Abstract
Cathode catalysts for PEMFC applications typically consist of platinum supported on carbon, with Pt weight percent usually 5-50%. While the Pt weight percent is known to affect performance and durability, the mechanisms behind these effects are poorly understood. We systematically investigated the effect of Pt weight percent using commercial Pt loaded on high surface area carbon (HSC) catalysts supplied by Tanaka. At the same Pt loading, the mass ratio between the Pt nanoparticles and carbon support will determine the thickness of the catalyst layer as well as the local Pt content. After durability testing, changes in ECSA, ORR mass activity, and performance in Hz/air indicate that degradation increases with increasing local Pt content, while average Pt content appears less important. CO stripping at different relative humidity shows that, despite substantial ECSA loss, there is little change in the distribution of Pt between the interior and exterior of carbon particles.