The direct Z-scheme g-C6N6/WTe2 van der Waals heterojunction as photocatalyst over water splitting in the visible light: Designing strategy from first principles

Using two-dimensional (2D) materials as photocatalysts for water splitting is considered an effective technique to solve the related environmental pollution and the energy issues. Herein, based on first-principles calculations, we systematically investigated the structural, optoelectronic and photocatalytic properties of the novel g-C6N6/WTe2 heterojunction. The results demonstrate that the heterojunction is a direct Z-scheme photocatalytic system and the band edge straddles the redox potential for water splitting. Interestingly, the heterojunction exhibits excellent sunlight capturing capacity in the visible-light range, which could generate sufficiently photoelectrons and holes for water splitting. Furthermore, in the acidic environment, the processes of OER and HER can spontaneously and simultaneously proceed on the surface of the heterojunction without any additional potential. At the same time, the remarkable solar-to-hydrogen conversion efficiency is 57.59% for the heterojunction. We believe that this theoretical investigation not only paves the way for the design of future Z-scheme systems in water splitting but also provides new insights to modify the photocatalytic properties of 2D materials.