vdW Heterostructure MoSe2/MoSi2P4: A Promising Material for Photocatalytic Hydrogen Production and Photovoltaic Applications

Herein, we have thoroughly investigated the potential of the van der Waals heterostructure (vdWH) MoSe₂/MoSi₂P₄ for sustainable energy applications. With a nominal lattice mismatch of ∼1.4% between the constituent monolayers, the heterostructure demonstrates dynamic stability (no imaginary phonon frequencies in the entire Brillouin zone) in all three possible stacking configurations, making it a versatile material for advanced technological applications, providing flexibility in synthesis, tunability in properties, and robustness. It exhibits identical band structures in all three stacking configurations, featuring direct band gaps of 1.02 and 1.12 eV at the Heyd–Scuseria–Ernzerhof functional level, with and without spin–orbit coupling. Additionally, it possesses a type-II band alignment to facilitate the separation of photogenerated electron–hole pairs. Our findings further reveal that the conduction band edges are optimally positioned for potential photocatalytic hydrogen production. Furthermore, the heterostructure displays a significant static dielectric constant of 7.82 as well as an optical absorption of 3.50 × 10⁵ cm^–1 in the visible region. An intense optical absorption appeared in the ultraviolet region. The determined high spectroscopic limited maximum efficiency of ∼30%, compared to those of standard high-performance thin-film absorber materials, such as CuInSe₂ (∼28%) and CdTe (∼31.5%), suggests that the studied heterostructure is a promising photovoltaic absorber material. Our findings shed light on the potential of vdWH MoSe₂/MoSi₂P₄ as a viable candidate for next-generation HER photocatalytic activity and photovoltaics.