Enhanced water splitting photocatalyst enabled by two-dimensional GaP/GaAs van der Waals heterostructure

Two-dimensional (2D) photocatalysts are promising alternatives to traditional 3D metal oxides. However, it is still a great challenge to surmount the limitation restricted by the 2D photocatalytic bandgap together with the band edge position. Herein, we have newly designed 2D GaP/GaAs van der Waals (vdW) heterostructure-based photocatalyst for water splitting and examined the corresponding operating mechanism. Firstly, the tunable electronic, higher carrier mobilities, and excellent optical properties of XP/XAs (X = Ga, In) vdW heterostructures and single-layer counterparts are introduced based on density functional theory. Specially, the GaP/GaAs vdW heterostructure with direct bandgap exhibits more noticeable optical absorption than the single-layer counterparts. Secondly, intrinsic electric field can be obtained in GaP/GaAs vdW heterostructure and the excited electrons and holes of GaP/GaAs vdW heterostructure are present in opposite layers, demonstrating that the GaP/GaAs vdW heterostructure can spontaneously generate the electron-hole separators. Thirdly, the thermodynamic stability of GaP/GaAs vdW heterostructure has been confirmed, which shows high potential for experimental implementation. Finally, due to the superior characteristics, GaP/GaAs vdW heterostructure has been constructed for the photocatalytic water-splitting. Importantly, the photoexcited electrons of GaP/GaAs vdW heterostructure can spontaneously induce hydrogen half reaction without sacrificial reagents. Moreover, the driving force in oxidation half reaction of GaP/GaAs vdW heterostructure can be greatly boosted under light illumination. Our constructed 2D-vdW-semiconductors-based devices provide a promising strategy to achieve high efficiency water-splitting photocatalyst.