Bias-Free Photoelectrochemical H<sub>2</sub>O<sub>2</sub> Production and Its <i>In Situ</i> Applications
Myohwa Ko, June Sung Lim, Ji‐Wook Jang, Sang Hoon Joo
Abstract
Hydrogen peroxide (H 2 O 2 ) is a valuable chemical that has been used in a wide range of applications. Currently, H 2 O 2 production relies predominantly on the anthraquinone process, which is energy-intensive and non-ecofriendly. The photoelectrochemical two-electron O 2 reduction reaction (2e – ORR) and 2e – water oxidation reaction (2e – WOR) have recently emerged as promising alternatives to produce H 2 O 2 in a bias-free, cost-effective, and environmentally benign manner. In this Perspective, we overview photoelectrochemical routes to H 2 O 2 production and its in situ application for valuable chemical synthesis. We discuss the design principles needed for achieving a bias-free photoelectrochemical H 2 O 2 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 H 2 O 2 synthesis cells. Further, we present the application of photoelectrochemically produced H 2 O 2 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 H 2 O 2, and practical viability.