关键词: 传质, 多孔介质, 燃料电池, 阴极催化层, 低Pt载量, 局部氧传质阻力

Abstract:

The oxygen mass transfer resistance in the cathode catalyst layer of proton exchange membrane fuel cell (PEMFC) is the main bottleneck limiting the polarization performance of membrane electrode with low Pt at high current densities. To reduce the oxygen mass transfer resistance of the cathode catalyst layers is of highly significance for the improvement of PEMFC performance and accelerating its commercial applications. In the paper, the sources and contributions of oxygen mass transfer resistance in catalyst layers have been analyzed. It is pointed out that the local oxygen mass transfer resistance is primarily caused by the resistance across the three-phase contact interface among the gas phase, ionomer, and Pt nanoparticles. The influences on the oxygen mass transfer resistance, especially the local one have been expounded from four aspects of Pt nanoparticle, ionomer, carbon support and the water formed, respectively. The methods of reducing oxygen mass transfer resistance have also been summarized. Finally, the design of cathode catalyst layers with low Pt for PEMFC is prospected. It is proposed that constructing suitable support pore structure, rationalizing the Pt particle distributions both inside and outside of the pores, controlling ionomer thickness and its distribution, as well as strengthening water transfer, could help to reduce the oxygen mass transfer resistance and thus to promote the cell power outputs at high current densities.

Key words: mass transfer, porous media, fuel cells, cathode catalyst layer, low Pt loading, local oxygen mass transfer resistance