Engineering of Z-scheme 2D/3D architectures with Bi2MoO6 on TiO2 nanosphere for enhanced photocatalytic 4-nitrophenol degradation

Sensitive photoelectric sensing for 5-HMF detection

5-Hydroxymethylfurfural (5-HMF) is a heterocyclic compound with six carbons commonly found in heat-treated carbohydrate-rich foods. 5-HMF exceeding the specified limit is cytotoxic to the human body, and will be converted into carcinogenic substances (5-sulfoxide methyl furfural) after long-term accumulation in the body. Therefore, it is highly necessary to develop a sensitive and accurate detection method for 5-HMF in the field of food safety. In this study, a photoelectric sensing method was developed for the highly sensitive detection of 5-HMF using hollow TiO2 nanospheres successfully synthesized by template, sol-gel and lye etching methods. The structure and composition of the materials were studied by XRD, XPS, SEM and TEM. The electrochemical and photoelectrochemical properties of an h-TiO2 electrode probe based on indium tin oxide (ITO) slides were investigated. The results indicated that the linear relationship of 5-HMF is good in the concentration range of 10-11-10-7 M, and the detection limit of 5-HMF is 0.001 nM. Moreover, the PEC sensor shows high accuracy in the detection of actual samples.

Research progress of TiO2-based photocatalytic degradation of wastewater: bibliometric analysis

The pollution caused by modernization and industrialization has caused serious harm to the biodiversity of the earth. TiO2-based photocatalyst has been widely studied as an effective and sustainable water environment remediation material. In this study, we analyzed the status and research trends of TiO2-based photocatalytic degradation of wastewater in depression from 2003 to 2023 to provide a reference for further research. "Doping", "Modification" and "Heterojunction" were used as keywords, and 817 related academic literatures were screened out by using Web of Science database. Through the visualization software VOSviewer and CiteSpace, the authors, institutions and literature keywords were clustered. The results show that since 2008, the annual number of published papers on TiO2-based photocatalytic degradation of wastewater has increased from 9 to 114. Among them, China has published 432 articles and made great contributions, and there are many representative research teams. Chinese universities are the main body to study TiO2-based photocatalytic degradation of wastewater, but the cooperation between universities is not as close as that abroad. This paper comprehensively analyzes the research hotspots of TiO2-based photocatalytic degradation of wastewater, such as the doping of TiO2 and the construction of different types of heterojunctions of TiO2. It is expected that these analysis results will provide new research ideas for researchers to carry out future research on related topics and let researchers know in-depth research institutions and possible collaborators to conduct academic exchanges and discussions with active institutions.

Pt-Cu@Bi2MoO6/TiO2 Photocatalyst for CO2 Reduction

Bi2MoO6/TiO2 heterojunction photocatalysts were constructed by depositing Bi2MoO6 nanosheets on TiO2 nanobelts' surface using a solvothermal method, and the surface of the optimum Bi2MoO6/TiO2 composite was decorated with copper and/or platinum nanoparticles. The synthesized samples were investigated for the CO2 photocatalytic reduction. The structural and optical properties of synthesized photocatalysts were characterized by XRD, FESEM, EDX, N2-physisorption, Raman, TPD-CO2, DRS, and PL analysis. The Bi2MoO6/TiO2 composite with different molar ratios of Bi2MoO6 to TiO2 (1, 1/2, 1/3, 1/4, 1/5, and 1/6) showed enhanced photocatalytic activity compared to pure Bi2MoO6 and TiO2. In comparison to bulk Bi2MoO6 and TiO2, the formation of a heterojunction between Bi2MoO6 and TiO2 leads to enhanced CO2 adsorption capacity. The enhanced performance of composites can be ascribed to the improved efficiency of light harvesting in the visible light range and suppressing charge recombination. The composite photocatalytic activity indicated that the ratio of Bi2MoO6 to TiO2 in the composite samples influenced the photocatalytic performance. The Bi2MoO6/TiO2 composite with 1/4 molar ratio had the best performance in 8 h (36.4 μmol/gcat), which was about 10 and 3 times higher than TiO2 and Bi2MoO6 photocatalysts, respectively. Under UV-visible light irradiation, the Pt-Cu@BMT4 sample produced the highest amount of methane (83.6 μmol/gcat) during CO2 photoreduction. During four irradiation cycles, the Pt-Cu@BMT4 sample exhibited superior stability with less than 5% decrease in methane production.

Heterojunction photocatalysts for the removal of nitrophenol: A systematic review

Nitrophenols are the most widely used raw materials in the chemical, pesticide, and pharmaceutical industries. Due to improper waste management and excessive usage, nitrophenol is listed as a priority pollutant and garnered global research attention. This review highlights the recent progress on heterojunction photocatalysts toward eliminating nitrophenols. The detailed mechanisms of the electron-hole pair separation using different heterojunctions such as traditional, p-n, Z-scheme, S-scheme, and Schottky heterojunctions are elaborated. The performance of the photocatalysts is evaluated using quantum efficiency. Among the heterojunctions, Z-scheme exhibited maximum removal efficiency of 100% and found superior over other heterojunctions. Even though heterojunctions exhibit good efficiency, the reusability of the heterojunction photocatalyst is not reported beyond 5 cycles. Further research is indeed to develop a highly reusable photocatalyst for environmental remediation.

Ag-modified TiO2/SiO2/Fe3O4 sphere with core-shell structure for photo-assisted reduction of 4-nitrophenol

Nitrogen-containing contaminants, such as 4-nitrophenol (4-NP), cause detrimental effects when discharged into the environment and thus should be reduced or removed from ecosystems. In this study, an Ag-loaded TiO₂-SiO₂-Fe₃O₄ (TSF) with a core-shell structure was employed for the photo-assisted reduction of 4-NP. Fe₃O₄, SiO₂, and TiO₂ in the core-shell structure served as a magnetic center, protective layer, and light absorber, respectively. To improve the reduction activity of 4-NP, Ag was loaded onto TSF under stirring, with a variation of the temperature (2-130 °C) and reaction time (1, 2, and 4 h). Under the optimized conditions, 5Ag-TSF (with 5 wt% of Ag) could promote the reduction of aqueous 4-NP solution (2 × 10^-4 M, 75 mL) in the presence of NaBH₄ (0.1 M, 5 mL) under irradiation by a metal halide lamp, affording over 98% reduction within 5 min and a rate constant of 0.185 min^-1, demonstrating its promising activity. Moreover, due to the advantages of the core-shell structure, the magnetic properties of Fe₃O₄ were sufficient to enable facile recycling of the sample for further reaction; SiO₂ could protect the Fe₃O₄ center from oxidation or reduction; TiO₂ enabled Ag accommodation and absorbed light to generate electron-hole pairs. In summary, an Ag-loaded TiO₂-SiO₂-Fe₃O₄ sphere with high activity and recyclability for 4-NP reduction was prepared via a facile and simple stirring method, where the sample can be used as a promising material in environmental remediation.

Immobilization of Ag(0) nanoparticles on quaternary ammonium functionalized polyacrylonitrile fiber as a highly active catalyst for 4-nitrophenol reduction

Ag(0) nanoparticles were immobilized on various pyridine salt, imidazole salt and quaternary ammonium functionalized polyacrylonitrile fibers (PANFs) to prepare Ag(0)-immobilized fiber catalysts. The catalytic activities of these immobilized catalysts for 4-nitrophenol (4-NP) reduction were detected. Among them, the quaternary ammonium fiber with butyl group immobilized Ag(0) nanoparticle catalyst PAN_QA-C4F-Ag(0) showed the best catalytic activity, and can effectively catalyze 4-nitrophenol (4-NP) reduction with a high conversation rate of 99.6%. Furthermore, PAN_QA-C4F-Ag(0) can be easily recovered, and it was reused 20 times with little decrease in catalytic activity and moderate Ag retention (53.5%). Notably, the cationic groups in the functionalized fibers can stabilize Ag(0) nanoparticles through electrostatic interactions and steric effects, and play an important role in phase transfer catalysis. Accordingly, possible mechanisms for the 4-NP reduction catalyzed by PAN_QA-C4F-Ag(0) were proposed.

Ag(0) nanoparticles were immobilized on various pyridine salt, imidazole salt and quaternary ammonium functionalized polyacrylonitrile fibers (PANFs) to prepare Ag(0)-immobilized fiber catalysts.

Construction of visible-light driven Bi2MoO6-rGO-TiO2 photocatalyst for effective ofloxacin degradation

Photocatalytic removal is more appropriate for the destruction of organic contaminants. The ternary Bi₂MoO₆-reduced graphene oxide (rGO)-TiO₂ catalyst was synthesized using a simple hydrothermal method, and various surface analytical optical techniques were analyzed. The photocatalytic decomposition efficiency of the Bi₂MoO₆-rGO-TiO₂ composite was 92.3% higher than those of pure and binary photocatalysts. The effects of operational parameters, such as catalyst ratio, catalyst variation, rGO ratio variation, and pH value variation were also analyzed. The as-prepared ternary photocatalyst exhibited low photoluminescence and high photocurrent density, which suppressed photon-induced electron and hole (h⁺) recombination and effective charge separation. The study demonstrated that rGO has excellent electron transfer performance and enhanced photocatalytic reaction stability. The perfect cycling stability of Bi₂MoO₆-rGO-TiO₂ was retained even after five consecutive cycles on the photocatalytic degradation reaction performance. In this study, we propose a decomposition performance mechanism for ofloxacin degradation that underwent visible-light irradiation.

A Mini Review on Bismuth-Based Z-Scheme Photocatalysts

Recently, the bismuth-based (Bi-based) Z-scheme photocatalysts have been paid great attention due to their good solar energy utilization capacity, the high separation rate of their photogenerated hole-electron pairs, and strong redox ability. They are considerably more promising materials than single semiconductors for alleviating the energy crisis and environmental deterioration by efficiently utilizing sunlight to motivate various photocatalytic reactions for energy production and pollutant removal. In this review, the traits and recent research progress of Bi-based semiconductors and recent achievements in the synthesis methods of Bi-based direct Z-scheme heterojunction photocatalysts are explored. The recent photocatalytic applications development of Bi-based Z-scheme heterojunction photocatalysts in environmental pollutants removal and detection, water splitting, CO₂ reduction, and air (NO_x) purification are also described concisely. The challenges and future perspective in the studies of Bi-based Z-scheme heterojunction photocatalysts are discussed and summarized in the conclusion of this mini review.

Fabrication of a high-adsorption N–TiO2/Bi2MoO6 composite photocatalyst with a hierarchical heterostructure for boosted weak-visible-light photocatalytic degradation of tetracycline

TiO₂ hierarchical heterostructure photocatalyst was successfully fabricated through the in situ growth of Bi₂MoO₆ nanosheets on rough N–TiO₂ nanorods with a bark-like surface. The structure–property relationship of this composite material were researched.