Enhanced oxygen reduction reaction performance over Pd catalysts by oxygen-surface-modified SiC

Abstract

Obtaining a detailed understanding of the surface modification of supports is crucial; however, it is a challenging task for the development and large-scale fabrication of supported electrocatalysts that can be used as alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR). In this study, commercial silicon carbide (SiC) was modified through surface oxidization (O-SiC) to support the use of Pd nanoparticles (Pd NPs) as electrocatalysts for ORR. The obtained Pd/O-SiC catalysts exhibited better ORR activity, stronger durability, and higher resistance to methanol poisoning than that exhibited by commercial Pt/C. The role of the support in enhancing the ORR performance, especially the oxidization of SiC surfaces, was discussed in detail based on the experimental characterizations and density functional theory calculations. The underlying mechanism of the superior ORR performance of Pd/O-SiC catalysts was attributed to the charge transfer from SiCxOy to Pd NPs on the surfaces of SiC and the strong metal–support interactions (SMSIs) between Pd and SiCxOy. The charge transfer enhanced the ORR activity by inducing electron-rich Pd, increased the adsorption of the key intermediate OOH, and decreased the Gibbs free energy of the critical ORR step. Furthermore, SMSIs enhanced the ORR stability of the Pd/O-SiC catalyst. This study provided a facile route for designing and developing highly active Pd-based ORR electrocatalysts.