Oxygen electroreduction on carbon-supported platinum catalysts. Particle-size effect on the tolerance to methanol competition
Résumé
The kinetics of oxygen reduction in methanol-containing acid electrolyte was investigated at platinum-based electrodes using the porous rotating disk electrodes (RDE) technique. Utilization of commercial-grade (E-TEK) carbon-supported Pt particles with narrow size distribution provided evidences for a particle size effect on the tolerance of oxygen reduction electrocatalysts to methanol competition. In methanol-containing perchloric acid electrolyte, the mass activity (MA, A g−1 Pt) for oxygen reduction increases continuously with a decrease in particle size from d=4.6 to 2.3 nm, whereas in methanol-free electrolyte MA is roughly independent of the size, when d≤3.5 nm. Effects of addition of a second metal to Pt were also investigated. Based on particle size considerations Pt:Cr–C appears to be a more active catalyst than Pt–C for oxygen reduction in methanol-containing electrolyte.