Photocatalytic degradation of naproxen using single-doped TiO2/FTO and co-doped TiO2-VO2/FTO thin films synthesized by sonochemistry

Single-doped TiO2/FTO and co-doped TiO2-VO2/FTO thin films were prepared by sonochemistry and spray pyrolysis deposition on FTO substrates. The co-deposition of TiO2-VO2 on FTO significantly changed the morphological, structural, optical, and photocatalytical properties compared to the single-deposition. X-ray diffraction and HRTEM results showed polycrystalline film structures composed of SnO2-tetragonal from FTO, anatase-TiO2, rutile-TiO2, and monoclinic-VO2 phases. The co-deposition technique increases the particle size distribution by approximately two times compared to simple deposition. The single-doped TiO2/FTO thin film had a 15% higher bandgap than the co-doped TiO2-VO2/FTO thin film, and the electrical resistivity calculated from the van der Pauw method was 55.3 MΩ sq−1 for the TiO2-VO2/FTO co-doped thin film, 2.7 times lower than that obtained for the TiO2/FTO thin film. Single-doped TiO2/FTO and co-doped TiO2-VO2/FTO thin films presented pseudo-first-order reactions at pH 6.5, with kinetic constants of 0.026 and 0.015 min−1, respectively. This behavior is related to the production of inactive or less active aggregates by the addition of vanadium during the co-doping process, which led to lattice contraction, which encouraged the formation of the rutile phase rather than the anatase phase. However, the co-doped thin film can modify the metal-insulator transition compared to the single-doped TiO2/FTO thin film. Furthermore, co-deposition decreased the bandgap value by 16% compared to single-deposition thin film. In this sense, co-doped TiO2-VO2/FTO thin films inhibited the recombination of photogenerated carriers and the formation of reactive oxygen species involved in the photocatalytic degradation of naproxen.

Photocatalytic hydrogen generation using TiO2: a state-of-the-art review

This review is focusing on photocatalytic hydrogen (H2) production as a viable fuel. The limitations of different production methods for H2 generation and the importance of photocatalytic process are discussed, which renders this process as highly promising to meet the future energy crises. TiO2 is one of most effective material to generate the H2 via photocatalytic processes. Therefore, advantages of the catalyst over other semiconductors have been thoroughly analyzed. Starting from synthesis of TiO2 and factors affecting the whole process of photocatalytic H2 production have been discussed. Modifications for improvement in TiO2 and the photocatalytic reaction are critically reviewed as well as the mechanism of TiO2 modification has been described. Metal doping, non-metal doping, impurity addition and defect introduction processes have been analyzed and the comparison of experimental results is developed based on H2 production efficiency. A critical review of the literature from 2004 to 2021 concludes that H2 production as fuel using TiO2 photocatalytic method is efficient and environment friendly, which have potential for practical applications for H2 generation.