Surface properties of Pt and PtCo electro-catalysts and their influence on the performance and degradation of high temperature polymer electrolyte fuel cells

摘要

An investigation of the behaviour of carbon-supported Pt and PtCo cathode electro- catalysts was carried out to evaluate their performance and resistance to degradation. Nanosized Pt and PtCo catalysts with similar crystallite size (2.7-2.9 nm) were prepared by using a colloidal route. The surface properties were investigated by X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectroscopy (LE-ISS). The formation of a Pt skin layer on the surface of the alloy electro-catalyst was obtained by using a pre- leaching procedure. As result, a significant surface Pt enrichment was observed for the leached Pt-Co electrocatalyst. This characteristic appeared to influence catalysts' performance and degradation. Accelerated tests (electrochemical cycling) at 130 °C in a pressurised PEMFC showed a better stability for the PtCo alloy as compared to Pt. Furthermore, better performance was obtained at high temperatures for the pre-leached PtCo/C as compared to the Pt/C cathode catalyst.