High carrier mobilities and tunable band structures in two-dimensional MNH2 (

Qi Li,Hong-Yao Liu,Huan Yang, Yuxin Zheng

Two-dimensional (2D) materials have injected new possibilities into the field of photocatalysis. In this work, the graphene-like MNH2 (M,N= C, Si, Ge) monolayers are predicted as a series of promising optoelectronic materials by the first-principles calculations. The results show that the MNH2 monolayers have direct bandgaps and the largest electron mobility is 8.15 ×104 cm2 V −1 s−1 for the Si2H2 monolayer, which is obviously higher than that of graphene. The bandgaps are tunable under strains, and the band edges of the Si2H2 and SiGeH2 monolayers can span the reduction potential and oxidation potential of water decomposition to produce hydrogen with specific biaxial strains. Under 4% strains, the solar-to-hydrogen efficiency of the Si2H2 and SiGeH2 monolayers can reach 19.27% and 13.22%, respectively. Thus, the Si2H2 and SiGeH2 monolayers can be predicted as promising photocatalytic materials for the water splitting under visible light irradiation.