Superior photocatalytic hydrogen peroxide production over g-C3N4 with Ni(OH)2 as an oxidation cocatalyst

Abstract

Loading cocatalysts is an effective strategy to boost the photocatalytic performance of semiconductor photocatalysts. In this work, a novel Ni(OH)₂/graphitic carbon nitride (g-C₃N₄) composite photocatalyst (NiCN) was successfully fabricated by a facile deposition process for hydrogen peroxide (H₂O₂) production. In the composite, Ni(OH)₂ serves mainly as an oxidation cocatalyst to efficiently capture photogenerated holes (h⁺), thereby improving the separation efficiency of photo-induced charge carriers. As a result, the NiCN composite displays remarkably enhanced catalytic performance. Among them, the optimized NiCN-30 achieves the highest H₂O₂ yield of 1189.8 μM within 1 h (5949.0 μmol g⁻¹ h⁻¹), which is 2.70 times higher than that of pristine g-C₃N₄. The superior activity of NiCN-30 is attributed to its greatly improved charge separation efficiency and favorable band structure compared with pure g-C₃N₄. Mechanistic studies confirm that ˙O₂⁻ is the dominant reactive intermediate, and the photocatalytic H₂O₂ generation over NiCN follows a two-step oxygen reduction reaction (ORR) pathway.