Nail-like α-SnWO<sub>4</sub> Array Film with Increased Reactive Facets for Photoelectrochemical Water Splitting
Yang Liu, Weixin Qiu, Gaoshuang He, Keke Wang, Yanqiu Wang, Long Chen, Qing Wu, Wenzhang Li, Jie Li
Abstract
α-SnWO4 is a good candidate for photoelectrochemical (PEC) water splitting due to its suitable band position that straddles the H+/H2 and O2/H2O redox potentials. However, its poor charge transfer ability results in unsatisfactory PEC performance. From the view of material design, a nail-like α-SnWO4 array film was constructed by a hydrothermal method assisted by halogen ions, and the corresponding physical and PEC properties are discussed. Density functional theory (DFT) calculations were also performed to help understand the effect of halogen ions (Cl–, F–) on the growth and exposure facet of α-SnWO4 and the underlying mechanism of PEC performance. The existence of F– decreases the surface energy of the {100} and {001} facets, directions along which the film has better charge transfer, and the {001} facet has a lower barrier in the PEC water oxidation reaction. The α-SnWO4 film photoanode after facet regulation presents better charge transfer ability, and the oxygen evolution rate is 0.16 μmol cm–2 h–1. In addition, a 1.9-fold photoresponse current is obtained during unbiased PEC water splitting.