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Monoclinic clinobisvanite bismuth vanadate is an important material with wide applications. However, its electronic structure and optical properties are still not thoroughly understood. Density functional theory calculations were adopted in the present work, to comprehend the band structure, density of states, and projected wave function of BiVO(4). In particular, we put more emphasis upon the intrinsic relationship between its structure and properties. Based on the calculated results, its molecular-orbital bonding structure was proposed. And a significant phenomenon of optical anisotropy was observed in the visible-light region. Furthermore, it was found that its slightly distorted crystal structure enhances the lone-pair impact of Bi 6s states, leading to the special optical properties and excellent photocatalytic activities.

Ultrathin and uniform Bi(2)WO(6) square nanoplates of ∼9.5 nm thickness corresponding to six repeating cell units were prepared in the presence of oleylamine using a hydrothermal route. The Bi(2)WO(6) nanoplates show great potential in the utilization of visible light energy to the highly efficient reduction of CO(2) into a renewable hydrocarbon fuel. On the one hand, the ultrathin geometry of the nanoplates promotes charge carriers to move rapidly from the interior to the surface to participate in the photoreduction reaction. This should also favor the improved separation of photogenerated electron and hole and a lower electron-hole recombination rate; on the other hand, the Bi(2)WO(6) square nanoplate is proven to provide the well-defined {001} facet for two dominantly exposed surfaces, which is a prerequisite for the high level of photocatalytic activity of CO(2) fixation.

An unprecedented, crystal facet-based CeO2 homojunction consisting of hexahedron prism-anchored octahedron with exposed prism surface of {100} facets and octahedron surface of {111} facets was fabricated through solution-based crystallographic-oriented epitaxial growth. The photocatalysis experiment reveals that growth of the prism arm on octahedron allows to activate inert CeO2 octahedron for an increase in phototocatalytic reduction of CO2 into methane. The pronounced photocatalytic performance is attributed to a synergistic effect of the following three factors: (1) band alignment of the {100} and {111} drives electrons and holes to octahedron and prism surfaces, respectively, aiming to reach the most stable energy configuration and leading to a spatial charge separation for long duration; (2) crystallographic-oriented epitaxial growth of the CeO2 hexahedron prism arm on the octahedron verified by the interfacial lattice fringe provides convenient and fast channels for the photogenerated carrier transportation between two units of homojuntion; (3) different effective mass of electrons and holes on {100} and {111} faces leads to high charge carrier mobility, more facilitating the charge separation. The proposed facet-based homojunction in this work may provide a new concept for the efficient separation and fast transfer of photoinduced charge carriers and enhancement of the photocatalytic performance.

The interaction of water with titanium dioxide surfaces has a vital role in many energy- and environment-related applications, such as dye-sensitized solar cell, photocatalytic or photoelectrochemical hydrogen production, and environmental purification. Structure and properties of water on the anatase TiO2(101) surface have been studied by using a combination of density functional theory and force field molecular dynamics. Owing to the amphotericity of this surface and the competition between water–water and water–substrate interactions, the structure and properties of water on the anatase TiO2(101) surface exhibited some peculiar and complicated features. The overall evolutionary process of interface formation has been obtained by investigating the coverage-dependent adsorption configuration and energy of water. The competition between water–water and water–substrate interaction results in the existence of a stable bilayer of water (Θ ≥ 2 ML) and an ice-like structure of water at higher coverage (Θ ≥ 3 ML). Both static and dynamic calculation results have showed that a highly ordered structure occurs in the first few water molecule layers, and this order decreases as one moves toward the bulk region. The electric fields across the interface and in the electric double layer were estimated to be about 10 and 2 eV, respectively. This study may provide new insight into the static and dynamic properties of the water–TiO2 interface and elucidate the reactions that occur on the TiO2 surface.

Photoelectrochemical water splitting is an attractive method to produce H(2) fuel from solar energy and water. Ion doping with higher valence states was used widely to enhance the photocurrent of an n-type oxide semiconductor. In this study, the different doping sites and the photoelectrochemical properties of Mo(6+), W(6+) and Sn(4+)-doped BiVO(4) were studied systematically. The results suggested that Mo(6+) or W(6+)-doped BiVO(4) had a much higher photocurrent while the photocurrent of Sn(4+)-doped BiVO(4) did not change obviously. Raman and XPS were used to identify the doping sites in the BiVO(4) crystal lattice. It was found that Mo or W substituted V sites but Sn did not substitute Bi sites. Results of theoretical calculation indicated that a higher formation energy and lower solubility of impurity ions led to serious SnO(2) segregation on the surface of the Sn(4+)-doped BiVO(4) thin film, which was the main reason for the poor performance of Sn-doped BiVO(4). The higher formation energy of Sn(4+) came from the large mismatch of ion radius and different outer shell electron distribution. These results can offer guidance in choosing suitable doping ions for other semiconductor photoelectrodes.

Interfacial charge separation and transfer are the main challenges of efficient semiconductor-based Z-scheme photocatalytic systems. Here, it is discovered that a Schottky junction at the interface between the BiVO 4 {010} facet and Au is an efficient electron-transfer route useful for constructing a high-performance BiVO 4 {010}-Au-Cu 2 O Z-scheme photocatalyst. Spectroscopic and computational studies reveal that hot electrons in BiVO 4 {010} more easily cross the Schottky barrier to expedite the migration from BiVO 4 {010} to Au and are subsequently captured by the excited holes in Cu 2 O. This crystal-facet-dependent electron shuttle allows the long-lived holes and electrons to stay in the valence band of BiVO 4 and conduction band of Cu 2 O, respectively, contributing to improved light-driven CO 2 reduction. This unique semiconductor crystal-facet sandwich structure will provide an innovative strategy for rational design of advanced Z-scheme photocatalysts.

Facilitated by TiO2 particles absorbing La3+ in hydrosol, La-doped TiO2 was prepared by a sol-hydrothermal method. Electron paramagnetic resonance and Brunauer−Emmett−Teller (BET) surface area analysis showed that the obtained La-doped anatase TiO2 surface provided a higher density of oxygen vacancies without a change in the BET surface area. A theoretical calculation was carried out to explain the generation mechanism of the increased oxygen vacancies. The results showed that the La-doped anatase TiO2 (101) surface tends to engender oxygen vacancies. The photoelectric conversion efficiency of dye-sensitized solar cells fabricated from 1 mol % La-doped TiO2 reached 6.72%, which gave an efficiency improved by 13.5% compared with that of the cells fabricated from pure TiO2. The improvement in the efficiency was ascribed to more dye absorbed on the surface of TiO2.