A bismuth tungstate-molybdate solid solution photocatalyst and a preparation method thereof

Abstract

This invention relates to the field of catalytic materials technology, and particularly to a bismuth tungsten-molybdate solid solution photocatalyst and its preparation method. The preparation method includes the following steps: dissolving bismuth nitrate pentahydrate in dilute nitric acid solution and stirring until homogeneous to obtain solution A; dissolving sodium tungstate dihydrate and sodium molybdate in water at different molar ratios and stirring until homogeneous to obtain solution B; adding solution B to solution A and stirring until homogeneous to obtain solution C; adding HTAB to solution C and stirring until homogeneous to obtain solution D; subjecting solution D to a hydrothermal reaction, cooling to room temperature, and then removing the product by centrifugation, washing, and drying to obtain the bismuth tungsten-molybdate solid solution photocatalyst. The preparation method of the bismuth tungsten-molybdate solid solution photocatalyst of this invention is simple, low-cost, and allows for controllable conditions. The obtained product has a stable structure, small size, abundant specific surface area, and surface oxygen vacancies, exhibiting excellent photocatalytic performance and superior cycle stability in the degradation of gaseous toluene.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, and in particular to a bismuth tungsten-molybdate solid solution photocatalyst and its preparation method. Background Technology

[0002] Volatile organic compounds (VOCs), such as benzene, toluene, formaldehyde, and acetaldehyde, are common air pollutants, mainly originating from industrial production and building decoration materials. Due to their strong toxicity and carcinogenicity, VOCs cause serious harm to human life and the living environment. In recent decades, the elimination of VOCs has attracted widespread attention, with researchers employing various technologies such as physical adsorption, chemical absorption, and catalytic combustion. However, traditional technologies have relatively low VOC removal efficiency. Therefore, there is an urgent need to develop more efficient, cost-effective, and environmentally friendly VOCs elimination technologies.

[0003] Photocatalysis is a green and low-energy-consumption process with broad application prospects. Under low temperature, low pressure, and air conditions, various organic reactions can be achieved through photocatalysis, ultimately converting pollutants into water and carbon dioxide. The principle of photocatalytic oxidation is to use light to excite semiconductors, and the generated electrons, holes, and other reactive oxygen species can participate in oxidation-reduction reactions.

[0004] In recent years, flower-like microsphere semiconductor materials, self-assembled from two-dimensional (2D) nanosheets, have been widely used in photocatalysis, such as photocatalytic N2 fixation, organic synthesis, water splitting, CO2 reduction, and pollutant degradation. Compared with two-dimensional nanosheets, three-dimensional flower-like microsphere materials have a larger specific surface area, providing more active sites for catalytic reactions. Among many metal oxide semiconductor materials that respond to visible light, bismuth molybdate (Bi₂MoO₆) and bismuth tungstate (Bi₂WO₆) belong to the Aurivillius family of layered perovskites, with the general formula Bi₂A₂. n-1 B n O 3n+3Bi₂WO₆ possesses excellent photocatalytic degradation performance. As a visible-light photocatalyst, it can be used for pollutant degradation; however, its high photogenerated carrier recombination rate, wide band gap, and absorption edge of only 460 nm severely limit its visible-light utilization efficiency. In related technologies, Bi₂MoO₆ has been used as a visible-light photocatalyst, with an absorption edge extending to 520 nm. Furthermore, Bi₂MoO₆ has a much smaller band gap than Bi₂WO₆, making it a more ideal photocatalyst from the perspective of visible-light utilization; however, its photocatalytic activity is far lower than that of Bi₂WO₆. Since the ionic radii of W and Mo are extremely similar, W ions can partially replace Mo ions to form a flower-like microsphere solid solution structure with a large specific surface area. This structure can simultaneously retain the advantages of both individual materials, improving both the oxidizing power of Bi₂MoO₆ and the visible-light utilization efficiency of Bi₂WO₆, thus better enhancing the photocatalytic performance of the material.

[0005] Common preparation methods for Bi2W x Mo 1-x Methods for preparing O6 solid solution photocatalysts include hydrothermal methods, solid-phase sintering methods, room temperature precipitation methods, ion exchange methods, and microwave hydrothermal methods. Existing preparation processes are relatively complicated, require high raw material costs, consume a large amount of energy, and the resulting materials have centimeter-sized grains, resulting in large particle sizes and low photocatalytic activity. Summary of the Invention

[0006] This invention provides a bismuth tungsten molybdate solid solution photocatalyst and its preparation method, in order to solve the problems of high energy consumption, long preparation time, complex preparation steps, large material size, and poor photocatalytic activity in existing bismuth tungsten molybdate solid solution photocatalyst preparation methods.

[0007] According to a first aspect of the present invention, the present invention provides a method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, comprising the following steps:

[0008] Bismuth nitrate pentahydrate was dissolved in dilute nitric acid solution and stirred until homogeneous to obtain solution A;

[0009] Sodium tungstate dihydrate and sodium molybdate in different molar ratios were dissolved in water and stirred until homogeneous to obtain solution B;

[0010] The obtained solution B is added to solution A and stirred until homogeneous to obtain solution C;

[0011] Add HTAB to the obtained solution C and stir until homogeneous to obtain solution D;

[0012] The obtained solution D was subjected to a hydrothermal reaction, then cooled to room temperature. The product was then removed, centrifuged, washed, and dried to obtain the bismuth tungsten-molybdate solid solution photocatalyst.

[0013] In the above scheme, the preparation method of the bismuth tungsten-molybdate solid solution photocatalyst of the present invention first prepares a bismuth-containing solution A and a tungsten and molybdenum-containing solution B, then mixes solutions A and B to obtain solution C. Solution C is then modified with HTAB to obtain solution D. The addition of HTAB introduces surface oxygen vacancies into the material. The presence of oxygen vacancies can better promote the separation and migration of photogenerated carriers, thereby improving its photocatalytic activity in degrading gaseous toluene. Then, solution D undergoes a one-step hydrothermal reaction to allow 2D nanosheet raw materials to self-assemble into 3D flower-like microspheres of bismuth tungsten-molybdate solid solution photocatalyst. The preparation method of the present invention only requires a combination of simple room temperature stirring and traditional hydrothermal method. Its reaction time is short, the experimental conditions are mild, and the energy consumption is low. The required raw material cost is low, the morphology of the obtained product is controllable, and the material preparation is easy to realize. Compared with existing preparation methods, the preparation method of the present invention is simple, requiring neither multiple sequential steps nor the synergistic effect of high temperature and co-solvent, greatly reducing the complexity of the steps, energy consumption, and raw material costs. The bismuth tungstenomolybdate solid solution photocatalyst prepared by the method of the present invention has abundant surface oxygen vacancies, which can not only adjust its band structure, improve light absorption performance and increase active sites, but also promote the separation of photogenerated charge carriers, thereby improving its photocatalytic degradation activity of organic pollutants and enhancing the degradation rate and degradation rate of gaseous toluene.

[0014] Furthermore, in solution B, the molar ratio of sodium tungstate dihydrate to sodium molybdate is (1-7):(1-7), preferably 1:(1-7), and more preferably 1:3.

[0015] In the above scheme, by limiting the molar ratio of sodium tungstate dihydrate and sodium molybdate in solution B to a reasonable range, the tungsten to molybdenum ratio in the bismuth tungstate molybdate solid solution photocatalyst can be controlled within a reasonable range. This is more conducive to obtaining bismuth tungstate molybdate solid solution photocatalysts with smaller particle size, uniform distribution, excellent performance, and low cost. When the molar ratio of sodium tungstate dihydrate and sodium molybdate in solution B is too low, the prepared sample is prone to forming stacked nanosheets with larger particle size, thicker layer, and smaller specific surface area. When the molar ratio of sodium tungstate dihydrate and sodium molybdate in solution B is too high, the prepared sample has uneven distribution, poor crystallinity, and obvious agglomeration of nanoparticles.

[0016] Further, in solution C, the molar ratio of bismuth nitrate pentahydrate, sodium tungstate dihydrate, sodium molybdate, and HTAB is 40:(2.5-20):(2.5-20):(0.2-20), preferably 40:(2.5-10):(10-17.5):(2-10), and more preferably 40:5:15:2.74.

[0017] In the above scheme, by controlling the molar ratio of bismuth nitrate pentahydrate, sodium tungstate dihydrate, sodium molybdate, and HTAB in solution C within a reasonable range, it is more conducive to obtaining a bismuth tungstate solid solution photocatalyst with smaller particle size, uniform distribution, excellent performance, and low cost.

[0018] Further, the hydrothermal reaction temperature is 150℃~190℃ and the time is 10-15h; preferably, the hydrothermal reaction temperature is 170℃ and the time is 12h.

[0019] In the above scheme, controlling the temperature and time of the hydrothermal reaction within a reasonable range is beneficial to improving the efficiency of the hydrothermal reaction and is more conducive to obtaining bismuth tungstenomolybdate solid solution photocatalysts with smaller particle size, uniform distribution, and excellent performance.

[0020] Furthermore, the molar concentration of the dilute nitric acid solution is 0.05-0.06 mol / L, preferably 0.057 mol / L.

[0021] In the above scheme, controlling the molar concentration of dilute nitric acid solution within a reasonable range is beneficial to the dissolution of bismuth nitrate.

[0022] Furthermore, the molar concentration of bismuth nitrate pentahydrate in solution A is 0.1-0.15 mol / L, preferably 0.1143 mol / L.

[0023] In the above scheme, limiting the molar concentration of bismuth nitrate pentahydrate in solution A to a reasonable range is more conducive to the dissolution of bismuth nitrate, which in turn is more conducive to subsequent mixing and reaction.

[0024] Furthermore, the stirring conditions for obtaining solutions A, B, C, and D each independently satisfy at least one of the following characteristics (1)-(3):

[0025] (1) The stirring time is 0.5-1.5h, preferably 1h;

[0026] (2) The stirring temperature is room temperature;

[0027] (3) Magnetic stirring is used for stirring.

[0028] In the above scheme, by limiting the time, temperature and method of stirring within a reasonable range, it is beneficial to the dissolution of reactants and to creating a mild and efficient dissolution process.

[0029] Furthermore, the solution D is cooled naturally after the reaction;

[0030] And / or, the solvent used for centrifugal washing of the product is deionized water and / or anhydrous ethanol.

[0031] In the above scheme, natural cooling is used after the reaction of solution D, which is beneficial to maintaining the morphology of the bismuth tungstenomolybdate solid solution photocatalyst during the cooling process. The solvent used for centrifugal washing of the product is deionized water and / or anhydrous ethanol, which avoids the introduction of impurities into the bismuth tungstenomolybdate solid solution photocatalyst, thus preventing any impact on its performance.

[0032] According to a second aspect of the present invention, the present invention also provides a bismuth tungstenomolybdate solid solution photocatalyst, which is prepared by the above-described preparation method.

[0033] Furthermore, the bismuth tungstenomolybdate solid solution photocatalyst has a particle diameter of 50-80 nm and a specific surface area of ​​30-40 m². 2 / g; The bismuth tungsten molybdate solid solution photocatalyst has a degradation rate of over 95% for gaseous toluene within 3 hours.

[0034] The bismuth tungstenomolybdate solid solution photocatalyst of the present invention is a photocatalyst with a wide visible light response range, small size, large specific surface area, low electron-hole recombination rate, and high photogenerated carrier migration efficiency. It has a significant effect on the degradation of volatile organic compounds and can achieve a degradation rate of more than 95% for gaseous toluene within 3 hours.

[0035] The beneficial effects of this invention are as follows:

[0036] (1) The preparation method of the bismuth tungsten molybdate solid solution photocatalyst of the present invention is simple, the reaction conditions are mild and the energy consumption is low. The morphology of the obtained bismuth tungsten molybdate solid solution photocatalyst is controllable, the particle size is small and the specific surface area is large. Under simulated actual environment (temperature: room temperature; light source: visible light), it exhibits excellent photocatalytic performance and excellent cycle performance retention. After four cycles, the crystal structure does not change significantly and the degradation rate can still be maintained above 90%. The bismuth tungsten molybdate solid solution photocatalyst has a wide range of practical application value.

[0037] (2) The bismuth tungstate-molybdate solid solution photocatalyst of this invention is rich in oxygen vacancies, while retaining the strong oxidizing properties of bismuth tungstate and the strong visible light activity of bismuth molybdate. It suppresses electron-hole recombination and improves the migration efficiency of photogenerated carriers. Simultaneously, this catalyst generates a large number of active free radicals such as... 1 O2, ·OH and h + It is a bismuth-based photocatalyst with excellent photocatalytic performance, and has good application prospects and economic value in the photocatalytic degradation of VOCs.

[0038] (3) This invention broadens the visible light response range of bismuth tungstate and the oxidation performance of bismuth molybdate. The photocatalytic activity of bismuth tungstate nanocatalyst in degrading gaseous toluene is 10-12 times that of pure bismuth tungstate and 13-15 times that of pure bismuth molybdate. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 Bi2W prepared in Examples 1-3, 5, 6 and Comparative Examples 1-2 of this invention x Mo 1-x XRD pattern of O6;

[0041] Figure 2 Bi2W prepared in Example 1 of this invention x Mo 1-x SEM images of O6 at different magnifications;

[0042] Figure 3 Bi2W prepared in Example 1 and Comparative Example 3 of this invention x Mo 1-x O6's EPR graph;

[0043] Figure 4 Bi2W prepared in Examples 1-3, 5, 6 and Comparative Examples 1-2 of this invention x Mo 1-x Degradation curve of O6 under visible light for gaseous toluene;

[0044] Figure 5 Bi2W prepared in Examples 1, 4, 7 and Comparative Example 3 of this invention x Mo 1-x Degradation curve of O6 under visible light for gaseous toluene;

[0045] Figure 6 Bi2W prepared in Examples 1 and 8-11 of this invention x Mo 1-x Degradation curve of O6 under visible light for gaseous toluene;

[0046] Figure 7 According to Figure 4 The photodegradation constant diagram obtained from the degradation data;

[0047] Figure 8 Bi2W prepared in Example 1 of this invention x Mo 1-x The degradation curve of O6 in gaseous toluene under visible light in four cycles;

[0048] Figure 9Bi2W prepared in Example 1 of this invention x Mo 1-x XRD patterns of O6 degrading gaseous toluene under visible light before and after four cycles. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0050] Example 1

[0051] This embodiment provides a method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, including the following steps:

[0052] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0053] (2) Dissolve 0.5 mmol sodium tungstate dihydrate and 1.5 mmol sodium molybdate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0054] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0055] (4) Add 0.1g of HTAB to solution C and stir for 1 hour to obtain solution D;

[0056] (5) Transfer solution D to a polytetrafluoroethylene-lined hydrothermal reactor and react at 170℃ for 12 hours. Afterward, cool to room temperature, remove the product, and wash it three times with deionized water and anhydrous ethanol by centrifugation. Dry the product to obtain the sample. The sample has a particle diameter of 50-80 nm and a specific surface area of ​​36.74 m². 2 / g.

[0057] Example 2

[0058] This embodiment provides a method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, including the following steps:

[0059] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0060] (2) Dissolve 0.25 mmol sodium tungstate dihydrate and 1.75 mmol sodium molybdate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0061] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0062] (4) Add 0.1g of HTAB to solution C and stir for 1h to obtain solution D;

[0063] (5) Transfer solution D to a hydrothermal reactor lined with polytetrafluoroethylene and react at 170°C for 12 hours. Then cool to room temperature, take out the product, wash it three times with deionized water and anhydrous ethanol by centrifugation, and dry it to obtain the sample.

[0064] Example 3

[0065] This embodiment provides a method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, including the following steps:

[0066] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0067] (2) Dissolve 1 mmol sodium tungstate dihydrate and 1 mmol sodium molybdate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0068] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0069] (4) Add 0.1g of HTAB to solution C and stir for 1h to obtain solution D;

[0070] (5) Transfer solution D to a hydrothermal reactor lined with polytetrafluoroethylene and react at 170°C for 12 hours. Then cool to room temperature, take out the product, wash it three times with deionized water and anhydrous ethanol by centrifugation, and dry it to obtain the sample.

[0071] Example 4

[0072] This embodiment provides a method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, including the following steps:

[0073] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0074] (2) Dissolve 0.5 mmol sodium tungstate dihydrate and 1.5 mmol sodium molybdate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0075] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0076] (4) Add 0.5g of HTAB to solution C and stir for 1h to obtain solution D;

[0077] (4) Transfer solution D to a hydrothermal reactor lined with polytetrafluoroethylene and react at 170°C for 12 hours. Then cool to room temperature, take out the product, wash it three times with deionized water and anhydrous ethanol by centrifugation, and dry it to obtain the sample.

[0078] Example 5

[0079] The molar ratio of sodium tungstate dihydrate and sodium molybdate dihydrate in step (2) of Example 1 was adjusted to 3:1, and the rest was the same as in Example 1.

[0080] Example 6

[0081] The molar ratio of sodium tungstate dihydrate and sodium molybdate dihydrate in step (2) of Example 1 was adjusted to 7:1, and the rest was the same as in Example 1.

[0082] Example 7

[0083] The amount of HTAB added in step (3) of Example 1 was adjusted to 0.02g, and the rest was the same as in Example 1.

[0084] Example 8

[0085] The temperature in step (5) of Example 3 was adjusted to 150°C, and the rest was the same as in Example 3.

[0086] Example 9

[0087] The temperature in step (5) of Example 3 was adjusted to 160°C, and the rest was the same as in Example 3.

[0088] Example 10

[0089] The temperature in step (5) of Example 3 was adjusted to 180°C, and the rest was the same as in Example 3.

[0090] Example 11

[0091] The temperature in step (5) of Example 3 was adjusted to 190°C, and the rest was the same as in Example 3.

[0092] Comparative Example 1

[0093] A method for preparing a bismuth tungstate solid solution photocatalyst includes the following steps:

[0094] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0095] (2) Dissolve 2 mmol of sodium tungstate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0096] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0097] (4) Add 0.1g of HTAB to solution C and stir for 1h to obtain solution D;

[0098] (4) Transfer solution D to a hydrothermal reactor lined with polytetrafluoroethylene and react at 170°C for 12 hours. Then cool to room temperature, take out the product and wash it three times with deionized water and anhydrous ethanol by centrifugation, and then dry it to obtain the sample.

[0099] Comparative Example 2

[0100] A method for preparing a bismuth molybdate solid solution photocatalyst includes the following steps:

[0101] (1) Dissolve 4 mmol of bismuth nitrate pentahydrate in 35 mL of 0.057 mol / L dilute nitric acid solution and stir for 1 h to obtain solution A;

[0102] (2) Dissolve 2 mmol of sodium molybdate dihydrate in 35 mL of deionized water and stir for 1 h to obtain solution B;

[0103] (3) Add solution B dropwise into solution A, and stir for 1 hour to obtain solution C;

[0104] (4) Add 0.1g of HTAB to solution C and stir for 1h to obtain solution D;

[0105] (4) Transfer solution D to a hydrothermal reactor lined with polytetrafluoroethylene and react at 170°C for 12 hours. Then cool to room temperature, take out the product and wash it three times with deionized water and anhydrous ethanol by centrifugation, and then dry it to obtain the sample.

[0106] Comparative Example 3

[0107] The amount of HTAB added in step (3) of Example 1 was adjusted to 0g, and the rest was the same as in Example 1.

[0108] The catalyst samples prepared in Examples 1-11 and Comparative Examples 1-3 were subjected to gas-phase toluene degradation tests (volatile organic compound degradation performance was tested in a closed test environment and under visible light source conditions to evaluate the photocatalytic performance of the samples in detail). The steps are as follows:

[0109] (1) Distribute 0.2g of photocatalyst evenly on the sample stage, place it in the sealed test chamber and introduce toluene gas with a concentration of 30ppm, and control the gas atmosphere and humidity of the sealed test chamber (0-50%).

[0110] (2) After placing the reactor in the dark for 1 hour, the VOC gas reached adsorption-desorption equilibrium on the surface of the photocatalyst. Then, the catalyst sample was irradiated with a visible light source (420 nm–780 nm). The concentration of VOC in the sealed environment was monitored every 30 minutes to evaluate the photocatalytic degradation performance of the catalyst for VOCs. The test results are shown in Table 1 and... Figures 4-6 As shown.

[0111] Table 1 Comparison of purification effects of Examples 1-11 and Comparative Examples 1-3

[0112]

[0113] As can be seen from the experimental results in Table 1, the bismuth tungsten molybdate solid solution photocatalyst of Example 1 has the highest activity in degrading gaseous toluene under visible light irradiation. For 30 ppm of gaseous toluene, the degradation rate can reach as high as 96.80% within 180 min.

[0114] Figure 1 These are XRD patterns of Examples 1-6 and Comparative Examples 1-2, using different proportions of raw materials. Figure 1 The successful preparation of bismuth tungstate, bismuth molybdate, and bismuth tungstate-molybdate solid solution materials with different proportions can be seen.

[0115] Figure 2 This is a SEM image of the bismuth tungsticolaminate solid solution photocatalyst prepared in Example 1. Figure 2 As can be seen from the above, the bismuth tungsten molybdate solid solution photocatalyst of the present invention has small particle size and uniform distribution, and is composed of numerous 2D nanosheets self-assembled into a 3D flower-like microsphere structure. This structure has a large specific surface area, which can provide more active sites for catalytic reaction, thereby improving its photocatalytic degradation activity of gaseous toluene.

[0116] Figure 3 These are the EPR diagrams of the bismuth tungsticolate solid solution photocatalysts prepared in Example 1 and Comparative Example 3. (S1 is Example 1; S2 is Comparative Example 3) Figure 3 As can be seen from the above, the bismuth tungstenomolybdate solid solution photocatalyst of the present invention introduces surface oxygen vacancies into the material through HTAB modification. The presence of oxygen vacancies can better promote the separation and migration of photogenerated charge carriers, thereby improving its photocatalytic degradation activity of gaseous toluene.

[0117] Figures 4-6These are degradation curves of gaseous toluene under visible light irradiation for the bismuth tungsticolate solid solution photocatalysts prepared in Examples 1-11 and Comparative Examples 1-3. The comparison shows that the bismuth tungsticolate solid solution photocatalyst prepared in Example 1, with a preparation temperature of 170℃, a W / Mo molar ratio of 1 / 3, and an HTAB addition of 0.1g, exhibits the highest activity in degrading gaseous toluene under visible light irradiation. For 30ppm of gaseous toluene, a degradation rate of up to 96.80% can be achieved within 180 minutes.

[0118] Figure 7 According to Figure 4 The degradation data were used to establish a quasi-first-order kinetic model and calculate the photodegradation constants. Figure 7 As can be seen from the data, the photodegradation constant of the catalyst is significantly improved after the formation of the bismuth tungomolybdate solid solution. (Bi₂W) 0.25 Mo 0.75 The K value of O6 is 0.0161 min. -1 They are pure Bi2WO6 (0.00156 min) -1 10.32 times that of pure Bi₂MoO₆ (0.00117 min) -1 The concentration of Bi2W in the sample was 13.7 times that of Bi2W. 0.25 Mo 0.75 O6 exhibits excellent photocatalytic activity.

[0119] Figures 8-9 This shows the cyclic degradation curves of gaseous toluene by the bismuth tungstenomolybdate solid solution photocatalyst of Example 1 under visible light irradiation, and the XRD patterns before and after four cycles. Figure 8 As can be seen, the bismuth tungstenomolybdate solid solution photocatalyst of the present invention exhibits excellent cycling stability. After four cycles of photocatalytic reaction totaling 12 hours, it still maintains a degradation performance of over 90% for gaseous toluene, demonstrating broad practical application prospects. Figure 9 As can be seen from the XRD patterns, the bismuth tungsten molybdate solid solution photocatalyst of the present invention showed no significant difference before and after four cycles, indicating that it has a stable crystal structure and excellent cycle stability.

[0120] In summary, the preparation method of this invention is simple and does not require a large amount of energy consumption. It only requires one-step hydrothermal synthesis under physical stirring at room temperature. The prepared bismuth tungsten-molybdate solid solution photocatalyst has a controllable crystal structure, a large specific surface area, and abundant surface oxygen vacancies, which increases the active sites for photocatalytic reaction and is beneficial to the separation and migration of photogenerated carriers. This improves the photocatalytic degradation activity of gaseous toluene, and can achieve a degradation rate of over 95% for 30 ppm gaseous toluene within 180 min. At the same time, it also has excellent cycle stability, and can still maintain a high degradation rate of over 90% after four cycles.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a bismuth tungstenomolybdate solid solution photocatalyst, characterized in that, Includes the following steps: Bismuth nitrate pentahydrate was dissolved in dilute nitric acid solution and stirred until homogeneous to obtain solution A; Sodium tungstate dihydrate and sodium molybdate in a molar ratio of 1:3 were dissolved in water and stirred until homogeneous to obtain solution B; The obtained solution B is added to solution A and stirred until homogeneous to obtain solution C; Add HTAB to the obtained solution C and stir until homogeneous to obtain solution D; The obtained solution D was subjected to a hydrothermal reaction, then cooled to room temperature, and the product was taken out, centrifuged, washed, and dried to obtain the bismuth tungsten-molybdate solid solution photocatalyst; the hydrothermal reaction was carried out at a temperature of 170°C for 12 hours. In solution C, the molar ratio of bismuth nitrate pentahydrate, sodium tungstate dihydrate, sodium molybdate, and HTAB is 40:5:15:2.

74.

2. The preparation method according to claim 1, characterized in that, The molar concentration of the dilute nitric acid solution is 0.05-0.06 mol / L.

3. The preparation method according to claim 2, characterized in that, The molar concentration of the dilute nitric acid solution is 0.057 mol / L.

4. The preparation method according to claim 1, characterized in that, The molar concentration of bismuth nitrate pentahydrate in solution A is 0.1-0.15 mol / L.

5. The preparation method according to claim 4, characterized in that, The molar concentration of bismuth nitrate pentahydrate in solution A is 0.1143 mol / L.

6. The preparation method according to claim 1, characterized in that, The stirring conditions for obtaining solutions A, B, C, and D each independently satisfy at least one of the following characteristics (1)-(3): (1) The stirring time is 0.5-1.5h; (2) The stirring temperature is room temperature; (3) Magnetic stirring is used for stirring.

7. The preparation method according to claim 6, characterized in that, The stirring time is 1 hour.

8. The preparation method according to claim 1, characterized in that, Solution D was cooled naturally after the reaction. And / or, the solvent used for centrifugal washing of the product is deionized water and / or anhydrous ethanol.

9. A bismuth tungsticolate solid solution photocatalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The bismuth tungstenomolybdate solid solution photocatalyst according to claim 9, characterized in that, The bismuth tungsten molybdate solid solution photocatalyst has a particle diameter of 50-80 nm and a specific surface area of ​​30-40 m². 2 / g; the bismuth tungsten molybdate solid solution photocatalyst has a degradation rate of over 95% for gaseous toluene within 3 hours.

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