Highly efficient overall photocatalytic water splitting in 2D heterostructure GaSe/ScGaSe3

Abstract

In the field of photocatalytic water splitting, the efficient utilization of solar energy is paramount. However, until now, the infrared and ultraviolet portions of the solar spectrum, which collectively constitute nearly half of the total solar energy, have remained underutilized, resulting in significant losses in solar energy utilization efficiency. Herein, we meticulously design a type-II band-aligned GaSe/ScGaSe₃ heterostructure and meticulously examine its photocatalytic capabilities through rigorous first-principles calculations. The calculation results reveal the valence band and conduction band are distributed on two opposite surfaces with a large electrostatic potential difference produced by the intrinsic dipole of the photocatalyst. This surface potential difference, acting as an auxiliary booster for photoexcited electrons, This enables the GaSe/ScGaSe₃ heterostructure to exhibit a minimal indirect band gap of 0.44 eV, ensuring effective photocatalytic water splitting reactions at all pH values under the action of the inherent electric field. Furthermore, the heterostructure possesses unique optical properties, demonstrating a high light absorption coefficient. It captures an impressive 10 % to 43 % of visible and ultraviolet light, significantly enhancing the utilization efficiency of sunlight. Encouragingly, our analysis shows that the corrected solar-to-hydrogen (STH) efficiency of this heterostructure is 33.77 %, marking a tremendous leap of 346 % compared to standalone GaSe monolayers. Additionally, the application of biaxial tensile strain further boosts this efficiency to an astonishing 36.46 %. These remarkable characteristics not only emphasize the immense potential and broad application prospects of the GaSe/ScGaSe₃ heterostructure but also underscore its significance in advancing the field of photocatalytic water splitting.