First-principles investigation of type-II GaO/MX2 (M = Mo, W; X = S, Se) van der Waals heterostructures for enhanced optoelectronic, photocatalytic and energy conversion applications.

Two-dimensional (2D) van der Waals heterostructures (vdWHs) offer an effective strategy to enhance the electronic, optical and photocatalytic properties of 2D materials. In this paper, first-principles calculations were used to calculate the structural stability, electronic properties, interfacial charge transfer, optical response and photocatalytic performance of GaO/MX2 (M = Mo, W; X = S, Se) vdWHs. Six stacking configurations were investigated for each vdWH, and their energetic and thermal stability were confirmed by binding energy, interlayer spacing and ab initio molecular dynamics simulations. The GaO/MX2 vdWHs showed indirect type-II band alignment, facilitating efficient charge separation and reducing electron-hole recombination. The obtained charge density difference, work function and electrostatic potential confirmed significant interfacial charge redistribution and built-in electric fields. Furthermore, the GaO/MX2 vdWHs demonstrated strong visible-to-near-infrared light absorption with enhanced solar-harvesting capability. Photocatalytic water splitting indicated that GaO/MoS2 and GaO/WS2 satisfied the band-edge requirements for visible-light-driven water splitting, highlighting their potential for photocatalytic and optoelectronic applications.