Tuning Two-Electron Oxygen-Reduction Pathways for H 2 O 2 Electrosynthesis via Engineering Atomically Dispersed Single Metal Site Catalysts.

The hydrogen peroxide (H 2 O 2 ) 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 H 2 and O 2 . It enables on-site and decentralized H 2 O 2 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 H 2 O 2 production via the 2e - ORR. Herein, recent methodologies and achievements on developing single metal site catalysts for selective O 2 to H 2 O 2 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 H 2 O 2 and the derived free radicals, catalyst stability and effective solutions to improve catalyst tolerance to H 2 O 2 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.