Improvement of the utilization efficiency of Pt by improving the mass diffusion is key especially for carbon nanotube (CNT)-based electrocatalyst layers (CL) of polymer electrolyte membrane fuel cells (PEMFC). Here, we introduced hydrophobic spherical polytetrafluoroethylene (PTFE) particles into the CNT-based CL for the first time to improve the diffusion of oxygen and water. Catalyst-coated gas diffusion layers (CCG) were prepared by vacuum filtration method and membrane electrode assembles were prepared by hot pressing of CCGs with Nafion membrane. By incorporating PTFE particles specifically into the cathode CL, a large increase of power density was obtained mainly due to the improvement of hydrophobicity. Addition of the PTFE was effective especially during low humidity operations. Since the filtration process is simple and useful especially for CNT-based electrocatalysts, our findings are quite beneficial to realize CNT-based PEMFC, which is promising especially for the next generation PEMFCs operated under high-temperature and low humidity.

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The effect of surface roughness of the catalyst layer (CL) based on carbon-nanotube (CNTs) in contact with polymer electrolyte membrane (PEM) in polymer electrolyte membrane fuel cell (PEMFC) was studied....

The effect of surface roughness of the catalyst layer (CL) based on carbon-nanotube (CNTs) in contact with polymer electrolyte membrane (PEM) in polymer electrolyte membrane fuel cell (PEMFC) was studied. The surface roughness of vacuum-filtrated CL sheets were evaluated using laser microscope and the surface of CL sheet contacting the filter membrane was found to be smoother compared to the surface exposed to the air. When a smoother surface of the CL sheet was laminated with PEM to fabricate membrane-electrode-assembly (MEA), power density of the single cell was 604.6 mW cm-2 at 80 °C under 100%R.H., which was greater than the MEA having a rougher CL surface (542.4 mW cm-2).