Two-Dimensional Layered MoS ₂ –MXO (M = Mo, W; X = S, Se, Te) van der Waals Heterostructures for Optoelectronics, Visible Light Photocatalysis, and Solar Energy Application

Two-dimensional (2D) van der Waals heterostructures (vdWHs) enable unprecedented flexibility in tailoring the structural and optoelectronic properties, facilitating their use across diverse next-generation device applications. Here, we used the first-principles study and comprehensively examined MoS₂ and MXO (M = Mo, W; X = S, Se, Te) monolayers and their layered vdWHs. We modeled 12 different stacking configurations of MoS₂-MXO vdWHs for model-I and model-II (six for each model) and examined their stability through binding energy, interlayer distance, and ab initio molecular dynamics (AIMD) simulations at room temperature. Remarkably, MoS₂-MXO vdWHs exhibit a staggered type-II band alignment, while MoS₂-WTeO vdWHs show type-I band alignment, confirming that they inherently facilitate spatial separation of photogenerated electrons and holes, showing good response toward high-efficiency optoelectronic and photocatalytic water splitting. Work function and plane-averaged electrostatic potential difference, as well as charge density difference distributions were investigated, which highlight pronounced charge redistribution and potential steps, underscoring the presence of interlayer charge transfer at the interface of MoS₂-MXO vdWHs that can effectively modulate carrier dynamics. The optical response was explored through calculations of the complex dielectric function, revealing pronounced absorption across the visible and also near-infrared regions, confirming it as an appealing candidate for high-performance solar energy conversion, photodetection, and optoelectronics. Further, photocatalytic applications of MoS₂-MXO vdWHs were examined by aligning their band edges with respect to the redox potentials of water for pH = 0-3. Our results demonstrated that the band edge positions of MoS₂-MXO vdWHs possess the thermodynamic requirements necessary for visible-light-driven water splitting, hence enabling both hydrogen and oxygen evolution reactions. Collectively, our findings establish MoS₂-MXO vdWHs as promising platforms for next-generation photocatalytic hydrogen production, offering a viable route toward sustainable and clean energy technology applications.