A catalyst superior to carbon-supported-platinum for promotion of the oxygen reduction reaction: reduced-polyoxometalate supported palladium

Abstract

The high solubility of polyoxometalates (POMs) in basic electrolytes limits their practical applications. Fortunately, we found that this shortcoming can be overcome by electrochemically reducing the POMs. The reduced POMs (rPOM) are extremely stable in alkaline solutions and can participate in electrocatalytic cycles. Herein, we present a novel rPOM as a Pd-catalyst-substrate to achieve a high catalytic performance towards the oxygen reduction reaction (ORR). Interestingly, although rPOM alone has very low catalytic activity, the Pd/rPOM hybrid catalyst exhibits excellent electrocatalytic performance for ORR in alkaline media, even better than the commercial Pt/C catalyst. The much improved ORR activity of Pd/rPOM is based on electron delocalization between the Pd and the rPOM support, causing a down-shift in the d-band structure of the Pd NPs. Furthermore, the rPOM in the Pd–rPOM hybrid serves as an assistant catalyst, facilitating the decomposition of the harmful hydrogen peroxide intermediates. The method reported here will promote broader interest in the further development of other new catalysts for real-world applications.