铋纳米颗粒负载的氮掺杂石墨毡用于稳定高效的铁铬液流电池.pdf

Cite this:NewCarbonMaterials,2024,39(1):131-141DOI:10.1016/S1872-5805(24)60837-1Bismuth nanoparticles anchored on N-doped graphite felts to givestable and efficient iron-chromium redox flow batteriesCHEHang-xin1,GAOYu-fei2,YANGJia-hui1,HONGSong1,*,HAOLei-duan1,XULiang1,SanaTaimoor1,AlexW.Robertson3,SUNZhen-yu1,*（1.State Key Laboratory of Organic-Inorganic Composites,College of Chemical Engineering,Beijing Universityof Chemical Technology,Beijing 100029,China;2.School of Mechanical and Electrical Engineering,Guilin University of Electronic Technology,Guilin 541004,China;3.Department of Physics,University of Warwick,Coventry CV4 7AL,UK）Abstract：Iron-chromiumredoxflowbatteries(ICRFBs)useabundantandinexpensivechromiumandironastheactivesub-stancesintheelectrolyteandhavegreatpotentialasacost-effectiveandlarge-scaleenergystoragesystem.However,theyarestillplaguedbyseveralissues,suchasthelowelectrochemicalactivityofCr3+/Cr2+andtheoccurrenceoftheundesiredhydrogenevolu-tionreaction(HER).Wereportthesynthesisofamorphousbismuth(Bi)nanoparticles(NPs)immobilizedonN-dopedgraphitefelts(GFs)byacombinedself-polymerizationandwet-chemistryreductionstrategyfollowedbyannealing,whichareusedasthenegat-iveelectrodesforICRFBs.TheresultingBiNPsreactwithH+toformintermediatesandgreatlyinhibittheparasiticHER.Inaddi-tion,thecombinedeffectofBiandNdopantsonthesurfaceofGFdramaticallyincreasestheelectrochemicalactivityofFe2+/Fe3+andCr3+/Cr2+,reducesthechargetransferresistance,andincreasesthemasstransferratecomparedtoplainGF.AttheoptimumBi/Nratioof2,ahighcoulombicefficiencyofupto97.7%ismaintainedevenfor25cyclesatdifferentcurrentdensities,theenergyeffi-ciencyreaches85.8%at60.0mAcm2,exceedingmanyotherreportedmaterials,andthecapacityreaches862.7mAhL1after100cycles,whichisabout5.3timesthatofbareGF.Key words:Iron-chromiumflowbattery；Bi；Negativeelectrode；Nitrogendoping；Graphitefelt1IntroductionThe development of clean energy sources is acurrent international priority.Renewable powersbasedonwindandsolargenerationarenowbecom-ingprimaryenergysourcesforpoweringoursocieties.However,theinherentintermittencyofrenewableen-ergysourcesbringsaboutseriouschallengesforen-suringaconsistentsupplyofpowertothegrid.En-ergystoragetechnologyisaneffectivetoolforachiev-ingefficientrenewableenergyutilizationandstablepowersystemoperation12.Comparedwithphysicalenergy storage technology such as pumped storage,chemical energy storage technology offers greaterflexibilityintermsofscaleandlocation.Amongthevariouschemicalenergystoragemethods,redoxflowbatteries(RFBs)have become a large-scale batteryenergystoragetechnologywithgreatpotentialowingtotheirlonglife,goodsafety,andhighenergyeffi-ciency3.RFBsareconsideredasoneofthebestchoicesfor megawatt-level power storage,and megawattdemonstrationsystems have been installed,for ex-ample,inChina,theUnitedStatesandAustralia.ThechargeanddischargeoftheRFBsarerealizedmainlybythe change in the redox state of the active sub-stanceinthesolutiononbothsidesofthepositiveandnegativeelectrodes.An RFB consists of two elec-trodes,two electrolyte tanks,and an ion exchangemembrane.Theelectrolyteisusuallystoredinanex-ternaltankandpumpedintothereactor.Theredoxre-actioniscarriedoutontheelectrodesurface,andtheactivesubstanceafterthereactionflowsbacktotheReceived date：2023-10-27；Revised date：2023-12-22Corresponding author：HONGSong,AssociateProfessor.E-mail:;SUNZhen-yu,Professor.E-mail:Author introduction：CHEHang-xin,Masterstudent.E-mail:Supplementarydataassociatedwiththisarticlecanbefoundintheonlineversion.Homepage:http:/ variety of RFBs have been developed,in-cludingall-vanadium flow batteries(VRFBs),vana-dium-ironRFBs,zinc-bromineRFBs,andiron-chro-miumflowbatteries(ICRFBs)5.Amongthem,ICRF-Bsarethefirstrealsenseofflowbatteryinhistory.Itusescheapandabundantchromiumandironastheactivesubstancesintheelectrolyteandisthereforeavery cost-effective energy storage system comparedwithotherkindsofflowbatteries6.However,practical implementation of ICRFBsmustaddresstheproblemsofslowCr3+/Cr2+kineticsandsuppressthecompetingHER.Graphitefelt(GF)istypicallythefirstchoiceofICRFBelectrodemateri-alsowingtoitsfavorableconductivity,stability,highspecificsurface area,porosity,and corrosion resist-ance79.However,GF also has drawbacks such aspoorhydrophilicity,insufficientelectrochemicalactivity,and low reversibility.The surfaces of GFelectrodeshavebeenmodifiedinanattempttocir-cumvent these issues and thus improve the ICRFBperformance.Forexample,indiumions10havebeendemonstrated to inhibit the HER and accelerateCr3+/Cr2+kinetics.ByloadingasmallamountofPb(100-200 g cm2)and Au(12-25 g cm2)ontoGF11,thekineticsoftheCr3+/Cr2+redoxreactionhasbeen promoted1213.Alternatively,Bi5,14,Tl15,SiO216,CoO1718,andothermodifiedelectrodeshavealsobeenutilizedtoacceleratetheCr3+/Cr2+redoxre-actions.Here,weproposeasynthesismethodforthepre-parationofBinanoparticles(NPs)immobilizedonN-dopedgraphitefelt(Bi/N-GF)byacombinedinterfa-cial copolymerization and wet-chemistry reductionapproachfollowedbyannealing,whichispromisingasanefficientnegativeelectrodeforICRFBs.As-ob-tainedcatalystsignificantlypromotesthereactivityofCr3+/Cr2+electrodes,improvesmasstransferkinetics,andalleviatestheHERoftheanode.Duringgalvano-staticchargeanddischarge,theBi/N-GFexhibitsex-cellentrateperformanceandlongstabilityduringcyc-ling.TheCoulombicefficiency(CE)ismaintainedat97.7%after25cyclesatvariouscurrentdensities.At60.0mAcm2,theenergyefficiency(EE)approaches85.8%.Thecapacityreaches862.7mAhL1after100cycles,whichisabout5.3timesthatofplainGF.2Experimental 2.1 Materials and preparationFeCl24H2O,CrCl36H2O and Bi(NO3)35H2OwerepurchasedfromMacklin.HClwasboughtfromBeijingTongGuangFineChemicalsCompany.Trisanddopamine(DA)hydrochloridewereprovidedbyShanghaiAladdin Biochemical Technology.Deion-izedwater(18.2Mcm)wasobtainedfromaMilli-pore system.N2 gas(99.999%purity)was boughtfromBeijingHaipuGasCo.,Ltd.Graphitefelts(GFs)were bought from Liaoning Jin Gu carbon materialCo.LTD,China.Single cells were provided byWuhanZhishengNewEnergyCo.,LTD.LinesandperistalticpumpswerepurchasedfromBaodingRiverFluidTechnologyCo.,LTD.Theelectrolyteof1molL1Fe/Cr(containing1molL1FeCl24H2Oand1molL1CrCl36H2O)+3 mol L1 HCl was prepared by dissolvingFeCl24H2O and CrCl36H2O in a concentrated HClsolution,andthendilutedquantitativelywithdeoxid-izedwateratroomtemperature.Deoxygenatedwaterwaspreparedbygraduallyheatingupdeionizedwaterto80C,thenintroducedintothesolutionwithava-cuum pump.The internal pressure increased,withsteady oxygen bubble formation observed until itceased,yielding deoxygenated water.The preparedelectrolyte was left for 3 h before electrochemicaltests.Graphitefelts(3cm3cm)werecleanedandcalcinedinairat500Cfor5h19.100mgdopaminehydrochloridesolutionwasdissolvedinaTrisHClbuffersolution(10mmolL1Tris,pH=8.5),andthepre-treatedGFwasaddedandstirredfor1hatroomtemperature.Then 200 mg Bi(NO3)35H2Owas dis-solvedin50mLglycolsolution,andthenaddedtotheabovesolutionandstirredatroomtemperaturefor7h.Finally,thepreparedsamplesweredriedinanovenat60C for 24 h.The resulting samples were sub-sequentlycalcinedat450Cfor1handfurtherat132新型炭材料（中英文）第39卷700Cfor2h1920inaquartzfurnaceunderN2atmo-sphere.As a consequence,Bi/N-GF was obtai-ned,asillustratedinFig.1.TheloadedBiinBi/N-GFwasestimatedtobeabout10.1%basedonenergy-dis-persiveX-rayspectroscopy(EDS)measurementsdur-ingtransmissionelectronmicroscopy(TEM)observa-tion.Byreplacingglycolwithdistilledwaterwhilere-maining the other conditions unchanged,bigger Binanoparticles supported on N-doped GF(named asBi_bigger/N-GF)were obtained.The number Bi/N-GF-0.5,Bi/N-GF-1andBi/N-GF-2referstoatheoret-icalcontentofBi/N.ForthefabricationofBi-GF,200mgBi(NO3)35H2Owasdissolvedin50mLglycolsolu-tionandthepre-treatedGFwasaddedandstirredfor8 h.The subsequent drying and thermal treatmentstepswerethesameasthoseusedforthepreparationofBi/N-GF.ForthepreparationofN-GF,100mgdopaminehydrochloride solution was dissolved in a Tris-HClbuffersolution(10mmolL1Tris,pH=8.5),andthepre-treatedGFwasaddedandstirredfor8hatroomtemperature.Thesubsequentdryingandthermaltreat-mentstepswerethesameasthoseusedfortheprepar-ationofBi/N-GF.2.2 CharacterizationScanningelectron microscopy(SEM)was per-formedonanS-4800microscopewitha3kVacceler-ating voltage.TEM and aberration corrected high-angle annular dark-field scanning TEM(HAADF-STEM)weredonewithaJEOLARM200microscopewitha200kVacceleratingvoltage.STEMsampleswerepreparedbydepositingadropletofsuspensionontoaCugridcoatedwithalaceycarbonfilm.X-raydiffraction(XRD)patterns were recorded on aD/MAX-RC diffractometer operated at 30 kV and100mAwithCuKradiation(=0.15418nm)atascanningrateof5min1.X-rayphotoelectronspec-troscopy(XPS)measurementswerecarriedoutusinga Thermo Scientific ESCALAB 250Xi instrument.Theinstrumentwasequippedwithanelectronfloodandascanningiongun.Nospecialtreatmentwasap-pliedtothesamplesbeforeXPSanalysis.TheCCbindingenergyof284.8eVwasusedforinternalcal-ibration.PeakdeconvolutionwasperformedwiththeAvantagesoftware.2.3 Electrochemical measurementCyclic voltammetry(CV)and electrochemicalimpedancespectroscopy(EIS)weretestedat65.0Cusingathree-electrodesystemconsistingofagraph-iteworkingelectrode(6.0mmindiameter),asatur-atedcalomelreferenceelectrode(SCE),andaplatin-umnetwork(1cm2)counterelectrodeonaCHI660electrochemicalworkstation(ShanghaiChenHuaIn-strumentCo.,LTD).Thevolumeofelectrolytethatwasusedduringthetestswas20mL.CVmeasure-mentswithdifferentsweeprateswereperformedinthepotentialrangesfrom0.8to0.8V.EISwascon-ductedunderadirectcurrentvoltagerangeof0.5Vand 0.35 V,a frequency range of 100 kHz and10MHz,andanamplitudeof5mV.ThetestresultswerefittedwiththeZviewsoftware.2.4 Flow battery testAs-obtainedBi/N-GF(diameter:3cm3cm)andNafion117wereusedastheanodeandcationex-change membranes,respectively.1 mol L1 FeCl24H2O and 1 mol L1 CrCl36H2O dissolved in a3molL1HClsolutionswereutilizedastheanalyteandcatholyte,respectively.Toeliminateanyresidualair,thestoragetanklinkedtothecellwaspurgedwithN2for30minandwassubsequentlyheatedinawaterbathto653C.TheelectrolytewasintroducedintoPolymerizationHeat treatmentBi NPsN-doped GF3-HydroxytyraminehydrochlorideBi3+pH=8.5Graphite felt450 oC 1 hand 700 oC 2 hHOHOHCINH2Fig.1AschematicillustrationofthesynthesisofBi/N-GF第1期CHEHang-xinetal:BismuthnanoparticlesanchoredonN-dopedgraphitefeltstogivestableand133asingularcellataflowrateof120.0mLmin1.AllvoltagemeasurementswereversusSCEunlessother-wisestated.Electrochemicaltestswereconductedus-ingapotentiostat/currentmeter,withacut-offvoltageof0.8Vforthechargetestand1.2Vforthedis-chargetest.TheCEwascalculatedbytheratioofthenumber of electrons transferred during discharge tothenumberofelectronstransferredduringcharge.Intheprocessofchargeanddischarge,thecrosscontam-inationofpositiveandnegativeelectrolytesnormallyleadstolowcoulombicefficiency.Voltageefficiency(VE)was determined by the ratio of average dis-chargevoltagetoaveragechargevoltage.EEwases-timatedbytheratiooftheoutputenergyofthedis-chargeprocesstothestoredenergyofthechargepro-cess.3ResultsanddiscussionTofabricateBi/N-GF,GFwasfirstcoatedwithpolydopamine(PDA)fromtheself-polymerizationofoxidizedDA.Thenitrogen-enrichedlayerfacilitatedthedepositionofBiNPsresultingfromglycolreduc-tionatelevatedtemperature.Afterfurtherheattreat-ment,BiNPsadheredtothesurfaceofN-dopedGFwere attained.The morphologies of GF,N-GF,Bi-GF,andBi/N-GF(theBi/Nmassratiois2.0unlessstated otherwise)were characterized by SEM(Fig.S1ad).Atlowmagnifications,alargenumberofin-terconnectedone-dimensionalfiberswereobservedinallcases.IncontrasttotherelativelysmoothsurfaceofbareGF,N-GFandBi-GFsamples,theoutersur-face of Bi/N-GF was seen to be densely depositedwithaggregates.ThisindicatesthattheintroductionofadditionalNspeciesinGFfavorstheanchoringofBiparticlesonthesurfaceofGF.ThemicrostructureoftheresultingBi/N-GFwasfurtherinvestigatedby(S)TEM.Itisapparentthatalmostallgraphitefelts(ex-istingasgraphiteflakes)weredecoratedwithBiNPswithanirregularshape(Fig.2a,b).TheaveragesizeofBiNPswasestimatedtobeabout25nm.Inaddi-tiontosomebigaggregates,ahighproportionofNPsoflessthan15nmwereidentified(Fig.2c,d).Theseformed NPs lack crystallinity,as confirmed by fastFouriertransform(FFT)(Fig.2e).TheformationofBiandNspeciesonGFwasvalidatedbytheSTEMimages and corresponding EDS elemental maps(a)(b)(c)(d)(e)(f)(g)(h)(i)C KBi MN KFig.2STEMcharacterisationofBi/N-GF.(a)Lowmagnificationbrightfield(BF)-STEMimage.(b)Magnifiedviewoftheindicatedareain(a),showingnanoparticledecorationofthegraphiteflake.(c)HighmagnificationHAADF-STEMimageoftheparticles,showingamorphousaggregationofatomsandsomeloosesingleatoms.(d)HAADF-STEMimageand(e)fastFouriertransformofananoparticle,confirminglackofcrystallinity.(f)HAADF-STEMimageand(gi)accompanyingEDSmapping,confirmingBiaggregatenanoparticlesdispersedontheN-dopedgraphitefelt134新型炭材料（中英文）第39卷(Fig.2fi).As illustrated in the XRD patterns of GF andBi/N-GF(Fig.3a),nocharacteristicdiffractionpeaksofBiwereobserved.Thethreepronouncedpeaksap-pearingat26.6,44.7and55.1canbeascribedtothe(004),(102)and(105)crystalreflectionsofCinGF,respectively(PDF#261080).Thesurfacecom-positionandoxidationstateofthesampleswereana-lyzedbyXPS(Fig.3b).TheC1sXPSspectraforboth GF and Bi/N-GF can be deconvoluted into 3peaks corresponding to CC(284.8 eV),CC(285.3eV)andCO(286.2eV)(Fig.S2).NotethatthecontentofCCinBi/N-GFissimilartothatinGFbutthecontentofCOishigher.Moreoxygen-containingfunctionalgroupscanboosttheCr3+/Cr2+redox reaction,benefiting the ICRFB.As shown inFig.3c,incontrasttoGFthatcontainssolelygraphit-icN(originatingfromthepolyacrylonitrileprecursorused for the preparation of GF),Bi/N-GF exhibitsthreeN1speaksattributabletographiticN(401.0eV),pyrrolicN(399.6eV),andpyridinicN(398.3eV),resultingfromthePDAdopant.ThesurfaceatomiccontentofNinBi/N-GFwasestimatedtobeabout2.6%.ThepercentageofpyridinicNishigherthanthatofpyrrolicN.ThisisbeneficialsincepyridinicNdopingoffersloneelectronpairs,whichfavorthead-sorption of the positively charged cadmium ions topromotetheredoxreactionofCr3+/Cr2+20.Twoprom-inentpeakscenteredat162.5and157.0eVwereob-servedforBi4fXPSspectrum,whichcorrespondtothe4f2/5and4f2/7peaksofBi0(Fig.3d),suggestingtheformationofmetallicBi.WeusedCVtoexplorethereactivityofGF,N-GF,Bi-GF,andBi/N-GFfortheredoxreactionsofFe2+/Fe3+andCr3+/Cr2+.Theobtainedelectrochemicalparameters were listed in Table S1.It can be seenfromFig.4a,thattwopeaksofFe2+/Fe3+redoxpairswere found in all samples.Compared with GF,thepeakredox current of Bi/N-GF is significantly en-hanced.Theoxidationpeakcurrentdensities(Ipa)of170165160155Bi 4fBi4f7/2 Bi0Intensity/(a.u.)Binding energy/eVBi4f5/2 Bi0Bi/N-GF204060Intensity/(a.u.)2/()Bi/N-GFGFC PDF#26-1080N 1sGraphitic NPyrrolic NPyridinic NBi/N-GF404402400398396Graphitic NGFBinding energy/eVIntensity/(a.u.)12009006003000Binding energy/eVBi/N-GFGFO 1sN 1sC 1sBi 4fIntensity/(a.u.)(a)(b)(c)(d)Fig.3(a)XRDpatternsofGFandBi/N-GF.(b)Wide-surveyand(c)N1sXPSspectraofGFandBi/N-GF.(d)Bi4fXPSspectrumofBi/N-GF第1期CHEHang-xinetal:BismuthnanoparticlesanchoredonN-dopedgraphitefeltstogivestableand1350.00