Titanium dioxide composite material coated with manganese and reduced graphene oxide on surface as well as preparation method and application of titanium dioxide composite material

Abstract

The invention discloses a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface as well as a preparation method and application of the titanium dioxide composite material, and belongs to the technical field of metal oxide catalysts. The preparation method comprises the following steps: S1, dispersing a titanium source in glacial acetic acid, and reacting under the action of moisture in air to obtain turbid liquid; s2, carrying out hydrothermal reaction treatment on the turbid liquid obtained in the step S1 to obtain a TiO2 precursor; s3, carrying out roasting treatment on the TiO2 precursor obtained in the step S2 to obtain TiO2; s4, mixing TiO2 obtained in the step S3, a manganese source and graphene oxide in an organic solvent, and drying to remove the organic solvent to obtain powder; and S5, roasting the powder obtained in the step S4 to obtain the titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface. The composite material disclosed by the invention can be used as a catalyst for VUV photocatalytic oxidation of VOCs, deep oxidation of VOCs is realized, and the mineralization rate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal oxide catalysts, and more specifically, to a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, a preparation method thereof, and an application thereof. Background Art

[0002] Volatile organic compounds (VOCs), especially benzene compounds such as toluene and chlorobenzene, have become one of the main sources of air pollution. VOCs not only pollute the environment, but also pose a threat to human health. Long-term exposure may lead to respiratory system, nervous system diseases and cancers, etc. Therefore, developing efficient VOCs removal technologies is an important task in current environmental governance.

[0003] Photocatalytic oxidation technology is widely used in the removal of VOCs due to its advantages such as environmental friendliness and low energy consumption. However, in the treatment scenarios of VOCs with low concentration and high wind speed, traditional photocatalytic technologies face the problem of low treatment efficiency. Especially for difficult-to-degrade VOCs such as benzene compounds, it is difficult to achieve complete degradation. In recent years, vacuum ultraviolet (VUV) photocatalytic oxidation technology has shown stronger VOCs degradation ability than traditional photocatalytic technologies due to its efficient gas-phase photolysis and photocatalysis synergy. The VUV light source can generate a large number of reactive species (such as ·OH, ·O2 - , O3, etc.) through photolysis reactions. These species have strong oxidation ability and help to accelerate the degradation of VOCs. However, the carrier mobility of existing photocatalysts is low, and the recombination rate of electrons and holes is high, resulting in low energy conversion efficiency in the photocatalytic reaction, which in turn affects the removal effect. At the same time, the concentration of ozone (O3) generated in the VUV photolysis reaction is high and it is difficult to be effectively utilized. This not only reduces the removal efficiency of ozone, but also may cause secondary pollution problems. The catalysts applicable to the VUV photocatalytic oxidation system are very limited.

[0004] The prior art CN109046326B discloses a vacuum ultraviolet photocatalytic purification material, a preparation method thereof, and an application thereof, including a matrix and a loading material. The matrix is mesoporous cerium dioxide, and the loading material is manganese-doped titanium dioxide. The molar ratio of manganese-doped titanium dioxide to cerium dioxide is 0.5-2.0-1. The material has relatively high removal rates of toluene and decomposition rate of ozone, but its mineralization rate is lower than 60%, indicating that although it can degrade toluene, its ability to degrade toluene into COx is too poor, that is, it cannot deeply oxidize VOCs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defect and deficiency of the too low mineralization rate of the existing VUV photocatalyst for degrading VOCs, and to provide a preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface. By a specific method, flower-shaped TiO2 is prepared, and manganese and reduced graphene oxide are coated on the surface of the flower-shaped TiO2 to achieve efficient deep oxidation of VOCs under the VUV photocatalytic system and improve the mineralization rate.

[0006] Another object of the present invention is to provide a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface.

[0007] Another object of the present invention is to provide an application of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface.

[0008] The above objects of the present invention are achieved by the following technical solutions:

[0009] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, comprising the following steps:

[0010] S1. Dispersing a titanium source in glacial acetic acid and reacting under the action of moisture in the air to obtain a suspension;

[0011] S2. Hydrothermally treating the suspension obtained in step S1 to obtain a TiO2 precursor;

[0012] S3. Calcining the TiO2 precursor obtained in step S2 to obtain TiO2;

[0013] S4. Mixing the TiO2, manganese source and graphene oxide obtained in step S3 in an organic solvent, and drying to remove the organic solvent to obtain a powder;

[0014] S5. Calcining the powder obtained in step S4 to obtain a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface;

[0015] Among them, in step S1, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:(50 - 300);

[0016] In step S2, the temperature of the hydrothermal reaction is 80 - 180 °C, and the time of the hydrothermal reaction is 6 - 18 h;

[0017] In step S3, the calcination temperature is 300 - 600 °C, and the calcination time is 1 - 6 h;

[0018] In step S4, the mass ratio of the manganese source to TiO2 is (0.001 - 0.03):1;

[0019] In step S4, the mass ratio of graphene oxide to TiO2 is (0.01 - 0.08):1.

[0020] The present invention provides a method for preparing a titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide. Using glacial acetic acid as a template guiding agent, the titanium source reacts with trace moisture in the ambient air to generate Ti(OH)4, which then polycondenses into a Ti-O-Ti polymer structure. After hydrothermal reaction and air calcination, flower-shaped TiO2 is obtained. Then, through surface impregnation with a manganese source, two-dimensional graphene coating, and reduction fixation, a titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide is obtained.

[0021] The titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide of the present invention can be used as a photocatalyst for VUV photocatalytic oxidation of VOCs. This is because in the composite material of the present invention, the flower-shaped titanium dioxide structure is rich in mesoporous structures due to particle and layered stacking, and at the same time exposes more active sites. The reduced graphene oxide loaded on the surface of the flower-shaped titanium dioxide acts as an electron transport medium and a reducing agent, improving the mobility of photo-generated carriers and promoting the formation of oxygen vacancies, thereby enhancing the photocatalytic and O3 activation capabilities of the catalyst. The manganese loading further forms functional adjacent sites with the oxygen vacancies, enriching electron storage and promoting O3 activation, and further adapting to VUV photocatalytic oxidation.

[0022] The catalyst prepared by the above preparation method has rich adsorption pores and catalytic active sites. The special structure of this material can maximize the enhancement of light absorption and photoluminescence quantum yield, enhance the migration efficiency of photo-generated carriers, and at the same time strengthen O3 decomposition and activation, realizing efficient and deep oxidation of VOCs under the VUV photocatalytic system. It has excellent catalytic oxidation performance and stability and can be applied to the deep oxidation of pollutants in the atmospheric field.

[0023] By controlling the reaction conditions of steps S1 to S3 of the present invention, flower-shaped TiO2 can be obtained.

[0024] In a specific embodiment, the manganese source can be one or more of manganese acetate tetrahydrate, manganese chloride tetrahydrate, or manganese sulfate. Preferably, it is manganese acetate tetrahydrate.

[0025] In a specific embodiment, the titanium source can be one or more of tetrabutyl titanate and isopropyl titanate. Preferably, it is tetrabutyl titanate.

[0026] Preferably, in step S1, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:(100 - 300).

[0027] The molar ratio of titanium element in the titanium source to glacial acetic acid being 1:(100 - 300) is beneficial to the formation of flower-shaped TiO2.

[0028] More preferably, in step S1, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:(100 - 250).

[0029] More preferably, in step S1, the molar ratio of titanium element to glacial acetic acid in the titanium source is 1:(150 - 250).

[0030] Preferably, in step S2, the temperature of the hydrothermal reaction is 120 - 160 °C, and the time of the hydrothermal reaction is 10 - 14 h.

[0031] More preferably, in step S2, the temperature of the hydrothermal reaction is 100 - 140 °C, and the time of the hydrothermal reaction is 10 - 14 h.

[0032] Preferably, in step S3, the calcination temperature is 350 - 550 °C, and the calcination time is 1 - 6 h.

[0033] More preferably, in step S3, the calcination temperature is 400 - 500 °C, and the calcination time is 3 - 5 h.

[0034] The heating rate from room temperature to the required calcination temperature can be 5 - 15 °C / min.

[0035] Preferably, in step S4, the mass ratio of the manganese source to TiO2 is (0.001 - 0.015):1.

[0036] More preferably, in step S4, the mass ratio of the manganese source to TiO2 is (0.001 - 0.005):1.

[0037] Even more preferably, in step S4, the mass ratio of the manganese source to TiO2 is (0.002 - 0.003):1.

[0038] Preferably, in step S4, the mass ratio of graphene oxide to TiO2 is (0.02 - 0.06):1.

[0039] More preferably, in step S4, the mass ratio of graphene oxide to TiO2 is (0.03 - 0.05):1.

[0040] Even more preferably, in step S4, the mass ratio of graphene oxide to TiO2 is (0.03 - 0.04):1.

[0041] Preferably, in step S5, the calcination temperature is 50 - 400 °C, and the calcination time is 1 - 6 h.

[0042] More preferably, in step S5, the calcination temperature is 100 - 300 °C, and the calcination time is 1 - 3 h.

[0043] The heating rate from room temperature to the required calcination temperature can be 5 - 15 °C / min.

[0044] In a specific implementation method, the preparation method of the titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide includes the following steps:

[0045] S1. Dropwise disperse tetrabutyl titanate in glacial acetic acid, and stir and react sufficiently at room temperature to obtain a suspension;

[0046] S2. Transfer the suspension in step S1 to a hydrothermal reaction kettle for heating, wash and dry after sufficient reaction to obtain a flower-like TiO2 precursor;

[0047] S3. Calcinate the flower-like TiO2 precursor in step S2 in an air atmosphere to obtain flower-like TiO2;

[0048] S4. Add the flower-like TiO2 in step S3 to an ethanol solution containing manganese acetate tetrahydrate and graphene oxide that is ultrasonically uniform, and evaporate the ethanol by heating;

[0049] S5. Calcinate the finally evaporated powder sample in step S4 in a hydrogen atmosphere to obtain the titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide.

[0050] The present invention also protects the titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide prepared by any of the above preparation methods.

[0051] Preferably, the diameter of the composite material is 0.5 - 1.5 μm.

[0052] The present invention also protects the application of the titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide in the VUV photocatalytic oxidation of VOCs.

[0053] Preferably, in the application, the environmental humidity is 0 - 90%.

[0054] The composite material of the present invention can be used as a catalyst for VUV photocatalytic VOCs, and can efficiently oxidize VOCs under the condition of environmental humidity RH = 0 - 90%. It has a broad spectrum of adaptability.

[0055] More preferably, in the application, the environmental humidity is 40 - 60%.

[0056] Even more preferably, in the application, the environmental humidity is 50%.

[0057] The present invention also protects a method for degrading benzene-based VOCs. Under the irradiation of a VUV light source, the benzene-based VOCs are reacted through a reactor containing the titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide.

[0058] Preferably, the benzene-based VOCs are one or more of toluene and chlorobenzene.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] The present invention provides a preparation method of a titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide. Using glacial acetic acid as a template guiding agent, the titanium source reacts with trace moisture in the ambient air to form Ti(OH)4, which then polycondenses into a Ti-O-Ti polymer structure. After hydrothermal reaction and air calcination, flower-shaped TiO2 is obtained. Then, through surface impregnation with a manganese source, two-dimensional graphene coating, and reduction fixation, a titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide is obtained.

[0061] The titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide prepared by the preparation method of the present invention can be used as a photocatalyst for VUV photocatalytic oxidation of VOCs. Under the VUV photocatalytic oxidation system, it can stably maintain a VOCs removal rate of more than 67% and a mineralization rate of more than 80% for a long time in the full humidity range (RH = 0 - 90%). It has excellent catalytic oxidation performance and stability and can be applied to the deep oxidation of pollutants in the atmospheric field. Brief Description of the Drawings

[0062] Figure 1 It is the preparation process of the composite material in Example 1.

[0063] Figure 2 It is the SEM and TEM test diagrams of the composite material in Example 1. Figure 2 a, 2b, and 2c are respectively the SEM, TEM, and HRTEM diagrams of the composite material in Example 1.

[0064] Figure 3 It is the test result diagram of energy dispersive X-ray spectroscopy (EDS) surface scanning mapping for the composite material in Example 1. Figure 3 a is the overall morphology diagram of the composite material. Figure 3 b, Figure 3 c, Figure 3 d, and Figure 3 e respectively correspond to the distribution of Ti element, O element, C element, and Mn element in the composite material of Example 1.

[0065] Figure 4 in Figure 4 a is the electron paramagnetic resonance (EPR) test diagram of the materials in Example 1, Comparative Example 1, and Comparative Example 2. Figure 4 b is the X-ray photoelectron spectroscopy test diagram of the materials in Example 1, Comparative Example 1, and Comparative Example 2.

[0066] Figure 5 in Figure 5a, 5b, and 5c are respectively the test result diagrams of photocurrent response, electrochemical impedance, and photoluminescence spectrum of the composite material in Example 1, the material in Comparative Example 1, and the material in Comparative Example 2.

[0067] Figure 6 It is a schematic structural diagram of the device for VUV photocatalytic oxidation continuous flow VOCs test.

[0068] Figure 7 It is the test diagram of the cyclic stability performance of the composite material in Example 1 for degrading gaseous toluene. Detailed implementation manners

[0069] The present invention will be further described below in conjunction with the detailed implementation manners, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the raw material reagents used in the embodiments of the present invention are conventional raw material reagents purchased.

[0070] Graphene oxide, the manufacturer is Jiangsu Xianfeng Nano Materials Technology Co., Ltd., and the grade is XFQ023.

[0071] Example 1

[0072] As Figure 1 shown, a preparation method of a titanium dioxide composite material with a surface coated with manganese and reduced graphene oxide includes the following steps:

[0073] S1. Dropwise disperse tetrabutyl titanate in glacial acetic acid, stir at room temperature, and react sufficiently under the action of moisture in the air to obtain a suspension; among them, the addition amounts of tetrabutyl titanate and glacial acetic acid are 2 mL and 60 mL respectively; that is, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:150;

[0074] S2. Transfer the suspension obtained in step S1 to a hydrothermal reaction kettle for heating, wash and dry after sufficient reaction to obtain a flower-shaped TiO2 precursor; among them, the hydrothermal temperature is 140 °C and the hydrothermal treatment time is 12 h;

[0075] S3. Calcinate the flower-shaped TiO2 precursor obtained in step S2 in an air atmosphere to obtain flower-shaped TiO2 (FT); among them, the calcination temperature is 400 °C, the calcination time is 3 h, and the heating rate is 10 °C / min;

[0076] S4. Add the flower-shaped TiO2 obtained in step S3 to an ethanol solution containing manganese acetate tetrahydrate and graphene oxide that is ultrasonically uniform, and evaporate the ethanol by heating; among them, the mass ratio of manganese acetate tetrahydrate to flower-shaped TiO2 is 0.003:1; the mass ratio of graphene oxide to flower-shaped TiO2 is 0.03:1;

[0077] S5. Bake the finally dried powder sample in a hydrogen atmosphere to obtain a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface; wherein, the baking temperature is 200 °C, the baking time is 2 h, and the heating rate is 10 °C / min. This material is abbreviated as FT@Mn / rGO.

[0078] Example 2

[0079] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S4, the mass ratio of graphene oxide to flower-like TiO2 is 0.01:1.

[0080] Example 3

[0081] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S4, the mass ratio of graphene oxide to flower-like TiO2 is 0.05:1.

[0082] Example 4

[0083] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S4, the mass ratio of manganese acetate tetrahydrate to flower-like TiO2 is 0.001:1.

[0084] Example 5

[0085] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S4, the mass ratio of manganese acetate tetrahydrate to flower-like TiO2 is 0.015:1.

[0086] Example 6

[0087] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S1, the addition amounts of tetrabutyl titanate and glacial acetic acid are 2 mL and 30 mL respectively. That is, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:75.

[0088] Example 7

[0089] A preparation method of a titanium dioxide composite material coated with manganese and reduced graphene oxide on the surface, including steps substantially the same as those in Example 1, the difference being that: in step S3, the baking temperature is 550 °C.

[0090] Comparative Example 1

[0091] A preparation method of TiO2, which is different from that of Example 1 in that it does not include step S4 and step S5.

[0092] Comparative Example 2

[0093] A preparation method of a TiO2@rGO catalyst, which is different from that of Example 1 in that in step S4, manganese acetate tetrahydrate is not included in the ethanol solution.

[0094] Comparative Example 3

[0095] A kind of nano-titanium dioxide, manufactured by Degussa Company of Germany, with the brand number P25.

[0096] Comparative Example 4

[0097] A preparation method of Mn / TiO2, which is different from that of Example 1 in that in step S4, graphene oxide is not included in the ethanol solution.

[0098] Comparative Example 5

[0099] A preparation method of granular Mn / rGO / TiO2, which is different from that of Example 1 in that glacial acetic acid is replaced by deionized water.

[0100] Result detection

[0101] The titanium dioxide composites with surface-coated manganese and reduced graphene oxide of Examples 1 to 5, the materials of Comparative Example 1 and the materials of Comparative Example 2 are respectively subjected to structural characterization and performance testing.

[0102] (1) SEM and TEM tests:

[0103] The composites of Example 1 are subjected to SEM and TEM tests, and the results are as Figure 2 shown, Figure 2 a, 2b and 2c are respectively the SEM, TEM and HRTEM diagrams of the composites of Example 1. It can be seen from the figure that the composites of Example 1 have a flower-like structure with a diameter of about 1 μm, and the surface is rough and coated with flaky substances, indicating that the surface is coated with reduced graphene oxide. The flower-like structure therein is formed by connecting and stacking nanoparticles with a diameter of about 10 nm. The lattice fringe of the particles with 0.35 nm belongs to the (101) crystal plane of TiO2 (JCPDS 73-1764), indicating that the flower-like TiO2 morphology takes glacial acetic acid as a template guiding agent to form a flower-like structure network, and then a large number of TiO2 nanoparticles are crystallized through hydrothermal treatment and calcination, and finally a flower-like structure is formed. Such a structure helps the catalyst to form active sites such as pores and oxygen vacancies, enhancing the adsorption and photocatalytic ability of VOCs.

[0104] (2) EDS test:

[0105] The composite material of Example 1 was subjected to energy-dispersive X-ray spectroscopy (EDS) surface scanning mapping, and the test results are as Figure 3 shown, where Figure 3 a is the overall morphology of the composite material, Figure 3 b, 3c, 3d and 3e respectively correspond to the distribution of Ti element, O element, C element and Mn element in the composite material of Example 1. It can be seen that rGO and Mn are uniformly loaded on the surface of TiO2.

[0106] (3) Qualitative and quantitative tests of oxygen vacancies

[0107] The materials of Example 1, Comparative Example 1 and Comparative Example 2 were subjected to electron paramagnetic resonance (EPR) test and X-ray photoelectron spectroscopy test, and the test results are as Figure 4 shown in a and 4b, Figure 4 The EPR result of a detected the oxygen vacancy signal (g = 2.004) of the material, proving the formation of oxygen vacancies, Figure 4 b analyzed the ratio of the peak areas of adsorbed oxygen and lattice oxygen in XPS (S ads / S latt ), which can indicate the oxygen vacancy content. The ratio of the peak areas of adsorbed oxygen and lattice oxygen in the material of Example 1 (S ads / S latt ) was 43.8%, the ratio of the peak areas of adsorbed oxygen and lattice oxygen in the material of Comparative Example 1 (S ads / S latt ) was 15.9%, and the ratio of the peak areas of adsorbed oxygen and lattice oxygen in the material of Comparative Example 2 (S ads / S latt ) was 18.3%. It can be seen that in Example 1, due to the loading effect of Mn and rGO, a large number of oxygen vacancies were formed in the material.

[0108] (4) Photon yield and photogenerated carrier migration performance tests:

[0109] Figure 5 a, 5b and 5c are the test results of photocurrent response, electrochemical impedance and photoluminescence spectrum of the composite material of Example 1, the material of Comparative Example 1 and the material of Comparative Example 2. The photocurrent generated by the composite material of Example 1 after illumination was the highest, and it had the lowest electron transport resistance. At the same time, the recombination rate of photogenerated carriers was the lowest. Thus, it can be seen that the photon yield and the migration efficiency of photogenerated carriers of the catalyst were significantly improved after surface coating with Mn and rGO.

[0110] The test results of photocurrent response, electrochemical impedance and photoluminescence spectrum of the material in Comparative Example 1 show that it has the lowest photogenerated electron yield, the largest electron transfer resistance and the most photogenerated carrier recombination, proving the relatively weak photoluminescence quantum yield and photogenerated carrier migration efficiency of the material in Comparative Example 1; the photoluminescence quantum yield and photogenerated carrier migration efficiency of the material in Comparative Example 2 are improved to a certain extent compared with those in Comparative Example 1. This is because rGO, as a good electron transfer medium, promotes the rapid transfer of photogenerated electrons to the catalyst surface. However, the photoluminescence quantum yield and photogenerated carrier migration efficiency of the material in Comparative Example 2 are not as good as those of the composite catalyst in Example 1. This is because the uniform dispersion of Mn on the surface of the catalyst in Example 1 provides abundant empty orbitals for surface electrons and improves the storage of electrons on the catalyst surface.

[0111] (5) VUV photocatalytic oxidation continuous flow VOCs test

[0112] The experimental device is as Figure 6 shown. In the continuous flow system, the flow rate of the VOCs waste gas is set to 1 L / min, and the addition amount of the catalyst is 100 mg. A VUV lamp is selected, manufactured by Foshan Kewi Optoelectronic Co., Ltd., model ZW10D15Y-Z212, with a lamp power of 10 W and ultraviolet wavelengths including 185 nm ultraviolet and 254 nm ultraviolet.

[0113] The reactor is a flat plate reactor.

[0114] VOCs degradation rate (%) = (import concentration of VOCs - export concentration of VOCs) / import concentration of VOCs × 100%;

[0115] CO selectivity = (import concentration of CO - export concentration of CO * n) / import concentration of CO × 100%, where n represents the number of carbon atoms in the VOC molecule;

[0116] CO2 selectivity = (import concentration of CO2 - export concentration of CO2 * n) / import concentration of CO2 × 100%, where n represents the number of carbon atoms in the VOC molecule;

[0117] Mineralization rate (%) = CO x selectivity = CO selectivity + CO2 selectivity;

[0118] O3 removal rate (%) = (import concentration of O3 - export concentration of O3) / import concentration of O3 × 100%.

[0119] The test results of the toluene removal rate, COx selectivity and O3 removal rate of the catalyst in each example and comparative example by VUV photocatalytic oxidation are shown in Table 1.

[0120] Table 1

[0121]

[0122]

[0123] The test results of the removal rates of chlorobenzene, the selectivity of COx, and the removal rate of O3 by the catalyst in each example and comparative example are shown in Table 2.

[0124] Table 2

[0125]

[0126] As can be seen from the data in Table 1 and Table 2, the degradation rate of toluene by the titanium dioxide composite material (FT@Mn / rGO) catalyst with manganese and reduced graphene oxide coated on the surface in the VUV photocatalytic oxidation system of the examples of the present invention reaches 72%-77%, the mineralization rate reaches 83%-90%, and the O3 removal rate reaches 79%-90%. When the titanium dioxide composite material (FT@Mn / rGO) catalyst with manganese and reduced graphene oxide coated on the surface in the examples of the present invention is used for photocatalytic oxidation of chlorobenzene, the removal rate, mineralization rate, and O3 removal rate of chlorobenzene reach 67-84%, 96-100%, and 61-79%, respectively. That is, the FT@Mn / rGO catalyst of the present invention has excellent VOCs degradation and mineralization capabilities, and at the same time enhances the catalytic activation and decomposition performance of O3.

[0127] However, the toluene degradation rate, mineralization rate, and O3 removal rate of the materials in Comparative Example 1 and Comparative Example 2 are significantly lower than those in the examples when degrading toluene, and the chlorobenzene degradation rate, mineralization rate, and O3 removal rate of the materials in Comparative Example 1 and Comparative Example 2 are also significantly lower than those in the examples when degrading chlorobenzene. This shows that the lack of Mn or the surface loading of rGO cannot simultaneously meet the requirements of high photocatalytic quantum yield, photogenerated carrier transport, and O3 catalytic activation, resulting in lower VOCs degradation and O3 decomposition and utilization performance. This may be because only rGO is coated on the surface of FT in Comparative Example 2, which can improve the photogenerated carrier mobility of the catalyst to a certain extent, but cannot enhance the activation of O3 for efficient degradation of toluene. In Comparative Example 4, only Mn is loaded on the surface of FT. Due to the lack of a carrier to disperse Mn, it leads to the occupation of photocatalytic active sites and a decrease in catalytic activity.

[0128] In Comparative Example 3, the toluene degradation rate, mineralization rate, and O3 removal rate of the commercial P25 catalyst are significantly lower than those of the present invention when degrading toluene, indicating that the particle structure of P25 is not conducive to the exposure of active sites, VOCs degradation, and O3 activation. The pore structure and surface defects such as oxygen vacancies on the surface of the flower-shaped FT@Mn / rGO catalyst of the present invention provide rich sites for the adsorption and activation of VOCs and O3, thus enhancing the degradation effect.

[0129] In Comparative Example 5, the toluene degradation rate, mineralization rate, and O3 removal rate of granular Mn / rGO / TiO2 were significantly lower than those of the present invention, indicating that Mn and rGO could not interact with granular TiO2 to form multiple active sites, and the oxygen vacancy content was low, resulting in low photocatalytic activity. The oxidized small-molecule substances were desorbed before they could be further oxidized, leading to low toluene removal rate and mineralization rate.

[0130] As can be seen from Examples 1 to 5, the composite material in Example 1 had the best performance in enhancing photocatalytic performance and O3 activation ability. This may be because the loadings of Mn and rGO were slightly low, which may lead to insignificant improvement in the transfer ability of photo-generated carriers and too few O3 adsorption sites, resulting in insignificant performance changes. Higher loadings of Mn and rGO may hinder the exposure of TiO2 lattice and active oxygen vacancy sites, thus causing a slight decrease in performance.

[0131] (6) Long-term stability test under different environmental humidities

[0132] It is Figure 7 known that the FT@Mn / rGO catalyst of the present invention maintained a chlorobenzene degradation rate of over 80% and a mineralization rate of over 99% during long-term continuous-flow degradation of chlorobenzene at different relative humidities (0 - 90%), and there was no inactivation phenomenon for over 1300 min, proving that the FT@Mn / rGO catalyst of the present invention can achieve long-term deep catalytic oxidation of VOCs in the VUV photocatalytic oxidation system.

[0133] Obviously, the above examples of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a titanium dioxide composite material coated with manganese and reduced graphene oxide, characterized in that: The steps include: S1. The titanium source is dispersed in glacial acetic acid and reacted under the action of moisture in the air to obtain a suspension; S2. The suspension obtained in step S1 is subjected to a hydrothermal reaction to obtain a TiO2 precursor; S3. The TiO2 precursor obtained in step S2 is calcined to obtain TiO2; S4. The TiO2, manganese source and graphene oxide obtained in step S3 are mixed in an organic solvent, and the organic solvent is removed by drying to obtain a powder; S5. calcining the powder obtained in step S4 to obtain a titanium dioxide composite material coated with manganese and reduced graphene oxide; Wherein, in step S1, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:(50-300); In step S2, the temperature of the hydrothermal reaction is 80-180° C., and the time of the hydrothermal reaction is 6-18 hours; In step S3, the calcination temperature is 300-600°C and the calcination time is 1-6h; In step S4, the mass ratio of manganese source to TiO2 is (0.001-0.03):1; In step S4, the mass ratio of graphene oxide to TiO2 is (0.01-0.08):

1.

2. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S1, the molar ratio of titanium element in the titanium source to glacial acetic acid is 1:(100-250).

3. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S2, the temperature of the hydrothermal reaction is 120-160° C., and the time of the hydrothermal reaction is 10-14 h.

4. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S3, the calcination temperature is 400-500° C. and the calcination time is 3-5 hours.

5. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S4, the mass ratio of the manganese source to TiO2 is (0.001-0.005):

1.

6. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S4, the mass ratio of graphene oxide to TiO2 is (0.02-0.06):

1.

7. The method for preparing the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 1, characterized in that: In step S5, the calcination temperature is 50-400° C. and the calcination time is 1-6 hours.

8. A titanium dioxide composite material with surface coated manganese and reduced graphene oxide prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the titanium dioxide composite material with surface coated manganese and reduced graphene oxide as claimed in claim 8 in VUV photocatalytic oxidation of VOCs.

10. A method for degrading benzene-based VOCs, characterized in that: Under the irradiation of VUV light source, benzene-based VOCs are reacted through a reactor containing the titanium dioxide composite material with surface-coated manganese and reduced graphene oxide as claimed in claim 8.

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