Nonaqueous Synthesis of a Bismuth Vanadate Photocatalyst By Using Microwave Heating: Photooxidation versus Photosensitized Decomposition in Visible-Light-Driven Photocatalysis

Hydrothermal synthesis of m-BiVO4/t-BiVO4 heterostructure for organic pollutants degradation: Insight into the photocatalytic mechanism of exposed facets from crystalline phase controlling

A series of BiVO₄ photocatalysts were prepared by a co-precipitation followed hydrothermal synthesis method for the photodegradation of Rhodamine B (RhB) and 2,4-Dichlorophenol (2,4-DCP). The crystalline phase ratio of the heterostructured BiVO₄ (m-BiVO₄/t-BiVO₄) between monoclinic and tetragonal could be easily controlled at different pH and hydrothermal time. Interestingly, the as-prepared heterostructured BiVO₄ photocatalyst at pH = 7 for 24 h (BiVO₄-7-24) showed the highest photocatalytic activities for the degradation of RhB, while the best photodegradation of 2,4-DCP was obtained at pH = 0.5 for 24 h (BiVO₄-0.5-24). The photocatalytic mechanism can be explained by the different charge carrier transfer pathways and active oxidation species in the m-BiVO₄/t-BiVO₄ heterostructure. More importantly, the exposed facets originated from crystalline phase controlling in BiVO₄-0.5-24 and BiVO₄-7-24 photocatalyst is an essential reason for the different photocatalytic activity. The proposed energy band alignments of BiVO₄-0.5-24 and BiVO₄-7-24 photocatalyst provide insights into the photocatalytic mechanism of the m-BiVO₄/t-BiVO₄ heterostructure.

Thin Coatings of α- and β-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light

Thin coatings of Bi2O3 were deposited on glass substrates by ultrasonic spray coating of THF solutions of the molecular precursor [Bi38O45(OMc)24(DMSO)9] ⋅ 2DMSO ⋅ 7H2O (OMc=O2CC3H5) followed by hydrolysis and subsequent annealing. Depending on the synthetic protocol, the bismuth oxido cluster was transformed into either α- or β-Bi2O3. The as-synthesized Bi2O3 coatings were characterized by powder X-ray diffraction (PXRD), thickness measurements, diffuse reflectance UV-Vis spectroscopy (DRS), photoluminescence (PL) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The thin coatings (thickness: 5-16 μm) were compared with regard to their performance in photocatalytic rhodamine B (RhB) decomposition under visible light irradiation. The β-Bi2O3 coatings, that showed the highest photocatalytic activity, were used for the photocatalytic decomposition of other pollutants such as triclosan and ethinyl estradiol. In addition, the interplay between the photooxidation that is induced by the excitation of the catalyst using visible light and the photosensitized decomposition pathway was studied by degradation experiments of aqueous rhodamine B solutions using β-Bi2O3 coatings.

Co2+ substituted for Bi3+ in BiVO4 and its enhanced photocatalytic activity under visible LED light irradiation

We investigated the fabrication of Co-doped BiVO₄ (Bi_1−xCo_xVO_4+δ, 0.05 < x < 0.5) by the substitution of Co ions for Bi sites in BiVO₄. The X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) results indicated that the substitution of Co²⁺ ions for Bi³⁺ sites in BiVO₄ was successful, although a change in the crystal phase of BiVO₄ did not occur. UV-vis DRS and PL results suggested that the Co-incorporation could slightly improve the visible light absorption of BiVO₄ and induce the separation of photoinduced electron–hole pairs; therefore, a significant enhancement of photocatalytic performance was achieved. The Bi_0.8Co_0.2VO_4+δ sample showed superior photocatalytic activity in comparison with other samples, achieving 96.78% methylene blue (MB) removal within 180 min. In addition, the proposed mechanism of improved photocatalytic activities and the stability of the catalyst were also investigated.

We investigated the fabrication of Co-doped BiVO₄ (Bi_1−xCo_xVO_4+δ, 0.05 < x < 0.5) by the substitution of Co ions for Bi sites in BiVO₄.

Bismuth vanadate-based semiconductor photocatalysts: a short critical review on the efficiency and the mechanism of photodegradation of organic pollutants

The number of publications on photocatalytic bismuth vanadate-based materials is constantly increasing. Indeed, bismuth vanadate is gaining stronger interest in the photochemical community since it is a solar-driven photocatalyst. However, the efficiency of BiVO₄-based photocatalyst under sunlight is questionable: in most of the studies investigating the photodegradation of organic pollutants, only few works identify the by-products and evaluate the real efficiency of BiVO₄-based materials. This short review aims to (i) present briefly the principles of photocatalysis and define the photocatalytic efficiency and (ii) discuss the formation of reactive species involved in the photocatalytic degradation process of pollutants and thus the corresponding photodegradation mechanism could be determined. All these points are developed in a comprehensive discussion by focusing especially on pure, doped, and composite BiVO₄. Therefore, this review exhibits a critical overview on different BiVO₄-based photocatalytic systems with their real efficiency. This is a necessary knowledge for potential implementation of BiVO₄ materials in environmental applications at larger scale than laboratory conditions.

Mechanochemically synthesized m-BiVO4 nanoparticles for visible light photocatalysis

Mechanochemical high energy ball milling approach was used to synthesize monoclinic BiVO₄ (m-BiVO₄) nanoparticles in an attempt to simultaneously reduce the particle size and improve the throughput for practical photocatalytic applications.