阅读说明：本技术 一种合成小尺寸高分散金属间化合物催化剂材料的方法及应用 (Method for synthesizing small-size high-dispersion intermetallic compound catalyst material and application ) 是由 廖世军 赵伟悦 崔志明 于 2019-09-12 设计创作，主要内容包括：本发明公开了一种合成小尺寸高分散金属间化合物催化剂材料的方法及应用。该方法为使用含有贵金属前驱体和非贵金属前驱体的溶液浸渍MOF衍生的碳材料,冷冻干燥,在含有还原性气氛的环境中高温处理。得到Pt<Sub>x</Sub>M金属间化合物催化剂纳米粒子颗粒度小,粒子分布均匀且均匀地分布于MOF衍生碳的表面及介孔内部。本发明提出的利用MOF衍生碳限域作用控制粒径的方法制得的金属间化合物与通常方法制备的金属间化合物相比较,具有尺寸小、分散均匀、且许多纳米粒子可以分散到MOF衍生碳的孔道中的重要优点。制备的有序Pt<Sub>x</Sub>M/MOFDC催化剂用于燃料电池的氧还原反应,表现出良好的催化性能。(The invention discloses a method for synthesizing a small-size high-dispersion intermetallic compound catalyst material and application thereof. The method comprises the steps of impregnating an MOF-derived carbon material with a solution containing a noble metal precursor and a non-noble metal precursor, freeze-drying, and carrying out high-temperature treatment in an environment containing a reducing atmosphere. Obtaining Pt x The M intermetallic compound catalyst has small particle size of the nanoparticles, and the particles are uniformly distributed on the surface of the MOF derived carbon and in the mesopores. Compared with the intermetallic compound prepared by the common method, the intermetallic compound prepared by the method for controlling the particle size by utilizing the MOF derived carbon confinement effect has the important advantages of small size, uniform dispersion and capability of dispersing a plurality of nano particles into the pore channels of the MOF derived carbon. Prepared ordered Pt x The M/MOFDC catalyst is used for the oxygen reduction reaction of the fuel cell and shows good catalytic performance.)

1. A method for synthesizing a small-size high-dispersion intermetallic compound catalyst material is characterized in that MOFs-derived porous carbon is used as a hard template to realize the control of the size of intermetallic compound nanoparticles; the catalyst material is a MOF-derived carbon-supported platinum-based intermetallic compound;

the method specifically comprises the following steps:

(1) synthesizing an MOF material, namely thermally cracking the MOF material at high temperature under inert gas, and then pickling, drying and grinding for later use;

(2) dissolving a noble metal precursor and a non-noble metal precursor in deionized water or an organic solvent, and ultrasonically dissolving and uniformly mixing; the noble metal precursor comprises acid or salt containing Pt, Pd, Au and Rh; the non-noble metal precursor comprises Fe salt, Co salt, Ni salt or Cu salt; the organic solvent comprises DMF, ethanol or isopropanol;

(3) dipping the product obtained in the step (1) into the solvent obtained in the step (2), immersing the solution into the micro-channels of the carbon material by ultrasonic waves, and then adopting freeze drying or vacuum drying;

(4) roasting the product obtained in the step (3) at high temperature in a reducing atmosphere environment to obtain the MOF carbon-loaded ordered intermetallic compound nanoparticle catalyst Pt_xM/MOFDC。

2. The method of claim 2, wherein in step (1), the MOF comprises ZIF-8, ZIF-67 or UIO-66.

3. The method as claimed in claim 2, wherein in step (1), the thermal cracking temperature is 900-1100 ℃ and the time is 1-3 hours; the inert gas is helium, argon or high-purity nitrogen.

4. The method according to claim 2, wherein in the step (1), the pickling temperature is 60-90 ℃ and the pickling time is 8-12 hours.

5. The method of claim 2, wherein the precursor solution of step (2) has a noble metal to non-noble metal molar ratio of 3:1, 1:1, or 1: 3.

6. The method according to claim 2, wherein in the step (2), when the solvent is deionized water, ethanol or isopropanol, the precious metal precursor is an inorganic acid or an inorganic salt such as chloroplatinic acid, chloropalladic acid, chloroauric acid or ammonium chlororhodate, and the non-precious metal precursor is an inorganic metal salt such as a chloride salt, a nitrate salt or a sulfate salt; when the solvent is DMF, the noble metal precursor is acetylacetone salt, and the non-noble metal precursor is acetylacetone salt.

7. The method of claim 2, wherein in step (3), the impregnating process is uniformly dropping a metal precursor solution drop by drop into the MOF-derived carbon; the ultrasonic mixing time is 0.5-2 hours.

8. Method according to claim 2, characterised by the steps of(4) In (1), the reducing gas is H₂Mixed gas of/Ar and NH₃/He、H₂Mixed gas of/He and NH₃/N₂、H₂/N₂Mixing the gas; the roasting temperature is 650-850 ℃ and the time is 1.5-4 hours.

9. Ordered Pt obtainable by the process according to any one of claims 1 to 9_xThe application of M/MOFDC in fuel cell catalyst.

Technical Field

The invention belongs to the field of new energy materials, and particularly relates to a synthetic method and application of a small-particle-size high-dispersion intermetallic compound.

Background

Proton Exchange Membrane Fuel Cells (PEMFC) have the advantages of high energy conversion efficiency, no pollution and the like, and are one of the most important new energy technologies in the 21 st century. Commercialization of fuel cells remains a significant challenge due to cost and durability issues. One of the main factors affecting fuel cell performance and cost is the catalyst of the cathode. Pt_xThe M alloy catalyst can simultaneously improve the catalytic stability and the specific quality activity due to the electronic effect and the geometric effect of the transition metal M on Pt, and effectively reduce the catalyst cost. However, such conventional alloys (solid solutions) have problems that the transition metal is easily dissolved out, resulting in a decrease in catalyst activity and degradation of the film. The ordered alloy, namely the intermetallic compound, formed by the catalyst through heat treatment can greatly improve the structural stability and the electrochemical stability, effectively solve the problem of the dissolution of transition metal and improve the durability of the catalyst. However, the high-temperature ordering treatment can cause the agglomeration of catalyst nano particles and the reduction of the electrochemical specific surface, thereby causing the reduction of the activity of the catalyst. Therefore, in the high-temperature heat treatment process of forming the ordered intermetallic compound, a simple and efficient method is found to inhibit the agglomeration and growth of the nano-particles, and the control of the particle size of the intermetallic compound is of great significance. Based on this, a great deal of research has been conducted on the preparation method of the intermetallic compound. Francis J. DiSalvo et al (Francis J. DiSalvo, et al, J. Am. chem. Soc. 2012, 134, 18453-18459) in organic systems by passing Pt₃The method of embedding Fe nano-particles into a KCl matrix is used for inhibiting particle agglomeration in a high-temperature process. The chinese patent application 109616671 a proposes that a simple freeze-drying method is adopted in a water system to form a highly dispersed precursor and inhibit the agglomeration and growth of particles in the high-temperature calcination reduction process.

Although many researches on controlling the particle size of the intermetallic compound have been reported, most of the researches are directed at single system, the synthesis method has no universality, and the process is complex. Therefore, a simple, efficient and universal method is found, the agglomeration and growth of intermetallic compound particles can be effectively inhibited in inorganic and organic systems, and the improvement of the dispersibility is of great significance.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention discloses a synthetic method for preparing a small-particle-size and high-dispersion intermetallic compound and application thereof. In the preparation process, the MOF derived carbon has the functions of a template agent and a carrier, and the method is simple, efficient and universal.

The purpose of the invention is realized by the following technical scheme.

A method for synthesizing a small-size high-dispersion intermetallic compound catalyst material is characterized in that MOFs-derived porous carbon is used as a hard template to realize the control of the size of intermetallic compound nanoparticles; the catalyst material is a MOF-derived carbon-supported platinum-based intermetallic compound;

the method specifically comprises the following steps:

(1) synthesizing an MOF material, namely thermally cracking the MOF material at high temperature under inert gas, and then pickling, drying and grinding for later use;

(2) dissolving a noble metal precursor and a non-noble metal precursor in deionized water or an organic solvent, and ultrasonically dissolving and uniformly mixing; the noble metal precursor comprises acid or salt containing Pt, Pd, Au and Rh; the non-noble metal precursor comprises Fe salt, Co salt, Ni salt or Cu salt; the organic solvent comprises DMF, ethanol or isopropanol;

(3) dipping the product obtained in the step (1) into the solvent obtained in the step (2), immersing the solution into the micro-channels of the carbon material by ultrasonic waves, and then adopting freeze drying or vacuum drying;

(4) roasting the product obtained in the step (3) at high temperature in a reducing atmosphere environment to obtain the MOF carbon-loaded ordered intermetallic compound nanoparticle catalyst Pt_xM/MOFDC。

In the above method, in step (1), the MOF comprises ZIF-8, ZIF-67 or UIO-66.

In the method, in the step (1), the thermal cracking temperature is 900-; the inert gas is helium, argon or high-purity nitrogen.

In the method, in the step (1), the pickling temperature is 60-90 ℃ and the pickling time is 8-12 hours.

In the method, the molar ratio of the noble metal to the non-noble metal in the precursor solution in the step (2) is 3:1, 1:1 or 1: 3.

In the above method, in step (2), when the solvent is deionized water, ethanol or isopropanol, the precious metal precursor is an inorganic acid or an inorganic salt such as chloroplatinic acid, chloropalladic acid, chloroauric acid or ammonium chlororhodate, and the non-precious metal precursor is an inorganic metal salt such as chloride, nitrate or sulfate; when the solvent is DMF, the noble metal precursor is acetylacetone salt, and the non-noble metal precursor is acetylacetone salt or inorganic metal salt.

In the method, in the step (3), the dipping process is to drop the metal precursor solution drop by drop into the MOF-derived carbon uniformly; the ultrasonic mixing time is 0.5-2 hours.

In the above method, in the step (4), the reducing gas is H₂Mixed gas of/Ar and NH₃/He、H₂Mixed gas of/He and NH₃/N₂、H₂/N₂Mixing the gas; the roasting temperature is 650-850 ℃ and the time is 1.5-4 hours.

Ordered Pt_xUse of M/MOF DC in fuel cell catalysts.

Compared with the prior art, the invention has the advantages that:

the product well keeps the original regular polyhedral morphology of the MOF. The MOF derived carbon is simultaneously used as a template and a carbon carrier, the particle size of intermetallic compound particles after high-temperature calcination is effectively controlled by utilizing the limited domain effect of the inner pore channels of the MOF derived carbon, and meanwhile, the porous structure of the MOF derived carbon enables most PtM nano particles to be positioned in the pore channels of porous carbon, so that the problems of easy agglomeration, uneven dispersion and the like of the intermetallic compound nano particles are effectively inhibited, the problems of agglomeration, migration and loss of the PtM nano particles in the operation process of a fuel cell are solved, and the catalytic durability of the material can be effectively improved.

Drawings

FIG. 1 is the ordered Pt prepared in example 1₃XRD pattern of Co/ZIF-8 DC.

FIG. 2 is the ordered Pt prepared in example 1₃TEM image of Co/ZIF-8 DC.

FIG. 3 is the ordered Pt prepared in example 1₃Graph of oxygen reduction performance of Co/ZIF-8 DC.

FIG. 4 is the ordered Pt prepared in example 2₃TEM image of Co/UIO-66 DC.

FIG. 5 is the ordered Pt prepared in example 3₃TEM image of Fe/ZIF-8 DC.

FIG. 6 is the ordered Pt prepared in example 6₃TEM image of Fe/ZIF-8 DC.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto, and may be carried out with reference to conventional techniques for process parameters not particularly noted.