The presented research is focused on Pt-C composite catalysts for proton exchange membrane fuel cell (PEMFC) applications. Nanostructured Pt-C thin films (thickness 25-150 nm, Fig 1d) were deposited on carbon paper gas diffusion layer (Sigracet 29 BC) substrates by magnetron sputtering method. Total Pt loading in the thin films varied in the range 5.5-30 µg/cm²as determined by XPS. These catalysts were examined for their activity in hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR).

A fuel cell with a membrane electrode assembly (MEA) based on Nafion 212 membrane with our Pt-C anode (Pt loading 5.5-30 µg/cm²) and a commercial state-of-the-art Pt/C cathode (Pt loading 300µg/cm²) generated output power up to 1.0 W/cm² (Fig 1a), value comparable to MEA with commercial powder anode using much higher Pt loading 200-300 µg/cm². This result demonstrates significant improvement in platinum utilization for HOR due to high dispersion of Pt provided by the magnetron sputtering deposition method. Similarly, a MEA with the commercial Pt/C cathode and our Pt/C thin film (Pt loading 5.5-30 µg/cm²) as anode yielded stable power up to 0.73W/cm²(Fig 1 b), proving its high efficiency for ORR.

Based on the above findings, a MEA with both magnetron sputtered Pt/C electrodes using total Pt loading 20 µg/cm² was tested with a 4 cm² cell operating at 70˚C in H₂/O₂-feed regime for 24 hours. The platinum content on cathode and anode side was chosen 14.4 µg/cm² and 5.5 µg/cm², providing highest efficiency for HOR and ORR, respectively. I-V polarization and power density curves were measured with fresh catalyst as well after a 24-hour duration test without any significant lost of efficiency during this period of time (Fig 1c). The magnetron sputtered Pt-C with fine metal dispersion proved to be a promising catalytic material with high Pt utilization for hydrogen-feed PEMFC applications. An additional significant benefit of the Pt-C composite is its lower requirement with respect to feed humidity.