第六课燃料电池基础-高等工程热力学课件.ppt

1、)(RT-)expexp(A00,cathodicffEEFRTGk23FeFee)(RT)-(1)expexp(A00,anodicbbEEFRTGksurfaceFebulkFebulkFesurfaceFe2233CCCC0i0EE AFiCkCkvsurfaceFebsurfaceFefnet23)exp(A)exp(A0,anodicb0,cathodicf0bfRTGRTGkkk)(exp-00fEEFkk)()-exp(100bEEFkkAFiCkCkvsurfaceRbsurfaceOfnetReO 对于任何一个单电子转移的还原反应对于任何一个单电子转移的还原反应)()1 (e

2、xp)(exp0surfaceR0surfaceO0EERTFCEERTFCAFki0)()1 (exp)(exp0eqSurfaceR0eqsurfaceO0EERTFCEERTFCAFkiSurfaceRSurfaceO0eq)(expCCEERTF)ln()ln(surfaceRSurfaceO0surfaceOSurfaceR0eqCCFRTECCFRTEEB-V方程回归到能斯特方程方程回归到能斯特方程i=0,电化学反应净反应速率为电化学反应净反应速率为0, 不代表正和逆反应各自速率为不代表正和逆反应各自速率为00)()1 (exp)(exp0eqSurfaceR0eqsurfaceO

3、0EERTFCEERTFCAFki00eqSurfaceR00eqsurfaceO0)()1 (exp)(expiEERTFCAFkEERTFCAFk交换电流交换电流, mA cm-2BulkR1BulkO0SurfaceR1SurfaceO00CCAFkCCAFki BulkR1BulkO0SurfaceRBulkR1BulkO0SurfaceO0)()1 (exp)(expCCEERTFCCCEERTFCiiSurface: 电极表面浓度Bulk：反应物本体浓度)1(BulkRBulkO0BulkRSurfaceRBulkRBulkO0BulkOSurfaceO0)()1 (exp)(ex

4、pCCEERTFCCCCEERTFCCiiBulkRBulkOSurfaceRSurfaceO0eq)(expCCCCEERTF)(exp0eqBulkRBulkOEERTFCC)()1 (exp0eq)1(BulkRBulkOEERTFCC)()1 (exp)(expeqBulkRSurfaceReqBulkOSurfaceO0EERTFCCEERTFCCii）准状态下（电流为电极标准可逆电势，标）准状态下（电流为电极可逆电势，但非标时）电极实际电势（有电流0:0:0eqEEE定义定义: : 电极实际电势与非准态时的可逆电势的差值，称为过电势，电极实际电势与非准态时的可逆电势的差值，称为过电

5、势， (overpotential),(overpotential),这种行为就叫做极化这种行为就叫做极化(polarization(polarization）eqEE )1 (expexpBulkRSurfaceRBulkOsurfaceO0RTFCCRTFCCii电流电流- -过电势关系式过电势关系式0eqEE)1 (expexpBulkRSurfaceRBulkOsurfaceO0RTFCCRTFCCii1050.58.314303)exp(expBulkOsurfaceO0BulkOsurfaceO0RTFCCiRTFCCii电池电流与电极电势损失的关系式电池电流与电极电势损失的关系式

6、Turbine or IC engineO2FuelHeatCO2CombustionNOx, SOxParticulatesMechanical energyElectric generatorElectric current?能源问题能源问题?大气环境大气环境?城市污染城市污染水水H2交通运输交通运输住宅住宅 商业商业工业工业电能电能水水可再可再生能生能源源能量能量载体载体能源消耗部门能源消耗部门fossil fuelsoxygenfossilfuelreservescombustionwater2water2化石燃料化石燃料氧气氧气可用能源可用能源燃烧燃烧water污染污染水水化石化石燃

7、料燃料储藏储藏二氧化碳二氧化碳环境环境hydrogenwaterwateroxygenoxygenenvironment可用能源可用能源hydrogenutilizationhydrogenproduction氢气氢气水水水水氧气氧气氧气氧气环境环境用氢用氢产氢产氢产电产电renewableenergysources电力电力可再生可再生能源能源环境环境DC electricitDC electricityWaterWaterHeatHeatO2H H22FUEL CELLFUEL CELLCathodeAnode“Fuel”H2 Plus H2OAir (O2)+21-+阴极催化层阴极催化层阴

8、极扩散层阴极扩散层质子交换膜质子交换膜阳极催化层阳极催化层阳极扩散层阳极扩散层e2H2H2OHe2H2O5 . 022质子交换膜质子交换膜电子通道电子通道阴极流场阴极流场阳极流场阳极流场电池放电电流的限制因素电池放电电流的限制因素任何化学反应任何化学反应燃料电池反应燃料电池反应e2H2H2OHe2H2O5 . 022质子交换膜质子交换膜电子通道电子通道透射电镜照片透射电镜照片碳载纳米催化剂碳载纳米催化剂The bringingtogether of these three things is a veryimportant issue in fuel cell design850 m 化学反应

9、能量与化学反应能量与H H2 2-PEMFC-PEMFC电电压压222Of,Hf,OHf,r5 . 0 GGGGg)or O(lH(g)O5 . 0(g)H222STGrprFGzFGE2rrr121211-TTTTT效率Hr-fuel of moleper producedenergy electrical效率%100rrHG最大效率FGzFGE2rrrO(g)H(g)O5 . 0(g)H222OH0.5OH0222ln2FRTEE0OH5 . 00O0H0222ln2ppppppFRTEE 热力学理论电压热力学理论电压 PEMFC 大于大于 SOFC 实际运行电压实际运行电压 SOFC 大

10、于大于 PEMFC 提高电池高温降低了电压损失或者说各种提高电池高温降低了电压损失或者说各种 不可逆损失不可逆损失iFRTiFRTEElnln0eq0actln|iiFRTV00actln2ln|iiFRTiizFRTV0actlogiiaV0actlniiAV0actln2iiFRTV0actln2iiFRTVact02expVRTFiiact0actact02exp )1 (exp2expVRTFiVRTFVRTFii0ractrcelllniiAEVEVcathode0,canode0,aactlnlniiAiiAVbiAVlnactbaAAAAAc0,AAa0,caiib2c0,2a0

11、,cm mA1 . 0;cm mA200iiC800cm mA10C;70cm mA1 . 02c0,2c0,ii0rlniiAEV20rcm mA 04. 0;06. 0;2 . 1iVAVElimitcon1lniiBV)RR(RcontactionomerelectronicOhmiciV电池运行中的各种损失电池运行中的各种损失ConOhmicActrCellVVVEV)(UI VIPower loss Ohmicloss voltage Reaction0micThermodynaCellCellCellnutilizatioFuelFaradayVoltage0micThermodynaCellCellinput fuel of HtVI EfficiencyObjective: Increasing Vcell at a given ICellTransport of reactant& productTriple phase area Catalyst activityReaction kinetics ion conductione- conductionInterfacial contactInternal resistance