The surface reconstruction induced enhancement of the oxygen evolution reaction on α-SnWO4 (010) based on a density functional theory study

The coordination environment of photocatalytic active sites is determined by the type of surface termination on an α-SnWO4 semiconductor. However, the stability of these surface terminations has not been thoroughly explored. In this work, the stability of the α-SnWO4(010) surface termination was studied using a thermodynamic analysis based on density functional theory (DFT). Under appropriate thermodynamic equilibrium conditions, it is possible to stabilize the O-W, O-Sn, R-OOSn and ST3 terminations of the α-SnWO4(010) surface. The electronic structures of these three potential stable surface terminations are also calculated using a Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional to determine the conceivable bandgap values. It is found that there are numerous surface states in the bandgap of these terminations. This is due to the evident reconstruction of these terminations after geometry optimization. In addition, work functions are substantially different for possible surface terminations. The results suggest that Z-scheme heterostructures based on SnWO4 can be regulated by securing the thermodynamically favorable surface terminations under suitable physical/chemical conditions. At last, O-Sn termination exhibits a low overpotential value of 0.51 V, showing remarkable oxygen evolution reaction (OER) performance among all stable surface terminations considered in this work. Our study may help explore the intrinsic surface properties of SnWO4, which will be a viable strategy for developing SnWO4-based photocatalysts.