Photoelectrochemical water oxidation for on-site production of hydrogen peroxide

Photoelectrochemical (PEC) two-electron water-oxidation reaction is a promising route for renewable and on-site generation of H2O2 as an alternative to the traditional anthraquinone process. However, large overpotential, low product selectivity, and poor stability limit its practical applications of PEC producing H2O2. This review discusses the fundamental aspects of two-electron water oxidation toward H2O2 in a simple PEC device. It also presents the research background and all prevailing and recent breakthrough in the mechanisms of anodic H2O2 generation. Afterward, it comprehensively reviews the progress made so far in enhancing the Faradaic efficiency of H2O2 synthesis by tuning the thermodynamic energy barriers and reaction kinetics, facilitating the mass transfer of reactants and products, and stabilizing the products and catalytic surfaces. Finally, the critical challenges and opportunities for future development in this field are discussed. We believe that this review would stimulate further efforts to achieve highly efficient on-site H2O2 production and high-power-density fuel cells with H2O2 chemical utilization.