Engineering Nonprecious Metal Oxides Electrocatalysts for Two-Electron Water Oxidation to H₂O₂

Hydrogen peroxide (H2O2) is a valuable chemical oxidant which has been extensively applied in water treatment, textile/paper bleaching, medical disinfection, and other industrial fields. Electrocatalytic two-electron water oxidation reaction (2e-WOR) with renewable energy inputs is an attractive route to produce H2O2, which avoids the energy-intensive anthraquinone process in industry. However, leveraging these advances requires the development of efficient and selective electrocatalysts to accelerate the sluggish kinetics. In particular, nanostructured engineering of nonprecious metal oxides offers a promising route for 2e-WOR. In this review, the recent progress on nanostructure engineering of various nonprecious metal oxides electrocatalysts for 2e-WOR is reviewed, along with remarks on the challenges and perspectives. The fundamental understanding of 2e-WOR by density functional theory calculations and operando characterizations is first given, followed by a discussion of diverse H2O2 quantification methods including ultraviolet-visible spectrophotometry, titration, and colorimetric strips, with special emphasis on their accuracy, detection limit and stability. Afterward, various strategies toward high-performance nonprecious metal oxides electrocatalysts including doping, defect, facet, and interface engineering are overviewed. Future challenges and opportunities for 2e-WOR to H2O2 are proposed finally.