The SnC/WS2 vdW heterojunction: A prospective direct Z-scheme photocatalyst for overall water decomposition with high STH efficiency and catalytic activity

Abstract

Searching for an advanced photocatalyst is a solution to the global energy scarcity and environmental problem. In this paper, we construct a SnC/WS2 heterojunction and its structural, electronic, optical and photocatalytic properties have been investigated by first-principles calculations. The SnC/WS2 heterojunction exhibits thermodynamic stability, with a type II (staggered) energy band structure and an indirect bandgap of 1.393 eV. A built-in electrical field with direction from SnC layer to WS2 layer is formed together with a band bending in interface region. The SnC/WS2 heterojunction is a direct Z-scheme photocatalyst supporting overall water decomposition, allowing a reductive reaction to take place in the conduction band of the SnC layer to produce H2 and an oxidative reaction in the valence band of the WS2 layer to produce O2. Meanwhile, the light absorption of the SnC/WS2 heterojunction is superior to that of the two single layer materials, with the highest absorption peak 5.3 × 105 in visible light region and a solar-to-hydrogen efficiency of 42 %. Furthermore, the Gibbs free energy calculations demonstrate the high catalytic activity of the SnC/WS2 heterojunction for redox reactions. The findings reveal that the SnC/WS2 heterojunction is a super-efficient direct Z-scheme photocatalyst for overall water splitting.