Strain engineering on the electrical properties and photocatalytic activity in gold sulfide monolayer

Abstract

In comparison with bulk materials, two dimensional materials are more suitable as photocatalysts due to their large surface-volume ratios and high anisotropic carrier mobilities. In this contribution, the gold sulfide monolayers (α-, β-Au2S, α-, β-, γ-AuS) are theoretically predicted as potential photocatalysts for water splitting applications using first principles calculations. β-AuS monolayer has more suitable band gap of 1.79 eV and band edges as compared with the other four monolayers. It also possesses high anisotropic carrier mobilities (electron: 1.9 × 104 cm2∙V−1∙s−1, hole: 6.16 cm2∙V−1∙s−1) and the electron carrier mobility is about as 100 times large as that of MoS2 (~200 cm2∙V−1∙s−1) and 20 times as that of black phosphorus monolayer (1100–1140 cm2∙V−1∙s−1). The solar-to-hydrogen (STH) efficiency of β-AuS monolayer reaches up to 17.21%, almost closing to the limit conventional theoretical value (18%). Moreover, it is observed that the band gap of β-AuS monolayer can be tuned from indirect to direct when 4%–8% compressive strains applied. Surprisingly, β-AuS monolayer under 4% compressive strain along armchair direction has ultrahigh and anisotropic electron carrier mobility in both zigzag direction (1.9 × 106 cm2∙V−1∙s−1) and armchair direction (2.9 × 105 cm2∙V−1∙s−1), respectively, which enable β-AuS monolayer great potential application in multifunctional optoelectronics and photocatalysis.