Hydrogen generation through photoelectrochemical (PEC) technology is one of the most appropriate ways for delivering sustainable fuel. Simultaneously, anisotropic properties will be exhibited by the materials with low crystal symmetry, allowing the tuning of the PEC properties by controlling the crystallographic orientation and exposed facets. Therefore, we synthesized copper tungstate films (CuWO 4 ) with highly exposed (100) crystal facets by regulating anions in the precursor solution. According to experimental characterization and density functional theory calculations, the CuWO 4 film with a high exposure ratio of the (100) crystal facet has promoted charge transport with trapfree mode and reduced recombination of electrons and holes. Meanwhile, the oxygen evolution reaction is promoted on the (100) facet because of the relatively low energy barrier. Compared to the CuWO 4 with other mixed exposure facets, CuWO 4 with a highly exposed (100) facet presents a twofold current density (0.38 mA/cm 2 ) and one-fifteenth electron transit time (0.698 ms) and also has great stability (more than 6 h). These results provide an easy way to enhance the PEC performance by modulating the exposure facets of the film electrode.

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.

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.

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Stannous tungstate (α-SnWO4) is a promising photoanode material for photoelectrochemical (PEC) water splitting, but its practical performance is severely limited by the charge recombination problem that results from poor bulk charge transport ability. Herein, SnWO4 with a two-dimensional (2D) sheet-like array morphology (SnWO4-NS) was formed to provide pathways for accelerating charge transport, which is demonstrated by the small radius of electrochemical impedance spectroscopy and a short charge transport time of intensity-modulated photocurrent spectroscopy. The carrier separation efficiency and hole collection efficiency of SnWO4-NS were improved to 6.84 and 40.66% compared to those (4.83 and 13.18%) of SnWO4 without controlled morphology at 1.23 V versus the reversible hydrogen electrode. As a result, the photocurrent density increased from 0.086 to0.41 mA cm–2, and a larger amount of oxygen was obtained in the same period. This 2D morphology modification method will provide a new idea for developing α-SnWO4 with efficient PEC performance.