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

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 first-principle 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.