Type-II AsP/Sc2CO2 van der Waals heterostructure: an excellent photocatalyst for overall water splitting

In this work, we explore the application potential of AsP/M 2 CO 2 (M = Sc, Zr) van der Waals heterostructures in photocatalytic water splitting through the first-principles calculations. The calculated results show that AsP/Zr 2 CO 2 heterostructure possesses an unfavorable type-Ⅰ band alignment, whereas AsP/Sc 2 CO 2 exhibits a desirable type-Ⅱ band alignment, which is beneficial for separating the photogenerated electron-hole pairs. Also, the band edge positions of AsP/Sc 2 CO 2 heterostructure stride the redox potential of water, ensuring favorable reaction kinetics. Besides, the strong optical absorption of AsP/Sc 2 CO 2 heterostructure in both visible and ultraviolet regions (especially up to 10 −6 cm −1 at about 250 nm) makes it possible to utilize solar energy effectively. Meanwhile, AsP/Sc 2 CO 2 heterostructure has an exciton binding energy as low as 0.09 eV, which quantitatively illustrates the high separation efficiency of photogenerated charge carrier. Thus, the type-Ⅱ band alignment, suitable band edge position, strong light absorption, and low exciton binding energy together indicate that AsP/Sc 2 CO 2 heterostructure is a potential photocatalytic material. In addition, the obvious redshift phenomenon in the optical spectrum of AsP/Sc 2 CO 2 heterostructure shows that biaxial strain can improve its light capture capability. Also, the interconversion between type-Ⅱ and type-Ⅰ can be achieved by applying different strains. All these findings suggest that the novel AsP/Sc 2 CO 2 heterostructure has significant application prospects in next-generation photovoltaic and photocatalytic devices. • AsP/Sc 2 CO 2 heterostructure good optical absorption in visible and ultraviolet regions. • The lower exciton binding energy of AsP/Sc 2 CO 2 heterostructure confirms the effective carrier separation. • The conversion of heterostructure type and the improvement of optical properties are realized under biaxial strain.