One of the majorissuesli mitingtheintroduction of polymer electrolyte membranefuel cells(PEMFCs) is thelowtemperature ofoperation which makes platinum-based anode catalysts susceptible to poisoning by the trace amount...One of the majorissuesli mitingtheintroduction of polymer electrolyte membranefuel cells(PEMFCs) is thelowtemperature ofoperation which makes platinum-based anode catalysts susceptible to poisoning by the trace amount of CO,inevitably present in reformedfuel.In order to alleviate the problemof COpoisoning andi mprove the power density of the cell,operating at temperature above 100 ℃ispreferred.Nafion-type perfluorosulfonated polymers have been typically used for PEMFC.However,the conductivity of Nafion-typepolymers is not high enoughto be usedfor fuel cell operations at higher temperature(>90 ℃) and atmospheric pressure because they dehy-drate under these condition.An additional problem which faces the introduction of PEMFCtechnology is that of supplying or storing hydrogen for cell operation,especially for vehicular applications.Consequently the use of alternative fuels such as methanol and ethanol is of interest,especially if thiscan be used directlyinthe fuel cell,without reformationto hydrogen.Ali mitation of the direct use of alcohol is thelower activity of oxida-tionin comparison to hydrogen,which means that power densities are considerably lower.Hence to i mprove activity and power outputhigher temperatures of operation are preferable.To achieve this goal,requires a newpolymer electrolyte membrane which exhibits stabilityand high conductivityin the absence of liquid water.Experi mental data on a polybenzi midazole based PEMFC were presented.Asi mple steady-stateisothermal model of the fuel cell is alsoused to aidin fuel cell performance opti misation.The governing equations involve the coupling of kinetic,ohmic and mass transport.Thispaper also considers the advances madeinthe performance of direct methanol and solid polymer electrolyte fuel cells and considers theirli mi-tations in relation to the source and type of fuels to be used.展开更多
文摘One of the majorissuesli mitingtheintroduction of polymer electrolyte membranefuel cells(PEMFCs) is thelowtemperature ofoperation which makes platinum-based anode catalysts susceptible to poisoning by the trace amount of CO,inevitably present in reformedfuel.In order to alleviate the problemof COpoisoning andi mprove the power density of the cell,operating at temperature above 100 ℃ispreferred.Nafion-type perfluorosulfonated polymers have been typically used for PEMFC.However,the conductivity of Nafion-typepolymers is not high enoughto be usedfor fuel cell operations at higher temperature(>90 ℃) and atmospheric pressure because they dehy-drate under these condition.An additional problem which faces the introduction of PEMFCtechnology is that of supplying or storing hydrogen for cell operation,especially for vehicular applications.Consequently the use of alternative fuels such as methanol and ethanol is of interest,especially if thiscan be used directlyinthe fuel cell,without reformationto hydrogen.Ali mitation of the direct use of alcohol is thelower activity of oxida-tionin comparison to hydrogen,which means that power densities are considerably lower.Hence to i mprove activity and power outputhigher temperatures of operation are preferable.To achieve this goal,requires a newpolymer electrolyte membrane which exhibits stabilityand high conductivityin the absence of liquid water.Experi mental data on a polybenzi midazole based PEMFC were presented.Asi mple steady-stateisothermal model of the fuel cell is alsoused to aidin fuel cell performance opti misation.The governing equations involve the coupling of kinetic,ohmic and mass transport.Thispaper also considers the advances madeinthe performance of direct methanol and solid polymer electrolyte fuel cells and considers theirli mi-tations in relation to the source and type of fuels to be used.
