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To design solid solution is an effective strategy for functional materials. The complex electron correlation and non‐equilibrium atomic interaction are the primary factors to impact the macro‐/micro‐structure and application performances of solid solution. Hence, this article concentrates on the stable crystal structure and the corresponding electronic structure of Ru1−xTixO2 solid solution by using density functional theory calculations. Based on analyzing the atomic interaction between solute and solvent atoms, the most stable supercell models for the specific solid solubility were obtained. In Ru1−xTixO2 solid solution, solute (and solvent) atoms preferentially arrange along the [110] direction, and tend to occupy the nearest sites of identical atoms, to arrange the symmetric ordered substitution configurations. Using the subregular solution model, the mixing enthalpy can be represented by the following expression: ΔHf=XTiO2XRuO235.30XTiO2+23.08XRuO2. The calculated phase diagram is consistent with the experimental results. Thus, the calculated results in this article are reliable and can provide more meaningful information. In the cases of Ru‐rich solid solutions, the metastable phase exists in the range of x < 0.27; while in the cases of Ti‐rich solid solutions, the metastable phase exists in the range of x > 0.81. Interestingly, the electron density of Ru1−xTixO2 solid solutions at Fermi level has a stronger dependence on the Ru composition, which intrinsically influences its electronic structure and optical properties. According to the basic application principle, Ru1−xTixO2 solid solutions with lower (x < 0.27) and higher (x > 0.81) solid solubility could act as suitable candidate for the applications in field electrochemistry and photocatalysis. [ABSTRACT FROM AUTHOR]

In the field of photocatalysis, constructing hetero-structures is an efficient strategy to improve quantum efficiency. However, a lattice mismatch often induces unfavorable interfacial states that can act as recombination centers for photo-generated electron–hole pairs. If the hetero-structure's components have the same crystal structure, this disadvantage can be easily avoided. Conversely, in the process of loading a noble metal co-catalyst onto the TiO2 surface, a transition layer of noble metal oxides is often formed between the TiO2 layer and the noble metal layer. In this article, interfacial properties of hetero-structures composed of a noble metal dioxide and TiO2 with a rutile crystal structure have been systematically investigated using first-principles calculations. In particular, the Schottky barrier height, band bending, and energy band alignments are studied to provide evidence for practical applications. In all cases, no interfacial states exist in the forbidden band of TiO2, and the interfacial formation energy is very small. A strong internal electric field generated by interfacial electron transfer leads to an efficient separation of photo-generated carriers and band bending. Because of the differences in the atomic properties of the components, RuO2/TiO2 and OsO2/TiO2 hetero-structures demonstrate band dividing, while RhO2/TiO2 and IrO2/TiO2 hetero-structures have a pseudo-gap near the Fermi energy level. Furthermore, NMO2/TiO2 hetero-structures show upward band bending. Conversely, RuO2/TiO2 and OsO2/TiO2 hetero-structures present a relatively strong infrared light absorption, while RhO2/TiO2 and IrO2/TiO2 hetero-structures show an obvious absorption edge in the visible light region. Overall, considering all aspects of their properties, RuO2/TiO2 and OsO2/TiO2 hetero-structures are more suitable than others for improving the photocatalytic performance of TiO2. These findings will provide useful information for understanding the role and effects of a noble metal dioxide as a transition layer between a noble metal co-catalyst and a TiO2 photocatalyst. [ABSTRACT FROM AUTHOR]

Noble metals supported on TiO2 surfaces have shown extraordinary photocatalytic properties in many important processes such as hydrogenation, water splitting, degradation of hazards, and so on. Using density functional theory calculations, this work has systematically investigated the microstructure and electronic structure of three different Au9 isomers loaded on anatase TiO2(001) surface. The calculated results show that the interaction between the Au9 cluster and the TiO2 support is closely related to the adsorption site and the stability of the Au9 cluster in the gas phase. The adsorption energy of the 2D configuration is larger than that of the 3D configuration of the Au9 cluster, owing to the stronger interactions between more adsorption sites. The stable adsorption site for Au9 clusters deposited on the anatase TiO2(001) surface tends to be the O2c–O2c hollow site. The presentation of the MIGS of the Au9 cluster, the disappearance of surface states of the TiO2(001) surface, and the shifting of the Fermi level from the top of the valence band to the bottom of the conduction band suggest strong interactions between the Au9 clusters and the TiO2(001) surface. Importantly, the electron transfer from the Au9 clusters to the TiO2 support occurs mainly through Au–O2c interactions, which are mainly localized at the contact layer of the Au9 clusters. These conclusions are useful to understand various physical and chemical properties of noble metal clusters loaded onto an oxide surface, and helpful to design novel metal/semiconductor functional composite materials and devices. [ABSTRACT FROM AUTHOR]

Composite photocatalysts with hetero-structures usually favor the effective separation of photo-generated carriers. In this study, BiOIO3 was chosen to form a hetero-structure with BiOI, due to its internal polar field and good lattice matching with BiOI. The interfacial properties and band offsets were focused on and analyzed in detail by DFT calculations. The results show that the charge depletion and accumulation mainly occur in the region near the interface. This effect leads to an interfacial electric field and thus, the photo-generated electron–hole pairs can be easily separated and transferred along opposite directions at the interface, which is significant for the enhancement of the photocatalytic activity. Moreover, according to the analysis of band offsets, the vertical BiOI/BiOIO3 belongs to the type-II hetero-structure, while the in-plane BiOI/BiOIO3 belongs to the type-I hetero-structure. The former type of hetero-structure has more favorable effects to enhance the photocatalytic activity of BiOI than that of the latter type of hetero-structure. In the case of the vertical BiOI/BiOIO3 hetero-structure, photo-generated electrons can move from the conduction band of BiOI to that of BiOIO3, while holes can move from the valence band of BiOIO3 to that of BiOI under solar radiation. In addition, the introduced internal electric field functions as a selector that can promote the separation of photo-generated carriers, resulting in the higher photocatalytic quantum efficiency. These findings illustrate the underlying mechanism for the reported experiments, and can be used as a basis for the design of novel highly efficient composite photocatalysts with hetero-structures. [ABSTRACT FROM AUTHOR]