CN108054391B

CN108054391B - Synthesis method and application of dendritic Pd nanocrystal catalyst

Info

Publication number: CN108054391B
Application number: CN201711311299.2A
Authority: CN
Inventors: 袁强; 马腾越
Original assignee: Guizhou University
Current assignee: Guizhou University
Priority date: 2017-12-11
Filing date: 2017-12-11
Publication date: 2021-03-30
Anticipated expiration: 2037-12-11
Also published as: CN108054391A

Abstract

The invention discloses a preparation method of a dendritic Pd nano-crystal catalyst, which is characterized by comprising the following steps: adding a surfactant and a reducing agent into water, and stirring for 5-15 minutes at room temperature, wherein the mass ratio of the surfactant to the reducing agent is 3: 1-1: 3; the added water quantity needs to completely dissolve the surfactant and the reducing agent; (2) respectively adding metal platinum salt precursor solutions into the mixed solution obtained in the step (1), wherein the concentration of the metal salt precursor solutions is 0.1-1 mol/L, the ratio of the mixed solution to the total volume of the metal precursor solutions is 25: 1-35: 1, the metal palladium salt precursor solutions are potassium chloropalladate, chloropalladate or sodium salts of chloropalladate, and stirring at room temperature for 5-15 minutes; (3) stirring the mixed solution obtained in the step (2) for 5-20 minutes at room temperature, and reacting in a three-neck flask for 2-4 hours, wherein the temperature is controlled at 70-100 ℃; (4) and (4) cooling the product obtained in the step (3), washing, and performing centrifugal separation to obtain the dendritic Pd nano-crystal catalyst.

Description

Synthesis method and application of dendritic Pd nanocrystal catalyst

Technical Field

The invention relates to the field of formic acid fuel cell catalysts, in particular to synthesis and application of a dendritic Pd nanocrystal catalyst.

Background

The fuel cell has high energy conversion rate and little environmental pollution, is beneficial to reducing the overuse of the traditional fossil fuel and protecting the global environment, and can be used as an ideal power source in the future, so the fuel cell is widely concerned by scientists of all countries in the world, and therefore, all countries in the world invest a great deal of manpower, material resources and financial resources to research. The direct formic acid fuel cell has great application prospect in the aspects of power supply of electric automobiles and mobile equipment. In the catalysis of formic acid, compared with Pt metal, Pd metal has the advantages of low price and strong catalytic performance, and the preparation methods of the existing catalysts comprise a high-temperature alloying method, a gas-phase reduction method, a sol method, a B.nnemann method, a liquid-phase reduction method, an alternative microwave in-situ reduction method, a solid-phase reaction method, a co-sputtering method and the like. The research on the catalyst is mainly carried out from the aspects of reducing agent, surfactant, morphology, dispersity, structure and the like, so that the catalyst with high catalytic activity and good stability is prepared. However, the existing Pd nano-catalyst with controllable morphology is mainly synthesized by using a high-pressure reaction kettle, and the synthesis temperature is usually higher than 100 ℃. Such methods are disadvantageous for operation and subsequent practical production applications.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: provides a dendritic Pd nano-crystal catalyst, which enhances the catalytic activity of the catalyst on formic acid.

The technical scheme of the invention is as follows: a preparation method of a dendritic Pd nano-crystal catalyst comprises the following preparation steps of (1) adding a surfactant and a reducing agent into water together, stirring for 5-15 minutes at room temperature, wherein the mass ratio of the surfactant to the reducing agent is 3: 1-1: 3; the added water quantity needs to completely dissolve the surfactant and the reducing agent; (2) respectively adding metal platinum salt precursor solutions into the mixed solution obtained in the step (1), wherein the concentration of the metal salt precursor solutions is 0.1-1 mol/L, the ratio of the mixed solution to the total volume of the metal precursor solutions is 25: 1-35: 1, the metal palladium salt precursor solutions are potassium chloropalladate, chloropalladate or sodium salts of chloropalladate, and stirring at room temperature for 5-15 minutes; (3) stirring the mixed solution obtained in the step (2) for 5-20 minutes at room temperature, and reacting in a three-neck flask for 2-4 hours, wherein the temperature is controlled at 70-100 ℃; (4) and (4) cooling the product obtained in the step (3), washing, and performing centrifugal separation to obtain the dendritic Pd nano-crystal catalyst.

The aqueous solution in the step (1) is ultrapure water, the stirring time is 10 minutes, and the mass ratio of the surfactant to the reducing agent is 3.2: 1.1.

The surfactant in the step (1) is glycine or CTAC; the reducing agent is ascorbic acid.

The concentration of the metal salt precursor solution in the step (2) is 0.1mol/L, and the metal palladium salt precursor solution is sodium chloropalladate.

Stirring the mixture at room temperature for 10 minutes in the step (3), and reacting the mixture in a three-neck flask for 3 hours, wherein the temperature is controlled to be 95 ℃.

And (4) naturally cooling, washing for three times, and centrifugally separating for four times to obtain the dendritic Pd nano-crystal.

The invention has the beneficial effects that: the dendritic Pd nano-crystal catalyst prepared by the invention has the advantages of simple operation, environmental friendliness and low requirement on equipment conditions, and the obtained dendritic Pd nano-crystal catalyst has the advantages of good dispersity, uniform particle size, excellent catalytic performance on formic acid and the like.

The invention researches and obtains a dendritic Pd nano-crystal catalyst, which better enhances the formic acid oxidation catalytic activity of the catalyst, and the catalytic activity is 0.1M HClO₄+0.5MHCOOH, the current value of the mass activity peak of the catalytic formic acid is 3.3A mg^-10.36A mg over commercial Pd black^-19.1 times higher; at 0.1M H₂SO₄+0.5MHCOOH, the current value of the mass activity peak of the catalytic formic acid is 1.08A mg^-10.12A mg over commercial Pd black^-19.0 times higher.

Drawings

FIG. 1 is a diagram of a dendritic Pd nanocrystal catalyst as observed by high resolution transmission electron microscopy;

FIG. 2 is a diagram of a dendritic Pd nanocrystal catalyst as observed by high resolution transmission electron microscopy;

FIG. 3 shows dendritic Pd nanocrystal catalysts and commercial Pd black at 0.1MHClO₄Cyclic voltammogram in +0.5MHCOOH solution;

FIG. 4 shows dendritic Pd nanocrystal catalysts and commercial Pd black at 0.1MH₂SO₄Cyclic voltammogram in +0.5MHCOOH solution;

FIG. 5 shows dendritic Pd nanocrystal catalysts and commercial Pd black at 0.1MHClO₄I-t curve at 0.1V in +0.5MHCOOH solution;

FIG. 6 shows dendritic Pd nanocrystal catalysts and commercial Pd black at 0.1MH₂SO₄I-t curve at 0.1V in +0.5MHCOOH solution;

FIG. 7 is a high resolution transmission electron microscope observation of a Pd dendritic nanocrystal catalyst of the reverse example;

FIG. 8 is a reverse example of a Pd dendritic nanocrystal catalyst at 0.5MH₂SO₄+0.5MHCOOH solution.

Detailed Description

Example 1

(1) Adding a surfactant and a reducing agent into the aqueous solution according to the mass ratio of 3:1, and stirring for 10 minutes; the surfactant is CTAC, and the reducing agent is ascorbic acid;

(2) adding a chloroplatinic acid solution into the mixed solution (14.5 mL) in the step (1) to obtain a solution with the concentration of 0.1mol/L, wherein the mixed solution is yellow in color, and stirring at room temperature for 10 minutes;

(3) transferring the solution obtained in the step (2) into a three-neck flask, and reacting for 3 hours at the temperature of about 95 ℃;

(4) the obtained product is centrifuged, washed by alcoholic solution for 3 times, dispersed and stored in the alcoholic solution, and has good dispersibility and catalytic activity.

Example 2

(1) Adding a surfactant and a reducing agent into the aqueous solution according to the mass ratio of 2:1, and stirring for 15 minutes; the surfactant is glycine, and the reducing agent is ascorbic acid;

(4) the obtained product is centrifuged, washed by alcoholic solution for 3 times, dispersed and stored in the alcoholic solution, and has good dispersibility and good catalytic activity.

Comparative example 1

(1) Mixing Na₂PdCl₄, CTAB, Ni(ac)₂And ascorbic acid were added to 20mL of water to give concentrations of 2.5X 10, respectively⁻⁴ M, 1.5 × 10⁻² M, 1.0 × 10⁻⁵ M, and 2.5 × 10⁻³M。

(2) The reactor was placed in a 30 ℃ water bath and heated for 2 hours.

(3) The standing temperature was raised to 60 ℃ and heated for 1.5 hours.

(4) The product obtained is centrifuged and washed several times with an aqueous alcohol solution.

(5) The sample was dried under vacuum at 60 ℃.

(6) In an ozone environment, the sample was irradiated with ultraviolet light for several hours to remove CTAB.

As can be seen by comparison with comparative example 1, the comparative example uses expensive Ni (ac)₂The cost is increased, the operation steps are more, and the post sample processing method is complex.

FIG. 1 is a projection electron microscope of the catalyst obtained in the example, and it can be seen that the dendritic Pd crystal nano-catalyst is relatively uniform in size.

FIG. 2 is a high resolution projection electron microscope conducted on the catalyst obtained in the example, which shows that the surface morphology of the dendritic Pd crystal nano-catalyst is uniform and is composed of platelets.

FIG. 3 shows the Pd dendritic catalyst obtained in the example and the commercial Pd black at 0.1MHClO₄The cyclic voltammogram of the catalytic formic acid in +0.5MHCOOH solution shows that the peak current value of dendritic Pd is the highest and is 3.3A mg^-19.1 times that of commercial Pd black under equivalent test conditions.

FIG. 4 shows the Pd dendritic catalyst obtained in the example and commercial Pd black at 0.1MH₂SO₄The cyclic voltammogram of the catalytic formic acid in +0.5MHCOOH solution shows that the peak current value of dendritic Pd is the highest and is 1.1A mg^-19 times that of commercial Pd black under equivalent test conditions.

FIG. 5 shows the catalyst obtained in the example and a commercial Pd black at 0.1MHClO₄The i-t curve is tested under the condition of 0.1V in +0.5MHCOOH solution, the test time is 3600s, and the result shows that the peak current value of the dendritic Pd crystal catalyst at 3600s is always higher than that of the commercial Pd black, and the stability is better than that of the commercial Pd black.

FIG. 6 shows the catalyst obtained in the example and commercial Pd black at 0.1MH₂SO₄The i-t curve is tested under the condition of 0.1V in +0.5MHCOOH solution, the test time is 3600s, and the result shows that the peak current value of the dendritic Pd crystal catalyst at 3600s is always higher than that of the commercial Pd black, and the stability is better than that of the commercial Pd black.

FIG. 7 is a high resolution projection electron microscope conducted on the Pd DN catalyst obtained in the reverse example, which shows that the morphology size is not uniform.

FIG. 8 (b) is a graph of Pd dendritic catalyst at 0.5MH obtained in comparative example₂SO₄The mass activity in +0.5MHCOOH was 0.178mA/mg, which is much lower than the mass activity of dendritic Pd in the present patent application (1.1A/mg).

Claims

1. A preparation method of a dendritic Pd nano-crystal catalyst is characterized by comprising the following steps: adding a surfactant and a reducing agent into water, and stirring for 5-15 minutes at room temperature, wherein the mass ratio of the surfactant to the reducing agent is 3: 1-1: 3; the added water quantity needs to completely dissolve the surfactant and the reducing agent; (2) respectively adding metal palladium salt precursor solutions into the mixed solution obtained in the step (1), wherein the concentration of the metal palladium salt precursor solutions is 0.1-1 mol/L, the ratio of the total volume of the mixed solution to the metal palladium salt precursor solutions is 25: 1-35: 1, the metal palladium salt precursor solutions are potassium chloropalladate, chloropalladate or sodium salts of chloropalladate, and stirring at room temperature for 5-15 minutes; (3) stirring the mixed solution obtained in the step (2) for 5-20 minutes at room temperature, and reacting in a three-neck flask for 2-4 hours, wherein the temperature is controlled at 70-100 ℃; (4) cooling the product obtained in the step (3), washing, and performing centrifugal separation to obtain the dendritic Pd nano-crystal catalyst; the surfactant in the step (1) is glycine or CTAC; the reducing agent is ascorbic acid.

2. The method of preparing a dendritic Pd nanocrystal catalyst as recited in claim 1, wherein: the water in the step (1) is ultrapure water, the stirring time is 10 minutes, and the mass ratio of the surfactant to the reducing agent is 3.2: 1.1.

3. The method of preparing a dendritic Pd nanocrystal catalyst as recited in claim 1, wherein: the concentration of the metal palladium salt precursor solution in the step (2) is 0.1mol/L, and the metal palladium salt precursor solution is sodium chloropalladate.

4. The method of preparing a dendritic Pd nanocrystal catalyst as recited in claim 1, wherein: stirring the mixture at room temperature for 10 minutes in the step (3), and reacting the mixture in a three-neck flask for 3 hours, wherein the temperature is controlled to be 95 ℃.

5. The method of preparing a dendritic Pd nanocrystal catalyst as recited in claim 1, wherein: and (4) naturally cooling, washing for three times, and centrifugally separating for four times to obtain the dendritic Pd nano-crystal.