Recent Advances in Electrochemical Water Oxidation to Produce Hydrogen Peroxide: A Mechanistic Perspective

Abstract

<p>Electrochemical production of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) has recently gained traction as a green alternative to the unsustainable anthraquinone auto-oxidation process and the high-risk direct synthesis route. While the two-electron oxygen reduction reaction (2<i>e</i><sup>-</sup> ORR) toward H<sub>2</sub>O<sub>2</sub> has been covered extensively in the literature, the unorthodox two-electron water oxidation reaction (2<i>e</i><sup>-</sup> WOR) remains far less popular, due to the thermodynamic unfavorability of the pathway. Nonetheless, the 2<i>e</i><sup>-</sup> WOR constitutes a coveted procedure as it enables the electro-generation of H<sub>2</sub>O<sub>2</sub> solely from water. A thorough understanding of the reaction mechanism, including all intermediates and competing reaction routes, is essential for the fabrication of electrocatalysts, and assembly of electrochemical reactors, capable of greater H<sub>2</sub>O<sub>2</sub> production rates with an optimal efficiency. This review focuses exclusively on the 2<i>e</i><sup>-</sup> WOR to electrochemically produce H<sub>2</sub>O<sub>2</sub>. A summary of all prevailing water oxidation mechanisms is presented, supported with computational and experimental data, and key challenges and limitations that require attention are addressed.</p>