Engineering two-dimensional SnC/HfSSe heterojunction as a direct Z-scheme photocatalyst for water splitting hydrogen evolution

Developing robust water-splitting photocatalyst remains a pivotal challenge for the conversion of solar energy to hydrogen fuel. Herein, we report SnC/HfSSe heterojunctions to be a competitive direct Z-scheme photocatalysts with HfSSe acting as an oxidant and SnC as a reductant for water-splitting hydrogen generation by employing the first-principles calculations. The photogenerated electron–hole migration logically follows the Z-scheme path due to the large interlayer built-in electric field, small interlayer bandgap, proper band edge alignment, and high interlayer carrier recombination. The overpotential is appropriate to the oxygen evolution reaction (OER), while the overpotential is slightly large to the hydrogen envolution reaction (HER) so that the incident photon energy above the band gap of the components is required for the HER. The heterojunctions have excellent visible light absorption, exhibiting the remarkable red shift and stronger light absorption with respect to the two components of the heterojunction. Moreover, the heterojunction exhibits an outstanding solar-to-hydrogen (STH) efficiency as high as 27% in extremely acidic solution.