Mathieu Mougenot

Cluster organization in co-sputtered platinum-carbon films as revealed by grazing incidence X-ray scattering

Nanostructured platinum-carbon thin films were prepared by magnetron co-sputtering method for designing efficient catalytic thin films, like fuel cells electrodes. The in-depth morphology of composite films was studied using surface sensitive X-ray techniques (grazing incidence small-angle scattering and reflectivity), consolidated by electron microscopy investigations. This study elucidates the growth mode of co-sputtered platinum-carbon thin film: 2-nm-sized platinum clusters are growing in surrounding simultaneously growing carbon columns (20-nm diameter range). In particular, the platinum cluster growth and distribution in the plane of the substrate surface are driven by surface diffusion and coalescence phenomena. Finally, this anisotropic distribution of platinum clusters correlated to the textured morphology of carbon matrix leads to a catalytic thin film morphology very suitable for electrochemical processes in fuel cell electrodes.

High Performance Plasma Sputtered Fuel Cell Electrodes with Ultra Low catalytic metal Loadings

Ultra-low Pt content PEMFC electrodes have been manufactured using magnetron co-sputtering of carbon and platinum on a commercial E-Tek_ uncatalyzed gas diffusion layer in plasma fuel cell deposition devices. Pt loadings lower than 0.01 mg cm-2 have been realized. The Pt catalyst is dispersed as small clusters with size less than 2 nm over a depth of 500 nm. PEMFC test with symmetric electrodes loaded with 0.01 mg cm-2 led to maximum reproducible power densities as high as 0.4 Wcm-2 with Nafion 212. Replacement of platinum was also realized by preparing MEAs composed of 0.01 mgPd cm-2 for the anode and 0.01 mgPd cm-2 + 0.001 mgPt cm-2 for the cathode and Nafion 212 membrane. Power density as high as 250 mW cm-2 were achieved at 80°C, which corresponds to a specific power density of 250 kW gPt-1