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

Neutral electrosynthesis of H₂O₂via 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–CN content and reduces the C–C/CC 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 Ni_0.10 SA/CNNS with optimal N–CN content exhibited the best selectivity (∼98%) and highest yield of H₂O₂ (∼503 mmol g_cat⁻¹ h⁻¹), which is ∼14.6 times higher than that of CNNS (∼34.4 mmol g_cat⁻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.