External uniaxial compressive strain induced built-in electric field in bilayer two-dimensional As2S3 for photocatalytic water splitting: A first-principles study

Highlights: • A built-in electric field occurs between in the sublayers of As₂S₃. • The As₂S₃ nanosheets are suitable for hydrogen production through water splitting. • The As₂S₃ nanosheets show a high anisotropy on optical and electronic properties. Water splitting to produce H₂ through photocatalysis is an attractive means to deal with the energy crisis, and a built-in electric field is rather crucial for the separation of photogenerated carriers. In this study, by applying uniaxial strain on mono- and bilayer As₂S₃, the strain-tunable electronic and optical properties feature a strong anisotropy in 2D As₂S₃. The band edges under all strain conditions are found to meet the potential redox rule of water splitting. The built-in electric field, deduced by the compressive uniaxial strain along a direction in bilayer As₂S₃, is beneficial to separate the photogenerated carriers and thus improves the photocatalytic efficiency. The optical absorption shows that 2D As₂S₃ is rather suitable for photocatalytic water splitting in the ultraviolet region. Our findings provide enlightenment to realize the built-in electric field in a bilayer structure, not by substituting atom but by applying strain only.