BiVO4 As a Sustainable and Emerging Photocatalyst: Synthesis Methodologies, Engineering Properties, and Its Volatile Organic Compounds Degradation Efficiency

Systematic investigation on the rational design and optimization of bi-based metal oxide semiconductors in photocatalytic applications

To address the global energy shortage and mitigate greenhouse gas emissions on a massive scale, it is critical to explore novel and efficient photocatalysts for the utilization of renewable resources. Bi-based metal oxide (BixMOy) semiconductors composed of bismuth, transition metal, and oxygen atoms have demonstrated improved photocatalytic activity and product selectivity. The vast number of element combinations available for BixMOymaterials provides a huge compositional space for the rational design and isolation of promising photocatalysts for specific applications. In this study, we have systematically investigated the electronic and optical properties over Bi2O3and a series of selected BixMOygroup materials (BiVO4, BiFeO3, BiCoO3, and BiCrO3) by calculating band structure, basic optical property features, mobility and separation of charge carriers. It is clearly noted that the band gap and band edge position of the BixMOygroup materials can be tuned in a wide range in comparison to Bi2O3. Similarly, the light response of BixMOyalso can be broadened from the ultraviolet to the visible light region by adjusting the selection of transition metals. Additionally, the analysis of the effective mass of charge carriers of these materials further confirms their possibility in photocatalytic reaction applications because of the appropriate separation efficiency and mobility of carriers. A selection of experimental investigations on the crystal structure, composition, and optical properties of Bi2O3, BiVO4, and BiFeO3as well as their catalytic performance in the degradation of methylene blue over was also conducted, which agree well with the theoretical predictions.

Terbium Vanadate Nanowires-Based Electrochemical Sensors for Mercury Ions

Terbium vanadate nanowires were synthesized via a facile chemical approach using sodium vanadate and terbium chloride. Morphology, structure, composition, and electrochemical characteristics of the terbium vanadate nanowires were investigated by different techniques. Terbium vanadate nanowires with single crystalline tetragonal TbVO4 phase possess smooth surface and flat tips. The length of the nanowires is longer than 5 μm, and diameter is 40-100 nm. Terbium vanadate nanowires modified electrode was used for trace-level mercury ions (Hg2+) detection. One well-defined stripping peak exists at - 0.34 V at the terbium vanadate nanowires modified electrode in 0.1 mM Hg2+ solution. Buffer solution pH value, deposition time, deposition potential, and standing time are pH = 1, 150 s, - 1.5 V, and 60 s, respectively. Detection limit for Hg2+ detection is 0.18 nM, and linear range is 0.01-100 μM. The proposed terbium vanadate nanowires modified electrode exhibits significant selectivity, stability, and reproducibility toward Hg2+. The usefulness of the developed sensor based on the terbium vanadate nanowires modified electrode was verified by Hg2+ detection in real samples.

Review of Bi-based catalysts in piezocatalytic, photocatalytic and piezo-photocatalytic degradation of organic pollutants

Photocatalysis, as an effective advanced oxidation process, has been widely carried out in water waste treatment, especially in the degradation of organic pollutants. However, the photocatalytic process is limited by the high recombination rate of photo-generated carriers. To improve photocatalytic efficiency, piezocatalysis has attracted increasing attention, especially that using lead-free piezoelectric materials, which avoids the secondary pollution of lead toxicity in the environment. Bi-based materials have both photocatalytic activity and piezocatalytic activity, which can perfectly combine the advantages of these two catalytic processes to promote the degradation of organic pollutants. Under an external mechanical action, the Bi-based catalyst produces a polarized electric field due to the piezoelectric effect, and the photo-generated carriers can be effectively separated under electrostatic attraction, thus obtaining more efficient photocatalytic performance. However, there are still many gaps in the design, reaction mechanism, and development prospects of Bi-based piezo-photocatalysts. Therefore, to acquire a deeper understanding of the research status of Bi-based piezo-photocatalysts, we summarize the existing literature to provide effective ways to improve piezo-photocatalytic performance. Moreover, this paper points out the developmental direction of piezo-photocatalysis in the future. Last but not least, we also look forward to the prospect of piezo-photocatalysis in the degradation of organic pollutants.

Comparative photocatalytic study of visible light driven BiVO4, Cu2O, and Cu2O/BiVO4 nanocomposite for degradation of antibiotic for wastewater treatment

Semiconductor-based photocatalysts have become increasingly used in the removal of pollutants from wastewater, especially antibiotics. A series of composite-based cuprous oxide and bismuth vanadate (Cu2O/BiVO4) composite-based photocatalysts were synthesized by using the chemical method. The structure of the Cu2O/BiVO4 composite was verified by using x-ray diffraction, scanning electron microscopy, photoluminescence, Fourier transform infrared spectroscopy, and UV-visible spectra. The degradation of methylene blue (MB) and tetracycline (TC) was investigated to check the photocatalytic activity of the Cu2O/BiVO4 composite series. The quantity of Cu2O was varied from 1% to 7% by weight to prepare the series of Cu2O/BiVO4 composites. The analysis of results verified that 5% Cu2O/BiVO4 exhibits an outstanding photocatalytic activity as compared to 1%, 3%, and 7% Cu2O/BiVO4, pure Cu2O, and pure BiVO4 under visible light irradiation. The optimum value of photocatalytic degradation achieved with 5% Cu2O/BiVO4 was 97% for MB dye and 95% for TC in 120 min, which is greater than the photocatalytic degradation of pure BiVO4 (MB 45% and TC 72%), pure Cu2O (MB 57% and TC 80%), 1% Cu2O/BiVO4 (MB 72% and TC 85%), 3% Cu2O/BiVO4 (MB 83% and TC 88%), and 7% Cu2O/BiVO4 (MB 87% and TC 91%). The stability and reusability of Cu2O/BiVO4 were also investigated. To check the major role of trapping in degradation, a trapping experiment was also performed by using three trapping agents: BQ, EDTA, and tBuOH. The results showed that Cu2O/BiVO4 exhibits an improved photocatalytic activity in the degradation of antibiotics in polluted water because the recombination rate of the electron-hole pair decreased and the surface area increased, which increased the active sites for redox reactions. Such a photocatalytic composite with high efficiency has various applications, such as energy production, environmental remediation, and water remediation.

A Meta-Analysis of Influencing Factors on the Activity of BiVO4-Based Photocatalysts

With the continuous advancement of global industrialization, a large amount of organic and inorganic pollutants have been discharged into the environment, which is essential for human survival. Consequently, the issue of water environment pollution has become increasingly severe. Photocatalytic technology is widely used to degrade water pollutants due to its strong oxidizing performance and non-polluting characteristics, and BiVO4-based photocatalysts are one of the ideal raw materials for photocatalytic reactions. However, a comprehensive global analysis of the factors influencing the photocatalytic performance of BiVO4-based photocatalysts is currently lacking. Here, we performed a meta-analysis to investigate the differences in specific surface area, kinetic constants, and the pollutant degradation performance of BiVO4-based photocatalysts under different preparation and degradation conditions. It was found that under the loading condition, all the performances of the photocatalysts can be attributed to the single BiVO4 photocatalyst. Moreover, loading could lead to an increase in the specific surface area of the material, thereby providing more adsorption sites for photocatalysis and ultimately enhancing the photocatalytic performance. Overall, the construct heterojunction and loaded nanomaterials exhibit a superior performance for BiVO4-based photocatalysts with 136.4% and 90.1% improvement, respectively. Additionally, within a certain range, the photocatalytic performance increases with the reaction time and temperature.

An Enhanced Photosensitive Sensor Based on ITO/MWCNTs@Polymer Composite@BiVO4 for Quercetin Detection

The fact that antioxidants scavenge free radicals in the human body and naturally treat many health problems that will occur in this way has increased the consumption of antioxidant-containing foods. However, consumption of artificially prepared antioxidants could cause cancer. Therefore, antioxidants from natural sources are preferred. Quercetin is an antioxidant present in natural samples. In this article, multi-walled carbon nanotubes (MWCNTs), a polymer composite (PC) consisting of a mixture of 15% (by mass) polystyrene (PST), 15% (by mass) polyacrylonitrile (PAN) and 70% (by mass) polyindole (PIN), and semiconducting BiVO₄ were used to prepare electrodes, and then a photosensitive ITO/MWCNTs@PC@BiVO₄-based sensor was fabricated for quercetin detection. Quercetin was analyzed via the photosensitive ITO/MWCNTs@PC@BiVO₄ sensor in 0.1 M phosphate buffered saline (pH 7.4) solutions including various quercetin concentrations. The constructed quercetin sensor displayed a wide linear response between 10 and 200 μM and a limit of detection of 0.133 μM. The developed photosensitive ITO/MWCNTs@PC@BiVO4 demonstrated a high sensitivity (442 µA mM^-1 cm^-2), good reproducibility (relative standard deviation 3.6%), high selectivity and long-term stability (>49 days) towards quercetin sensing. The photoelectrochemical sensor was then applied to detection of quercetin in black tea as a real-life sample. Our study could lead to the development of novel photosensitive PC polyphenol sensors.