Photocatalytic properties of hierarchical BiOXs obtained via an ethanol-assisted solvothermal process

Non-radical activation of persulfate with Bi2O3/BiO1.3I0.4 for efficient degradation of propranolol under visible light

Non-radical activation of persulfate (PS) by photocatalysts is an effective approach for removing organic pollutants from aqueous environments. In this study, a novel Bi2O3/BiO1.3I0.4 heterojunction was synthesized using a facile solvothermal approach and used for the first time for non-radical activation of PS to degrade propranolol (PRO) in the presence of visible light. The findings found that the degradation rate of PRO in the Bi2O3/BiO1.3I0.4/PS system was significantly increased from 19% to more than 90% within 90 min compared to the Bi2O3/BiO1.3I0.4 system. This indicated that the composite system exerted an excellent synergistic effect between the photocatalyst and the persulfate-based oxygenation. Quenching tests and electron paramagnetic resonance demonstrated that the non-radical pathway with singlet oxygen as the active species played a major role in the photocatalytic process. The existence of photo-generated holes during the reaction could also be directly involved in the oxidation of pollutants. Meanwhile, a possible PRO degradation pathway was also proposed. Furthermore, the impacts of pH, humic acid and common anions on the PRO degradation by the Bi2O3/BiO1.3I0.4/PS were explored, and the system's stability and reusability were also studied. This study exhibits a highly productive catalyst for PS activation via a non-radical pathway and provides a new idea for the degradation of PRO.

Hydrophilicity and Pore Structure Enhancement in Polyurethane/Silk Protein-Bismuth Halide Oxide Composite Films for Photocatalytic Degradation of Dye

Polyurethane/silk protein-bismuth halide oxide composite films were fabricated using a blending-wet phase transformationin situsynthesis method. The crystal structure, micromorphology, and optical properties were conducted using XRD, SEM, and UV-Vis DRS characterize techniques. The results indicated that loaded silk protein enhanced the hydrophilicity and pore structure of the polyurethane composite films. The active species BiOX were observed to grow as nanosheets with high dispersion on the internal skeleton and silk protein surface of the polyurethane-silk protein film. The photocatalytic efficiency of BiOX/PU-SF composite films was assessed through the degradation of Rhodamine B under visible light irradiation. Among the tested films, the BiOBr/PU-SF composite exhibited the highest removal rate of RhB at 98.9%, surpassing the removal rates of 93.7% for the BiOCl/PU-SF composite and 85.6% for the BiOI/PU-SF composite. Furthermore, an active species capture test indicated that superoxide radical (•O2-) and hole (h+) species played a predominant role in the photodegradation process.

Effect of Urea as a Shape-Controlling Agent on the Properties of Bismuth Oxybromides

Bismuth oxybromides were prepared via a solvothermal method by applying different urea amounts during synthesis. The effects of the urea ratio on the morpho–structural properties and photocatalytic activity of the samples were investigated. X-ray diffraction, diffuse reflectance spectroscopy, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and surface tension measurements were carried out to characterize the samples. Their photoactivity was evaluated by the photocatalytic degradation of rhodamine B and ibuprofen under UV and visible light irradiations. The urea ratio notably influenced morphology, particle size distribution, and photoactivity. However, it only had a limited effect on the crystalline composition, primary crystallite size, and band gap of bismuth oxybromides. The formation of Bi-based complexes and degraded urea-based products were observed, which were deduced to influence band gap energies and hence, photoactivity. Predominantly, samples prepared at low urea ratios proved to be the best for both rhodamine B and ibuprofen degradations under both irradiations.

A review on the progress of the photocatalytic removal of refractory pollutants from water by BiOBr-based nanocomposites

Organic matters from various sources such as the manufacturing, agricultural, and pharmaceuticals industries is continuously discharged into water bodies, leading to increasingly serious water pollution. Photocatalytic technology is a clean and green advanced oxidation process, that can successfully decompose various organic pollutants into small inorganic molecules such as carbon dioxide and water under visible light irradiation. Bismuth oxybromide (BiOBr) is an attractive visible light photocatalyst with good photocatalytic performance, suitable forbidden bandwidth, and a unique layered structure. However, the rapid combination of the electron-hole pairs generated in BiOBr leads to low photocatalytic activity, which limits its photocatalytic performance. Due to its unique electronic structure, BiOBr can be coupled with a variety of different functional materials to improve its photocatalytic performance. In this paper, We present the morphologically controllable BiOBr and its preparation process with the influence of raw materials, additives, solvents, synthesis methods, and synthesis conditions. Based on this, we propose design synthesis considerations for BiOBr-based nanocomplexes in four aspects: structure, morphology and crystalline phase, reduction of electron-hole pair complexation, photocorrosion resistance, and scale-up synthesis. The literature on BiOBr-based nanocomposites in the last 10 years (2012-2022) are summarized into seven categories, and the mechanism of enhanced photocatalytic activity of BiOBr-based nanocomposites is reviewed. Moreover, the applications of BiOBr-based nanocomposites in the fields of degradation of dye wastewater, antibiotic wastewater, pesticide wastewater, and phenol-containing wastewater are reviewed. Finally, the current challenges and prospects of BiOBr-based nanocomposites are briefly described. In general, this paper reviews the construction of BiOBr-based nanocomposites, the mechanism of photocatalytic activity enhancement and its research status and application prospects in the degradation of organic pollutants.

Ti/TiO2 nanotubes sensitized PbS quantum dots as photoelectrodes applied for decomposition of anticancer drugs under simulated solar energy

One of the challenges in research into photoelectrocatalytic (PEC) degradation of pollutants is finding the appropriate photoanode material, which has a significant impact on the process efficiency. Among all others, photoelectrodes based on an ordered TiO₂ nanotube arrays are a promising material due to well-developed surface area and efficient charge separation. To increase the PEC activity of this material, the SILAR method was used to decorate Ti/TiO₂ nanotubes by PbS quantum dots (QD). The ifosfamide (IF) degradation rate constants was twice as higher for PbS-Ti/TiO₂ (0.0148 min^-1) than for Ti/TiO₂ (0.0072 min^-1). Our research showed the highest efficiency of PEC degradation of drugs using IIIPbS-Ti/TiO₂ made with 3 SILAR cycles (PbS QD size mainly 2-4 nm). The 4 and 6 of SILAR cycles resulted in the aggregation of PbS nanoparticles on the Ti/TiO₂ surface and decreased IF PEC degradation rate to 0.0043 and 0.0033 min^-1, respectively. Research on PEC mechanism has shown that the drugs are degraded mainly by the activity of photogenerated holes and hydroxyl radicals. In addition, the identified drug intermediates made possible to propose a degradation pathways of anticancer drugs and the ecotoxicity test show no inhibition of Lemna minor growth of treated solutions.

Synthesis of Thin Bi9 O7.5 S6 Nanosheets for Improved Photodetection in a Wide Wavelength Range

Bismuth-based compounds possess layered structures with a variety of stacking modes, endowing the compounds with diverse properties. As one type of bismuth oxysulfides, Bi₉ O_7.5 S₆ nanocrystals has great applications in photodetection; however, the responsivity of bulky Bi₉ O_7.5 S₆ is limited due to the poor charge separation. Herein, single-crystalline Bi₉ O_7.5 S₆ thin nanosheets are successfully synthesized by using a solvothermal method. The thickness of the obtained Bi₉ O_7.5 S₆ nanosheets is down to 15 nm and can be easily tuned by varying the reaction period. Moreover, the Bi₉ O_7.5 S₆ nanosheets show strong light absorption in the visible and near infrared range, making it a promising candidate in optoelectronics. As a demonstration, the thin Bi₉ O_7.5 S₆ nanosheets are used as active layer in an optoelectronic device, which exhibits sensitive photoelectric response to light in a wide range of 400-800 nm. The responsivity of the device reaches up to 1140 μA W^-1 , and the performance of the device is stable after long-period illumination. This work demonstrates a great potential of the thin Bi₉ O_7.5 S₆ nanosheets in optoelectronic devices, and these nanosheets may also be extended to various optoelectronic applications.

A critical review on bismuth oxyhalide based photocatalysis for pharmaceutical active compounds degradation: Modifications, reactive sites, and challenges

Pharmaceutical active compounds (PhACs), as a kind of widely used pharmaceutical drugs, has attracted much attention. The bismuth oxyhalides (BiOX)-based photocatalysis can remove PhACs efficiently due to its unique layered structure, optical and electronic properties. Nevertheless, the rapid recombination of photogenerated electron-hole pairs, and the inherent instability of structure have limited its practical application. In order to solve these problems, recent modification studies tend to focus on facet control, elemental doping, bismuth-rich strategies, defect engineering and heterojunction. Therefore, the objective of this review is to summarize the recent developments in multiply modified strategies for PhACs degradation. The synthesis methods, photocatalytic properties and the enhancement mechanism are elaborated. Besides, based on theoretical calculation, the reactive sites of typical PhACs attacked by different reactive oxygen species were also proposed. Subsequently, challenges and opportunities in applications are also featured which include factors, viz., dissolution of halogen ions, instability under visible light, applications of real water/wastewater, intermediates and byproducts toxicity analysis of BiOX-based photocatalysis. Finally, the perspectives of BiOX-based photocatalysis for PhACs photodegradation in actual water applications are highlighted.

Morphology Regulation Mechanism and Enhancement of Photocatalytic Performance of BiOX (X = Cl, Br, I) via Mannitol-Assisted Synthesis

BiOX (X = Cl, Br, I) photocatalysts with dominant (110) facets were synthesized via a mannitol-assisted solvothermal method. This is the first report on the exposed (110) facets-, size-, and defects-controlled synthesis of BiOX achieved by solvothermal synthesis with mannitol. This polyol alcohol acted simultaneously as a solvent, capping agent, and/or soft template. The mannitol concentration on the new photocatalysts morphology and surface properties was investigated in detail. At the lowest concentration tested, mannitol acted as a structure-directing agent, causing unification of nanoparticles, while at higher concentrations, it functioned as a solvent and soft template. The effect of exposed (110) facet and surface defects (Bi(3−x)+, Bi4+, Bi5+) of BiOX on the photocatalytic activity of nanomaterials under the UV–Vis irradiation were evaluated by oxidation of Rhodamine B (RhB) and 5-fluorouracil (5-FU), an anticancer drug, and by reduction of Cr(VI). Additionally, the influence of crucial factors on the formation of BiOX in the synthesis with mannitol was discussed extensively, and the mechanism of BiOX formation was proposed. These studies presented a new simple method for synthesizing BiOX without any additional surfactants or shape control agents with good photocatalytic activity. The study also provided a better understanding of the effects of solvothermal conditions on the BiOX crystal growth.

One dimensional hierarchical BiOCl microrods: their synthesis and their photocatalytic performance

One dimensional hierarchical BiOCl microrods are controlled synthesized via hydrothermal method using sodium citrate as structure-agent. These hierarchical BiOCl architectures exhibit outstanding photocatalytic activity for degrading organic dyes and phenol.