Identification of the Highly Active Co-N4 Coordination Motif for Selective Oxygen Reduction to Hydrogen Peroxide

Electrosynthesis of hydrogen peroxide (H2O2) through oxygen reduction reaction (ORR) is an environment-friendly and sustainable route for obtaining a fundamental product in the chemical industry. Co-N4 single-atom catalysts (SAC) have sparkled attention for being highly active in both 2e- ORR, leading to H2O2 and 4e- ORR, in which H2O is the main product. However, there is still a lack of fundamental insights into the structure-function relationship between CoN4 and the ORR mechanism over this family of catalysts. Here, by combining theoretical simulation and experiments, we unveil that pyrrole-type CoN4 (Co-N SACDp) is mainly responsible for the 2e- ORR, while pyridine-type CoN4 catalyzes the 4e- ORR. Indeed, Co-N SACDp exhibits a remarkable H2O2 selectivity of 94% and a superb H2O2 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 SACDp-with weakening O-2/HOO* interaction-boosts the H2O2 production.

Automated summary

The research reveals that pyrrole-type CoN4 and pyridine-type CoN4 are responsible for 2e- ORR and 4e- ORR reactions, respectively. Pyrrole-type CoN4 catalyst exhibits excellent H2O2 selectivity and yield in acid media. This study is significant for understanding the structure-function relationship of Co-N4 single-atom catalysts and improving H2O2 production.