Tuning Two-Electron Oxygen-Reduction Pathways for H₂O₂ Electrosynthesis via Engineering Atomically Dispersed Single Metal Site Catalysts

The hydrogen peroxide (H₂O₂) generation via the electrochemical oxygen reduction reaction (ORR) under ambient conditions is emerging as an alternative and green strategy to the traditional energy-intensive anthraquinone process and unsafe direct synthesis using H₂ and O₂. It enables on-site and decentralized H₂O₂ production using air and renewable electricity for various applications. Currently, atomically dispersed single metal site catalysts have emerged as the most promising platinum group metal (PGM)-free electrocatalysts for the ORR. Further tuning their central metal sites, coordination environments, and local structures can be highly active and selective for H₂O₂ production via the 2e⁻ ORR. Herein, recent methodologies and achievements on developing single metal site catalysts for selective O₂ to H₂O₂ reduction are summarized. Combined with theoretical computation and advanced characterization, a structure–property correlation to guide rational catalyst design with a favorable 2e⁻ ORR process is aimed to provide. Due to the oxidative nature of H₂O₂ and the derived free radicals, catalyst stability and effective solutions to improve catalyst tolerance to H₂O₂ are emphasized. Transferring intrinsic catalyst properties to electrode performance for viable applications always remains a grand challenge. The key performance metrics and knowledge during the electrolyzer development are, therefore, highlighted.