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    Photocatalytic activation of TiO2 under visible light using Acid Red 44
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    Ag modification has been demonstrated to be an efficient strategy to improve the photocatalytic performance of TiO2 photocatalysts. However, the previous studies about the Ag modification are only restricted to the surface loading of metallic Ag or Ag(I) doping, investigations have seldom been focused on the simultaneously deposited and doped Ag/Ag(I)-TiO2 photocatalyst. In this study, Ag/Ag(I)-TiO2 photocatalyst was prepared by a facile impregnated method in combination with a calcination process (450 °C) and the photocatalytic activity was evaluated by the photocatalytic decomposition of methyl orange and phenol solutions under both UV- and visible-light irradiation, respectively. It was found that Ag(I) doping resulted in the formation of an isolated energy level of Ag 4d in the band gap of TiO2. On the basis of band-structure analysis of Ag/Ag(I)-TiO2 photocatalyst, a possible photocatalytic mechanism was proposed to account for the different UV- and visible-light photocatalytic activities. Under visible-light irradiation, the isolated energy level of Ag 4d contributes to the visible-light absorption while the surface metallic Ag promotes the effective separation of the following photogenerated electrons and holes in the Ag/Ag(I)-TiO2 nanoparticles, resulting in a higher visible-light photocatalytic activity than the one-component Ag-modified TiO2 (such as Ag(I)-TiO2 and Ag/TiO2). Under UV-light irradiation, the doping energy level of Ag(I) ions in the band gap of TiO2 acts as the recombination center of photogenerated electrons and holes, leading to a lower photocatalytic performance of Ag-doped TiO2 (such as Ag/Ag(I)-TiO2 and Ag(I)-TiO2) than the corresponding undoped photocatalysts (such as Ag/TiO2 and TiO2). Considering the well controllable preparation of various Ag-modified TiO2 (such as TiO2, Ag/TiO2, Ag(I)-TiO2, and Ag/Ag(I)-TiO2), this work may provide some insight into the smart design of novel and high-efficiency photocatalytic materials.
    Visible spectrum
    Methyl orange
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    The simple synthesis of TiO2 and improved visible-light photocatalytic performance of TiO2 have been the goal of researchers. When compared to pure phase TiO2, mixed-phase TiO2 nanoparticles with oxygen vacancies can aid in lowering the band gap and carrier recombination rate, which improves the performance of visible light photocatalysis. In this study, three different acids were separately applied in the hydrothermal synthesis of TiO2 nanoparticles without any post-heat treatment. The reaction was carried out at a relatively low temperature not exceeding \(140^{\circ}\)C. Under the visible light illumination-assisted photocatalytic degradation of methyl orange in water, the TiO2 nanoparticles obtained from HCl (H-TiO2) and CH3COOH (A-TiO2) showed stable photocatalysis performance for increasing the cycles up to ten times while only five cycles for TiO2 nanoparticles obtained by HNO3-assisted (N-TiO2). Compared with efficiencies of N-TiO2 nanoparticles, H-TiO2 and A-TiO2 showed superior efficiencies and have excellent photocatalytic performances when assisting in the degradation of methyl orange in water under visible light illumination. The high visible-light photocatalytic performance and the simple acid-assisted synthesis of the H-TiO2 and A-TiO2 nanoparticles will promote the industrial application.
    Visible spectrum
    Methyl orange
    A photocatalyst foam is developed by growing high-density CdS microspheres on Ni 2 P nanolayer-modified Ni foam (NF) for efficient visible-light-driven photocatalytic H 2 evolution.
    Visible spectrum
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    In terms of the UV irradiating directions, photocatalysis with TiO2 thin films can be divided into two types, the background irradiated photocatalysis and the foreground irradiated one. Comparatively, background irradiated photocatalysis has an advantage of avoiding the UV light attenuation which foreground irradiated one suffers when the light is going through the solution. In this article, the influence of the thickness of the films, the wavelength of light source and non-uninformly doping with V on the photocatalytic efficiency of the catalyst in case of background irradiated photocatalysis is investigated, and simultaneously it is compared with foreground irradiated one. The results show that in case of background irradiated photocatalysis there is an optimal thickness of the film according to the wavelength of the light source that is limited in the range of 300 nm to 388 nm, which is quite different from foreground irradiated one. But in both cases, the catalyst's photocatalytic activities are improved by non-uniformly doped with V.
    Visible spectrum
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