Heterostructured α-Bi2O3/BiOCl Nanosheet for Photocatalytic Applications

Construction of functionalized In-based metal organic framework/BiOCl1-xIx Z-scheme heterojunction for efficient photocatalytic degradation of tetracycline: Performance and mechanism

The environmental implications of antibiotics have drawn widespread attention. Numerous monomer-based bismuth oxide halide catalysts have been extensively studied to remove tetracycline (TC) from aquatic environments. Integrating bismuth oxide halide composites with In-based metal organic framework (NH2-MIL-68(In)) might potentially serve as a novel strategy. By meticulously adjusting Cl and I within the composite bismuth halide oxide (B-x), a suite of purpose built heterojunctions (NMB-x) were synthesized, which were engineered to facilitate the efficient photodegradation of TC in simulated and actual aquatic environments. The incorporation of Z-scheme heterojunctions yielded a significant enhancement in photocatalytic responsiveness and charge carrier separation. Notably, NMB-0.3 demonstrated remarkable TC removal efficiency of 88.52 ± 3.05%, which is 3.74 times of B-0.3 within 90 min. The apparent quantum yield was also increased from 8.97% (B-0.3) to 19.68% (NMB-0.3). The removal of TC from natural water bodies was also assessed. Moreover, the photocatalyst concentration, assessed using response surface method, was found to show influential factors on TC removal. In addition, density functional theory (DFT) simulations were employed to identify vulnerable sites within TC. Intermediates and pathways in the photodegradation of TC have also been inferred. Furthermore, a comprehensive environmental toxicity assessment of representative intermediates demonstrated that these intermediates exhibited significantly reduced environmental toxicity compared to TC. This study provides a new approach to the design strategy of efficient and environmentally friendly MOF-based photocatalysts.

A swarm of helical photocatalysts with controlled catalytic inhibition and acceleration by magneto-optical stimuli

Highly persistent and toxic organic pollutants increasingly accumulate in freshwater resources, exacerbating the human water scarcity crisis. Developing novel microrobots with high catalytic performance, high mobility, and recycling capability integrated to harness energy from the surrounding environment to degrade pollutants effectively remains a challenge. Here, we report a kind of Spirulina (SP)-based magnetic photocatalytic microrobots with a substantially decreased band gap than that of pure photocatalysts, facilitating the generation of stable holes and electrons. Under sunlight irradiation, the degradation rate of rhodamine B (RhB) by the microrobots could be increased by 7.85 times compared with that of pure BiOCl, indicating its excellent photocatalytic performance. In addition, the microrobots can swarm in a highly controllable manner to the targeted regions and perform selective catalytic degradation of organic pollutants in specific areas by coupling effect of light and magnetic field. Importantly, the catalytic capability of the swarming microrobots can be activated by light stimulus whereas inhibited by magneto-optical stimuli, with a rate constant 2.15 times lower than that of pure light stimulation. The biohybrid and magneto-optical responsive microrobots offer a potential platform for selective pollutants catalysis at assigned regions in wastewater treatment plants.

Efficient Degradation of Rhodamine B with the BiOCl/Bi2Fe4O9 Heterojunction Photocatalyst

BiOCl/Bi2Fe4O9 photocatalyst was prepared by a coprecipitation-hydrothermal method. The heterojunction structure generated by the composite of BiOCl and Bi2Fe4O9 reduced the electron-hole recombination efficiency and improved the degradation rate of RhB. At 240 min, 20% BiOCl/Bi2Fe4O9 represented the excellent degradation effect on 10 mg/L RhB; the degradation efficiency reached 99.56%; and the reaction rate constant was 0.01534 min-1, which was 5.76 times and 6.06 times that of Bi2Fe4O9 and BiOCl, respectively. The main active substance of the photocatalytic degradation of dyes was superoxide radical O2-·. Five cycles of the experiment proved the relative stability of BiOCl/Bi2Fe4O9.

Outstanding photocatalytic nitrogen fixation performance of TiO2 QDs modified by Bi2O3/NaBiS2 nanostructures upon simulated sunlight

Nowadays, a promising material for NH₃ production under mild and safe conditions using heterogeneous photocatalysts is very important. In this regard, Bi₂O₃ and NaBiS₂ nanoparticles were combined with TiO₂ quantum dots (QDs) through a facile hydrothermal process. The TiO₂ QDs/Bi₂O₃/NaBiS₂ nanocomposites displayed excellent performance in the photofixation of nitrogen upon simulated sunlight. The NH₃ generation rate constant over the optimum nanocomposite was 10.2 and 3.3-folds higher than TiO₂ (P25) and TiO₂ QDs photocatalysts, respectively. The spectroscopic and electrochemical studies affirmed more effective segregation and transfer of photo-induced charge carriers within ternary nanocomposite, due to the developing tandem n-n-p heterojunctions, which led to more lifetime of charges. Moreover, the impacts of solvent, pH, electron scavenger, and lake of nitrogen molecules on the NH₃ generation were investigated. Finally, it was concluded that the TiO₂ QDs/Bi₂O₃/NaBiS₂ nanocomposite, with appealing features of more activity, high stability, and a facile one-pot synthesis method, is a promising photocatalyst in nitrogen fixation technology.

In situ synthesis of a Bi2O3 quantum dot decorated BiOCl heterojunction with superior photocatalytic capability for organic dye and antibiotic removal

As a decoration method, coupling a photocatalyst with semiconductor quantum dots has been proven to be an efficient strategy for enhanced photocatalytic performance. Herein, a novel BiOCl nanosheet decorated with Bi₂O₃ quantum dots (QDs) was first synthesized by a facile one-step in situ chemical deposition method at room temperature. The as-prepared materials were characterized by multiple means of analysis. The Bi₂O₃QDs with an average diameter of about 8.0 nm were uniformly embedded on the surface of BiOCl nanosheets. The obtained Bi₂O₃QDs/BiOCl exhibited significantly enhanced photocatalytic performance on the degradation of the rhodamine B and ciprofloxacin, which could be attributed to the band alignment, the photosensitization effect and the strong coupling between Bi₂O₃ and BiOCl. In addition, the dye photosensitization effect was demonstrated by the monochromatic photodegradation experiments. The radical trapping experiments and the ESR testing demonstrated the type II charge transfer route of the heterojunction. Finally, a reasonable photocatalytic mechanism based on the relative band positions was discussed to illustrate the photoreaction process. These findings provide a good choice for the design and potential application of BiOCl-based photocatalysts in water remediation.