Hydrogen peroxide electrosynthesis via two-electron oxygen reduction: From pH effect to device engineering

Abstract

As a versatile and environmentally benign oxidant, hydrogen peroxide (H₂O₂) is highly desired in sanitation, disinfection, environmental remediation, and the chemical industry. Compared with the conventional anthraquinone process, the electrosynthesis of H₂O₂ through the two-electron oxygen reduction reaction (2e⁻ ORR) is an efficient, competitive, and promising avenue. Electrocatalysts and devices are two core factors in 2e⁻ ORR, but the design principles of catalysts for different pH conditions and the development trends of relevant synthesis devices remain unclear. To this end, this review adopts a multiscale perspective to summarize recent advancements in the design principles, catalytic mechanisms, and application prospects of 2e⁻ ORR catalysts, with a particular focus on the influence of pH conditions, aiming at providing guidance for the selective design of advanced 2e⁻ ORR catalysts for highly-efficient H₂O₂ production. Moreover, in response to diverse on-site application demands, we elaborate on the evolution of H₂O₂ electrosynthesis devices, from rotating ring-disk electrodes and H-type cells to diverse flow-type cells. We elaborate on their characteristics and shortcomings, which can be beneficial for their further upgrades and customized applications. These insights may inspire the rational design of innovative catalysts and devices with high performance and wide serviceability for large-scale implementations.