Bias-Free Photoelectrochemical H2O2 Production and Its In Situ Applications

Hydrogen peroxide (H2O2) is a valuable chemical that has been used in a wide range of applications. Currently, H2O2 production relies predominantly on the anthraquinone process, which is energy-intensive and non-ecofriendly. The photoelectrochemical two-electron O2 reduction reaction (2e- ORR) and 2e- water oxidation reaction (2e- WOR) have recently emerged as promising alternatives to produce H2O2 in a bias-free, costeffective, and environmentally benign manner. In this Perspective, we overview photoelectrochemical routes to H2O2 production and its in situ application for valuable chemical synthesis. We discuss the design principles needed for achieving a bias-free photo electrochemical H2O2 synthesis and introduce the concept of single and dual constructions, with notable examples of each one. We benchmark the solar-to-chemical conversion efficiencies of photoelectrochemical H2O2 synthesis cells. Further, we present the application of photoelectrochemically produced H2O2 for in situ green chemical synthesis. Finally, we provide future perspectives on this emerging field, discussing its main limitations and targets for further development, including high performance, stability of produced H2O2, and practical viability.