Graphitic carbon nitride–BiVO4 heterojunctions: simple hydrothermal synthesis and high photocatalytic performances

Abstract

Graphitic carbon nitride (C₃N₄)–BiVO₄ heterojunctions with various mass ratios of C₃N₄ and BiVO₄ were synthesized by a simple hydrothermal method. High-resolution transmission electron microscopy (HR-TEM) results show that an interface of intimate contact is formed between C₃N₄ and BiVO₄ in heterojunctions. The UV-vis diffuse reflection spectra reveal that the resulting C₃N₄–BiVO₄ heterojunctions exhibit more intensive absorption within the visible light range in comparison with pure C₃N₄. The photocatalytic tests demonstrate that the resulting C₃N₄–BiVO₄ heterojunctions possess significantly enhanced photocatalytic activities for methylene blue (MB) degradation under visible light irradiation compared with individual C₃N₄ and BiVO₄. The optimum photocatalytic activity of the 0.7 C₃N₄–0.3 BiVO₄ heterojunction is almost 3.5 and 2.8 times higher than those of individual C₃N₄ and BiVO₄, respectively. On the basis of experimental result, a possible photocatalytic mechanism that has superoxide radical species as the mainly active species in photocatalysis is proposed. Additionally, the present study provides a useful strategy to design heterojunction materials with enhanced photocatalytic performance.