Layered Perovskite Pb2Bi4Ti5O18 for Excellent Visible Light-Driven Photocatalytic NO Removal

Bi2WO6 quantum dots with oxygen vacancies combined with g-C3N4 for NO removal

Semiconductor materials have been used for photocatalytic degradation since they were discovered to be useful for photocatalytic degradation. Many studies have been researched to improve the efficiency of photocatalytic degradation. Among them, the introduction of vacancies to improve the photocatalytic efficiency has been verified to be a more feasible method. In this study, we combined two-dimensional (2D) graphite carbon nitride (g-C₃N₄) nanosheets with oxygen-containing vacancy zero-dimensional (0D) Bi₂WO₆ (BWO-OV) quantum dots to prepare 2D-0D g-C₃N₄/Bi₂WO₆-OV composite catalyst. The use of Bi₂WO₆ containing oxygen vacancies enhanced the absorption of light and increased the generation of photogenerated carriers. In addition, the formation of heterojunction and the vacancy structure of Bi₂WO₆ promote the life of photogenerated carriers and improve the catalytic effect of the catalyst. This structure shows high efficiency in removing low concentration (0.5 ppm) of nitric oxide (NO) at room temperature. The efficiency of the composite catalyst is much higher than g-C₃N₄ or BWO-OV, and better than the composite g-C₃N₄/Bi₂WO₆ without oxygen vacancies. When applied to NO removal, the composite g-C₃N₄/Bi₂WO₆-OV-10 showed the best catalytic activity which was up to 61.2%. At the same time, five cycles of experiments show that the material has excellent stability.

Visible-light-driven photocatalytic disinfection mechanism of Pb-BiFeO3/rGO photocatalyst

While the visible-light-driven photocatalytic disinfection techniques for drinking water have recently attracted tremendous attentions, it is necessary to further improve the solar energy utilization efficiency. In this study, we synthesized Pb-BiFeO₃ photocatalysts doped with different amounts of reduced graphene oxide (Pb-BiFeO₃/rGO). The photocatalytic disinfection efficiencies toward gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus) were evaluated under visible-light irradiation (λ ≥ 400 nm). The results indicated that Pb-BiFeO₃ with 0.5 wt% rGO (Pb-BiFeO₃/0.5% rGO) exhibited the highest disinfection efficiency. Complete inactivation was reached within 30 min and 90 min for E. coli and S. aureus, respectively. The transcriptomic analysis results indicated that Pb-BiFeO₃/0.5% rGO deregulates the genes in E. coli cells that are involved in the cell membrane damage and oxidative stress responses. This was validated by the cell leakage of nucleic acids or proteins, transmission electron microscopy images of the bacteria, and the disinfection efficiency decrease caused by the introduction of scavenger of hydroxyl radical (HO•). Metal ions (Pb²⁺, Bi²⁺, and Fe³⁺) released from the photocatalysts did not contribute to the disinfection process. For the first time, our results elucidated that the photocatalytic disinfection mechanism of Pb-BiFeO₃/rGO toward E. coli was mainly associated with oxidative stress due to HO• generation and the loss of membrane integrity from direct contact with the photocatalyst. After four consecutive cycles, the Pb-BiFeO₃/0.5% rGO photocatalyst exhibited a strong antibacterial efficiency. The excellent disinfection efficiency and stability of Pb-BiFeO₃/0.5% rGO suggests that this photocatalyst shows great potential for drinking water disinfection.

Novel High Efficiency Layered Oxide Photocatalyst Li2SnO3 for Rhodamine B and Tetracycline Degradation

The use of a layered Li2SnO3 material as an efficient photocatalyst for the degradation of environmental pollutants (Rhodamine B and tetracycline) was investigated. The structure and morphology of the material were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Optical measurements demonstrated that Li2SnO3 was a UV-light-responsive material with a band gap of 3.71 eV. The maximum kinetic rate constants of photocatalytic degradation of Rhodamine B and tetracycline solutions were 0.0155 min−1 and 0.0406 min−1 · L/mg, respectively, when exposed to UV-light irradiation within 120 min. Trapping experiments demonstrated that holes ( h + ) , hydroxyl radical ( · O H ) and superoxide radical ( · O 2 − ) were the dominant active species during the degradation of Rhodamine B and tetracycline. Theoretical band structure calculations revealed that Li2SnO3 was a direct gap semiconductor with a large m h * / m e * value (4.7) near the band edge. Partial charge density near the top of the valence band indicated that the photocatalytic oxidation reaction occurred largely on the O-2p states. The excellent photocatalytic performance was attributed to the synergistic effect of the layered crystal structure and large m h * / m e * . This work represents an important contribution to the design and optimization of efficient oxide photocatalysts with layered crystal structures for environmental remediation.