Bismuth vanadate aerogel coating compositions, methods of making the same, and their use in photoelectrochemical air purification

Abstract

The present application provides a kind of bismuth vanadate (BiVO4) aerogel coating composition and its preparation method. The present application uses chelation controlled sol-gel chemistry, followed by supercritical fluid drying and controlled calcination, to prepare bismuth vanadate aerogel with three-dimensional gel network, high specific surface area, small pore size and high porosity. The bismuth vanadate aerogel of the present application also has a smaller band gap, making it have a higher pollutant removal efficiency under visible light irradiation and can be widely used. The present application also provides the application of the bismuth vanadate aerogel coating in the light anode substrate of high efficiency air particulate filter (HEPA filter) and photoelectrochemical air purification system.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical air purification. More specifically, this invention provides a bismuth vanadate (BiVO4) aerogel composition and its preparation method, as well as its application in high-efficiency particulate air (HEPA) filters and photoelectrochemical air purification systems. Background Technology

[0002] Bismuth vanadate (BiVO4) is an inorganic metal oxide semiconductor composed of bismuth (Bi) 3+ ), Vanadium (V) 5+ It is composed of oxygen and is characterized by its response to visible light irradiation.

[0003] Bismuth vanadate exists in various crystal phases, among which the monoclinic scheelite phase is the most valuable in terms of technological applications because its photocatalytic and photoelectrochemical activities are superior to those of the tetragonal or zircon-type crystal systems.

[0004] Bismuth vanadate has a band gap of approximately 2.4 eV, enabling it to absorb light in the visible light spectrum, which is significantly different from traditional photocatalysts (such as titanium dioxide and TiO2) that primarily absorb ultraviolet light. Therefore, bismuth vanadate can utilize sunlight or indoor lighting for photocatalytic reactions, thus expanding its application in indoor photoelectrochemistry.

[0005] Bismuth vanadate possesses a positive valence band, enabling it to drive vigorous oxidation reactions, such as the degradation of organic pollutants, dyes, pharmaceuticals, and industrial contaminants. Furthermore, bismuth vanadate exhibits good chemical stability in aqueous solvents and is non-toxic, thus holding promise as a replacement for materials such as titanium dioxide and tungsten trioxide in existing environmental remediation technologies.

[0006] However, methods for synthesizing bismuth vanadate typically only yield particulate, thin-film, or bulk forms. Due to limitations in specific surface area and porosity, these methods reduce the photocatalytic activity, carrier separation capability, and pollutant degradation performance of bismuth vanadate.

[0007] Therefore, there is an urgent need for an improved method for synthesizing bismuth vanadate to prepare bismuth vanadate with higher specific surface area and porosity, thereby improving its performance. This invention is precisely designed to meet this need. Summary of the Invention

[0008] To meet the needs of the prior art, a first aspect of the present invention provides an aerogel coating composition based on bismuth vanadate (BiVO4). The composition comprises a bismuth source, a vanadium source, and a chelating agent. The bismuth:vanadium molar ratio of the composition is from 0.8:1 to 1.2:1, and the chelating agent:bismuth molar ratio is from 0.5:1 to 2:1.

[0009] Specifically, the aerogel coating composition has a thickness of not less than 80 μm. 2 / g high specific surface area and small average pore size of no more than 3 nanometers.

[0010] In one embodiment of the invention, the composition further comprises 1-10 molar percentage of a transition metal dopant.

[0011] In another embodiment, the transition metal dopant is selected from manganese, iron, cobalt oxide, nickel hydroxide, copper, chromium, tungsten, cadmium, molybdenum, zinc, or any combination thereof.

[0012] A second aspect of the present invention provides a method for preparing an aerogel coating composition. The method includes: (i) mixing a solution containing a bismuth source, a solution containing a vanadium source, and a chelating agent to obtain a first mixture; (ii) continuously stirring the first mixture at a temperature of 80-120°C; (iii) aging the first mixture for 2 to 12 hours to obtain a reinforced gel; (iv) drying the reinforced gel for at least 4 hours at a temperature of 200-260°C and a pressure of 4-10 MPa under supercritical fluid drying conditions to obtain an aerogel precursor; and (v) calcining the aerogel precursor at a temperature of 400-600°C for 30-90 minutes to obtain the aerogel coating composition.

[0013] A third aspect of the present invention also provides a high-efficiency particulate air (HEPA) filter coated with an aerogel coating composition. Specifically, the HEPA filter, when irradiated with a light source with a wavelength greater than 420 nanometers at a distance of 8-12 cm from the filter, exhibits a removal efficiency of not less than 95% for volatile organic compounds (VOCs).

[0014] According to an embodiment of the third aspect of the present invention, a HEPA filter coated with the above-mentioned aerogel coating composition is prepared by the following steps: (i) coating the filter with the aerogel coating composition; (ii) drying the aerogel coating composition to form a sol-gel layer with a thickness of 50 to 100 micrometers; (iii) removing the liquid components in the aerogel coating composition by supercritical fluid drying at a temperature of 200-260°C and a pressure of 4-10 MPa for a drying time of not less than 4 hours; and (iv) calcining at a temperature of 400-600°C for 30-90 minutes.

[0015] A fourth aspect of the invention provides a photoanode comprising fluorine-doped tin oxide (FTO) glass coated with an aerogel coating composition. This photoanode is characterized by its ability to remove sulfur-containing contaminants and volatile organic compounds (VOCs) at a low DC power supply of no more than 5 volts.

[0016] In one embodiment of the fourth aspect of the invention, fluorine-doped tin oxide glass is coated with an aerogel coating composition having a thickness of 50 to 200 micrometers.

[0017] In another embodiment, the photoanode can be used as a component of a photoelectrochemical air purification system. In another embodiment, the photoelectrochemical air purification system may include: a washing container having an inlet and an outlet for allowing air to enter and exit the system; a ventilation fan installed at the outlet for directing gas flow through the washing container; a photoelectrochemical cell including a liquid reservoir connected to a liquid distribution system, a stirrer located at the bottom of the liquid reservoir, a cathode (e.g., platinum) and a photoanode (including fluorine-doped tin oxide (FTO), indium tin oxide (ITO), an aluminum substrate, and a bismuth vanadate aerogel coating composition according to embodiments of the present invention); a low-voltage (e.g., not higher than 5 volts) DC power supply connected to the cathode and photoanode; an electrolyte comprising a salt solution compatible with the photocatalytic material and electrode material; and a visible light source for irradiating the photoanode coating. This photoelectrochemical air purification system is characterized by its high removal efficiency for hydrogen sulfide, sulfur dioxide, and volatile organic compounds, all of which exceed 90% removal efficiency. Attached Figure Description

[0018] The embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein:

[0019] Figure 1 Powder X-ray diffraction (P-XRD) results of bismuth vanadate with different bismuth:vanadium ratios but having the same monoclinic crystal structure are shown.

[0020] Figure 2 The ultraviolet-visible absorption spectrum of a bismuth vanadate aerogel according to an embodiment of the present invention is shown, as described in Example I below.

[0021] Figure 3 Brunauer-Emmett-Teller (BET) test results of the specific surface area of ​​a bismuth vanadate aerogel sample prepared according to an exemplary embodiment of the present invention are shown.

[0022] Figure 4 Photographs of a high-efficiency particulate air (HEPA) filter coated with bismuth vanadate aerogel according to an embodiment of the present invention are shown. From left to right, the photographs show: (a) the initial appearance of the HEPA filter before coating; (b) the HEPA filter after being dipped in the bismuth vanadate aerogel composition; (c) the dipped HEPA filter after being dried with supercritical ethanol; and (d) the HEPA filter after calcination.

[0023] Figure 5 It shows, as Figure 4 The image shown is a scanning electron microscope (SEM) image of a HEPA filter coated with bismuth vanadate aerogel.

[0024] Figure 6The present invention illustrates a process for preparing a photoanode for a photoelectrochemical air purification system by coating bismuth vanadate aerogel onto a fluorine-doped tin oxide glass.

[0025] Figure 7A and Figure 7B Showing according to Figure 6 Photoelectrochemical (PEC) properties of the prepared photoanode. Figure 7A The methylene blue test solution was shown to be... Figure 6 The photoanode shown is in the intermediate stage after PEC purification. Figure 7B The image shows the clear solution after 1 hour of purification with PEC.

[0026] Figure 8 The degradation of methylene blue by bismuth vanadate in a mixed solution of 1M sodium sulfate and 0.1M sodium sulfite is shown.

[0027] Figure 9 A schematic diagram of an air purification system equipped with a photoanode according to an embodiment of the present invention is provided. Detailed Implementation

[0028] As mentioned above, although bismuth vanadate is gradually becoming a new generation material for environmental remediation technologies, currently available synthesis methods can only produce bismuth vanadate materials with a bulk crystalline morphology. These materials have low porosity, and therefore typically have a small specific surface area and high structural density. These factors collectively limit their photocatalytic activity, including reduced light intensity, low porosity hindering carrier separation, and generally slow pollutant degradation rates.

[0029] Therefore, a first aspect of the present invention provides a specially designed bismuth vanadate synthesis formulation, which exists in the form of an aerogel coating composition rather than a conventional bulk crystal. According to one embodiment, the bismuth vanadate aerogel coating composition comprises a bismuth source, a vanadium source, and a chelating agent, wherein the bismuth:vanadium molar ratio is controlled between 0.8:1 and 1.2:1, and the chelating agent:bismuth molar ratio is between 0.5:1 and 2:1.

[0030] Typically, bismuth vanadate achieves optimal photocatalytic and photoelectrochemical performance only when its stoichiometric ratio is highly matched to the monoclinic scheelite phase. Compared to conventional bismuth vanadate synthesis methods that typically allow for large stoichiometric deviations leading to phase heterogeneity, controlling the bismuth:vanadium molar ratio from 0.8:1 to 1.2:1 can suppress the formation of secondary phases such as bismuth trioxide or vanadium pentoxide, which are mismatched with the preferred monoclinic scheelite phase. Figure 1 The powder X-ray diffraction patterns shown indicate that the structures of bismuth vanadate synthesized at bismuth:vanadium molar ratios of 0.8:1 and 1.2:1 are almost identical to those of bismuth vanadate in the monoclinic scheelite phase.

[0031] The addition of chelating agents (such as citric acid, ethylenediaminetetraacetic acid (EDTA), tannic acid, or combinations thereof) is intended to form strong coordination bonds with bismuth ions and temporarily stabilize the Bi-O coordination layer. This coordination prevents premature precipitation of bismuth oxide salts and synchronizes the condensation kinetics of bismuth and vanadium, thereby promoting the formation of Bi-OV bonds, which is crucial for constructing homogeneous metal-organic gel networks. In contrast, conventional bismuth vanadate synthesis methods lack sufficient chelation control, resulting in isolated particles that often cannot support self-supporting gels.

[0032] The resulting bismuth vanadate aerogel has a specific surface area greater than 80 m². 2 With an average pore size of less than 3 nanometers, bismuth vanadate crystals have a specific surface area of ​​less than 50 square meters per gram, and larger pore sizes (typically greater than 10 nanometers) or exhibit pore collapse. This is advantageous in coating applications and photoelectrochemical interfaces, where surface reactivity is particularly critical.

[0033] In another embodiment, a transition metal dopant of 1-10 molar percentage may be added. Suitable dopant includes, but is not limited to, manganese, iron, cobalt, nickel, copper, titanium, or chromium. When the dopant content is 1-10 molar percentage, these dopants not only maintain their function of enhancing electron mobility and suppressing carrier recombination, but also exhibit uniform dispersion due to the high specific surface area and high porosity of the aerogel. Although dopant typically segregates or forms recombination centers in dense bismuth vanadate films, in a bismuth vanadate aerogel according to an embodiment of the present invention, spatially dispersed dopant facilitates charge transport throughout the three-dimensional percolating gel network, thereby achieving a higher photocurrent density.

[0034] According to a second aspect of the present invention, a method for synthesizing the above-mentioned bismuth vanadate aerogel coating composition is provided. The method comprises: (i) mixing a solution containing a bismuth source, a solution containing a vanadium source, and a chelating agent to obtain a first mixture; (ii) continuously stirring the first mixture at a temperature of 80-120°C; (iii) aging the first mixture for 2 to 12 hours to obtain a reinforced gel; (iv) drying the reinforced gel at a temperature of 200-260°C and a pressure of 4-10 MPa under supercritical fluid drying conditions for not less than 4 hours to obtain an aerogel precursor; and (v) calcining the aerogel precursor at a temperature of 400-600°C for 30-90 minutes to obtain the aerogel coating composition.

[0035] In hydrothermal or precipitation processes, high temperatures promote grain growth, resulting in dense particles or rods. However, as mentioned above, the introduction of a chelating agent and stirring at high temperatures can increase the ligand exchange and polymerization rates, while simultaneously suppressing crystal nucleation.

[0036] The aging process further promotes Bi-OV crosslinking and gel pillar thickening without causing pore closure. This step allows the gel to maintain sufficient mechanical integrity after solvent removal, thereby preserving porosity. This aging process is crucial because gels with low mechanical strength may collapse after solvent removal, resulting in poor morphology and reduced performance in subsequent applications.

[0037] Supercritical drying removes the solvent above its critical point. Therefore, no liquid-gas interface forms, and capillary pressure is significantly reduced. While capillary forces generated during room temperature or vacuum drying can cause nanoscale pores to collapse, resulting in a dry gel or dense solid structure, supercritical drying optimally preserves the gel structure.

[0038] The final calcination step is used to remove the organic ligands and allow the monoclinic bismuth vanadate to crystallize. The designed calcination time and temperature range allows crystallization to occur within the existing support structure without sintering the support structure, thus allowing the gel network to maintain its porosity and minimizing densification.

[0039] Bismuth vanadate in aerogel form can be applied to various surfaces in different air purification systems or devices, including but not limited to high-efficiency particulate air (HEPA) filters, and as a photoanode in photoelectrochemical air purification systems when coated on fluorine-doped tin oxide (FTO) glass.

[0040] The following examples describe exemplary embodiments and characteristics of the bismuth vanadate aerogel coating composition, as well as two applications: HEPA filters and FTO glass coated with the bismuth vanadate aerogel coating composition, and evaluate their performance.

[0041] Example

[0042] I. Bismuth vanadate aerogel coating composition

[0043] An exemplary method for preparing bismuth vanadate aerogel according to an embodiment of the present invention is as follows: First, a 4% molybdenum-bismuth vanadate sol gel is prepared by dissolving bismuth nitrate pentahydrate and citric acid in nitric acid (solution A), and dissolving ammonium metavanadate and citric acid in ammonia water (solution B), wherein the bismuth:vanadium ratio is 1:1. Under stirring, solution A is added dropwise to solution B, and then ethylenediaminetetraacetic acid and a certain amount of sodium molybdate are added as a molybdenum source. The mixture is heated to remove some of the solvent, forming a uniform molybdenum-bismuth vanadate sol gel, which is then subjected to supercritical drying and finally calcined.

[0044] In the second step, bismuth molybdenum-vanadate is immersed in an aqueous solution containing nickel nitrate hexahydrate (Ni(NO3)2·6H2O), cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and boric acid (H3BO3, as a boron activator) to form a boron-doped nickel-cobalt oxide capping layer. The electrode is removed and dried, and the immersion coating is repeated as needed to adjust the loading. Finally, it is sintered at a moderate temperature to decompose the precursor and form a conformal boron-doped nickel-cobalt oxide thin film on the bismuth molybdenum-vanadate layer.

[0045] Figure 2 The UV-Vis absorption spectrum of bismuth vanadate aerogel is shown, where the x-axis "A" represents wavelength and the y-axis "B" represents absorbance. The UV-Vis absorption onset wavelength was estimated to be 542.17 nm using linear extrapolation.

[0046] Therefore, the band gap of bismuth vanadate aerogel can be estimated using the following formula: , Where h represents Planck's constant (approximately 6.626 × 10⁻⁶). -34 J·s); c represents the speed of light (approximately 2.99 × 10⁻⁶). 8 (m / s); λ represents the absorption initiation wavelength, which, after extrapolation, is 542.17 nanometers. Based on 1 eV equaling 1.6 × 10⁻⁶... -19 Based on the conversion factor of J, the band gap of bismuth vanadate aerogel is estimated to be approximately 2.29 eV, which is lower than the band gap of conventional monoclinic bismuth vanadate (approximately 2.4 eV).

[0047] The band gap is defined as the minimum photon energy required to generate electron-hole pairs, and it also represents the minimum photon energy required to drive photoexcitation. Given that photon energy is inversely proportional to photon wavelength (as shown in Equation (I) above), a lower band gap generally means that longer wavelength photons are sufficient to drive photoexcitation. In other words, the bismuth vanadate aerogel coating composition according to embodiments of the present invention can extend the range of light absorption and photoexcitation to a deeper visible light region.

[0048] The aerogel composition was also subjected to the Brunauer-Emmett-Teller (BET) test. For example... Figure 3 As shown, the test data indicates that the bismuth vanadate aerogel coating composition has a specific surface area of ​​91.08 square meters per gram and an average pore size of 1.99 nanometers.

[0049] Table 1 below lists a comparison of the surface area, average pore size, band gap, and organic dye removal performance of the bismuth vanadate aerogel coating composition according to embodiments of the present invention with those of commercially available bismuth vanadate compositions.

[0050] Table 1:

[0051] II. Bismuth vanadate aerogel coating on glass high-efficiency particulate air (HEPA) filters

[0052] According to an embodiment of a third aspect of the present invention, a bismuth vanadate aerogel coating composition is used for in-situ coating of a glass HEPA filter.

[0053] The coating method includes: (i) coating a bismuth vanadate aerogel coating composition onto a filter material; (ii) drying the aerogel composition to form a sol-gel layer with a thickness of 50-100 micrometers; and (iii) removing the liquid components in the sol-gel layer by supercritical drying and calcination.

[0054] Figure 4 The appearance of the glass HEPA filter at each stage of the above method is shown.

[0055] See Figure 5 The image shows a microscopic image of bismuth vanadate aerogel coated on a HEPA filter. The structure of the bismuth vanadate aerogel is observed to be preserved, exhibiting a complex three-dimensional network and high porosity.

[0056] Then, according to GB / T 18801-2022 standard, the removal efficiency of various contaminants on the coated HEPA filter was tested. The coated HEPA filter was installed on the air circulation device, and the light source was located about 10 cm in front of the coated HEPA filter, with an illumination wavelength greater than 420 nanometers. The test results are shown in Table 2 below.

[0057] Table 2:

[0058] III. Photoelectrochemical Air Purification System Using Bismuth Vanadate Aerogel-Coated Photoanode

[0059] See Figure 6 According to an embodiment of the present invention, a bismuth vanadate aerogel composition is coated on a fluorine-doped tin oxide (FTO) glass surface.

[0060] One milliliter of bismuth vanadate sol-gel was coated onto the surface of FTO glass and slowly heated until viscous. The bismuth vanadate sol-gel was then spin-coated at 50 rpm for 10 seconds to ensure uniform distribution. Subsequently, supercritical ethanol drying was performed at 240°C and 8.5 MPa to remove liquid components. Finally, the coated FTO glass was calcined at 450°C. The coated FTO glass can be used as a photoanode in a photoelectrochemical system. Specifically, this photoanode does not require high voltage to operate; for example, a DC power supply of no more than 5 volts is sufficient.

[0061] like Figure 7A and 7BAs shown, the photoelectrochemical performance of the prepared photoanode was tested. The photoanode was coupled to a conventional cathode and immersed in 100 mL of a 10 ppm methylene blue solution. A 5-volt voltage was applied. A 1 M sodium-based electrolyte was used, and the solution was continuously stirred. A 300-watt xenon lamp equipped with a UV filter (wavelength greater than 420 nm) was used as the light source, positioned 5 cm away from the system under test. The initial UV-Vis absorption spectrum showed an absorbance of 1.553 at 664 nm (the unique absorption wavelength of methylene blue).

[0062] Table 3 below lists the degradation results of methylene blue.

[0063] Table 3:

[0064] For comparison, Table 4 below lists the methylene blue degradation performance of conventional photocatalysts (the bismuth vanadate samples in Table 4 are commercially available block bismuth vanadate samples).

[0065] Table 4:

[0066] Observations revealed that the photoanode prepared as described above could achieve 98% degradation of methylene blue within 60 minutes, with both degradation rate and time required being superior to other methods.

[0067] This photoanode can be used as a component of a photoelectrochemical (PEC) air purification system. Figure 9 An exemplary structure of such a PEC air purification system is schematically illustrated. The system may include: a washing container having an air inlet and an air outlet for allowing air to enter and exit the system; a ventilation fan installed at the air outlet for directing gas flow through the washing container; a photoelectrochemical cell including: a liquid reservoir connected to a liquid distribution system; a stirrer located at the bottom of the liquid reservoir; a cathode (e.g., platinum); a photoanode (including FTO, indium tin oxide (ITO), an aluminum substrate, and a coating comprising the bismuth vanadate aerogel coating composition of embodiments of the present invention); a low-voltage (e.g., not higher than 5 volts) DC power supply connected to the cathode and photoanode; an electrolyte comprising a salt solution compatible with the photocatalytic material and electrode material; and a visible light source for irradiating the photoanode coating.

[0068] As mentioned above, the photoanode installed on the air circulation device was also tested for its efficiency in removing sulfur-containing pollutants (hydrogen sulfide and sulfur dioxide) according to GB / T 18801-2022 standard. The light source was located approximately 10 cm in front of the photoanode, with an illumination wavelength greater than 420 nm. The test results showed that the photoanode's removal efficiency for both hydrogen sulfide and sulfur dioxide exceeded 90%. Similarly, the photoanode was also tested for its efficiency in removing volatile organic compounds (VOCs) (such as acetone and formaldehyde), and the results showed that its removal efficiency was also higher than 90%.

[0069] The terms “substantially,” “equivalently,” “approximately,” and “about,” as used herein, are used to describe and explain minute variations, unless otherwise defined. When used in conjunction with an event or situation, these terms can cover both cases where the event or situation has occurred completely and cases where it has occurred very close to it. For example, when used in conjunction with a numerical value, these terms can cover a range of variation less than or equal to ±10% of that value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. The term “fundamentally coplanar” can refer to two surfaces lying in the same plane and spaced within the micrometer range, such as 40 μm, 30 μm, 20 μm, 10 μm, or 1 μm.

[0070] As used herein, the singular terms “a,” “an,” and “the” may include plural references unless the context clearly specifies otherwise. In the description of some embodiments, a component that is “located” or “covers” another component may encompass situations where the former is directly located on the latter component (e.g., the former is in physical contact with the latter), and one or more intermediate components are located between the former and the latter component.

[0071] While this disclosure has been described and illustrated with reference to specific embodiments thereof, such descriptions and illustrations are not limiting. Those skilled in the art will understand that various changes and substitutions can be made and equivalents substituted without departing from the spirit and scope of this disclosure (as defined by the appended claims). Illustrations may not be drawn to scale. Due to manufacturing processes and tolerances, there may be differences between the schematic diagrams in this disclosure and actual apparatus. Other embodiments not specifically illustrated may exist in this disclosure. The specification and drawings should be considered exemplary and not limiting. Modifications may be made to particular circumstances, materials, compositions of matter, methods, or processes to conform to the purpose, spirit, and scope of this disclosure. All such modifications should be within the scope of the appended claims. While the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of this disclosure. Therefore, unless expressly stated otherwise herein, the order and grouping of operations are not limiting.

[0072] The above description of the present invention is for illustrative and explanatory purposes only and is not intended to be exhaustive or to limit the invention to the specific forms disclosed. Those skilled in the art can make numerous modifications and variations to the present invention.

[0073] These embodiments were chosen and described in order to better explain the principles of the invention and its applications, thereby enabling those skilled in the art to understand the invention in different embodiments and various modifications suitable for particular purposes.

Claims

1. A bismuth vanadate-based aerogel coating composition, characterized in that, include: Bismuth source; Vanadium source; as well as Chelating agents; The molar ratio of bismuth to vanadium in the aerogel coating composition is from 0.8:1 to 1.2:

1. Wherein, the molar ratio of the chelating agent to bismuth in the aerogel coating composition is 0.5:1 to 2:1; The specific surface area of ​​the aerogel coating composition is not less than 80 m². 2 / g; and The aerogel coating composition has an average pore size of no more than 3 nanometers.

2. The aerogel coating composition according to claim 1, characterized in that, The composition also contains 1-10 molar percentage of transition metal dopants.

3. The aerogel coating composition according to claim 2, characterized in that, The transition metal dopant is selected from oxides of manganese, iron, and cobalt, nickel hydroxide, copper, chromium, tungsten, cadmium, molybdenum, zinc, or any combination thereof.

4. The aerogel coating composition according to claim 1, characterized in that, The chelating agent is selected from citric acid, ethylenediaminetetraacetic acid, tannic acid, or any combination thereof.

5. A method for preparing the aerogel coating composition according to claim 1, characterized in that, include: A solution containing the bismuth source, a solution containing the vanadium source, and the chelating agent are mixed to obtain a first mixture; The first mixture was continuously stirred at a temperature of 80-120°C; The first mixture was aged for 2 to 12 hours to obtain a reinforced gel; Under supercritical fluid drying conditions, the reinforced gel is dried at a temperature of 200-260℃ and a pressure of 4-10 MPa for no less than 4 hours to obtain an aerogel precursor. as well as The aerogel precursor is calcined at 400-600°C for 30-90 minutes to obtain the aerogel coating composition.

6. A high-efficiency air particulate filter, coated with the aerogel coating composition according to claim 1, characterized in that, When the high-efficiency particulate air filter is irradiated with a light source with a wavelength greater than 420 nanometers at a distance of 8-12 cm, the high-efficiency particulate air filter has a removal efficiency of no less than 95% for volatile organic compounds.

7. The high-efficiency particulate air filter according to claim 6, characterized in that, The method for preparing the high-efficiency particulate air filter includes: The aerogel coating composition is applied to the high-efficiency particulate air filter; The aerogel coating composition is dried to form a sol-gel layer with a thickness of 50 to 100 micrometers on the high-efficiency particulate air filter; The liquid components in the sol-gel layer are removed by supercritical drying at a temperature of 240°C and a pressure of 8.5 MPa for a drying time of not less than 4 hours; and Calcination at 400-500℃ for 30-90 minutes.

8. A photoanode for removing sulfur-containing pollutants and volatile organic compounds, characterized in that, The photoanode comprises fluorine-doped tin oxide glass coated with the aerogel coating composition of claim 1, wherein the photoanode is operable on a DC power supply not exceeding 5 volts.

9. The photoanode according to claim 8, characterized in that, The fluorine-doped tin oxide glass is coated with the aerogel coating composition having a thickness of 50-200 micrometers.

10. A photoelectrochemical air purification system, characterized in that, The photoelectrochemical air purification system includes the photoanode according to claim 8.

11. The photoelectrochemical air purification system according to claim 10, characterized in that, include: A washing container having an air inlet and an air outlet for allowing air to enter and exit the system; A ventilation fan installed at the air outlet is used to allow gas to flow through the washing container; Photoelectrochemical cell, the photoelectrochemical cell comprising: Liquid distribution system; The liquid storage tank is connected to the liquid distribution system; A stirrer located at the bottom of the liquid storage tank; cathode; and The photoanode; A DC power supply with a voltage not exceeding 5 volts, the DC power supply being connected to the cathode and the photoanode; The electrolyte is a salt solution compatible with the photocatalytic material of the photoanode and the electrode material of the cathode; and A visible light source is used to illuminate the coating of the photoanode.

12. The photoelectrochemical air purification system according to claim 11, characterized in that, The cathode is made of platinum.

13. The photoelectrochemical air purification system according to claim 11, characterized in that, When the system is irradiated with visible light at a wavelength of 420 nanometers at a distance of 10 centimeters from the photoanode, the removal efficiency of hydrogen sulfide and sulfur dioxide is no less than 90%.

14. The photoelectrochemical air purification system according to claim 11, characterized in that, When the system is irradiated with visible light at a wavelength of 420 nanometers at a distance of 10 centimeters from the photoanode, the removal efficiency of the system for volatile organic compounds is not less than 90%.

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