First-principles prediction a promising direct Z-scheme HfS2/InP van der Waals heterojunction photocatalyst with superior optical absorption, high STH efficiency and strong catalytic activity for overall water-splitting

In recent years, direct Z-scheme van der Waals heterojunctions based on two-dimensional materials have been at the forefront of solar water decomposition for hydrogen production. This paper utilizes first-principles calculations to thoroughly examine the HfS 2 /InP heterojunction, with a focus on its structural stability, electronic behavior, photocatalytic efficiency, and optical properties. The results show that the HfS 2 /InP heterojunction has a type II energy band arrangement and a direct Z-scheme charge transfer path. A built-in electric field pointing from InP side to HfS 2 side is formed at the interface. A high solar-to-hydrogen (STH) conversion efficiency η STH of 13.8 % is obtained under AM1.5G solar illumination, with favorable band edge positions enabling water splitting in a wide pH range (0–11). Furthermore, the photocatalytic performance of the material exhibits remarkable stability over a strain range of −6 % to2 %. The results indicate that the HfS 2 /InP heterojunction is a promising candidate for photocatalytic water splitting due to its high photocatalytic efficiency and strain stability. This research provides valuable theoretical insights and potential applications for advancing photocatalyst design and green energy technologies. (a) Schematic representation of photocatalytic hydrolysis reactions and photogenerated electrons and holes flow at the interface of the HfS 2 /InP heterojunction. (b) Redox reaction potentials of HER (black balls and lines) and OER (red balls and lines) for overall water-splitting as a function of pH value relative to the CBM (−3.75 eV) of InP layer (blue dashed line) and VBM (−6.66 eV) of the HfS 2 layer (violet dashed line) in the HfS 2 /InP heterojunction with respect to vacuum level. • HfS 2 /InP heterostructure is a direct Z-scheme heterostructure photocatalyst. • HfS 2 /InP heterostructure has a built-in electric field from InP side to HfS 2 side. • HfS 2 /In Pheterostructure has a high solar-to-hydrogen efficiency of 13.8 %. • HfS 2 /InP heterostructure shows a strong catalytic activity for overall water-splitting. • HfS 2 /InP heterostructure shows a high optical absorption coefficient of 4.78 × 10 5 cm −1 .