3 research outputs found

    Enhancement of Activity of Activated Carbon Fiber for Electro-Fenton Process by Loading it with SiO<sub>2</sub> having Tunable Hydrophobic/Hydrophilic Moieties

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    Electro-Fenton (EF) process is promising for achieving satisfactory oxidation of organic contaminants. However, the sluggish kinetics of in situ production of H2O2 and slow rate of Fe2+ regeneration remain its limitations. In this work, SiO2 with tunable methyl and hydroxyl moieties on the surface (MxOHSiO2; x denotes the mass ratio of diethoxydimethylsilane to tetraethyl orthosilicate) was successfully loaded onto activated carbon fiber (ACF) to construct an ACF-supported cathode (MxOHSiO2/ACF) for the degradation of bisphenol A (BPA). The MxOHSiO2/ACF exhibited substantially higher activity than bare ACF in the EF process. The removal of BPA proceeded most rapidly with M0.75OHSiO2/ACF with an initial pH of 3.0, an electrolyzing voltage of 20 V, and an Fe2+ dosage of 0.5 mM. The mineralization efficiency was 79.3% after 360 min, with the complete disappearance of BPA recorded at 60 min during the EF process. In addition, the M0.75OHSiO2/ACF catalytic electrode remained stable for five successive cycling tests. Because of the synergistic effect of the hydrophobic methyl moiety and electron-rich hydroxyl moiety on SiO2, the H2O2 electro-generation and Fe2+ regeneration at M0.75OHSiO2/ACF were simultaneously improved. This work provides an effective strategy for the application of EF technology in future

    Photocatalytic Reduction of CO<sub>2</sub> in Aqueous Solution on Surface-Fluorinated Anatase TiO<sub>2</sub> Nanosheets with Exposed {001} Facets

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    Photocatalytic reduction of carbon dioxide can activate chemically inert carbon dioxide by the use of renewable energy. In the present work, the main products of photocatalytic reduction of CO<sub>2</sub> in aqueous TiO<sub>2</sub> suspensions were found to be methane, methanol, formaldehyde, carbon monoxide, and H<sub>2</sub>. Anatase TiO<sub>2</sub> catalysts with various morphologies, such as nanoparticle, nanotube, and nanosheet, were synthesized through a hydrothermal method. The TiO<sub>2</sub> nanosheets were more active than the nanotubes or nanoparticles in the reduction of CO<sub>2</sub> in aqueous solution. This is because the photogenerated carriers prefer to flow to the specific facets. The TiO<sub>2</sub> sheet with high-energy exposed {001} facets facilitates the oxidative dissolution of H<sub>2</sub>O with photogenerated holes, leaving more photogenerated electrons available for the reduction of CO<sub>2</sub> on {101} facets. Moreover, surface fluorination promotes the formation of Ti<sup>3+</sup> species, which is helpful in the reduction of CO<sub>2</sub> to CO<sub>2</sub><sup>–</sup> and in extending the lifetime of photogenerated electron–hole pairs. The optimum ratio of exposed {001} to {101} facets for surface-fluorinated TiO<sub>2</sub> nanosheets was found to be ∼72:28, which corresponds to an initial F/Ti ratio of 1. From our analysis of the effect of adding of known intermediates on the photocatalytic reduction of CO<sub>2</sub>, we propose that the photocatalytic reduction of CO<sub>2</sub> with H<sub>2</sub>O on surface-fluorinated TiO<sub>2</sub> nanosheets proceeds via a mechanism involving generation of hydrogen radicals and carbon radicals

    Photocatalytic Degradation of Toluene by a TiO<sub>2</sub> p‑n Homojunction Nanostructure

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    The development of catalysts for the treatment of volatile organic compounds (VOCs) by photocatalytic oxidation is very important for treating industrial flue gases. Although defect engineering has been developed into an effective method to improve the photocatalytic activity of TiO2 semiconductor materials, few holistic studies have been performed on the structure and properties of TiO2. Herein, a one-step hydrothermal method was used to synthesize three types of nanoscale TiO2 (p-TiO2 with only Ti vacancies, n-TiO2 with only O vacancies, and pn-TiO2 with dual Ti/O vacancies) for the photocatalytic removal of gaseous toluene to determine the relationship between the redox capacity of the electron–hole pairs and the type of conductive semiconductors. It was found that pn-TiO2 exhibited a higher gaseous toluene conversion (99.6%) within 2 h, with 2.8-fold faster photocatalytic kinetics than p-TiO2 and 1.26-fold faster than n-TiO2. Based on the results of an experimental study and theoretical calculations, it was verified that the dual vacancies in pn-TiO2 enabled the valence and conduction bands to be fully exploited to generate ·OH and ·O2–, respectively, for the synergistic degradation of gaseous toluene. Because of the characteristics of the p-n homojunction, charge transfer and separation were efficiently increased in pn-TiO2, resulting in the effective treatment of gaseous toluene. In addition, after five cycles of photocatalytic degradation of toluene, the degradation rate by pn-TiO2 remained over 80%, indicating potential applications for pn-TiO2. In this study, a rational pathway is demonstrated for photocatalysts containing dual vacancies to degrade toluene based on the synergistic effect of free radicals, providing an inspiration for designing materials with vacancies or homojunctions and providing means of eliminating VOCs in practical applications
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