Role of MoS2 and WS2 monolayers on photocatalytic hydrogen production and the pollutant degradation of monoclinic BiVO4: a first-principles study

Abstract

The global dependence on exhaustible fossil fuel resources has made the search for an alternative renewable and sustainable fuel more urgent. Photocatalysis has gained increasing consideration as a promising technology to solve problems associated with solar energy conversion. Fabricated m-BiVO4- based heterostructures have shown improved photocatalytic activity for hydrogen evolution and pollutant degradation; however, a deeper understanding of the photocatalytic mechanism and the role of the monolayers is still lacking. Moreover, no theoretical studies have been carried out on MS2/m-BiVO4(010) heterostructures. In the present study, the roles of MoS2 and WS2 monolayers loaded onto a m-BiVO4 surface for active photocatalytic hydrogen production and pollutant degradation are explored using firstprinciple studies. Herein, hybrid density functional calculations and a long-range dispersion correction method were used to investigate the charge transfer, electronic properties, photocatalytic activity and mechanism of the MS2/m-BiVO4(010) heterostructures. The results showed a narrow band gap, built-in potential and a type-II band alignment for the MS2/m-BiVO4(010) heterostructures compared to pure m-BiVO4, which favour the separation and transfer of charge carriers and visible-light-driven activity. The MoS2/m-BiVO4 heterostructure showed a suitable band edge for hydrogen production and pollutant degradation compared to the WS2/m-BiVO4 heterostructure. This improvement was attributed to the role of the MoS2 monolayer as an electron donor, the many reactive sites on the MoS2 surface and the enhanced electron/hole pair separation of charge carriers at the MoS2/m-BiVO4(010) interface. Considering that the MS2 monolayer coupled with m-BiVO4 can restrain the electron-hole recombination rate without lattice distortion indicates that the heterostructure approach is better than the doping approach. Based on the analysis of the electronic properties, the MS2/m-BiVO4(010) heterostructures were shown to fit within the acceptable band gap and built-in potential range. The proposed theoretical design paves a way for the effective and large-scale fabrication of m-BiVO4-based photocatalyst for solar energy conversion and environmental remediation applications