A First Principles Investigation of Optoelectronic and Photocatalytic Behavior of Heterostructure PtS ₂ /AlS

Recent advances in two‐dimensional van der Waals (vdW) heterostructures have highlighted the importance of stacking configuration and interfacial interactions in tailoring their electronic and catalytic properties. Motivated by these developments, we systematically investigate the structural, electronic, optical, and photocatalytic properties of the PtS ₂ /AlS vdW heterostructure using first‐principles density functional theory calculations. Four possible stacking configurations are examined, and the energetically and dynamically stable configuration is identified from its adhesion energy and phonon dispersion. The optimized PtS ₂ /AlS vdW heterostructure exhibits a hexagonal structure, indirect band gap, and type‐II band alignment, as supported by work‐function differences and charge‐density analysis, indicating efficient spatial separation of photogenerated charge carriers. The weak interlayer interaction is further supported by electron localization function analysis. The heterostructure exhibits strong optical absorption with an absorption coefficient of the order of 10 ⁵  cm ⁻¹ , extending from the visible to the ultraviolet region. Furthermore, the calculated band‐edge positions satisfy the requirements for photocatalytic water splitting, with suitable redox potentials maintained up to pH 10. These results establish PtS ₂ /AlS as a promising vdW heterostructure for photocatalytic and optoelectronic applications.