Powergenerationusingspinelmanganesecobaltoxide

Powergenerationusingspinelmanganese–cobaltoxideasacathodecatalystformicrobialfuelcellapplicationsMohamedMahmouda,⇑,TarekA.Gad-Allaha,K.M.El-Khatibb,FatmaEl-GoharyaaWaterPollutionResearchDepartment,NationalResearchCentre,El-TahrirSt.,Dokki,P.O.Box12311,Cairo,EgyptbChemicalEngineeringandPilot-PlantDepartment,NationalResearchCentre,El-TahrirSt.,Dokki,P.O.Box12311,Cairo,EgyptarticleinfoArticlehistory:Received19July2011Receivedinrevisedform26August2011Accepted29August2011Availableonline5September2011Keywords:MicrobialfuelcellsOxygenreductionreactionCathodecatalystManganese–cobaltoxidePowergenerationabstractThisstudyfocusedontheuseofspinelmanganese–cobalt(Mn–Co)oxide,preparedbyasolidstatereac-tion,asacathodecatalysttoreplaceplatinuminmicrobialfuelcells(MFCs)applications.SpinelMn–Cooxides,withanMn/Coatomicratiosof0.5,1,and2,werepreparedandexaminedinanaircathodeMFCswhichwasfedwithamolasses-ladensyntheticwastewaterandoperatedinbatchmode.AmongthethreeMn–Cooxidecathodesandafter300hofoperation,theMn–CooxidecatalystwithMn/Coatomicratioof2(MnCo-2)exhibitedthehighestpowergeneration113mW/m2atcellpotentialof279mV,whichwerelowerthanthoseforthePtcatalyst(148mW/m2and325mV,respectively).Thisstudyindi-catedthatusingspinelMn–Cooxidetoreplaceplatinumasacathodiccatalystenhancespowergenera-tion,increasescontaminantremoval,andsubstantiallyreducesthecostofMFCs.2011ElsevierLtd.Allrightsreserved.1.IntroductionIncreasedeconomicgrowthandsocialdevelopmentareleadingtoalargegapbetweenenergydemandsandtheavailabilityoffos-silfuels.Currentmethodstoproduceenergyarenotsustainable,andconcernsaboutclimatechangeandglobalwarmingrequiredevelopingnewmethodsofenergyproductionusingrenewableandcarbon-neutralsources.Thedevelopmentofelectrogenicreac-torsbasedonmicrobialfuelcells(MFCs)representsanewap-proachforgeneratingelectricityfromwasteandbiomass(Loganetal.,2006;Rabaeyetal.,2005).Althoughtheconceptofelectricityproductionfrombacteriawasconceivednearlyacenturyago(Cohen,1931),onlyrecentlythetechnologyhasbeensufficientlyimprovedtomakeitusefulasamethodforenergygeneration.Onenear-termapplicationofMFCswillbetoproduceelectricityfromwastewater,providinganewwaytosimultaneouslytreatwastewaterwhileobtainingasourceofcleanandrenewableen-ergy(Liuetal.,2004;Yuetal.,2007).Furtherdevelopmentwillal-lowMFCstobeusedforrenewableenergyproductionfromothersourcesofbiomass.AlargeefforthasbeeninvestedtoenhanceenergyproductioninMFCs.Mostattentionwasonsubstratedegradation,electrongeneration,andtransferinanodechambers(Lovely,2006;Loganetal.,2006;Lietal.,2010).Severalimportantfactorsincludingsubstrateconcentration,pH,conductivity,microbialactivity,cir-cuitresistance,electrode,andmembranematerialhavebeenextensivelyinvestigated(Aeltermanetal.,2008;Lietal.,2010).However,inrecentstudies,oxygenreductionandelectronaccep-tanceinthecathodechamberhavebeenfoundasthelimitingstepforenergyproductionduetotheslowreactionkineticsoftheoxy-genreductionrate(ORR)(Jangetal.,2004;Phametal.,2004).Platinum(Pt)hasbeenwidelyusedasthecathodecatalysttoacceleratetheORRandelectronacceptanceinMFCs(LiuandLogan,2004),butthehighcostofplatinum,whichestimatedataround50%ofthetotalcapitalcostofthesystem,posesanobstacleintheapplicationofMFCs(Rozendaletal.,2008).Moreover,theeffectivenessofPtasORRcatalystwouldbefardiminishedduetothelowerpowerdensitythanfuelcells,andcontaminationfrombiologicalprocess(TartakovskyandGuiot,2006).Alternatively,severalPt-freenon-nobletransitionmetalssuchasCo,FeandMnandtheirsupportingstructureshavebeenstudiedintheformofiron(III)phthalocyanine(FePc)andcobalttetramethoxyphenyl-porphyrin(CoTMPP)forORR(Zhaoetal.,2005;Chengetal.,2006;Youetal.,2006;Lefebvreetal.,2009;Duteanuetal.,2010).Moreover,stainlesssteelalloyandnickelalloyshavebeenusedforalternativelowcostcatalystsinmicrobialelectrolysiscells(Sel-emboetal.,2009).Theystatedthattheperformanceofstainlesssteelandnickelalloyswassimilarorbetterthanplatinumsheetmetalwhenusedascathodes.StainlesssteelA286showedthebestperformanceofallthealloystestedatanappliedpotentialof0.9V.Anickeloxidelayerelectrodepositedonthemetalsurfacesim-provedtheircatalyticperformancebyatleastafactoroffour.Ina0960-8524/$-seefrontmatter2011ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2011.08.123⇑Correspondingauthor.Tel./fax:[phone].E-mailaddresses:[e-mail],m_mahmoud@lycos.-com(M.Mahmoud).BioresourceTechnology102(2011)10459–10464ContentslistsavailableatSciVerseScienceDirectBioresourceTechnologyjournalhomepage:(2010)investigatedmanganeseoxideswithacryptomelane-typeoctahedralmolecularsieve(OMS-2)structureasacathodecatalystinordertoreplaceplatinum.Theyinvestigatedthreecatalystsdopedwithcobalt(Co-OMS-2),copper(Cu-OMS-2),andcerium(Ce-OMS-2).Theresultsshowedthatafter400hofoperation,theCo-OMS-2andCu-OMS-2exhibitedgoodcatalyticperformanceinORRwithpowerdensityof180and165mW/m2,respectively.Inanotherstudy,Liuetal.(2010)demonstratedthatanano-structuredmanganeseoxide(MnOx),preparedbyanelec-trochemicallydepositionmet