Manipulating Metal Cations Microenvironment for Highly Selective Electrochemical Water Oxidation to Hydrogen Peroxide

Abstract

Electrochemical two-electron water oxidation (2e^– WOR) represents a promising approach for the renewable and on-site production of H₂O₂, potentially replacing the anthraquinone process. Nevertheless, it faces intense competition from the conventional four-electron oxygen evolution reaction (OER), resulting in low selectivity, high overpotential, and low yield. Herein, taking carbon-based structures with 2e^– WOR selectivity as model catalysts, by manipulating the electrolyte, it increased the maximum Faraday efficiency of H₂O₂ to 71 ± 3%, with an H₂O₂ production rate of 11.7 μmol cm^–2 min^–1. The 2e^– WOR activity was found to be most sensitive to alkali metal cations in the following order: Cs⁺ > K⁺ > Na⁺ > Li⁺. In situ spectroscopy characterization confirmed that larger cations facilitate the generation of peroxide species; this is because, on one hand, cations can regulate the electronic activity of the catalyst sites and improve the adsorption of the reaction intermediates; on the other hand, the cation-hydrogen oxygen interaction regulates the stable coordination of the cation, realizes the reforming of the hydrogen bond network, and prevents its further water oxidation into O₂. With the help of a flow electro-synthetic cell, we can successfully achieve the rapid degradation of organic pollutants in water and the preparation of solid H₂O₂ (sodium peroxycarbonate). This work not only enriches the understanding of cationic and 2e^– WOR mechanisms but also provides implications for rational optimization strategies of the electrode/electrolyte interface.