Preparation method of composite metal-based catalyst powder as well as preparation method and application of electrode for electro-catalytic degradation of benzene series VOCs (Volatile Organic Compounds)

Abstract

The invention provides a preparation method of composite metal-based catalyst powder as well as a preparation method and application of an electrode for electro-catalytic degradation of benzene series VOCs (Volatile Organic Compounds). According to the preparation method of the composite metal-based catalyst powder, oxides or chlorides corresponding to metal elements La, Ce, Sn and Ta and TiN powder are used for preparing the composite metal-based catalyst powder, TiO2 serves as a matrix of the prepared composite metal-based catalyst powder, and the composite metal-based catalyst powder has excellent performance in an electro-activated persulfate system; oxides or oxychlorides corresponding to metal elements are doped in a nanometer titanium dioxide matrix to prepare composite metal-based catalyst powder, the composite metal-based catalyst powder is used for modifying an electrode in a system, and the modified electrode has a high degradation rate when used for degrading benzene series VOCs in an electro-catalysis persulfate system.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode preparation, and in particular to a method for preparing composite metal-based catalyst powder, and a method for preparing and applying an electrode for electrocatalytic degradation of benzene series VOCs. Background Art

[0002] It is well known that the electrochemical and catalytic properties of electrodes will greatly affect the electrochemical process, thereby affecting the rate and efficiency of the electrochemical reaction. Specifically for the system of activating persulfate to oxidize benzene VOCs, the main points include the following two: First, different electrode materials have different hydrogen and oxygen evolution potentials. When there are other halogen elements such as chlorine in the electrolyte, chlorine evolution will also occur. In most electrochemical advanced oxidation processes, whether it is hydrogen evolution, oxygen evolution or chlorine evolution, it is usually a side reaction and may compete with the main reaction (including the oxidation of benzene VOCs and the activation of persulfate), resulting in a decrease in the oxidation rate and efficiency. Therefore, it is usually hoped to find electrode materials with higher hydrogen and oxygen evolution potentials to carry out the electrochemical oxidation process in order to improve the removal rate of benzene VOCs. Secondly, different electrode materials also have different activities in the redox process, which is mainly due to the different surface morphology, number of active sites and electron transport properties of different materials. If the surface morphology of the electrode is richer and the average particle size is smaller, the electrode will have higher stability and a larger specific surface area. These factors can not only increase the number of active sites on the electrode surface, but also enhance the adsorption process of benzene VOCs and persulfate ions to be activated on the electrode surface. The increase in the number of active sites directly increases the area of ​​the electrode surface that can oxidize benzene VOCs and the area that activates persulfate. The electron transport performance is affected by the electron transfer kinetics on the electrode surface. The larger the electron transfer rate constant, the faster the electron transfer on the electrode surface and the better the reaction kinetics. According to the active collision theory, a high electron transfer rate will provide higher energy to increase the number of active molecules and the probability of active collisions, which can increase the probability and rate of the reaction, thereby improving the reaction efficiency. Therefore, all of the above factors are conducive to the enrichment of benzene VOCs and persulfate on the electrode surface, making them more easily oxidized or activated, which ultimately manifests as an increase in the reaction rate and efficiency.

[0003] Since the mid-20th century, various non-precious metal electrodes and functional electrodes have become a research hotspot. The first typical example of non-precious metal electrodes is carbon electrodes, from the earliest graphite electrodes to today's graphene electrodes and carbon nanotube electrodes. The second typical example is metal oxide electrodes, such as various transition metal oxide electrodes. In these electrodes, the properties of the metal atoms have a profound impact on the electrode performance. First, the oxidation state and valence electron structure of the metal atoms determine the conductivity and electron transport properties of the metal oxide. Metals with higher oxidation states generally form oxides with better conductivity, such as nickel oxide (NiO) and cobalt oxide (Co3O4), because they have higher electron density and free electron mobility in the crystal. Second, the crystal structure and lattice defects of the metal oxide also directly affect the surface activity and catalytic performance of the electrode. In addition, lattice defects such as oxygen vacancies or missing metal atoms can enhance the catalytic activity of the electrode. Finally, the electronic state and band structure of the metal atoms are crucial for charge transfer processes and the generation and recombination of electron-hole pairs.

[0004] At present, the more common metal oxide electrode is the DSA (dimensonally stable anode) electrode, which has been widely studied due to its high electrocatalytic activity and stability. DSA electrodes are generally composed of conductive materials and coatings. The conductive materials are usually made of stable metal substrates, such as titanium, platinum-titanium alloys, etc. These materials have good mechanical strength and corrosion resistance, and can maintain the stable size and structure of the electrode during long-term electrochemical reactions. The coating is used to improve the activity and selectivity of the electrode. Common ones include ruthenium-iridium coatings and iridium-tantalum coatings. These electrodes have good performance in most cases, but sometimes they cannot meet the needs of scientific research and industrial production. Therefore, people usually choose to further regulate the electrochemical and catalytic properties of the electrode by modifying the electrode.

[0005] Titanium-based iridium-tantalum electrode (Ti / IrO2-Ta2O5), in which IrO2 exhibits a large electrocatalytic active surface area at the anode, it mainly assumes the electrocatalytic role in the electrode, while Ta2O5 is responsible for maintaining the stability of IrO2 in the system. Since IrO2 itself has good corrosion resistance, the stability of the entire electrode can be further improved after doping with the inert oxide Ta2O5. This phenomenon is attributed to the addition of Ta2O5, which can effectively prevent the coating of the Ti / IrO2 electrode from falling off due to high current density and high processing temperature. At the same time, this also enables the titanium-based iridium-tantalum electrode (Ti / IrO2-Ta2O5) to function in a wider pH range than other electrodes, and even in acidic wastewater, it can exhibit extremely long life at a high removal rate.

[0006] However, the degradation efficiency of the above-mentioned electrodes in the electrocatalytic degradation of benzene-related VOCs is still not high. Based on this, it is necessary to improve the existing electrodes. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing a composite metal-based catalyst powder, a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, and its application in order to solve the problems and deficiencies of the prior art.

[0008] The present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0010] Adding the oxide or chloride corresponding to the metal element to a mixed solution of n-butanol and hydrochloric acid, and ultrasonicating to obtain an impregnation solution;

[0011] impregnating TiN powder in an impregnation solution and drying to obtain a TiN / metal precursor salt reactant;

[0012] calcining the TiN / metal precursor salt reactant to obtain a composite metal-based catalyst powder;

[0013] The metal element includes at least one of La, Ce, Sn, and Ta.

[0014] Preferably, in the step of calcining the TiN / metal precursor salt reactant to obtain the composite metal-based catalyst powder, the calcination temperature is 700-800° C. and the calcination time is 0.5-1 h.

[0015] Preferably, the TiN powder is immersed in the impregnation solution, and in the drying step, the drying temperature is 100-120° C. and the drying time is 1-3 hours.

[0016] Preferably, the volume ratio of n-butanol to hydrochloric acid is (1-5):7;

[0017] The mass concentration of the hydrochloric acid is 36-38%;

[0018] The molar ratio of the oxide or chloride corresponding to the metal element to the TiN powder is (0.1-0.5):0.7;

[0019] The molar volume ratio of the oxide or chloride corresponding to the metal element to the mixed solution of n-butanol and hydrochloric acid is (0.1-0.5) mol: (80-120) mL.

[0020] In a second aspect, the present invention further provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0021] Mixing the composite metal-based catalyst powder prepared by the preparation method, water, ethanol and Nafion solution to obtain a mixed solution;

[0022] The mixed solution is coated on the surface of the anode or cathode and dried to obtain an electrode for electrocatalytic degradation of benzene series VOCs.

[0023] Preferably, the mass volume ratio of the composite metal-based catalyst powder, water, ethanol and Nafion solution is (200-300) mg: (2-5) mL: (2-5) mL: (0.2-0.5) mL;

[0024] The mass fraction of the Nafion solution is 5 to 7%.

[0025] In a third aspect, the present invention also provides an application of an electrode prepared by the preparation method in the degradation of benzene series VOCs in an electrocatalytic persulfate system.

[0026] Preferably, the application comprises the following steps:

[0027] Na2S2O8 aqueous solution was used as the electrolyte;

[0028] The electrode for electrocatalytic degradation of benzene series VOCs prepared by the preparation method is used as an anode or a cathode;

[0029] providing an additional electrode to act as a cathode or anode;

[0030] Adding benzene VOCs into the electrolyte;

[0031] The power supply is connected to the electrode for electrocatalytic degradation of benzene series VOCs and another electrode respectively, and the power supply is turned on to electrocatalytically degrade the benzene series VOCs.

[0032] Preferably, in the application, Na2S2O8 is added to water to obtain a Na2S2O8 aqueous solution with a concentration of 0.5 to 1 mol / L, and the pH of the Na2S2O8 aqueous solution is adjusted to 9 to 11, and the Na2S2O8 aqueous solution after pH adjustment is used as an electrolyte.

[0033] Preferably, in the application, during electrolysis, the temperature of the electrolyte is controlled to be 60-70°C and the current density is 160-170A / m 2 .

[0034] The composite metal-based catalyst powder and its preparation method of the present invention have the following advantages over the prior art:

[0035] Beneficial effects:

[0036] 1. The preparation method of the composite metal-based catalyst powder of the present invention uses oxides or chlorides corresponding to the metal elements La, Ce, Sn, and Ta, and TiN powder to prepare the composite metal-based catalyst powder. The prepared composite metal-based catalyst powder uses TiO2 as a matrix. Titanium dioxide has excellent performance in an electro-activated persulfate system. The oxides or chloride oxides corresponding to the metal elements are doped into a nano-titanium dioxide matrix to prepare the composite metal-based catalyst powder, and the composite metal-based catalyst powder is used to modify the electrode in the system. The modified electrode has a high degradation rate when degrading benzene series VOCs in the electrocatalytic persulfate system;

[0037] 2. After the composite metal-based catalyst powder is loaded on the anode surface of the present invention, the time to reach equilibrium is greatly shortened; from the perspective of mineralization rate, the mineralization rate of the anode electrode modified with the four metal elements La, Ce, Sn, and Ta is significantly improved compared with the unmodified electrode, from about 60% to about 80%; the mineralization rate of the cathode modified with the four metal elements La, Ce, Sn, and Ta is significantly improved compared with the unmodified electrode, from about 60% to about 80%; among the electrodes modified with the four metal elements La, Ce, Sn, and Ta, the conversion rate of the Sn-modified electrode is the highest, but the mineralization rate of the La-modified electrode is the highest. This is mainly because there is a more obvious direct reaction on the surface of the Sn electrode, there are more active sites and adsorption sites in the electrode, and it is easier to generate various free radicals, so the mineralization rate is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0039] Figure 1 is the XRD pattern of the composite metal-based catalyst powder prepared in Example 1;

[0040] Figure 2 is the XRD pattern of the composite metal-based catalyst powder prepared in Example 2;

[0041] Figure 3 is the XRD pattern of the composite metal-based catalyst powder prepared in Example 3;

[0042] Figure 4 is the XRD pattern of the composite metal-based catalyst powder prepared in Example 4;

[0043] Figure 5The effect of La, Ce, Ta and Sn modified anodes on the conversion rate of chlorobenzene degradation by electrothermal combined activation persulfate system in Example 5;

[0044] Figure 6 The effect of La, Ce, Ta and Sn on the mineralization rate of chlorobenzene degradation in the electrothermal combined activation persulfate system in Example 5 is shown;

[0045] Figure 7 The effect of La, Ce, Ta and Sn on the conversion rate of chlorobenzene degradation by the electrothermal combined activation persulfate system in Example 6 is shown;

[0046] Figure 8 This is the effect of using La, Ce, Ta and Sn to modify the cathode in Example 6 on the mineralization rate of chlorobenzene degradation in the electrothermal combined activation persulfate system. DETAILED DESCRIPTION

[0047] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] In the description of the present invention, it should be understood that the directions or positions indicated by “upper” and the like are based on the directions or positions shown in the accompanying drawings, or are the directions or positions in which the product of the invention is usually placed when in use, or are the directions or positions commonly understood by those skilled in the art. These directions or positions are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0049] The order of description of the following embodiments is not intended to limit the preferred order of the embodiments. In addition, in the description of this application, the term "including" means "including but not limited to". Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be understood as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0050] The present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0051] S1. Add the oxide or chloride corresponding to the metal element to a mixed solution of n-butanol and hydrochloric acid, and sonicate to obtain an impregnation solution;

[0052] S2, immersing the TiN powder in an impregnation solution and drying to obtain a TiN / metal precursor salt reactant;

[0053] S3. calcining the TiN / metal precursor salt reactant to obtain a composite metal-based catalyst powder.

[0054] The present invention utilizes oxides or chlorides corresponding to metal elements La, Ce, Sn, and Ta, and TiN powder to prepare composite metal-based catalyst powder. The prepared composite metal-based catalyst powder uses TiO2 as a matrix. Titanium dioxide has excellent performance in an electro-activated persulfate system. Oxides or chloride oxides corresponding to the metal elements are doped into a nano-titanium dioxide matrix to prepare the composite metal-based catalyst powder, and the composite metal-based catalyst powder is used to modify electrodes in the system. The modified electrodes have a higher degradation rate when degrading benzene series VOCs in the electrocatalytic persulfate system.

[0055] Rare earth element oxides also have many advantages: First, they generally have excellent catalytic activity and can promote the progress of redox reactions. The active sites on the surface of these oxides can increase the reaction rate and efficiency, making them excellent electrocatalysts. Secondly, they have good electrical conductivity and can effectively transfer electrons. At the same time, they also have high chemical stability, are not prone to oxidation, reduction or corrosion reactions, and can exist stably in the electrolyte. Finally, rare earth element oxides also have a variety of crystal structures, including perovskite structure, spinel structure, oxide mixed crystal structure, etc., and this rich crystal structure can provide a variety of crystal planes. These crystal planes can exhibit excellent catalytic activity for different processes under different conditions, which makes it very easy to regulate their electrochemical properties. The electrochemical performance of rare earth element oxide electrodes can be regulated as needed to meet actual needs. These advantages make rare earth element oxides often used as important components of electrode materials.

[0056] In some embodiments, the metal element includes at least one of La, Ce, Sn, and Ta. Specifically, the chlorides corresponding to the metal elements La, Ce, Sn, and Ta are LaCl3, CeCl3, SnCl2, and TaCl5, respectively.

[0057] In some embodiments, in the step of calcining the TiN / metal precursor salt reactant to obtain the composite metal-based catalyst powder, the calcination temperature is 700-800° C. and the calcination time is 0.5-1 h.

[0058] In some embodiments, the TiN powder is immersed in the impregnation solution, and in the drying step, the drying temperature is 100-120° C. and the drying time is 1-3 hours.

[0059] In some embodiments, the volume ratio of n-butanol to hydrochloric acid is (1-5):7;

[0060] The mass concentration of hydrochloric acid is 36-38%;

[0061] The molar ratio of the oxide or chloride corresponding to the metal element to the TiN powder is (0.1-0.5):0.7;

[0062] The molar volume ratio of the oxide or chloride corresponding to the metal element to the mixed solution of n-butanol and hydrochloric acid is (0.1-0.5) mol: (80-120) mL.

[0063] Based on the same inventive concept, the present invention also provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0064] The composite metal-based catalyst powder prepared by the above preparation method, water, ethanol and Nafion solution are mixed to obtain a mixed solution;

[0065] The mixed solution is coated on the surface of the anode or cathode and dried to complete the modification of the electrode with metal elements La, Ce, Sn, and Ta to obtain an electrode for electrocatalytic degradation of benzene series VOCs.

[0066] In some embodiments, the mass volume ratio of the composite metal-based catalyst powder, water, ethanol, and Nafion solution is (200-300) mg: (2-5) mL: (2-5) mL: (0.2-0.5) mL;

[0067] The mass fraction of the Nafion solution is 5 to 7%.

[0068] In some embodiments, the amount of composite metal-based catalyst powder loaded on the electrode is 0.05 to 0.25 mg / cm 2 .

[0069] In some embodiments, the anode is a Ru-Ir anode (50 mm×100 mm, i.e., 100 mm in length and 50 mm in width), and the cathode is a titanium plate cathode (50 mm×100 mm, i.e., 100 mm in length and 50 mm in width).

[0070] Based on the same inventive concept, the present invention also provides an application of an electrode prepared by the above-mentioned preparation method in the degradation of benzene series VOCs (volatile organic compounds) in an electrocatalytic persulfate system.

[0071] In some embodiments, the above application includes the following steps:

[0072] Na2S2O8 aqueous solution was used as the electrolyte;

[0073] The electrode for electrocatalytic degradation of benzene series VOCs prepared by the preparation method is used as an anode or a cathode;

[0074] providing an additional electrode to act as a cathode or anode;

[0075] Adding benzene VOCs into the electrolyte;

[0076] The power supply is connected to the electrode for electrocatalytic degradation of benzene series VOCs and another electrode respectively, and the power supply is turned on to electrocatalytically degrade the benzene series VOCs.

[0077] Specifically, if the electrode used for electrocatalytic degradation of benzene-related VOCs is used as the anode, another electrode is provided as the cathode, such as a pure titanium plate; if the electrode used for electrocatalytic degradation of benzene-related VOCs is used as the cathode, another electrode is provided as the anode, such as a Ru-Ir anode; during electrolysis, the anode and cathode are respectively connected to the positive and negative poles of the power supply through wires.

[0078] In some embodiments, Na2S2O8 is added to water to obtain a Na2S2O8 aqueous solution with a concentration of 0.5 to 1 mol / L, and the pH of the Na2S2O8 aqueous solution is adjusted to 9 to 11. The pH-adjusted Na2S2O8 aqueous solution is used as an electrolyte.

[0079] In some embodiments, during electrolysis, the electrolyte temperature is controlled to be 60-70°C and the current density is controlled to be 160-170 A / m 2 .

[0080] The following further illustrates the preparation method of the composite metal-based catalyst powder of the present application, the preparation method and application of the electrode for electrocatalytic degradation of benzene-related VOCs, with specific examples. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0081] In the following examples, TiN is T819470 nano-titanium nitride with a particle size of 20 nm, provided by MacLean's reagent; the anode is a Ru-Ir anode, specifically a ruthenium titanium coated electrode (Ti / RuO2-TiO2), provided by Xi'an Aierdi Environmental Protection Technology Co., Ltd.; the Nafion solution is specifically N871880 Nafion perfluorinated resin solution with a mass fraction of 5%, provided by MacLean's reagent.

[0082] Example 1

[0083] The present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0084] S1. Add 0.3 mol of LaCl3 to 100 mL of a mixed solution of n-butanol and hydrochloric acid, and sonicate for 1 h to obtain an impregnation solution; the volume ratio of n-butanol to hydrochloric acid is 3:7, and the mass fraction of hydrochloric acid is 37%;

[0085] S2, impregnating 0.7 mol of TiN powder in the impregnation solution, and drying at 120° C. for 1 h to obtain a TiN / metal precursor salt reactant;

[0086] S3. The TiN / metal precursor salt reactant was calcined at 800° C. for 0.5 h to obtain a composite metal-based catalyst powder (denoted as LaOCl-TiO 2 ).

[0087] This embodiment also provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0088] S1. Mix 200 mg of the composite metal-based catalyst powder prepared in Example 1, 2 mL of deionized water, 2 mL of anhydrous ethanol, and 0.2 mL of a 5% by mass Nafion solution to obtain a mixed solution;

[0089] S2. The mixed solution is coated on a Ru-Ir anode and dried at 100°C to obtain an anode for electrocatalytic degradation of benzene series VOCs, that is, a La-modified anode; the mixed solution is coated on a titanium plate cathode and dried at 100°C to obtain a cathode for electrocatalytic degradation of benzene series VOCs, that is, a La-modified cathode.

[0090] Example 2

[0091] The present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0092] S1. Add 0.3 mol of CeCl3 to 100 mL of a mixed solution of n-butanol and hydrochloric acid, and sonicate for 1 h to obtain an impregnation solution; the volume ratio of n-butanol to hydrochloric acid is 3:7, and the mass fraction of hydrochloric acid is 37%;

[0093] S2, impregnating 0.7 mol of TiN powder in the impregnation solution, and drying at 120° C. for 1 h to obtain a TiN / metal precursor salt reactant;

[0094] S3. calcining the TiN / metal precursor salt reactant at 800° C. for 0.5 h to obtain a composite metal-based catalyst powder (denoted as CeO 2 -TiO 2 ).

[0095] This embodiment also provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0096] S1. Mix 200 mg of the composite metal-based catalyst powder prepared in Example 2, 2 mL of deionized water, 2 mL of anhydrous ethanol, and 0.2 mL of a 5% by mass Nafion solution to obtain a mixed solution;

[0097] S2. The mixed solution is coated on a Ru-Ir anode and dried at 100°C to obtain an anode for electrocatalytic degradation of benzene series VOCs, that is, a Ce-modified anode; the mixed solution is coated on a titanium plate cathode and dried at 100°C to obtain a cathode for electrocatalytic degradation of benzene series VOCs, that is, a Ce-modified cathode.

[0098] Example 3

[0099] The present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0100] S1. Add 0.3 mol of SnCl2 to 100 mL of a mixed solution of n-butanol and hydrochloric acid, and sonicate for 1 h to obtain an impregnation solution; the volume ratio of n-butanol to hydrochloric acid is 3:7, and the mass fraction of hydrochloric acid is 37%;

[0101] S2, impregnating 0.7 mol of TiN powder in the impregnation solution, and drying at 120° C. for 1 h to obtain a TiN / metal precursor salt reactant;

[0102] S3. calcining the TiN / metal precursor salt reactant at 800° C. for 0.5 h to obtain a composite metal-based catalyst powder (denoted as SnO 2 -TiO 2 ).

[0103] This embodiment also provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0104] S1. Mix 200 mg of the composite metal-based catalyst powder prepared in Example 3, 2 mL of deionized water, 2 mL of anhydrous ethanol, and 0.2 mL of a 5% by mass Nafion solution to obtain a mixed solution;

[0105] S2. The mixed solution is coated on a Ru-Ir anode and dried at 100°C to obtain an anode for electrocatalytic degradation of benzene series VOCs, that is, a Sn-modified anode; the mixed solution is coated on a titanium plate cathode and dried at 100°C to obtain a cathode for electrocatalytic degradation of benzene series VOCs, that is, a Sn-modified cathode.

[0106] Example 4

[0107] The present invention provides a method for preparing a composite metal-based catalyst powder, comprising the following steps:

[0108] S1. Add 0.3 mol of TaCl5 to a 100 mL mixed solution of n-butanol and hydrochloric acid, and sonicate for 1 h to obtain an impregnation solution; the volume ratio of n-butanol to hydrochloric acid is 3:7, and the mass fraction of hydrochloric acid is 37%;

[0109] S2, impregnating 0.7 mol of TiN powder in the impregnation solution, and drying at 120° C. for 1 h to obtain a TiN / metal precursor salt reactant;

[0110] S3. The TiN / metal precursor salt reactant is calcined at 800° C. for 0.5 h to obtain a composite metal-based catalyst powder (denoted as Ta 2 O 5 -TiO 2 ).

[0111] This embodiment also provides a method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, comprising the following steps:

[0112] S1. Mix 200 mg of the composite metal-based catalyst powder prepared in Example 4, 2 mL of deionized water, 2 mL of anhydrous ethanol, and 0.2 mL of a 5% by mass Nafion solution to obtain a mixed solution;

[0113] S2. The mixed solution is coated on a Ru-Ir anode and dried at 100°C to obtain an anode for electrocatalytic degradation of benzene series VOCs, that is, a Ta-modified anode; the mixed solution is coated on a titanium plate cathode and dried at 100°C to obtain a cathode for electrocatalytic degradation of benzene series VOCs, that is, a Ta-modified cathode.

[0114] Performance Testing

[0115] Figure 1 This is the XRD pattern of the composite metal-based catalyst powder prepared in Example 1.

[0116] Figure 2 This is the XRD pattern of the composite metal-based catalyst powder prepared in Example 2.

[0117] Figure 3This is the XRD pattern of the composite metal-based catalyst powder prepared in Example 3.

[0118] Figure 4 This is the XRD pattern of the composite metal-based catalyst powder prepared in Example 4.

[0119] from Figures 1 to 4 It can be seen from the figure that after peak comparison with the standard PDF card, it can be seen that the material composition of the four composite metal-based catalyst powders prepared in Examples 1 to 4 is similar, and all contain rutile phase (Rutile) TiO2, anatase phase (Anatase) TiO2 and the corresponding oxides or chloride oxides of La, Ce, Sn, and Ta. Among them, Ce, Sn and Ta produce the corresponding oxides after firing: CeO2, SnO2 and Ta2O5, while La is different and produces chloride oxide LaOCl; In addition, from the perspective of diffraction peak intensity, although the firing temperature and firing time are the same, T The molar ratios of La, Ce, Sn, and Ta are also fixed, but the ratios of the resulting TiO2 crystals to the corresponding oxide or chloride oxide crystals of La, Ce, Sn, and Ta are different. The CeO2 content in the CeO2-TiO2 composite metal-based catalyst nanopowder is significantly higher than that of TiO2. In the LaOCl-TiO2 and Ta2O5-TiO2 composite metal-based catalyst nanopowders, the LaOCl and Ta2O5 contents are roughly equal to those of TiO2. And in the SnO2-TiO2 composite metal-based catalyst nanopowder, the TiO2 content is far greater than that of SnO2. Furthermore, the ratios of the two crystalline phases of TiO2 in the four composite metal-based catalyst nanopowders are also different, and these differences in crystal ratios can affect the catalytic performance of the composite metal-based catalyst nanopowders.

[0120] Example 5

[0121] This embodiment provides an application of the electrode prepared in the above embodiments 1 to 4 in the electrocatalytic persulfate system for the degradation of benzene series VOCs; specifically, the following steps are included:

[0122] S1. Na2S2O8 was added to water to obtain a 0.5 mol / L Na2S2O8 aqueous solution. The pH of the Na2S2O8 aqueous solution was adjusted to 10.0 using a 1.0 mol / L NaOH solution. The pH-adjusted Na2S2O8 aqueous solution was used as an electrolyte.

[0123] S2. The electrolyte in S1 (volume 2.0 L) was placed in an electrolytic cell. The La-modified anode prepared in Example 1 was used as the anode (a wire was provided on the anode, and the wire passed through a sealing plug) and the pure titanium plate was used as the cathode (a wire was provided on the cathode, and the wire passed through a sealing plug). A sealing plug was installed at the upper end of the electrolytic cell.

[0124] S3. Connect the anode and cathode to the positive and negative poles of a power supply via wires, respectively. Pass an air inlet pipe through a sealing plug and extend it into the electrolyte near the bottom of the electrolytic cell. Meanwhile, set an air outlet pipe above the electrolyte in the electrolytic cell. The upper end of the air outlet pipe passes through the sealing plug and extends outside the electrolytic cell.

[0125] Chlorobenzene (one of the VOCs) was introduced into the electrolyte through the air inlet pipe at a certain flow rate v (specifically 1.0 L / min). The electrolyte temperature was controlled at 60 °C. After the power was turned on, electrolysis was carried out and the current density was controlled at 168 A / m 2 (i.e. the current density formed by the cathode plate losing electrons and the anode plate gaining electrons at the same time), the degraded chlorobenzene is discharged through the outlet pipe;

[0126] The initial concentration of chlorobenzene introduced into the electrolyte at the beginning (i.e., before electrolysis) is 1500 ppm.

[0127] According to the above method, the La-modified anode in Example 1 was replaced by the Ce-modified anode in Example 2, the Sn-modified anode in Example 3, the Ta-modified anode in Example 4, and the unmodified Ru-Ir anode, respectively. The other process parameters remained unchanged. The electrochemical degradation of chlorobenzene was carried out according to the method in Example 5, and the conversion rate and mineralization rate of chlorobenzene were tested. The results are as follows: Figures 5-6 shown.

[0128] Example 6

[0129] This embodiment provides an application of the electrode prepared in the above embodiments 1 to 4 in the electrocatalytic persulfate system for the degradation of benzene series VOCs; specifically, the following steps are included:

[0130] S1. Na2S2O8 was added to water to obtain a 0.5 mol / L Na2S2O8 aqueous solution. The pH of the Na2S2O8 aqueous solution was adjusted to 10.0 using a 1.0 mol / L NaOH solution. The pH-adjusted Na2S2O8 aqueous solution was used as an electrolyte.

[0131] S2. The electrolyte in S1 (volume 2.0 L) was placed in an electrolytic cell. The La-modified cathode prepared in Example 1 was used as the cathode (a wire was provided on the cathode and passed through a sealing plug) and the unmodified Ru-Ir anode was used as the anode (a wire was provided on the anode and passed through a sealing plug). A sealing plug was placed at the upper end of the electrolytic cell.

[0132] S3. Connect the anode and cathode to the positive and negative poles of a power supply via wires, respectively. Pass an air inlet pipe through a sealing plug and extend it into the electrolyte near the bottom of the electrolytic cell. Meanwhile, set an air outlet pipe above the electrolyte in the electrolytic cell. The upper end of the air outlet pipe passes through the sealing plug and extends outside the electrolytic cell.

[0133] Chlorobenzene was introduced into the electrolyte through the air inlet pipe at a certain flow rate v (specifically 1.0 L / min), the electrolyte temperature was controlled at 60 °C, and electrolysis was carried out after the power was turned on, and the current density was controlled at 168 A / m 2 (i.e. the current density formed by the cathode plate losing electrons and the anode plate gaining electrons at the same time), the degraded chlorobenzene is discharged through the outlet pipe;

[0134] The initial concentration of chlorobenzene introduced into the electrolyte at the beginning (i.e., before electrolysis) is 1500 ppm.

[0135] According to the above method, the La-modified cathode in Example 1 was replaced by the Ce-modified cathode in Example 2, the Sn-modified cathode in Example 3, the Ta-modified cathode in Example 4, and the unmodified titanium plate cathode, respectively. The other process parameters remained unchanged. The electrochemical degradation of chlorobenzene was carried out according to the method in Example 6, and the conversion rate and mineralization rate of chlorobenzene were tested. The results are as follows: Figures 7-8 shown.

[0136] The calculation method of the conversion rate of chlorobenzene in Examples 5-6 is:

[0137] To more accurately describe the conversion rate of chlorobenzene waste gas in the persulfate system, the present invention obtains the concentration change curve of the inlet and outlet through multiple sampling, and integrates it according to the reaction time to obtain the total amount of chlorobenzene in the reaction and the total amount of chlorobenzene outflow. The total amount of chlorobenzene oxidized and converted by the system at the corresponding time is then deducted from the total amount of chlorobenzene inflow minus the total amount of chlorobenzene outflow and the total amount of chlorobenzene present in the liquid phase at the corresponding time. The total amount of chlorobenzene converted by the system at the corresponding time is then compared with the total amount of chlorobenzene inflow to obtain the conversion rate of chlorobenzene at the reaction time t. The specific calculation method is shown in the following formula:

[0138]

[0139] Where: T t -Chlorobenzene conversion rate at reaction time t, %; ρ CB -Chlorobenzene density under standard conditions, mg / cm 3, specifically 1.106 g / cm 3 ; v-chlorobenzene flow rate 1.0 L / min; C 0,CB - Initial concentration of chlorobenzene in the electrolyte at the beginning (i.e., before electrolysis), 1500ppm; C t,CB -Chlorobenzene concentration at the outlet of the gas pipe, ppm; L-electrolyte volume, 2L; C * t,CB -Chlorobenzene concentration in the liquid phase (i.e., electrolyte) at reaction time t, mg / L.

[0140] The calculation method of the mineralization rate of chlorobenzene in Examples 5-6 is:

[0141] As the oxidation time increases, chlorobenzene will be oxidized and decomposed into organic substances with smaller molecular weight in the sodium persulfate system until it is converted into carbon dioxide, at which point chlorobenzene is completely mineralized. In order to explore the degree of mineralization of chlorobenzene in the activated persulfate system over time, the mineralization rate (denoted by M in the present invention) is used to express the ability of the system to completely oxidize chlorobenzene to inorganic substances.

[0142] In the electro-activated persulfate system, the mineralization rate can be calculated by detecting the concentration of TOC (total organic carbon) in the liquid phase. The calculation formula is as shown below:

[0143]

[0144] Where: M E,t -Chlorobenzene mineralization rate at reaction time t, %; M CB -Chlorobenzene molecular weight, 112.56 g / mol; V-electrolyte volume, 2 L; C 0,TOC -TOC concentration in electrolyte before reaction, mg / L; C t,TOC -TOC concentration in the electrolyte at reaction time t, mg / L; Molecular weight, 44.01 g / mol; ρ CB -Chlorobenzene density under standard conditions, mg / cm 3 , specifically 1.106 g / cm 3 ; v-chlorobenzene flow rate 1.0 L / min; C in,CB Initial concentration of chlorobenzene in the electrolyte at the beginning (i.e. before electrolysis) is 1500ppm; C out,CB -Chlorobenzene concentration at the outlet of the gas pipe at reaction time t, ppm.

[0145] Figure 5 The La-modified anode in Example 1 (ie Figure 5 La in Example 2), Ce-modified anode (ie Figure 5 Ce in the anode modified with Sn in Example 3 (i.e. Figure 5 Sn in Example 4), the Ta-modified anode (ie Figure 5 Ta) and unmodified Ru-Ir anode (i.e. Figure 5 The effect of the original) on the conversion rate (T(%) of chlorobenzene.

[0146] Figure 6 The La-modified anode in Example 1 (ie Figure 6 La in Example 2), Ce-modified anode (ie Figure 6 Ce in the anode modified with Sn in Example 3 (i.e. Figure 6 Sn in Example 4), the Ta-modified anode (ie Figure 6 Ta) and unmodified Ru-Ir anode (i.e. Figure 6 The effect of the original) on the mineralization rate (M(%)) of chlorobenzene.

[0147] Anode materials have significant differences in the efficiency and rate of chlorobenzene degradation in electrocatalytic persulfate systems. Figure 5 It can be found that although the conversion rate can reach more than 95% after 5 hours of reaction time, the electrode loaded with composite metal-based catalyst powder has a conversion rate close to 90% after 1 hour of reaction, while the unmodified electrode has not yet reached 80% conversion rate after 4 hours. That is, after the composite metal-based catalyst powder is loaded on the surface of the anode material, the time to reach equilibrium is greatly shortened. In terms of mineralization rate, Figure 6 It shows that the mineralization rate of the four modified anode electrodes is significantly improved compared with the unmodified electrode, increasing from about 60% to about 80%.

[0148] Figure 7 The cathode modified by La in Example 1 (ie Figure 7 La in Example 2), Ce-modified cathode (ie Figure 7 Ce in the example 3), the cathode modified with Sn in the example 3 (ie Figure 7 Sn in Example 4), the cathode modified by Ta in Example 4 (ie Figure 7 Ta) and unmodified titanium cathode (i.e. Figure 7 The effect of the original) on the conversion rate (T(%) of chlorobenzene.

[0149] Figure 8 The cathode modified by La in Example 1 (ie Figure 7 La in Example 2), Ce-modified cathode (ie Figure 7 Ce in the example 3), the cathode modified with Sn in the example 3 (ie Figure 7 Sn in Example 4), the cathode modified by Ta in Example 4 (ie Figure 7 Ta) and unmodified titanium cathode (i.e. Figure 7 The effect of the original) on the mineralization rate (M(%)) of chlorobenzene.

[0150] The efficiency and rate of the cathode electrode in activating the persulfate system to degrade chlorobenzene also showed significant differences. Figure 7 It can be found that although the conversion rate can reach more than 95% after 5 hours of reaction time, the cathode material loaded with composite metal-based catalyst powder has a conversion rate close to 90% after 1 hour of reaction; from the perspective of mineralization rate, Figure 8 The mineralization rates of the four modified cathodes were significantly improved compared to the unmodified electrodes, rising from approximately 60% to 80%. Among the four metal elements La, Ce, Sn, and Ta-modified electrodes, the Sn-modified electrode had the highest conversion rate, but the La-modified electrode had the highest mineralization rate. This is primarily due to the more pronounced direct reaction of chlorobenzene on the Sn electrode surface, resulting in more active and adsorption sites, making it more likely to generate various free radicals, leading to a higher mineralization rate.

[0151] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a composite metal-based catalyst powder, characterized in that: The following steps are involved: Adding the oxide or chloride corresponding to the metal element to a mixed solution of n-butanol and hydrochloric acid, and ultrasonicating to obtain an impregnation solution; impregnating TiN powder in an impregnation solution and drying to obtain a TiN / metal precursor salt reactant; calcining the TiN / metal precursor salt reactant to obtain a composite metal-based catalyst powder; The metal element includes at least one of La, Ce, Sn, and Ta.

2. The method for preparing the composite metal-based catalyst powder according to claim 1, wherein: In the step of calcining the TiN / metal precursor salt reactant to obtain the composite metal-based catalyst powder, the calcination temperature is 700-800° C. and the calcination time is 0.5-1 hour.

3. The method for preparing the composite metal-based catalyst powder according to claim 1, wherein: The TiN powder is immersed in the impregnation solution. In the drying step, the drying temperature is 100 to 120° C. and the time is 1 to 3 hours.

4. The method for preparing the composite metal-based catalyst powder according to claim 1, wherein: The volume ratio of n-butanol to hydrochloric acid is (1-5):7; The mass concentration of the hydrochloric acid is 36-38%; The molar ratio of the oxide or chloride corresponding to the metal element to the TiN powder is (0.1-0.5):0.7; The molar volume ratio of the oxide or chloride corresponding to the metal element to the mixed solution of n-butanol and hydrochloric acid is (0.1-0.5) mol: (80-120) mL.

5. A method for preparing an electrode for electrocatalytic degradation of benzene series VOCs, characterized in that: The following steps are involved: The composite metal-based catalyst powder prepared by the preparation method according to any one of claims 1 to 4 is mixed with water, ethanol and Nafion solution to obtain a mixed solution; The mixed solution is coated on the surface of the anode or cathode and dried to obtain an electrode for electrocatalytic degradation of benzene series VOCs.

6. The method for preparing an electrode according to claim 5, wherein: The mass volume ratio of the composite metal-based catalyst powder, water, ethanol and Nafion solution is (200-300) mg: (2-5) mL: (2-5) mL: (0.2-0.5) mL; The mass fraction of the Nafion solution is 5 to 7%.

7. Use of an electrode prepared by the preparation method according to any one of claims 5 to 6 in the degradation of benzene series VOCs in an electrocatalytic persulfate system.

8. The use according to claim 7, characterized in that The following steps are involved: Na2S2O8 aqueous solution was used as the electrolyte; The electrode for electrocatalytic degradation of benzene series VOCs prepared by the preparation method according to any one of claims 5 to 6 is used as an anode or a cathode; providing an additional electrode to act as a cathode or anode; Adding benzene VOCs into the electrolyte; The power supply is connected to the electrode for electrocatalytic degradation of benzene series VOCs and another electrode respectively, and the power supply is turned on to electrocatalytically degrade the benzene series VOCs.

9. The use according to claim 8, characterized in that Na2S2O8 is added to water to obtain a Na2S2O8 aqueous solution with a concentration of 0.5 to 1 mol / L, and the pH of the Na2S2O8 aqueous solution is adjusted to 9 to 11. The Na2S2O8 aqueous solution after pH adjustment is used as an electrolyte.

10. The use according to claim 8, characterized in that During electrolysis, the electrolyte temperature is controlled at 60-70°C and the current density is controlled at 160-170A / m 2 .

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