Design of an efficient photocatalyst: a type II heterojunction for enhanced hydrogen production driven by visible light.

Abstract

Solar hydrogen production, which is an eco-friendly method to obtain energy, is still far away from wide commercialization due to the lack of an efficient catalyst. Effective calculations can reduce trial and error costs and provide mechanistic explanations while exploring efficient catalysts. Herein, a type II heterojunction Mg-containing-porphyrin/g-C3N4 is proven to be an efficient photocatalyst by using a combination of DFT and many-body Green's function theory. Our results show that the heterojunction can significantly enhance the absorption of visible light and realize the separation of photogenerated electrons and holes after excitation. Subsequently, water absorbing on the excited surface decomposes into H+ and OH- easily, and then produces H2 and O2 with reduced free energy. Our investigation and explanation can provide theoretical support for designing photonic devices based on porphyrin and g-C3N4, and deepen the understanding of how H2O splits into H2.