LAUSR

Abstract Considering the reported Bi2Se3 monolayer with P-3M1 space group cannot match energy band edges for the hydrogen evolution reaction(HER) and the oxygen evolution reaction(OER), we identify three Bi2Se3 monolayers with desirable bandgap, band edges, and optical absorption for the redox reactions, based on the twenty two-dimensional structures screened by using Universal Structure Predictor: Evolutionary Xtallography with the first-principles calculations. The stabilities of the identified geometrical configurations are confirmed by phonon dispersion and ab initio molecular dynamics simulation, respectively. The density of states, bandgap and band edges, the optical absorption, mobility, and effect of strain engineering are determined and used to evaluate the photoelectronic properties of the monolayers. The results show that the I-Bi2Se3 monolayer possesses an approximate direct bandgap of 1.44/1.77eV by HSE06/GW. However, the II-Bi2Se3 and III-Bi2Se3 monolayers show indirect bandgaps of 1.91 and 2.15 eV by HSE06 and 1.99 and 2.84 eV by GW. The band edges can match the redox potentials of HER and OER, although one of them needs +3% biaxial tensile strain. The enhanced visible-light and UV absorptions and apparent mobility difference between the electron and hole are also observed. All results support the newfound Bi2Se3 monolayers could be candidates for HER and OER.