First-principles study of two-dimensional HfS2/GaS van der Waals heterostructure for photocatalytic action

Abstract

Exploring excellent performance of photocatalysts for hydrogen/oxygen evolution reactions is an effective way for solar energy applications. In this work, a HfS 2 /GaS van der Waals heterostructure (vdwH) has been designed to achieve efficient and spontaneous water decomposition. Through first-principles calculation, HfS 2 /GaS vdwH has been proved to be a stable and promising photocatalyst with the following obvious advantages: both water reduction and oxidation potentials are located in the band gap of HfS 2 /GaS vdwH (2.04 eV), ensuring that water splitting can occur. The type-Ⅱ band structure and built-in electric field ensure the effective separation of photoelectron-hole, and the high mobility of electrons and holes can also predict high photocatalytic activity . By calculating the free energy of the oxygen evolution reaction on the surface of GaS and the hydrogen evolution reaction on the surface of HfS 2 of the heterostructure , it's found that the water decomposition reaction can occur spontaneously under light. Furthermore, after 1–6% in-plane biaxial tensile strain was applied, the redox reaction of photocatalytic decomposition water can still occur on the HfS 2 /GaS vdwH, and the application of strain can effectively regulate the optical and electronic properties. Therefore, HfS 2 /GaS vdwH could be a promising candidate material for the photocatalytic decomposition of water. • The spatial separation of photogenerated carriers is realized in type-II HfS 2 /GaS heterostructure. • The electron mobility can be as high as 10 3 cm 2 V −1 s −2 . • Free energy calculation shows that the water decomposition reaction can occur spontaneously under light. • HfS 2 /GaS heterostructure reach high light absorption coefficients of 3.6 × 10 5 cm −1 .