Janus monolayer SiXY (X = P, as and Sb, Y = N, P, As) for photocatalytic water splitting

We theoretically propose a types of Janus monolayers SiPN and SiXY (X = As, Sb; Y = P, As) with high stability, suitable band structures and outstanding light absorption for photocatalytic water splitting. On the basis of the first-principles calculations with the HSE06 functional and EVGW0 + BSE method, we determine that monolayer SiPN has mediocre optical absorption, appropriate STH efficiency, small electronic effective mass, and indirect band gap with value of 2.49 eV. We have also explored the anisotropy-tunable electronic and optical properties under uniaxial strain. Additionally, through replacing the surface atoms in monolayer SiPN, we have built monolayer SiAsP, SiSbP, and SiSbAs, whose band gaps are 2.35 eV, 1.88 eV, and 2.17 eV, respectively. Furthermore, we obtain that monolayer SiAsP, SiSbP, and SiSbAs have smaller effective mass, higher solar to hydrogen (STH) efficiency, as well as better optical absorption in visible-light region. Our work not only propose four Janus monolayers for expanding the instances of two-dimensional Janus semiconductors but also provide a guide for modifying mediocre 2D semiconductor photocatalysts into the high-performance one for photocatalytic water splitting.