Membrane electrode assemblies (MEAs) with various catalyst-loading were made using a standard 46.5%Pt/KB (TEC10E50E) with the aim of developing low Pt-loading PEFCs. Since increase in concentration overvoltage for low catalyst-loading MEAs was observed, the mechanism of such increase in concentration overvoltage was considered, and then reducing concentration overvoltage was tried through two methods, by adding extra carbon and using a more hydrophobic carbon support, graphitized Ketjen black, within the cathode layer (CL). As a result, we have experimentally proven that increase in hydrophobicity of CL can promote water drain and reduce the concentration overvoltage for low catalyst-loading MEAs, and hydrophobicity is an important factor to be controlled within CL in addition to porosity.
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