2D Janus MoXSiN ₂ (X = S, Se, Te): Excellent Photocatalysts with Extremely High Energy Conversion Efficiency for Water Splitting

The transport and recombination rates of photogenerated carriers are key factors affecting the efficiency of photocatalytic water splitting. Here, we investigated the photocatalytic performance of 2D Janus MoXSiN2 monolayers by first-principles calculations. The results show that photogenerated electrons and holes distribute in two different layers and there exist intrinsic built-in electric fields along vertical direction. Furthermore, average nonadiabatic coupling (NAC) and time-dependent ab initio nonadiabatic molecular dynamics (NAMD) calculations approve that the built-in electric field endows photogenerated carriers rapidly transfer rather than recombine to participate in redox reactions. Janus MoSeSiN2 and MoTeSiN2 can achieve photocatalytic water splitting in all acid–base solutions (pH = 0–14). Notably, MoTeSiN2 achieves an extremely high carrier utilization rate of 61.4% with a corrected solar-to-hydrogen STH efficiency of 28.7%. These findings suggest that MoXSiN2 is a remarkably promising photocatalyst for water splitting.