One-Pot Synthesized Visible Light-Driven BiOCl/AgCl/BiVO4 n-p Heterojunction for Photocatalytic Degradation of Pharmaceutical Pollutants

BiOCl Heterojunction photocatalyst: Construction, photocatalytic performance, and applications

BiOCl semiconductors have attracted extensive amounts of attention and have substantial potential in alleviating energy shortages, improving sterilization performance, and solving environmental issues. To improve the optical quantum efficiency of layered BiOCl, the lifetimes of photogenerated electron-hole pairs, and BiOCl reduction capacity. During the past decade, researchers have designed many effective methods to weaken the effects of these limitations, and heterojunction construction is regarded as one of the most promising strategies. In this paper, BiOCl heterojunction photocatalysts designed and synthesized by various research groups in recent years were reviewed, and their photocatalytic properties were tested. Among them, direct Z-scheme and S-scheme photocatalysts have high redox potentials and intense redox capabilities. Hence, they exhibit excellent photocatalytic activity. Furthermore, the applications of BiOCl heterojunctions for pollutant degradation, CO₂ reduction, water splitting, N₂ fixation, organic synthesis, and tumor ablation are also reviewed. Finally, we summarize research on the BiOCl heterojunctions and put forth new insights on overcoming their present limitations.

Photocatalytic removal of pharmaceutical water pollutants by TiO2 - Carbon dots nanocomposites: A review

Pharmaceuticals are becoming increasingly more relevant water contaminants, with photocatalysts (such as TiO₂) being a promising approach to remove these compounds from water. However, TiO₂ has poor sunlight-harvesting capacity, low photonic efficiency, and poor adsorption towards organic pollutants. One of the emerging strategies to enhance the photocatalytic performance of TiO₂ is by conjugating it with fluorescent carbon dots. Herein, we performed a critical review of the development of TiO₂ - carbon dots nanocomposites for the photocatalytic removal of pharmaceuticals. We found that carbon dots can improve the photocatalytic efficiency of the resulting nanocomposites, mostly due to increasing the adsorption of organic pollutants and enhancing the absorption in the visible range. However, while this approach shows significant promise, we also identified and discussed several aspects that need to be addressed before this strategy could be more widely used. We hope that this review can guide future studies aiming to the development of enhanced photocatalytic TiO₂ - carbon dots nanocomposites.

A Novel BiOCl Based Nanocomposite Membrane for Water Desalination

In this study, BiOCl based nanocomposites were used as photocatalytic membranes for a simulated study on water desalination in reverse osmosis membrane systems. Through molecular dynamic simulation, the molecular structure of BiOCl, BiOCl/Ag2S and BiOCl/Bi2O3 heterojunctions were designed and their electronic properties, mechanical properties, and membrane performance for water desalination were evaluated for the first time. The molecular structure was created, and a geometry optimization task was used to optimize it. Material Studio 2019 CASTEP was used for simulation of the electronic and mechanical properties and water desalination was performed by ReaxFF software under pressures between 0 and 250 MPa. The novel BiOCl based nanocomposites showed improved electronic and mechanical properties and, most importantly, improvements in salt rejection and water permeability as compared to well-known materials such as graphene and MoS2. BiOCl and BiOCl/Ag2S had a bandgap around two, which is the ideal bandgap for semiconductor photocatalysts. A salt rejection of 98% was achieved under an applied pressure of 10 MPa. Salt rejection was higher for BiOCl/Bi2O3, while water permeability was higher for BiOCl/Ag2S. The monolayer BiOCl was unstable under pressures higher than 50 MPa, but the mechanical stability of BiOCl/Ag2S increased twofold and increased fourfold for BiOCl/Bi2O3, which is even higher than MoS2. However, between the three nanocomposites, BiOCl/Ag2S was found to be the most ideal photocatalytic nanocomposite membrane.

TiO2 nanofibres decorated with green-synthesized PAu/Ag@CQDs for the efficient photocatalytic degradation of organic dyes and pharmaceutical drugs

Organic pollutants such as dyes and pharmaceutical drugs have become an environmental menace, particularly in water bodies owing to their unregulated discharge. It is thus required to develop an economically viable and environment-friendly approach for their degradation in water bodies. In this study, for the first time, we report green route-synthesized plasmonic nanostructures (PM-CQDs (where M: Au and Ag)) decorated onto TiO2 nanofibers for the treatment of toxic dye- and pharmaceutical drug-based wastewater. PM-CQDs are efficaciously synthesized using carbon quantum dots (CQDs) as the sole reducing and capping agent, wherein CQDs are derived via a green synthesis approach from Citrus limetta waste. The characteristic electron-donating property of CQDs played a key role in the reduction of Au3+ to Au0 and Ag+ to Ag0 under visible light irradiation to obtain PAu-CQDs and PAg-CQDs, respectively. Thus, the obtained CQDs, PAu-CQDs, and PAg-CQDs are loaded onto TiO2 nanofibers to obtain a PM-CQD/TiO2 nanocomposite (NC), and are further probed via transmission electron microscopy, scanning electron microscopy and UV-visible spectrophotometry. The degradation of organic pollutants and pharmaceutical drugs using methylene blue and erythromycin as model pollutants is mapped with UV-vis and NMR spectroscopy. The results demonstrate the complete MB dye degradation in 20 minutes with 1 mg mL-1 of PAu-CQD/TiO2 NC, which otherwise is 30 minutes for PAg@CQD/TiO2 dose under visible light irradiation. Similarly, the pharmaceutical drug was found to degrade in 150 minutes with PAu-CQD/TiO2 photocatalysts. These findings reveal the enhanced photocatalytic performance of the green-synthesized Au decorated with TiO2 nanofibers and are attributed to the boosted SPR effect and aqueous-phase stability of Au nanostructures. This study opens a new domain of utilizing waste-derived and green-synthesized plasmonic nanostructures for the degradation of toxic/hazardous dyes and pharmaceutical pollutants in water.