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In this study, we explored the effect of either Nb or Sc doping at a concentration range of 0.0–1.0 at.% on the physical–chemical and photoelectrochemical behavior of TiO2 anatase electrodes. This behavior was characterized by work function, flat band potential, donor density, spectral dependence of photocurrent and stationary photocurrent measurements. All experimental results are interpreted in terms of the formation of the shallow delocalized polaron states in the case of Nb doping and deep acceptor states induced by Sc doping on TiO2 anatase. [ABSTRACT FROM AUTHOR]

Individual (FTO/Cu2O and FTO/CuCo2O4) and heterostructured (FTO/BiVO4/Cu2O, FTO/BiVO4/CuCo2O4, and FTO/CuCo2O4/Cu2O) electrodes were successfully formed using the electrodeposition method on copper-containing compounds. The morphology of the synthesized electrode systems, which affect the electrochemical properties, was determined. A comparative study of the electrochemical and photoelectrochemical properties of the individual and heterostructured electrodes showed that the modification of the BiVO4 electrode surface with Cu2O and CuCo2O4 oxides led to a significant increase in its efficiency as a photoanode. The deposition of Cu2O nanoclusters onto CuCo2O4 nanoflakes increased the electrochemical stability of the electrode while maintaining its high capacitance. [ABSTRACT FROM AUTHOR]

Two series of Sc3+- and Nb5+-doped TiO2 (rutile) samples were synthesized and characterized by SEM, ICPE spectroscopy, XPS, and BET methods. Photocatalytic activity of the doped TiO2 samples was tested in photocatalytic degradation of phenol. Dependences of the photocatalytic activities of the doped TiO2 samples demonstrate a volcano-like behavior, indicating the existence of the optimal dopant concentrations to achieve the highest activity of photocatalysts. Remarkably, the optimal dopant concentrations correspond to the extrema observed in work function dependences on the dopant concentrations, that indicates a significant energy redistribution of the defect states within the bandgap of TiO2. Such a redistribution of the defect states is also proven by the alterations of the optical and EPR spectra of the intrinsic Ti3+ defect states in TiO2. Based on the analysis of the experimental results, we conclude that both Sc3+ and Nb5+ doping of TiO2 results in redistribution of the defect states and the optimal dopant concentrations correspond to the defect structures, which are ineffective in charge carrier recombination, that ultimately leads to the higher photocatalytic activity of doped TiO2. [ABSTRACT FROM AUTHOR]

Carbon monoxide adsorption of LiX-1.0 zeolite ([Li96.(Si96Al96O384)]-FAU, Si/Al = 1.0) was studied by means of FT-IR spectroscopy at a wide temperature range to investigate the nature and properties of adsorption sites. It is shown that the existence of two slightly different adsorption centers in LiX-1.0 zeolite at room and low temperatures.

Here, we report the results of comparative studies of the photostimulated hydrophilic behavior of heterostructured TiO2/BiVO4 and ZnO/BiVO4, and monocomponent TiO2 and ZnO nanocoating surfaces. The chemical composition and morphology of the synthesized nanocoatings were characterized by XPS, SEM, and AFM methods. The electronic energy structure of the heterostructure components (band gap, top of the valence band, bottom of the conduction band, and Fermi level position) was determined on the basis of experimental results obtained by XPS, UV-V absorption spectroscopy and Kelvin probe methods. According to their electronic energy structure, the ZnO/BiVO4 and TiO2/BiVO4 heterostructures correspond to type I and type II heterostructures, respectively. The difference in the type of heterostructures causes the difference in the charge transfer behavior at heterojunctions: the type II TiO2/BiVO4 heterostructure favors and the type I ZnO/BiVO4 heterostructure prevents the photogenerated hole transfer from BiVO4 to the outer layer of the corresponding metal oxide. The results of the comparative studies show that the interaction of the photogenerated holes with surface hydroxy-hydrated multilayers is responsible for the superhydrophilic surface conversion accompanying the increase of the surface free energy and work function. The formation of the type II heterostructure leads to the spectral sensitization of the photostimulated surface superhydrophilic conversion. [ABSTRACT FROM AUTHOR]

The effect of a Cu2O substrate on the photoinduced alteration of the hydrophilicity of TiO2 and ZnO surfaces was studied. It was demonstrated that the formation of heterostructures Cu2O/TiO2 and Cu2O/ZnO strongly changed the direction of the photoinduced alteration of surface hydrophilicity: while both TiO2 and ZnO demonstrate surface transition to superhydrophilic state under UV irradiation and no significant alteration of the surface hydrophilicity under visible light irradiation, the formation of Cu2O/TiO2 and Cu2O/ZnO heterostructures resulted in photoinduced decay of the surface hydrophilicity caused by both UV and visible light irradiation. All observed photoinduced changes of the surface hydrophilicity were compared and analyzed in terms of photoinduced alteration of the surface free energy and its polar and dispersive components. Alteration of the photoinduced hydrophilic behavior of TiO2 and ZnO surfaces caused by formation of the corresponding heterostructures with Cu2O are explained within the mechanism of electron transfer and increasing of the electron concentration on the TiO2 and ZnO surfaces. [ABSTRACT FROM AUTHOR]

In recent years many works are aimed at finding a method of controllable switching between hydrophilicity and hydrophobicity of a surface. The hydrophilic surface state is generally determined by its energy. Change in the surface energy can be realized in several different ways. Here we report the ability to control the surface wettability of zirconium dioxide nano-coatings by changing the composition of actinic light. Such unique photoinduced hydrophilic behavior of ZrO 2 surface is ascribed to the formation of different active surface states under photoexcitation in intrinsic and extrinsic ZrO 2 absorption regions. The sequential effect of different actinic lights on the surface hydrophilicity of zirconia is found to be repeatable and reversibly switchable from a highly hydrophilic state to a more hydrophobic state. The observed light-controllable reversible and reproducible switching of hydrophilicity opens new possible ways for the application of ZrO 2 based materials.

An experimental technique is developed for spectral studies of ice films deposited at 77 K onto the ZnSe inner windows of a cell, so that the spectra could be registered in the presence of gaseous adsorbate. Pure H2O or D2O ice as well as HCN/D2O and ND3/D2O mixed icy films with different dopant/water ratios (1:10, 1:5, and 1:1) were investigated. The surface area of ice deposited at 77 K H2O estimated from adsorption measurements was about 160 m2/g. Bands of dangling hydroxyl groups disappear on raising the temperature up to 130-160 K when the changes of bulk absorption provide evidence for a phase transition from amorphous to polycrystalline ice. Surface properties of icy films were characterized by low-temperature adsorption of CO and CHF3. Insertion of small doses of HCN or ammonia does not change the acid/base strength of dangling hydroxyl groups or coordinately unsaturated surface oxygen atoms, but it changes the proportion between the concentrations of these sites as compared with pure water ice. For high dopant concentrations, the dangling hydroxyls were not observed, and the dominant adsorption sites for CO are likely to be the unsaturated oxygen atoms, while serious structural changes occur in the bulk of ices.