Abstract
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.