Origin of High Photocatalytic Efficiency in Monolayer g-C3N4/CdS Heterostructure: A Hybrid DFT Study

Graphite-like carbon nitride (g-C3N4)-based heterostructures have attracted much attention because of their prominent photocatalytic performance. However, theoretical understanding on the relationship of the interface and enhanced photocatalytic activity is still lacking. In this study, we systematically calculated energy band structure and charge transfer of the g-C3N4/CdS heterojunction using the hybrid density functional approach. The interaction between g-C3N4 and the CdS (110) surface was explored. Results indicated that g-C3N4 and CdS were in contact and formed a van der Waals heterojunction. The valence and conduction band edge positions of g-C3N4 and CdS changed with the Fermi level and formed a standard type-II heterostructure. Furthermore, density of states, Bader charge, and charge density difference indicated that the internal electric field facilitated the separation of electron–hole pair in the g-C3N4/CdS interface and restrained carrier recombination. These results demonstrated that the band structure of the g-C3N4/CdS heterojunction had significant advantages to improve photocatalytic efficiency under visible-light irradiation. Moreover, our work may be used as a basis for the design of other highly active heterostructures.