New Understanding on Enhanced Photocatalytic Activity of g-C₃N₄/BiPO₄ Heterojunctions by Effective Interfacial Coupling

Although g-C3N4/BiPO4 heterojunctions have shown high photocatalytic performance experimentally, understanding is far from satisfactory on the relevance of the interlayer interaction and energy levels at interface. Herein, the energy level alignment at g-C3N4/BiPO4 interface is systematically explored by first-principles calculations incorporating semiempirical dispersion-correction schemes. The results indicate that a stable interface with the chemical adsorption can be formed between g-C3N4 and BiPO4. Interestingly, a typical type-II band alignment at g-C3N4/BiPO4 interface is found based on the analysis of the energy band structures and work functions, where the valence and conduction band edges of the BiPO4 layer are higher than those of the g-C3N4 layer after the actual contact of BiPO4 and g-C3N4, respectively. Especially, both charge density difference and Mulliken population show that a built-in electric field is formed with the direction from g-C3N4 to BiPO4 after interfacial equilibrium, and facilitates the separation of photoinduced e–/h+ pairs. In addition, it is found that the introduction of g-C3N4 could boost light harvesting. The present investigation provides insightful information regarding the observed enhanced photocatalytic activity of g-C3N4/BiPO4 heterojunctions.