A noble metal supported spherical catalyst and a method for preparing the same

Abstract

The application relates to the technical field of catalyst material preparation, in particular to a noble metal-loaded spherical catalyst and a preparation method thereof. The preparation method comprises the following steps: S1: a boron-containing compound, a nitrogen source and formaldehyde are added into a solvent and stirred uniformly, and a catalyst is added to obtain polymer microspheres through reaction; S2: the polymer microspheres are carbonized to obtain boron-nitrogen-doped carbon microspheres; S3: the boron-nitrogen-doped carbon microspheres are dispersed in a solvent, a noble metal compound is added and stirred, and then filtration, drying and carbonization are sequentially carried out to obtain the noble metal-loaded spherical catalyst. The boron-containing monomer and the nitrogen source with a specific structure are used as the comonomers, and the in-situ boron-nitrogen-doped carbon microspheres are prepared under the catalysis of the catalyst. The noble metal can be loaded on the carbon microspheres as the matrix, so that the loading capacity of the noble metal can be remarkably improved, and the catalytic effect of the noble metal-loaded carbon can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalytic material preparation, in particular to a noble metal loaded spherical catalyst and a preparation method thereof. BACKGROUND

[0002] Platinum, gold, palladium, rhodium and other noble metals are important catalyst materials and functional materials. In the field of catalysis, direct use of noble metals as catalysts not only has low utilization rate and large amount, but also often forms a homogeneous catalytic system during the reaction, which makes it difficult to separate and purify the product, resulting in difficulty in recycling and reuse of the catalyst. Therefore, more and more researchers have begun to focus on the design and preparation of supported nanometer noble metal heterogeneous catalysts.

[0003] Among the many supported catalysts, activated carbon supported noble metal catalysts are widely used due to their small density and low cost. The traditional activated carbon supported noble metal catalysts use pure carbon, and the catalytic effect is low. The performance can be improved by doping other elements such as N, B, P, S, O, etc. Among them, nitrogen-doped carbon materials have stable chemical structure, large pore volume and specific surface area. The doping of nitrogen atoms helps to enhance the electron transport of the carrier and adjust the chemical and electronic properties of the supported phase, thereby playing a role in stabilizing and dispersing the active center, and thus has become a research hotspot of supported catalysts.

[0004] For example, the Chinese invention patent with application number 201710067598.X discloses a nitrogen-doped carbon supported nanometer noble metal catalyst. The noble metal compound is adsorbed on the cyan-functionalized ionic liquid through ion exchange or coordination, and then a nitrogen-doped carbon supported nanometer noble metal catalyst is prepared by high-temperature calcination. The Chinese invention patent with application number 201611115350.8 relates to a preparation method of a nitrogen-doped carbon material supported noble metal catalyst and its application in alcohol catalytic oxidation. The carbon material is modified by nitrogen at low temperature through pyrolysis treatment of a nitrogen-containing macrocyclic compound, and then loaded with noble metal. The Chinese invention patent with application number 201810976586.3 discloses a composite carbon-nitrogen-noble metal catalyst, its preparation method and application in the synthesis of 3-alkylpiperidines. The noble metal catalyst is composed of nitrogen-containing graphene quantum dots and their composites and noble metal particles. The noble metal particles are deposited on the surface of the nitrogen-containing graphene quantum dot composite, and the nitrogen-containing graphene quantum dot composite and the nitrogen-containing graphene quantum dots with noble metal particles are uniformly dispersed in pure water solvent.

[0005] Although the above patent documents all report carbon material doped noble metal catalysts, most of the carbon material substrates are amorphous carbon, have low specific surface area, irregular structure, and poor adsorption capacity; the carriers are all single-doped, such as single nitrogen-doped, and the doping amount is too low, with most of the nitrogen doping amount being below 1%, leading to poor carrier stability, non-ideal pore structure and surface physicochemical properties, and thus problems of low noble metal loading and poor catalytic effect. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a noble metal loaded spherical catalyst with good catalytic effect and a preparation method thereof.

[0007] To solve the above technical problem, the technical scheme adopted by the present application is as follows: a preparation method of a noble metal loaded spherical catalyst, comprising the following steps:

[0008] S1: adding a boron-containing compound, a nitrogen source and formaldehyde into a solvent and stirring until uniform, and adding a catalyst to react to obtain a polymer microsphere;

[0009] S2: carbonizing the polymer microsphere to obtain a boron-nitrogen doped carbon microsphere;

[0010] S3: dispersing the boron-nitrogen doped carbon microsphere in a solvent, adding a noble metal compound and stirring, and sequentially performing filtration, drying and carbonization to obtain a noble metal loaded spherical catalyst;

[0011] The chemical structural formula of the boron-containing compound is shown in formula (1) or formula (2):

[0012]

[0013] wherein R1 is a hydroxyl group or an amino group, R2 and R3 are halogen or hydrogen, and when one of R2 and R3 is halogen, the other is hydrogen.

[0014] Another technical scheme adopted by the present application is: the noble metal loaded spherical catalyst prepared by the above preparation method, wherein the carrier is a boron-nitrogen doped carbon microsphere, the mass percentage of boron in the boron-nitrogen doped carbon microsphere is ≥4%, and the mass percentage of nitrogen is ≥4%.

[0015] The noble metal loaded spherical catalyst of the present application is prepared in-situ by using a specific structure of boron-containing monomer and nitrogen source as a comonomer under the catalysis of a catalyst, and one active site of the benzene ring in the boron monomer is occupied, which can inhibit the substitution reaction on the ring, thereby controlling the cross-linking structure of the resin to form more pores. The introduction of the nitrogen source can further destroy the regularity of the molecular chain, so that the polymer microspheres have better cracking effect at high temperature, and porous carbon with large specific surface area is prepared. At the same time, the introduction of nitrogen can promote the formation of B-N covalent structure, and doped carbon microspheres with high boron and nitrogen content are obtained. Loading noble metal on the carbon microspheres as a matrix can significantly improve the loading amount of noble metal and improve the catalytic effect of noble metal loaded carbon. DETAILED DESCRIPTION

[0016] To illustrate the technical content, purposes and effects of the present application, the following embodiments are described.

[0017] The technical solution adopted by the present application is as follows: the preparation method of the noble metal loaded spherical catalyst described above, comprising the following steps:

[0018] S1: adding a boron-containing compound, a nitrogen source and formaldehyde into a solvent to stir uniformly, and adding a catalyst to react to obtain polymer microspheres;

[0019] S2: carbonizing the polymer microspheres to obtain boron and nitrogen doped carbon microspheres;

[0020] S3: dispersing the boron and nitrogen doped carbon microspheres in a solvent, adding a noble metal compound and stirring, and then sequentially performing filtration, drying and carbonization to obtain a noble metal loaded spherical catalyst;

[0021] The chemical structural formula of the boron-containing compound is shown in formula (1) or formula (2):

[0022]

[0023] wherein R1 is hydroxyl or amino, R2 and R3 are halogen or hydrogen, and when one of R2 and R3 is halogen, the other is hydrogen.

[0024] As can be seen from the above description, the present application uses a specific structure of boron-containing monomer and nitrogen source as a comonomer to prepare in-situ boron and nitrogen doped polymer microspheres under the catalysis of a catalyst. The noble metal loaded on the boron and nitrogen doped polymer microspheres as a matrix can provide an attachment space for the noble metal compound, significantly improve the loading amount of noble metal, and improve the catalytic effect of noble metal loaded carbon.

[0025] This invention uses a boron-containing monomer with a specific structure as the boron source. By pre-occupying an active site on the benzene ring with boron-containing groups, the substitution reaction on the benzene ring is suppressed, thereby adjusting the crosslinking density of the polymer microspheres. Because the number of substitution sites on the benzene ring is reduced, the crosslinking density decreases, allowing for more efficient cleavage of the carbonized molecular chain segments and the benzene ring. This results in a better steric sag, forming more pores and creating a larger specific surface area, thus obtaining carbon microspheres with high boron content and high specific surface area.

[0026] Meanwhile, in order to suppress the pore blockage caused by the formation of boron oxides, nitrogen source is used as comonomer. On the one hand, by introducing nitrogen-containing structures into the molecular structure, the regularity of the molecular chain is disrupted, promoting the tendency of benzene rings to break during high-temperature pyrolysis, enriching the pore structure, and further increasing the specific surface area of ​​porous carbon. On the other hand, the high nitrogen content is conducive to the formation of BN covalent structure, inhibiting the formation of boron oxides. The formed BN covalent groups can also significantly improve the application performance of carbon materials.

[0027] Halogens can be introduced onto the benzene ring of boron-containing monomers to further weaken the reactivity of the benzene ring and inhibit substitution reactions. However, the reactivity of the benzene ring in the boron-containing monomer cannot be too low; otherwise, the reaction rate will be too slow, the degree of cross-linking will be too low, reducing the thermal stability of the carbon microspheres, and the pores will easily collapse during pyrolysis, clogging the channels and reducing the specific surface area. The boron content in the boron-containing monomer should not be too high, as excessive boron content will cause difficulties in pyrolysis, reduce pore size, and excessive boron will easily form boron oxides, which not only fail to effectively promote catalysis but also clog the channels and reduce the specific surface area.

[0028] Furthermore, the boron-containing compound is any one of 4-hydroxyphenylboronic acid, 2-hydroxyphenylboronic acid, 2-fluoro-4-hydroxyphenylboronic acid, 2-aminophenylboronic acid, and 4-aminophenylboronic acid.

[0029] Furthermore, the nitrogen source can be any one of urea, melamine, OAT, and aminophenol.

[0030] OAT is a waste product generated during the melamine production process, and its main components are nitrogen-containing aromatic compounds.

[0031] As described above, urea, melamine, OAT, or aminophenol all exhibit good reactivity with formaldehyde as nitrogen sources and can co-condense with boron-containing compounds, introducing nitrogen in situ into the polymer microspheres to provide nitrogen for subsequent carbon microspheres. Using OAT as a nitrogen source to prepare nitrogen-doped microspheres and carbon microspheres offers significant advantages in terms of resources, environmental friendliness, and cost.

[0032] Furthermore, the catalyst is any one of ammonia, ethylenediamine, and hexamethylenetetramine.

[0033] From the above description, the nitrogen element can be introduced by using the benzene ring compound with amino group or using ammonia or amine as catalyst to further increase the nitrogen content. In the prior art, only the catalyst is used as the nitrogen source, the reactivity is very low, and the amount of resin introduced is not much, so the nitrogen content of the prepared carbon microspheres is low, and the stability of the carrier is poor.

[0034] Further, the solvent is at least one of water, ethanol, methanol, acetone, tetrahydrofuran, methane and chloroform.

[0035] Further, the noble metal compound is at least one of rhodium trichloride, gold trichloride, aurous chloride, palladium chloride, chloroauric acid, chloroplatinic acid, potassium hexachloroplatinate, sodium hexachloroplatinate, platinum tetrachloride, platinum acetylacetone, palladium nitrate, palladium acetate and amine tetrachloropalladate.

[0036] From the above description, the boron-nitrogen-doped carbon microspheres have a large number of pore structures, which can provide attachment space for the noble metal compound. By changing the amount of noble metal compound and the solution temperature and other parameters, the loading amount of noble metal in the carbon microspheres can be adjusted.

[0037] Further, the noble metal compound can be directly added, or the pure noble metal compound can be configured into a solution, or the noble metal compound solution in the process of recycling waste noble metal substrate can be directly used.

[0038] Further, the reaction conditions in step S1 are: reacting at a temperature of 100-140℃ for 6-24h.

[0039] Further, the specific steps of carbonization in step S2 are: carbonizing at a carbonization temperature of 600-800℃ for 2-4h in an inert gas atmosphere.

[0040] From the above description, the carbonization in step S2 is to obtain a porous structure,

[0041] Further, the specific steps of carbonization in step S3 are: carbonizing at a carbonization temperature of 700-1000℃ for 2-5h in an inert gas atmosphere.

[0042] From the above description, the carbonization in step S3 is to obtain the noble metal element or its covalent substance with boron and nitrogen, so as to play a catalytic effect.

[0043] Further, the inert gas is nitrogen or argon.

[0044] Another technical solution adopted by the present application is: the noble metal loaded spherical catalyst prepared by the above preparation method, the carrier is boron-nitrogen-doped carbon microspheres, the mass percentage of boron in the boron-nitrogen-doped carbon microspheres is ≥4%, and the mass percentage of nitrogen is ≥4%.

[0045] From the above description, the beneficial effects of the application are that the mass percentage of boron in the spherical catalyst is ≥4%, and the mass percentage of nitrogen is ≥4%, both of which have a relatively high mass percentage of boron and nitrogen, can increase the specific surface area of the boron and nitrogen doped carbon microspheres, significantly improve the loading capacity of noble metals, and improve the catalytic effect of noble metal loaded carbon.

[0046] Further, the specific surface area of the boron and nitrogen doped carbon microspheres is ≥400m 2 / g.

[0047] From the above description, the large specific surface area can increase the adsorption capacity of the noble metal salt solution, increase the content and dispersion effect of the noble metal in the catalyst, and on the other hand, can also provide rich catalytic space for the catalytic process and improve the catalytic effect.

[0048] Further, the particle size of the boron and nitrogen doped carbon microspheres is ≤1000nm.

[0049] Embodiment 1 of the application is:

[0050] A preparation method of a noble metal loaded spherical catalyst, comprising the following steps:

[0051] S1: 0.2g 4-hydroxyphenylboronic acid, 0.04g melamine and 0.3g 37% mass fraction formaldehyde aqueous solution are added to 20mL water, stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, and after 12h reaction at 120℃, polymer microspheres are obtained;

[0052] S2: the polymer microspheres are carbonized at 700℃ for 4h under a nitrogen atmosphere to obtain boron and nitrogen doped carbon microspheres;

[0053] S3: the boron and nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 0.001g chloroplatinic acid is added, stirred and dispersed and adsorbed by ultrasonic treatment, filtered and dried, then carbonized at 800℃ for 2h under a nitrogen atmosphere to obtain a noble metal loaded spherical catalyst.

[0054] It is detected that the mass percentage of nitrogen in the boron and nitrogen doped carbon microspheres is 4.2%, the mass percentage of boron is 4.7%, the BET (specific surface area) is 522m 2 / g, and the average particle size is about 825nm.

[0055] Embodiment 2 of the application is a preparation method of a noble metal loaded spherical catalyst, comprising the following steps:

[0056] S1: 0.2g 4-hydroxyphenylboronic acid, 0.04g OAT and 0.3g 37% mass fraction formaldehyde aqueous solution are added into 20mL water, stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, and polymer microspheres are obtained after 12h reaction at 120℃;

[0057] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere to obtain boron-nitrogen doped carbon microspheres;

[0058] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 0.001g chloroplatinic acid is added, stirred and dispersed and adsorbed by ultrasonic treatment, filtered and dried, then carbonized at 800℃ for 2h under nitrogen atmosphere to obtain noble metal loaded spherical catalyst.

[0059] It is detected that the mass percentage of nitrogen of the boron-nitrogen doped carbon microspheres is 4.3%, the mass percentage of boron is 4.2%, the BET (specific surface area) is 483m 2 / g, and the average particle size is about 859nm.

[0060] Embodiment 3 of the present application is a preparation method of noble metal loaded spherical catalyst, comprising the following steps:

[0061] S1: 0.2g 4-hydroxyphenylboronic acid, 0.06g urea and 0.3g 37% mass fraction formaldehyde aqueous solution are added into 20mL water / ethanol solution (volume ratio of water to ethanol is 4:1), stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, and polymer microspheres are obtained after 12h reaction at 120℃;

[0062] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere to obtain boron-nitrogen doped carbon microspheres;

[0063] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 1mL palladium chloride ethanol solution (concentration is 0.001g / mL) is added, stirred and dispersed and adsorbed by ultrasonic treatment, filtered and dried, then carbonized at 800℃ for 2h under nitrogen atmosphere to obtain noble metal loaded spherical catalyst.

[0064] It is detected that the mass percentage of nitrogen of the boron-nitrogen doped carbon microspheres is 4.5%, the mass percentage of boron is 6.7%, the BET (specific surface area) is 559m 2 / g, and the average particle size is about 761nm.

[0065] Embodiment 4 of the present application is a preparation method of noble metal loaded spherical catalyst, comprising the following steps:

[0066] S1: 0.1g 4-hydroxyphenylboronic acid, 0.03g melamine and 0.15g 37% mass fraction formaldehyde aqueous solution are added into 20mL water / ethanol solution (volume ratio of water to ethanol is 4:1), stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, and the polymer microspheres are obtained after 12h reaction at 120℃;

[0067] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere to obtain boron-nitrogen doped carbon microspheres;

[0068] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 2mL palladium chloride ethanol solution (concentration is 0.001g / mL) is added, stirred and dispersed and adsorbed by ultrasonic treatment, filtered and dried, then the noble metal loaded spherical catalyst is obtained after carbonization at 800℃ for 2h under nitrogen atmosphere.

[0069] It is detected that the mass percentage of nitrogen of the boron-nitrogen doped carbon microspheres is 5.1%, the mass percentage of boron is 5.4%, the BET (specific surface area) is 667m 2 / g, and the average particle size is about 645nm.

[0070] Embodiment 5 of the application is a preparation method of a noble metal loaded spherical catalyst, comprising the following steps:

[0071] S1: 0.1g 2-hydroxyphenylboronic acid, 0.03g melamine and 0.15g 37% mass fraction formaldehyde aqueous solution are added into 20mL water / ethanol solution (volume ratio of water to ethanol is 4:1), stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, and the polymer microspheres are obtained after 12h reaction at 120℃;

[0072] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere to obtain boron-nitrogen doped carbon microspheres;

[0073] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 2mL palladium chloride ethanol solution (concentration is 0.001g / mL) is added, stirred and dispersed and adsorbed by ultrasonic treatment, filtered and dried, then the noble metal loaded spherical catalyst is obtained after carbonization at 800℃ for 2h under nitrogen atmosphere.

[0074] Embodiment 6 of the application is a preparation method of a noble metal loaded spherical catalyst, comprising the following steps:

[0075] S1: 0.1g 2-fluoro-4-hydroxyphenylboronic acid, 0.03g melamine and 0.15g 37% mass fraction formaldehyde aqueous solution are added into 20mL acetone / tetrahydrofuran solution, stirred uniformly, then 0.1g 25% mass fraction ammonia water is added, after 10h reaction at 140℃, polymer microspheres are obtained;

[0076] S2: the polymer microspheres are carbonized at 800℃ for 2h under nitrogen atmosphere, boron-nitrogen doped carbon microspheres are obtained;

[0077] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 0.002g sodium hexachloroplatinate, platinum tetrachloride and platinum acetylacetone mixture are added, after stirring, ultrasonic treatment is adopted to make them dispersed and adsorbed, after filtration and drying, noble metal loaded spherical catalyst is obtained after carbonization at 700℃ for 5h under nitrogen atmosphere.

[0078] Embodiment 7 of the application is a preparation method of noble metal loaded spherical catalyst, comprising the following steps:

[0079] S1: 0.1g 2-amino phenylboronic acid, 0.03g aminophenol and 0.15g 37% mass fraction formaldehyde aqueous solution are added into 20mL water / methanol solution (volume ratio of water to methanol is 4:1), stirred uniformly, then 0.1g ethylenediamine is added, after 6h reaction at 120℃, polymer microspheres are obtained;

[0080] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere, boron-nitrogen doped carbon microspheres are obtained;

[0081] S3: the boron-nitrogen doped carbon microspheres are dispersed in 10mL ethanol solution, then 0.002g chloroauric acid, chloroplatinic acid and potassium hexachloroplatinate mixture are added, after stirring, ultrasonic treatment is adopted to make them dispersed and adsorbed, after filtration and drying, noble metal loaded spherical catalyst is obtained after carbonization at 800℃ for 2h under nitrogen atmosphere.

[0082] Embodiment 8 of the application is a preparation method of noble metal loaded spherical catalyst, comprising the following steps:

[0083] S1: 0.1g 4-amino phenylboronic acid, 0.03g urea and 0.15g 37% mass fraction formaldehyde aqueous solution are added into 20mL water / ethanol solution (volume ratio of water to ethanol is 4:1), stirred uniformly, then 0.1g 25% mass fraction hexamethylenetetramine is added, after 24h reaction at 120℃, polymer microspheres are obtained;

[0084] S2: the polymer microspheres are carbonized at 700℃ for 4h under nitrogen atmosphere, boron-nitrogen doped carbon microspheres are obtained;

[0085] S3: disperse the boron-nitrogen doped carbon microspheres in 10 mL of ethanol solution, then add 0.002 g of a mixture of rhodium trichloride, gold trichloride and aurous chloride, and after stirring, disperse and adsorb by ultrasonic treatment, then filter and dry, and then obtain a noble metal loaded spherical catalyst by carbonizing at 800℃ for 2 h under a nitrogen atmosphere.

[0086] The comparative example 1 of the present application is a preparation method of a noble metal loaded spherical catalyst (wherein no nitrogen source is added), comprising the following steps:

[0087] S1: add 0.2 g of 4-hydroxyphenylboronic acid and 0.3 g of a 37% mass fraction formaldehyde aqueous solution into 20 mL of water, stir until uniform, then add 0.1 g of a 25% mass fraction ammonia water, and obtain polymer microspheres after reacting at 120℃ for 12 h;

[0088] S2: obtain boron-nitrogen doped carbon microspheres by carbonizing the polymer microspheres at 700℃ for 4 h under a nitrogen atmosphere;

[0089] S3: disperse the boron-nitrogen doped carbon microspheres in 10 mL of ethanol solution, then add 0.001 g of chloroplatinic acid, and after stirring, disperse and adsorb by ultrasonic treatment, then filter and dry, and then obtain a noble metal loaded spherical catalyst by carbonizing at 800℃ for 2 h under a nitrogen atmosphere.

[0090] It is detected that the mass percentage of nitrogen in the boron-nitrogen doped carbon microspheres is 0.5%, the mass percentage of boron is 4.1%, the BET (specific surface area) is 403 m 2 / g, and the average particle size is about 701 nm.

[0091] The comparative example 2 of the present application is a preparation method of a noble metal loaded spherical catalyst (wherein the boron-containing compound is boric acid), comprising the following steps:

[0092] S1: add 0.2 g of boric acid, 0.04 g of melamine and 0.3 g of a 37% mass fraction formaldehyde aqueous solution into 20 mL of water, stir until uniform, then add 0.1 g of a 25% mass fraction ammonia water, and obtain polymer microspheres after reacting at 120℃ for 12 h;

[0093] S2: obtain boron-nitrogen doped carbon microspheres by carbonizing the polymer microspheres at 700℃ for 4 h under a nitrogen atmosphere;

[0094] S3: disperse the boron-nitrogen doped carbon microspheres in 10 mL of ethanol solution, then add 0.001 g of chloroplatinic acid, and after stirring, disperse and adsorb by ultrasonic treatment, then filter and dry, and then obtain a noble metal loaded spherical catalyst by carbonizing at 800℃ for 2 h under a nitrogen atmosphere.

[0095] The boron-nitrogen doped carbon microspheres were detected to have a nitrogen mass percentage of 3.5%, a boron mass percentage of 0.2%, a BET (specific surface area) of 506 m 2 / g, and an average particle size of about 769 nm.

[0096] The catalytic performance of the noble metal loaded spherical catalysts prepared from the noble metal loaded spherical catalysts of Examples 1 to 4 and Comparative Examples 1 and 2 was tested by the following method.

[0097] 0.004 g of the noble metal loaded spherical catalyst was added with 0.2 mL of isopropyl alcohol, 0.77 mL of water and 0.032 mL of a 5 wt.% Nafion (perfluorosulfonic acid type polymer) solution, and after ultrasonic dispersion, a uniform slurry was obtained. 10 μL of the slurry was dropped onto the surface of a 0.196 cm 2 long and 0.196 cm 2 wide glassy carbon electrode, and after drying in a fume hood for 2 h, a working electrode having a loading of 0.2 mg / cm 2 was obtained. Oxygen was passed at a flow rate of 50 mL / min for 30 min to saturate the solution with oxygen. A 6M KOH electrolyte and a three-electrode system were used for the test, and the three-electrode system included a reference electrode (Hg / HgO), a counter electrode (Pt sheet) and the working electrode. The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100] As shown in Table 1, the half-wave potential and the limiting current density of Examples 1 to 4 are higher than those of Comparative Examples 1 and 2, which shows better catalytic effect. Therefore, the boron-nitrogen doped carbon microspheres prepared by the method of the present application have good electrochemical performance and good catalytic effect.

[0101] In summary, the preparation method provided by the present application uses a specific structure of boron monomer and nitrogen source comonomer to prepare a polymer microsphere with high boron-nitrogen content under the catalysis of ammonia or amine catalyst. The boron monomer has one active site of the benzene ring occupied, which can inhibit the substitution reaction on the ring, thereby controlling the crosslinking structure of the resin and forming more pores. The introduction of the nitrogen source can further destroy the regularity of the molecular chain, so that the polymer microsphere has better cracking effect at high temperature and a large specific surface area of the porous carbon is prepared. Meanwhile, the introduction of nitrogen can promote the formation of B-N covalent structure and obtain the doped carbon microsphere with high boron-nitrogen content.

[0102] The boron-nitrogen doped carbon microspheres are filtered, dried and carbonized in sequence to obtain the noble metal loaded spherical catalyst. Since the boron-nitrogen doped carbon microspheres have many pores and high boron-nitrogen content, the use of the carbon microspheres as a substrate to load noble metal can significantly increase the loading amount of noble metal and promote the catalytic effect of the noble metal loaded carbon.

[0103] The above description is merely that of embodiments of the application, and is not intended to limit the patent scope of the application. Any equivalent variation or direct or indirect application in related technical fields made by using the description of the application shall be included in the patent protection scope of the application.

Claims

1. Use of a noble metal supported spherical catalyst in an oxygen reduction reaction, characterized in that, The preparation method of the noble metal loaded spherical catalyst comprises the following steps: S1: a boron-containing compound, a nitrogen source and formaldehyde are added into a solvent and stirred uniformly, and a catalyst is added for reaction to obtain polymer microspheres; the nitrogen source is any one of urea, melamine, OAT and aminophenol, the OAT is a waste produced in a melamine production process, and the main component of the OAT is a nitrogen-containing aromatic compound; S2: the polymer microspheres are carbonized to obtain boron-nitrogen-doped carbon microspheres; S3: the boron-nitrogen-doped carbon microspheres are dispersed in a solvent, a noble metal compound is added and stirred, and then filtration, drying and carbonization are sequentially performed to obtain the noble metal loaded spherical catalyst; The chemical structural formula of the boron-containing compound is shown in formula (1) or formula (2): Formula (1), Formula (2); wherein R1 is a hydroxyl group or an amino group, R2 and R3 are halogen or hydrogen, and when one of R2 and R3 is halogen, the other is hydrogen; The catalytic performance of the noble metal loaded spherical catalyst is tested, and the specific steps are as follows: oxygen is passed at a flow rate of 50 mL / min for 30 min to make the oxygen in the solution saturated, and a 6 M KOH electrolyte and a three-electrode system are used for testing.

2. Use according to claim 1, characterized in that, The boron-containing compound is any one of 4-hydroxyphenylboronic acid, 2-hydroxyphenylboronic acid, 2-fluoro-4-hydroxyphenylboronic acid, 2-aminophenylboronic acid and 4-aminophenylboronic acid.

3. Use according to claim 1, characterized in that, The catalyst in S1 is any one of ammonia, ethylenediamine and hexamethylenetetramine.

4. Use according to claim 1, characterized in that, The solvent is at least one of water, ethanol, methanol, acetone, tetrahydrofuran, methane and chloroform.

5. The use according to claim 1, characterized in that, The noble metal compound is at least one of rhodium trichloride, gold trichloride, aurous chloride, palladium chloride, chloroauric acid, chloroplatinic acid, potassium hexachloroplatinate, sodium hexachloroplatinate, platinum tetrachloride, platinum acetylacetonate, palladium nitrate, palladium acetate and amine tetrachloropalladate.

6. Use according to claim 1, characterized in that, The reaction condition in S1 is that the reaction is carried out at a temperature of 100-140 DEG C for 6-24 h.

7. Use according to claim 1, characterized in that, The specific step of carbonization in S2 is that the carbonization is carried out in an inert gas atmosphere at a carbonization temperature of 600-800 DEG C for 2-4 h.

8. The use according to claim 1, characterized in that, The specific step of carbonization in S3 is that the carbonization is carried out in an inert gas atmosphere at a carbonization temperature of 700-1000 DEG C for 2-5 h.

9. Use according to any one of claims 1 to 8, characterized in that, The carrier of the noble metal loaded spherical catalyst is boron-nitrogen-doped carbon microspheres, and the mass percentage of boron in the boron-nitrogen-doped carbon microspheres is ≥4%, and the mass percentage of nitrogen is ≥4%.

10. Use according to claim 9, characterized in that, The boron-nitrogen doped carbon microspheres have a specific surface area of ≥400 m 2 / g.

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