Tapered mesoporous gold nano-catalyst as well as preparation method and application thereof

Abstract

The invention discloses a conical mesoporous gold nano catalyst and a preparation method and application thereof, N-(2-mercaptoethyl)-N, N-dimethyldocosyl-1-ammonium chloride is used as a surfactant, chloroauric acid is used as a gold precursor, and co-assembly of the surfactant and the gold precursor is realized by Au-S covalent binding; and preparing the tapered mesoporous gold nano-catalyst with a multilevel structure by using L-ascorbic acid as a reducing agent through a one-step liquid phase method. The conical structure of the catalyst disclosed by the invention maximally exposes active sites of the catalyst and reduces the consumption of gold, and the high-curvature tip region has high electric field intensity, can promote reactant activation and electron transport, has an enrichment effect on ions beneficial to the reaction, is beneficial to directional proceeding of a target reaction, and has a good application prospect. Excellent catalytic activity, selectivity and stability are shown in an electro-catalysis styrene oxidation reaction. The catalyst is simple in preparation method, mild in reaction condition, good in product morphology, capable of being prepared in a large scale and suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a conical mesoporous gold nanocatalyst and a preparation method thereof, as well as the application of the catalyst in the electrocatalytic oxidation reaction of styrene. Background Art

[0002] Styrene oxide is an important synthetic intermediate for synthesizing perfumes, epoxy resins, plasticizers, drugs, sweeteners, and many fine chemicals. The traditional synthesis method is to oxidize styrene to styrene oxide with peroxyacid under acidic conditions, generating by-product carboxylic acid at the same time. This reaction has high requirements for equipment and high treatment costs for the generated acidic wastewater. Therefore, the electrochemically synthesis of styrene oxide has attracted extensive attention now. The electrochemically synthesis method directly drives the reaction through electron transfer, reducing acidic waste emissions and also having potential energy consumption optimization. Moreover, the electrochemical method also requires a suitable catalyst to improve the reaction rate, selectivity, and yield. Existing catalysts include: metal oxide catalysts (such as lead dioxide, ruthenium oxide), which have good stability, but compared with noble metals, the reaction rate is lower, they are easily corroded at high potentials, and the selectivity is poor; carbon-based materials (such as carbon nanotubes, graphene), which have a high specific surface area, good electrical conductivity, and low cost, but the catalytic activity is limited, and generally need to be compounded with other materials to improve performance; transition metal complexes or organic catalysts, which can adjust the catalytic performance through molecular design, but are easily decomposed or inactivated in the electrochemical environment, have poor stability, are sensitive to reaction conditions, and have limited application scope. Therefore, it is necessary to develop new highly active catalysts for the electrochemically synthesis of styrene epoxide.

[0003] Since the report of ordered mesoporous materials, mesoporous materials have received extensive attention. As the second-generation mesoporous materials, mesoporous metals with continuous crystalline skeletons have special application values in catalysis and electrocatalysis. Generally speaking, mesoporous metals have multiple advantages of "large nanoparticles" with fast electron transfer rate and high stability, and "small nanoparticles" with large surface area and many catalytic active sites, thus having excellent electrocatalytic performance. In particular, the crystal mesoporosity of mesoporous metals can optimize their electronic and spatial structures and provide a nanoscale confinement environment, promising to adjust their selectivity for a specific electrocatalysis.

[0004] Controlling the shape of nanocrystals is a simple and effective means to customize their properties and optimize their performance in various applications. The appropriate d-band electronic structure of noble metals can produce a moderate chemical adsorption strength for reactants, intermediates, and products in the catalytic process, which can improve selectivity and stability. In recent years, a large number of studies have shown that noble metal-based catalyst materials with diverse structures can be precisely prepared through morphology-controlled synthesis strategies (such as spheres, cubes, octahedrons, nanobowls, and nanorods). However, the scarcity of noble metals and their high prices still limit their large-scale industrial applications. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a conical mesoporous gold nanocatalyst, and provides a preparation method and a new use for this catalyst.

[0006] For the above purpose, the conical mesoporous gold nanocatalyst provided by the present invention is prepared by the following method:

[0007] Step 1: Heat and dissolve N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in deionized water, mix well and then cool to room temperature, and add chloroauric acid to obtain a reaction solution; the concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 0.7 - 3 mg / mL, and the concentration of chloroauric acid is 0.0005 - 0.02 mol / L.

[0008] Step 2: Let the reaction solution in Step 1 stand and react at room temperature for 30 - 60 minutes, then add L-ascorbic acid, and stir and reduce at room temperature for 2 - 6 hours. After the reaction is completed, centrifuge and wash with absolute ethanol, and the obtained solid is vacuum dried at 50 - 80 °C to obtain the conical mesoporous gold nanocatalyst.

[0009] Further, in the above Step 1, it is preferred to heat and dissolve N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in deionized water at 50 - 80 °C.

[0010] Further, in the above Step 1, it is preferred that the concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 0.75 - 1.5 mg / mL.

[0011] The structural formula of the above N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride is as follows:

[0012]

[0013] Further, in the above Step 1, it is preferred that the concentration of chloroauric acid in the reaction solution is 0.002 - 0.01 mol / L.

[0014] Further, in the above step 2, it is preferred that the addition amount of L-ascorbic acid is 15 to 80 times the mass of chloroauric acid in step 1.

[0015] Further, in the above step 2, it is more preferred that the addition amount of L-ascorbic acid is 20 to 30 times the mass of chloroauric acid in step 1.

[0016] Further, it is preferred that the apex angle of the cone of the conical mesoporous gold nanocatalyst is 30° to 120°.

[0017] Further, it is more preferred that the apex angle of the cone of the conical mesoporous gold nanocatalyst is 60° to 90°.

[0018] The present invention provides an application of the above-mentioned conical mesoporous gold nanocatalyst in the electrocatalytic oxidation reaction of styrene. The specific method is as follows: The conical mesoporous gold nanocatalyst and activated carbon (VulcanXC-72) are physically loaded according to a mass ratio of 2:1, and isopropanol: deionized water: naphthol with a volume ratio of 23:23:4 is used as a solvent to prepare a catalyst ink with a catalyst concentration of 5 mg / mL, and it is used as an anode catalyst and drop-coated on carbon paper. After drying, it is clamped on a clip electrode and used as a working electrode, with a saturated silver / silver chloride electrode as a reference electrode, a carbon rod electrode as a counter electrode, and an aqueous solution containing potassium sulfate and potassium bromide as an electrolyte. A dioxane solution of styrene is added to the electrolyte for the electrocatalytic oxidation reaction of styrene, and the reaction temperature is 25°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The present invention uses N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride as a surfactant and chloroauric acid as a gold precursor, and realizes the co-assembly of the surfactant-gold precursor by using the Au-S covalent bond combination; then, L-ascorbic acid is used as a reducing agent, and a conical mesoporous gold nanocatalyst with a hierarchical structure is prepared by a one-step liquid-phase method, and the surfactant is removed by centrifugal washing by using the solubility difference between the surfactant and the catalyst in ethanol. The present invention realizes the preparation of mesoporous nano-gold with a conical morphology by a simple one-step liquid-phase method. The preparation process is simple, the catalyst preparation cost is reduced, and the reaction conditions are mild, energy-saving and emission-reducing, the product morphology is well maintained, and it can be prepared in large quantities, etc., which is suitable for large-scale industrial production applications.

[0021] 2. In the conical mesoporous gold nanocatalyst of the present invention, on the one hand, the conical structure maximally exposes the active sites of the catalyst, greatly improving the utilization rate of gold and reducing the amount of gold used; the mesoporous structure enhances its resistance to Ostwald ripening and improves the stability of the catalytic reaction. On the other hand, the conical mesoporous structure has better molecular accessibility compared to the common spherical mesoporous structure, which is conducive to the diffusion and transportation of reactant molecules, intermediates and products, maximizing the utilization rate of the mesoporous channels; the conical structure has a tip effect, that is, the high-curvature tip region of the conical structure has a high electric field strength, which promotes the activation of reactants and electron transport and has an enrichment effect on ions favorable for the reaction, effectively improving the activity of the catalytic reaction.

[0022] 3. The conical mesoporous gold nanocatalyst of the present invention is used in the electrocatalytic oxidation reaction of styrene. The kinetic diffusion advantages of the synergistic conical structure and mesoporous structure, as well as the intrinsic oxidation activity of Au, exhibit excellent catalytic activity, selectivity and stability. Brief Description of the Drawings

[0023] Figure 1 It is a transmission electron microscope image of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° - 90° prepared in Example 1.

[0024] Figure 2 It is an X-ray diffraction pattern of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° - 90° prepared in Example 1.

[0025] Figure 3 It is a transmission electron microscope image of the conical mesoporous Au nanocatalyst with a cone apex angle of 30° - 60° prepared in Example 2 (a), the conical mesoporous Au nanocatalyst with a cone apex angle of 90° - 120° prepared in Example 2 (b), the flaky mesoporous Au nanocatalyst prepared in Comparative Example 1 (c), the conical Au nanocatalyst with a cone apex angle of 15° - 30° prepared in Comparative Example 2 (d), and the Au nanoparticle catalyst prepared in Comparative Example 3 (e).

[0026] Figure 4 It is a selectivity comparison diagram of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° - 90° prepared in Example 1, the flaky mesoporous Au nanocatalyst prepared in Comparative Example 1, the conical Au nanocatalyst with a cone apex angle of 15° - 30° prepared in Comparative Example 2, and the Au nanoparticle catalyst prepared in Comparative Example 3.

[0027] Figure 5 It is a yield comparison diagram of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° - 90° prepared in Example 1, the flaky mesoporous Au nanocatalyst prepared in Comparative Example 1, the conical Au nanocatalyst with a cone apex angle of 15° - 30° prepared in Comparative Example 2, and the Au nanoparticle catalyst prepared in Comparative Example 3.

[0028] Figure 6 It is the cyclic stability diagram of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° to 90° prepared in Example 1. Detailed implementation manners

[0029] The present invention will be further described in detail below with reference to the drawings and examples, but the protection scope of the present invention is not limited to these examples only.

[0030] Example 1

[0031] Preparation of the conical mesoporous Au nanocatalyst with a cone apex angle of 60° to 90°

[0032] Step 1: At 75 °C, add 20 mg of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride to 20 mL of deionized water, stir until the solid is completely dissolved, then cool to room temperature, and add 6.0 mL of 0.010 mol / L chloroauric acid aqueous solution to obtain a reaction solution; the concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 0.77 mg / mL, and the concentration of chloroauric acid is 0.0023 mol / L.

[0033] Step 2: Let the reaction solution stand at room temperature (25 °C) for 30 minutes, then add 10 mL of 0.053 g / mL L-ascorbic acid. The addition amount of L-ascorbic acid is 26 times the mass of chloroauric acid, and stir and reduce at room temperature for 2 hours; after the reaction is completed, centrifuge and wash 6 times with absolute ethanol to remove N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride. The obtained solid is dried in a vacuum drying oven at 60 °C for 2 hours to obtain the conical mesoporous Au nanocatalyst. It can be Figure 1 seen that the cone apex angle of the obtained catalyst is 60° to 90°, the conical mesoporous structure size is relatively uniform and monodispersed. And the high-magnification transmission electron microscope image shows that the surface of the conical mesoporous Au has a rich mesoporous channel structure, and the mesoporous channels are branched and radiate towards the edge of the nanocone. The crystal structure of the mesoporous Au catalyst with a cone apex angle of 60° to 90° is further characterized. From Figure 2 the powder X-ray diffraction pattern, it can be seen that the catalyst shows PXRD signals corresponding to the face-centered cubic (fcc) crystal.

[0034] Example 2

[0035] Preparation of the conical mesoporous Au nanocatalyst with a cone apex angle of 30° to 60°

[0036] Step 1: At 75 °C, add 60 mg of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride to 20 mL of deionized water. Stir until the solid is completely dissolved, then cool to room temperature. Add 2.0 mL of 0.010 mol / L chloroauric acid aqueous solution to obtain a reaction solution. The concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 2.72 mg / mL, and the concentration of chloroauric acid is 0.0009 mol / L.

[0037] Step 2: Let the reaction solution stand at room temperature (25 °C) for 30 minutes, then add 10.2 mL of 0.025 g / mL L-ascorbic acid. The addition amount of L-ascorbic acid is 38 times the mass of chloroauric acid. Stir and carry out a reduction reaction at room temperature for 2 hours. After the reaction is completed, centrifuge and wash with absolute ethanol 6 times to remove N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride. The obtained solid is dried in a vacuum drying oven at 60 °C for 2 hours to obtain a conical mesoporous Au nanocatalyst. As shown in Figure 3 (a), the obtained catalyst is conical, the cone apex angle is 30° - 60°, and it diffuses in a branched shape towards the conical edge.

[0038] Example 3

[0039] Preparation of Conical Mesoporous Au Nanocatalyst with Cone Apex Angle of 90° - 120°

[0040] Step 1: At 75 °C, add 20 mg of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride to 20 mL of deionized water. Stir until the solid is completely dissolved, then cool to room temperature. Add 8.0 mL of 0.010 mol / L chloroauric acid aqueous solution to obtain a reaction solution. The concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 0.7 mg / mL, and the concentration of chloroauric acid is 0.003 mol / L.

[0041] Step 2: Let the reaction solution stand at room temperature (25 °C) for 30 minutes, then add 10 mL of 0.053 g / mL L-ascorbic acid. The addition amount of L-ascorbic acid is 19 times the mass of chloroauric acid. Stir and carry out a reduction reaction at room temperature for 2 hours. After the reaction is completed, centrifuge and wash with absolute ethanol 6 times to remove N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride. The obtained solid is dried in a vacuum drying oven at 60 °C for 2 hours to obtain a conical mesoporous Au nanocatalyst. As shown in Figure 3 (b), the obtained catalyst is conical, the cone apex angle is 90° - 120°, and it diffuses in a branched shape towards the conical edge.

[0042] Comparative Example 1

[0043] Preparation of Flaky Mesoporous Au Nanocatalyst

[0044] Step 1: At 75 °C, add 15 mg of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride to 20 mL of deionized water. Stir until the solid is completely dissolved, then cool to room temperature. Add 2.0 mL of 0.010 mol / L chloroauric acid aqueous solution to obtain a reaction solution. The concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 0.68 mg / mL, and the concentration of chloroauric acid is 0.0009 mol / L.

[0045] Step 2: Let the reaction solution stand at room temperature (25 °C) for 30 minutes, then add 10 mL of 0.053 g / mL L-ascorbic acid. The addition amount of L-ascorbic acid is 78 times the mass of chloroauric acid. Stir and reduce at room temperature for 2 hours. After the reaction, centrifuge and wash with absolute ethanol 6 times to remove N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride. The obtained solid is dried in a vacuum drying oven at 60 °C for 2 hours to obtain a flaky mesoporous Au nanocatalyst. As shown in Figure 3 (c), the obtained catalyst is in a flaky structure and is branched.

[0046] Comparative Example 2

[0047] Preparation of Conical Mesoporous Au Nanocatalyst with a Cone Apex Angle of 15° - 30°

[0048] Step 1: At 75 °C, add 100 mg of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride to 20 mL of deionized water. Stir until the solid is completely dissolved, then cool to room temperature. Add 2.0 mL of 0.010 mol / L chloroauric acid aqueous solution to obtain a reaction solution. The concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution is 4.55 mg / mL, and the concentration of chloroauric acid is 0.0009 mol / L.

[0049] Step 2: Let the reaction solution stand at room temperature (25 °C) for 30 minutes, then add 5 mL of 0.053 g / mL L-ascorbic acid. The addition amount of L-ascorbic acid is 78 times the mass of chloroauric acid. Stir and reduce at room temperature for 2 hours. After the reaction, centrifuge and wash with absolute ethanol 6 times to remove N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride. The obtained solid is dried in a vacuum drying oven at 60 °C for 2 hours to obtain a conical mesoporous Au nanocatalyst. As shown in Figure 3 (d), the obtained catalyst is conical, and the cone apex angle is 15° - 30°.

[0050] Comparative Example 3

[0051] Preparation of Au Nanoparticle Catalyst

[0052] At room temperature, 4.06 mL of 0.01 mol / L chloroauric acid solution was taken in a beaker, and 40 mg of Vulcan XC-72 was added thereto. The mixture was ultrasonicated to be uniform, and the above solution was slowly stirred to dryness at room temperature. The obtained solid powder was poured into 64 mL of freshly prepared 10 mmol / L aqueous sodium borohydride solution. After stirring for 2 hours, it was centrifugally washed twice with deionized water. The obtained solid was dried in a vacuum drying oven at 60 °C for 2 hours to obtain the Au nanoparticle catalyst. As can be seen from Figure 3 (e), the obtained catalyst is in granular form.

[0053] Comparing the results of Example 2 above with those of Comparative Example 1 and Comparative Example 2, it can be seen that the concentration of N-(2-mercaptoethyl)-N,N-dimethyldocosyl-1-ammonium chloride in the reaction solution has a significant effect on the morphology of the obtained catalyst. If the concentration is too high or too low, the tapered mesoporous Au nanocatalyst cannot be obtained.

[0054] Example 4

[0055] Application of the Tapered Mesoporous Gold Nanocatalyst of the Present Invention in the Electrocatalytic Oxidation Reaction of Styrene

[0056] 2.0 mg of the tapered mesoporous Au nanocatalyst prepared in Example 1 was weighed, mixed and stirred with 1.0 mg of Vulcan XC-72 carbon black and 2.0 mL of ethanol for 3 hours, washed and dried with ethanol, and then 185 μL of isopropanol, 185 μL of deionized water and 30 μL of naphthol were added. After ultrasonication in an ultrasonic cleaner for 15 minutes, a 5.0 mg / mL tapered mesoporous Au nanocatalyst ink was obtained. 80 μL of the catalyst ink was uniformly pipetted and dropped onto a 2.0 cm × 1.0 cm carbon paper, and the dropping area was 1.0 cm × 1.0 cm, so that the loading amount of the catalyst was 0.40 mg, and it was dried at room temperature. After drying, it was clamped on a clip electrode and used as a working electrode, with a saturated silver / silver chloride electrode as the reference electrode and a 6.0 mm × 6.0 cm carbon rod electrode as the counter electrode. The electrolytic cell used was a common three-electrode electrolytic cell. An aqueous solution containing 0.075 mol / L potassium sulfate and 0.10 mol / L potassium bromide with a volume of 30 mL was used as the electrolyte, and a mixed solution of 300 μL of styrene and 3 mL of dioxane was added to the electrolyte. The electrocatalytic oxidation reaction of styrene was carried out using an electrochemical workstation (CHI660E). The reaction test temperature was 25 °C, and the temperature was controlled by a water bath.

[0057] In the electrocatalytic styrene oxidation reaction test, cyclic voltammetry (CV) was used to record the current density (j) within the applied voltage range, which can be used to characterize the electrochemical behavior under this voltage range. Among them, the CV scanning rate was 50 mV / s, the scanning voltage range was -0.50 to 1.7 V relative to silver / silver chloride, and the reaction temperature was 25 °C; the constant voltage method can be used to record the chronoamperometry (i-t) curve under the applied potential.

[0058] The calculation method of selectivity (Sel.) is as follows: Nuclear magnetic resonance hydrogen spectroscopy ( 1 H NMR) was used to detect the reaction products. Tetramethylsilane (TMS) was used as an internal standard for normalization. The areas corresponding to the characteristic hydrogens of each product (styrene oxide, phenylacetaldehyde, acetophenone, benzaldehyde, formaldehyde, benzoic acid) were obtained, and the concentrations corresponding to each product were calculated as c 1 , c 2 , c 3 , c 4 , c 5 , c 6 (corresponding to the above products respectively). The formula for calculating selectivity is:

[0059]

[0060] The calculation method of the yield of styrene oxide is as follows: Nuclear magnetic resonance hydrogen spectroscopy ( 1 HNMR) was used to detect the reaction products. Tetramethylsilane (TMS) was used as an internal standard for normalization. The area S of the characteristic hydrogen corresponding to styrene oxide was obtained. The formula for calculating the yield is:

[0061]

[0062] At the same time, the catalytic properties of the flaky mesoporous Au nanocatalyst prepared in Comparative Example 1, the conical Au nanocatalyst with a cone apex angle of 0° to 15° prepared in Comparative Example 2, and the Au nanoparticle catalyst prepared in Comparative Example 3 were compared.

[0063] Figure 4 It was shown that compared with Comparative Example 1 and Comparative Example 3, the catalyst prepared in Example 1 had higher selectivity for the formation of styrene oxide in an aqueous solution containing 0.075 mol / L potassium sulfate and 0.1 mol / L potassium bromide, indicating that the catalyst of Example 1 had high selectivity for the oxidation of styrene.

[0064] Figure 5It is shown that, compared with Comparative Example 1, Comparative Example 2 and Comparative Example 3, the catalyst prepared in Example 1 has a higher yield of styrene oxide in an aqueous solution containing 0.075 mol / L potassium sulfate and 0.1 mol / L potassium bromide, indicating that the catalyst of Example 1 has high activity for the epoxidation of styrene. It shows that the nanocone structure of the catalyst has high activity and selectivity for the epoxidation of styrene.

[0065] Based on the high selectivity and activity exhibited by the tapered mesoporous Au nanocatalyst of the present invention, the stability of the catalyst during the electrocatalytic oxidation of styrene was further investigated. Figure 6 It is shown that within 6 cycles, the selectivity and yield of the electrooxidation of styrene catalyzed by the catalyst prepared in Example 1 remain almost unchanged.

Claims

1. A method for preparing a conical mesoporous gold nanocatalyst, characterized in that: The method consists of the following steps: Step 1: dissolving N-(2-mercaptoethyl)-N,N-dimethylbehenyl-1-ammonium chloride in deionized water by heating, mixing and cooling to room temperature, adding chloroauric acid to obtain a reaction solution; the concentration of N-(2-mercaptoethyl)-N,N-dimethylbehenyl-1-ammonium chloride in the reaction solution is 0.7-3 mg / mL, and the concentration of chloroauric acid is 0.0005-0.02 mol / L; Step 2: The reaction solution of step 1 is allowed to stand at room temperature for 30 to 60 minutes, then L-ascorbic acid is added, and the reduction reaction is stirred at room temperature for 2 to 6 hours. After the reaction is completed, it is washed by centrifugation with anhydrous ethanol, and the obtained solid is vacuum dried at 50 to 80° C. to obtain a conical mesoporous gold nanocatalyst.

2. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: In step 1, N-(2-mercaptoethyl)-N,N-dimethyldodecyl-1-ammonium chloride is heated at 50-80° C. and dissolved in deionized water.

3. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: In step 1, the concentration of N-(2-mercaptoethyl)-N,N-dimethyldodecyl-1-ammonium chloride in the reaction solution is 0.75 to 1.5 mg / mL.

4. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: In step 1, the concentration of chloroauric acid in the reaction solution is 0.002-0.01 mol / L.

5. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: In step 2, the amount of L-ascorbic acid added is 15 to 80 times the mass of chloroauric acid in step 1.

6. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: In step 2, the amount of L-ascorbic acid added is 20 to 30 times the mass of chloroauric acid in step 1.

7. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: The cone apex angle of the cone in the catalyst is 30° to 120°.

8. The method for preparing the conical mesoporous gold nanocatalyst according to claim 1, characterized in that: The cone apex angle of the cone in the catalyst is 60° to 90°.

9. The conical mesoporous gold nanocatalyst obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the conical mesoporous gold nanocatalyst according to claim 9 in the electrocatalytic oxidation reaction of styrene.

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