荞麦芯衍生的富氮和富氧可控多孔碳用于高性能超级电容器

时间：TIME\@"yyyy'年'M'月'd'日'"2022年3月29日学海无涯页码：第1-页共1页荞麦芯衍生的富氮和富氧可控多孔碳用于高性能超级电容器1Introduction

Withtheimprovementoftherequirementsofthelivingenvironmentandtherapiddevelopmentofeconomy,peoplehaveproblemsinthestorageandutilizationofenergy.Withthelarge-scaledevelopmentandutilizationofnewenergy,theexistingenergystorageequipmenthasbeenunabletomeetthedemandforenergysourcestorage.Supercapacitor(SC),apotentialenergystoragedevice,hasattractedmuchattentiononaccountofitsadvantages(suchasfastchargepropagationdynamics,highpowerdensityandlongcyclelife)whichmayreplacecommercialbatteries[1-2].Generallyspeaking,supercapacitorsincludeelectricdoublelayercapacitors(EDLCs)andpseudocapacitors(PCs),consideringthedifferentenergystoragemechanisms[3-4].Theformermainlygeneratesstoredenergythroughtheadsorptionofpureelectrostaticchargesontheelectrodesurface.PCstoresenergythroughrapidsurfaceredoxreactions[5].Thestructureandcharacteristicsofelectrodematerialsdeterminethechargestoragemechanismofsupercapacitors,whichdeterminestheelectrochemicalperformanceofsupercapacitors[6-8].

Inthelastfewyears,numerousstudieshavebeencarriedoutbyresearchersonthedevelopmentofelectrodematerials,whichcommonlyincludecarbonmaterials,conductingpolymersandmetaloxides[9-13].Althoughmetaloxideshavehighspecificcapacitanceandredoxactivity,theyarenotpracticalbecauseoftheirhighcost(suchasRuO2,MnO2andCo3O4)[14-16].Conductivepolymers,suchasPANIandPPY,generallystoreandreleasechargethroughreversibledopingandde-dopingprocessesonthematerialsurface,andtheexpansionandcontractionproducedinthisprocessmaydamagetheelectrodestructure[17-18].Uptonow,carbonhasbeentheonlyelectrodematerialemployedincommercialSCsowningtoitslargesurfacearea,goodprocessabilityandphysicochemicalstability[19],mainlyincludingCNTs,activatedcarbonandgraphene[20-22].Electric-doublelayercapacitance(EDLC)energystorageofcarbonmaterialscouldaccumulateandseparateelectrostaticchargesattheelectrode/electrolyteinterface,yieldingthehighspecificcapacitance[23].Recently,alotofattentionhasbeenpaidtoporouscarbonmaterialsforEDLCbehavior[24-26].Theporestructuresplaydifferentrolesinimprovingcapacitanceperformances.Parameterssuchasspecificsurfacearea(SSA)andporestructuredeterminetheelectrochemicalperformanceofcarbonelectrodes,andalargeSSAisnotnecessarilyfavorablefortheircapacitiveperformance.Therefore,itisnecessarytofindanextensibleapproachtopreparehighavailablesurfaceareacarbonmaterialswithreasonableporestructure.

Porouscarbon,attributedtoitslargeSSAandinterconnectedcellnetwork,isconsideredtobeanelectrodematerialwithhighperformanceSCs[27-29].Wastebiomassisregardedasoneofthepromisingprecursorsforthefabricationofactivatedcarbonfromtheperspectiveofrawmaterialavailabilityandlowcost.Currently,thereportedbiomasscarbonmaterialsusedaselectrodematerialsforSCsincludebuleberrypeel[30],puffballspores[31],tofu[32],pinenutshells[33]andshiitakemushroom[34],miscanthuswaste[35],methylcellulose[36],etc.Buckwheatisanabundantresourcewithworldbuckwheatproductionexceedingonemilliontons.Comparedwiththeotherbiomass,buckwheathasbeenwidelyemployedasahealthcareproductsuchasbuckwheattea,andseldomappliedinotherfieldsespeciallyforenergy.Itsmainproteinsandcarbohydratesareglobulin(70%)andstarch(10%),respectively,andcontainstraceelementsanddietaryfiber[37-38].Theabundantstarchisbeneficialinthehightemperaturecarbonizationprocesstoobtainarichcarbonstructure,andadegreeofproteincontentisbeneficialintheestablishmentofaN-dopedstructureinthecarbonmatrix[39-40].Wedemonstratealow-cost,green,simpleandeasilyscalableapproachtofabricateporouscarbonsusingbuckwheatcoreasrawmaterial.

Hence,wepreparedporouscarbon(BCPC-3)withhighavailablesurfaceareaandreasonableporestructureusingbuckwheatcorepowderasprecursorbyactivationofKOHat800℃.Weinvestigatedthecapacitanceoftheacquiredsamples,likewisetheeffectsoftheKOHactivationratioandthenitrogen/oxygencontent.ThepreparedcarbonmaterialsalsodisplayedtunableshapeandporestructureduetothedifferentKOHratios.This3Dhierarchicallyporousstructureconsistedofvariousdiametersofpores,whichmayenhancetheelectrochemicalperformanceoftheactivematerial.Inparticular,thepresenceofagreatnumberofmicroporesstrengthenstheelectric-double-layercapacitance.Additionally,N-5,N-6andphenol-Ocouldenhancethewettability.Overall,BCPC-3showedahighcapacitance(330F/gat0.5A/g)andexcellentrateperformance(140F/gat100A/g)inathree-electrodesystemwith6mol/LKOHaselectrolyte.Besides,thesymmetrialsupercapacitorbasedontheBCPC-3sampledeliversalargeenergydensityof6.1W·h/kgatapowerdensityof250W/kgin6mol/LKOHelectrolyte.

2Experimental

2.1Samplefabrication

BCPC-x(xisthemassratioofKOHtobuckwheatcore)wasobtainedbychemicalactivationofthebuckwheatcoreforpreparation.ThemixtureofBuckwheatcoreandKOH(mBuckwheatcore/mKOH=1:1/1:3/1:5)wasallowedtostandfor24hatroomtemperatureandthencompletelydriedinablastdryerandmovedtoahigh-temperaturetubefurnaceraisedto800℃(5℃/min)andkeepinArfor1h.Theblackpowderwasobtainedinordertoremovepotassiumcompoundsandotherimpuritiessoakedin2mol/LHNO3for24handwashedseveraltimeswithdistilledwater,followedbyapHtestpapertomeasurethepHvalueofthefiltratearound7.Finally,theblackpastewasdriedat70°CandnamedasBCPC-x.Thefinalyieldsofthecarbonmaterialswere1.35%,1.18%and0.94%respectively.Asacomparison,thesampleswerecalcinedat700°CandnamedasBCPC700°C-x.ThepreparationoftheBCPC-xisshowninScheme1.

Scheme1SchematicofthesynthesisstepsfortheBCPC-x

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2.2Characterizationofmaterials

TheporouscarbonpreparedwastestedbyX-raydiffraction(XRD)(BrukerD8Advance).RamanandinfraredspectrumwereoperatedbyLabRAMHR800(France)andNICOLET5700FTIRspectrometer,respectively.TheN2adsorptionanddesorptiontestswereconductedbyAutosorbIQ(USA).ElementvalancewasstudiedbytheX-rayphotoelectronspectroscopy(XPS)(KratosXSAM800).Themorphologicalstructuresofthesamplesatdifferentnanometersizeswerestudiedbyscanningelectronmicroscopy(SEM)(HitachiS4800)andtransmissionelectronmicroscopy(TEM)(TecnaiG220).Thermogravimetry(TG)wasoperatedbyTGAQ500inargonatmosphere.

2.3Electrochemicaltests

2.3.1Three-electrodemeasurement

Toestimatetheelectrochemicalcapabilitiesoftheporouscarbonobtainedfrombuckwheat,fourmainmethodsareusedforelectrochemicaltesting:constantcurrentcharge/discharge,cyclicvoltammetry,ACimpedance,andcharge/dischargecyclicstabilityof5000cycles.BlackpastewasobtainedbymixingactivesubstanceBCPC-x,acetyleneblack,andPVDFintheconventionalratioof80:10:10,addingappropriatenitromethylpyrrolidoneasthesolvent,andthenevenlycoatedoncarboncloth(area:1cm×1cm;thickness:0.33mm).Itwasmaintainedat60℃undervacuumandtheworkingelectrodewasobtained.Here,theworkingelectrodemasswasabout2mg.Thedevicesweretestedin6mol/LKOHaqueouselectrolytes,theHg/HgOelectrodeactedasreferenceelectrodeandthegraphitesheetwasusedascounterelectrode.

Dependingtothedischargetime,thespecificcapacities(C,F/g)werecalculatedby:

C=IΔtΔVma

(1)

Intheaboveequation,I(A),C(F/g),Δt(s),ma(g),ΔV(V)representthedischargecurrent,specificcapacitance,dischargetime,activemassandpotentialwindow,respectively.

2.3.2Two-electrodemeasurement

Acoin-shapedsymmetricsupercapacitorwasassembledusingtheelectrodespreparedabove,wheretheseparatorisaglassfiber(Whatman)andtheelectrolyteis6mol/LKOH.Thespecificcapacitanceofaunitaryelectrodeofcarbonmaterialiscomputedasfollows:

C=IΔtΔVmT

(2)

wheremT(g)representsthetotalmassofactivematerialsinbothelectrodes.TheenergydensityandpowerdensityofSCwereobtainedbyEqs.(3)and(4),respectively:

E=0.5C(ΔV)23.6

(3)

P=3600EΔt

(4)

Intheaboveformulas,E(W·h/kg),C(F/g),ΔV(V),P(W/kg)andΔt(s)representtheenergydensity,specificcapacitance,potentialwindow,powerdensityanddischargetime,respectively.

3Resultsanddiscussion

3.1Physicochemicalcharacterization

ThegatheredsampleswerecharacterizedbyXRDandthepatternsareshowninFigure1(a).Thethreesetsofsamplesexhibitedtwotypicalwidepeaksatnearly22°and43°,representing(002)and(100)planesofthehexagonalgraphite,respectively[41].

Figure1(a)XRDpatterns,(b)Ramanspectra,(c)N2adsorption/desorptionisotherms,and(d)poresizedistributionoftheBCPC-1,BCPC-3andBCPC-5samples

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Theinterlayerdistance(002)ofgraphiticlayersofcarbonisestimated0.39-0.42nmfollowingtheBraggequation,

2dsinθ=λ

(5)

LaandLcaretheaveragetransverselengthandthicknessofthegraphitesegment,respectively.FollowingthetheScherrerEq.(6),

La/c=Kλβcosθ

(6)

Amongthem,βandKdenotethediffractionpeakhalf-heightwidthandScherrerconstant,respectively[42].Ramanspectra(Figure1(b))deliveredtwopeakslocatingat1345cm-1(Dband)and1590cm-1(Gband),relatedtodisorderfeatureandgraphiticdegree[30].WegenerallyconsiderthattheintensityratioofG-bandtoD-band(IG/ID)reflectedthecrystallinityofcarbon[27].Asaresult,thevalueofBCPC-3(1.04)washigherthanthatofBCPC-1(0.95)andBCPC-5(1.01),whichimpliedthatthegraphitizationofBCPC-3washigherthantheothertwogroups.ThetexturalpropertiesofthethreetypesofBCPC-xwerefurtheranalyzedusingtheN2adsorption/desorptionanalysis.ThisclearlydemonstratesthecharacteristicsofthemicroporesseeninFigure1(c),wherealltheisothermscanbeclassifiedtotypeIVabsorptionisotherms[43].Figure1(d)showstheporesizedistributionsofallsamples.Numerousmicropores(mainlyrangefrom0.2to2nm)canbeobservedinBCPC-xafterKOHactivation(insetinFigure1(d)).InTable1,theSSAofthecarbonsincreaseswiththeKOHratio.Notably,BCPC-3exhibitedthelargestmesoporousandtotalporevolume,whichareconsideredasbeneficialforthediffusionoftheions.Microporosityofthethreesampleswas85%,41%and71%,respectively.Previousreportsindicatethatexcessiveultra-microporesarenotbeneficialforchargestorage[44].ThisisbecauseinaqueousKOHsolutions,theK+andOH-ionsinvolvedintheconductivityhaveadiameterofabout0.3nm,anditisdifficultforK+andOH-toquicklyentersomeultramicroporouspores(0.55nm)duetothepresenceofionicsolventlayersandtheirregularityofthepores[45].Consequently,BCPC-3,withthehighSSAandreasonableporesizegradient,wasdesirabletoexhibitoutstandingelectrochemicalperformanceintermsofrateandcapacitanceaspects.

Table1SBET,Vt,VmicandIG/IDfortheBCPC-1,BCPC-3,andBCPC-5samples

SampleD002/nmLc/nmLa/nmSBET/(m2·g-1)Vt/(cm3·g-1)Vmic/(cm3·g-1)IG/ID

BCPC-10.412.334.82799.890.410.350.95

BCPC-30.391.573.25805.910.600.251.04

BCPC-50.422.214.57923.940.530.381.01

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Toinvestigatethemicroscopicmorphologyofthematerials,scanningelectronmicroscopy(SEM)characterizationwasconducted.Firstly,whentheratioofbuckwheatcorepowdertoKOHis1:1,thematerialcontainsasignificantnumberofmesoporesandmacropores(seeFigure2(a)).Astheratioincreasesto1:3,theBCPC-3formedamorerationalporousfoam-likeinterconnectedcarbonskeleton(seeFigure2(b)).SubsequentfurtheretchingofBCPC-5resultedthecrashofthemicro-structureandgeneratedabulkyamountofmaterialdebris(Figure2(c)),whichindicatedthedisruptionoftheinterconnectedstructure.Energyelementalmapping(Figures2(d)-(g))obviouslydisplayedthattheelementsofC,OandNweredistributedhomogeneouslyintheBCPC-3.Theelementseffectivelyincreasethecapacitanceandratecapabilityoftheactivematerialinthecharging/dischargingprocedures[46].ThedetailedstructuralcharacterizationofBCPC-3wasfurtherrevealedbytypicaltransmissionelectronmicroscopy(TEM).Simultaneously,inFigure2(h),wefoundmyriadshinyandshadowypatchesuniformlydispersedinBCPC-3,whicharemicroporousstructuresinthecarbonmaterialfromthepyrolysisoforganiccomponentsandtheactivationofKOH.Besides,thelatticefringespacingmeasuredinFigure2(j)isalsoconsistentwiththecalculationofXRDpatterns.ThisresultmaybeascribedtothecombinationofthelowcarbonationtemperatureandKOHactivationandfurtherleadstoanincreasedgraphitizationofthematerial,butnotafullyformedgraphiticstructure.ThepreparedcarbonmaterialsalsodisplayedtunableshapeandporestructureduetothedifferentKOHratios.This3Dhierarchicallyporousstructureconsistedofvariousdiametersofpores,whichmayenhancetheelectrochemicalperformanceoftheactivematerial.Inparticular,thepresenceofagreatnumberofmicroporesstrengthenstheelectric-double-layercapacitance[28].Further,thethermaldecompositionprocessofbuckwheatcorepowderinargonatmospherewasanalyzedbyTGA.Itismainlycomposedofstarchandprotein,andthecarbonationprocessismainlyattributedtothepyrolysisofthesecompounds.TheTGAcurvesinFigureS1showasignificantmasslossinthetemperatureinterval250℃-500℃.Thedecompositionofthesepolymersduringcarbonizationleadstothegasvolatilizationandtheinterconnectedporousstructure(micropores,mesoporesandmacropores).

Figure2SEMimagesof(a)BCPC-1,(b)BCPC-3and(c)BCPC-5,(d-g)elementalmappingand(h-j)HRTEMgraphicsfortheBCPC-3

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Inordertostudytheelementalcompositionincarbonmaterials,Figure3presentstheXPSspectraofBCPC-3.ThefullXPSspectrumofthesampleseeninFigure3(a)around284,532and399eVexhibitthreepeakscorrespondingtoC(85.5%),O(14%),andN(0.5%)elements.ThepropertyindicatesthatNinthesampleisself-doped,whichoriginatesfromtheN-containingcompoundsinthebuckwheatcore.InFigure3(b),itisshownthattheC1speakconsistedoffourpeakslocatedat284.6,285.9,287.4and289.3eV,correspondingtoC—C,C—O,C=OandCOOHgroups,respectively.AsshowninFigure3(c),O1sspectracouldbedeconvolutedintotwosinglepeaksasphenol-O(532.3eV)andcarboxyl-O(533.7eV).Additionally,aspresentedinFigure3(d),N1srevealedtwopeaksat398.8(pyrrolic-NabbreviatedtoN-5)and400.6eV(pyridinic-NabbreviatedtoN-6)[28].SinceN-5hassuperiorelectrondonationcapabilityandrapidchargeflux,andN-6possesseselectronpairingwithπ-conjugatedrings.[47].Itisreportedthatpyrrolic-N/phenol-O/carboxyl-Ospeciescanserveasactivepseudocapacitivespeciestofurtherprovideadditionalpseudocapacitanceinalkalineelectrolyte[48-49].Moreover,theresultantsamplewasquitehydrophilic,whichwillfacilitateiondiffusionandmaximizetheeffectiveion-accessiblesurfacearea.Importantly,N-5,N-6andphenol-Ocouldenhancethewettability[50].Insummary,thepresenceoftheseC,NandOfunctionalgroupsplaysanessentialpartinenhancingtheelectrochemicalpropertiesofthematerial.Oneoftheoxygen-containingfunctionalgroupscanefficientlyincreasethedefectsanddisorderinthecarbonstructure,andthismatcheswiththeresultsdisplayedbyXRDandRamanspectroscopy.Moreover,thecomponentsofBCPC-xwerefirstlyestimatedbyEA(analyticfunctionaltesting).Threechemicalelementsofcarbon,nitrogenandhydrogencanbedetectedfromTableS1.InFigureS2,FTIRpatternsoftheBCPC-1,BCPC-3andBCPC-5samplespresentedthreepeakssurroundedat3440,1630and1090cm-1belongingtotheO—H,N-6orN-5groups,andaromaticether(C—O)stretchingvibrations,respectively[51].

Figure3FullXPSspectraofBCPC-3samples(a)andXPStestofC(b),O(c)andN(d)

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3.2Electrochemicalevaluation

Theelectrochemicalbehaviorsofthesampleswerefurtherresearchedinthree-electrodesystem.FigureS3showedtheCVplotsofdifferentBCPC-xfrom-1to0Vat50mV/s.Amongthem,BCPC-3enclosesahigherareathanBCPC-1andBCPC-5.Itcanbeobservedthattherearenoobviousredoxpeaksforthethreecurves.ExcellentsymmetryimpliedgoodEDLCbehaviorandfavorablestabilityofthematerials.BCPC-1,BCPC-3andBCPC-5electrodesweretestedfrom5to100mV/s(Figures4(a),(c)and(e)).TheCVcurvesofBCPC-1,BCPC-3andBCPC-5stilldisplayedanear-rectangleshapeevenatscanratesof100mV/s,whichindicatedthedesirableratecapabilityandfastiontransferability.TheGCDprofilesofBCPC-1,BCPC-3andBCPC-5at0.5-100A/garepresentedinFigures4(b),(d)and(f).Thegalvanostaticchargedischange(GCD)curvesshowednosignificantIRdropandallexhibitedastandardsymmetricshape,provingthegoodreversibilityofthethreesamplesatalowequivalentseriesresistance.Furthermore,astheKOHratioincreased,thespecificcapacitanceat0.5A/gwas226,330and196F/gforthethreesetsofcarbonscalculatedaccordingtoEq.(1),respectively.Comparedwiththeothertwogroupsofsamples,thedischargetimeofBCPC-3waslongeratequalcurrentdensities,implyingthatBCPC-3hadahigherspecificcapacitance,whichcoincidedwiththeCVcurves.KOHwasusedfortheactivationofprecursorandthereactionmechanismisgivenasfollows[52]:

4KOH+C→K2CO3+K2O+2H2

(7)

K2CO3+2C→2K+3CO

(8)

K2O+C→2K+CO

(9)

Figure4Electrochemicalperformanceofthesamplestestedinathree-electrodesystemusing6mol/LKOHelectrolyte:CVcurvesofBCPC-1(a),BCPC-3(c)andBCPC-5(e)atthescanratefrom5to100mV/s;GCDcurvesofBCPC-1(b),BCPC-3(d)andBCPC-5(f)at0.5-100A/g

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Accordingtothesechemicalreactions,theamountofKOHiscriticaltotheprocessofactivationandtheresultantwell-developedporousstructure.Duringthepore-formingprocess,KOHcancreateporesbyreactingwithcarbon,andpotassiumisgenerated.Whenthetemperatureexceedstheboilingpointofpotassium(762℃),itwillexistinthegaseousformandbeextremelyreactive.Subsequently,potassiumwillunfoldthearomaticlayerandcreatemoreinternalporesandinterconnectedchannels[53].AstheamountofKOHemployedintheproductionofsampleBCPC-1isratherlow,theinsufficientetchingofcarbonframeworkmayresultinanunevenporesizedistribution.ThehigherKOHratioofBCPC-5resultedinthecollapseofmicrostructuredpores.Inaddition,FaradayreactionprocessrelatedtoabundantN,Odopingcouldgiverisetopseudocapacitanceeffect.Amongthem,thepseudocapacitancecontributionofBCPC-3canbeattributedtomoreavailableexposednumerousdefectsitesandN,OfunctionalgroupsespeciallytheeffectiveN-5andN-6speciesunderhighspecificsurfacearea[54].Aspredictedabove,thesuperiorcapacitanceperformanceofBCPC-3materialsmainlyoriginsfromhighspecificsurfaceareawithfavorablestructuredistributionsynergizedwithabundantoxygendopingandN-6andN-5dominatedNdoping.

Toinvestigatetheratepropertydeeply,Figure5(a)showedthecapacitanceversusdischargecurrentdensityforallsamples.ItisclearthatBCPC-3hasahighercapacitance(0.5-100A/g),whichrepresentsafavorableratecapabilityofBCPC-3.ItisworthnotingthattheBCPC-3stilldeliversacapacitanceof140F/gatahighrateof100A/g.Meanwhile,theGCDcurvesandratepropertiesofthethreegroupsofmaterialsat700℃areshowninFigureS4.BCPC700℃-1,BCPC700℃-3andBCPC700℃-5haverelativelylowcapacitanceandcomparablerateperformance.Thelowcapacitivebehaviorisduetotheunderdevelopedporestructureandincompletesurfacechemistrycausedbythelowtemperature.Inaddition,theareacapacitance(Ca)andvolumetriccapacitance(Cv)arecalculatedbythefollowingequationsrespectively[55-56].

Ca=SC

(10)

Cv=ρpC

(11)

Figure5(a)GravimetricspecificcapacitanceoftheBCPC-1,BCPC-3andBCPC-5atvariousrates(0.5,1,5,10,20,50,100A/g);(b)EIScurvesoftheBCPC-1,BCPC-3andBCPC-5

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whereSstandsforthemassloadingofasingleelectrode(2mg/cm2).ρp=1Vp+1/ρcarbon,whereVpistheporevolumeofthecarbonparticleswhichcanbedeterminedbynitrogenphysisorption(0.6cm3/g)andρcarbonisthetruedensityofthecarbonthatcanbemeasuredbyheliumpycnometryandisusuallyaround2g/cm3.AsshowninFigureS5,theareacapacitanceandvolumetriccapacitanceofBCPC-3at0.5A/gwere660mF/cm2and300mF/cm3,respectively.WespeculatethatthismaybeduetotheproperKOHratioandtemperatureresultinginatunableporosity.Meanwhile,thisreasonableporestructurecanactasareservoirforaqueouselectrolytestopromotetransportofions[57].BCPC-3exhibitsahigherspecificcapacitancecomparingtotheexistingbiomass-basedcarbonmaterialsreportedinrecentyears.Forinstance,porouscarbonobtainedbyone-stepcarbonizingbiomasscashewnuthusk(305.2F/gat1A/g)[43],camelliapetals(227F/gat0.5A/g)[58],N-dopedporouscarbonderivedbyhydrothermalcarbonizationofmacroalgae(228F/gat0.1A/g)[59],anovelzirconia-basedcarbonnanofiber(referredtoasCNF-20ZrO2)fabricatedusingasimpleelectrospinningmethod(140F/gat1A/g)[60],NaOH-activatedpeanutshells(199F/gat0.5A/g)[61].ThisfurtherprovesthatBCPC-3exhibitsthesupremecapacitance.

Furthermore,inFigure5(b),theelectrochemicalimpedancespectrum(EIS)ofBCPC-1,BCPC-3andBCPC-5isperformed(0.01Hz-100kHz).Nyquistplotcontainedasemicircleinthehigh-frequencyregionandanobliquestraightlineinthelow-frequencyregion.Theinterceptofthesemicircleandthehorizontalaxisinthehigh-frequencyregionrepresentstheintrinsicresistance(Rs)oftheelectrode,includingtheresistanceofthematerial,theresistanceoftheelectrolyte,andtheresistancebetweentheelectrolyteandthecollector.Bysimulatingandcalculatingtheequivalentcircuitmodel(insetillustration),theelectrodeintrinsicresistanceofBCPC-1,BCPC-3andBCPC-5is0.85Ω,0.74Ωand0.76Ω,respectively.ItdemonstratesthatareasonableKOHratioandthesurfacechemistryofthenitrogen-oxygenfunctionalgroupreducestheself-resistanceofthematerial.Atthesametime,thediameterofthesemicircleinthemid-lowfrequencyregionrepresentsthechargetransferresistancebetweenthematerialandtheelectrolyte,whichisrelatedtotheRctintheequivalentcircuitmodel.TheRctvaluesofBCPC-1,BCPC-3andBCPC-5is0.91Ω,0.27Ωand0.41Ω,respectively.Th