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    Effect of Nb and Ta substitution on donor electron transport and ultrafast carrier dynamics in anatase TiO2 thin films
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    Abstract:
    Substitution of Ti with Nb or Ta in epitaxial thin films of anatase TiO2 induces large and small polarons.
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    Substitution (logic)
    Due to the variable subjects and methods of solving problems in Higher Mathematics,substitution will not only flexibly develop the ways of problem solving,but also an effect of simplification.By reversing the examples in solving the problems of application,substitution,ways of incremental-substitution,tangle-substitution,double-substitution,unequal-substitution,ratio-substitution and so on,are discussed.
    Substitution (logic)
    Substitution effect
    Substitution method
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    Based on first principles within density-functional theory, we establish three models of N doped anatase TiO2, Sm doped anatase TiO2 and Sm-N codoped anatase TiO2 by using the plane-wave ultrasoft pseudopotential method. We calculate their densities of states, band structures and absorption spectra. Their results show that although the N doped anatase TiO2 takes the best redshift, the Sm-N codoped anatase TiO2 makes better lifespan of electron and the Sm-N codoped anatase TiO2 is more stable.
    Pseudopotential
    Citations (4)
    When we solve a maths problem,we should use the method of substitution to make the problem easier.It is the equivalent generation changes.Also it has three forms;triangle substitution,the radical substitution,overall substitution,and the equivalent generation substitution.
    Substitution (logic)
    Substitution method
    Substitution effect
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    Hydroxyapatite (HAp) was crystallized on anatase titanium dioxide (TiO 2 ) photocatalytic crystals or their thin films using of a pseudo‐body solution method, and electrochemical properties of the HAp‐adhered anatase TiO 2 photocatalytic surfaces were discussed. Decomposition rates of methylene blue were faster for the HAp‐adhered anatase TiO 2 photocatalysts, although specific surface areas were smaller than those for the commercial anatase TiO 2 ones. Surface potential dispersions on the HAp‐adhered anatase TiO 2 thin films before and after an ultraviolet light irradiation were measured by an atomic force microscopy. Changes in the color of leucocrystalviolet mixed in the HAp‐adhered anatase TiO 2 photocatalysts or the commercial anatase TiO 2 ones with experimental durations were compared. Movements of electrons from the anatase TiO 2 photocatalytic surfaces to the HAp, crystals and oxidizing reactions on the HAp‐adhered anatase TiO 2 photocatalytic surfaces in the dark were discussed on the basis of these experimental results.
    Titanium Dioxide
    Methylene blue
    Oxidizing agent
    In this study, CuO loaded on anatase TiO2 catalysts (CuO/anatase) with oxygen vacancies was synthesized via reduction treatments by NaHB4 and H2 (CuO/anatase-B, CuO/anatase-H), respectively. The characterizations suggest that different reduction treatments bring different concentration of oxygen vacancies in the CuO/anatase catalysts, which finally affect the CO catalytic performance. The CuO/anatase-B and CuO/anatase-H exhibit CO conversion of 90% at 182 and 198 °C, respectively, which is lower than what occurred for CuO/anatase (300 °C). The XRD, Raman, and EPR results show that the amount of the oxygen vacancies of the CuO/anatase-H is the largest, indicating a stronger reduction effect of H2 than NaHB4 on the anatase surface. The in situ DRIFTS results exhibit that the Cu sites are the adsorption sites of CO, and the oxygen vacancies on the anatase can active the O2 molecules into reactive oxygen species. According to the in situ DRIFTS results, it can be concluded that in the CO oxidation reaction, only the CuO/anatase-H catalyst can be carried out by the Mvk mechanism, which greatly improves its catalytic efficiency. This study explained the reaction mechanisms of CO oxidation on various anatase surfaces, which offers detailed insights into how to prepare suitable catalysts for low-temperature oxidation reactions.
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    TiO2 is as promising photocatalyst for environmental degradation of organic compounds and solar energy conversion. Commercial titania is a mixture of rutile and anatase phases, and, for as of yet unknown reasons, anatase is the photocatalytically more active form. In contrast to rutile, atomic-scale information on well-characterized anatase surfaces and their chemical properties was virtually absent at the beginning of this project. We have performed surface science investigations of anatase with the goal to understand, and ultimately control, the surface chemistry underlying its diverse applications. We have of (1) characterized all main crystallographic surface orientations of anatase, namely the (101), (100), (001), and (103) surfaces (2) have investigated the influence of surface imperfections such as defects and steps; (3) have investigated the influence of dopants on epitaxial (001) anatase films; and (3) have investigated the chemical and adsorption and reaction processes of simple molecules (water and methanol) on anatase surfaces. The experiments were performed in collaboration with Pacific Northwest National Laboratory (PNNL) using a variety of complementary surface science techniques. They have lead to a thorough characterization of this model system and have provided a more complete understanding of TiO2, which could possibly lead to improved efficiency in of photocatalytic applications.
    Rutile
    Characterization
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