A direct Z-scheme GaTe/AsP van der Waals heterostructure: A promising high efficiency photocatalyst for overall water splitting with strong optical absorption and superior catalytic activity

The existing energy crisis and environmental pollution require an innovative approach to hydrogen production. Photocatalytic water-splitting has emerged as a potential solution, but the development of efficient photocatalysts remains the key challenge. Here, we employ first-principles calculations to investigate the structural, electronic, optical and photocatalytic characteristics of a van der Waals heterojunction comprising GaTe and AsP monolayers. The constructed GaTe/AsP heterojunction is thermodynamic, dynamical and thermal stable. The smaller indirect bandgap 1.68 eV than 2.21 eV and 2.45 eV for the constituent GaTe and AsP monolayers respectively, enhances the optical absorption of the GaTe/AsP heterojunction in visible and ultraviolet (UV) regions. The type-II band alignment of the GaTe/AsP heterojunction makes an efficient separation of photogenerated electrons and holes to different layers and extension their lifespans. The built-in electric field from GaTe side to AsP side induces a direct Z-scheme heterojunction photocatalyst with high redox reaction kinetic and high solar-to-hydrogen efficiency of 14.10 %. Our study demonstrates that the GaTe/AsP heterostructure is as efficient photocatalysts for overall water-splitting.