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Article

Preparation of Bismuth Vanadates with Rich Oxygen Vacancies Using Different Sol pH and Their Photocatalytic Behavior in Degradation of Methylene Blue

by
Shengli Chen
1,
Yuanyuan Zhong
1,
Jie Yang
2,
Daixiong Yang
1,
Dong Liu
3,
Xiaodong Zhu
1,4 and
Lin Huang
1,4,*
1
School of Mechanical Engineering, Chengdu University, Chengdu 610106, China
2
Department of Basic Courses, Officers College of the People’s Armed Police Force, Chengdu 610218, China
3
Sichuan Tuomai Xingzhong Technology Co., Ltd., Chengdu 610106, China
4
Sichuan Province Engineering Technology Research Center of Powder Metallurgy, Chengdu 610106, China
*
Author to whom correspondence should be addressed.
Gels 2025, 11(8), 625; https://doi.org/10.3390/gels11080625
Submission received: 8 July 2025 / Revised: 4 August 2025 / Accepted: 7 August 2025 / Published: 9 August 2025
Browse Figures
Versions Notes

Abstract

Gel precursors were formed by reacting bismuth nitrate pentahydrate, acetic acid, sodium metavanadate, and NaOH. pH was adjusted using NaOH solution followed by calcination to obtain bismuth vanadate (BiVO4) photocatalysts. During synthesis, pH directly influenced the formation and structure of the gel network. Therefore, the effects of pH on the microstructure and photocatalytic activity of BiVO4 were investigated. At pH 3, the sample consisted of microspheres formed by tightly packed small particles. At pH 5, the microspheres transformed into aggregated flakes. Photocatalytic performance was evaluated through methylene blue (MB) degradation, revealing the sample prepared at pH 7 (7-BVO) demonstrated the highest efficiency. The electronic band structure, bandgap, and band edge positions of 7-BVO were probed by density functional theory (DFT) and UV-vis absorption spectra. Furthermore, photoluminescence spectroscopy, electrochemical measurements, active species trapping experiments and liquid chromatography mass spectrometry technique collectively revealed the possible mechanistic pathways for MB photodegradation by 7-BVO.

1. Introduction

With the rapid development of the economy, pollution has become an increasingly prominent concern. Since water is essential for human life, the effective treatment of water pollutants is critical to ensuring safe water supplies [1,2,3,4]. Common water treatment methods include physical, chemical, and biological approaches [5,6,7,8]. Among these, semiconductor photocatalysis has gained significant attention due to its green, environmentally friendly nature, ability to harness solar energy, and lack of secondary pollution [9,10,11].
Bismuth-based materials have emerged as a research focus due to their high solar energy utilization efficiency [12,13,14]. Specifically, bismuth vanadate (BiVO4) has attracted attention for its narrow bandgap and unique layered structure, which promotes charge separation [15,16,17,18,19]. Nguyen et al. [15] prepared BiVO4 employing 2-methoxyethanol (MeOH), ethylene glycol (EDOH), and glycerol (PTOH) as solvents. They demonstrated that the solvent environment influenced BiVO4 crystal morphology, producing spindle-shaped crystals in EDOH and PTOH, and rod-shaped crystals in MeOH. Dhakal et al. [16] synthesized Er3+/Yb3+-doped BiVO4 using Bi(NO3)3·5H2O, NH4VO3, Yb(NO3)3·5H2O, Er(NO3)3·5H2O. By adjusting the doping ion concentration, they reduced the bandgap of BiVO4. Fluorescence lifetime measurements revealed that Er3+/Yb3+ doping prolonged the excited-state lifetime of BiVO4.
Substantial evidence confirms that heat treatment temperature significantly influences phase transitions in photocatalysts [20,21,22,23]. Baral et al. [22] studied the phase evolution of BiVO4 synthesized at heat treatment temperatures ranging from 300 °C to 600 °C. At 300 °C, the product was tetragonal BiVO4; between 400 °C and 550 °C, a tetragonal/monoclinic mixed phase was observed, and monoclinic BiVO4 formed at 600 °C. pH exerts significant regulatory control over the morphology and structure of photocatalytic materials [24,25,26,27]. Lu et al. [25] synthesized BiOBr photocatalysts at varying pH levels of 1, 3, 5, 7. Results demonstrate that grain size decreased with increasing pH. At pH 7, the catalyst exhibited a flower-like microstructure and optimal photocatalytic activity, achieving a BPA degradation rate exceeding 95% after 5-h irradiation.
In summary, both pH and calcination temperature critically determine BiVO4 properties. Crucially, pH directly governs the architecture of gel networks, thereby mediating the microstructure and photocatalytic activity. Consequently, hydrated gel precursors were synthesized from Bi(NO3)3·5H2O, NaVO3, acetic acid, and NaOH. Crystalline BiVO4 was fabricated at varying pH (3–11) under isothermal calcination. pH-dependent crystallographic and microstructural evolution was investigated. The effects of pH on crystal structure and microstructure were investigated. Photocatalytic performance was evaluated using MB solution degradation. Density functional theory (DFT), fluorescence spectrum, UV-vis absorption spectroscopy, reactive species experiments, and electrochemical measurements were used to investigate the electronic band structure, the extent of electron-hole pairs recombination, the light response range, and the main active species in the photodegradation.

2. Results and Discussion

2.1. Crystal Structure and Chemical Bond

Figure 1 shows the XRD patterns of samples prepared at different pH values (pH = 3, 5, 7, 9, 11). At pH 3 and 5, characteristic diffraction peaks appear at 18.7°, 28.8°, and 30.6°, corresponding to the (110), (121), and (040) crystal planes of monoclinic scheelite BiVO4 (m-s BiVO4) (PDF#14-0688) [17,28]. For pH 7, the intensity and position of these peaks are consistent with 3-BVO, confirming that the samples are m-s BiVO4 [18]. However, at pH 9, the intensity and position of the diffraction peaks change significantly, indicating a phase transformation. According to previous reports, BiVO4 reacts with OH− under alkaline conditions to form Bi2VO5.5 [29,30]:
BiVO4 + OH− → Bi2VO5.5
The diffraction peaks at 28.3° and 31.7° correspond to the (103) and (110) planes of tetragonal Bi2VO5.5 (PDF#51-0032), and no BiVO4 peaks is observed, confirming that 9-BVO is entirely tetragonal Bi2VO5.5. The peak intensity is lower than that at pH 3, 5, and 7, indicating reduced crystallinity. For 11-BVO, the diffraction peaks remain consistent with those of Bi2VO5.5, but with further reduced crystallinity. The calculated grain sizes for 3-BVO, 5-BVO, 7-BVO, 9-BVO, and 11-BVO are 35.7 nm, 28.7 nm, 21.3 nm, 24.0 nm, and 15.1 nm, respectively. These results indicate a decreasing trend in crystallinity and grain size with increasing pH.
Figure 2 exhibits the FT-IR spectra of BiVO4 samples prepared at different pH values. The peaks at 740 cm−1 and 840 cm−1 correspond to the asymmetric (v3) and symmetric (v1) stretching vibrations of the VO43− units [31]. The spectral feature at 520 cm−1 is assigned to the Bi–O stretching vibration [18].

2.2. Chemical Valence States Analysis

XPS spectra of 7-BVO in Figure 3a confirm the sample consisting of Bi, V, and O. To further explore the chemical states of these elements, high-resolution spectra were obtained (Figure 3b–d). Two prominent peaks at 163.7 eV and 158.5 eV are attributed to Bi 4f7/2 and Bi 4f5/2, respectively, indicating the presence of Bi3+ [32,33]. Additionally, two minor peaks at 164.9 eV and 159.4 eV suggest the existence of Bi(3+x)+ valance. Studies indicate that Bi3+ can lose additional electrons to form Bi(3+x)+, a higher oxidation state with enhanced antioxidative properties. This high-valent Bi prevents oxygen vacancies from being refilled by O atoms, thus stabilizing the oxygen vacancies [12,14]. The high-resolution V 2p spectrum shows for distinct peaks at 523.8 eV and 521.8 eV, 517.4 eV and 516.1 eV, corresponding to V 2p1/2 and V 2p3/2, respectively, indicating the presence of both V4+ and V5+ oxidation state [34,35,36]. The O 1s spectrum reveals three peaks. The peak at 529.0 eV corresponds to lattice oxygen, the peak at 531.8 eV is attributed to adsorbed oxygen, and the peak at 530.0 eV is associated with oxygen vacancies [14,37,38,39].

2.3. Morphology and Specific Surface Area Analysis

SEM images of samples at different pH values are shown at 100,000× in Figure 4. 3-BVO exhibits microspherical agglomerates formed by densely packed small particles with sizes ranging from 2 to 3 µm. At pH 5, the microspherical agglomerates transition to sheet-like structures. The agglomerates of 7-BVO, 9-BVO, 11-BVO further disperse into smaller particles.
The TEM image (Figure 5a) reveals that 7-BVO consists of dispersed rice-liked particles with sizes ranging from 50 to 80 nm. The HRTEM image (Figure 5b) shows uniform and well-defined lattice fringes, indicating high crystallinity. The measured lattice spacing of 0.302 nm corresponds to the (121) crystal plane of BiVO4 [31].
The N2 adsorption-desorption isotherms and pore volume distribution curves for 3-BVO and 11-BVO are shown in Figure 6. In Figure 6a, the specific surface areas of 3-BVO, and 11-BVO are 0.44 m2/g and 11.65 m2/g, respectively, with 7-BVO at 7.79 m2/g [18], indicating an increasing trend with higher pH. The average pore volumes of 23.77 cm3/g for 3-BVO and 21.99 cm3/g for 11-BVO in Figure 6b, whereas 7-BVO (13.55 cm3/g) demonstrates significantly lower porosity [18]. According to the specific surface area (BET) analysis and micromorphology results, 3-BVO consists of tightly packed small particles, resulting in a lower specific surface area and fewer active sites for photocatalytic reactions. In contrast, 7-BVO and 11-BVO, with their dispersed small particles, exhibit larger specific surface areas.

2.4. Photocatalytic Performance Analysis

The photocatalytic performance was evaluated through measuring the degradation of MB under light irradiation, with results shown in Figure 7a. After 30 min of dark adsorption, the amounts of adsorbed pollutants increased with rising pH values. This trend likely results from the larger agglomerate size and denser particle packing of BiVO4 crystals synthesized at pH 3 and 5, leading to a smaller specific surface area and poorer adsorption performance. In contrast, BiVO4 prepared at pH 7, 9, and 11 exhibited smaller, more dispersed particles with larger specific surface areas, consistent with the BET results.
After 1 h of illumination, the degradation degrees for 3-BVO, 5-BVO, 7-BVO, 9-BVO, and 11-BVO were 22.9%, 23.7%, 55.4%, 35.0%, and 50.8%, respectively [18]. The photocatalytic reaction follows a first-order kinetic model described by –ln(C/C0) = kt, with the first-order kinetic fitting curves shown in Figure 7b. The highest photocatalytic activity was observed for 7-BVO, with a k of value of 0.0112 min−1 [18]. Samples prepared at pH 3 and 5 exhibited poor photocatalytic performance due to their smaller specific surface areas and limited reaction sites. At pH 9 and 11, the phase transition from m-s BiVO4 to tetragonal Bi2VO5.5 occurred, accompanied by reduced crystallinity and increased amorphous Bi2VO5.5. This phase transition led to a higher recombination rate of photogenerated electron-hole pairs, thereby reducing photocatalytic efficiency.
The reusability of 7-BVO was assessed through five cyclic experiments, with results presented in Figure 8. After five cycles, the degradation efficiency of 7-BVO slightly decreased, likely due to the coverage of the photocatalyst sites [14].
XRD patterns of the sample before and after the photodegradation (Figure 9) showed no significant changes in the peak shape or position, indicating that 7-BVO retained its m-s BiVO4 structure throughout the reactions. This demonstrates the structural stability of the material during photocatalytic processes.

2.5. Photocatalytic Mechanism

In PL spectra, higher PL peak intensity indicates a higher recombination rate, which reduces the number of photogenerated carriers available for redox reactions, thereby hindering photocatalytic activity [14,39]. As shown in Figure 10, the PL peak intensity decreased initially and then increased as the pH increased from 3 to 11, with the lowest PL intensity observed at pH 7 [18]. This indicates that 7-BVO exhibits the lowest recombination rate. XPS analysis revealed the presence of highly oxidizing Bi(3+x)+ valence in 7-BVO. These ions stabilize oxygen vacancies by preventing oxygen atoms from refilling the vacancies, thereby enhancing the separation efficiency of photogenerated photocarriers.
The UV-vis absorption spectra shown in Figure 11a indicate that the light absorption range of the samples narrows with increasing pH, suggesting a reduced light response range. The band gaps (Eg) were calculated using the Tauc relation [40]:
ahv = A (hv − Eg)1/n
where h is Planck’s constant, v is the photon frequency, A is a proportional constant, and n depends on the type of semiconductor (2 for indirect and 1/2 for direct semiconductors). BiVO4, a direct semiconductor [29], showed band gap energies of 2.30 eV, 2.32 eV, 2.38 eV, 2.43 eV, and 2.76 eV for 3-BVO, 5-BVO, 7-BVO, 9-BVO, and 11-BVO, respectively [18] (Figure 11b).
Density functional theory (DFT) calculations determined the band gap, density of states (DOS), and work function of 7-BVO (Figure 12). The optimized structure in Figure 12a exhibits a narrow band gap of 2.394 eV (Figure 12b), which closely matches the 2.38 eV value derived from Tauc plot analysis. As shown in Figure 12c, the valence band maximum (VBM) is predominantly composed of O 2p orbitals, while the conduction band minimum (CBM) is dominated by V 3d states. Figure 12d presents the work function (6.868 eV), quantifying the energy required for electron emission from the Fermi level to the vacuum level [41,42].
To identify the primary reactive species, various scavengers were introduced during the photocatalytic reaction of 7-BVO (Figure 13). Adding ammonium oxalate (AO) and isopropanol (IPA) had mild impact on the degradation of MB, indicating that photogenerated holes (h+) and hydroxyl radicals (·OH) were not the main reactive species. However, the addition of benzoquinone (BQ) significantly inhibited MB degradation, with the degradation rate dropping to 27.2%, suggesting that superoxide radicals (·O2−) are the primary reactive species.
Nitroblue tetrazolium (NBT) experiments further confirmed the formation of ·O2− during the photocatalytic process. As shown in Figure 14, the absorbance of NBT decreased with increased illumination time, indicating that ·O2− reacted with NBT, producing a purple precipitate and consuming NBT in the process [43].
In electrochemical impedance spectroscopy (Figure 15), smaller semicircle radii for 7-BVO indicate lower charge transfer resistance [18], facilitating rapid migration of photogenerated carriers for photocatalytic degradation [11,39].
The liquid chromatography-mass spectrometry technique was employed to analyze the main degradation pathways and intermediate products generated during the photocatalytic degradation of MB by 7-BVO. As shown in the Figure 16, MB may undergo two main degradation pathways. It undergoes chemical reactions under the action of ·OH, h+ and ·O2−, generating intermediate products with reduced molecular weight. Eventually, MB is decomposed into CO2, H2O and other small molecules [44,45,46].

3. Conclusions

Gel precursors were synthesized from bismuth nitrate pentahydrate, acetic acid, sodium metavanadate, and NaOH. Subsequent pH modulation (pH = 3, 5, 7, 9, 11) via NaOH solution and calcination yielded bismuth vanadate (BiVO4) photocatalysts. The pH-governed structure of three-dimensional gel networks influenced the microstructure and photocatalytic performance of BiVO4 At pH 3, the sample comprised tightly packed microspheres formed by small particles. At pH 5, the microspheres transitioned into sheet-like aggregates, while at pH 7, 9, and 11, the aggregates dispersed further into fine, granular particles. Samples prepared at pH 3, 5, and 7 exhibited a m-s BiVO4 phase, whereas at pH 9 and 11, m-s BiVO4 reacted with OH−, forming a tetragonal Bi2VO5.5 phase. The specific surface area increased with rising pH (3–11). XPS analysis confirmed the presence of highly oxidizing Bi(3+x)+ valance in 7-BVO, which prevented the refilling of oxygen vacancies by oxygen atoms, ensuring oxygen vacancy stability and enhancing charge carrier separation. DFT calculations reveal that in 7-BVO, VBM is predominantly composed of O 2p orbitals, while the conduction band minimum CBM is primarily dominated by V 3d states.PL spectra revealed that 7-BVO exhibited the lowest recombination rate of photocarriers. Photocatalytic experiments demonstrated that 7-BVO exhibited the highest photocatalytic activity, achieving a 55.4% degradation degree of MB after 1 h of irradiation. Active species trapping experiments identified ·O2− as the dominant reactive species in the photocatalytic process.

4. Materials and Methods

4.1. Reagents

All reagents used in this experiment were of analytical grade. Sodium metavanadate, bismuth nitrate pentahydrate, glacial acetic acid, sodium hydroxide, 1,4-benzoquinone (BQ), ammonium oxalate (AO), isopropanol (IPA), methylene blue (MB), and nitroblue tetrazolium chloride (NBT), were purchased from Chengdu Kelong Chemical Co., Ltd. (Chengdu, China). Poly vinylidene fluoride (PVDF), was purchased from Zhengzhou Jinghong New Energy Technology Co., Ltd. (Zhengzhou, China), and N-Methyl-2-pyrrolidone (NMP), was purchased from Titan Scientific Co., Ltd. (Shanghai, China).

4.2. Synthesis of Photocatalytic Materials

Bismuth nitrate pentahydrate (5 mmol, 2.425 g) was dissolved in 50 mL of 1 M acetic acid to form a homogeneous bismuth-based precursor sol (Sol A), where acetic acid acted as both chelating agent and reaction medium to suppress premature Bi3+ precipitation. Simultaneously, sodium metavanadate (5 mmol, 0.61 g) was dissolved in 50 mL of 1 M NaOH solution, yielding a stable vanadate ion sol (Sol B). Under continuous stirring, Sol B was dropwise added to Sol A to initiate hydrolysis and condensation between Bi3+ and VO43− ions, establishing primary Bi-O-V linkages. The pH was subsequently adjusted to predetermined values (3, 5, 7, 9, 11) using 1 M NaOH-a critical parameter governing hydrolysis/polycondensation kinetics, colloidal surface charge, and sol stability that directly determined gel network formation. The mixture was then magnetically stirred at 80 °C for 60 min, enabling enhanced Bi-O-V network growth, particle aging/crosslinking, and viscosity increase that facilitated sol-to-gel transition, ultimately yielding a yellow suspension. Precipitates were collected by centrifugation, washed with deionized water to remove ionic residues, and dried to obtain xerogel precursors. Subsequent calcination at 400 °C for 1 h in a muffle furnace eliminated organic/hydroxyl species while converting amorphous networks to crystalline BiVO4. Final products were ground and labeled as x-BVO (x = 3, 5, 7, 9, 11) according to synthesis pH.

4.3. Characterization

The phase compositions were analyzed using a DX-2700 X-ray diffractometer (Dandong Haoyuan Instrument Co., Ltd., Dandong, China). Surface morphology was examined using an FEI-nspect F50 SEM (Boyue Instrument Co., Ltd., Shanghai, China) and an FEI Tecnai G2 F20 TEM/HRTEM (Fortress Energy Incorporated Company, Oregon, OR, USA). Elemental Analysis: Elemental composition and valence states were analyzed using an XSAM800 multifunctional surface analysis system (Kratos Analytical, Manchester, UK). Nitrogen adsorption-desorption data were recorded using a Micromeritics ASAP 2460 analyzer (Beijing Guanyuan Technology Co., Ltd., Beijing, China) to determine surface area and porosity. UV-vis absorption spectra were characterized using a UT-1950 double-beam UV-vis spectrophotometer (Puxi Instrument and Meter Co., Ltd., Shanghai, China). The rate of electron-hole pairs recombination was assessed using a Hitachi F-4600 fluorescence spectrophotometer (Techcomp Instrument Co., Ltd., Shanghai, China). Photocatalytic performance was evaluated using a DH7000 electrochemical workstation (Jiangsu Donghua Analytical Instruments Co., Ltd., Jingjiang, China).

4.4. Photocatalytic Activity Test

A 25 mg sample was added to 100 mL of a 15 mg/L MB solution. The mixture was stirred in the dark for 30 min to achieve adsorption equilibrium. 350 W xenon lamp (NBeT, Beijing, China) was then used to irradiate the solution for 1 h. During irradiation, 2 mL aliquots were taken every 10 min, centrifuged, and the absorbance at 664 nm was measured via UV-vis spectrophotometer.

4.5. Active Species Trapping Experiment

Ammonium oxalate (AO), benzoquinone (BQ), and isopropanol (IPA) were used to capture photogenerated holes (h+), superoxide radicals (·O2−), and hydroxyl radicals (·OH), respectively. For each experiment, 2 mL of a 2 mmol/L trapping agent was added to the photocatalytic system, keeping all other conditions constant. Results were compared with a control group to determine the active species involved.

4.6. NBT Reduction Test

25 mg of BiVO4 was dissolved in 100 mL of 5 mmol/L nitroblue tetrazolium (NBT) solution. The suspension was irradiated for 1 h, with samples taken every 10 min. After centrifugation, the supernatant was analyzed by UV-vis spectroscopy to measure changes in absorbance at 259 nm.

Author Contributions

S.C.: Methodology, Writing-original draft, Data analysis. Y.Z.: Data analysis, Writing-original draft. J.Y.: Data analysis. D.Y.: Data analysis. D.L.: Data analysis. X.Z.: Investigation, Project administration. L.H.: Investigation, Project administration, Writing-review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Dataset available on request from the authors.

Conflicts of Interest

Author Dong Liu was employed by the company “Sichuan Tuomai Xingzhong Technology Co., Ltd.”. The remaining authors declare that the research was conducted in the absence of any com-mercial or financial relationships that could be construed as a potential conflict of interest.

References

  1. Dou, L.; Jin, X.; Chen, J.; Zhong, J.; Li, J.; Zeng, Y.; Duan, R. One-pot solvothermal fabrication of S-scheme OVs-Bi2O3/Bi2SiO5 microsphere heterojunctions with enhanced photocatalytic performance toward decontamination of organic pollutants. Appl. Surf. Sci. 2020, 527, 146775. [Google Scholar] [CrossRef]
  2. Baral, S.C.; Maneesha, P.; Datta, S.; Dukiya, K.; Sasmal, D.; Samantaray, K.S.; Br, V.K.; Dasgupta, A.; Sen, S. Enhanced photocatalytic degradation of organic pollutants in water using copper oxide (CuO) nanosheets for environmental application. JCIS Open 2024, 13, 100102. [Google Scholar] [CrossRef]
  3. Madkhali, N.; Prasad, C.; Malkappa, K.; Choi, H.Y.; Govinda, V.; Bahadur, I.; Abumousa, R.A. Recent update on photocatalytic degradation of pollutants in waste water using TiO2-based heterostructured materials. Results Eng. 2023, 17, 100920. [Google Scholar] [CrossRef]
  4. Aljawrneh, B.; Ocak, Y.S.; Albiss, B.A.; Dwiri, A.; Tawalbeh, M.; Al-Othman, A. ZrO2 nanoparticles for effective dye degradation in wastewater: Synthesis, characterization, and photocatalytic performance under sunlight. J. Alloys Compd. 2024, 1008, 176522. [Google Scholar] [CrossRef]
  5. Sendão, R.M.S.; Esteves Da Silva, J.C.G.; Pinto Da Silva, L. Photocatalytic removal of pharmaceutical water pollutants by TiO2–carbon dots nanocomposites: A review. Chemosphere 2022, 301, 134731. [Google Scholar] [CrossRef] [PubMed]
  6. Kato, S.; Sakai, Y.; Guan, G.; Kansha, Y. Illumination conditions of photocatalyst-containing mist on the degradation of organic compounds. em. Eng. Chem. Eng. Process. 2025, 208, 110106. [Google Scholar] [CrossRef]
  7. Yifira, M.T.; Mersha, A.K.; Gebreslassie, G.; Mekonnen, K.N. Cellulose-based photocatalytic membranes for dye degradation: A review. Carbohydr. Polym. Technol. Appl. 2024, 8, 100589. [Google Scholar] [CrossRef]
  8. Mishra, S.; Sundaram, B. A review of the photocatalysis process used for wastewater treatment. Mater. Today Proc. 2024, 102, 393–409. [Google Scholar] [CrossRef]
  9. Zhu, X.; Qin, F.; Luo, Y.; Zhang, L.; Yang, D.; Feng, W.; Chen, S. Enhanced photocatalytic activity of p (BaSnO3)-n (anatase/rutile/brookite TiO2) heterojunction composites by efficient interfacial charge transfer. J. Mol. Struct. 2023, 1294, 136440. [Google Scholar] [CrossRef]
  10. Qin, F.; Luo, Y.; Yu, Q.; Cheng, J.; Qin, Q.; Zhu, X.; Feng, W. Enhanced charge transfer and photocatalytic activity of BiOBr/Bi2WO6 p-n heterojunctions. J. Mol. Struct. 2024, 1304, 137719. [Google Scholar] [CrossRef]
  11. Dou, L.; Li, J.; Long, N.; Lai, C.; Zhong, J.; Li, J.; Huang, S. Fabrication of 3D flower-like OVs-Bi2SiO5 hierarchical microstructures for visible light-driven removal of tetracycline. Surf. Interfaces 2022, 29, 101787. [Google Scholar] [CrossRef]
  12. Xu, N.; Li, C.; Lin, X.; Lin, X.; Zhao, X.; Nan, J.; Xiao, X. Design of atomically dispersed N-Bi(3+x)+–OV sites in ultrathin Bi2O2CO3 nanosheets for efficient and durable visible-light-driven CO2 reduction. Appl. Catal. Gen. 2024, 680, 119776. [Google Scholar] [CrossRef]
  13. Qin, F.; Xia, Y.; Yang, D.; Xiao, T.; Zhu, X.; Feng, W.; Qi, Z. Enhanced photocatalytic activity of g-C3N4/Bi2WO6 heterojunction via Z-scheme charge-transfer mechanism. J. Mol. Struct. 2024, 1316, 139023. [Google Scholar] [CrossRef]
  14. Hou, W.; Xu, H.; Cai, Y.; Zou, Z.; Li, D.; Xia, D. Precisely control interface OVs concentration for enhance 0D/2D Bi2O2CO3/BiOCl photocatalytic performance. Appl. Surf. Sci. 2020, 530, 147218. [Google Scholar] [CrossRef]
  15. Nguyen, T.D.; Hong, S.S. Facile solvothermal synthesis of monoclinic-tetragonal heterostructured BiVO4 for photodegradation of Rhodamine B. Catal. Commun. 2020, 136, 105920. [Google Scholar] [CrossRef]
  16. Dhakal, D.R.; Kshetri, Y.K.; Chaudhary, B.; Choi, J.; Murali, G.; Kim, T.H. Enhancement of upconversion luminescence in Yb3+/Er3+-doped BiVO4 through calcination. Mater. Today Commun. 2023, 37, 107258. [Google Scholar] [CrossRef]
  17. Zhang, S.; Ou, X.; Yang, X.; Wang, D.; Zhang, C. Preparation and properties of Al3+-doped BiVO4 semiconductor photocatalyst. Chem. Phys. Lett. 2021, 778, 138747. [Google Scholar] [CrossRef]
  18. Zhong, Y.; Chen, S.; Xiao, T.; Zhu, X.; Feng, W.; Qi, Z. Interfacial modification of BiVO4 photocatalyst: Construction of heterojunction with AgI. J. Phys. Chem. Solids 2025, 202, 112691. [Google Scholar] [CrossRef]
  19. Zhang, H.; Cao, Y.; Han, J.; Wang, S.; Zhang, Z.; Wei, Z.; Wu, Z.; Zhu, Y.; Guo, Q. An investigation of Z-scheme homojunction BiVO4 photocatalysts for efficient green removal of ammonia nitrogen. J. Alloys Compd. 2024, 1008, 176640. [Google Scholar] [CrossRef]
  20. Yan, S.; Liang, X.; Liu, S.; Zhang, Y.; Zeng, J.; Bai, J.; Zhu, X.; Li, J. Synthesis of PANI@α-Fe2O3/Al2O3 photo-fenton composite for the enhanced efficient methylene blue removal. J. Sol-Gel Sci. Technol. 2024, 109, 137–149. [Google Scholar] [CrossRef]
  21. Nguyen, H.P.; Gyawali, G.; Jo, Y.H.; Kim, T.H.; Lee, S.W. Effect of heat treatment on ultrasonic synthesized bismuth ferrites: An effective visible light-driven photocatalyst. Res. Chem. Intermed. 2017, 43, 5113–5122. [Google Scholar] [CrossRef]
  22. Baral, B.; Reddy, K.H.; Parida, K.M. Construction of m-BiVO4/t-BiVO4 isotype heterojunction for enhanced photocatalytic degradation of norfloxacine and oxygen evolution reaction. J. Colloid Interface Sci. 2019, 554, 278–295. [Google Scholar] [CrossRef]
  23. Abo El-Yazeed, W.S.; El-Hakam, S.A.; Salah, A.A.; Ibrahim, A.A. Fabrication and characterization of reduced graphene-BiVO4 nanocomposites for enhancing visible light photocatalytic and antibacterial activity. J. Photochem. Photobiol. Chem. 2021, 417, 113362. [Google Scholar] [CrossRef]
  24. Sayan, M.; Akhan, S.C. Antiviral drug-associated potential vaccine-escape hepatitis B virus mutants in turkish patients with chronic hepatitis B. Int. J. Infect. Dis. 2011, 15, 722–726. [Google Scholar] [CrossRef] [PubMed][Green Version]
  25. Lu, L.; Zhou, M.; Yin, L.; Zhou, G.; Jiang, T.; Wan, X.; Shi, H. Tuning the physicochemical property of BiOBr via pH adjustment: Towards an efficient photocatalyst for degradation of bisphenol A. J. Mol. Catal. Chem. 2016, 423, 379–385. [Google Scholar] [CrossRef]
  26. Ma, Q.; Ke, J.; Ma, W.; Chen, X.; Yi, Z.; Yang, H. Influence of pH adjustment and surfactant addition on the particle morphology and photocatalytic performance of hydrothermally synthesized BiVO4. Opt. Mater. 2023, 146, 114532. [Google Scholar] [CrossRef]
  27. Yang, Z.; Ma, X.; Liu, J.; Wang, Y.; Li, H.; Zhang, X.; Li, R. Facile fabrication of visible-light-responsive BiVO4 oxygen evolution photocatalysts with tunable band gap structure. Mater. Lett. 2024, 370, 136786. [Google Scholar] [CrossRef]
  28. Cao, D.; Wang, Y.; Qiao, M.; Zhao, X. Enhanced photoelectrocatalytic degradation of norfloxacin by an Ag3PO4/BiVO4 electrode with low bias. J. Catal. 2018, 360, 240–249. [Google Scholar] [CrossRef]
  29. Kohri, H.; Yagasaki, T. Effect of element substitution at V site on thermoelectric properties of aurivillius phase Bi2VO5.5. J. Electron. Mater. 2016, 45, 4928–4934. [Google Scholar] [CrossRef]
  30. Xie, W.; Zhong, L.; Wang, Z.; Liang, F.; Tang, X.; Zou, C.; Liu, G. Photocatalytic performance of Bi2VO5.5/Bi2O3 laminated composite films under simulated sunlight irradiation. Solid State Sci. 2019, 94, 1–7. [Google Scholar] [CrossRef]
  31. Xu, X.; Zhang, J.; Tao, F.; Dong, Y.; Wang, L.; Hong, T. Facile construction of Z-scheme g-C3N4/BiVO4 heterojunctions for boosting visible-light photocatalytic activity. Mater. Sci. Eng. B 2022, 279, 115676. [Google Scholar] [CrossRef]
  32. Zhao, X.; Li, K.; Shao, X.; Chen, D.; Ji, X.; Sun, M.; Lu, H.; Liu, Y. Oxygen vacancies enhanced WO3/H-BiVO4 photoanode with conformal BiVO4-layer for promoting photoelectrochemical activity. Catal. Lett. 2025, 155, 126. [Google Scholar] [CrossRef]
  33. Clament Sagaya Selvam, N.; Kim, Y.G.; Kim, D.J.; Hong, W.H.; Kim, W.; Park, S.H.; Jo, W.K. Reduced graphene oxide-mediated Z-scheme BiVO4/CdS nanocomposites for boosted photocatalytic decomposition of harmful organic pollutants. Sci. Total Environ. 2018, 635, 741–749. [Google Scholar] [CrossRef] [PubMed]
  34. Aguirre-Cortes, J.M.; Moral-Rodríguez, A.I.; Bailón-García, E.; Carrasco-Marín, F.; Pérez-Cadenas, A.F. BiVO4-based photocatalysts for the degradation of antibiotics in wastewater: Calcination role after solvothermal synthesis. Catalysts 2024, 14, 474. [Google Scholar] [CrossRef]
  35. Bao, J.; Wang, S.; Wu, J.; Fan, F.; Wang, Y.; Luo, D.; Jiang, G.; Yao, W. Enhanced photocatalytic activity of Z-scheme BiVO4 heterophase junction via giant built-in electric field. Surf. Interfaces 2024, 54, 105116. [Google Scholar] [CrossRef]
  36. Kukreti, K.; Roy, A.; Biswas, R.; Adhikari, S.D.; Himanshu, M.; Singh, R.P.; Dutta, A.; Sharma, M.P.; Yadav, K.L.; Yadav, K. Role of oxygen vacancy enriched m-BiVO4/t-BiVO4 isotype heterojunction for enhanced photocatalytic degradation of rhodamine B dye and in ferroelastic to paraelastic phase transition. Surf. Interfaces 2024, 52, 104932. [Google Scholar] [CrossRef]
  37. Chen, J.; Gao, J.; Liu, X.; Wang, P.; Yu, X.; Zhao, F.; Sun, Y.; Feng, W.; Wang, Q. Controllable phase transformation and enhanced photocatalytic performance of nano-TiO2 by using oxalic acid. Nanomaterials 2022, 12, 3019. [Google Scholar] [CrossRef]
  38. Zhu, X.; Qin, F.; Xia, Y.; Zhong, Y.; Zhang, X.; Feng, W.; Jiao, Y. Synthesis of Ag@AgCl modified anatase/rutile/brookite mixed phase TiO2 and their photocatalytic property. Nanotechnol. Rev. 2022, 11, 2916–2927. [Google Scholar] [CrossRef]
  39. Liu, Q.; Shen, J.; Yang, X.; Zhang, T.; Tang, H. 3D Reduced graphene oxide aerogel-mediated Z-scheme photocatalytic system for highly efficient solar-driven water oxidation and removal of antibiotics. Appl. Catal. B Environ. 2018, 232, 562–573. [Google Scholar] [CrossRef]
  40. Shan, L.; Ding, J.; Sun, W.; Han, Z.; Jin, L. Core–shell heterostructured BiVO4/BiVO4:Eu3+ with improved photocatalytic activity. J. Inorg. Organomet. Polym. Mater. 2017, 27, 1750–1759. [Google Scholar] [CrossRef]
  41. Zhang, X.; Hu, C.; Zhu, Z.; Zhang, Y.; Tu, S.; Zhang, Y.; Ma, T.; Chen, F.; Huang, H. Efficient piezo-photocatalysis of 0D/2D α-Fe2O3/Bi2WO6: Synergy of weak force-driven piezoelectric polarization and Z-scheme junction. J. Colloid Interface Sci. 2023, 650, 1536–1549. [Google Scholar] [CrossRef]
  42. Xu, F.; Meng, K.; Cheng, B.; Wang, S.; Xu, J.; Yu, J. Unique S-scheme heterojunctions in self-assembled TiO2/CsPbBr3 hybrids for CO2 photoreduction. Nat. Commun. 2020, 11, 4613. [Google Scholar] [CrossRef]
  43. Du, C.; Feng, W.; Nie, S.; Zhang, J.; Liang, Y.; Han, X.; Wu, Y.; Feng, J.; Dong, S.; Liu, H.; et al. Harnessing efficient in-situ H2O2 production via a KPF6/BiOBr photocatalyst for the degradation of polyethylene. Sep. Purif. Technol. 2021, 279, 119734. [Google Scholar] [CrossRef]
  44. Singh Shagolsem, B.; Mohondas Singh, N. An environmentally friendly photocatalyst for the breakdown of RhB, MB, 2,4-DCP, and TCAA: Reusable Fe3O4/Ag doped g-C3N4. J. Mol. Liq. 2024, 413, 125913. [Google Scholar] [CrossRef]
  45. Kumaravel, S.; Lee, D.S.; Niyitanga, T.; Kaliyamoorthy, S.; Hasan, I.; Balu, K. Development of 2D/2D h-MoO3/Ag/g-C3N4 heterojunction photocatalyst with enhanced photocatalytic performance for the detoxification of methylene blue and tetracycline under solar light illumination. J. Alloys Compd. 2024, 994, 174666. [Google Scholar] [CrossRef]
  46. Latifian, P.; Hosseini, S.F.; Seyed Dorraji, M.S.; Rasoulifard, M.H. Fabrication of Ti-doped Bi2S3/NiO p-n heterojunction with enhanced visible-light–driven photocatalytic activity. J. Mol. Liq. 2023, 376, 121445. [Google Scholar] [CrossRef]
Gels 11 00625 g001
Figure 1. XRD patterns of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO (3-BVO, 5-BVO, 7-BVO, 9-BVO, and 11-BVO denote BiVO4 samples prepared under pH conditions of 3, 5, 7, 9, and 11, respectively).
Figure 1. XRD patterns of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO (3-BVO, 5-BVO, 7-BVO, 9-BVO, and 11-BVO denote BiVO4 samples prepared under pH conditions of 3, 5, 7, 9, and 11, respectively).
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Gels 11 00625 g002
Figure 2. FT-IR spectra of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
Figure 2. FT-IR spectra of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
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Gels 11 00625 g003
Figure 3. XPS spectra of 7-BVO: (a) total spectra; (b) Bi 4f; (c) V 2p; (d) O 1s.
Figure 3. XPS spectra of 7-BVO: (a) total spectra; (b) Bi 4f; (c) V 2p; (d) O 1s.
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Gels 11 00625 g004
Figure 4. SEM images of samples at 100,000×: (a) 3-BVO; (b) 5-BVO; (c) 7-BVO; (d) 9-BVO; (e) 11-BVO.
Figure 4. SEM images of samples at 100,000×: (a) 3-BVO; (b) 5-BVO; (c) 7-BVO; (d) 9-BVO; (e) 11-BVO.
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Gels 11 00625 g005
Figure 5. TEM (a) and HRTEM (b) images of 7-BVO.
Figure 5. TEM (a) and HRTEM (b) images of 7-BVO.
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Gels 11 00625 g006
Figure 6. N2 adsorption desorption curves (a) and pore size distribution curves (b) of 3-BVO and 11-BVO.
Figure 6. N2 adsorption desorption curves (a) and pore size distribution curves (b) of 3-BVO and 11-BVO.
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Gels 11 00625 g007
Figure 7. Photocatalytic degradation curves (a) and first order kinetic curves (b) of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
Figure 7. Photocatalytic degradation curves (a) and first order kinetic curves (b) of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
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Gels 11 00625 g008
Figure 8. The five cyclic experiment results of 7-BVO for MB degradation.
Figure 8. The five cyclic experiment results of 7-BVO for MB degradation.
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Gels 11 00625 g009
Figure 9. XRD patterns of 7-BVO before and after the five cyclic experiments.
Figure 9. XRD patterns of 7-BVO before and after the five cyclic experiments.
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Gels 11 00625 g010
Figure 10. PL spectra of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
Figure 10. PL spectra of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
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Gels 11 00625 g011
Figure 11. UV-vis absorption spectra (a) and band gaps (b) of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
Figure 11. UV-vis absorption spectra (a) and band gaps (b) of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
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Gels 11 00625 g012
Figure 12. Optimized models (a), bandgap energies (b), density of states (DOS) (c) and work functions (d) of 7-BVO.
Figure 12. Optimized models (a), bandgap energies (b), density of states (DOS) (c) and work functions (d) of 7-BVO.
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Gels 11 00625 g013
Figure 13. Active species experiment results of 7-BVO.
Figure 13. Active species experiment results of 7-BVO.
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Gels 11 00625 g014
Figure 14. NBT absorbance curves of 7-BVO.
Figure 14. NBT absorbance curves of 7-BVO.
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Gels 11 00625 g015
Figure 15. Electrochemical impedance spectroscopy of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
Figure 15. Electrochemical impedance spectroscopy of 3-BVO, 5-BVO, 7-BVO, 9-BVO and 11-BVO.
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Gels 11 00625 g016
Figure 16. Possible degradation pathways of 7-BVO for MB.
Figure 16. Possible degradation pathways of 7-BVO for MB.
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MDPI and ACS Style

Chen, S.; Zhong, Y.; Yang, J.; Yang, D.; Liu, D.; Zhu, X.; Huang, L. Preparation of Bismuth Vanadates with Rich Oxygen Vacancies Using Different Sol pH and Their Photocatalytic Behavior in Degradation of Methylene Blue. Gels 2025, 11, 625. https://doi.org/10.3390/gels11080625

AMA Style

Chen S, Zhong Y, Yang J, Yang D, Liu D, Zhu X, Huang L. Preparation of Bismuth Vanadates with Rich Oxygen Vacancies Using Different Sol pH and Their Photocatalytic Behavior in Degradation of Methylene Blue. Gels. 2025; 11(8):625. https://doi.org/10.3390/gels11080625

Chicago/Turabian Style

Chen, Shengli, Yuanyuan Zhong, Jie Yang, Daixiong Yang, Dong Liu, Xiaodong Zhu, and Lin Huang. 2025. "Preparation of Bismuth Vanadates with Rich Oxygen Vacancies Using Different Sol pH and Their Photocatalytic Behavior in Degradation of Methylene Blue" Gels 11, no. 8: 625. https://doi.org/10.3390/gels11080625

APA Style

Chen, S., Zhong, Y., Yang, J., Yang, D., Liu, D., Zhu, X., & Huang, L. (2025). Preparation of Bismuth Vanadates with Rich Oxygen Vacancies Using Different Sol pH and Their Photocatalytic Behavior in Degradation of Methylene Blue. Gels, 11(8), 625. https://doi.org/10.3390/gels11080625

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