Computational exploration and screening of novel Janus MA2Z4 (M = Sc-Zn, Y-Ag, Hf-Au; A=Si, Ge; Z=N, P) monolayers and potential application as a photocatalyst

By high-throughput calculations, 13 thermally and environmentally stable Janus MA2Z4 monolayers were screened from 104 types of candidates. The 13 stable monolayers have very high charge carrier concentrations (×1015 cm-2), which are better than those of the well-known graphene and TaS2. Because of their excellent conductivity, the 6 monolayers with band gaps less than 0.5 eV are identified as potential electrode materials for hydrogen evolution reaction applications. For potential applications as photoelectric or photocatalytic materials, bandgaps (Eg-HSE) higher than 0.5 eV remained, which resulted in 7 potential candidates. Based on optical absorption analysis in the visible-light range, H-HfSiGeP4 and H-MoSiGeP4 have higher absorption ability and optical conductivity, which is quite impressive for optoelectronic, solar cell device, and photocatalysis applications. Additionally, the transmittance coefficient of Janus MA2Z4 monolayers is approximately 70%–80% in the visible-light range, which implies that these monolayers show good light transmittance. For potential applications as photocatalysts, the redox potential and charge effective mass analysis indicate that H-HfSiGeP4, H-MoSiGeP4, T-ScSiGeN4, and T-ZrSiGeN4 are suitable photocatalysts for CO2 reduction reactions. Using high-throughput identification, 13 types of new and stable Janus MA2Z4 monolayers were explored, and the basic properties and potential applications were investigated, which can reduce the time for experiments and provide basic data for the material genome initiative.