Operando identification of synergistic dynamic for cobalt-tungsten-based bimetallic electrocatalysts in oxygen evolution reaction

Abstract

The bimetallic electrocatalysts in oxygen evolution reaction (OER) have been the subject of numerous investigations. However, due to their heterogeneous nature, understanding the individual roles and reaction mechanisms of the catalytic sites remains challenging. Herein, we present an electrocatalyst system featuring a cobalt-tungsten (Co/W)-based bimetallic pair. In this bimetallic series, the catalytic activity displays a trend, with the overpotential of 385 mV at 10 mAcm−2 and the lowest Tafel slope of 70 mVdec−1 under alkaline conditions for the OER. Operando characterization reveals the Co site functions as the active site, undergoing a CoIII/CoIV redox cycle, while the W site also exhibits a simultaneous redox cycle, acting as a driving force to trigger the OER process. We propose a catalytic cycle that demonstrates the synergistic effect of hetero-atoms, in which they follow a similar O–O bond-forming step to metal oxides under OER conditions yet exhibit distinct rate-determining steps. Our research contributes to the understanding of bimetallic electrocatalysts as promising systems for fundamental studies and improved OER performance.