Theoretical investigation of an arsenene/g-CN van der Waals heterojunction: a direct Z-scheme system with high photocatalytic efficiency.

With advancements in algorithms and computational power, theoretical calculations have become increasingly feasible for designing and constructing functional materials. In this study, we utilized density functional theory (DFT) to investigate the new arsenene/g-CN van der Waals heterojunction, which forms a direct Z-scheme system with an indirect bandgap of 1.41 eV and a minimal lattice mismatch of just 1.4%. The heterojunction's band edge positions are favorable for overall water splitting across a wide strain range (-6% to +6%) and varying pH conditions. Photocatalytic analysis reveals that the oxygen evolution reaction (OER) proceeds spontaneously under light irradiation, while the hydrogen evolution reaction (HER) requires an energy barrier of 0.47 eV, which can be further reduced to 0.2 eV under -6% compressive strain. The heterojunction also demonstrates enhanced visible light absorption, with a redshift in the absorption spectrum under biaxial strain, significantly boosting solar energy utilization. Remarkably, the heterojunction achieves a solar-to-hydrogen (STH) conversion efficiency of 47.84%, outperforming many previously reported photocatalytic materials. With a strong interfacial binding energy of -27.54 meV Å, confirmed by molecular dynamics simulations, its exceptional structural stability positions it as a promising candidate for experimental realization. These findings underscore the potential of the arsenene/g-CN heterojunction as a high-performance platform for advanced photocatalytic applications.