Tetragonal to Monoclinic Crystalline Phases Change of BiVO4 via Microwave-Hydrothermal Reaction: In Correlation with Visible-Light-Driven Photocatalytic Performance

Recent Developments in Nickel-Based Layered Double Hydroxides for Photo(-/)electrocatalytic Water Oxidation

Layered double hydroxides (LDHs), especially those containing nickel (Ni), are increasingly recognized for their potential in photo(-/)electrocatalytic water oxidation due to the abundant availability of Ni, their corrosion resistance, and their minimal toxicity. This review provides a comprehensive examination of Ni-based LDHs in electrocatalytic (EC), photocatalytic (PC), and photoelectrocatalytic (PEC) water oxidation processes. The review delves into the operational principles, highlighting similarities and distinctions as well as the benefits and limitations associated with each method of water oxidation. It includes a detailed discussion on the synthesis of monolayer, ultrathin, and bulk Ni-based LDHs, focusing on the merits and drawbacks inherent to each synthesis approach. Regarding the EC oxygen evolution reaction (OER), strategies to improve catalytic performance and insights into the structural evolution of Ni-based LDHs during the electrocatalytic process are summarized. Furthermore, the review extensively covers the advancements in Ni-based LDHs for PEC OER, including an analysis of semiconductors paired with Ni-based LDHs to form photoanodes, with a focus on their enhanced activity, stability, and underlying mechanisms facilitated by LDHs. The review concludes by addressing the challenges and prospects in the development of innovative Ni-based LDH catalysts for practical applications. The comprehensive insights provided in this paper will not only stimulate further research but also engage the scientific community, thus driving the field of photo(-/)electrocatalytic water oxidation forward.

Visible-Light-Driven Z-Type Pg-C3N4/Nitrogen Doped Biochar/BiVO4 Photo-Catalysts for the Degradation of Norfloxacin

Antibiotics cannot be effectively removed by traditional wastewater treatment processes, and have become widespread pollutants in various environments. In this study, a Z-type heterojunction photo-catalyst Pg-C3N4 (PCN)/Nitrogen doped biochar (N-Biochar)/BiVO4 (NCBN) for the degradation of norfloxacin (NOR) was prepared by the hydrothermal method. The specific surface area of the NCBN (42.88 m2/g) was further improved compared to BiVO4 (4.528 m2/g). The photo-catalytic performance of the catalyst was investigated, and the N-Biochar acted as a charge transfer channel to promote carrier separation and form Z-type heterojunctions. Moreover, the NCBN exhibited excellent performance (92.5%) in removing NOR, which maintained 70% degradation after four cycles. The main active substance of the NCBN was •O2-, and the possible degradation pathways are provided. This work will provide a theoretical basis for the construction of heterojunction photo-catalysts.

Carrier confinement activated explicit solvent dynamic of CdS/BiVO4/H2O and optimized photocatalytic hydrogen evolution performances

Herein, using an electrophoretic deposition strategy, a S-scheme CdS (cubic)/BiVO4 (monoclinic) heterostructured photocatalyst is fabricated. The as-synthesized photocatalysts exhibit high carrier separation efficiency, prominent hydrogen evolution ability and high stability. The results of the detailed density functional theory (DFT) prove that the photogenerated electrons and holes are located in BiVO4 and CdS components, respectively. Besides, an explicit solvent model based on the electron-enriched region in CdS/BiVO4 heterojunction is designed deliberately to investigate the solid/liquid interface issues. Intriguing findings demonstrate that the surface hydrogen diffusing rate in CdS/BiVO4/H2O is faster than that of BiVO4/H2O and is highly associated with the electron-enrich effect, which has a greater capacity to promote water decomposition, the possibility of proton collision and photocatalytic hydrogen evolution. Notably, the H p orbital can participate in the electron-enrich effect during solvation, thus reforming the orbital energy level and activating the HER of the BiVO4 component in the CdS/BiVO4 system.

Synergistic Effect of Co3(HPO4)2(OH)2 Cocatalyst and Al2O3 Passivation Layer on BiVO4 Photoanode for Enhanced Photoelectrochemical Water Oxidation

Bismuth vanadate (BVO) is regarded as an exceptional photoanode material for photoelectrochemical (PEC) water splitting, but it is restricted by the severe photocorrosion and slow water oxidation kinetics. Herein, a synergistic strategy combined with a Co3(HPO4)2(OH)2 (CoPH) cocatalyst and an Al2O3 (ALO) passivation layer was proposed for enhanced PEC performance. The CoPH/ALO/BVO photoanode exhibits an impressive photocurrent density of 4.9 mA cm-2 at 1.23 VRHE and an applied bias photon-to-current efficiency (ABPE) of 1.47% at 0.76 VRHE. This outstanding PEC performance can be ascribed to the suppressed surface charge recombination, facilitated interfacial charge transfer, and accelerated water oxidation kinetics with the introduction of the CoPH cocatalyst and ALO passivation layer. This work provides a novel and synergistic approach to design an efficient and stable photoanode for PEC applications by combining an oxygen evolution cocatalyst and a passivation layer.

Insight into the Key Restriction of BiVO4 Photoanodes Prepared by Pyrolysis Method for Scalable Preparation

Bismuth Vanadate (BiVO4 ) photoanode has been popularly investigated for promising solar water oxidation, but its intrinsic performance has been greatly retarded by the direct pyrolysis method. Here we insight the key restriction of BiVO4 prepared by metal-organic decomposition (MOD) method. It is found that the evaporation of vanadium during the pyrolysis tends to cause a substantial phase impurity, and the unexpected few tetragonal phase inhibits the charge separation evidently. Consequently, suitably excessive vanadium precursor was adopted to eliminate the phase impurity, based on which the obtained intrinsic BiVO4 photoanode could exhibit photocurrent density of 4.2 mA cm-2 at 1.23 VRHE under AM 1.5 G irradiation, as comparable to the one fabricated by the currently popular two-step electrodeposition method. Furthermore, the excellent performance can be maintained on the enlarged photoanode (25 cm2 ), demonstrating the advantage of MOD method in scalable preparation. Our work provides new insight and highlights the glorious future of MOD method for the design of scale-up efficient BiVO4 photoanode.

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.

Molecular Imprinted BiVO4 Microswimmers for Selective Target Recognition and Removal

Analogous to photosynthetic systems, photoactive semiconductor-based micro/nanoswimmers display biomimetic features that enable unique light harvesting and energy conversion functions and interactions with their surroundings. However, these artificial swimmers are usually non-selective and provide ineffective target recognition, resulting in poor surface analyte binding that affects the overall reactivity and motion efficiency. Here, the surface engineering of light-driven BiVO₄ microswimmers by molecular imprinting polymerization is presented. After embedding surface recognition sites, the modified microswimmers can self-propel in a solution of a target molecule, without requiring toxic fuels, and degrade the target selectively in a pollutant mixture. These findings show that optimizing the design of semiconductor-based microswimmers with specific target recognition cavities on their surface is a promising strategy to achieve selective capture and degradation of organic pollutants, which is otherwise impossible because of the non-selective behavior of photogenerated reactive radicals. Moreover, this study provides a unique strategy to enhance the motion capabilities of single-component photocatalytic microswimmers in a specific chemical environment.

Revealing the effect of substitutional cation doping in the A-site of nanoscale APbI3 perovskite layers for enhanced retention and endurance in optoelectronic resistive switching for non-volatile bipolar memory devices

The effect of substitutional cation doping in the A-site of the nanoscale APbI₃ perovskite layer has been systematically investigated to achieve improvements in the charge-carrier dynamics and endurance of non-volatile bipolar (NVB) memory devices. We successfully adopted an energy-efficient, ultra-fast microwave-assisted solvothermal (MW-ST) synthesis route to prepare a sequence of APbI₃ (A = MA⁺, FA⁺, MAFA⁺, CsMA⁺ and CsMAFA⁺) perovskite powders with morphological transitions from cube-like polyhedrons to mixed polyhedrons and rods within 10 minutes at 120 °C without requiring any inert-gas atmosphere under high-humid ambient conditions. As-prepared APbI₃ powders were dissolved in DMSO:DMF, followed by the fabrication of a thin film via spin-coating. Upon annealing at 120 °C, the nanoscale self-assembled thin-film layer was formed. We observed that devices with the inorganic Cs⁺ cation with organic cations, (CsMAPI and CsMAFAPI) device showed improved endurance (3500 and 5000 cycles, respectively) and outstanding retention (60 000 s) owing to effective charge-carrier dynamics, compared to organic cation-based MAPI, FAPI and MAFAPI (1800, 1200 and 1300 cycles, respectively). Significantly, various cation-doped APbI₃-powders obtained via the MW-ST method remained to be stable for up to 5-months under high-humid conditions. Thus, enhanced optoelectronic-memory performance studies could provide an opportunity for next-generation nanoscale ORSNVB-memory devices for artificial intelligence (AI) and Internet of Things (IoT) applications.

Facile preparation of nickel phosphide for enhancing the photoelectrochemical water splitting performance of BiVO4 photoanodes

The photoelectrochemical (PEC) water splitting performance of BiVO₄ (BVO), a promising photoanode material, is constrained by its extremely short hole diffusion length and slow water oxidation kinetics. Modification of oxygen evolution cocatalysts (OECs) by appropriate methods is a practical solution to enhance the PEC water splitting performance of BVO. In this work, two different nickel phosphides Ni₂P and Ni₁₂P₅ were prepared by a facile and mild one-step solvothermal method, and used as OECs to modify a BVO photoanode for enhancing the PEC water splitting performance. The BVO/Ni₂P and BVO/Ni₁₂P₅ photoanodes showed impressive photocurrent densities of 3.3 mA cm^-2 and 3.1 mA cm^-2, respectively. In addition, the PEC water splitting stability of the BVO/Ni₂P photoanode was greatly enhanced compared to that of the bare BVO photoanode. Further characterization and photoelectrochemical analysis revealed that the significant improvement of the BVO photoanode performance was attributed to the effective inhibition of surface charge recombination, facilitation of interfacial charge transfer, and acceleration of water oxidation kinetics after Ni₂P and Ni₁₂P₅ modification.

Bismuth-Based Multi-Component Heterostructured Nanocatalysts for Hydrogen Generation

Developing a unique catalytic system with enhanced activity is the topmost priority in the science of H2 energy to reduce costs in large-scale applications, such as automobiles and domestic sectors. Researchers are striving to design an effective catalytic system capable of significantly accelerating H2 production efficiency through green pathways, such as photochemical, electrochemical, and photoelectrochemical routes. Bi-based nanocatalysts are relatively cost-effective and environmentally benign materials which possess advanced optoelectronic properties. However, these nanocatalysts suffer back recombination reactions during photochemical and photoelectrochemical operations which impede their catalytic efficiency. However, heterojunction formation allows the separation of electron–hole pairs to avoid recombination via interfacial charge transfer. Thus, synergetic effects between the Bi-based heterostructured nanocatalysts largely improves the course of H2 generation. Here, we propose the systematic review of Bi-based heterostructured nanocatalysts, highlighting an in-depth discussion of various exceptional heterostructures, such as TiO2/BiWO6, BiWO6/Bi2S3, Bi2WO6/BiVO4, Bi2O3/Bi2WO6, ZnIn2S4/BiVO4, Bi2O3/Bi2MoO6, etc. The reviewed heterostructures exhibit excellent H2 evolution efficiency, ascribed to their higher stability, more exposed active sites, controlled morphology, and remarkable band-gap tunability. We adopted a slightly different approach for reviewing Bi-based heterostructures, compiling them according to their applicability in H2 energy and discussing challenges, prospects, and guidance to develop better and more efficient nanocatalytic systems.

Improved Performance of the Al2O3-Protected HfO2-TiO2 Base Layer with a Self-Assembled CH3NH3PbI3 Heterostructure for Extremely Low Operating Voltage and Stable Filament Formation in Nonvolatile Resistive Switching Memory

Herein, we report intriguing observations of an extremely stable nonvolatile bipolar resistive switching (NVBRS) memory device fabricated using HfO₂-TiO₂ topologically protected by Al₂O₃ as a stacked base layer for a CH₃NH₃PbI₃ (MAPI) electrolyte layer sandwiched between Ag and fluorine-doped tin oxide (FTO) electrodes. MAPI has been successfully synthesized by a rapid microwave-solvothermal (MW-ST) method within 10 min at 120 °C without requiring any inert gas atmosphere using low-cost precursors and solvents. Subsequently, MAPI powders are dissolved in aprotic solvents (DMF/DMSO = 8:2), and a spin-coated thin film is allowed to recrystallize upon annealing at 120 °C via a solution-based nanoscale self-assembly process. The fabricated memory device with the Ag/MAPI/Al₂O₃/TiO₂-HfO₂/FTO configuration shows an enhanced resistance ratio of 10⁵ for >10⁴ s at an extremely lower operating voltage (SET +0.2 V, RESET -0.2 V) when compared to that of the pristine MAPI device (±1 V, 10², 10⁴ s). We show that the memory device also exhibits a remarkable endurance of ≥3500 cycles due to the Al₂O₃ robust coating on the HfO₂-TiO₂ layer, facilitating prompt heterojunction formation. Thus, the adopted innovative strategies to prepare structurally and optically stable (∼1.5 years) MAPI under high-humid conditions could offer enhanced performance of NVBRS memory devices for medical, security, internet of things (IoT), and artificial intelligence (AI) applications.

Strain Adjustment Realizes the Photocatalytic Overall Water Splitting on Tetragonal Zircon BiVO4

Overall water splitting to generate H₂ and O₂ is vital in solving energy problem. It is still a great challenge to seek efficient visible light photocatalyst to realize overall water splitting. In this work, the tetragonal zircon BiVO₄ is prepared by epitaxial growth on FTO substrate and its overall water splitting reaction is studied. Under the influence of epitaxial strain, the conduction band position shifts negatively and beyond H⁺ /H₂ reduction potential (0 V vs NHE), which enables it to possess the photocatalytic hydrogen evolution activity. After loading cocatalysts, the overall water splitting (λ > 400 nm) is realized (H₂ : ≈65.7 µmol g^-1 h^-1 , O₂ : ≈32.6 µmol g^-1 h^-1 ), and the value of solar hydrogen conversion efficiency is 0.012%. The single-particle photoluminescence (PL) spectra and PL decay kinetics tests demonstrate the cocatalysts are beneficial to the separation and transfer of carriers. The new strategy of adjusting the band structure by strain is provided.

Visible-light-driven Z-scheme protonated g-C3N4/wood flour biochar/BiVO4 photocatalyst with biochar as charge-transfer channel for enhanced RhB degradation and Cr(VI) reduction

For the simultaneous photocatalytic reduction of hexavalent chromium (Cr(VI)) and the degradation of rhodamine B (RhB), directional charge-transfer channels and efficient separation of photogenerated holes and electrons are important. Herein, a Z-scheme heterojunction photocatalyst, protonated g-C₃N₄/BiVO₄ decorated with wood flour biochar (pCN/WFB/BiVO₄), was prepared through a hydrothermal reaction and electrostatic self-assembly for Cr(VI) photoreduction and RhB photodegradation. The morphological features, crystalline structure, chemical composition, optical properties, specific surface area, and photoelectrochemical properties of the prepared samples were investigated. The pCN/WFB/BiVO₄ photocatalyst exhibited superior removal performance when used to remove Cr(VI) and RhB separately or RhB-Cr(VI) system. The biochar bridge served as a charge-transfer channel between two semiconductors, and the electrons in protonated g-C₃N₄ (pCN) and BiVO₄ achieved a charge balance. This led to the formation of a Z-scheme heterojunction, fast photogenerated charge separation, and a powerful redox ability. The pCN/WFB/BiVO₄ photocatalyst provides new insight into the mechanisms responsible for boosting multicomponent photocatalytic reactions, while constituting a promising candidate for wastewater treatment.

Controlled Synthesis and Structural Modulation to Boost Intrinsic Photocatalytic Activity of BiVO4

Modulation of the structure, composition, and morphology through a simple refinement of the synthetic parameters are central to obtaining signature catalytic properties, enabling an understanding of the underlying growth and...

Highlights of the characterization techniques on inorganic, organic (COF) and hybrid (MOF) photocatalytic semiconductors

This review is dedicated to the brave COVID warriors fighting against the COVID-2019 pandemic.

Graphite-bridged indirect Z-scheme system TiO2-C-BiVO4 film with enhanced photoelectrocatalytic activity towards serial bisphenols

Due to the increase in the occurrence of bisphenols (BPs) in the environments, it is urgent to develop efficient and ecofriendly methods for their removal. A novel, indirect Z-scheme TiO₂-C-BiVO₄ film was prepared by a sol-gel method combined with hydrothermal carbonization. The doped graphite carbon was generated in situ from glucose, which acted as an electron-transfer bridge for the Z-scheme system to enhance the heterojunction tightness between TiO₂ and BiVO₄. This resulted in an increasing separation efficiency of photogenerated electrons and holes and a stronger redox ability of the TiO₂-C-BiVO₄ film for the degradation and detoxification of BPs. The degradation efficiency of BPs was over 95% in 240 min, except for that of 4,4'-sulphonyldiphenol (BPS) due to the presence of the OSO group, and all of the BPs were nearly completely mineralized when the reaction time reached 360 min. Consequently, the inhibition ratio towards Vibrio fischeri decreased significantly along with the loss and mineralization of aromatic intermediates during photoelectrocatalytic degradation. 2,2-bis(4-Hydroxyphenyl) butane (BPB), 4,4'-(1-phenylethylidene)-bisphenol (BPAP), and (4,4'-hexafluoroisopropylidene) diphenol (BPAF), with relatively high toxicity levels and lipophilicity and as toxic product precursors, require attention in terms of environmental safety. Overall, this work provides a promising and environmentally friendly way to remove BPs from water.

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.

Microwave-Enhanced Chemistry at Solid-Liquid Interfaces: Synthesis of All-Inorganic CsPbX3 Nanocrystals and Unveiling the Anion-Induced Evolution of Structural and Optical Properties

We demonstrate how microwaves could enhance the chemistry at interfaces of heterogeneous reactions involved in the microwave-solvothermal (MW-ST) synthesis of all-inorganic CsPbX₃ (X = Cl, Br, I) perovskite nanocrystals (PNCs) within 6 min, unlike a conventional hot-injection method that requires 3 h. The enhanced MW-ST reaction rate was quantitatively analyzed by the Eyring equation, and it has been observed that the decreased activation free energy (ΔG^⧧) and increased activation entropy (ΔS^⧧) are caused by changes in the relative energies of reactants at their solid-liquid interfaces, leading to the formation of "hot spots", where microwave energy absorption is at its maximum. This rapid and homogeneous microwave heating could facilitate the self-assembly of uniformly distributed CsPbX₃ nanocubes with precise control over the stoichiometric ratio, as confirmed by high-resolution transmission electron microscopy and energy-dispersive X-ray analyses. X-ray diffraction and Raman results indicate that lattice contraction and expansion in CsPbBr_3-yX_y have occurred because of an increase in the metal-halide bond length upon moving down the groups Cl → Br → I, as further ascertained by the Rietveld refinement studies. These anion-induced structural variations accordingly affected the electronic properties of MW-ST-synthesized CsPbX₃ PNCs, which is apparent from the shifts in their conduction-band (CB) and valence-band (VB) positions. Consequently, the optical properties were also altered, resulting in a color-tuned emission from blue to red, with excellent photoluminescence quantum yields (up to 92%) and narrow emission line widths, as is evident from UV-vis and photoluminescence spectroscopy. The MW-ST-synthesized CsPbX₃ PNCs were used as color-conversion layers for the fabrication of light-emitting diodes (LEDs) with commercial 456 nm UV-LED chips.

Easy Synthesis of BiVO4 for Photocatalytic Overall Water Splitting

Developing a photocatalyst system to generate hydrogen from water is a topic of great interest for fundamental and practical importance. In this study, we develop a new Z-scheme photocatalytic system for overall water splitting that consists of Rh/K₄Nb₆O₈ for H₂ evolution, Pt/BiVO₄ for O₂ evolution, and I^-/IO₃ ^- for an electron mediator under UV light irradiation. The oxygen evolution photocatalyst BiVO₄ was prepared by the microwave-assisted hydrothermal method. The method is fast and simple, as compared to conventional hydrothermal synthesis. The catalysts were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV-visible spectroscopy. The photocatalytic water splitting is investigated in (i) aqueous AgNO₃ as sacrificial electron scavengers and (ii) a Z-scheme photocatalytic water splitting system. The BiVO₄ photocatalysts prepared by the microwave-assisted hydrothermal method not only showed a very high oxygen evolution rate (2622 μmol g^-1 h^-1) of water splitting reaction in an aqueous AgNO₃ solution but also achieved a high H₂ evolution rate (340 μmol g^-1 h^-1) and O₂ evolution rate (172 μmol g^-1 h^-1) in a Z-scheme overall water splitting system.

Facile and rapid synthesis of a novel spindle-like heterojunction BiVO4 showing enhanced visible-light-driven photoactivity

A spindle-like monoclinic–tetragonal heterojunction BiVO₄ was successfully synthesized by a pressure-controllable microwave method. The as-prepared BiVO₄ samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, transient photocurrent responses and electrochemical impedance spectroscopy (EIS). The visible-light-driven photocatalytic activity of the BiVO₄ samples was evaluated for the degradation of Rhodamine B (RhB) and tetracycline (TC). The synthesis process needs microwave irradiation for only 10 min without the addition of any auxiliary reagent, pH adjustment, and calcination. The as-prepared spindle-like monoclinic–tetragonal heterojunction BiVO₄ exhibits excellent photocatalytic activity for the degradation of both RhB and TC. The photocatalytic degradation rates of RhB and TC over spindle-like BiVO₄ are 1.77 and 1.64 times higher, respectively, than that measured over monoclinic BiVO₄. The enhanced photocatalytic activity is mainly attributed to the fact that the existence of a heterojunction effectively promotes the separation of photo-generated carriers and extends the visible-light absorption of BiVO₄.

A novel spindle-like monoclinic–tetragonal BiVO₄ heterojunction is rapidly synthesized via a pressure-controllable microwave method.