Electrochemically generated electrophilic peroxo species accelerates alkaline evolution reaction

Abstract

Introducing a new redox cycle into (electro)catalysts can activate reactants, enabling novel functionality. Here, we report that early transition metals (TMs) with vacant d orbitals (d0-oxoanions) directly participate in and accelerate the alkaline oxygen evolution reaction (OER) via a redox cycle associated with early TM-peroxo species [M(O2)2-]. Interestingly, the metal-peroxo cycles both induced by hydrogen peroxide (H2O2) and OER intermediates have similar characteristics, making it possible to modulate the OER performance using d0-oxoanions that react with H2O2 as enhancers. This principle was successfully integrated into practical electrolysis systems with the anode side extended to typical OER catalysts. Among them, tungstate-modified iron-nickel (oxy)hydroxide (W/FeNiOOH) exhibited current densities of 7.87 and 4.26 A cmgeo-2 at 2.0 Vcell in water electrolysis while running in 1.0 M KOH and 1.0 wt % K2CO3 electrolyte, respectively. Our finding provides universal platforms demonstrating a controllable strategy toward electrochemical oxygen activation using the electrophilic peroxo cycle.