Engineering of Single-Atomic Sites for Electro- and Photo-Catalytic H₂O₂ Production

Direct electro- and photo-synthesis of H₂O₂ through the 2e^- O₂ reduction reaction (ORR) and H₂O oxidation reaction (WOR) offer promising alternatives for on-demand and on-site production of this chemical. Exploring robust and selective active sites is crucial for enhancing H₂O₂ production through these pathways. Single-atom catalysts (SACs), featuring isolated active sites on supports, possess attractive properties for promoting catalysis and unraveling catalytic mechanisms. This review first systematically summarizes significant advancements in atomic engineering of both metal and nonmetal single-atom sites for electro- and photo-catalytic 2e^- ORR to H₂O₂, as well as the dynamic behaviors of active sites during catalytic processes. Next, the progress of single-atom sites in H₂O₂ production through 2e^- WOR is overviewed. The effects of the local physicochemical environments on the electronic structures and catalytic behaviors of isolated sites, along with the atomic catalytic mechanism involved in these H₂O₂ production pathways, are discussed in detail. This work also discusses the recent applications of H₂O₂ in advanced chemical transformations. Finally, a perspective on the development of single-atom catalysis is highlighted, aiming to provide insights into future research on SACs for electro- and photo-synthesis of H₂O₂ and other advanced catalytic applications.