Photochemical reactions of g-C3N4-based heterostructured composites in Rhodamine B degradation under visible light

Abstract

Highly efficient visible-light-driven Ag₂O/g-C₃N₄, Ag/g-C₃N₄, and BiOBr/g-C₃N₄ heterostructured photocatalysts were prepared by solution synthesis methods at room temperature. Compared with Ag/g-C₃N₄ (1 : 30 mass ratio) and Ag₂O/g-C₃N₄ (2 : 1 mass ratio) photocatalysts, the BiOBr/g-C₃N₄ composite (1 : 3) displayed enhanced photocatalytic activities for Rhodamine B (RhB) degradation under visible-light irradiation. The reaction kinetics of phenol RhB dye photodegradation of Ag₂O/g-C₃N₄ (1 : 1, 2 : 1, 4 : 1 mass ratios) and BiOBr/g-C₃N₄ were fitted with the pseudo-first-order model, ln(C₀/C) = kt, while the data of Ag/g-C₃N₄ and pure g-C₃N₄, Ag₂O/g-C₃N₄ (1 : 20 mass ratio) were fitted with the zero-order model. The former has enhanced photocatalytic activity, and BiOBr/g-C₃N₄ composites exhibit the highest degrading rate for RhB. The enhanced photocatalytic activity of two dimensional BiOBr/g-C₃N₄ photocatalysts was mainly attributed to the formation of type II p–n heterojunctions, as well as the well-matched band gap and the synergetic effects between two components, which accelerate the separation efficiency of photogenerated electrons–holes at the interface. Finally, possible photocatalytic and charge separation mechanisms of Ag₂O/g-C₃N₄ and BiOBr/g-C₃N₄ composites were proposed via active species capture experiments.