Recent advances in bismuth vanadate-based photocatalysts for photoelectrochemical water splitting

Recent Progress in Bismuth Vanadate-Based Photocatalysts for Photodegradation Applications

Bismuth vanadate (BiVO4), a well-known semiconductor photocatalyst with various advantages, has shown great potential in addressing energy and environmental issues. However, its inherent drawbacks restrict the photocatalytic performance of pure BiVO4. In the past few years, many efforts have been devoted to improving the catalytic activity of BiVO4 and revealing the degradation mechanism in depth. In this review, we summarized the recent progress on BiVO4 in the field of photocatalytic degradation, including the strategies which enhance light absorption ability and suppress the recombination of charge carriers of BiVO4, as well as the related degradation mechanism. Finally, future prospects and challenges are summarized, which may provide new guidelines for designing more effective BiVO4-based photocatalysts for the degradation of persistent organic pollutants.

Advanced Dual-Mode Microfluidic Sensing Platform Based on Amphiphilic Polymer-Capped Perovskite Nanozymes Induced Photoelectrochemical Signal Amplification and Fluorescence Emission

A novel dual-mode microfluidic sensing platform integrating photoelectrochemical (PEC) and fluorescence (FL) sensors was developed for the sensitive monitoring of heart fatty acid binding protein (h-FABP). First, BiVO4/AgInS2 (BVAIS) composites with excellent photoelectric activity were synthesized as sensing matrices. The BVAIS heterojunction with a well-matched internal energy level structure provided a stable photocurrent. Second, an innovative signal amplification strategy based on octylamine-modified poly(acrylic acid) (OPA)-capped CsPbBr3 (OPCB) nanocrystals (NCs) with excellent catalytic activity and fluorescence property was proposed. On the OPCB nanozyme possessing ascorbate oxidase-like catalytic activity could catalyze the oxidation of ascorbic acid, which achieved quenching of the photocurrent signals by competitively consuming the electron donor. On the other hand, the OPCB NCs that overcame the water stability defect processed good luminescence performance and were able to produce obvious FL signals. Mutually verified dual-response signals effectively enhance the precision of test outcomes and avoid false-positive or false-negative results. Finally, the constructed microfluidic sensing platform realized sensitive detection of h-FABP in the linear range of 0.0001-150 ng/mL (PEC mode) and 0.001-150 ng/mL (FL mode), with detection limits of 36 fg/mL and 0.32 pg/mL, respectively. The present work provided a new perspective for designing an efficient dual-mode sensing strategy to achieve sensitive detection of disease markers.

Indium Oxide Layer Dual Functional Modified Bismuth Vanadate Photoanode Promotes Photoelectrochemical Oxidation of Water to Hydrogen Peroxide

The photoelectrochemical (PEC) dual-electron pathway for water oxidation to produce hydrogen peroxide (H2O2) shows promising prospects. However, the dominance of the four-electron pathway leading to O2 evolution competes with this reaction, severely limiting the efficiency of H2O2 production. Here, we report a In2O3 passivator-coated BiVO4 (BVO) photoanode, which effectively enhances the selectivity and yield of H2O2 production via PEC water oxidation. Based on XPS spectra and DFT calculations, a heterojunction is formed between In2O3 and BVO, promoting the effective separation of interface and surface charges. More importantly, Mott-Schottky analysis and open-circuit potential measurements demonstrate that the In2O3 passivation layer on the BVO photoanode shifts the hole quasi-Fermi level towards the anodic direction, enhancing the oxidation level of holes. Additionally, the widening of the depletion layer and the flattening of the band bending on the In2O3-coated BVO photoanode favor the generation of H2O2 while suppressing the competitive O2 evolution reaction. In addition, the coating of In2O3 can also inhibit the decomposition of H2O2 and improve the stability of the photoanode. This work provides new perspectives on regulating PEC two/four-electron transfer for selective H2O2 production via water oxidation.

Synthesis, dopant solubility, and thermostructural properties of Ca10.5-xTMx(VO4)7 (TM = Co, Cu) as function of transition metal content

Crystals of Ca10.5-xTMx(VO4)7 (TM = Co, Cu), belonging to the whitlockite family, were synthesized by solid-state reaction and studied as a function of the TM content (x) for the first time. The structure was refined at ambient conditions and at high temperatures up to 1200 K using the Rietveld method. The unit cell size significantly decreases with increasing TM content up to the solubility limit, xlim, which is 0.78(3) for TM = Co and 0.75(4) for TM = Cu. Occupancy factors show a preference for the M5 site by Co/Cu. The unit cell size varies smoothly with temperature, while the axial ratio exhibits nonlinear behaviour above approximately 800 K. The thermal expansion coefficient was determined from 300-1100 K. Atomic arrangement modifications at higher temperatures are indicated by changes in the axial ratio, the thermal expansion coefficient, and the reduction of fractional TM occupancy at the M5 site at specific temperatures.

BiVO4 Film Coupling with CoAl2O4 Nanoparticles for Photoelectrochemical Water Splitting Utilizing Broad Solar Spectrum through p-n Heterojunction, Photothermal, and Cocatalytic Synergism

Water oxidation is an endothermic and kinetics-sluggish reaction; the research of photoanodes with photothermal and cocatalytic properties is of great significance. Herein, BiVO4/CoAl2O4 film photoanodes were studied for solar water splitting through coupling spinel p-type CoAl2O4 nanoparticles on n-type BiVO4 films. Compared to the BiVO4 photoanode, better performance was observed on the BiVO4/CoAl2O4 photoanode during water oxidation. A photocurrent of 3.47 mA/cm2 was produced on the BiVO4/CoAl2O4 photoanode at 1.23 V vs RHE, which is two-fold to the BiVO4 photoanode (1.70 mA/cm2). Additionally, the BiVO4/CoAl2O4 photoanodes showed an acceptable stability for water oxidation. The BiVO4/CoAl2O4 photoanode being of higher water oxidation performance could be attributed to the presence of p-n heterojunction, cocatalytic, and photothermal effects. In specific, under the excitation of λ < 520 nm light, the holes produced in/on BiVO4 can be transferred to CoAl2O4 owing to the p-n heterojunctions of BiVO4/CoAl2O4. Meanwhile, the temperature on the BiVO4/CoAl2O4 photoanode rises quickly up to ∼53 °C under AM 1.5 G irradiation due to the photothermal property of CoAl2O4 through capturing the 520 < λ < 720 nm light. The temperature rising on the BiVO4/CoAl2O4 photoanode improves the cocatalytic activity of CoAl2O4 and modifies the wettability of BiVO4/CoAl2O4 for effective water oxidation.

Surface Plasmon Resonance-Enhanced CdS/FTO Heterojunction for Cu2+ Detection

Copper ion (Cu2+) pollution poses a serious threat to marine ecology and fisheries. However, the complexity of seawater and its interference factors make the online detection of Cu2+ quite challenging. To address this issue, we introduce the concept of the photo-assisted adjustment barrier effect into electrochemical detection, using it as a driving force to generate electrochemical responses. The Schottky barrier demonstrates a remarkable regulatory influence on the electrochemical response under photoexcitation, facilitating the response through Cu2+ adsorption. We developed a 4-MBA-AuNPs/CdS/FTO composite that serves as a sensitive platform for Cu2+ detection, achieving a detection limit of 70 nM. Notably, the photo-assisted adjustment of the barrier effect effectively counters the interference posed by ions in seawater, ensuring accurate detection. Furthermore, the sensor exhibits a promising recovery rate (99.62-104.9%) in real seawater samples, highlighting its practical applications. This innovative approach utilizing the photo-assisted adjustment barrier effect offers a promising path for developing electrochemical sensors that can withstand interference.

Integrating Co(OH)2 nanosheet arrays on graphene for efficient noble-metal-free EY-sensitized photocatalytic H2 evolution

The development of an efficient noble-metal-free cocatalyst is the key to photocatalytic hydrogen production technology. In this study, hierarchical Co(OH)2 nanosheet array-graphene (GR) composite cocatalysts are developed. With Eosin Y (EY) as a photosensitizer, the optimal Co(OH)2-10%GR hybrid cocatalyst presents excellent photocatalytic activity with an H2 production rate of 17 539 μmol g-1 h-1, and the apparent quantum yield for hydrogen production can reach 12.8% at 520 nm, which remarkably surpasses that of pure Co(OH)2 and most similar hybrid cocatalyst systems. Experimental investigations demonstrate that the excellent photocatalytic activity of Co(OH)2-GR arises from its unique nanosheet array architecture, which can collaboratively expose rich active sites for photocatalytic hydrogen evolution and facilitate the migration and separation of photogenerated charge carriers. It is desired that this study would supply a meaningful direction for the rational optimization of the constitute and structure of cocatalysts to achieve efficient photocatalytic hydrogen generation.

Exploring the Redox Properties of the Low-Miller Index Surfaces of Copper Tungstate (CuWO4): Evaluating the Impact of the Environmental Conditions on the Water Splitting and Carbon Dioxide Reduction Processes

Photocatalysis has gained significant attention and interest as an environmentally friendly and sustainable approach to the production of hydrogen through water splitting and the reduction and conversion of CO2. Copper tungstate (CuWO4) is a highly promising candidate for these applications owing to its appropriate bandgap and superior stability under different conditions. However, the redox behavior of the CuWO4 surfaces under different environments and their impact on the morphology of the material nanoparticles, as well as the electronic properties, remain poorly understood. In this study, we have employed density functional theory calculations to investigate the properties of the bulk and pristine surfaces of CuWO4 and how the latter are impacted by oxygen chemisorption under the conditions required for photocatalytic water splitting and carbon dioxide reduction processes. We have calculated the lattice parameters and electronic properties of the bulk phase, as well as the surface energies of all possible nonpolar, stoichiometric, and symmetric terminations of the seven low-Miller index surfaces and found that the (010) and (110) facets are the thermodynamically most stable. The surface-phase diagrams were used to derive the equilibrium crystal morphologies, which show that the pristine (010) surface is prominent under synthesis and room conditions. Our crystal morphologies suggest that the partially oxidized (110) surface and the partially reduced (011) surface may play an important role in the photocatalytic splitting of water and CO2 conversion, respectively. Our results provide a comprehensive understanding of the CuWO4 surfaces under the conditions of important photocatalytic applications.

Efficient Photocatalytic Reduction of Hexavalent Chromium by BiVO4-Decorated MXene Photocatalysts and Their Charge Carrier Dynamics

The synergistically MXene (Ti3C2Tx) co-catalyst-decorated BiVO4-based heterostructured photocatalysts have been synthesized by a hydrothermal approach with varied loading concentrations of MXene (Ti3C2Tx) to drive the hexavalent chromium reduction efficiently. The formation of the heterostructured photocatalyst was confirmed by the appearance of X-ray diffraction (XRD) peaks corresponding to the monoclinic BiVO4 phase and MXene (Ti3C2Tx) and also the antisymmetric (834 cm-1) and symmetric stretching (715 cm-1) of tetrahedral VO4 and D (1330 cm-1) and G (1570 cm-1) bands corresponding to MXene (Ti3C2Tx) in the Raman spectrum. The worm-like structures of BiVO4 nanocrystals grew onto the lamellar sheets of MXene (Ti3C2Tx), as shown by field emission scanning electron microscopy (FESEM), and has an increased surface area of 15.62 m2g-1 in the case of BVO-20-TC. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of V5+ and Ti3+states, and the uniform distribution of BiVO4 nanocrystals over lamellar sheets of MXene (Ti3C2Tx) is evident from energy-dispersive X-ray (EDX) analysis. The ultraviolet-diffuse reflectance spectroscopy (UV-DRS) spectra suggest a decrease in the band gap energy of BVO-20-TC to 2.335 eV, promoting a higher degree of visible light harvesting. Upon optimization, by varying the pH, the amount of the photocatalyst, and the concentration of Cr(IV), BVO-20-TC exhibits the highest photocatalytic efficiency (96.39%) while using a Cr(VI) concentration of 10 ppm at pH 2 and 15 mg of the photocatalyst, and the photoreduction of Cr(VI) to Cr(III) follows the pseudo-first-order reaction. The decrease in the PL intensity in BVO-20-TC reveals a faster transfer of electrons from MXene (Ti3C2Tx) to BiVO4. Further, the higher degree of band bending at the BiVO4/MXene (Ti3C2Tx) heterojunction, revealed from the Mott-Schottky analysis, facilitates efficient charge transfer and eventually faster and efficient photoreduction of Cr(VI) to Cr(III). The reusability and stability test undertaken for BVO-20-TC reveals that even after five cycles, the Cr (VI) photoreduction efficacy is retained. This work provides insights into photoreduction of Cr (VI) by using such heterostructures.

Photo-Induced C1 Substitution Using Methanol as a C1 Source

The development of sustainable and efficient C1 substitution methods is of central interest for organic synthesis and pharmaceuticals production, the methylation motifs bound to a carbon, nitrogen, or oxygen atom widely exist in natural products and top-selling drugs. In the past decades, a number of methods involving green and inexpensive methanol have already been disclosed to replace industrial hazardous and waste-generating C1 source. Among the various efforts, photochemical strategy is considered as a "renewable" alternative that shows great potential to selectively activate methanol to achieve a series of C1 substitutions at mild conditions, typically C/N-methylation, methoxylation, hydroxymethylation, and formylation. Herein the recent advances in selective transformation of methanol to various C1 functional groups via well-designed photochemical systems involving different types of catalysts or not is systematically reviewed. Both the mechanism and corresponding photocatalytic system were discussed and classified on specific methanol activation models. Finally, the major challenges and perspectives are proposed.

Investigation of BiVO4-based advanced oxidation system for decomposition of organic compounds and production of reactive sulfate species

Growth of population and expansion of industries lead to increasing contamination of environment with various organic pollutants. If not properly cleaned, wastewater contaminates freshwater resources, aquatic environment and has huge negative impact on ecosystems, quality of drinking water and human health, therefore new and effective purification systems are in demand. In this work bismuth vanadate-based advanced oxidation system (AOS) for the decomposition of organic compounds and production of reactive sulfate species (RSS) was investigated. Pure and Mo-doped BiVO₄ coatings were synthesized using sol-gel process. Composition and morphology of coatings were characterized using X-ray diffraction and scanning electron microscopy techniques. Optical properties were analyzed using UV-vis spectrometry. Photoelectrochemical performance was studied using linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. It was shown that increase in Mo content affects the morphology of BiVO₄ films, reduces charge transfer resistance and enhances the photocurrent in the solutions of sodium borate buffer (with and without glucose) and Na₂SO₄. Mo-doping of 5-10 at.% leads to 2- to 3-fold increase in photocurrents. Faradaic efficiencies of RSS formation ranged between 70 and 90 % for all samples irrespective of Mo content. All studied coatings demonstrated high stability in long-lasting photoelectrolysis. In addition, effective light-assisted bactericidal performance of the films in deactivation of Gram positive Bacillus sp. bacteria was demonstrated. Advanced oxidation system designed in this work can be applied in sustainable and environmentally friendly water purification systems.

Bi nanoparticles modified the WO3/ZnWO4 heterojunction for photoelectrochemical water splitting

The novel ternary photoanode was successfully prepared by Bi nanoparticles (Bi NPs) modified on type II heterojunction of WO₃-ZnWO₄ using the simple and effective drop casting and chemical impregnation methods. The photoelectrochemical (PEC) experimental tests revealed that the photocurrent density of the ternary photoanode of WO₃/ZnWO₄(2)/Bi NPs reaches 3.0 mA/cm² at 1.23 V (vs. RHE), which is 6 times of the WO₃ photoanode. The incident photon-to-electron conversion efficiency (IPCE) at 380 nm wave length reaches 68%, which increases 2.8 times compared to WO₃ photoanode. The observed enhancement can be attributed to the formation of type II heterojunction and modification of Bi NPs. The former broadens the absorption range for visible light and improves the carrier separation efficiency, while the latter enhances the light capture ability through the local surface plasmon resonance (LSPR) effect of Bi NPs and the generation of hot electrons.

Microwave-Assisted Synthesis of MoS2/BiVO4 Heterojunction for Photocatalytic Degradation of Tetracycline Hydrochloride

Compared with traditional hydrothermal synthesis, microwave-assisted synthesis has the advantages of being faster and more energy efficient. In this work, the MoS₂/BiVO₄ heterojunction photocatalyst was synthesized by the microwave-assisted hydrothermal method within 30 min. The morphology, structure and chemical composition were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM). The results of characterizations demonstrated that the synthesized MoS₂/BiVO₄ heterojunction was a spherical structure with dimensions in the nanorange. In addition, the photocatalytic activity of the samples was investigated by degrading tetracycline hydrochloride (TC) under visible light irradiation. Results indicated that the MoS₂/BiVO₄ heterojunction significantly improved the photocatalytic performance compared with BiVO₄ and MoS₂, in which the degradation rate of TC (5 mg L^-1) by compound where the mass ratio of MoS₂/BiVO₄ was 5 wt% (MB5) was 93.7% in 90 min, which was 2.36 times of BiVO₄. The active species capture experiments indicated that •OH, •O₂^- and h⁺ active species play a major role in the degradation of TC. The degradation mechanism and pathway of the photocatalysts were proposed through the analysis of the band structure and element valence state. Therefore, microwave technology provided a quick and efficient way to prepare MoS₂/BiVO₄ heterojunction photocatalytic efficiently.

Size-Specific Infrared Spectroscopic Study of the Reactions between Water Molecules and Neutral Vanadium Dimer: Evidence for Water Splitting

Investigation of the reactions between water molecules and neutral metal clusters is important in water splitting but is very challenging due to the inherent difficulty of size selection. Here, we report a size-specific infrared-vacuum ultraviolet spectroscopic study on the reactions of water with neutral vanadium dimer. The V₂O₃H₄ and V₂O₄H₆ products were characterized to have unexpected V₂(μ₂-OH)(μ₂-H)(η¹-OH)₂ and V₂(μ₂-OH)₂(η¹-H)₂(η¹-OH)₂ structures, indicative of a water decomposition. A combination of theory and experiment reveals that the water splitting by V₂ is both thermodynamically exothermic and kinetically facile in the gas phase. The present system serves as a model for clarifying the pivotal roles played by neutral metal clusters in water decomposition and also opens new avenues toward systematic understanding of water splitting by a large variety of single-cluster catalysts.

Revealing the enhanced photoelectrochemical water oxidation activity of Fe-based metal-organic polymer-modified BiVO4 photoanode

Metal-organic polymers (MOPs) can enhance the photoelectrochemical (PEC) water oxidation performance of BiVO₄ photoanodes, but their PEC mechanisms have yet to be comprehended. In this work, we constructed an active and stable composite photoelectrode by overlaying a uniform MOP on the BiVO₄ surface using Fe²⁺ as the metal ions and 2,5-dihydroxyterephthalic acid (DHTA) as ligand. Such modification on the BiVO₄ surface yielded a core-shell structure that could effectively enhance the PEC water oxidation activity of the BiVO₄ photoanode. Our intensity-modulated photocurrent spectroscopy analysis revealed that the MOP overlayer could concurrently reduce the surface charge recombination rate constant (k_sr) and enhance the charge transfer rate constant (k_tr), thus accelerating water oxidation activity. These phenomena can be ascribed to the passivation of the surface that inhibits the recombination of the charge carrier and the MOP catalytic layer that improves the hole transfer. Our rate law analysis also demonstrated that the MOP coverage shifted the reaction order of the BiVO₄ photoanode from the third-order to the first-order, resulting in a more favorable rate-determining step where only one hole accumulation is required to overcome water oxidation. This work provides new insights into the reaction mechanism of MOP-modified semiconductor photoanodes.

Recent Development Strategies for Bismuth-Driven Materials in Sustainable Energy Systems and Environmental Restoration

Bismuth(Bi)-based materials have gained considerable attention in recent decades for use in a diverse range of sustainable energy and environmental applications due to their low toxicity and eco-friendliness. Bi materials are widely employed in electrochemical energy storage and conversion devices, exhibiting excellent catalytic and non-catalytic performance, as well as CO₂ /N₂ reduction and water treatment systems. A variety of Bi materials, including its oxides, chalcogenides, oxyhalides, bismuthates, and other composites, have been developed for understanding their physicochemical properties. In this review, a comprehensive overview of the properties of individual Bi material systems and their use in a range of applications is provided. This review highlights the implementation of novel strategies to modify Bi materials based on morphological and facet control, doping/defect inclusion, and composite/heterojunction formation. The factors affecting the development of different classes of Bi materials and how their control differs between individual Bi compounds are also described. In particular, the development process for these material systems, their mass production, and related challenges are considered. Thus, the key components in Bi compounds are compared in terms of their properties, design, and applications. Finally, the future potential and challenges associated with Bi complexes are presented as a pathway for new innovations.

Abdelhamid A, Alzamly A. Visible-Light-Driven Photocatalytic Coupling of Neat Benzylamine over a Bi-Ellagate Metal-Organic Framework

Selective aerobic oxidation of benzylamine to N,N-benzylidenebenzylamine was achieved using a bismuth ellagate (Bi-ellagate) metal-organic framework (MOF) under simulated visible light irradiation. The bismuth ellagate photocatalyst was characterized using several spectroscopic techniques: powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and nitrogen sorption measurements. Product formation was confirmed using ¹H-NMR, ¹³C-NMR, and FTIR. The photocatalytic performance of Bi-ellagate was studied for the first time, which exhibits a band gap value of 2.62 eV, endowing it with a high photocatalytic activity under visible light irradiation. The reaction product, N,N-benzylidenebenzylamine, was selectively obtained with a high conversion yield of ∼96% under solvent-free conditions compared to other control experiments. The Bi-ellagate photocatalyst was recovered and reused four times without any significant loss in its activity, which provides an eco-friendly, low-cost, recyclable, and efficient photocatalyst for potential photocatalytic applications.

Morphological guided sphere to dendrite BiVO4 for highly efficient organic pollutant removal and photoelectrochemical performance under solar light

Monoclinic BiVO₄ (m-BiVO₄) has been reported as promising phase for solar light driven photocatalysis. However, in the case of morphology guided BiVO₄ with different synthetic conditions maintaining the m-BiVO₄ phase remains a substantial challenge for achieving an efficient photocatalyst driven by solar light. Herein, a simple hydrothermal approach was used to produce well-defined template free m-BiVO₄ dendrites with distinct branches for photo catalytically removal of organic pollutant and photocurrent generation. The development of monoclinic dendrite BiVO₄ was confirmed after comprehensive structural, morphological, and optical examinations. FE-SEM images of m-BiVO₄ revealed transformation of spherical to dendritic morphology with distinct branches by simply changing the HNO₃ to NaOH ratios from 2:1 to 2:2, which are named as BVO 2-1 and BVO 2-2, respectively. The BVO 2-2 dendrites exhibited improved activity of 98% towards methylene blue (MB) photodegradation upon simulated solar light irradiation. The BVO 2-2 dendrites photoelectrode showed an outstanding photocurrent density of 1.4245 mAcm^-2 than that of the BVO 2-1 spherical photoelectrode (0.7367 mAcm^-2). Enhanced photocatalytic and photoelectrochemical action, could be ascribed to the unique morphological changes provides photoactive sites, harvest more light utilization together with higher separation of e^-/h⁺ pairs. Furthermore, photocatalytic mechanism is investigated based on scavenger trapping agent, valence band XPS, UV Visible DRS and PL study. Our findings could pave the way for the development of dendritic nanostructure photocatalysts with improved photocatalytic activity.

Cobalt-plasma treatment enables structural reconstruction of a CoOx/BiVO4 composite for efficient photoelectrochemical water splitting

Cobalt-plasma sparked by a pulsed laser was utilized for the first time to modify a BiVO₄ photoanode, inducing surface structural reconstruction and CoO_x/BiVO₄ composite construction. Combining charge redistribution and cobalt, the center of hole accumulation and catalytic activity, the photoanode with optimized charge transfer capacity exhibits a 3 times improvement in photoelectrochemical water oxidation performance.

Insight into Potassium Vanadates as Visible-Light-Driven Photocatalysts: Synthesis of V(IV)-Rich Nano/Microstructures for the Photodegradation of Methylene Blue

Photocatalysis is regarded as a promising tool for wastewater remediation. In recent years, many studies have focused on investigating novel photocatalysts driven by visible light. In this study, K₂V₆O₁₆·nH₂O nanobelts and KV₃O₈ microplatelets were synthesized and investigated as photocatalysts. Samples were obtained via the facile method based on liquid-phase exfoliation with ion exchange. By changing the synthesis temperature (20–80 °C), different compositions, morphologies, and V⁴⁺/V⁵⁺ ratios were obtained and investigated as photocatalysts for organic dye degradation. Potassium vanadates’ structural, morphological, and optical properties were characterized using X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Physical Property Measurement System (PPMS), thermogravimetric analysis (TGA) with mass spectrometry (MS), N₂ adsorption, scanning electron microscopy (SEM), photoluminescence (PL), and UV–vis diffuse reflectance spectroscopy (DRS). Synthesized K₂V₆O₁₆·nH₂O and KV₃O₈ showed an efficient absorption in the visible wavelength region with a narrow band gap energy of 1.80 and 1.91 eV, respectively. Their photocatalytic activity was evaluated by the degradation of methylene blue (MB) under simulated solar light illumination. The KV₃O₈ microplatelets exhibited the greatest photocatalytic activity, resulting in more than 90% degradation of the dye within the first 30 min. It is suggested that the observed excellent photocatalytic performance is attributed to the high content of V⁴⁺ species. Furthermore, the influence of active species was investigated, and the mechanism responsible for the photodegradation of the MB dye was discussed for the first time for potassium vanadates.

Potassium vanadates were synthesized via the facile method based on liquid-phase exfoliation with ion exchange. Different synthesis temperatures (20−80 °C) resulted in various phase compositions, morphologies, and V⁴⁺/V⁵⁺ ratios. The obtained samples were demonstrated as efficient visible-light driven photocatalysts, resulting in more than 90% degradation of methylene blue within the first 30−60 min. The enhanced photoactivity is attributed to the high content of V⁴⁺ species, which are beneficial for the separation of photogenerated electrons and holes and their lifetime.