Identification of the Highly Active Co-N 4 Coordination Motif for Selective Oxygen Reduction to Hydrogen Peroxide.

Electrosynthesis of hydrogen peroxide (H 2 O 2 ) through oxygen reduction reaction (ORR) is an environment-friendly and sustainable route for obtaining a fundamental product in the chemical industry. Co-N 4 single-atom catalysts (SAC) have sparkled attention for being highly active in both 2e - ORR, leading to H 2 O 2 and 4e - ORR, in which H 2 O is the main product. However, there is still a lack of fundamental insights into the structure-function relationship between CoN 4 and the ORR mechanism over this family of catalysts. Here, by combining theoretical simulation and experiments, we unveil that pyrrole-type CoN 4 (Co-N SAC Dp ) is mainly responsible for the 2e - ORR, while pyridine-type CoN 4 catalyzes the 4e - ORR. Indeed, Co-N SAC Dp exhibits a remarkable H 2 O 2 selectivity of 94% and a superb H 2 O 2 yield of 2032 mg for 90 h in a flow cell, outperforming most reported catalysts in acid media. Theoretical analysis and experimental investigations confirm that Co-N SAC Dp ─with weakening O 2 /HOO* interaction─boosts the H 2 O 2 production.