Study on direct methanol fuel cell performance modification based on foam carbon diffusion layer
Diffusion layer(DL)is an essential structure of a direct methanol fuel cell(DMFC)membrane electrode assembly(MEA),which provides a channel for the mass transfer of reactants from the flow field to the catalytic layer.As the reaction proceeds,the DL also provides a channel for the transport of electrons from the catalytic layer to the flow field.Therefore,the conductivity and surface morphology of the DL affects the overall performance of the fuel cell.The cathode diffusion layer(CDL)based on the foam carbon(FC)material could reduce the contact,charge transfer,and mass transfer resistance between the fuel cell membrane electrode and the current collector plate thanks to the FC's electrical conductivity and three-dimensional network structure.Moreover,the high porosity and small surface contact angle(CA)of FC could also increase the proportion of DMFC cathode catalytic layer exposed to the air and provide extra gas-liquid two-phase channels,which is the better catalyst support.Experimental results show that compared with the DMFC based on traditional carbon paper(CP-DMFC),the maximum power density of the DMFC with FC as the CDL(FC-DMFC)increases from 24.47 mW/cm2 to 39.24 mW/cm2,the contact resistance decreases from 0.588 Ω to 0.494 Ω,the charge transfer resistance decreases from 2.784Ω to 1.816 Ω,and the mass transfer impedance decreased from 1.689 Ω to 1.417 Ω.Under a discharging current of 100 mA/cm2,the discharge time of FC-DMFC is 60 min,while the discharge time of CP-DMFC is 46 min,and FC as a diffusion layer has a longer discharge time.It shows that the new structure has higher energy efficiency under the same methanol concentration and volume than the conventional structure.
fuel celldiffusion layerfoamy carbontwo-phase flowpower density
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