Abstract
Electrochemical water oxidation enables the conversion of H(2)O to H(2)O(2). It holds distinct advantages to the O(2) reduction reaction, which is restricted by the inefficient mass transfer and limited solubility of O(2) in aqueous media. Nonetheless, most reported anodes suffer from high overpotentials (usually >1000 mV) and low selectivity. Electrolysis at high overpotentials often causes serious decomposition of peroxides and leads to declined selectivity. Herein, we report a ZnGa(2)O(4) anode with dual active sites to improve the selectivity and resist the decomposition of peroxides. Its faradaic efficiency reaches 82% at 2.3 V versus RHE for H(2)O(2) generation through both direct (via OH(-)) and indirect (via HCO(3)(-)) pathways. The percarbonate is the critical species generated through the conversion of bicarbonate at Ga-Ga dual sites. The peroxy bond is stable on the surface of the ZnGa(2)O(4) anode, significantly improving faradaic efficiency.