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Facet engineering is a new method of materials design with considerable potential for many technological applications. The present work uses DFT calculations to understand how this strategy can be used to accelerate the silanization of tetraethyl orthosilicate (TEOS) on the surface of ceria (CeO2), which is a key technology in biomedical and other fields. Cubic CeO2nanoparticles with exposed {100} facets are shown to represent the most favorable morphology for silanization owing to (1) the facilitated adsorption of TEOS on these facets compared to the {110} and {111} facets and (2) spontaneous breakage of the Si–O bonds of TEOS, which is found to be the rate-determining step for silanization of CeO2. The favorable adsorption on the {100} facets arises from its superior structural and electronic properties as well as higher reactivity, which are attributed to its more open arrangement of the surface atoms and consequently reduced steric hindrance, higher density of dangling bonds and surface active sites, and the larger difference in Mulliken charges between the surface and bulk atoms.

The present work reports data for the mineralogical and chemical properties of anatase thin films individually doped or codoped with chromium and vanadium, fabricated by sol–gel spin coating on glass substrates and annealing at 450 °C for 2 h. X-ray photoelectron spectroscopy data indicated the presence of Ti4+, Ti3+, Cr3+, and possibly Cr4+in the Cr-doped thin films; Ti4+, Ti3+, V3+, V4+, and possibly V5+in the V-doped thin films; and Ti4+, Ti3+, Cr3+, Cr4+, V3+, V4+, and possibly V5+in the codoped thin films. While the thermodynamically stable valences Ti4+, Cr3+, and V5+would be expected to have formed, the presence of the nonequilibrium valences Ti3+, Cr4+, V3+, and V4+is considered to have resulted from intervalence charge transferfor the Cr-doped and V-doped systems but from multivalence charge transfer(MVCT) for the codoped system. The latter phenomenon, which is introduced as a new conceptual term, describes the nature of the mutual exchange of electrons during valence changes of both dopant (Cr, V) and matrix (Ti) ions during annealing. In the present case, MVCT appears to be a transient metastable condition that acts during annealing, but subsequent UV irradiation can alter its effects.

Bismuth-based metal oxide compounds are promising candidates as novel photocatalysts for environmental remediation. However, their low quantum efficiencies and rapid electron-hole recombination times have hindered their uptake for photocatalytic applications. The present work reports an investigation of the effects of variable Bi/Ti ratio during hydrothermal synthesis on the phase assemblage, nanostructure, surface chemistry, band gap, and photocatalytic performance. Increasing Ti concentration resulted in variations in characteristics and properties according to the sequential formation of the principal phases α-Bi2O3(BO), Bi4Ti3O12(BTO), and (Na0.5Bi0.5)TiO3(NBT). Samples fabricated with precursors having a Bi/Ti ratio of 12/12 exhibited the highest methylene blue (MB) photodegradation rate of 92% under UV irradiation for 2 h. This excellent photocatalytic performance is attributed to the formation of an NBT/BTO heterojunction with advantageous band alignment.