Two-Dimensional Long-Plate SnWO₄ Photoanode Exposed Active Facets for Enhanced Solar Water Splitting

α-SnWO4 is a potential catalyst for photoelectrochemical (PEC) water splitting with its narrow band gap and suitable band position, while its PEC performance is restricted by poor carrier transport ability. Herein, morphology control together with facet engineering as a strategy is used to optimize the carrier transport of the SnWO4 film photoanode. In this paper, a two-dimensional (2D) long-plate structure for the SnWO4 film was obtained from a rod-like WO3 film due to the inherited behavior of the morphology, and the added fluoride ions (F–) further smoothed the surface of α-SnWO4 and increased the proportion of active facets. As a result, 2D SnWO4 with favorable facets presents ∼0.79 mA/cm2 at 1.23 V vs reversible hydrogen electrode (RHE) in KPi without any sacrificial agent, which is much larger than the SnWO4 film (0.26 mA/cm2) transformed from plane WO3 without structure-directing agents. We believe this work provides a pathway to design ternary metal oxide-based nanostructured film electrodes.