Performance of thin-film cathodes for proton-exchange-membrane fuel cells based on high-surface-area carbon supports

New commercial catalysts materials from Johnson Matthey were tested in thin-film electrodes (cathodes) in PEMFCs. These catalysts are nano-sized Pt particles on a novel high-surface-area carbon support. It was found that in thin-film electrodes made from the new catalyst material a much higher specific electrochemically active surface area could be achieved than in electrodes made from conventional 40 wt% Pt/Vulcan XC-72. This was due to both smaller particle sizes and a better utilisation, and also resulted in a higher mass activity. The optimum Nafion content was found to be 20 wt%. The thickness of electrodes was reduced, resulting in a lower proton resistance. This reduced the transport losses in the electrode, as is also illustrated by modelling results.