Mechanism study on direct Z-scheme HfSSe/Arsenene van der Waals heterojunction for photocatalytic water splitting

The performance of HfSSe/Arsenene van der Waals heterostructure in photocatalytic water splitting based on density functional theory (DFT) is investigated, in which the heterostructure is categorized into two configurations, S-As and Se-As, according to the distances of S and Se to the Arsenene layer. Calculations of the band structures, work functions, electron transfer, and band-edge position reveal that both the configurations are identified as direct Z-scheme heterojunction in photocatalysis. Moreover, the hydrogen evolution reaction (HER) occurs on the Arsenene surface, while the oxygen evolution reaction (OER) occurs on the HfSSe surface. After forming a monolayer HfSSe/Arsenene heterojunction, the carrier mobility of the system is increased. Furthermore, the optical properties of the system have been studied using the G0W0+BSE (Bethe-Salpeter equation) method, and the results show an increase in the absorption coefficient in both visible and ultraviolet regions. Additionally, the absorption coefficient of the heterostructure is significantly affected by conducting biaxial strains, thus further alters the reactivity of hydrogen evolution reaction and oxygen evolution reaction.