GaN/BS van der Waals heterostructure: A direct Z-scheme photocatalyst for overall water splitting

[Display omitted] •GaN/BS van der Waals heterostructures possesses Z-scheme charge transform.•The band edges of the GaN/BS straddle the water redox potentials, forming a direct Z-scheme photocatalysts for overall water splitting.•Biaxial and external electric field can effectively modulate the band edge positions and optical properties of GaN/BS.•The solar-to-hydrogen efficiency ηSTH of the heterostructure can reach 19.95 % at the ε = 6 %, significantly higher than GaN (0.28 %) and BS (1.55 %) monolayers.•The photocurrent of the GaN/BS is greater than its individual components. Direct Z-scheme heterostructures have attracted much attention as promising solar-driven water splitting photocatalysts. Here, the GaN/BS van der Waals heterostructures with Z-scheme charge transform model are constructed. The electronic structure, optical properties and photocatalytic mechanism are investigated using the first-principles calculations. Our results demonstrate that the electrons migrate from GaN to BS layer in GaN/BS heterostructure and its band edges straddle the water redox potentials, forming a direct Z-scheme photocatalysts for overall water splitting. Biaxial and external electric field can effectively modulate the band edge positions and optical properties, promoting more photons participating in the water splitting. The solar-to-hydrogen efficiency ηSTH of the heterostructure can reach 19.95 % at the ε = 6 %, significantly higher than GaN (0.28 %) and BS (1.55 %) monolayers. Negative electric field also can improve the ηSTH. The work provides a valuable theoretical guidance for designing of the GaN/BS heterostructures and pointing that the heterostructures have great promising for application in photocatalytic water splitting.