Transition metal single atom-optimized g-C₃N₄ for the highly selective electrosynthesis of H₂O₂ under neutral electrolytes

Neutral electrosynthesis of H2O2 via the 2e(_) ORR is attractive for numerous applications, but the low activity and high cost of electrocatalysts have become important constraints. Therefore, the development of cheap and efficient electrocatalysts for the 2e(_) ORR is necessary. Herein, we report the embedding of transition metal single atoms (TM SAs) in g-C3N4 nanosheets (CNNS). The introduction of TM SAs increases the N-CQN content and reduces the C-C/CQC content in CNNS, which contributes to the increased selectivity of TM SA/CNNS for the 2e(_) ORR. TM SA is the main reason for the enhanced activity of the 2e(_) ORR. Based on the results obtained by replacing a series of TM SA, the Ni0.10 SA/CNNS with optimal N-CQN content exhibited the best selectivity (similar to 98%) and highest yield of H2O2 (similar to 503 mmol gcat(-1) h(-1)), which is similar to 14.6 times higher than that of CNNS (similar to 34.4 mmol gcat(-1) h(-1)). Other TM SA/CNNS also exhibited high activity and selectivity. This study demonstrates the ability of TM SA to modulate the selectivity and activity of CNNS, making it a promising candidate for the 2e(_) ORR and providing more reference ideas for the preparation of H2O2.