Electrocatalytic Activity of Different Phases of Molybdenum Carbide/Carbon and Platinum–Molybdenum Carbide/Carbon Composites toward the Oxygen Reduction Reaction

Abstract

AbstractIn the last few years, transition metal carbides have emerged as novel materials with promising catalytic properties toward important practical reactions. In this work, cubic and hexagonal molybdenum carbides are synthesized and evaluated as carbon‐supported catalysts and as support materials for Pt nanoparticles for the electrochemical oxygen reduction reaction (ORR). The catalysts are characterized by XRD, energy‐dispersive X‐ray spectroscopy, TEM, XPS, and cyclic voltammetry on stationary and rotating ring‐disk electrodes. The results suggest different reactivity of the molybdenum carbide phases as both catalysts and supports for the ORR. Enhanced mass and specific ORR activities at 0.9 V are calculated for Pt–molybdenum carbide‐derived composites compared to commercial Pt and Pt/C catalysts prepared by depositing Pt by the same method. The origin of the improved ORR activity is discussed in terms of the synergistic effect between Pt and the carbide‐derived support and a decrease in the adsorption strength of oxygen‐containing species on the Pt surface, similar to that proposed for Pt–metal alloys. Additionally, the possible formation of a Pt–Mo alloy on the catalyst surface is proposed.