproduceCO,CO2andelectronsFullsizeimageInaddition,thenon-electrochemicalreactionoftheBoudouardreactionthatoccursat750 °Chasastronginfluenceontheentireanodereaction,whichconsumescarbonthroughachemicalreactionandcausesasharpdecreaseincurrentdensity[28].Butintermsoflong-termstability,theinfluenceofcurrentdensityisnotobvious[29].However,theCOproducedbythereverseBoudouardreactioncanalsogenerateelectricitythroughelectrochemicaloxidation,whichcontributestohigher-poweroutput[133].Deleebeecketal.[124]comparedtheeffectsofdifferentanodegasesoncellperformanceandfoundthatintroducingpureCO2couldreducethemasstransferlimitationbyfacilitatingtheBoudouardreactionorpreventingthecarbonatedecomposition.Inaddition,introducingN2leadstoahighOCV,duetothemovementofCO2orCO[134].Recently,Lietal.[135]alsofoundthatintroducingCO2intotheanodechambercouldimprovecellperformancethroughtheelectrochemicalreaction(Eqs.19and20)at700–800 °C.However,poorperformancebyfilingCO2wasobtainedat650 °C,asalowtemperatureisunfavorableforthereverseBoudouardreaction.Giventhispriorresearch,Leeetal.[136]designedthree-fuelcellsthatprovideddifferentcontactswiththeanodeandanalyzedtheoxidationofcarbonfuelbyobservingthecurrentdensityusingdifferentvoltages.ThevariousmeansofcontactmethodbetweenthecarbonandanodearepresentedinFig. 6a.CellI,cellIIandcellIIIindicate:directcontact,physicallyseparated,incontactwiththecarbonatemedium.Thecurrentdensityofthecellat800 °C,whenusingadifferentvoltageload,isshowninFig. 6b.ItshowsthatthevaluesofiIandiIIwerelowerthanthatofiIIIatagivenvoltage.Therefore,addingcarbonateincreasesthecurrentdensitysignificantly,provingthatthecarbonateionsdominatetheoxidationreaction(SeeFig. 6c.Fig.6Reproducedfromref.[136]TherelationshipbetweenthedifferentcontactmodesoftheanodeandthecellperformanceofDCFC:athreedifferentcontactmethodsforcarbonfuelandtheanode;bcomparisonofcurrentdensityusingdifferentvoltagelevelsat800 °C;andcrelativecontributionvalueofvariousreactionmechanismstothetotalcurrent.FullsizeimageRecently,Jiangetal.[137]designedanexperimenttoinvestigatethepossiblereactionactivesitesattheanodechamberinHDCFC.TheconfigurationoftheHDCFCdesignisshowninFig. 7a.Thecurrentcollectionwirecouldbemovedtoalloweasyadjustmentofthespacebetweenthecurrentcollectorandthelayerattheanode(L),tofurtherensurethatthereactionsoccurintheareacontainingthecarbonandcarbonate.Figure 7bandcshowtheACimpedancespectraat700 °CwhenusingananodecurrentcollectorofAuandPtanddifferentLs.Thisdemonstratesthattheohmicresistancewasdeterminedbythelocationofthecurrentcollectionwithunchangedpolarizationresistance.Theunchangedpolarizationresistancewiththecurrentcollectionpositionalsoindicatesapossibleextensionfroma2DanodeintheTPBstoa3Dareafilledwithcarbonandcarbonateforallinstancesofcarbonoxidation.Fig.7Reproducedfromref.[137]TheelectrochemicalreactionzoneinHDCFCwithaNiO-YSZanode,YSZelectrolyte,LSM-YSZcathodeand62 mol%Li2CO3-38 mol%K2CO3:aconfigurationoftheHDCFCdesignwithremovablecurrentcollectionwires;bACimpedancespectrumat700 °CwithAu/NiO-YSZ/YSZ/LSM-YSZ;cACimpedancespectrumat700 °CwithPd/YSZ/LSM-YSZ.FullsizeimageApartfromthetemperature,thecarbonoxidationprocessattheanodealsodependsontheelectrodeandelectrolyte.Jiangetal.[122]furtherexploredthereactionmechanismoftheanodebyexchangingthecarbonatecontentintheHDCFCsystemwithaconfigurationofNiO-YSZ/YSZ/LSM,whileusing62 mol%Li2CO3-38 mol%K2CO3intheanodechamber.Theyobservedreducedpolarizationresistanceofthecellwithacarbonatecontentof20 mol%or50 mol%.Adifferentresultwasfoundwhenmorecarbonatewasapplied,andhigherpolarizationresistancewasachievedwhenthecarbonateincreasedto80 mol%.Thisfindingdemonstratesthatcarbonparticlesarepreventedfromreachingtheelectrodebyahighconcentrationofmoltencarbonate,whichhasalimitedeffectonvariouscarbonoxidationreactions.Somecorrosionandsealingissuesaresignificantconcernswhenusinghighcarbonateconcentrations.Cantero-Tubillaetal.[72]proposedthattheliquidphasewasrelatedtothecarbonatecontent,andthereforetherateofmovementofcarbonfuelslowedinthepresenceofhighcarbonateconcentrations.Themeltcarbonatecouldresultinaconcomitantincreaseinpolarizationresistanceand,consequently,asignificantdeclineinelectrochemicaloutput.ChemicalcatalysisMcKeeetal.[133,134,135,136,137,138,139,140]usedadefiniteredoxcycleandpostulatedthatalkalimetalcarbonates(Li2CO3,Na2CO3,K2CO3,etc.)producecatalyticactivity,whichishelpfulintheprocessofgasificationofcarbonunderanoxygenorcarbondioxideatmosphere.Inaflowingoxygenatmosphere,carbon-induceddecompositionofmetalcarbonates(M2CO3)intometaloxides(M2O),asshownEq. (21)[138]:$${\text{M}}_{{\text{2}}}{\text{CO}}_{{\text{3}}}{\text{+C+O}}_{{\text{2}}}{\text{=M}}_{{\text{2}}}{\text{O+2CO}}_{{\text{2}}}$$ (21) Atahighertemperature,M2Oisfurtheroxidizedtoperoxideorhigheroxide(M2O1+n),andeventuallyreducedtoM2Obycarbon,whichcompletestheredoxcycle—seeEqs.(22,23)[139].$${\text{M}}_{{\text{2}}}{\text{O+}}\frac{n}{2}{\text{O}}_{{\text{2}}}{\text{=M}}_{{\text{2}}}{\text{O}}_{{{\text{1+n}}}}$$ (22) $${\text{M}}_{{\text{2}}}{\text{O}}_{{{\text{1+n}}}}{\text{+nC=M}}_{{\text{2}}}{\text{O+nCO}}$$ (23) Nevertheless,itisunlikelythatthereactionoftheoxide-peroxidecyclewilltakeplaceinaflowingcarbondioxideatmospherebecausetheconversionofM2CO3toM2Oisdifficult.Instead,M2CO3isreducedtotheelementalstate,whileCisoxidizedtoCO:$${\text{M}}_{{\text{2}}}{\text{CO}}_{{\text{3}}}{\text{+2C=2M+3CO}}$$ (24) Then,themetalelementgeneratesmetaloxideinthecarbondioxideatmosphere:$${\text{2M+CO}}_{{\text{2}}}{\text{=M}}_{{\text{2}}}{\text{O+CO}}$$ (25) Afterthat,carbonateisformedbythemetaloxideandcarbondioxide,whichcompletesacyclereaction[138]:$${\text{M}}_{{\text{2}}}{\text{O+CO}}_{{\text{2}}}{\text{=M}}_{{\text{2}}}{\text{CO}}_{{\text{3}}}$$ (26) Nagaseetal.[141]proposedthatsomemetalcarbonatesalsohadaninfluenceonthereverseBoudouardreactioninaninertatmosphere,whichactedasthecatalyticmediaintheprocessofelectrochemicaloxidationorgasificationofcarbon.Recently,Lietal.[22]studiedthereactionmechanismoftheHDCFCanodefilledwithN2.TheseresearchersfoundthatmoreCOwasproducedusingeutecticsalts(Li2CO3–K2CO3)asthecatalystmedia,thantheabsenceofcarbonate,whichthereforeimprovedcellperformance.Tworeactionsproducedthecarbondioxide(Eq. 27)andthecarbonmonoxide(Eq. 28),withbothconvertingM2CO3toM2O:$${\text{M}}_{{\text{2}}}{\text{CO}}_{{\text{3}}}{\text{+C+2O}}^{{{\text{2}}-}}{\text{=M}}_{{\text{2}}}{\text{O+2CO}}_{{\text{2}}}{\text{+4e}}^{-}$$ (27) $${\text{M}}_{{\text{2}}}{\text{CO}}_{{\text{3}}}{\text{+C+O}}^{{{\text{2}}-}}{\text{=M}}_{{\text{2}}}{\text{O+CO}}_{{\text{2}}}{\text{+CO+2e}}^{-}$$ (28) Lastly,moreCOandelectronsweregeneratedbyseriesofreactions(Eqs.29and30)thaninanoxygenatmosphere:$${\text{M}}_{{\text{2}}}{\text{O+nO}}^{{{\text{2}}-}}{\text{=M}}_{{\text{2}}}{\text{O}}_{{{\text{1+n}}}}{\text{+2ne}}^{-}$$ (29) $${\text{M}}_{{\text{2}}}{\text{O}}_{{{\text{1+n}}}}{\text{+nC=M}}_{{\text{2}}}{\text{O+nCO}}$$ (30) IssueswiththepresenceofcarbonateEventhoughDCFCisbeingdevelopedcontinuously,someissues,likematerialsandtechnology,mustbeaddressed.Mostmoltencarbonatesarecorrosiveandreactive,whichraiseswidespreadconcernaboutthethermalcorrosionandchemicalstabilityofcellmaterialsandthechemicalcompositionofsolidfuels.Besidestheashofsolidcarbonfuels,thewettabilityofcarbonatesalsoaffectscellperformance.Theseproblemsultimatelyleadtoasignificantreductioninconversionefficiencyandlong-termstability.CorrosionThehighlycorrosiveactionofmoltencarbonatehaspreventedprogressfrombeingmadewithMCFCtechnology.From1996to2006,thecelllifetimewasgreatlyincreasedfromjustafewmonthsto2 years[142].However,whenvariouscarbonatesareusedastheelectrolytecontactedbycellcomponents,itstillresultsinthermalcorrosionattacks(suchasoxidation,carburizationandfluxreactions)athighoperatingtemperatures[143].ThecorrosionissuegivesrisetoseverechallengesinimprovingthechemicalandphysicochemicalstabilityofelectrodematerialsforMCFC.Althoughsomenewpowergenerationdevicesareemerging,stabilityhasalwaysbeenanissuewhendevelopingnewtechnologies.Atpresent,nickelisoneofthemostwidelyusedelectrodematerialsbecauseofitslowpriceandgoodperformanceinconductivityandelectro-catalyticability.However,NiandNiOareeasilydissolvedintothemoltencarbonate,whichcausesaninternalshort-circuitinMCFCorashortlifespan[144].ItwasreportedthattheNi/NiOsolubilityincarbonatecouldbereducedbyaddingsomeoxides(e.g.,SrOorMgO[140,141,142,143,144,145,146,147,148])orcarbonates(e.g.,CaCO3,BaCO3,orSrCO3[146,149])toalkalicarbonate,duetothechangeinthepHvalueofthesolution.Dopingarare-earthmetal[150]orarare-earthmetaloxide(suchasLa2O3,Y2O3,andYb2O3)[146,147,148,149,150,151,152,153]isanotherpracticalapproachtoprotectthenickelornickeloxideelectrodeagainstdissolutioninmoltencarbonate.Forexample,aNi–Cecathodeshowedmoredurability(136 mW cm−2during2100 h)thanacommercialNicathodematerial(butthevoltagedecreasedfrom120to108 mW cm−2in1000 h)[150].Further,Liuetal.[154]observedthataddingtherare-earthmetalDytoamixtureofLi2CO3andK2CO3inamoleratioof62:38couldreducetheNiO/Nipassiveanodiccurrent,inhibitingtheoutwarddiffusionofNiat650 °C,andeventuallyincreasetheresistantabilitytocorrosion.IntermsofHDCFC,thesolidoxideelectrolyteseparatesthetwoelectrodesandpreventsthecathodefromcarbonatecorrosion.Nevertheless,thechemicalcompatibilitybetweentheelectrolyteandthecarbonateisessentialbecauseofthecontact-attack.Suskietal.[155]reportedonadouble-cellwithYSZandanelectrolyteof53%Li2CO3-47%Na2CO3,withtheOCVofO2 + Ar/YSZ/AuatTPBsbeingsimilartotheOCVvalueofthereferenceelectrodeover1000 hofoperation.ThelongoperationhoursindicatethatthekineticsofthechemicalreactionbetweenYSZandLi2CO3–Na2CO3isveryslow.However,anotherreportusedXRDanalysistodeterminethatYSZimmersedinLi2CO3–K2CO3at700 °Cfor10 dayswasconvertedtolithiumzirconate,butwithnochangeK2CO3–Na2CO3[126].Jiangetal.[15]didamoredetailedinvestigationofYSZcorrosion.First,theyconfirmedthattheYSZof5–10 μmdidnotchangefor13 hinanatmosphereof97–3%H2O.Then,severalcorrosionexperimentsweredoneontheYSZelectrolyteinmoltencarbonateof62 mol%Li2CO3-38 mol%K2CO3whenusingdifferentatmospheresat700 °Cfor10 h.Figure 8showsthecorrosionoftheYSZsurfacewhenusingdifferentatmospheres.Withtheairatmosphere,thegrainboundariesofYSZaredestroyedandnewparticlesappear,asshowninFig. 8b,whichmaybeduetotheformationofLi2ZrO3,K2ZrO3orLiKZrO3[151,152,153,154,155,156,157,158].SomewrinklesappearonthesurfaceofYSZandthegrainboundariesbecomeinconspicuousinareducingatmosphere,asshowninFig. 8c,butlesssignificantlythanintheairtest.Thereisnosignificantchangeaftertestingperformanceusing5%H2–95%Ar,asshowninFig. 8d.TheinsignificantchangeispossiblebecauseoftheformationofLi2ZrO3beingpreventedinareducingatmosphere[159].Fig.8Reproducedfromref.[15]SEMimagesoftheYSZsurfacewiththecorrosiontestinLi-Kcarbonateat700 °Cfor10 h:abeforethecorrosiontest;binair;cinAr;din5%H2/Ar.FullsizeimageTheresearchersusedthebasicitymodelofLux-Floodtoexplaintheexperimentalresult.Theformationofoxidesandsuperoxideswasmorelikelytooccurinanoxygenenvironment,whichwastheprimaryreasonforcorrosion[43].Itiscommontopurgeacarriergas(e.g.,N2orCO2)intheanodechamber.Theelectrolytematerial,YSZ,iseitherinthereducingenvironmentattheinterfaceoftheelectrolyte/anodeorintheoxidizingenvironmentattheinterfaceoftheelectrolyte/cathode.Therefore,itisnecessarytoinvestigatethestabilityofYSZinboththereducingatmosphereandtheoxidizingatmospheretosimulatebothoperatingconditions[159,160].AccordingtoXuetal.[161],YSZisagoodchoiceofelectrolyteforHDCFC,duetothereducingatmosphereoftheanodechamber.Thedopedceriumoxide-basedmaterialisatypicalsolidelectrolyteinDCFCthatshowsgoodstabilitybelow650 °C,duetothecompletemicrostructurebeingmaintainedat650 °Cand10%H2–90%N2for1000 h[162].Xuetal.[161]furtherexploredthestabilityofSDCin62 mol%Li2CO3-38 mol%K2CO3inair,andfoundthatYSZeasilyreactedwithK2CO3toformLi2ZrO3at700 °Cafter10 daysoftesting.And,thereisnonewphaseformationintheSDCsamplewhenusingthesameconditions.ThissuggeststhatSDCismoreresistanttocorrosionthanYSZ,whenusingair.AlthoughtherewasnoimpurityformationofSDCat700 °Cafter10 daysinair,cracksappearedatthegrainboundaries[163].Thissuggeststhatcrystalboundariesmightbethemostpreferredsiteforcorrosiondevelopment[163],asshowninFig. 9.Inaddition,theresistanceresultalsoshowedaninsignificantincreaseintheohmicresistanceoftheSDCelectrolyteat650 °Cduringthe70-htesting,whichmaybeduetotheslowcorrosionratealongthegrainboundary.Asmentioned,thecorrosionofmoltencarbonatecanbeamelioratedbydifferentmethods,butcannotbeavoided.Therefore,itisvitaltodevelopnascentcorrosion-resistantmaterials,tomaximizetheadvantagesofcarbonateforDCFCdevices.Fig.9Reproducedfromref.[161]CrosssectionoftheSDCforthecorrosiontestinLi-Kcarbonateat700 °Cinanairatmospherefor10 days:abeforethecorrosiontest;bafterthecorrosiontest.FullsizeimageAshSolidcarbonfuelscomefromawiderangeofsourcesandhaveauniqueconstituency.Themoltencarbonateislikelytochangechemicallyduetointeractionwithsomeashcomponents,includingheavymetalsandtheiroxides,sulfidesandchlorides,whichultimatelyleadtocellfailure[74].However,somemetalsinashhaveapositiveeffectoncellperformance.Forexample,Cao,MgOandFe2O3haveacatalyticeffectontheoxidationreactionofsolidcarbon,whichincreasesthecurrentdensity[24].AmixtureofFemOn,Li2O,K2OandCaOisthecatalystfortheBoudouardreaction[26]anditcanimprovethereactionactivityandelectrochemicalperformanceofthefuel[164].Therefore,studyingtheeffectofimpuritiesintheashoncellmaterialsiskeytoimprovingtheperformanceofDCFC.Ithasbeenreportedthatcoalwithalowashcontentshowsbettercellperformancethanhighash[29,160,161,162,163,164,165,166,167,168].Juetal.[169]comparedtheelectrochemicalperformanceofdifferentgradesofcoal,andfoundthatash-freecoal(lowashcontent)exhibitedthemostprolongedstability(300 minat50 mA cm−2and900 °C),whiletherawcoalwasunderoperationfor50 minbeforefailureduetoblockageoftheanodechannelbyashandthuspreventionofthereaction.Thehighashcontentinrawcoalisconsidereddetrimentaltotheshort-termstabilitywithaNi-YSZanode,astheashblockstheanodeandcausescontactbetweenthereactioninterfaceandthecarboninterfaceduringcelloperation[167].OnestudyreportedthatwhenusingAl2O3,SiO2andTiO2fromcoalash,itiseasytogenerateapassivatingmembraneontheelectrodeinterfaceduringoperationofthecell,whichleadstopassivationoftheelectrode[74].Inparticular,SiO2islikelytoreactwithcarbonateelectrolytes,togenerateCO2andM2SiO3(whereM = Li,Na,K)inMCFC,leadingtoadditionalelectrochemicalreactions[170].Tullochetal.[171]reportedthatcoalwithabout70 wt%SiO2ashshowedasignificantdecreaseincurrentdensityforMC-DCFC,asSiO2inhibitstheoxidationbehaviorofcarbon.Recently,differentpretreatmentmethodshavebeenproposedtoremoveunwantedimpuritiesandenhancecellperformance[167,168,169,170,171,172,173,174,175].Eometal.[172]reportedthatusingHCltopre-treatcoalcouldensuremaximumreductionofashcontentandthesensitivityofcellperformancetosurfacesiliconcontentmaybereducedwhenthetemperatureishigherthan733 °CbecauseLi2SiO3canbecompletelydecomposedat733 °C[176].Xieetal.[174]modifiedbituminouscoalwithaceticacid,andeffectivelyremovedashofabout84 wt%Siand64 wt%Al,tooptimizecellperformance.Ithasbeenreportedthatsomeimpuritiesinashmaypromoteanelectrodereaction,e.g.,CaO,MgOandFe2O3couldimprovethecurrentdensityslightlybyactingasacatalystinMC-DCFC[24,177].Caietal.[39]employedorchidleafcharinSO-DCFCwithyttrium-stabilizedzirconiaelectrolyteandanAg-GDCelectrode.TheresearchersconcludedthatthenaturalCainbiocharderivedfromorchidtreeleavesexertedacatalyticeffectonthereverseBoudouardreactionandenhancedtheperformanceofDCFC.Then,theyloaded5%Caonwheatstrawcharinthesamecellconfigurationandrecordedahigher-powerperformance(258 mW cm−2)comparedtothatofunloadingchar(197 mW cm−2)at700 °C[178].Haoetal.[36]furtherconfirmedthepositiveeffectofcalciteandmagnesiumcalciteinmagazinewastepaper,whichindicatedthatmoreamorphouscarbonexhibitedahigherdegreeofcarbonoxidationalsocatalyzedthegasificationreactionofcarbonfuelanddeliveredahigher-powerdensity.Recently,aDCFCsupportedbyanSDC-(67%Li-33%Na)2CO3compositemoltencarbonateshowedexcellentcellperformance(378 mW cm−2)atanoperatingtemperatureof750 °C.TheenhancedcellperformancewasbecausetheKClinrawreedashincreasesthedegreeofstructuraldisorderofbiocharduringthepyrolysisprocess,whichleadstothehighoxidationactivityofreedchar[179].WettingCompletewettingofthecarbonparticlesineutecticcarbonateiscriticalforthechargetransferattheTPBszone[180,181],asthisisadominantfactorinensuringuninterruptedround-the-clockpowergenerationbytheDCFC.Duringtheoperatingprocess,theeutecticcarbonateiscompletelydiffusedandpenetratesthecarbonpores.Therefore,thepotentialofastablecellcanbereached[49].Whenmeasuringthecontactangleofagraphiterodin62 mol%Li2CO3-38 mol%K2CO3at520–560 °C,Chenetal.[182]foundthatwettingofcarbonincarbonateisdrivenbycapillaryforce,aswellasbeinglargelydeterminedbyCObubblesproducedfromthereverseBoudouardreaction.TheOCVincreasesfrom0.5to0.81 Vduringtheprocessofwetting,whichcontributestotheadsorptionofCOonthesurface.Therefore,nomatterwhatcarbonateisemployedinDCFC,aslongasthesolidcarboniscompletelysoakedinthemoltencarbonatetoformtheinterfacewherethecarbonoxidationreactionoccurs,theelectronscanbecontinuouslygeneratedandtransferred.Thewettabilityofsolidcarbonfuelinamoltencarbonateisenhancedbypre-treatmenttoincreasethesurfaceareaandtheporevolumeofthecarbonparticles[183].Theeffectofbaseoracidpre-treatmentontheelectrochemicalactivityofcarboninlithiumandpotassiumcarbonatehasalsobeenexamined[183],withHF,HNO3andNaOHarethecommonacidandbasematerialsused.Ofallthesamples,activatedcarbonpre-treatedwithHFexhibitedthehighestelectro-oxidationactivity,withanincreasedcurrentofapproximately50 mA cm−2.TheenhancedcurrentisbecauseHFpre-treatmentincreasestheporosityandsurfaceareaofthecarbonparticles,formingadoubleelectricallayerthatfacilitateselectrontransferofcarbonduringanodization.Ithasalsobeenshownthatcarbonparticlewettabilityreliesoncarbonatecomposition.Watanabeetal.[184]indicatedthatthesurfacetensionofsolidcarboncouldbereducedbyloweringtheamountofsodiumcarbonateandthusimprovingitswettability.Thetestresultsshowedthatcarbonparticleshadabetterwettingeffectinaternarycarbonateof12.2 mol%Li2CO3-25 mol%Na2CO3-62.8 mol%K2CO3comparedto12.2 mol%Li2CO3-45 mol%Na2CO3-42.8 mol%K2CO3,andthatastableOCVof0.63 Vcouldbesustainedfor45 min.IntermsofDCFCwithmoltencarbonate,thedegreeofstirringisalsoanimportantvariablethataffectscarbonparticlewetting.Lietal.[96]observedthatmasstransferhasbeensignificantlyimprovedat400 rpm,andthatcurrentdensitycanbefurtherincreasedinthewholeelectrodepotentialrangewhenthestirringrateisincreasedupto600 rpm.ImprovedcurrentdensitywhenincreasingthestirringratealignswiththeearlierreportofVutetakisetal.[74].However,theperformanceofDCFCwillbegreatlyreducedifthestirringrateexceedsaspecificvalue,becausethefuelsplashphenomenonleadstoafuelshortage[4].Whetherthestirringimprovescellperformanceornotdependsonotherfactors,suchascelloperatingtemperatureandelectrolyteviscosity[185].Carbonatehasgoodionicconductivitybutpoorelectronicconductivityatahightemperature.Althoughcarbonparticleswithdifferentsizesaredispersedinmoltencarbonate,theelectrochemicaloxidationofcarbonoccursonlyinTPBs,thusthepercolationlimitofcarbonparticlesmustbeconsidered,toensureefficientandcontinuouspowergeneration[186].Usinghighlyconductivecarbonfuelssuchasgraphitecouldimproveelectronicconductivity,butthechemicalactivityofgraphiteisverylow.Atpresent,moltenmetalanodescansolvethisproblemandensuregoodconductivity[187].However,thecorrosionissueremainsunresolved.OutlookWiththeincreaseinenvironmentalconcernandthehighenergydemand,DCFCmayprovideacleanelectrochemicaldeviceforgeneratingelectricityfromsolidcarbon.TheintroductionofcarbonateintheDCFCsystemisconducivetoimprovingcellperformanceofopen-circuitvoltageandoutputpower.Thecarbonateacceleratesiontransferasamediumorisacatalystforcarbonoxidationandgasificationreaction.Atpresent,researchonbasictheoryisstillanessentialaspectofthedevelopmentofDCFC.AlthoughvariousDCFCsystemsthatusecarbonatearebeingdevelopedrapidly,thespecificreactionmechanismwithcarbonateinvolvedinthewhole-cellsystemstilllackssufficientproofofexperimentsduetothecomplexityofreactionsinsidethecell.Therefore,newexperimentalconfigurationsshouldbedesigned.Alternatively,acombinationofatheoreticalmodelandexperimentaltestsshouldbeconsidered,whichwouldbebeneficialtocellperformanceifdeterminedwhatsubstancesaffecttheelectrodereactionprocess.Theissueofmaterialcorrosioninmoltencarbonatehasnotbeensolvedsatisfactorily.DespiteaplethoraofliteraturesthathavebeenpublishedtosolvetheproblemofcorrosionofcarbonateinMC-DCFC,thereisstillnodetailedresearchonthecorrosionofcarbonatetothesolid-stateelectrolyteforemergingHDCFCs.Itisunknownwhetheraddingsomecarbonates,oxidesorrare-earthelementshasapositiveornegativeeffectoncellperformance.IthasbeenconfirmedthattheadditionofcarbonatetotheanodefavorsexpandingTPBs,becausethefluidityofmoltencarbonatecouldpromotethetransferofcarbonfueltotheanode,resultinginadramaticimprovementofelectrochemicalreactions.However,carbonateattacksthesolidelectrolyte.AlthoughSDChasbettercorrosionresistancethanYSZ,thecorrosionissuecannotbeavoided.Providedthatcorrosionoccursduringtheentirecelloperation,thecellwilldegradequicklyandcannotgeneratepoweroverthelongterm.Hence,moreattentionneedstobefocusedonthecarbonatecorrosiontoothercellcomponents(includingsolid-stateelectrolytes),insteadofonlycommonelectrodematerials.ItiswellknownthatthevarietyofsolidcarbonaceousfuelsisoneofthemostsignificantadvantagesofDCFC.Nonetheless,thecarbonatecomponentinDCFCeasilyreactswiththeinorganicsaltsoffuelsash—especiallycoalandbiomassfuelswithahighashcontent—whichshowsvariouseffectsoncellperformance.Forexample,alargeamountofFe,MgandCapromotesgasificationofcarbon,whileSiandAlhaveanegativeeffectonthecellperformanceofDCFCwithcarbonate.Itisdifficulttoidentifytheeffectofeachinorganicsaltoncellperformancebecausethereisoftenmorethanonesaltinthefuel.Removingashfromnon-purecarbonfuelssuchasbiomassshouldalsobeconsideredseriously.Pre-treatmentshouldbeattemptedasanessentialtreatmentmethodappliedtoDCFC(includingheattreatment,acidorbasewashingandairplasma,etc.).Otherissuesworthmentioningincludetheeffectofpre-treatmentonthepropertiesofthefuelitselfandthereactivityofthepretreatedfuelwithcarbonatestoeventuallyexplorethefeasibilityofusingdifferentrenewablecarbon-basedmaterialsinthecell.Whilemanycelldesignshavebeendevelopedtoprovidebettercontinuouspowergeneration,thefluidizedbedcellcanprovideamoreconvenientfeedingmode.Thus,designingdifferentcellconfigurationsisstillkeytothecommercializationofDCFC. ReferencesGrove,W.R.:XXIVOnvoltaicseriesandthecombinationofgasesbyplatinum.Phil.Mag.14(86–87),127–130(1839).https://doi.org/10.1080/14786443908649684Article  GoogleScholar  Behling,N.,Managi,S.,Williams,M.:Updatedlookattheapplicationofsolidparticlesinfuelcelltechnology.2019SMEAnnualConferenceandExpoandCMA121stNationalWesternMiningConference(2019)Williams,M.C.,Horita,T.,Yamaji,K.,Yokokawa,H.:Anapplicationofsolidparticlesinfuelcelltechnology.KONAPowderPart.J.25,153–161(2007).https://doi.org/10.14356/kona.2007014CAS  Article  GoogleScholar  Ahn,S.Y.,Eom,S.Y.,Rhie,Y.H.,Sung,Y.M.,Moon,C.E.,Choi,G.M.,Kim,D.J.:Utilizationofwoodbiomasscharinadirectcarbonfuelcell(DCFC)system.Appl.Energ.105,207–216(2013).https://doi.org/10.1016/j.apenergy.2013.01.023Article  GoogleScholar  Edison,T.A.:Processofandapparatusforgeneratingelectricity.USPatentNo460,122(1891)Jacques,W.W.:Methodofconvertingpotentialenergyofcarbonintoelectricalenergy.USPatentNo555511A(1896)Srinivasan,S.:Fuelcellsforextraterrestrialandterrestrialapplications.J.Electrochem.Soc.136(2),41C(1989).https://doi.org/10.1149/1.2096647CAS  Article  GoogleScholar  Meibuhr,S.:Reviewofunitedstatesfuel-cellpatentsissuedfrom1860to1947.Electrochim.Acta.11(9),1301–1308(1966).https://doi.org/10.1016/0013-4686(66)87029-9CAS  Article  GoogleScholar  Haber,F.,Bruner,L.:DasKohlenelement,eineKnallgaskette.ZeitschriftfürElektrochemieundangewandtephysikalischeChemie10(37),697–713(1904).https://doi.org/10.1002/bbpc.19040103702Article  GoogleScholar  Weaver,R.D.,Leach,S.C.,Bayce,A.E.,Nanis,L.:Directelectrochemicalgenerationofelectricityfromcoal.SRIInternationalCorp.(1979)Weaver,R.D.,Tietz,L.,Cubicciotti,D.:Directuseofcoalinafuelcell:Feasibilityinvestigation.SRIInternationalCorp.(1975)Gür,T.M.:Utilizationmodesforsolidcarbonconversioninfuelcells.ECSTrans.25(2),1099(2009).https://doi.org/10.1149/1.3205637Article  GoogleScholar  Gür,T.M.:Mechanisticmodesforsolidcarbonconversioninhightemperaturefuelcells.J.Electrochem.Soc.157(5),B751(2010).https://doi.org/10.1149/1.3357050CAS  Article  GoogleScholar  Nürnberger,S.,Bußar,R.,Desclaux,P.,Franke,B.,Rzepka,M.,Stimming,U.:DirectcarbonconversioninaSOFC-systemwithanon-porousanode.EnergyEnviron.Sci.3(1),150–153(2010).https://doi.org/10.1039/b916995dCAS  Article  GoogleScholar  Jiang,C.,Ma,J.,Bonaccorso,A.D.,Irvine,J.T.S.:Demonstrationofhighpower,directconversionofwaste-derivedcarboninahybriddirectcarbonfuelcell.EnergyEnviron.Sci.5(5),6973–6980(2012).https://doi.org/10.1039/c2ee03510cCAS  Article  GoogleScholar  Hackett,G.A.,Zondlo,J.W.,Svensson,R.:Evaluationofcarbonmaterialsforuseinadirectcarbonfuelcell.J.PowerSources168(1),111–118(2007).https://doi.org/10.1016/j.jpowsour.2007.02.021CAS  Article  GoogleScholar  Dicks,A.L.:Theroleofcarboninfuelcells.J.PowerSources156(2),128–141(2006).https://doi.org/10.1016/j.jpowsour.2006.02.054CAS  Article  GoogleScholar  Lan,R.,Tao,S.:Asimplehigh-performancematrix-freebiomassmoltencarbonatefuelcellwithoutCO2recirculation.Sci.Advs.2(8),e1600772(2016).https://doi.org/10.1126/sciadv.1600772CAS  Article  GoogleScholar  Dudek,M.,Tomczyk,P.:Compositefuelfordirectcarbonfuelcell.Catal.Today176(1),388–392(2011).https://doi.org/10.1016/j.cattod.2010.11.029CAS  Article  GoogleScholar  Liu,C.,Pu,J.,Chen,X.,Ma,Z.,Ding,X.,Zhou,J.,Wang,S.:Influenceofanode’smicrostructureonelectrochemicalperformanceofsolidoxidedirectcarbonfuelcells.Inter.J.HydrogenEnergy45(20),11784–11790(2020).https://doi.org/10.1016/j.ijhydene.2020.02.119CAS  Article  GoogleScholar  Nabae,Y.,Pointon,K.D.,Irvine,J.T.S.:ElectrochemicaloxidationofsolidcarboninhybridDCFCwithsolidoxideandmoltencarbonatebinaryelectrolyte.EnergyEnviron.Sci.1(1),148–155(2008).https://doi.org/10.1039/b804785eCAS  Article  GoogleScholar  Li,S.,Jiang,C.,Liu,J.,Tao,H.,Meng,X.,Connor,P.,Hui,J.,Wang,S.,Ma,J.,Irvine,J.T.S.:Mechanismofenhancedperformanceonahybriddirectcarbonfuelcellusingsawdustbiofuels.J.PowerSources383(15),10–16(2018).https://doi.org/10.1016/j.jpowsour.2018.02.040CAS  Article  GoogleScholar  Jiang,C.,Cui,C.,Ma,J.,Irvine,J.T.S.:InsightintographiteoxidationinaNiO-basedhybriddirectcarbonfuelcell.Inter.J.HydrogenEnergy45(17),10559–10568(2020).https://doi.org/10.1016/j.ijhydene.2019.08.208CAS  Article  GoogleScholar  Li,X.,Zhu,Z.,DeMarco,R.,Bradley,J.,Dicks,A.:Evaluationofrawcoalsasfuelsfordirectcarbonfuelcells.J.PowerSources195(13),4051–4058(2010).https://doi.org/10.1016/j.jpowsour.2010.01.048CAS  Article  GoogleScholar  Lee,C.-G.,Kim,W.-K.:Oxidationofash-freecoalinadirectcarbonfuelcell.Inter.J.HydrogenEnergy40(15),5475–5481(2015).https://doi.org/10.1016/j.ijhydene.2015.01.068CAS  Article  GoogleScholar  Tang,Y.,Liu,J.:EffectofanodeandBoudouardreactioncatalystsontheperformanceofdirectcarbonsolidoxidefuelcells.Inter.J.HydrogenEnergy35(20),11188–11193(2010).https://doi.org/10.1016/j.ijhydene.2010.07.068CAS  Article  GoogleScholar  Jewulski,J.,Skrzypkiewicz,M.,Struzik,M.,Lubarska-Radziejewska,I.:Ligniteasafuelfordirectcarbonfuelcellsystem.Inter.J.HydrogenEnergy39(36),21778–21785(2014).https://doi.org/10.1016/j.ijhydene.2014.05.039CAS  Article  GoogleScholar  Fuente-Cuesta,A.,Jiang,C.,Arenillas,A.,Irvine,J.T.S.:Roleofcoalcharacteristicsintheelectrochemicalbehaviourofhybriddirectcarbonfuelcells.EnergyEnviron.Sci.9(9),2868–2880(2016).https://doi.org/10.1039/c6ee01461eCAS  Article  GoogleScholar  Jiang,C.,Ma,J.,Arenillas,A.,Bonaccorso,A.D.,Irvine,J.T.:Comparativestudyofdurabilityofhybriddirectcarbonfuelcellswithanthracitecoalandbituminouscoal.Inter.J.HydrogenEnergy41(41),18797–18806(2016).https://doi.org/10.1016/j.ijhydene.2016.04.047CAS  Article  GoogleScholar  König,A.,Ulonska,K.,Mitsos,A.,Viell,J.R.:Optimalapplicationsandcombinationsofrenewablefuelproductionfrombiomassandelectricity.EnergyFuel33(2),1659–1672(2019).https://doi.org/10.1021/acs.energyfuels.8b03790CAS  Article  GoogleScholar  Li,M.,Xiao,H.,Zhang,T.,Li,Q.,Zhao,Y.:Activatedcarbonfiberderivedfromsisalwithlargespecificsurfaceareaforhigh-performancesupercapacitors.ACSSustain.Chem.Eng.7(5),4716–4723(2019).https://doi.org/10.1021/acssuschemeng.8b04607CAS  Article  GoogleScholar  Rybarczyk,M.K.,Li,Y.,Qiao,M.,Hu,Y.-S.,Titirici,M.-M.,Lieder,M.:HardcarbonderivedfromricehuskaslowcostnegativeelectrodesinNa-ionbatteries.J.EnergyChem.29,17–22(2019).https://doi.org/10.1016/j.jechem.2018.01.025Article  GoogleScholar  Tiwari,J.N.,Dang,N.K.,Sultan,S.,Thangavel,P.,Jeong,H.Y.,Kim,K.S.:Multi-heteroatom-dopedcarbonfromwaste-yeastbiomassforsustainedwatersplitting.Nat.Sustain.3(7),556–563(2020).https://doi.org/10.1038/s41893-020-0509-6Article  GoogleScholar  Xu,C.,Chen,J.,Li,S.,Gu,Q.,Wang,D.,Jiang,C.,Liu,Y.:N-dopedhoneycomb-likeporouscarbonderivedfrombiomassasanefficientcarbocatalystforH2Sselectiveoxidation.J.HazardMater.403(5),123806(2021).https://doi.org/10.1016/j.jhazmat.2020.123806CAS  Article  GoogleScholar  Yu,J.,Zhao,Y.,Li,Y.:Utilizationofcorncobbiocharinadirectcarbonfuelcell.J.PowerSources270(15),312–317(2014).https://doi.org/10.1016/j.jpowsour.2014.07.125CAS  Article  GoogleScholar  Hao,W.,Mi,Y.:Evaluationofwastepaperasasourceofcarbonfuelforhybriddirectcarbonfuelcells.Energy107(15),122–130(2016).https://doi.org/10.1016/j.energy.2016.04.012CAS  Article  GoogleScholar  Wang,C.,Lü,Z.,Li,J.,Cao,Z.,Wei,B.,Li,H.,Shang,M.,Su,C.:Efficientuseofwastecartonforpowergeneration,tarandfertilizerthroughdirectcarbonsolidoxidefuelcell.Renew.Energy158,410–420(2020).https://doi.org/10.1016/j.renene.2020.05.082CAS  Article  GoogleScholar  Elleuch,A.,Boussetta,A.,Yu,J.,Halouani,K.,Li,Y.:Experimentalinvestigationofdirectcarbonfuelcellfueledbyalmondshellbiochar:PartI.Physico-chemicalcharacterizationofthebiocharfuelandcellperformanceexamination.Inter.J.HydrogenEnergy38(36),16590–16604(2013).https://doi.org/10.1016/j.ijhydene.2013.08.090CAS  Article  GoogleScholar  Cai,W.,Zhou,Q.,Xie,Y.,Liu,J.,Long,G.,Cheng,S.,Liu,M.:Adirectcarbonsolidoxidefuelcelloperatedonaplantderivedbiofuelwithnaturalcatalyst.Appl.Energy179(2),1232–1241(2016).https://doi.org/10.1016/j.apenergy.2016.07.068CAS  Article  GoogleScholar  Ali,A.,Raza,R.,Shakir,M.I.,Iftikhar,A.,Alvi,F.,Ullah,M.K.,Hamid,A.,Kim,J.-S.:Promisingelectrochemicalstudyoftitanatebasedanodesindirectcarbonfuelcellusingwalnutandalmondshellsbiocharfuel.J.PowerSources.434,12(2019).https://doi.org/10.1016/j.jpowsour.2019.05.085CAS  Article  GoogleScholar  Cherepy,N.J.,Krueger,R.,Fiet,K.J.,Jankowski,A.F.,Cooper,J.F.:Directconversionofcarbonfuelsinamoltencarbonatefuelcell.J.Electrochem.Soc.152(1),A80–A87(2005).https://doi.org/10.1149/1.1836129CAS  Article  GoogleScholar  Cisneros,S.,Sánchez,C.:KineticcharacterizationandmoltenKOHfuelcellsimulationfordissolvedcoaloxidationonnickelanodes.J.Electrochem.Soc.161(14),F1330–F1339(2014).https://doi.org/10.1149/2.1181412jesCAS  Article  GoogleScholar  Bie,K.,Zhou,H.,Fu,P.,Liu,Y.,Yue,F.:Investigationofthecathodepolarizationandcarbondepositioninamoltencarbonatedirectcarbonfuelcell.J.Appl.Electrochem.49(6),585–597(2019).https://doi.org/10.1007/s10800-019-01307-0CAS  Article  GoogleScholar  Howard,H.:Directgenerationofelectricityfromcoalandgas(fuelcells).Chem.CoalUtil.2,1568–1585(1945)CAS  GoogleScholar  Liebhafsky,H.A.,Cairns,E.J.:Fuelcellsandfuelbatteries.Guidetotheirresearchanddevelopment(1968)Cao,D.,Sun,Y.,Wang,G.:Directcarbonfuelcell:Fundamentalsandrecentdevelopments.J.PowerSources167(2),250–257(2007).https://doi.org/10.1016/j.jpowsour.2007.02.034CAS  Article  GoogleScholar  Cao,T.,Huang,K.,Shi,Y.,Cai,N.:Recentadvancesinhigh-temperaturecarbon–airfuelcells.EnergyEnviron.Sci.10(2),460–490(2017).https://doi.org/10.1039/c6ee03462dCAS  Article  GoogleScholar  Giddey,S.,Badwal,S.P.S.,Kulkarni,A.,Munnings,C.:Acomprehensivereviewofdirectcarbonfuelcelltechnology.Prog.EnergyCombust.38(3),360–399(2012).https://doi.org/10.1016/j.pecs.2012.01.003CAS  Article  GoogleScholar  Cooper,J.F.,Selman,R.:Electrochemicaloxidationofcarbonforelectricpowergeneration:areview.J.Electrochem.Soc.19(14),15–25(2009).https://doi.org/10.1149/1.3220176CAS  Article  GoogleScholar  Gür,T.M.:Criticalreviewofcarbonconversionin“carbonfuelcells.”Chem.Rev.113(8),6179–6206(2013).https://doi.org/10.1021/cr400072bCAS  Article  GoogleScholar  Rady,A.C.,Giddey,S.,Badwal,S.P.S.,Ladewig,B.P.,Bhattacharya,S.:Reviewoffuelsfordirectcarbonfuelcells.EnergyFuel26(3),1471–1488(2012).https://doi.org/10.1021/ef201694yCAS  Article  GoogleScholar  Zhou,W.,Jiao,Y.,Li,S.D.,Shao,Z.:Anodesforcarbon-fueledsolidoxidefuelcells.ChemElectroChem3(2),193–203(2016).https://doi.org/10.1002/celc.201500420CAS  Article  GoogleScholar  Jiang,C.,Ma,J.,Corre,G.,Jain,S.L.,Irvine,J.T.S.:Challengesindevelopingdirectcarbonfuelcells.Chem.Soc.Rev.46(10),2889–2912(2017).https://doi.org/10.1039/c6cs00784hCAS  Article  GoogleScholar  Glenn,M.J.,Allen,J.A.,Donne,S.W.:Carbonelectro-catalysisinthedirectcarbonfuelcellutilisingalkalimetalmoltencarbonates:amechanisticreview.J.PowerSources453,227662(2020).https://doi.org/10.1016/j.jpowsour.2019.227662CAS  Article  GoogleScholar  Tanimoto,K.,Yanagida,M.,Kojima,T.,Tamiya,Y.,Matsumoto,H.,Miyazaki,Y.:Long-termoperationofsmall-sizedsinglemoltencarbonatefuelcells.J.PowerSources72(1),77–82(1998).https://doi.org/10.1016/S0378-7753(97)02673-6CAS  Article  GoogleScholar  Morita,H.,Kawase,M.,Mugikura,Y.,Asano,K.:Degradationmechanismofmoltencarbonatefuelcellbasedonlong-termperformance:long-termoperationbyusingbench-scalecellandpost-testanalysisofthecell.J.PowerSources195(20),6988–6996(2010).https://doi.org/10.1016/j.jpowsour.2010.04.084CAS  Article  GoogleScholar  Glugla,P.,DeCarlo,V.:Thespecificconductanceofmoltencarbonatefuelcelltiles.J.Electrochem.Soc.129(8),1745(1982).https://doi.org/10.1149/1.2124263CAS  Article  GoogleScholar  McKee,D.W.,Spiro,C.L.,Kosky,P.G.,Lamby,E.J.:Catalysisofcoalchargasificationbyalkalimetalsalts.Fuel62(2),217–220(1983).https://doi.org/10.1016/0016-2361(83)90202-8CAS  Article  GoogleScholar  McKee,D.W.,Spiro,C.L.,Kosky,P.G.,Lamby,E.J.:Eutecticsaltcatalystsforgraphiteandcoalchargasification.Fuel64(6),805–809(1985).https://doi.org/10.1016/0016-2361(85)90014-6CAS  Article  GoogleScholar  McKee,D.:Rareearthoxidesascarbonoxidationcatalysts.Carbon23(6),707–713(1985).https://doi.org/10.1016/0008-6223(85)90232-5CAS  Article  GoogleScholar  Yu,X.,Shi,Y.,Wang,H.,Cai,N.,Li,C.,Ghoniem,A.F.:Usingpotassiumcatalyticgasificationtoimprovetheperformanceofsolidoxidedirectcarbonfuelcells:experimentalcharacterizationandelementaryreactionmodeling.J.PowerSources252(2),130–137(2014).https://doi.org/10.1016/j.jpowsour.2013.12.021CAS  Article  GoogleScholar  Janz,G.J.,Lorena,M.R.:Solid-liquidphaseequilibriaformixturesoflithium,sodium,andpotassiumcarbonates.J.Chem.Eng.Data6(3),321–323(1961).https://doi.org/10.1021/je00103a001CAS  Article  GoogleScholar  Weaver,R.,Leach,S.,Nanis,L.:Electrolytemanagementforthecoalairfuelcell.IECECConference(1981)Kouchachvili,L.,Ikura,M.:Performanceofdirectcarbonfuelcell.Inter.J.HydrogenEnergy36(16),10263–10268(2011).https://doi.org/10.1016/j.ijhydene.2010.10.036CAS  Article  GoogleScholar  Kojima,T.,Yanagida,M.,Tanimoto,K.,Tamiya,Y.,Matsumoto,H.,MiyazakiI,Y.:Thesurfacetensionandthedensityofmoltenbinaryalkalicarbonatesystems.Electrochemistry67(6),593–602(1999).https://doi.org/10.5796/electrochemistry.67.593CAS  Article  GoogleScholar  Posypaiko,V.,Alekseeva,E.,Vasina,N.:Diagrammyplavkostisolevykhsistem.Troynyyesistemy[Chartsofsaltsystems'fusion.Triplesystems].Moscow:Chemistry(1977)Licht,S.:StabilizationofSTEPelectrolysesinlithium-freemoltencarbonates.arXivpreprintarXiv:1209.3512.(2012)Ang,P.,Sammells,A.:Influenceofelectrolytecompositiononelectrodekineticsinthemoltencarbonatefuelcell.J.Electrochem.Soc.127(6),1287(1980).https://doi.org/10.1149/198110.0341PVCAS  Article  GoogleScholar  Belhomme,C.,Devynck,J.,Cassir,M.:NewinsightinthecyclicvoltammetricbehaviourofnickelinmoltenLi2CO3–Na2CO3at650°C.Electroanal.Chem.545(27),7–17(2003).https://doi.org/10.1016/S0022-0728(03)00060-3CAS  Article  GoogleScholar  Maru,H.C.,Dullea,J.,Ong,E.,Pigeaud,A.,Sampath,V.,Selman,J.R.:Fuelcellresearchonsecond-generationmoltencarbonatesystem.InstituteofGasTechnology,Chicago(1976) GoogleScholar  Morita,H.,Komoda,M.,Mugikura,Y.,Izaki,Y.,Watanabe,T.,Masuda,Y.,Matsuyama,T.:PerformanceanalysisofmoltencarbonatefuelcellusingaLi/Naelectrolyte.J.PowerSources112(2),509–518(2002).https://doi.org/10.1016/S0378-7753(02)00468-8CAS  Article  GoogleScholar  Cantero-Tubilla,B.,Xu,C.,Zondlo,J.W.,Sabolsky,K.,Sabolsky,E.M.:Investigationofanodeconfigurationsandfuelmixturesontheperformanceofdirectcarbonfuelcells(DCFCs).J.PowerSources238(2),227–235(2013).https://doi.org/10.1016/j.jpowsour.2013.03.072CAS  Article  GoogleScholar  Mamantov,G.,Mamantov,C.:Advancesinmoltensaltchemistry5.ElsevierSciencePublishersScienceandTechnologyDiv(1983)Vutetakis,D.,Skidmore,D.,Byker,H.:Electrochemicaloxidationofmoltencarbonate-coalslurries.J.Electrochem.Soc.134(12),3027–3035(1987).https://doi.org/10.1149/1.2100334CAS  Article  GoogleScholar  Jiang,C.,Ma,J.,Arenillas,A.,Irvinea,J.T.S.:Applicationofternarycarbonateinhybriddirectcoalfuelcells.ECSTrans.59(1),281–288(2014).https://doi.org/10.1149/05901.0281ecstCAS  Article  GoogleScholar  Eom,S.,Cho,J.,Ahn,S.,Sung,Y.,Choi,G.,Kim,D.:Comparisonoftheelectrochemicalreactionparameterofgraphiteandsub-bituminouscoalinadirectcarbonfuelcell.EnergFuel30(4),3502–3508(2016).https://doi.org/10.1021/acs.energyfuels.5b02904CAS  Article  GoogleScholar  Li,C.,Yi,H.,Lee,D.:On-demandsupplyofslurryfuelstoaporousanodeofadirectcarbonfuelcell:attemptstoincreasefuel-anodecontactandrealizelong-termoperation.J.PowerSources309,99–107(2016).https://doi.org/10.1016/j.jpowsour.2016.01.080CAS  Article  GoogleScholar  Lee,E.-K.,Park,S.-A.,Jung,H.-W.,Kim,Y.-T.:Performanceenhancementofmoltencarbonate-baseddirectcarbonfuelcell(MC-DCFC)viaaddingmixedionic-electronicconductorsintoNianodecatalystlayer.J.PowerSources386(15),28–33(2018).https://doi.org/10.1016/j.jpowsour.2017.03.078CAS  Article  GoogleScholar  Elleuch,A.,Boussetta,A.,Halouani,K.,Li,Y.:Experimentalinvestigationofdirectcarbonfuelcellfueledbyalmondshellbiochar:PartII.Improvementofcellstabilityandperformancebyathree-layerplanarconfiguration.Inter.J.HydrogenEnergy38(36),16605–16614(2013).https://doi.org/10.1016/j.ijhydene.2013.07.061CAS  Article  GoogleScholar  Elleuch,A.,Halouani,K.,Li,Y.:Investigationofchemicalandelectrochemicalreactionsmechanismsinadirectcarbonfuelcellusingolivewoodcharcoalassustainablefuel.J.PowerSources.281(1),350–361(2015).https://doi.org/10.1016/j.jpowsour.2015.01.171CAS  Article  GoogleScholar  Bian,W.,Wu,W.,Orme,C.J.,Ding,H.,Zhou,M.,Ding,D.:Dual3Dceramictextileelectrodes:fastkineticsforcarbonoxidationreactionandoxygenreductionreactionindirectcarbonfuelcellsatreducedtemperatures.Adv.Funct.Mater.30(19),1–9(2020).https://doi.org/10.1002/adfm.201910096CAS  Article  GoogleScholar  Hao,W.,He,X.,Mi,Y.:Achievinghighperformanceinintermediatetemperaturedirectcarbonfuelcellswithrenewablecarbonasafuelsource.Appl.Energy135(15),174–181(2014).https://doi.org/10.1016/j.apenergy.2014.08.055CAS  Article  GoogleScholar  Hao,W.,Mi,Y.:AdirectcarbonfuelcellwithaCuO–ZnO–SDCcompositeanode.RSCAdv.6(55),50201–50208(2016).https://doi.org/10.1039/c6ra04949dCAS  Article  GoogleScholar  He,W.:Adaptationofaonemegawattmoltencarbonatefuelcellsystem.EnergyConvers.Manage.38(7),659–663(1997).https://doi.org/10.1016/S0196-8904(96)00080-5CAS  Article  GoogleScholar  Baur,E.,Brunner,R.:Überdieeisenoxyd-kathodeinderkohle-luft-kette.ZeitschriftfürElektrochemieundangewandtephysikalischeChemie43(9),725–727(1937).https://doi.org/10.1002/bbpc.19370430902CAS  Article  GoogleScholar  Anbar,M.:Methodsandapparatusforthepollution-freegenerationofelectrochemicalenergy.USPatentNo3,741,809(1973)Anbar,M.,McMillen,D.F.,Weaver,R.D.,Jorgensen,P.J.:Methodandapparatusforelectrochemicalgenerationofpowerfromcarbonaceousfuels.USPatentNo3,741,809(1976)McKee,D.W.:Gasificationofgraphiteincarbondioxideandwatervapor—thecatalyticeffectsofalkalimetalsalts.Carbon20(1),59–66(1982).https://doi.org/10.1016/0008-6223(82)90075-6CAS  Article  GoogleScholar  Dunks,G.B.:Electrochemicalstudiesofgraphiteoxidationinsodiumcarbonatemelt.Inorg.Chem.23(7),828–837(1984).https://doi.org/10.1021/ic00175a008CAS  Article  GoogleScholar  Cooper,J.F.,Krueger,R.,Cherepy,N.:Fuelcellapparatusandmethodthereof.USPatentNo6815105B2(2004)Luo,Z.,Wang,S.,Liao,Y.,Zhou,J.,Gu,Y.,Cen,K.:Researchonbiomassfastpyrolysisforliquidfuel.BiomassBioenergy26(5),455–462(2004).https://doi.org/10.1016/j.biombioe.2003.04.001CAS  Article  GoogleScholar  Huang,J.,Mao,Z.,Yang,L.,Peng,R.:SDC-Carbonatecompositeelectrolytesforlow-temperatureSOFCs.Electrochem.SolidState8(9),A437–A440(2005).https://doi.org/10.1149/1.1960139CAS  Article  GoogleScholar  Cooper,J.F.,Cherepy,N.,Krueger,R.L.:Tiltedfuelcellapparatus.USPatentNo6878479B2(2005)Cooper,J.F.:Reactionsofthecarbonanodeinmoltencarbonateelectrolyte.PresentationsinDirectCarbonFuelCellWorkshop,NETL(2003)Cooper,J.F.:Directconversionofcoalandcoal-derivedcarboninfuelcells.The2ndInternationalConferenceonFuelCellScience,EngineeringandTechnology(2004)Li,X.,Zhu,Z.H.,Roland,D.M.,Andrew,D.,John,B.,Liu,S.,Lu,G.Q.:Factorsthatdeterminetheperformanceofcarbonfuelsinthedirectcarbonfuelcell.Ind.Eng.Chem.Res.47(23),9670–9677(2008).https://doi.org/10.1021/ie800891mCAS  Article  GoogleScholar  Li,X.,Zhu,Z.,Roland,D.M.,John,B.,Andrew,D.:Modificationofcoalasafuelforthedirectcarbonfuelcell.J.Phys.Chem.A114(11),3855–3862(2010).https://doi.org/10.1021/jp9062719CAS  Article  GoogleScholar  Zhang,J.,Zhong,Z.,Shen,D.,Xiao,J.,Fu,Z.,Zhang,H.,Zhao,J.,Li,W.,Yang,M.:Characteristicsofafluidizedbedelectrodeforadirectcarbonfuelcellanode.J.PowerSources196(6),3054–3059(2011).https://doi.org/10.1016/j.jpowsour.2010.11.130CAS  Article  GoogleScholar  Ido,A.,Kawase,M.:Developmentofatubularmoltencarbonatedirectcarbonfuelcellandbasiccellperformance.J.PowerSources449(15),227483(2020).https://doi.org/10.1016/j.jpowsour.2019.227483CAS  Article  GoogleScholar  Gür,T.M.,Huggins,R.A.:Directelectrochemicalconversionofcarbontoelectricalenergyinahightemperaturefuelcell.J.Electrochem.Soc.139(10),L95(1992).https://doi.org/10.1149/1.2069025Article  GoogleScholar  Zhang,J.,Jiang,X.,Piao,G.,Yang,H.,Zhong,Z.:Simulationofafluidizedbedelectrodedirectcarbonfuelcell.Inter.J.HydrogenEnergy40(8),3321–3331(2015).https://doi.org/10.1016/j.ijhydene.2014.12.090CAS  Article  GoogleScholar  Kruesi,W.,Fray,D.:Fundamentalstudyoftheanodicandcathodicreactionsduringtheelectrolysisofalithiumcarbonate-lithiumchloridemeltusingacarbonanode.J.Appl.Electrochem.24(11),1102–1108(1994).https://doi.org/10.1007/BF00241307Article  GoogleScholar  Weaver,R.D.,Nanis,L.:Electrochemicaloxidationofcarboninamoltencarbonatecoal-airfuelcell.J.Electrochem.Soc.1981,316–333(1981).https://doi.org/10.1149/198109.0316PVArticle  GoogleScholar  Glenn,M.J.,Allen,J.A.,Donne,S.W.:Carbongasificationfromamoltencarbonateeutectic.EnergyTechnol-ger.(2019).https://doi.org/10.1002/ente.201900602Article  GoogleScholar  Watanabe,H.,Umehara,D.,Hanamura,K.:Impactofgasproductsaroundtheanodeontheperformanceofadirectcarbonfuelcellusingacarbon/carbonateslurry.J.PowerSources329,567–573(2016).https://doi.org/10.1016/j.jpowsour.2016.08.122CAS  Article  GoogleScholar  Kaklidis,N.,Strandbakke,R.,Arenillas,A.,Menéndez,J.A.,Konsolakis,M.,Marnellos,G.E.:Thesynergisticcatalyst-carbonateseffectonthedirectbituminouscoalfuelcellperformance.Inter.J.HydrogenEnergy44(20),10033–10042(2019).https://doi.org/10.1016/j.ijhydene.2019.02.038CAS  Article  GoogleScholar  Tamaru,S.,Kamada,M.:Brennstoffketten,derenArbeitstemperaturunterhalb600℃liegt.ZeitschriftfürElektrochemieundangewandtephysikalischeChemie41(2),93–96(1935).https://doi.org/10.1002/bbpc.19350410207CAS  Article  GoogleScholar  Thonstad,J.:TheelectrodereactionontheC,CO2electrodeincryolite-aluminamelts-ISteadystatemeasurements.Electrochim.Acta.15(10),1569–1580(1970).https://doi.org/10.1016/0013-4686(70)80079-2CAS  Article  GoogleScholar  Lee,E.-K.,Chun,H.H.,Kim,Y.-T.:EnhancingNianodeperformanceviaGd2O3additioninmoltencarbonate-typedirectcarbonfuelcell.Inter.J.HydrogenEnergy39(29),16541–16547(2014).https://doi.org/10.1016/j.ijhydene.2014.03.180CAS  Article  GoogleScholar  Bie,K.,Fu,P.,Liu,Y.,Muhammad,A.:Comparativestudyontheperformanceofdifferentcarbonfuelsinamoltencarbonatedirectcarbonfuelcellwithanovelanodestructure.J.PowerSources(2020).https://doi.org/10.1016/j.jpowsour.2020.228101Article  GoogleScholar  Eguchi,K.,Setoguchi,T.,Inoue,T.,Arai,H.:Electricalpropertiesofceria-basedoxidesandtheirapplicationtosolidoxidefuelcells.SolidStateIon.52(1–3),165–172(1992).https://doi.org/10.1016/0167-2738(92)90102-UCAS  Article  GoogleScholar  Zhu,B.:Functionalceria–salt-compositematerialsforadvancedITSOFCapplications.J.PowerSources114(1),1–9(2003).https://doi.org/10.1016/s0378-7753(02)00592-xCAS  Article  GoogleScholar  Elleuch,A.,Yu,J.,Boussetta,A.,Halouani,K.,Li,Y.:Electrochemicaloxidationofgraphiteinanintermediatetemperaturedirectcarbonfuelcellbasedontwo-phaseselectrolyte.Inter.J.HydrogenEnergy38(20),8514–8523(2013).https://doi.org/10.1016/j.ijhydene.2012.11.070CAS  Article  GoogleScholar  Li,Y.,Rui,Z.,Xia,C.,Anderson,M.,Lin,Y.S.:Performanceofionic-conductingceramic/carbonatecompositematerialassolidoxidefuelcellelectrolyteandCO2permeationmembrane.CatalToday148(3–4),303–309(2009).https://doi.org/10.1016/j.cattod.2009.08.009CAS  Article  GoogleScholar  Rui,Z.,Anderson,M.,Lin,Y.S.,Li,Y.:Modelingandanalysisofcarbondioxidepermeationthroughceramic-carbonatedual-phasemembranes.J.Membr.Sci.345(1–2),110–118(2009).https://doi.org/10.1016/j.memsci.2009.08.034CAS  Article  GoogleScholar  Lahijani,P.,Zainal,Z.A.,Mohammadi,M.,Mohamed,A.R.:ConversionofthegreenhousegasCO2tothefuelgasCOviatheboudouardreaction:areview.Renew.Sust.EnergyRev.41,615–632(2015).https://doi.org/10.1016/j.rser.2014.08.034CAS  Article  GoogleScholar  Jia,L.,Tian,Y.,Liu,Q.,Xia,C.,Yu,J.,Wang,Z.,Zhao,Y.,Li,Y.:Adirectcarbonfuelcellwith(moltencarbonate)/(dopedceria)compositeelectrolyte.J.PowerSources195(17),5581–5586(2010).https://doi.org/10.1016/j.jpowsour.2010.03.016CAS  Article  GoogleScholar  Wu,W.,Zhang,Y.,Ding,D.,He,T.:Ahigh-performingdirectcarbonfuelcellwitha3Darchitecturedanodeoperatedbelow600℃.Adv.Mater.30(4),1704745(2018).https://doi.org/10.1002/adma.201704745CAS  Article  GoogleScholar  Nabae,Y.,Pointon,K.D.,Irvine,J.T.S.:Ni/Cslurriesbasedonmoltencarbonatesasafuelforhybriddirectcarbonfuelcells.J.Electrochem.Soc.156(6),B716–B720(2009).https://doi.org/10.1149/1.3110862CAS  Article  GoogleScholar  AlexanderLipilin,IouriBalachov,LawrenceDubois,AngelSanjurjo,MichaelMcKubre,StevenCrouch-Baker,MarcHornbostel,Tanzella,F.:Liquidanodeelectrochemicalcell.USPatentNo2007/0269688A1(2007)Jain,S.L.,BarryLakeman,J.,Pointon,K.D.,Marshall,R.,Irvine,J.T.S.:ElectrochemicalperformanceofahybriddirectcarbonfuelcellpoweredbypyrolysedMDF.EnergyEnviron.Sci.2(6),687–693(2009).https://doi.org/10.1039/b820836kCAS  Article  GoogleScholar  Jiang,C.,Irvine,J.T.S.:Catalysisandoxidationofcarboninahybriddirectcarbonfuelcell.J.PowerSources196(17),7318–7322(2011).https://doi.org/10.1016/j.jpowsour.2010.11.066CAS  Article  GoogleScholar  Ruflin,J.,Perwich,A.D.,II.,Brett,C.,Berner,J.K.,Lux,S.M.:Directcarbonfuelcell:aproposedhybriddesigntoimprovecommercializationpotential.J.PowerSources213,275–286(2012).https://doi.org/10.1016/j.jpowsour.2012.04.048CAS  Article  GoogleScholar  Deleebeeck,L.,Hansen,K.K.:HDCFCperformanceasafunctionofanodeatmosphere(N2-CO2).J.Electrochem.Soc.161(1),F33–F46(2013).https://doi.org/10.1149/2.027401jesCAS  Article  GoogleScholar  Deleebeeck,L.,Ippolito,D.,Hansen,K.K.:EnhancinghybriddirectcarbonfuelcellanodeperformanceusingAg2O.Electrochim.Acta.152,222–239(2015).https://doi.org/10.1016/j.electacta.2014.11.064CAS  Article  GoogleScholar  Pointon,K.,Lakeman,B.,Irvine,J.,Bradley,J.,Jain,S.:Thedevelopmentofacarbon–airsemifuelcell.J.PowerSources162(2),750–756(2006).https://doi.org/10.1016/j.jpowsour.2005.07.023CAS  Article  GoogleScholar  Jain,S.,Lakeman,B.,Pointon,K.D.,Irvine,J.T.:Carboncontentinadirectcarbonfuelcell.Ecs.Trans.7(1),829–836(2007).https://doi.org/10.1149/1.2729172Article  GoogleScholar  Jain,S.L.,Nabae,Y.,Lakeman,B.J.,Pointon,K.D.,Irvine,J.T.S.:Solidstateelectrochemistryofdirectcarbon/airfuelcells.SolidStateIon.179(27–32),1417–1421(2008).https://doi.org/10.1016/j.ssi.2008.01.078CAS  Article  GoogleScholar  Lee,A.C.,Mitchell,R.E.,Gür,T.M.:Thermodynamicanalysisofgasification-drivendirectcarbonfuelcells.J.PowerSources194(2),774–785(2009).https://doi.org/10.1016/j.jpowsour.2009.05.039CAS  Article  GoogleScholar  Lee,A.C.,Mitchell,R.E.,Gür,T.M.:ModelingofCO2gasificationofcarbonforintegrationwithsolidoxidefuelcells.AIChEJ.55(4),983–992(2009).https://doi.org/10.1002/aic.11713CAS  Article  GoogleScholar  White,S.,Twardoch,U.:Thesolubilityandelectrochemistryofalkalimetaloxidesinthemolteneutecticmixtureoflithiumcarbonate-sodiumcarbonate-potassiumcarbonate.J.Appl.Electrochem.19(6),901–910(1989).https://doi.org/10.1007/BF01007939CAS  Article  GoogleScholar  Peeters,D.,Moyaux,D.,Claes,P.:(1999)SolubilityandsolvationofcarbondioxideinthemoltenLi2CO3/Na2CO3/K2CO3(43.5:31.5:25.0mol%)eutecticmixtureat973KII.TheoreticalPart.Eur.J.Inorg.Chem.4,589–592(1999).https://doi.org/10.1002/(SICI)1099-0682(199904)1999:4Article  GoogleScholar  Nakagawa,N.,Ishida,M.:Performanceofaninternaldirect-oxidationcarbonfuelcellanditsevaluationbygraphicexergyanalysis.Ind.Eng.Chem.Res.27(7),1181–1185(1988).https://doi.org/10.1021/ie00079a016CAS  Article  GoogleScholar  Hemmes,K.,Cassir,M.:Atheoreticalstudyofthecarbon/carbonate/hydroxide(electro-)chemicalsysteminadirectcarbonfuelcell.J.FuelCellSci.Technol.8(5),1(2011).https://doi.org/10.1115/1.4003750CAS  Article  GoogleScholar  Li,S.,Pan,W.,Wang,S.,Meng,X.,Jiang,C.,Irvine,J.T.:Electrochemicalperformanceofdifferentcarbonfuelsonahybriddirectcarbonfuelcell.Inter.J.HydrogenEnergy42(25),16279–16287(2017).https://doi.org/10.1016/j.ijhydene.2017.05.150CAS  Article  GoogleScholar  Lee,J.Y.,Song,R.H.,Lee,S.B.,Lim,T.H.,Park,S.J.,Shul,Y.G.,Lee,J.W.:Aperformancestudyofhybriddirectcarbonfuelcells:Impactofanodemicrostructure.Inter.J.HydrogenEnergy39(22),11749–11755(2014).https://doi.org/10.1016/j.ijhydene.2014.05.145CAS  Article  GoogleScholar  Ma,J.,Zhang,B.,Hou,X.,Gong,J.,Yu,H.,Xu,R.,Jiang,C.:Thefunctionofcarbonateinahybriddirectcarbonfuelcell.SolidStateIon.344,115094–115099(2020).https://doi.org/10.1016/j.ssi.2019.115094CAS  Article  GoogleScholar  McKee,D.,Chatterji,D.:Thecatalyticbehaviorofalkalimetalcarbonatesandoxidesingraphiteoxidationreactions.Carbon13(5),381–390(1975).https://doi.org/10.1016/0008-6223(75)90006-8CAS  Article  GoogleScholar  McKee,D.W.:Mechanismsofthealkalimetalcatalysedgasificationofcarbon.Fuel62(2),170–175(1983).https://doi.org/10.1016/0016-2361(83)90192-8CAS  Article  GoogleScholar  McKee,D.,Chatterji,D.:Thecatalyzedreactionofgraphitewithwatervapor.Carbon16(1),53–57(1978).https://doi.org/10.1016/0008-6223(78)90116-1CAS  Article  GoogleScholar  Nagase,K.,Shimodaira,T.,Itoh,M.,Zheng,Y.:KineticsandmechanismsofthereverseBoudouardreactionovermetalcarbonatesinconnectionwiththereactionsofsolidcarbonwiththemetalcarbonates.Phys.Chem.Chem.Phys.1(24),5659–5664(1999).https://doi.org/10.1039/A906687JCAS  Article  GoogleScholar  Selman,J.R.:Molten-saltfuelcells—technicalandeconomicchallenges.J.PowerSources160(2),852–857(2006).https://doi.org/10.1016/j.jpowsour.2006.04.126CAS  Article  GoogleScholar  Kulkarni,A.,Giddey,S.:Materialsissuesandrecentdevelopmentsinmoltencarbonatefuelcells.J.SolidStateElectr.16(10),3123–3146(2012).https://doi.org/10.1007/s10008-012-1771-yCAS  Article  GoogleScholar  Kudo,T.,Hisamitsu,Y.,Kihara,K.,Mohamedi,M.,Uchida,I.:X-raydiffractometricstudyofinsituoxidationofNiinLi/KandLi/Nacarbonateeutectic.J.PowerSources104(2),272–280(2002).https://doi.org/10.1016/S0378-7753(01)00962-4CAS  Article  GoogleScholar  Doyon,J.D.,Gilbert,T.,Davies,G.,Paetsch,L.:NiOsolubilityinmixedalkali/alkalineearthcarbonates.J.Electrochem.Soc.134(12),3035(1987).https://doi.org/10.1149/1.2100335CAS  Article  GoogleScholar  Scaccia,S.:InvestigationonNiOsolubilityinbinaryandternarymoltenalkalimetalcarbonatescontainingadditives.J.Mol.Liq.116(2),67–71(2005).https://doi.org/10.1016/j.molliq.2004.07.078CAS  Article  GoogleScholar  Huang,B.,Li,F.,Yu,Q.-C.,Chen,G.,Zhao,B.-Y.,Hu,K.-A.:StudyofNiOcathodemodifiedbyZnOadditiveforMCFC.J.PowerSources128(2),135–144(2004).https://doi.org/10.1016/j.jpowsour.2003.10.008CAS  Article  GoogleScholar  Kim,S.-G.,Yoon,S.P.,Han,J.,Nam,S.W.,Lim,T.H.,Oh,I.-H.,Hong,S.-A.:AstudyonthechemicalstabilityandelectrodeperformanceofmodifiedNiOcathodesformoltencarbonatefuelcells.Electrochim.Acta.49(19),3081–3089(2004).https://doi.org/10.1016/j.electacta.2004.01.027CAS  Article  GoogleScholar  Tanimoto,K.,Kojima,T.,Yanagida,M.,Nomura,K.,Miyazaki,Y.:Optimizationoftheelectrolytecompositionina(Li0.52Na0.48)2-2xAExCO3(AE=CaandBa)moltencarbonatefuelcell.J.PowerSources131(12),256–260(2004).https://doi.org/10.1016/j.jpowsour.2003.11.085CAS  Article  GoogleScholar  Soler,J.,Gonzalez,T.,Escudero,M.,Rodrigo,T.,Daza,L.:EndurancetestonasinglecellofanovelcathodematerialforMCFC.J.PowerSources106(1–2),189–195(2002).https://doi.org/10.1016/S0378-7753(01)01041-2CAS  Article  GoogleScholar  Matsuzawa,K.,Mizusaki,T.,Mitsushima,S.,Kamiya,N.,Ota,K.-I.:TheeffectofLaoxideadditiveonthesolubilityofNiOinmoltencarbonates.J.PowerSources140(2),258–263(2005).https://doi.org/10.1016/j.jpowsour.2004.08.041CAS  Article  GoogleScholar  Daza,L.,Rangel,C.,Baranda,J.,Casais,M.,Martınez,M.,Alonso,J.:ModifiednickeloxidesascathodematerialsforMCFC.J.PowerSources86(1–2),329–333(2000).https://doi.org/10.1016/S0378-7753(99)00499-1CAS  Article  GoogleScholar  Ota,K.-I.,Matsuda,Y.,Matsuzawa,K.,Mitsushima,S.,Kamiya,N.:EffectofrareearthoxidesforimprovementofMCFC.J.PowerSources160(2),811–815(2006).https://doi.org/10.1016/j.jpowsour.2006.04.055CAS  Article  GoogleScholar  Liu,Z.,Guo,P.,Zeng,C.:EffectofDyonthecorrosionofNiO/Niinmolten(0.62Li,0.38K)2CO3.J.PowerSources166(2),348–353(2007).https://doi.org/10.1016/j.jpowsour.2007.01.063CAS  Article  GoogleScholar  Suski,L.,Kołacz,J.,Mordarski,G.,Ruggiero,M.:Determinationofopen-circuitpotentialsatgas/electrode/YSZboundaryversusmoltencarbonatereferenceelectrodeatmediumtemperatures.Electrochim.Acta.50(14),2771–2780(2005).https://doi.org/10.1016/j.electacta.2004.11.023CAS  Article  GoogleScholar  Lee,J.-A.,Lee,H.-C.,Heo,Y.-W.,Lee,J.-H.,Kim,J.-J.:EffectofLidopingonsinteringcharacteristicsandmicrostructuralbehaviorofyttria-stabilizedzirconia.Ceram.Int.42(15),17339–17346(2016).https://doi.org/10.1016/j.ceramint.2016.08.030CAS  Article  GoogleScholar  Kohli,R.:Thethermodynamicpropertiesofalkalimetalcompoundsathightemperatures.J.Therm.Anal.Calorim.41(6),1571–1576(1994).https://doi.org/10.1007/BF02549955CAS  Article  GoogleScholar  Chandrakala,H.N.,Ramaraj,B.:Shivakumaraiah,siddaramaiah:influenceoflithiumpotassiumzirconatenanoparticlesontheelectricalpropertiesandstructuralcharacteristicsofpoly(vinylalcohol)films.J.Phys.Chem.Solids75(2),252–258(2014).https://doi.org/10.1016/j.jpcs.2013.09.025CAS  Article  GoogleScholar  Pasierb,P.,Gajerski,R.,Komornicki,S.,RÄkas,M.:ReactivityoflithiumandbariumcarbonateswithZrO2:Y2O3andNasiconinsolidstateelectrochemicalgassensors.J.Therm.Anal.Calorim.77,105–113(2004).https://doi.org/10.1023/B:JTAN.0000033193.98853.d0CAS  Article  GoogleScholar  Wade,J.L.,Lee,C.,West,A.C.,Lackner,K.S.:CompositeelectrolytemembranesforhightemperatureCO2separation.J.Membr.Sci.369(1–2),20–29(2011).https://doi.org/10.1016/j.memsci.2010.10.05CAS  Article  GoogleScholar  Xu,X.,Zhou,W.,Zhu,Z.:StabilityofYSZandSDCinmoltencarbonateeutecticsforhybriddirectcarbonfuelcells.RSCAdv.4(5),2398–2403(2014).https://doi.org/10.1039/c3ra46600kCAS  Article  GoogleScholar  Badwal,S.,Ciacchi,F.T.,Drennan,J.:Investigationofthestabilityofceria-gadoliniaelectrolytesinsolidoxidefuelcellenvironments.SolidStateIon.121(1–4),253–262(1999).https://doi.org/10.1016/S0167-2738(99)00044-2CAS  Article  GoogleScholar  Guo,L.Q.,Zhao,X.M.,Wang,B.C.,Bai,Y.,Xu,B.Z.,Qiao,L.J.:TheinitialstageofatmosphericcorrosiononinterstitialfreesteelinvestigatedbyinsituSPM.Corros.Sci.70,188–193(2013).https://doi.org/10.1016/j.corsci.2013.01.028CAS  Article  GoogleScholar  Jiao,Y.,Tian,W.,Chen,H.,Shi,H.,Yang,B.,Li,C.,Shao,Z.,Zhu,Z.,Li,S.-D.:Insitucatalyzedboudouardreactionofcoalcharforsolidoxide-basedcarbonfuelcellswithimprovedperformance.Appl.Energy141,200–208(2015).https://doi.org/10.1016/j.apenergy.2014.12.048CAS  Article  GoogleScholar  Ali,A.,ShehzadBashir,F.,Raza,R.,Rafique,A.,KaleemUllah,M.,Alvi,F.,Afzal,M.,Ghauri,M.,Belova,L.M.:Electrochemicalstudyofcompositematerialsforcoal-baseddirectcarbonfuelcell.Inter.J.HydrogenEnergy43(28),12900–12908(2018).https://doi.org/10.1016/j.ijhydene.2018.05.104CAS  Article  GoogleScholar  Jiang,C.,Ma,J.,Ana,A.,John,T.S.I.:Hybriddirectcarbonfuelcellswithdifferenttypesofmineralcoal.ECSTrans.57(1),3013–3021(2013).https://doi.org/10.1149/05701.3013ecstArticle  GoogleScholar  Jiang,C.,Ma,J.,Arenillas,A.,Irvine,J.T.:Applicationofternarycarbonateinhybriddirectcoalfuelcells.ECSTrans.59(1),281–288(2014).https://doi.org/10.1149/05901.0281ecstCAS  Article  GoogleScholar  Chien,A.C.,Arenillas,A.,Jiang,C.,Irvine,J.T.S.:Performanceofdirectcarbonfuelcellsoperatedoncoalandeffectofoperationmode.J.Electrochem.Soc.161(5),F588–F593(2014).https://doi.org/10.1149/2.025405jesCAS  Article  GoogleScholar  Ju,H.,Eom,J.,Lee,J.K.,Choi,H.,Lim,T.-H.,Song,R.-H.,Lee,J.:Durablepowerperformanceofadirectash-freecoalfuelcell.Electrochim.Acta.115,511–517(2014).https://doi.org/10.1016/j.electacta.2013.10.124CAS  Article  GoogleScholar  Devyatkin,S.V.,Pisanenko,A.D.,Shapoval,V.I.:Chemicalandelectrochemicalbehaviorofcarbonatemeltscontainingsiliconoxide.Russ.J.Appl.Chem.75(4),562–564(2002).https://doi.org/10.1023/A:101950482CAS  Article  GoogleScholar  Tulloch,J.,Allen,J.,Wibberley,L.,Donne,S.:Influenceofselectedcoalcontaminantsongraphiticcarbonelectro-oxidationforapplicationtothedirectcarbonfuelcell.J.PowerSources260(15),140–149(2014).https://doi.org/10.1016/j.jpowsour.2014.03.026CAS  Article  GoogleScholar  Eom,S.,Ahn,S.,Kang,K.,Choi,G.:Correlationsbetweenelectrochemicalresistancesandsurfacepropertiesofacid-treatedfuelincoalfuelcells.Energy140(2),885–892(2017).https://doi.org/10.1016/j.energy.2017.09.034CAS  Article  GoogleScholar  Eom,S.,Ahn,S.,Choi,G.:Effectoffuelacidtreatmentonthereductionofelectrochemicalresistanceinadirectcarbonfuelcellsystem.EnergyFuel35(5),4493–4501(2021).https://doi.org/10.1021/acs.energyfuels.0c03714CAS  Article  GoogleScholar  Xie,H.,Zhai,S.,Chen,B.,Liu,T.,Zhang,Y.,Ni,M.,Shao,Z.:CoalpretreatmentandAg-infiltratedanodeforhigh-performancehybriddirectcoalfuelcell.Appl.Energy(2020).https://doi.org/10.1016/j.apenergy.2019.114197Article  GoogleScholar  Dudek,M.:Ontheutilizationofcoalsamplesindirectcarbonsolidoxidefuelcelltechnology.SolidStateIon.271(2),121–127(2015).https://doi.org/10.1016/j.ssi.2014.09.034CAS  Article  GoogleScholar  Kim,J.-W.,Lee,Y.-D.,Lee,H.-G.:DecompositionofLi2CO3byinteractionwithSiO2inmoldfluxofsteelcontinuouscasting.ISIJInt.44(2),334–341(2004).https://doi.org/10.2355/isijinternational.44.334CAS  Article  GoogleScholar  Li,C.,Yi,H.,Eom,S.,Choi,G.,Choi,T.-Y.,Lee,D.:Intrinsicsolid-statereactioncharacteristicsofcoalsandcharsinadirectcarbonfuelcell:withfocusonsignificanceassessmentoffuel-bornefactors.EnergyFuel34(4),4129–4138(2020).https://doi.org/10.1021/acs.energyfuels.9b04387CAS  Article  GoogleScholar  Cai,W.,Liu,J.,Liu,P.,Liu,Z.,Xu,H.,Chen,B.,Li,Y.,Zhou,Q.,Liu,M.,Ni,M.:Adirectcarbonsolidoxidefuelcellfueledwithcharfromwheatstraw.Inter.J.HydrogenEnergy43(7),2468–2477(2018).https://doi.org/10.1002/er.3968CAS  Article  GoogleScholar  Xu,L.J.,Liu,S.A.,Wang,Z.Z.,Liu,C.Y.,Li,S.G.:ZincisotopiccompositionsofmigmatitesandgranitoidsfromtheDabieOrogen,centralChina:Implicationsforzincisotopicfractionationduringdifferentiationofthecontinentalcrust.Lithos324,454–465(2019).https://doi.org/10.1016/j.lithos.2018.11.028CAS  Article  GoogleScholar  Peng,F.,Li,Y.,Nash,P.,Cooper,J.F.,Parulekar,S.J.,Selman,J.R.:Directcarbonfuelcells–wettingbehaviorofgraphiticcarboninmoltencarbonate.Inter.J.HydrogenEnergy41(41),18858–18871(2016).https://doi.org/10.1016/j.matchemphys.2006.06.006CAS  Article  GoogleScholar  Chen,M.,Wang,C.,Niu,X.,Zhao,S.,Tang,J.,Zhu,B.:Carbonanodeindirectcarbonfuelcell.Inter.J.HydrogenEnergy35(7),2732–2736(2010).https://doi.org/10.1016/j.ijhydene.2009.04.051CAS  Article  GoogleScholar  Hong,S.-G.,Selman,J.R.:WettingcharacteristicsofcarbonatemeltsunderMCFCoperatingconditions.J.Electrochem.Soc.151(1),A77–A84(2004).https://doi.org/10.1149/1.1629094CAS  Article  GoogleScholar  Cao,D.,Wang,G.,Wang,C.,Wang,J.,Lu,T.:Enhancementofelectrooxidationactivityofactivatedcarbonfordirectcarbonfuelcell.Inter.J.HydrogenEnergy35(4),1778–1782(2010).https://doi.org/10.1016/j.ijhydene.2009.12.133CAS  Article  GoogleScholar  Watanabe,H.,Kimura,A.,Okazaki,K.:Impactofternarycarbonatecompositiononthemorphologyofthecarbon/carbonateslurryandcontinuouspowergenerationbydirectcarbonfuelcells.EnergyFuel30(3),1835–1840(2016).https://doi.org/10.1021/acs.energyfuels.5b02224CAS  Article  GoogleScholar  Ahn,S.Y.,Eom,S.Y.,Rhie,Y.H.,Sung,Y.M.,Moon,C.E.,Choi,G.M.,Kim,D.J.:Applicationofrefusefuelsinadirectcarbonfuelcellsystem.Energy51(1),447–456(2013).https://doi.org/10.1016/j.energy.2012.12.025CAS  Article  GoogleScholar  Gür,T.M.:Solidfuelutilizationinhightemperaturefuelcells.ECSTrans.41(12),29–38(2019).https://doi.org/10.1149/1.3697426Article  GoogleScholar  Jayakumar,A.,Küngas,R.,Roy,S.,Javadekar,A.,Buttrey,D.J.,Vohs,J.M.,Gorte,R.J.:Adirectcarbonfuelcellwithamoltenantimonyanode.EnergyEnviron.Sci.(2011).https://doi.org/10.1039/c1ee01863aArticle  GoogleScholar  DownloadreferencesAcknowledgementsTheresearchersappreciatethefundingsupportprovidedbytheSichuanScienceandTechnologyProgram(Grantnumber2019YFH0177,2021YFH0092),theZigongScienceandTechnologyProgram(Grantnumber2019YYJC24,2020YGJC18)andtheTalentIntroductionPlanofSichuanUniversityofScienceandEngineering(Grantnumbers2016RCL36,2016RCL37).AuthorinformationAuthornotesCanCuiandShuangbinLicontributedequallytothiswork.AuthorsandAffiliationsSchoolofMaterialsScienceandEngineering,SichuanUniversityofScienceandEngineering,Zigong,643000,Sichuan,People’sRepublicofChinaCanCui, JunyiGong, KeyanWei, XiangjunHou, CairongJiang & JianjunMaSchoolofChemistry,UniversityofStAndrews,StAndrews,KY169ST,UKShuangbinLiMaterialCorrosionandProtectionKeyLaboratoryofSichuanProvince,Zigong,643000,Sichuan,People’sRepublicofChinaCairongJiang & JianjunMaInstitutefortheDevelopmentofEnergyforAfricanSustainability(IDEAS),UniversityofSouthAfrica,cnrChristiaandeWetandPioneerRoad,PrivateBagX6,Florida,1710,SouthAfricaYaliYaoAuthorsCanCuiViewauthorpublicationsYoucanalsosearchforthisauthorin 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ReprintsandPermissionsAboutthisarticleCitethisarticleCui,C.,Li,S.,Gong,J.etal.Reviewofmoltencarbonate-baseddirectcarbonfuelcells. MaterRenewSustainEnergy10,12(2021).https://doi.org/10.1007/s40243-021-00197-7DownloadcitationReceived:04March2021Accepted:25June2021Published:02July2021DOI:https://doi.org/10.1007/s40243-021-00197-7SharethisarticleAnyoneyousharethefollowinglinkwithwillbeabletoreadthiscontent:GetshareablelinkSorry,ashareablelinkisnotcurrentlyavailableforthisarticle.Copytoclipboard ProvidedbytheSpringerNatureSharedItcontent-sharinginitiative KeywordsDirectcarbonfuelcellCarbonateElectrolyteCatalystTriple-phaseboundaries(TPBs) DownloadPDF Advertisement