Gold-based nano-catalyst as well as preparation method and application thereof

Abstract

The invention discloses a gold-based nano-catalyst as well as a preparation method and application thereof, and belongs to the technical field of co-production hydrogen production through biomass electrochemical conversion. According to the preparation method disclosed by the invention, a gold precursor, an iron precursor, a surfactant and a reducing solvent are combined with a carbon carrier solution to serve as a preparation raw material, Au-FeOx heterojunction nano-particles are formed through metal oxide modified nano-gold particles, and then the Au-FeOx heterojunction nano-particles are loaded on the surface of the carrier to form the catalyst. The gold-based nano-catalyst prepared by the method is high in glycerol adsorption capacity and reaction intermediate adsorption and dissociation capacity, and good in catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass electrochemical conversion and co-production of hydrogen, and specifically relates to a gold-based nanocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Biodiesel is a clean and renewable energy source. The energy crisis has promoted the vigorous development of biodiesel, but the production of biodiesel will generate a large amount of glycerol by-products. Glycerol is one of the most important biomass platform compounds, and value-added chemicals such as glyceraldehyde, dihydroxyacetone, glyceric acid, etc. are produced through different conversion pathways such as bioconversion, oxidation, hydrogenolysis, etc. Among them, the market value of glyceric acid is much higher than that of glycerol, and it is widely used in the cosmetics, food, and pharmaceutical industries. However, the reaction of thermal catalytic oxidation of glycerol to glyceric acid usually needs to be carried out under high temperature and high pressure conditions, and a large amount of oxidant needs to be added to the reaction. In contrast, the reaction of electrocatalytic oxidation of glycerol can be carried out under normal temperature and pressure conditions, and at the same time, the production of H2 can be realized at the cathode. With the sustainable development of electric power resources, the cost of electric power resources has gradually decreased, and the electrocatalytic oxidation of glycerol to glyceric acid has gradually become a research hotspot for researchers.

[0003] Au-based catalysts usually exhibit excellent catalytic activity and selectivity for glycerol. In addition, compared with Pt and Pd-based catalysts, Au-based catalysts are not easily poisoned and inactivated due to over-oxidation, and have high stability and reusability. However, pure gold catalysts exhibit very low catalytic activity, far from meeting the requirements of industrial production. Therefore, in the reaction process of electrocatalytic oxidation of glycerol to lactic acid, the development of supported gold-based catalysts with high activity and high selectivity is the focus of this research direction. Therefore, it is crucial to develop a catalyst that can improve the stability and high selectivity of Au species. Summary of the Invention

[0004] The purpose of the present invention is to provide a gold-based nanocatalyst, a preparation method thereof, and an application thereof, so as to solve the technical problem that the existing catalysts have poor catalytic activity.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions: The present invention discloses a preparation method of a gold-based nanocatalyst, comprising the following steps: Mix a gold precursor, an iron precursor, a surfactant, and a reducing solvent, and then perform ultrasonic and stirring treatments in sequence to obtain a precursor solution; Stir and heat the precursor solution in an inert atmosphere, cool and wash it, and then disperse it in ethanol to obtain a mixed solution; Ultrasonically mix the mixed solution with a carbon support solution, and then perform washing and drying treatments in sequence to obtain a gold-based nanocatalyst.

[0006] Furthermore, the ultrasonic time of the precursor solution is 50 - 70 min; the stirring time is 160 - 500 min, and the rotation speed is 300 - 500 r / min.

[0007] Furthermore, the gold precursor is an inorganic compound containing gold; the inorganic compound containing gold is one of chloroauric acid, potassium chloroaurate, and sodium chloroaurate.

[0008] Furthermore, the iron precursor is one of ferric chloride, ferrous chloride, iron(III) acetylacetonate, and iron(II) acetylacetonate; The surfactant is one or both of cetyltrimethylammonium bromide and polyvinylpyrrolidone; The reducing solvent is one of ethylene glycol, oleylamine, and isopropyl alcohol.

[0009] Furthermore, the dosage ratio of the gold precursor, iron precursor, surfactant, and reducing solvent is (0.5 - 1.5) mmol : (0.02 - 0.16) mmol : (0.1 - 0.5) mmol; (5 - 25) mL.

[0010] Furthermore, the inert atmosphere is N₂ atmosphere in a closed space; the stirring and heating are carried out under the conditions of 100 - 150 °C and 1000 - 1400 r / min for 100 - 140 min; the volume ratio of the reducing solvent to ethanol is (5 - 25) : 20.

[0011] Furthermore, the carbon support solution is obtained by ultrasonically dispersing the activated carbon support in ethanol, and the ultrasonic dispersion is carried out at 100 Hz for 5 - 10 min; the dosage ratio of the activated carbon support to ethanol is 36.7 mg - 20 mL.

[0012] Furthermore, the volume dosage ratio of the mixed solution to the carbon support solution is 1 : 1; The washing is carried out with cyclohexane and ethanol with a volume ratio of 1:9; The ultrasonic mixing time of the mixed solution and the carbon support solution is 40 - 60 min; The temperature of the drying treatment is 30 - 60 °C.

[0013] The present invention also discloses a gold-based nanocatalyst prepared by the above preparation method. The gold-based nanocatalyst has Au-FeO x heterojunction nanoparticles formed by Fe oxides anchored and modified on gold nanoparticles, and the Au-FeO x heterojunction nanoparticles are loaded on a carbon support to form a microstructure; The Au-FeO x heterojunction nanoparticles have a particle size of 5 - 20 nm; The content of gold in the gold-based nanocatalyst is 0.15wt% to 0.35wt%, and the molar amount of iron is one-fourth of that of gold.

[0014] The present invention also discloses the application of the above gold-based nanocatalyst in the reaction of electro-oxidizing glycerol to glyceric acid.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a preparation method of a gold-based nanocatalyst. By using a gold precursor, an iron precursor, a surfactant, a reducing solvent and a carbon support solution as raw materials for preparation, Au-FeO x heterojunction nanoparticles are formed through metal oxide-modified gold nanoparticles. Subsequently, the Au-FeO x heterojunction nanoparticles are loaded on the surface of the support to form a catalyst. Since the heterojunction is the Au-FeO x phase formed between the Au phase and the FeO x phase, there are a large number of defects and lattice distortions at the interface. The bonding interaction between Au and FeO x interfaces can improve the electron transfer rate. The lattice strain caused by different chemical compositions and crystal structures in the heterostructure affects the adsorption energy of the active site for the substrate, optimizes the glycerol oxidation reaction path. The different energy band arrangements of the Au and FeO x phases lead to charge transfer at the interface, which is beneficial to the surface electron modulation of the heterostructure. The FeO x phase is anchored on the surface of the Au particles, optimizing the active sites on the surface of the Au particles to form Au-FeO x heterojunction, affecting the substrate adsorption configuration, optimizing the glycerol oxidation path, improving the adsorption ability of the catalyst for glycerol and the adsorption and dissociation ability for reaction intermediates, and thus improving the catalytic activity.

[0016] Furthermore, the preparation method of the present invention reduces the usage amount of precious metal gold compared with gold catalysts with the same performance, saves costs. At the same time, the preparation method of the nano gold-based catalyst in the present invention adopts a wet chemical method, and the safety factor of the experimental operation process is high and the repeatability is strong.

[0017] Furthermore, the FeO x modified gold nanoparticles Au-FeO x in the nano gold-based catalyst of the present invention change the substrate adsorption configuration and improve the selectivity of the catalytic glycerol electrocatalytic oxidation reaction to produce lactic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Au-FeO prepared in Example 4 of the present invention xTransmission electron microscopy image of the Au-FeO Figure 2 / C (molar ratio of gold to iron is 4:1) catalyst prepared in Example 4 of the present invention; x Mapping image of the Au-FeO / C (molar ratio of gold to iron is 4:1) catalyst; where: a) is the distribution map of Au element; b) is the distribution map of Fe element; c) is the distribution map of C element; d) is the distribution map of O element; Figure 3 XRD pattern of the Au-FeO x / C (molar ratio of gold to iron is 4:1) prepared in Example 4 of the present invention; Figure 4 Catalytic performance result graph of the catalysts prepared in Examples 1-4; Figure 5 Catalytic performance result graph of the catalysts prepared in Examples 4-7 and Comparative Examples 1-2. Detailed implementation manners

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0021] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0022] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0023] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0024] The present invention provides a preparation method of a gold-based nanocatalyst, comprising the following steps: After mixing a gold precursor, an iron precursor, a surfactant and a reducing solvent, ultrasonic treatment and stirring treatment are sequentially carried out to obtain a precursor solution, denoted as A1; Transfer the precursor solution A1 to a thick-walled pressure-resistant bottle, fill N2 in a closed container, then heat with stirring at a certain temperature, and after cooling and washing, disperse it in ethanol for use to obtain a mixed solution, denoted as A2; Ultrasonically mix a high specific surface area activated carbon carrier with ethanol to obtain a carbon carrier solution, denoted as A3; Ultrasonically mix A2 and A3 evenly to obtain a solution, denoted as A4; Finally, wash and dry the solution A4 to obtain the gold-based nanocatalyst.

[0025] Preferably, the gold precursor refers to an inorganic compound containing gold.

[0026] More preferably, the gold precursor includes chloroauric acid, potassium chloroaurate, sodium chloroaurate, and preferably chloroauric acid.

[0027] Preferably, the iron precursor includes any one of ferric chloride, ferrous chloride, iron acetylacetonate, ferrous acetylacetonate, and more preferably ferrous acetylacetonate.

[0028] Preferably, the reducing solvent includes any one of ethylene glycol, oleylamine, isopropyl alcohol; more preferably oleylamine.

[0029] Preferably, the carbon carrier includes high specific surface area activated carbon after ball milling, and is not limited thereto.

[0030] Preferably, the dosage ratio of the gold precursor, the iron precursor, the surfactant and the reducing solvent is (0.5~1.5) mmol: (0.02~0.16) mmol: (0.1~0.5) mmol; (5~25) mL.

[0031] Preferably, the solution A1 and A2 are stirred at 500 r / min and 1400 r / min for 180~200 min and 120~140 min respectively.

[0032] Preferably, the washing liquid used for the washing treatment includes cyclohexane and ethanol.

[0033] Preferably, the solution A1, A3, and A4 are ultrasonically treated at 100 Hz for 45~65 min, 5~10 min, and 50~70 min respectively.

[0034] Preferably, the temperature of the drying treatment is 30~60 °C.

[0035] In some preferred embodiments, the preparation method of the gold-based catalyst specifically includes: (1) Disperse chloroauric acid trihydrate, cetyltrimethylammonium bromide, and ferrous acetylacetonate into a certain amount of oleylamine. After a period of ultrasonic treatment and stirring, the precursor is evenly dispersed in oleylamine to form a precursor solution A1; (2) Transfer the precursor solution A1 to a thick-walled pressure-resistant bottle, evacuate and then fill with N2. Heat for a period of time under N2 protection, cool, and wash with cyclohexane and ethanol. After washing, the nanoparticles are dispersed in ethanol and ultrasonically homogenized to form solution A2; (3) Mix a certain amount of high-surface-area activated carbon and ethanol, and ultrasonically homogenize to form a suspension A3; (4) Ultrasonically mix solution A2 and solution A3 to form solution A4; (5) Wash the reaction product A4 with cyclohexane and ethanol, and dry overnight under vacuum to obtain the catalyst.

[0036] Furthermore, in step (2), the mass of chloroauric acid and the carbon support are added such that the gold loading is controlled at 0.15 wt% - 0.4 wt%; the dosage ratio of the added chloroauric acid to ferrous acetylacetonate is 1 mol: 0.01 - 0.16 mol: 5 - 25 mol.

[0037] Furthermore, in steps (1) and (3), the ultrasonic treatment is carried out at 100 Hz for 50 - 60 min and 5 - 10 min respectively. Furthermore, in step (2), the heating is carried out under N2 protection, and stirring is carried out at 1400 r while heating.

[0038] Furthermore, in steps (1) and (2), the stirring is carried out at 500 r / min and 1400 r / min for 180 - 200 min and 120 - 140 min respectively.

[0039] The present invention also discloses a gold-based nanocatalyst prepared by the above preparation method, which is an Au-FeO x heterojunction nanoparticle formed by modified gold nanoparticles with a transition metal oxide FeO x supported on a high-surface-area activated carbon carrier, the Au-FeO x / C catalyst, including: a large number of defects and dislocations are formed between the Au and FeO x two phases. The defects at the interface will form impurity energy levels in the electronic structure, thus affecting the conductive performance of the heterojunction; the lattice strain caused by different chemical compositions and crystal structures in the heterostructure affects the adsorption energy of the active sites for the substrate, improving the catalytic activity of the gold-based catalyst; electron interaction: Au and FeO xThe different energy band alignments of the two phases result in charge transfer at the interface, which is beneficial for the surface electron modulation of the heterostructure.

[0040] The nano-gold-based catalyst in the present invention is a supported catalyst, the carrier is activated carbon with a high specific surface area, and the active component is the transition metal oxide FeO x modified nano-gold particles, which are distributed on the activated carbon carrier with a high specific surface area after ball milling (denoted as: Au-FeO x / C), and the metal oxide FeO x modified nano-gold particles form heterojunctions with each other and are distributed on the activated carbon carrier with a high specific surface area; due to the different reduction potentials of gold and iron, gold is easily reduced to the metallic state by oleylamine and preferentially nucleates in the solvent; in addition, at the interface between the metallic gold and the metal oxide FeO x the introduction of FeO x changes the adsorption configuration and electron transport ability of the catalyst substrate.

[0041] Preferably, the particle size of the gold nanoparticles is less than 15 nm.

[0042] Preferably, the gold content in the nano-gold-based catalyst is 0.2 wt% - 0.3 wt%.

[0043] Preferably, the iron content in the nano-gold-based catalyst is 0.01 wt% - 0.1 wt%.

[0044] Preferably, the gold-based nanoparticles are the nano-gold particles modified by the transition metal oxide FeO x Au-FeO x and form a Au-FeO x heterostructure, and is not limited thereto.

[0045] In some preferred embodiments, the preparation method specifically includes: (1) Ultrasonically mixing and stirring the gold precursor, iron precursor, surfactant, and reducing solvent to form a precursor solution A1; (2) Heating and keeping the precursor solution A1 warm for a period of time while stirring, washing with an organic solvent after cooling, and dispersing in ethanol to form a solution A2; (3) Adding a certain amount of high-surface-area activated carbon carrier to ethanol and ultrasonically forming a solution A3; (4) Ultrasonically mixing the solutions A2 and A3 to form a fourth solution A4; And, washing and overnight drying the solution A4 to finally obtain the nano-gold-based catalyst.

[0046] Furthermore, the gold precursor refers to an inorganic compound containing gold.

[0047] Further, the gold precursor includes chloroauric acid, potassium chloroaurate, sodium chloroaurate, preferably chloroauric acid.

[0048] Further, the iron precursor includes any one of ferric chloride, ferrous chloride, iron acetylacetonate, ferrous acetylacetonate, preferably ferrous acetylacetonate.

[0049] Further, the reducing solvent includes any one of ethylene glycol, oleylamine, isopropyl alcohol; preferably oleylamine.

[0050] Further, the carbon support includes high specific surface area activated carbon after ball milling, and is not limited thereto.

[0051] Further, the amounts of the gold precursor, iron precursor, surfactant, and reducing solvent are about 0.5 - 1.5 mmol: 0.02 - 0.16 mmol: 0.1 - 0.5 mmol: 5 - 25 mL (purity greater than 99%).

[0052] Further, the solutions A1 and A2 are stirred at 500 r / min for 180 - 200 min and 1400 min for 120 - 140 min.

[0053] Further, the washing liquid used for the washing treatment includes cyclohexane and ethanol.

[0054] Further, the solutions A1, A3, and A4 are ultrasonicated at 100 Hz for 50 - 60 min, 5 - 10 min, and 50 - 60 min.

[0055] Further, the temperature of the drying treatment is 30 - 60 °C.

[0056] In some preferred embodiments, the preparation method of the gold-based catalyst specifically includes: (1) Disperse chloroauric acid trihydrate, cetyltrimethylammonium bromide, and ferrous acetylacetonate into a certain amount of oleylamine. After a period of ultrasonic treatment and stirring, the precursors are evenly dispersed in oleylamine to form a precursor solution A1; (2) Transfer the precursor solution A1 to a thick-walled pressure-resistant bottle, evacuate and then fill with N2. Heat for a period of time under N2 protection, cool, wash with cyclohexane and ethanol, and add ethanol and ultrasonicate evenly to form a solution A2; (3) Mix a certain amount of high surface area activated carbon and ethanol, and ultrasonicate evenly to form a suspension A3; (4) Ultrasonically mix the solution A2 and the suspension A3 to form a solution A4; (5) Wash the reaction product A4 with cyclohexane and ethanol, and dry overnight under vacuum to obtain the catalyst.

[0057] Furthermore, the mass of chloroauric acid and carbon support added in step (2) is such that the gold loading is controlled at 0.15 wt% to 0.4 wt%; the dosage ratio of the added chloroauric acid to ferrous acetylacetonate is 1 mol: 0.01 - 0.16 mol: 5 - 25 mol.

[0058] Furthermore, in steps (1) and (3), the ultrasonic treatments are carried out at 100 Hz for 120 - 140 min and 5 - 10 min respectively.

[0059] Furthermore, in step (2), the heating is carried out under N2 protection and stirring is carried out at 1400 r while heating.

[0060] Furthermore, in steps (1) and (2), the stirring is carried out at 500 r / min and 1400 r / min for 180 - 200 min and 120 - 140 min respectively.

[0061] Furthermore, the heating temperature in step (2) is 100 - 120 °C.

[0062] Furthermore, the drying temperature in step (5) is 30 - 60 °C.

[0063] Furthermore, the volume ratio of cyclohexane to ethanol in the washing liquid in steps (2) and (5) is 1:9.

[0064] The preparation method of the nano - gold - based catalyst in the present invention adopts a wet - chemical method, which is safe, easy to operate and reproducible.

[0065] Another aspect of the embodiments of the present invention also provides the use of the aforementioned nano - gold - based catalyst in the electro - catalytic highly selective preparation of glyceric acid from glycerol.

[0066] In the present invention, the catalytic test is carried out to evaluate the efficacy of the catalyst, and the reaction is carried out at normal temperature and normal pressure.

[0067] The design of the nano - gold - based catalyst in the present invention will be further improved in the highly selective catalytic conversion of glycerol to glyceric acid by gold - based catalysts. This is because there is a significant synergistic effect between Au particles and metal cations in metal oxide FeOx, and the influence of the heterojunction interface between Au and FeOx on the catalytic effect can be controlled by changing the input amounts of Au and Fe. Through the modification of the support by the metal oxide, the nano - gold - based catalyst can be effectively regulated to have excellent activity and high selectivity in the selective catalytic conversion of glycerol to lactic acid.

[0068] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0069] In the catalyst test of the embodiments involved in the present invention, a mixed solution of 1M KOH and 0.5M glycerol was used as the reaction solvent. Glycerol is a typical polyol compound. However, the application field of this catalyst can be targeted at the selective oxidation of other alcohol compounds. In the test, the reaction conditions adopted were set as: normal temperature and normal pressure; the metal loading of the catalyst was 30wt%; a small amount of metal oxide FeO x Effectively improved the catalytic activity and selectivity of the gold-based catalyst, and improved the utilization rate of metal atoms in the catalyst.

[0070] The calculation method for the selectivity of glycerol selective oxidation to glyceric acid: Analyze the products by liquid chromatography, and the lactic acid content in the products is the selectivity.

[0071] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0072] Example 1 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.02 mmol of neodymium acetylacetonate into 10 mL of oleylamine (oleylamine purity > 99%), ultrasonicate for 60 min under the condition of 100 Hz, and stir for 180 min under the condition of 500 r / min to make the precursor evenly dispersed in oleylamine to form a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a closed environment. After evacuating the air, fill it with N2, and heat it for a certain period under the protection of N2. The heating temperature is 120 °C. The heating jacket takes 8 min to heat up from room temperature to 120 °C. The stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution (the particles washed well with cyclohexane and ethanol are on the centrifuge tube wall, and disperse them evenly with 20 ml of ethanol by ultrasonication), denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min under the condition of 100 Hz to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then wash it twice with ethanol, and dry it overnight in a vacuum at 60 °C for 10 h to obtain a catalyst, denoted as Au4-(NdO x )1 / C (the molar ratio of Au to Nd = 4:1); Subsequently, evaluate the catalytic oxidation of glycerol to glyceric acid by the catalyst.

[0073] Example 2 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.02 mmol of tin acetylacetonate into 10 mL of oleylamine (oleylamine purity is greater than 99%), ultrasonicate for 60 min under the condition of 100 Hz, and stir at 500 r / min for 180 min to make the precursor disperse evenly in oleylamine to form a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a closed environment. After evacuating the air, fill it with N2, and heat it for a certain period under the protection of N2. The heating temperature is 120 °C. The heating jacket takes 8 min to heat up from room temperature to 120 °C. The stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash the solution A4 once with cyclohexane and ethanol and then twice with ethanol, and dry it overnight under vacuum at 60 °C for 10 h to obtain a catalyst, denoted as Au4-(SnO x )1 / C (the molar ratio of Au to Sn = 4:1); Subsequently, the catalytic glycerol oxidation to glyceric acid of the catalyst was evaluated.

[0074] Example 3 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.02 mmol of cerium acetate into 10 mL of oleylamine (oleylamine purity > 99%), ultrasonicate for 60 min under the condition of 100 Hz, and stir for 180 min under the condition of 500 r / min to make the precursor evenly dispersed in oleylamine, forming a precursor solution, denoted as A1; Step 2: Transfer A1 to a thick-walled pressure-resistant bottle, keep the container in a closed environment, evacuate and then fill with N2, heat for a period of time under N2 protection, the heating temperature is 120 °C, the heating jacket takes 8 min to rise from room temperature to 120 °C, the stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution, denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form a solution A4; Step 5: Wash the solution A4 once with cyclohexane and ethanol and then twice with ethanol, and dry it overnight under vacuum at 60 °C for 10 h to obtain a catalyst, denoted as Au4-(CeO x )1 / C (the molar ratio of Au to Ce = 4:1); Subsequently, the catalytic glycerol oxidation to glyceric acid of the catalyst was evaluated.

[0075] Example 4 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.02 mmol of ferrous acetylacetonate into 10 mL of oleylamine (oleylamine purity > 99%), ultrasonicate for 60 min under the condition of 100 Hz, and stir for 180 min under the condition of 500 r / min to make the precursor evenly dispersed in oleylamine, forming a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a closed environment. After evacuating the air, fill it with N2, and heat it for a certain period under the protection of N2. The heating temperature is 120 °C. The heating jacket takes 8 min to heat up from room temperature to 120 °C. The stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then wash it twice with ethanol, and dry it under vacuum at 60 °C overnight for 10 h to obtain a catalyst, denoted as Au4-(FeO x )1 / C (the molar ratio of Au to Fe = 4:1); Subsequently, evaluate the catalytic performance of the catalyst for the oxidation of glycerol to glyceric acid.

[0076] Example 5 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.08 mmol of acetylacetone into 10 mL of oleylamine (the purity of oleylamine is greater than 99%). Ultrasonicate it for 60 min under the condition of 100 Hz and stir it for 180 min under the condition of 500 r / min in sequence to make the precursor disperse evenly in oleylamine to form a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a closed environment. After evacuating the air, fill it with N2, and heat it for a certain period under the protection of N2. The heating temperature is 120 °C. The heating jacket takes 8 min to heat up from room temperature to 120 °C. The stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then wash it twice with ethanol, and dry it under vacuum at 60 °C overnight for 10 h to obtain a catalyst, denoted as Au-FeO x / C (molar ratio of Au to Fe = 1:1); Subsequently, the catalytic glycerol oxidation of the catalyst to glyceric acid was evaluated.

[0077] Example 6 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.04 mmol of ferrous acetylacetonate into 10 mL of oleylamine (oleylamine purity > 99%), and ultrasonicate for 60 min at 100 Hz and stir for 180 min at 500 r / min in sequence to make the precursors disperse evenly in oleylamine, forming a precursor solution, denoted as A1; Step 2: Transfer A1 to a thick-walled pressure-resistant bottle, keep the container in a closed environment, evacuate and then fill with N2, and heat for a period of time under N2 protection. The heating temperature is 120 °C, the heating jacket takes 8 min to rise from room temperature to 120 °C, the stirring speed during heating is 1400 r / min, stir for 120 min, then cool for 45 min and wash once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then twice with ethanol, and dry overnight in vacuum at 60 °C for 10 h to obtain the catalyst, denoted as Au2-(FeO x )1 / C (molar ratio of Au to Fe = 2:1); Subsequently, the catalytic glycerol oxidation of the catalyst to glyceric acid was evaluated.

[0078] Example 7 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.16 mmol of ferrous acetylacetonate into 10 mL of oleylamine (oleylamine purity > 99%), and ultrasonicate for 60 min at 100 Hz and stir for 180 min at 500 r / min in sequence to make the precursors disperse evenly in oleylamine, forming a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a sealed environment. After evacuating the air, fill it with N2. Heat it for a certain period under the protection of N2. The heating temperature is 120 °C. The heating jacket takes 8 min to rise from room temperature to 120 °C. The stirring speed during heating is 1400 r / min. Stir for 120 min. Then, after cooling for 45 min, wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution, denoted as A3; Step 4: Ultrasonicate A2 and A3 for 50 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then twice with ethanol. Dry it under vacuum at 60 °C overnight for 10 h to obtain a catalyst, denoted as Au1-(FeO x )2 / C (the molar ratio of Au to Fe = 1:2); Subsequently, evaluate the catalytic glycerol oxidation to glyceric acid of the catalyst.

[0079] Example 8 A preparation method of a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.08 mmol of acetylacetone into 10 mL of oleylamine (oleylamine purity is greater than 99%). Ultrasonicate for 50 min under the condition of 100 Hz and stir for 500 min under the condition of 300 r / min in sequence to make the precursor disperse evenly in oleylamine to form a precursor solution, denoted as A1; Step 2: Transfer A1 into a thick-walled pressure-resistant bottle. Keep the container in a sealed environment. After evacuating the air, fill it with N2. Heat it for a certain period under the protection of N2. The heating temperature is 100 °C. The heating jacket takes 8 min to rise from room temperature to 100 °C. The stirring speed during heating is 1000 r / min. Stir for 100 min. Then, after cooling for 45 min, wash it once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 5 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution, denoted as A3; Step 4: Ultrasonicate A2 and A3 for 40 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then twice with ethanol. Dry it under vacuum at 30 °C overnight for 10 h to obtain a catalyst.

[0080] Example 9 A method for preparing a gold-based nanocatalyst, comprising the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate, 0.28 mmol of cetyltrimethylammonium bromide, and 0.08 mmol of acetylacetone into 10 mL of oleylamine (oleylamine purity greater than 99%), and ultrasonicate for 70 min under the condition of 100 Hz and stir for 160 min under the condition of 400 r / min in sequence, so that the precursor is uniformly dispersed in oleylamine to form a precursor solution, denoted as A1; Step 2: Transfer A1 to a thick-walled pressure-resistant bottle, keep the container in a closed environment, evacuate and then fill N2, and heat for a period of time under N2 protection. The heating temperature is 150 °C. The heating jacket takes 8 min to rise from room temperature to 100 °C, the stirring speed during heating is 1000 r / min, stir for 140 min, then cool for 45 min and wash once with cyclohexane and ethanol, and then add 20 mL of ethanol and ultrasonicate for 5 min to form a uniform mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonicate A2 and A3 for 60 min to mix them evenly to form solution A4; Step 5: Wash solution A4 once with cyclohexane and ethanol and then wash twice with ethanol, and dry overnight in vacuum at 50 °C for 10 h to obtain the catalyst.

[0081] Comparative Example 1 A preparation process of an Au / C (without ferrous acetylacetonate precursor) catalyst comprises the following steps: Step 1: Disperse 0.08 mmol of chloroauric acid trihydrate and 0.28 mmol of cetyltrimethylammonium bromide into 10 ml of oleylamine (oleylamine purity greater than 99%), and ultrasonicate for 60 min under the condition of 100 Hz and stir for 180 min under the condition of 500 r / min in sequence, so that the precursor is uniformly dispersed in oleylamine to form a precursor solution A1; Step 2: Transfer A1 to a thick-walled pressure-resistant bottle, keep the container in a closed environment, evacuate and then fill N2, and heat for a period of time under N2 protection. The heating temperature is 120 °C. The heating jacket takes 8 min to rise from room temperature to 120 °C, the stirring speed during heating is 1400 r / min, then cool for 45 min and wash once with cyclohexane and ethanol, and then add ethanol and ultrasonicate for 10 min to form a uniform mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Au loading to be 0.3 wt%) with ethanol and ultrasonicate for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonically mix A2 and A3 for 50 min to form a homogeneous solution A4; Step 5: Wash the reaction product A4 once with cyclohexane and ethanol, then wash it twice with ethanol, and dry it under vacuum at 60 °C overnight for 10 h to obtain the catalyst, denoted as Au / C; Subsequently, the catalytic glycerol oxidation to glyceric acid of the catalyst was evaluated.

[0082] Comparative Example 2 A preparation process of an FeOx / C (without gold precursor) catalyst includes the following steps: Step 1: Disperse 0.1 mmol of ferrous acetylacetonate and 0.28 mmol of cetyltrimethylammonium bromide into 10 ml of oleylamine (oleylamine purity is greater than 99%), ultrasonically for 60 min under the condition of 100 Hz and stir for 180 min under the condition of 500 r / min in sequence to make the precursor disperse evenly in oleylamine to form a precursor solution A1; Step 2: Transfer A1 to a thick-walled pressure-resistant bottle, keep the container in a closed environment, evacuate and then fill N2, heat for a period of time under N2 protection, the heating temperature is 120 °C, the heating jacket takes 8 min to rise from room temperature to 120 °C, the stirring speed during heating is 1400 r / min, then cool for 45 min and wash once with cyclohexane and ethanol, and then add ethanol and ultrasonically for 10 min to form a homogeneous mixed solution, denoted as A2; Step 3: Mix a certain amount of high-surface-area activated carbon (control the Fe loading to be 0.3 wt%) with ethanol and ultrasonically for 10 min to obtain a carbon support solution denoted as A3; Step 4: Ultrasonically mix A2 and A3 for 50 min to form a homogeneous solution A4; Step 5: Wash the reaction product A4 once with cyclohexane and ethanol, then wash it twice with ethanol, and dry it under vacuum at 60 °C overnight for 10 h to obtain the catalyst, denoted as Au / C; Subsequently, the catalytic glycerol oxidation to glyceric acid of the catalyst was evaluated.

[0083] For the Au4-(NdO x )1 / C, Au4-(CeO x )1 / C, Au4-(SnO x )1 / C, Au4-(FeO x1 / C (The catalyst was tested for catalytic performance using glycerol as a model reactant for catalytic alcohol compounds. During the test, the reaction conditions were: atmospheric pressure, room temperature; the metal loading of the catalyst was 0.3 wt%; the anodic electrolyte solution was a 50 ml mixed solution of 1 M KOH and 0.5 M glycerol, the cathodic electrolyte solution was 50 ml of 1 M KOH, and an anion exchange membrane was installed at the connection between the cathodic electrolytic cell and the anodic electrolytic cell; during the reaction, stirring was carried out at 800 r to prevent the catalyst from deactivating due to poisoning during the reaction. The calculation method for glycerol oxidation to glyceric acid: The product was analyzed by liquid chromatography, and the glyceric acid content in the product was the selectivity. The test results are shown in Figure 1 , as can be seen from the figure, Au4-(FeO x ) / C has the best performance.

[0084] Figure 2 This is the mapping diagram of the Au-FeO x / C (the molar ratio of gold to iron is 4:1) catalyst prepared in Example 4 of the present invention. As can be seen from the figure, some of the gold nanoparticles form small aggregates, amorphous iron oxides are attached to the surface of the gold nanoparticles, and the Au-FeOx heterojunction nanoparticles are evenly distributed on the carbon support.

[0085] The Au-FeO x / C catalysts, Au2-(FeO x )1 / C catalysts, Au1-(FeO x )2 / C catalysts, Au4-(FeO x )1 / C catalysts, the Au / C catalyst of the comparative example, and the FeO x / C catalyst prepared in Examples 4-7 and Comparative Examples 1-2 were tested for catalytic performance using the same test method as above. The test results are as shown in Figure 5 shown. As can be seen from Figure 5 , in all examples, the activity of the catalyst is closely related to the incorporation amount of the oxide FeO x . For the Au-FeO x heterojunction nanoparticles formed by FeO x modified gold nanoparticles in Examples 4 to 7, the activity of the catalyst was improved to varying degrees. Among them, the peak current density of the Au4-(FeO x )1 / C catalyst in the glycerol oxidation reaction increased by nearly seven times (compared with Comparative Example 1), and the total selectivity of glyceric acid and glycolic acid of the catalyst working at medium and high voltages for 6 h reached 93.7% (the selectivity of glyceric acid was 66%). It can be seen from Examples 4-7 that the metal oxide FeO xThe modified gold nanoparticles greatly improve the catalytic activity of gold-based catalysts, effectively increasing the glycerol conversion rate and glyceric acid selectivity. Considering both the conversion rate and selectivity, the Au4-(FeO x )1 / C catalyst exhibits the best performance.

[0086] The catalytic reaction occurs on the active surface. The adsorption, desorption, and mass transfer behaviors of reactants and reaction intermediates on the active surface are crucial for improving catalytic performance. Therefore, it is necessary to rationally design the surface structure of the catalyst. Since glycerol has multiple hydroxyl groups to be oxidized, there are multiple oxidation paths for glycerol and different products are formed. Even with high product selectivity, it is difficult to achieve a very high level of reaction current density. Au-based catalysts are not easily poisoned and have a unique adsorption ability for secondary hydroxyl groups, but their catalytic activity needs to be improved. Introducing iron oxide onto the surface of gold nanoparticles constructs an Au-FeOx interface. Due to the strong interaction between metals, the electron transfer rate is accelerated. The active sites and geometric configurations on the heterojunction interface regulate the adsorption behavior of gold towards glycerol, thereby optimizing the choice of glycerol electrooxidation path. By controlling the content of iron oxide, the optimal Au-FeOx heterojunction interface content can be screened out, and this structure has been successfully applied to the electrooxidation of glycerol to glyceric acid.

[0087] Figure 3 XRD pattern of the Au4-(FeO x )1 / C catalyst, from which the crystal form of Au4-(FeO x )1 / C can be analyzed. As Figure 3 shown, the Au4-(FeO x )1 / C sample has typical Au diffraction peaks at 2θ = 38.2°, 44.4°, 64.6°, 77.5°, 81.7°, 98.1°, 110.8°, 115.3°, 135.4° (JCPDS #04-0784), but there are no obvious diffraction peaks for FeO x , further verifying the amorphous structure of FeO x . The Au diffraction peaks do not shift, indicating that no alloy is formed with Fe. Combining the previously shown microscopic morphology, it is further determined that a small amount of amorphous iron oxide is anchored on the surface of gold nanoparticles to form an Au-FeOx heterojunction.

[0088] Figure 4 Au4-(NdO x )1 / C, Au4-(CeO x )1 / C, Au4-(SnO x )1 / C, Au4-(FeO x)1 / C was used to conduct a catalytic performance test. Glycerol was used as a model reactant for catalytic alcohol compounds. During the test, the reaction conditions were as follows: atmospheric pressure, room temperature; the catalyst loading was 0.3 wt%; the anode electrolyte solution was a 50 ml mixed solution of 1 M KOH and 0.5 M glycerol, the cathode electrolyte solution was 50 ml of 1 M KOH, and an anion exchange membrane was installed at the connection between the cathode electrolytic cell and the anode electrolytic cell; during the reaction process, stirring was carried out at 800 r to prevent the catalyst from deactivating due to poisoning during the reaction. The calculation method for glycerol oxidation to glyceric acid: The product was analyzed by liquid chromatography, and the glyceric acid content in the product was the selectivity. As can be seen from the figure, Au4-(FeO x ) / C had the best performance.

[0089] The Au-FeO x / C catalysts, Au2-(FeO x )1 / C catalysts, Au1-(FeO x )2 / C catalysts, Au4-(FeO x )1 / C catalysts, and Au / C catalysts prepared in Examples 4-7 and Comparative Examples 1-2 were subjected to a catalytic performance test using the same test method as above, and the test results are as Figure 5 shown.

[0090] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a gold-based nanocatalyst, characterized in that, It includes the following steps: After mixing a gold precursor, an iron precursor, a surfactant and a reducing solvent, ultrasonic treatment and stirring treatment are carried out in sequence to obtain a precursor solution; The precursor solution is stirred and heated in an inert atmosphere, cooled and washed, and then dispersed in ethanol to obtain a mixed solution; After the mixed solution is ultrasonically mixed with a carbon support solution, washing and drying treatments are carried out in sequence to obtain a gold-based nanocatalyst.

2. The preparation method of a gold-based nanocatalyst according to claim 1, characterized in that, The time for ultrasonic treatment of the precursor solution is 50-70 min; the time for the stirring treatment is 160-500 min, and the rotation speed is 300-500 r / min.

3. The preparation method of a gold-based nanocatalyst according to claim 1, characterized in that, The gold precursor is an inorganic compound containing gold; the inorganic compound containing gold is one of chloroauric acid, potassium chloroaurate and sodium chloroaurate.

4. The preparation method of a gold-based nanocatalyst according to claim 1, characterized in that, The iron precursor is one of ferric chloride, ferrous chloride, iron acetylacetonate and ferrous acetylacetonate; The surfactant is one or both of cetyltrimethylammonium bromide and polyvinylpyrrolidone; The reducing solvent is one of ethylene glycol, oleylamine and isopropanol.

5. The preparation method of a gold-based nanocatalyst according to claim 1, characterized in that, The dosage ratio of the gold precursor, the iron precursor, the surfactant and the reducing solvent is (0.5-1.5) mmol: (0.02-0.16) mmol: (0.1-0.5) mmol; (5-25) mL.

6. The preparation method of a gold-based nanocatalyst according to claim 1, wherein, The inert atmosphere is an N2 atmosphere in a closed space; the stirring and heating are carried out under the conditions of 100-150 °C and 1000-1400 r / min for 100-140 min; the volume ratio of the reducing solvent to ethanol is (5-25):

20.

7. The preparation method of a gold-based nanocatalyst according to claim 1, wherein, The carbon support solution is obtained by ultrasonically dispersing an activated carbon support in ethanol, and the ultrasonic dispersion is carried out at 100 Hz for 5-10 min; the dosage ratio of the activated carbon support to ethanol is 36.7 mg - 20 mL.

8. The preparation method of a gold-based nanocatalyst according to claim 1, wherein The volume dosage ratio of the mixed solution to the carbon support solution is 1:1; The washing is carried out with cyclohexane and ethanol with a volume ratio of 1:9; The time for ultrasonic mixing of the mixed solution and the carbon support solution is 40-60 min; The temperature of the drying treatment is 30-60 °C.

9. A gold-based nanocatalyst, characterized in that, Prepared by the preparation method described in any one of claims 1 to 8; the gold-based nanocatalyst has Au-FeO formed by Fe oxide anchored and modified on gold nanoparticles x heterojunction nanoparticles, and the Au-FeO x microstructure formed by the heterojunction nanoparticles loaded on a carbon support; The Au-FeO x The particle size of the heterojunction nanoparticles is 5 to 20 nm; The gold content in the gold-based nanocatalyst is 0.15 wt% - 0.35 wt%, and the molar amount of iron is one-fourth of that of gold.

10. Application of the gold-based nanocatalyst according to claim 9 in the reaction of electro-oxidizing glycerol to glyceric acid.

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