Preparation method and application of photo-thermal synergistic catalytic nanomaterial ag / f-sn02 for efficiently degrading vocs, especially formaldehyde

Abstract

The application provides a preparation method and application of a photo-thermal synergistic catalysis nanomaterial Ag / F-SnO2 which can degrade VOCs, especially formaldehyde, and relates to the technical field of photocatalysis, and the preparation method comprises the following steps: in step 1, tin-containing solution, sodium hydroxide solution and NH4F solution are uniformly mixed and then subjected to hydrothermal reaction, the obtained product is subjected to centrifugation, washing, drying and grinding to obtain SnO2 doped with F; in step 2, AgNO3 solution and NaBH4 aqueous solution are added to the F-SnO2 suspension, and then the mixture is subjected to stirring, separation by standing, washing, drying and grinding, so that silver is loaded on the SnO2 doped with F to obtain the nanomaterial Ag / F-SnO2. The Ag NP, F and SnO2 are compounded to obtain a composite catalyst with photo-thermal synergistic catalysis capacity, the catalyst can efficiently degrade VOCs in indoor air, especially toluene, has good stability and reusability, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photocatalysis, in particular to a preparation method and application of a light-heat synergistic catalytic nanomaterial Ag / F-SnO2 for efficiently degrading VOCs, especially formaldehyde. BACKGROUND

[0002] Due to the use of a large amount of adhesive in home decoration materials, volatile organic compounds (VOCs), nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter and other air pollutants are contained in indoor air. And because most people spend most of their time in indoor environments, if people are exposed to indoor air pollutants for a long time, it will be harmful to health and may lead to sick building syndrome, building-related illness, and in extreme cases, cancer. The Indoor Air Quality Standard (GB / T 18883-2022) lists 22 items including toluene (high performance liquid chromatography), benzene, toluene, xylene, total volatile organic compounds (TVOC) as air quality detection indicators.

[0003] Volatile organic compounds (VOCs) mainly include alkanes, aromatic hydrocarbons, esters, alkenes, carboxylic acids and alcohols. The existing technology for removing volatile organic compounds VOCs includes photocatalytic oxidation, adsorption, absorption, biological filtration, membrane filtration, incineration and combustion, etc. Adsorption technology improves the adsorption capacity of VOCs by improving the specific surface area, pore volume, surface chemical functional groups of the adsorbent and reducing the pore size, and the adsorbent and VOCs can be recycled and reused; biological filtration technology is used to remove VOCs at low to moderate concentrations (<1000 mg / L), but the filter bed needs to be backwashed regularly; membrane filtration technology is usually used to separate halogenated VOCs (such as chloroform, trichloroethylene, tetrachloroethylene, etc.) and avoid the generation of by-products. Compared with the above technologies, photocatalytic oxidation process is considered as an efficient and economical advanced oxidation technology for VOCs removal. Photocatalytic oxidation method is driven by photocatalyst absorption of sunlight, which has the advantages of mild reaction conditions, green, energy saving, good degradation efficiency of multiple pollutants, etc.

[0004] However, in the practical application process of photocatalytic oxidation, it is found that most of the existing photocatalysts have the defects of wide band gap, limited range of light absorption wavelength, and mismatched energy band position, resulting in poor photocatalytic degradation efficiency. Because photocatalysis is affected by light conditions in the actual application environment, the catalytic effect of the catalyst is unstable. Therefore, in the field of photocatalysis, how to effectively improve the catalytic performance of the photocatalyst is a technical problem to be solved at present. SUMMARY

[0005] To solve the above problems, in a first aspect, the present application provides a preparation method of a light-heat synergistic catalytic nanomaterial Ag / F-SnO2, which comprises:

[0006] Step 1: mixing tin-containing solution, sodium hydroxide solution and NH4F solution uniformly, then carrying out hydrothermal reaction, and obtaining F-doped SnO2 by centrifugation, washing, drying, and grinding after the reaction; wherein the molar ratio of the tin-containing solution, the sodium hydroxide solution and the NH4F solution is 1:(1-8):(1-5);

[0007] Step 2: adding AgNO3 solution and NaBH4 aqueous solution to the F-SnO2 suspension, and obtaining the nanomaterial Ag / F-SnO2 by stirring, standing, separating, washing, drying, and grinding; wherein the mass fraction ratio of the F-SnO2 suspension and the AgNO3 solution is 1:(0.016-0.096).

[0008] Preferably, in the step 1, the temperature of the hydrothermal reaction is 120-180℃, and the holding time of the hydrothermal reaction is 24-48h.

[0009] Preferably, in the step 1, the molar ratio of the tin-containing solution, the sodium hydroxide solution and the NH4F solution is 1:5:2; wherein the NH4F solution is obtained by adding NH4F dropwise into ethanol solution.

[0010] Preferably, in the step 1, the mass fraction ratio of the F-SnO2 suspension and the AgNO3 solution is 1:0.048.

[0011] Preferably, in the step 1, the tin-containing solution is obtained by dissolving anhydrous tin chloride, tin chloride dihydrate or tin chloride pentahydrate in deionized water.

[0012] Preferably, in the step 1, the mixing is realized by stirring, and the stirring time is 20-30min; the washing is carried out by using ultrapure water and anhydrous ethanol; and the drying temperature is 60-80℃.

[0013] Preferably, in the step 2, the F-SnO2 suspension is obtained by dispersing the F-doped SnO2 in step 1 in deionized water; the stirring time is 4-8h, the washing is carried out by using alcohol and deionized water, and the drying temperature is 120℃.

[0014] Preferably, in the step 2, the molar ratio of the NaBH4 aqueous solution and the AgNO3 solution is 4:1.

[0015] Preferably, the loading amount of Ag nanoparticles in the nanomaterial Ag / F-SnO2 is 3wt%.

[0016] In a second aspect, the application provides an application of the photo-thermal synergistic catalytic nanomaterial Ag / F-SnO2, wherein the nanomaterial Ag / F-SnO2 obtained by the preparation method of the first aspect is used for degrading VOCs, especially formaldehyde.

[0017] Compared with the prior art, the application has the following advantages:

[0018] The application provides a preparation method and application of a photo-thermal synergistic catalytic nanomaterial Ag / F-SnO2 for efficiently degrading VOCs, especially formaldehyde, and relates to the technical field of photocatalysis. The preparation method comprises the following steps: in step 1, tin-containing solution, sodium hydroxide solution and NH4F solution are uniformly mixed and then subjected to hydrothermal reaction, and the obtained product is subjected to centrifugation, washing, drying and grinding to obtain F-doped SnO2; in step 2, AgNO3 solution and NaBH4 aqueous solution are added to the F-SnO2 suspension, and then the mixture is subjected to stirring, separation by standing, washing, drying and grinding to load silver on the F-doped SnO2 to obtain the nanomaterial Ag / F-SnO2. The application composites Ag NP, F and SnO2 to obtain a composite catalyst with photo-thermal synergistic catalytic capacity. The catalyst can efficiently degrade VOCs in indoor air, especially has the optimal degradation effect on toluene, and has good stability, reusability and good application prospect.

[0019] In the embodiment of the application, the deposition of the metal co-catalyst and the element doping change the band gap, the energy band edge and the carrier separation capacity of the composite catalyst, thereby improving the photocatalytic degradation efficiency. That is, the SnO2 is modified by Ag NP deposition modification and F doping. The Ag NP and F jointly modify the SnO2, which can improve the light absorption capacity of the SnO2, thereby improving the photocatalytic capacity activity of the SnO2 and improving the toluene removal efficiency to a certain extent. Meanwhile, the movement of the photo-generated electrons to the Ag nanoparticles is enhanced, and the photo-generated carrier separation performance is simultaneously improved with the defects introduced by the fluorine doping, thereby reducing the recombination of the carriers and finally improving the ability of photocatalytic oxidation of toluene. The Ag NP, F and SnO2 are composited to obtain a composite catalyst with photo-thermal synergistic catalytic capacity. The composite catalyst has the synergistic effect between the photocatalytic and thermal catalytic effects, so that under the condition of photo-thermal synergistic catalysis, the composite catalyst can efficiently degrade VOCs in indoor air, especially has the optimal degradation effect on toluene, and has the characteristics of good stability and reusability. The composite catalyst not only improves the photocatalytic performance of the catalyst, but also supplements the thermal catalytic property, so that the catalytic effect of the catalyst is stable, thereby solving the problems of poor photocatalytic degradation efficiency and unstable photocatalytic effect. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 The flow chart of the preparation method of the photo-thermal synergistic catalytic nanomaterial Ag / F-SnO2 provided by the present application is shown in the figure.

[0022] Figure 2 The scanning electron microscope image of the Ag / F-SnO2 prepared in the embodiment 1 of the present application is shown in the figure.

[0023] Figure 3 The ultraviolet-visible diffuse reflectance spectrogram of the SnO2, F-SnO2 and Ag / F-SnO2 composite visible light catalytic nanomaterial prepared in the embodiment of the present application is shown in the figure.

[0024] Figure 4 The Fourier transform infrared absorption spectrogram of the F-SnO2 and Ag / F-SnO2 materials prepared in the embodiment of the present application is shown in the figure.

[0025] Figure 5 The comparison graph of the degradation time curves of the 3wt% Ag NP modified Ag / F-SnO2 photocatalytic nanomaterial prepared in the embodiment of the present application, F-SnO2 and single SnO2 photocatalytic degradation of toluene is shown in the figure.

[0026] Figure 6 The continuous degradation experiment result graph of the Ag / F-SnO2 photocatalytic nanomaterial obtained in the embodiment 1 of the present application is shown in the figure.

[0027] Figure 7 The result graph of the removal rate of toluene by the Ag / F-SnO2 obtained in the embodiment 1 of the present application at different temperatures is shown in the figure. DETAILED DESCRIPTION

[0028] The following embodiments are provided in order to better further understand the present application, and are not limited to the best embodiments, and do not constitute a limitation on the content and protection scope of the present application, and any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application.

[0029] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0030] Due to the extensive use of adhesives in home decoration materials, indoor air contains air pollutants such as volatile organic compounds (VOCs), nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter. Specific air pollutants include toluene, SO2, and ammonia. VOCs mainly include alkanes, aromatics, esters, alkenes, carboxylic acids, and alcohols, such as toluene. Existing technologies for removing VOCs include photocatalytic oxidation, adsorption, absorption, biofiltration, membrane filtration, incineration, and combustion. Among these, photocatalytic oxidation is considered a highly efficient and economical advanced oxidation technology for VOC removal. Driven by the absorption of sunlight through a photocatalyst, photocatalytic oxidation offers advantages such as mild reaction conditions, being green, energy-saving, and having high degradation efficiency for multiple pollutants.

[0031] However, in practical applications of photocatalytic oxidation, it has been found that most existing photocatalysts have drawbacks such as wide band gaps, limited light absorption wavelength ranges, and band structure mismatches, resulting in poor photocatalytic degradation efficiency. Furthermore, photocatalysis is subject to the influence of light conditions in practical applications, leading to unstable catalytic performance. Therefore, effectively improving the catalytic performance of photocatalysts has become an urgent technical problem to be solved in the field of photocatalysis.

[0032] In view of this, the present invention improves the photocatalytic degradation efficiency by changing the band gap, band edge, and carrier separation capability of the composite catalyst through element doping and the deposition of metal co-catalysts, thereby obtaining a composite nanocatalytic material with both photocatalytic and thermocatalytic properties.

[0033] Firstly, referring to Figure 1 , Figure 1 This is a flowchart of a method for preparing the photothermal synergistic catalytic nanomaterial Ag / F-SnO2 provided by the present invention. The preparation method includes:

[0034] S101, hydrothermal reaction is carried out after the tin-containing solution, the sodium hydroxide solution and the NH4F solution are mixed uniformly, and the obtained product is obtained after centrifugation, washing, drying and grinding to obtain SnO2 doped with F; wherein the molar ratio of the tin-containing solution, the sodium hydroxide solution and the NH4F solution is 1: (1-8): (1-5);

[0035] In specific implementation, tin hydroxide is generated under alkaline conditions; then, SnO2 is generated by dehydration under high-temperature hydrothermal conditions, and F ions are doped into the process of SnO2 precipitation to obtain F-SnO2: a certain molar ratio of tin source and NaOH is dissolved in deionized water respectively, and each is mixed and stirred for 20 min to obtain a tin-containing solution and a sodium hydroxide solution; wherein the amount of deionized water is not specifically limited, for example, 50 mL of deionized water is used respectively. Then, a proper amount of NH4F is added to 75% ethanol, mixed and stirred for 30 min to obtain an NH4F solution; wherein the addition amount of NH4F is 10 mmol-30 mmol, and the amount of ethanol is 30-100 mL. The above hydrothermal reaction is carried out in a stainless steel high-pressure reaction kettle with a Teflon lining.

[0036] S102, AgNO3 solution and NaBH4 aqueous solution are added to the F-SnO2 suspension, and after stirring, standing, separation, washing, drying and grinding, the nanomaterial Ag / F-SnO2 is obtained; wherein the mass fraction ratio of the F-SnO2 suspension and the AgNO3 solution is 1: (0.016-0.096).

[0037] In specific implementation, Ag NP (Ag nanoparticle) is loaded on F-SnO2 by reduction-deposition method, that is, Ag NP is deposited on the surface of F-SnO2: a certain amount of F-SnO2 is dispersed in 30 mL of deionized water to obtain a F-SnO2 suspension, and AgNO3 solution is added dropwise to the F-SnO2 suspension under vigorous stirring; after the silver nitrate and the F-SnO2 dispersion are uniformly mixed, NaBH4 aqueous solution (as a reducing agent) is added to the F-SnO2 suspension (turbidity), and stirring, standing and separation are continued, then the sample is separated, and the separated material is washed with alcohol and deionized water, and then dried and ground to obtain Ag / F-SnO2. It should be noted that Ag is not introduced into SnO2 as a dopant to modify SnO2.

[0038] In the embodiment of the present application, the band gap, the band edge and the carrier separation ability of the composite catalyst are changed by the deposition of the metal co-catalyst and the element doping, so as to improve the photocatalytic degradation efficiency, that is, the SnO2 is modified by the deposition modification of Ag NP and the F doping, the composite catalyst with the synergistic photocatalytic and thermal catalytic ability is obtained by the compounding of Ag NP, F and SnO2, the composite catalyst has the photocatalytic performance and the thermal catalytic performance, the photocatalytic performance of the visible light catalyst is improved, and the thermal catalytic performance is supplemented, so that the catalytic effect of the catalyst is stable, and the problems of the poor photocatalytic degradation efficiency and the unstable photocatalytic effect are solved. On the one hand, the F doping is performed in the process of synthesizing SnO2, the surface oxygen vacancy and the change of the local electronic structure are introduced, the photo-generated carrier separation performance is improved, the recombination of the carriers is reduced, and the SnO2 photocatalytic activity is improved, so as to improve the ability of photocatalytic oxidation and degradation of toluene; the Ag NP is loaded (deposited) on the surface of the semiconductor material SnO2, the Ag NP can endow the SnO2 with the thermal catalytic activity and the superior electron capture ability, the noble metal Ag nanoparticles with the thermal catalytic activity and the SPR effect (SPR) are compounded with the semiconductor material SnO2 with the photocatalytic activity, the photocatalysis and the thermal catalysis are coupled to produce the synergistic effect of the photo-thermal catalysis, so that the semiconductor material SnO2 has the synergistic photocatalytic and thermal catalytic ability, and the toluene oxidation and degradation performance of the composite material is further improved. On the other hand, the Ag NP and the F jointly modify the SnO2, the light absorption ability of the SnO2 is improved, so as to improve the photocatalytic ability of the SnO2, and the toluene removal efficiency is improved to a certain extent; meanwhile, the movement of the photo-generated electrons to the Ag nanoparticles is enhanced, and the photo-generated carrier separation performance is improved synchronously with the defects introduced by the fluorine doping, so as to reduce the recombination of the carriers, and finally improve the ability of photocatalytic oxidation of toluene. Specifically, the Ag NP and the F jointly modify the SnO2, the electron capture ability of the SnO2 is improved, so as to improve the separation ability of the generated carriers of the Ag / F-SnO2 material under the light excitation, reduce the recombination of the carriers, and then when a large amount of carriers are transferred to the surface of the Ag / F-SnO2 material, the to-be-degraded substances or free radical precursors adsorbed on the surface of the Ag / F-SnO2 material react with a large amount of photo-generated carriers to generate more free radicals, the catalytic activity is improved, and the next step of degradation reaction is performed by the free radicals, and finally the ability of photocatalytic oxidation of toluene is improved.

[0039] The Ag / F-SnO2 material provided by the application can efficiently degrade VOCs (an air pollutant) in indoor air under the condition of photo-thermal synergistic catalysis, and has the characteristics of good stability and reusability, so the catalyst will have a good application prospect in the field of indoor VOCs purification. The Ag / F-SnO2 material has a very good degradation efficiency on air pollutants, and has the optimal degradation effect on toluene in particular. It should be noted that toluene is a kind of air pollutant which is difficult to degrade, and the ability to degrade toluene also has a corresponding degradation effect on other easily treated substances. In addition, the novel visible light catalyst provided by the application also solves the problem of single ability of photocatalysis or thermal catalysis, reduces energy consumption by introducing photocatalysis, and stabilizes the catalytic effect of the catalyst by supplementing thermal catalysis. It should be noted that single photocatalytic material generally does not have thermal catalytic performance. In the prior art, thermal catalysis generally needs to be heated, so thermal catalysis needs additional energy supply, and the energy consumption is large. Although photocatalysis can utilize sunlight and is more environmentally friendly, it needs water as a medium, and photocatalysis in the actual application environment will be affected by the light conditions.

[0040] It should be noted that the noble metal Ag nanoparticles with thermal catalytic activity and metal plasmon resonance effect (SPR) are loaded on the semiconductor material SnO2, the Ag nanoparticles not only improve the photocatalytic performance, but also play a role in thermal catalysis. The improvement of the photocatalytic performance is as follows: a Schottky barrier can be formed to promote the separation of photo-generated electron-hole pairs, reduce the recombination of carriers, improve the SnO2 photocatalytic activity, and thus improve the ability of photocatalytic degradation of toluene; and due to the existence of the metal plasmon resonance effect (SPR), the absorption of light by the semiconductor material is improved, and the light absorption range is widened, so that the degradation rate can be improved to a certain extent (that is, when the incident photon frequency matches the overall vibration frequency of the noble metal Ag nanoparticles or metal conduction electrons, the Ag nanoparticles will have a strong absorption effect on the photon energy, and local surface plasmon resonance will occur). In the process of degrading toluene, the Ag / F-SnO2 material improves the degradation rate from two aspects through the Ag nanoparticles deposited on the surface of the material, and plays the following roles in photocatalysis: widening the light absorption range to a certain extent to improve the degradation rate (specifically, the light absorption range is widened by the plasmon resonance effect of the Ag nanoparticles); and endowing SnO2 with superior electron capture ability, so that the movement of photo-generated electrons to the Ag nanoparticles deposited on the surface of the material is enhanced, the separation ability of the Ag / F-SnO2 material to generate carriers under light excitation is improved, the recombination of carriers is reduced, and then when a large number of carriers are transferred to the surface of the Ag / F-SnO2 material, the degradation substances or free radical precursors adsorbed on the surface of the Ag / F-SnO2 material react with a large number of photo-generated carriers to generate more free radicals, thereby improving the catalytic activity, and the next step of degradation reaction is carried out by the free radicals, and finally the effect of the photocatalytic degradation reaction is improved; and a certain role is played in thermal catalysis, and the catalytic performance of the Ag / F-SnO2 material itself is utilized to degrade toluene.

[0041] It should be noted that the light-thermal catalytic synergistic effect is generated after coupling, and the light-thermal synergistic degradation rate will be higher than the single photocatalytic rate, the single thermal catalytic rate, or the sum of the two, that is, the synergistic effect between photocatalysis and thermal catalysis in the present application is the synergistic effect of the two catalytic forms; and the Ag nanoparticles not only have the SPR effect in the photocatalytic effect, but also play a role in the thermal catalysis.

[0042] Preferably, in the step 1, the temperature of the hydrothermal reaction is 120-180℃, and the holding time of the hydrothermal reaction is 24-48h.

[0043] In specific implementation, the temperature of the hydrothermal reaction is preferably in the range of 130-180℃, and the holding time is preferably 24h; further, the hydrothermal temperature is 140℃.

[0044] Preferably, in the step 1, the molar ratio of the tin-containing solution, the sodium hydroxide solution and the NH4F solution is 1:5:2; wherein the NH4F solution is obtained by adding NH4F into ethanol solution.

[0045] Preferably, in the step 1, the mass fraction ratio of the F-SnO2 suspension and the AgNO3 solution is 1:0.048.

[0046] Preferably, in the step 1, the tin-containing solution is obtained by dissolving anhydrous tin chloride, tin chloride dihydrate or tin chloride pentahydrate in deionized water.

[0047] Preferably, in the step 1, the mixing is achieved by stirring for 20min-30min; the washing is performed by using ultrapure water and anhydrous ethanol; and the drying temperature is 60℃-80℃.

[0048] In particular implementation, the stirring time is preferably 20min; the product collected by centrifugation is repeatedly washed by using ultrapure water and anhydrous ethanol; and the drying time is preferably 60℃.

[0049] Preferably, in the step 2, the F-SnO2 suspension is obtained by dispersing the F-doped SnO2 in the step 1 in deionized water; the stirring time is 4h-8h; the washing is performed by using alcohol and deionized water; and the drying temperature is 120℃.

[0050] In particular implementation, the stirring time is preferably 4h, and the drying time can be 24h; since the F-SnO2 is insoluble in water, the F-SnO2 is dispersed in deionized water to form a suspension (float).

[0051] Preferably, in the step 2, the molar ratio of the NaBH4 aqueous solution and the AgNO3 solution is 4:1.

[0052] Preferably, the loading amount of Ag nanoparticles in the nanomaterial Ag / F-SnO2 is 3wt%.

[0053] In a second aspect, the application provides an application of the photo-thermal synergistic catalytic nanomaterial Ag / F-SnO2, wherein the nanomaterial Ag / F-SnO2 obtained by the preparation method of the first aspect is used for degrading VOCs, especially formaldehyde.

[0054] In the embodiment of the present application, the obtained Ag / F-SnO2 material has good degradation efficiency on VOCs (an air pollutant), and has optimal degradation effect on toluene. The catalyst solves the problem of single ability of photocatalysis or thermal catalysis, reduces energy consumption by introducing photocatalysis, and makes the catalytic effect of the catalyst more stable by supplementing thermal catalysis. It should be noted that toluene is a kind of air pollutant which is difficult to degrade, and the degradation of toluene can also correspondingly have a degradation effect on other easily treated substances.

[0055] In the degradation process, the Ag / F-SnO2 material is doped with F, which introduces surface oxygen vacancies and changes the local electronic structure, improves the separation performance of photo-generated carriers, reduces the recombination of carriers, and thus improves the ability of photocatalytic degradation of toluene; in the degradation process, the band gap of the single photocatalytic material SnO2 is 3.6 eV, which has strong redox ability to degrade toluene; in the process of degrading toluene, the Ag / F-SnO2 material improves the degradation rate from two aspects through the Ag nanoparticles deposited on the surface of the material, which plays the following roles in photocatalysis: broadening the light absorption range, which can improve the degradation rate to a certain extent (specifically, the light absorption range is broadened by the plasmonic resonance effect of Ag nanoparticles); at the same time, it endows SnO2 with superior electron capture ability, which enhances the movement of photo-generated electrons to the Ag nanoparticles deposited on the surface of the material, improves the separation ability of the generated carriers of the Ag / F-SnO2 material under light excitation, reduces the recombination of carriers, and then when a large number of carriers are transferred to the surface of the Ag / F-SnO2 material, the degradation or free radical precursor adsorbed on the surface of the Ag / F-SnO2 material reacts with a large number of photo-generated carriers to generate more free radicals, which improves the catalytic activity, and then the free radicals perform the next step of degradation reaction, and finally the effect of photocatalytic degradation reaction is improved; in thermal catalysis, it plays a certain role and degrades toluene by using its own catalytic performance.

[0056] In order for those skilled in the art to better understand the present application, the following describes the preparation method provided by the present application through a plurality of specific embodiments.

[0057] Example 1

[0058] In this embodiment, the molar ratio of the raw materials is: the molar ratio of tin chloride, sodium hydroxide and NH4F is 1:5:2.

[0059] Step 1: 10 mmol of tin chloride and 50 mmol of sodium hydroxide were dissolved in 50 mL of deionized water respectively, and stirred for 20 min. 20 mmol of NH4F was dissolved in 50 mL of 75% ethanol, and stirred for 10 min (i.e. the molar ratio of the tin-containing solution, the sodium hydroxide solution and the NH4F solution was 1:5:2). The three solutions were mixed and stirred for 20 min, and the resulting mixture was poured into a Teflon-lined stainless steel autoclave, which was incubated at 140°C for 24 h. The product was collected by centrifugation and repeatedly washed with ultrapure water and anhydrous ethanol. Finally, the product was dried at 60°C and ground to obtain F-SnO2.

[0060] Step 2: Ag NPs were loaded onto F-SnO2 using a reduction-deposition method. 0.5 g of F-SnO2 was dispersed in 30 mL of deionized water. AgNO3 solution was added dropwise under vigorous stirring (i.e. the mass fraction ratio of the F-SnO2 suspension and the AgNO3 solution was 1:0.048) to obtain a 3 wt% Ag loading. With NaBH4 aqueous solution as the reducing agent, the silver nitrate and F-SnO2 dispersion were mixed uniformly, and then the NaBH4 aqueous solution was added to the F-SnO2 suspension at a molar ratio of NaBH4 / Ag = 4. The stirring was continued for 4 h, and then the sample was separated after standing and layering. The separated material was washed with alcohol and deionized water, and then dried at 120°C overnight. The Ag / F-SnO2 was obtained by grinding.

[0061] The obtained Ag / F-SnO2 was subjected to characterization tests, and the results are shown in Table 1. Figure 2 , Figure 2 The scanning electron microscope image of the Ag / F-SnO2 prepared in Example 1 of the present application is shown in the figure, and the Ag / F-SnO2 material has a mesoporous nanosheet structure, and the sheet structures are stacked with each other.

[0062] Comparative Example 1

[0063] 10 mmol of tin chloride and 50 mmol of sodium hydroxide were dissolved in 50 mL of deionized water respectively, and stirred for 20 min before being poured into a Teflon-lined stainless steel autoclave, which was incubated at 140°C for 24 h. The product was collected by centrifugation and repeatedly washed with ultrapure water and anhydrous ethanol. Finally, the product was dried at 60°C and ground to obtain SnO2.

[0064] The Ag / F-SnO2 obtained in Example 1, the SnO2 obtained in Comparative Example 1, and the F-SnO2 obtained in Step 1 of Example 1 were subjected to the following performance tests. The results are shown in Table 1. Figure 3 , Figure 3UV-Vis diffuse reflectance spectra of SnO2, F-SnO2 and Ag / F-SnO2 composite visible light catalytic nanomaterials prepared in the embodiments of the present application. As shown in the figure, single SnO2 has strong light absorption between 200-400 nm in the near ultraviolet region, and after F doping, the light absorption range of F-SnO2 changes little compared with single SnO2 material, but the light absorption intensity is improved. The Ag / F-SnO2 composite material enhances the visible light absorption of the material in the 400-600 nm region due to the existence of Ag plasmonic resonance effect.

[0065] In order to study the composition and structure of the sample after synthesis, FTIR analysis was used, and the reference Figure 4 , Figure 4 Fourier transform infrared absorption spectra of F-SnO2 and Ag / F-SnO2 materials prepared in the embodiments of the present application. As shown in the figure, the strong and wide peaks at 3431 cm -1 and 1622 cm -1 are respectively attributed to the stretching vibration of the hydroxyl group on the surface of the material and the bending vibration of the water molecule. The wide peak band at 619 cm -1 corresponds to the superposition of the anti-symmetric O-Sn-O stretching mode and the terminal oxygen vibration in the SnO2 nanostructure. It is shown that the Ag NP modification and F doping do not significantly change the absorption of the spectrum of SnO2, i.e. there is no too much change in its bond connection.

[0066] In order to verify the degradation performance of the Ag / F-SnO2 photocatalytic nanomaterial prepared in Example 1 on toluene, the following experiment was done:

[0067] First, the photo-thermal catalytic activity was evaluated:

[0068] The catalytic reaction was carried out in a 100 mL stainless steel reactor, the reactor was placed in a heating unit, and a 300 W Xe lamp was equipped. By passing a gas mixture (N2:O2=3:1) into the toluene saturated solution, the toluene concentration in the gas flow was adjusted to 100 ppm, and it was injected into the reactor. Start the light source and heating unit, take out 2 mL of gas every certain time, and measure the toluene content using a gas chromatograph equipped with a flame ionization detector (FID). The removal rate (Y) of toluene is calculated as Y(%)=(1-C / C0)×100%, where C and C0are the concentrations of toluene at 0 and t min, respectively. Referring to Figure 5 , Figure 5The 3wt% Ag NP modified Ag / F-SnO2 photocatalytic nanomaterial prepared in the embodiment of the present application is compared with F-SnO2 and single SnO2 photocatalytic degradation of toluene time degradation curve. As can be seen from the figure, the degradation rates of F-SnO2 and single SnO2 to toluene are 33% and 42% respectively within 80 min; while the removal (degradation) efficiency of Ag / F-SnO2 to toluene is as high as 85.6% within the same time.

[0069] A continuous degradation experiment is carried out:

[0070] After the first degradation reaction is completed, the reactor containing the photocatalyst is dried at 60°C for 2 hours, and then cooled to room temperature before being put into the reactor again for the next toluene removal reaction, and the remaining reaction conditions are consistent with the first one except the material; after the second reaction is completed, the above steps are repeated to carry out a 4-cycle degradation experiment, and the results are shown in the figure. Refer to Figure 6 , Figure 6 The continuous degradation experiment results of the Ag / F-SnO2 photocatalytic nanomaterial obtained in the embodiment 1 of the present application are shown in the figure. Figure 6 The stable photocatalytic performance of the Ag / F-SnO2 photocatalytic nanomaterial is shown, and the toluene degradation efficiency is maintained at about 86% in the 4 continuous degradation experiments, which indicates that the photocatalytic activity of the Ag / F-SnO2 photocatalytic nanomaterial remains good after four cycles.

[0071] The photothermal synergistic effect of the material is further illustrated by the following experiment:

[0072] The experiment and the catalytic reaction experiment steps are the same, under the irradiation of a 300W xenon lamp, the catalyst dosage is 0.10g, the initial concentration of toluene is 100ppm, but the initial temperature is controlled at 20°C, 40°C, 60°C and 80°C respectively. Refer to Figure 7 , Figure 7 The toluene removal rate results of the Ag / F-SnO2 obtained in the embodiment 1 of the present application at different temperatures are shown in the figure. When the initial temperature is 20°C, 40°C, 60°C and 80°C respectively, the degradation rates of toluene are 64%, 86.3%, 93% and 88.5% respectively.

[0073] As can be seen, by controlling the degradation temperature, the degradation rates are obviously different, which indicates that the material has a thermal catalytic effect and has a photothermal synergistic effect (it is the synergistic effect of two catalytic forms), that is, the Ag / F-SnO2 material has a photothermal catalytic degradation ability. The Ag / F-SnO2 material shows the highest degradation rate under the condition that the initial temperature is 60°C, and the degradation efficiency of toluene is as high as 93% after 80 min.

[0074] For the method embodiments, the acts performed as part of the method embodiments are referred to using process parameters such as "employing" or "employing a" or "using" or "using a" or the like. When performing the acts, process parameters can be determined by a skilled person in the field of the application. The skilled person will understand that the order of the acts can be changed, and that some acts can be performed simultaneously. The skilled person will also understand that the acts described in the specification are preferred acts, and that not all of the acts are necessary for the application.

[0075] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the present specification.

[0076] The above describes in detail the preparation method and application of the light-heat synergistic catalytic nanomaterial Ag / F-SnO2 provided by the present application for efficiently degrading VOCs, especially formaldehyde. The principles and implementation modes of the present application are described by using specific examples. The above embodiment descriptions are only used to help understand the method of the present application and its core idea. Meanwhile, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed. In summary, the content of the present specification should not be understood as a limitation of the present application.

Claims

1. A method for preparing Ag / F-SnO2, a photothermal synergistic catalytic nanomaterial, characterized in that, The preparation method includes: Step 1: After uniformly mixing the tin-containing solution, sodium hydroxide solution, and NH4F solution, a hydrothermal reaction is carried out. The resulting product is centrifuged, washed, dried, and ground to obtain F-doped SnO2. The molar ratio of the tin-containing solution, the sodium hydroxide solution, and the NH4F solution is 1:5:

2. Step 2: Add AgNO3 solution and NaBH4 aqueous solution to the F-SnO2 suspension, and after stirring, standing for layering, separation, washing, drying, and grinding, obtain the nanomaterial Ag / F-SnO2; wherein the mass fraction ratio of the F-SnO2 suspension to the AgNO3 solution is 1:(0.016~0.096); and the molar ratio of the NaBH4 aqueous solution to the AgNO3 solution is 4:1; In step 1, the NH4F solution is obtained by adding NH4F dropwise to an ethanol solution.

2. The preparation method according to claim 1, characterized in that, In step 1, the temperature of the hydrothermal reaction is 120 ℃~180 ℃, and the holding time of the hydrothermal reaction is 24 h~48 h.

3. The preparation method according to claim 1, characterized in that, In step 1, the mass fraction ratio of the F-SnO2 suspension to the AgNO3 solution is 1:0.

048.

4. The preparation method according to claim 1, characterized in that, In step 1, the tin-containing solution is obtained by dissolving anhydrous tin chloride, tin chloride dihydrate, or tin chloride pentahydrate in deionized water.

5. The preparation method according to claim 1, characterized in that, In step 1, the mixing is achieved by stirring for 20 to 30 minutes; the washing is performed using ultrapure water and anhydrous ethanol; and the drying temperature is 60 to 80 degrees Celsius.

6. The preparation method according to claim 1, characterized in that, In step 2, the F-SnO2 suspension is obtained by dispersing the F-doped SnO2 in step 1 in deionized water; the stirring time is 4 h to 8 h; the washing is performed with alcohol and deionized water; and the drying temperature is 120℃.

7. The preparation method according to claim 1, characterized in that, The loading of Ag nanoparticles in the Ag / F-SnO2 nanomaterial is 3 wt%.

8. An application of a photothermal synergistic catalytic nanomaterial Ag / F-SnO2, characterized in that, The nanomaterial Ag / F-SnO2 obtained by the preparation method according to any one of claims 1-7 is used to degrade VOCs.

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