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

Bismuth vanadate (BiVO₄) is one of the best bismuth-based semiconducting materials because of its narrow band gap energy, good visible light absorption, unique physical and chemical characteristics, and non-toxic nature. In addition, BiVO₄ with different morphologies has been synthesized and exhibited excellent visible light photocatalytic efficiency in the degradation of various organic pollutants, including volatile organic compounds (VOCs). Nevertheless, the commercial scale utilization of BiVO₄ is significantly limited because of the poor separation (faster recombination rate) and transport ability of photogenerated electron-hole pairs. So, engineering/modifications of BiVO₄ materials are performed to enhance their structural, electronic, and morphological properties. Thus, this review article aims to provide a critical overview of advanced oxidation processes (AOPs), various semiconducting nanomaterials, BiVO₄ synthesis methodologies, engineering of BiVO₄ properties through making binary and ternary nanocomposites, and coupling with metals/non-metals and metal nanoparticles and the development of Z-scheme type nanocomposites, etc., and their visible light photocatalytic efficiency in VOCs degradation. In addition, future challenges and the way forward for improving the commercial-scale application of BiVO₄-based semiconducting nanomaterials are also discussed. Thus, we hope that this review is a valuable resource for designing BiVO₄-based nanocomposites with superior visible-light-driven photocatalytic efficiency in VOCs degradation.

Facile Phase Control and Photocatalytic Performance of BiVO4 Crystals for Methylene Blue Degradation

Emerging contaminants, which mainly exist as organic pollutants and pose adverse biological effects, could be removed using photocatalytic degradation, resulting in a low-cost and environmentally friendly solution. Herein, BiVO4 nanoparticles with different morphologies and photocatalytic performances were synthesized by hydrothermal treatment at different residence times. The XRD and SEM results indicate that the crystal phase of BiVO4 gradually transformed from a single tetragonal phase to a single monoclinic crystal phase as the hydrothermal time increased, and with the extension of the hydrothermal time, the morphology of BiVO4 nanoparticles gradually differentiated from a smooth spherical shape to flower-like shapes composed of polyhedrons; the size of the crystals also increased accordingly. Methylene blue (MB), used as a probe of organic pollutants, was degraded under visible light irradiation by all BiVO4 samples to investigate its photocatalytic activities. The experimental results show that the longer the hydrothermal time, the better the photocatalytic performance. The optimum hydrothermal time was 24 h, at which the sample showed the highest photocatalytic activity for MB degradation. This work shows a convenient strategy for control of the crystal phase of BiVO4-based photocatalysts based on the understanding of the crystal morphology evolution mechanism, which will benefit the researchers in designing new BiVO4-based photocatalysts with high efficiency for emerging contaminants' degradation.

Synthesis of MoS2/Mg(OH)2/BiVO4 hybrid photocatalyst by ultrasonic homogenization assisted hydrothermal methods and its application as sunlight active photocatalyst for water decontamination

In this work, MoS₂/Mg(OH)₂/BiVO₄ ternary hybrid photocatalyst was synthesized by sonicated precursor mixture to the hydrothermal procedure to generate a highly efficient solar light-induced and simply recyclable photocatalyst. The obtained hybrid was confirmed by the characteristic peaks of MoS₂/Mg(OH)₂/BiVO₄ observed in X-ray diffraction (14.31°/18.62°/28.18°), infrared spectra (465/445/679 cm^-1), ultraviolet-visible spectra (636/683/639 nm) studies, and the band-gap narrowing (2.62/2.44/2.25 eV). The morphological structure of MoS₂ (rod), Mg(OH)₂ (particles), and BiVO₄ (random aggregates) were turned into MoS₂/Mg(OH)₂/BiVO₄ hierarchical nanosheets that coexisted with particles. The photodegradation experiments of the photocatalysts were assessed by using Congo Red (CR), Malachite Green (MG) and Textile Industry Effluent (TIE) as the model pollutant under direct sunlight. The photocatalytic efficiency of the hybrids was noticeably 2.1 to 2.3 times higher than that of the individual components. Photocurrent response test indicate that MoS₂/Mg(OH)₂/BiVO₄ ternary hybrid nanocomposites photocatalysts had a more effective electron/hole pair separation than individual and binary composite photocatalysts. The mechanism of photodegradation of MoS₂/Mg(OH)₂/BiVO₄ternary hybrid photocatalysts was investigated and discussed.

Impact of Erbium (Er) and Yttrium (Y) doping on BiVO4 crystal structure towards the enhancement of photoelectrochemical water splitting and photocatalytic performance

An efficient BiVO₄nanocatalyst with Erbium (Er) and Yttrium (Y) doping was synthesized via a facile microwave irradiation route and the obtained materials were further characterized through various techniques such as p-XRD, FT-IR, FE-SEM, HR-TEM, UV-Vis DRS, PL, LSV, and EISanalysis. The obtained results revealed that the rare metals induce the stabilization of the monoclinic-tetragonal crystalline structure with a distinct morphology. The yttrium doped BiVO₄ (Y-BiVO₄) monoclinic-tetragonal exhibited anefficient photoelectrochemical water splitting and photocatalytic performanceare compared to bare BiVO₄. TheY-BiVO₄ indicated increased results of photocurrent of 0.43 mA/cm²and bare BiVO₄0.24 mA/cm². Also, the Y-doped BiVO₄ nanocatalyst showed the maximum photocatalytic activity for the degradation of MB, MO, and RhB. A maximum degradation of 93%, 85%, and 91% was achieved for MB, MO, and RhB respectively, within 180 min under the visible light illumination. The photocatalytic decomposition of acetaldehyde also was performed. The improved photoelectrochemical water splitting and photocatalytic activity are due to the narrowing the bandgap, leading to extending the photoabsorption capability and reducing the recombination rate of photoexcited electron-hole pairs through the formation inner energy state of the rare earth metals. The current study disclosed that the synthesis of nanomaterials with crystal modification could be a prospectivecontender forhydrogen energy production as well as to the photocatalytic degradation of organic pollutants.To the best of our knowledge, both photocatalytic and photoelectrochemical studies were never been reported before for this type of material.

Facile fabrication of porous BiVO4hollow spheres with improved visible-light photocatalytic properties

Bismuth vanadate (BiVO₄) hollow spheres with porous structure have been successfully fabricated by a one-step wet solution method with no surfactant and template.

Controlled synthesis of CeVO4 hierarchical hollow microspheres with tunable hollowness and their efficient photocatalytic activity

CeVO₄ hierarchical hollow microspheres assembled from nanoscaled building units (nanoparticles, nanocubes and nanoflakes) were synthesized by a one-step hydrothermal approach using l-Asp as the morphology-directing agent.

Synthesis of a monoclinic BiVO4 nanorod array as the photocatalyst for efficient photoelectrochemical water oxidation

The BiVO₄ nanorod array is successfully synthesized on fluorine-doped tin oxide (FTO) glasses via a simple solution method, and the electrode is applied as the photoanode for water oxidation.

Facile synthesis of graphene-like copper oxide nanofilms with enhanced electrochemical and photocatalytic properties in energy and environmental applications

Novel graphene-like CuO nanofilms are grown on a copper foam substrate by in situ anodization for multifunctional applications as supercapacitor electrodes and photocatalysts for the degradation of dye pollutants. The as-prepared CuO consists of interconnected, highly crystalline, conductive CuO nanosheets with hierarchical open mesopores and a large surface area. The CuO nanofilms supported on a copper foam are employed as freestanding, binder-free electrodes for supercapacitors, which exhibit wonderful electrochemical performance with a large specific capacitance (919 F g(-1) at 1 A g(-1)), an excellent cycling stability (7% capacitance loss after 5000 cycles), and a good rate capability (748 F g(-1) at 30 A g(-1)). The porous CuO nanofilms also demonstrate excellent photocatalytic activities for degradation of methylene blue, with a degradation rate 99% much higher than 54% of the commercial CuO powders after 60 min. This excellent energy storage and photocatalytic performance of the graphene-like CuO nanofilms can open a new avenue for large-scale applications in energy and environmental fields.

Selective construction of junctions on different facets of BiVO4 for enhancing photo-activity

The combination of p–n and m–s junctions over BiVO₄ results in an additional effect for improving photo-activity.