Effects of Heat Treatment on the Catalytic Activity and Methanol Tolerance of Carbon-Supported Platinum Alloys

This work studies the effect of heat treatment of carbon-dispersed platinum and platinum alloys on its methanol tolerance and catalytic activity as gas diffusion electrodes for oxygen reduction reaction (ORR) in acid medium. The catalyst powders were subjected to heat treatments at three different temperatures for a fixed period at controlled atmospheres. Differences in catalyst morphology were characterized using X-ray diffraction, energy dispersive X-ray analysis, and transmission electron microscope techniques. The electrochemical characteristics and activity of the electrocatalysts were evaluated for ORR and methanol tolerance using cyclic voltammetry in the form of gas diffusion electrodes. The optimum heat treatment temperature is found to be strongly dependent on the individual catalyst. The maximum ORR activity and better methanol tolerance for ORR was observed in Pt-Fe/C and Pt-Cu/C catalysts subjected to heat treatment at 350 °C. A trend of catalytic activity for ORR was obtained: Pt-Cu/C (350 °C) > Pt-Fe/C (350 °C) > Pt-Ni/C (350 °C) > Pt-Co/C (250 °C) > Pt/C (350 °C), showing that Pt-Cu/C-type catalysts had a higher catalytic activity with reasonable methanol tolerance.