PH-induced structural evolution,photodegradation mechanism and application of bismuth molybdate photocatalyst

In this work, we have elucidated the pH-induced structural evolution of bismuth molybdate photocatalyst based on a hydrothermal synthesis route. With increasing the pH value of precursor solution, pure Bi₂MoO₆ was synthesized at pH 2–5, Bi₂MoO₆-Bi₄MoO₉ mixture was obtained at pH 7–9, pure Bi₄MoO₉ was obtained at pH 11, and pure α-Bi₂O₃ was derived at pH 13. The as-derived samples mainly present particle-like shapes but with different particle sizes (except the observation of Bi₂MoO₆ nanowires in sample S-pH9). The photocatalytic performances between the samples were compared via the degradation of methylene blue (MB) under irradiation of simulated sunlight. The Bi₂MoO₆ sample synthesized at pH 2 exhibited the highest photodegradation performance (η(30 min) = 89.8 %, k_app = 0.05007 min^?1) among the samples. The underlying photocatalytic mechanism and degradation pathways of MB were systematically analyzed. Moreover, the photodegradation performance of the Bi₂MoO₆ photocatalyst was further evaluated at different acidic-alkaline environments as well as in degrading various color and colorless organic pollutants, which provides an important insight into its practical application.     

Novel Mo/Bi2MoO6/Bi3ClO4 heterojunction photocatalyst for ultra-deep desulfurization of thiophene under simulated sunlight irradiation

In the present work, a visible-light-driven Mo/Bi₂MoO₆/Bi₃ClO₄ heterojunction photocatalyst was fabricated via the Pechini sol–gel process. The type and amount of gelling agent, chelating agent and mole ratio of chelating agent to total metals were balanced to generate ultrafine nanoparticles. The Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite as a novel photocatalyst not only exhibited an excellent visible-light photocatalytic desulfurization performance of thiophene (~97%), but also had better photodesulfurization efficiency than Mo/Bi₂MoO₆ and Bi₃ClO₄ nanostructures. The ultra-deep photocatalytic desulfurization performance of the Mo/Bi₂MoO₆/Bi₃ClO₄ nanocomposite can be attributed to the strong visible-light absorption, unique nanostructures, high separation and low recombination of electron–hole pairs due to the as-formed heterojunctions. Furthermore, a photocatalytic desulfurization mechanism was elucidated via radical trapping experiments, which revealed that the ^?O₂^? and ^?OH radicals play a key role in the photocatalytic desulfurization process.     

Modulation of Bi2MoO6‐Based Materials for Photocatalytic Water Splitting and Environmental Application: a Critical Review

Highly active photocatalysts driving chemical reactions are of paramount importance toward renewable energy substitutes and environmental protection. As a fascinating Aurivillius phase material, Bi₂MoO₆ has been the hotspot in photocatalytic applications due to its visible light absorption, nontoxicity, low cost, and high chemical durability. However, pure Bi₂MoO₆ suffers from low efficiency in separating photogenerated carriers, small surface area, and poor quantum yield, resulting in low photocatalytic activity. Various strategies, such as morphology control, doping/defect‐introduction, metal deposition, semiconductor combination, and surface modification with conjugative π structures, have been systematically explored to improve the photocatalytic activity of Bi₂MoO₆. To accelerate further developments of Bi₂MoO₆ in the field of photocatalysis, this comprehensive Review endeavors to summarize recent research progress for the construction of highly efficient Bi₂MoO₆‐based photocatalysts. Furthermore, benefiting from the enhanced photocatalytic activity of Bi₂MoO₆‐based materials, various photocatalytic applications including water splitting, pollutant removal, and disinfection of bacteria, were introduced and critically reviewed. Finally, the current challenges and prospects of Bi₂MoO₆ are pointed out. This comprehensive Review is expected to consolidate the existing fundamental theories of photocatalysis and pave a novel avenue to rationally design highly efficient Bi₂MoO₆‐based photocatalysts for environmental pollution control and green energy development.     

Comparison Between γ-Bi2MoO6 and Bi2WO6 Catalysts in the CO Oxidation

Bismuth molybdate (-Bi₂MoO₆) and bismuth tungstate (Bi₂WO₆) catalysts were prepared by solid-state reaction and their catalytic properties evaluated in the CO oxidation reaction. We characterize their structure by X-ray diffraction, scanning electron microscopy, Auger electron spectroscopy, and BET nitrogen absorption. X-ray diffraction analysis shows that both -Bi₂MoO₆ and Bi₂WO₆ are structural analogs (SG P2₁ ab). Auger analysis shows that Bi₂WO₆ catalysts have more bismuth on the surface than -Bi₂MoO₆, although both samples are bismuth deficient as compared to the stoichiometric compound. The results regarding catalytic activity show that Bi₂WO₆ prepared at 1073 K reaches total conversion of CO (100%) at a lower temperature when compared to -Bi₂MoO₆. It indicates that Bi₂WO₆ is a potential candidate to be used as catalyst in the CO to CO₂ oxidation.     

Fabrication of plate-on-plate Z-scheme SnS<Subscript>2</Subscript>/Bi<Subscript>2</Subscript>MoO<Subscript>6</Subscript> heterojunction photocatalysts with enhanced photocatalytic activity

A class of direct plate-on-plate Z-scheme heterojunction SnS₂/Bi₂MoO₆ photocatalysts was synthesized via a two-step hydrothermal method. The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, Fourier transform infrared photoluminescence emission spectra, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity was estimated via the degradation of crystal violet (CV) and ciprofloxacin (CIP). The experimental results indicated that the 5 wt% SnS₂/Bi₂MoO₆ composites exhibited significantly enhanced performance in contrast to pure Bi₂MoO₆ or SnS₂ nanoflakes, and were also superior to the popular TiO₂ (P25). The degradation reaction accorded well with the first-order reaction kinetics equation; the rate constant of CV using a SnS₂ content of 5 wt% photocatalyst was ~?3.6 times that of the Bi₂MoO₆ and 2.4 times that of SnS₂. Furthermore, a SnS₂ content of 5 wt% exhibited a 1.7 times higher photocatalytic activity of CIP than that of pure Bi₂MoO₆, and 1.3 times that of pure SnS₂. Radical trapping experiments and an electron spin resonance technique indicated that h⁺ and ·OH were the dominant active species involved in the degradation process. A plasmonic Z-scheme photocatalytic mechanism was proposed to explain the superior photocatalytic activities and efficient separation of photogenerated electrons and holes.     

Crystal growth and physical properties of ternary bismuth molybdenum oxides Bi x MoO y (x=0.21, 0.25; y=3 + δ)

Large purple-brown crystals of two reduced bismuth molybdenum oxides have been grown from the MoO₃–Bi₂O₃ system by electrolytic reduction of the molten salts. The unit cell parameters and the compositions have been determined by X-ray diffraction and XPS microprobe analysis, respectively. The empirical formulae were refined to Bi_0.25MoO_3.1 and Bi_0.21MoO_3.2. Transport measurements (the resistivity and the thermoelectric power) showed that both crystals are semiconductors with p-type carriers, and the thermally activated energy gaps are respectively about 0.296 eV and 0.30 eV. The EPR spectra, the XPS core-level spectra and possible structural features were also considered.     

Unveiling nanoplates-assembled Bi2MoO6 microsphere as a novel anode material for high performance potassium-ion batteries

Bismuth (Bi)-based electrode has aroused tremendous interest in potassium-ion batteries (PIBs) on account of its low cost, high electronic conductivity, low charge voltage and high theoretical capacity. However, the rapid capacity fading and poor lifespan induced by the normalized volume expansion (up to ~ 406%) and serious aggregation of Bi during cycling process hinder its application. Herein, bismuth molybdate (Bi₂MoO₆) microsphere assembled by 2D nanoplate units is successfully prepared by a facile solvothermal method and demonstrated as a promising anode for PIBs. The unique microsphere structure and the self-generated potassium molybdate (K-Mo-O species) during the electrochemical reactions can effectively suppress mechanical fracture of Bi-based anode originated from the volume variation during charge/discharge of the battery. As a result, the Bi₂MoO₆ microsphere without hybridizing with any other conductive carbon matrix shows superior electrochemical performance, which delivers a high reversible capacity of 121.7 mAh·g⁻¹ at 100 mA·g⁻¹ over 600 cycles. In addition, the assembled perylenetetracarboxylic dianhydride (PTCDA)//Bi₂MoO₆ full-cell coupled with PTCDA cathode demonstrates the potential application of Bi₂MoO₆ microsphere. Most importantly, the phase evolution of Bi₂MoO₆ microsphere during potassiation/depotassiation process is successfully deciphered by ex situ X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) technologies, which reveals a combination mechanism of conversion reaction and alloying/dealloying reaction for Bi₂MoO₆ anode. Our findings not only open a new way to enhance the performance of Bi-based anode in PIBs, but also provide useful implications to other alloy-type anodes for secondary alkali-metal ion batteries.

     

Oxide-ion-conducting phases in the Bi2MoO6-Bi2VO5.5 system

In search of new oxide-ion-conducting phases, we have synthesized a series of Bi₂V_1?x Mo _x O_5.5+x/2 ceramic samples, in which the end-members Bi₂VO_5.5 (x = 0) and Bi₂MoO₆ (x = 1) are single-layer Aurivillius phases, possess ferroelectric properties, and offer high oxide-ion conductivity. We have determined the phase composition of the samples and have investigated their electrical properties. The results indicate the formation of narrow ranges of Bi₂VO_5.5-and Bi₂MoO₆-based solid solutions (0 < x ≤ 0.1 and 0.9 ≤ x < 1, respectively). In the composition range 0.2 ≤ x ≤ 0.8, the samples consist of Bi₂VO_5.5-or Bi₂MoO₆-based solid solutions and compounds isostructural with BiVO₄ and Bi₆Mo₂O₁₅. Molybdenum doping stabilizes the orthorhombic phase β-Bi₂VO_5.5 to room temperature, but the solid solutions differ little in electric conductivity from Bi₂VO_5.5. The conductivity of the Bi₂MoO₆-based solid solutions is higher than that of undoped bismuth molybdate by about a factor of 3.     

Polymorphism and properties of Bi<Subscript>2</Subscript>W<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mo<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>6</Subscript> aurivillius phases

A continuous series of Bi₂W_{1 − x} Mo _x O₆ solid solutions between the n = 1 Aurivillius phases Bi₂WO₆ and Bi₂MoO₆ with a polar orthorhombic structure (γ-phase) have been prepared by solid-state reactions at 850 (0 < x ≤ 0.3) and 530–640°C (0.3 ≤ x < 1), and their thermal and electrical properties have been studied throughout their stability region, between room temperature and 960°C, with the aim of gaining detailed insight into their polymorphism. The results demonstrate that the tungsten-rich (0 ≤ x ≤ 0.2) materials undergo a ferroelectric and a reconstructive phase transition like bismuth tungstate, Bi₂WO₆. The temperatures of both transitions decrease with increasing molybdenum content. The molybdenum-rich materials in the composition range 0.9 ≤ x ≤ 1 are similar in properties to bismuth molybdate, Bi₂MoO₆. In the composition range 0.3 ≤ x ≤ 0.8, neither ferroelectric nor reconstructive phase transition was detected.     

Mechanochemical homodisperse of Bi2MoO6 on Zn-Al LDH matrix to form Z-scheme heterojunction with promoted visible-light photocatalytic performance

In this work, a Z-scheme Bi₂MoO₆/Zn-Al LDH heterojunction photocatalyst with excellent visible light responsiveness was fabricated via a two-step mechanochemical ball-milling process, where amorphous Bi₂MoO₆ particles were homodispersed upon the surface of lamellar LDH matrix. BPA was selected as the targeted organic contaminant to quantitatively evaluate the photocatalytic capacity of Bi₂MoO₆/Zn-Al LDH, in which the optimal 30 wt%Bi₂MoO₆/LDH exhibited a degradation rate of 96% within 300 min, over 9.25 and 18.5 times higher than that of individual pristine Bi₂MoO₆ and LDH, respectively. The crystal structure, microtopography, interfacial physicochemical interaction, optical and electrochemical properties of as-fabricated hybrids were systematically evaluated, and the DFT theoretical calculation was used to confirm the electronic structural characteristics in the Bi₂MoO₆/LDH heterojunction. A possible photocatalysis reaction mechanism was interpreted through ESR where the major manner of ?O^2– proved the Z-scheme electron migration within matched band levels.     

Synergistic effect of visible-light-driven FeOOH@Bi2MoO6 for removal of ciprofloxacin over a wide pH range: Efficient separation of photogenerated carriers and fast Fe(III)/Fe(II) cycling

Fabrication of FeOOH@Bi₂MoO₆ composites was successfully carried out by the solvent thermal-impregnation method, and they were used as effective visible light-driven photo-Fenton catalysts. The catalyst can achieve effective degradation of CIP in the pH range of 3.5–10.5, which overcomes the problems of harsh pH application conditions and low H₂O₂ utilization in Fenton. Notably, FeOOH@Bi₂MoO₆ exhibited stronger photo-Fenton catalytic activity compared with pure FeOOH, pure Bi₂MoO₆ and their simple physical mixtures, indicating that the interfacial active sites of FeOOH and Bi₂MoO₆ are favorable for the rapid transfer of photogenerated electrons from Bi₂MoO₆ to FeOOH. Combined with the characterization analysis and performance experiments, the catalytic mechanism of the FeOOH@Bi₂MoO₆-H₂O₂ system is reasonably proposed. The photocatalytic-Fenton synergy facilitates the rapid separation of photogenerated carriers and the valence cycling of Fe(III)/Fe(II), which drives the reaction system to produce a large amount of OH, O₂^? and a small amount of h⁺ to participate in the degradation process of CIP. In this study, the preparation of composite catalysts and the coupled use of photocatalytic-Fenton provided a feasible idea to overcome the problems of narrow pH application and low H₂O₂ utilization in Fenton.     

Construction of 3D marigold-like Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript>/Ag<Subscript>2</Subscript>O/CQDs heterostructure with superior visible-light active photocatalytic activity toward tetracycline degradation and selective oxidation

A novel visible-light-driven photocatalyst Bi₂WO₆/Ag₂O/CQDs (BWO/Ag₂O/CQDs), which possesses hierarchical superstructure with marigold-like appearance, was fabricated via a hydrothermal method, followed by a simple precipitation process. Ag₂O nanoparticles sized around 25 nm and CQDs with diameters of about 10 nm were evenly deposited on Bi₂WO₆ to form a unique heterostructure. The obtained BWO/Ag₂O/CQDs heterostructure showed excellent adsorption and remarkably enhanced photocatalytic performance in the photodegradation of antibiotic tetracycline (TC) under visible-light irradiation compared to pristine Bi₂WO₆. The degradation rate of TC over BWO/Ag₂O/CQDs photocatalyst is 16.2 times higher than that of pristine Bi₂WO₆ and a possible mechanism for the enhanced photocatalytic performance was discussed. In addition, BWO/Ag₂O/CQDs was applied in the selective oxidation of benzyl alcohol to benzaldehyde under visible-light illumination. The result demonstrated that the conversion rate and product selectivity are greatly improved over BWO/Ag₂O/CQDs compared to pristine Bi₂WO₆ in the same reaction conditions, making it a promising photocatalyst in the application of green chemical transformation. The co-coupling of CQDs and Ag₂O with matched band potentials gives a substantial promotion for the light harvesting ability and effective separation of photogenerated charge carriers, synergistically accounting for the improvement of photocatalytic efficiency.     

Sonochemical assisted impregnation of Bi2WO6 on TiO2 nanorod to form Z-scheme heterojunction for enhanced photocatalytic H2 production

In this work, Bi₂WO₆/TiO₂ nanorod heterojunction was prepared by sonochemical assisted impregnation method. After loading 2 wt% Bi₂WO₆ on TiO₂ nanorods, the photocatalytic hydrogen production rate of 2026 µmol/h/g was achieved. Compared to commercial P25 and TiO₂ nanorods, ∼13 and ∼3 folds enhanced activity was observed. The excellent photocatalytic performance of Bi₂WO₆/TiO₂ nanorod photocatalyst was mainly attributed to i) reduction of bandgap due to heterojunction formation, ii) quick transport of photogenerated charge carriers, and iii) efficient charge carrier separation supported by UV-DRS, photocurrent measurement, Impedance study, and photoluminescence spectra analysis. The Z-scheme band alignment for Bi₂WO₆/TiO₂ nanorod heterojunction was proposed based on the Mott-Schottky measurement. This result demonstrated the effective utilization of Z-scheme heterojunction of Bi₂WO₆/TiO₂ for photocatalytic reduction application.     

Synergy-Compensation Effect of Ferroelectric Polarization and Cationic Vacancy Collaboratively Promoting CO2 Photoreduction

Photocatalytic CO₂ reduction is severely limited by the rapid recombination of photo-generated charges and insufficient reactive sites. Creating electric field and defects are effective strategies to inhibit charge recombination and enrich catalytic sites, respectively. Herein, a coupled strategy of ferroelectric poling and cationic vacancy is developed to achieve high-performance CO₂ photoreduction on ferroelectric Bi₂MoO₆, and their interesting synergy-compensation relationship is first disclosed. Corona poling increases the remnant polarization of Bi₂MoO₆ to enhance the intrinsic electric field for promoting charge separation, while it decreases the CO₂ adsorption. The introduced Mo vacancy (V_Mo) facilitates the adsorption and activation of CO₂, and surface charge separation by creating local electric field. Unfortunately, V_Mo largely reduces the remnant polarization intensity. Coupling poling and V_Mo not only integrate their advantages, resulting in an approximately sevenfold increased surface charge transfer efficiency, but also compensate for their shortcomings, for example, V_Mo largely alleviates the negative effects of ferroelectric poling on CO₂ adsorption. In the absence of co-catalyst or sacrificial agent, the poled Bi₂MoO₆ with V_Mo exhibits a superior CO₂-to-CO evolution rate of 19.75 µmol g⁻¹ h⁻¹, ≈8.4 times higher than the Bi₂MoO₆ nanosheets. This work provides new ideas for exploring the role of polarization and defects in photocatalysis.     

Synthesis of bismuth oxide nanoparticles at 100 °C

A simple gel to crystal conversion route has been followed for the preparation of ultrafine Bi₂O₃ particles at 80–100 °C under refluxing conditions. Freshly prepared bismuth hydroxide gel is allowed to crystallize under refluxing and stirring conditions for 6–12 h. Formation of nanocrystallites of Bi₂O₃ is confirmed by X-ray diffraction (XRD) study. The thermal decomposition of bismuth hydroxide yields Bi₂O₃ only at 400 °C. This shows the advantage of the present method. Transmission electron microscope (TEM) investigations revealed that the average particle size is 50 nm for these oven-dried powders.     

Facile preparation of heterostructured Bi2O3/Bi2MoO6 hollow microspheres with enhanced visible-light-driven photocatalytic and antimicrobial activity

Hierarchical β-Bi₂O₃/Bi₂MoO₆ heterostructured flower-like microspheres assembled from nanoplates with different β-Bi₂O₃ loadings (0–26.5 mol%) were synthesized through a one-step template-free solvothermal route. Under visible-light illumination (λ > 420 nm), over 99% of rhodamine B was degraded within 90 min on the 21.9 mol% of β-Bi₂O₃ loading Bi₂O₃/Bi₂MoO₆ microspheres. The remarkable enhancement of photocatalytic activity of the hierarchical Bi₂O₃/Bi₂MoO₆ micro/nanostructures can be attributed to the effective separation of the photoinduced charge carriers at the interfaces and in the semiconductors. The electrons (e⁻) are the main active species in aqueous solution under visible-light irradiation. The Bi₂O₃/Bi₂MoO₆ also displays visible-light photocatalytic activity for the destruction of E. coli. In addition, the β-Bi₂O₃ in the hierarchical Bi₂O₃/Bi₂MoO₆ microspheres is very stable and the composite can be easily recycled by a simple filtration step, thus the second pollution can be effectively avoided. A possible photocatalytic mechanism was proposed based on the experimental results.     

A Unique Etching-Doping Route to Fe/Mo Co-Doped Ni Oxyhydroxide Catalyst for Enhanced Oxygen Evolution Reaction

Fe-doped Ni (oxy)hydroxide shows intriguing activity toward oxygen evolution reaction (OER) in alkaline solution, yet it remains challenging to further boost its performance. In this work, a ferric/molybdate (Fe³⁺/MoO₄²⁻) co-doping strategy is reported to promote the OER activity of Ni oxyhydroxide. The reinforced Fe/Mo-doped Ni oxyhydroxide catalyst supported by nickel foam (p-NiFeMo/NF) is synthesized via a unique oxygen plasma etching-electrochemical doping route, in which precursor Ni(OH)₂ nanosheets are first etched by oxygen plasma to form defect-rich amorphous nanosheets, followed by electrochemical cycling to trigger simultaneously Fe³⁺/MoO₄²⁻ co-doping and phase transition. This p-NiFeMo/NF catalyst requires an overpotential of only 274 mV to reach 100 mA cm⁻² in alkaline media, exhibiting significantly enhanced OER activity compared to NiFe layered double hydroxide (LDH) catalyst and other analogs. Its activity does not fade even after 72 h uninterrupted operation. In situ Raman analysis reveals that the intercalation of MoO₄²⁻ is able to prevent the over-oxidation of NiOOH matrix from β to γ phase, thus keeping the Fe-doped NiOOH at the most active state.     

Hierarchical Bi2S3 nanoflowers: A novel photocatalyst for enhanced photocatalytic degradation of binary mixture of Rhodamine B and Methylene blue dyes and degradation of mixture of p-nitrophenol and p-chlorophenol

Hierarchical nanostructures of bismuth sulfide (Bi₂S₃) have been synthesized by a facile hydrothermal method. The potentiality of Bi₂S₃ hierarchical nanostructures for the photocatalytic degradation of Rhodamine B (RhB), Methylene blue (MB) and the mixture of RhB-MB organic dyes have been demonstrated and compared with commercial TiO₂ (Degussa P25) sample under visible light illumination. The degradation efficiency of Bi₂S₃ and Degussa P25 is found to be higher in the single as well as in the binary dye solution for MB degradation as compared to RhB degradation. Furthermore, the degradation rate of RhB and MB is enhanced by ～8 times and ～3 times in their binary solution as compared to that in single dye solution. Whereas, Bi₂S₃ has demonstrated ～14 times higher degradation rate of both RhB and MB in their binary solution than that of Degussa P25 for RhB and MB degradation in the binary solution under visible light exposure, respectively. Interestingly, Bi₂S₃ nanostructures has exhibited larger improvement in the degradation efficiency for RhB in its binary solution which is attributed to the faster separation of photogenerated charge carriers due to the proper alignments between the molecular orbits of dyes and band level positions of Bi₂S₃ in RhB-MB-Bi₂S₃ heterogenous system. The photocatalytic degradation study of colourless contaminants, p-chlorophenol (CP), p-nitrophenol (NP) and their mixture (CP-NP) is also investigated in the presence of Bi₂S₃ nanoflowers. Among the phenolic compounds, the degradation rate of NP is observed to be highest in the single solution. However, the degradation rate of both CP and NP is found to decrease in binary mixture solution in comparison to their individual solution. A possible mechanism for the enhanced photodegradation of RhB-MB dye mixture based on the active species trapping experiment has been proposed.     

Fabrication of Bi2WO6/In2O3 photocatalysts with efficient photocatalytic performance for the degradation of organic pollutants: Insight into the role of oxygen vacancy and heterojunction

Photocatalysis is an attractive and green strategy for organic pollutant removal. The development of alternative and effective photocatalysts has attracted great attention. Herein, we rationally engineer an alternative rich-oxygen vacancies (OVs) Bi₂WO₆/In₂O₃ composite photocatalyst via integrating the calcination and hydrothermal method for removing organic dyes (rhodamine B). Thanks to the synergistic effect of OVs and heterojunction structure, the 80 wt% Bi₂WO₆/In₂O₃ (BiIn80) displays enhanced photocatalytic degradation effect. The degradation rate of BiIn80 is up to 97.3% under light irradiation within 120 min and the reaction rate constant k value (0.03221 min⁻¹) is about 15-fold and 4.17-fold as high as those of In₂O₃ (0.00203 min⁻¹) and Bi₂WO₆ (0.00772 min⁻¹), respectively. The heterostructure of Bi₂WO₆/In₂O₃ can extend the lifespan of the photogenerated charge carriers. Moreover, the density functional theory (DFT) calculations reveal that the OVs in Bi₂WO₆/In₂O₃ can boost visible light absorbability by decreasing band gap value and serve as the extra electron transfer channels to enhance the separation efficiency of photogenerated electron-hole pairs. This study not only provides an alternative route for fabricating highly efficient heterojunction photocatalysts, but also obtains better understanding of the synergistic effect of OVs and heterojunction on enhancing the photocatalytic performance.     

Enhanced photocatalytic activity of bismuth molybdate via hybridization with carbon

The bismuth molybdate Bi_3.64Mo_0.36O_6.55 (BMO) was successfully synthesized by a rapid and convenient microwave-assisted method. Carbon was introduced to hybridize with BMO material (BMO/C) through the simple combination of hydrothermal process in the presence of glucose and subsequent calcination treatment in N₂ gas at 280 °C. The products were characterized by the study of X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The results indicated that carbon did not affect the final crystalline structure of BMO, but it had great influences on the photocatalytic activity of BMO towards rhodamine-B (RhB) degradation. The improved photocatalytic performance could be ascribed to the enhanced photogenerated electron-hole separation and more RhB adsorption associated with carbon.