Preparation of platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst and application of platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst in ammoxidation reaction

Abstract

The invention discloses preparation of a platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst and application of the platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst in ammoxidation reaction, relates to the technical field of electro-catalysis, and provides a unique sheet structure of a platinum catalyst and a preparation method of the platinum catalyst compared with the prior art. Due to the special structure and morphology, the composite material has a relatively wide application prospect, shows relatively high catalytic activity, stability and conductivity in ammoxidation reaction, is particularly suitable for ammoxidation reaction in an alkaline medium, and can provide feasible guidance for developing an efficient platinum material electrochemical catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of electrocatalysis, and in particular to the preparation of a quasi-two-dimensional nanosheet catalyst of self-assembled platinum nanoparticles and its application in an ammonia oxidation reaction. Background Art

[0002] The hazards associated with conventional fuels and handling of hydrogen fuels have prompted the consideration of alternative clean and sustainable fuel types. Ammonia has great potential in this task as a direct fuel and hydrogen carrier due to its convenient transportation and low cost. Therefore, the electrochemical ammonia oxidation reaction (AOR) is an important process for utilizing ammonia for energy applications, whether it is ammonia cracking to produce hydrogen or direct power generation with ammonia fuel cells, which has high commercial prospects.

[0003] Most catalysts for ammonia oxidation reactions are based on precious metals, and Pt and its derivatives remain the most studied and best performing AOR electrocatalysts because Pt not only has a low AOR onset overpotential, but also has a high Nads oxidation potential and a low NH2ads dimerization activation energy. These properties make Pt an ideal model electrode for studying AOR, but it has not yet been used on an industrial scale due to its high cost. In order to improve electrocatalytic activity while reducing costs, people continue to explore and find that the performance of electrocatalysts depends largely on their surface morphology, so the manufacture of Pt electrocatalysts with various morphologies has always attracted much attention. Therefore, it becomes crucial to design Pt nanostructures with efficient catalytic activity. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method of a quasi-two-dimensional nanosheet catalyst of self-assembled platinum nanoparticles and its application in an ammonia oxidation reaction. The platinum nanosheet shows relatively excellent catalytic activity, stability and conductivity.

[0005] The technical problem to be solved by the present invention is achieved by adopting the following technical solutions:

[0006] One of the purposes of the present invention is to provide a preparation method of a quasi-two-dimensional nanosheet catalyst self-assembled from platinum nanoparticles, comprising the following steps:

[0007] Dissolve a platinum source, an amide solvent such as N-methyl-2-pyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, polyvinylpyrrolidone, and a surfactant such as dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride in a solvent, and then stir with a magnetic stirrer;

[0008] Then, a reducing agent such as ethylene glycol, formaldehyde, citric acid, anhydrous hemic acid, etc. is added to the mixture, followed by ultrasonic treatment and hydrothermal reaction in a sand bath;

[0009] After the reaction is completed, the mixture is cooled to room temperature, and the obtained substance is washed, centrifuged, and dried to obtain platinum nanosheets;

[0010] The second object of the present invention is to provide a quasi-two-dimensional nanosheet self-assembled from platinum nanoparticles prepared according to the aforementioned preparation method.

[0011] The third object of the present invention is to provide the preparation of the aforementioned platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst and its application in ammonia oxidation reaction.

[0012] The beneficial effects of the present invention are as follows: compared with the prior art, the present invention provides a method for preparing a quasi-two-dimensional nanosheet catalyst self-assembled from platinum nanoparticles, whose controllable sheet morphology gives it a broader application prospect, and exhibits high catalytic activity, stability and conductivity in ammonia oxidation reactions, and is particularly suitable for ammonia oxidation reactions in alkaline media, and can provide practical guidance for the development of high-efficiency platinum material electrochemical catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 and Figure 2 The structural characterization results of the Pt nanosheets sample prepared in Example 1 of the present invention: X-ray diffraction pattern; scanning electron microscope image;

[0014] Figure 3-Figure 8 Performance test results of the Pt nanosheets sample prepared in Example 1 of the present invention and commercial Pt / C in the electrocatalytic ammonia oxidation reaction: Figure 3 AOR curves under different electrolytes with 1 M KOH and 0.1 M NH3·H2O added; Figure 4 These are the AOR curves obtained for Ptnanosheets and Pt / C; Figure 5 is the AOR curve under different NH3·H2O concentrations; Figure 6 is the AOR curve under different KOH concentrations; Figure 7 Current-time diagram at different NH3·H2O concentrations at 655mV overpotential;

[0015] Figure 8 Comparison of the AOR catalytic activity of Pt nanosheets before and after 100 cycles of CV. DETAILED DESCRIPTION

[0016] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments and diagrams.

[0017] The present invention provides a method for preparing a quasi-two-dimensional nanosheet catalyst of self-assembled platinum nanoparticles, comprising the following steps:

[0018] A platinum source, an amide solvent such as N-methyl-2-pyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, polyvinylpyrrolidone, and a surfactant such as dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride are dissolved in a solvent, and then stirred with a magnetic stirrer;

[0019] Then, a reducing agent such as ethylene glycol, formaldehyde, citric acid, anhydrous hemic acid, etc. is added to the mixture, followed by ultrasonic treatment and hydrothermal reaction in a sand bath;

[0020] After the reaction is completed, the mixture is cooled to room temperature, and the obtained material is washed, centrifuged, and dried to obtain platinum nanosheets.

[0021] Preferably, the rotation speed is set at 100-300 rpm, and the time is 6-10 minutes.

[0022] Preferably, the platinum source is potassium chloroplatinate.

[0023] Preferably, the solvent is water.

[0024] Preferably, the ultrasound is for 30 min.

[0025] Preferably, the hydrothermal reaction temperature is room temperature to 80° C., and the reaction time can be 5 to 8 hours.

[0026] The present invention also provides a catalyst of quasi-two-dimensional nanosheets self-assembled from platinum nanoparticles prepared according to the above-mentioned preparation method.

[0027] The present invention further provides the use of the aforementioned platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst in an electrocatalytic ammonia oxidation reaction.

[0028] Preferably, the electrocatalytic ammonia oxidation reaction is an ammonia oxidation reaction in an alkaline medium using 1 M KOH and 0.1 M NH 3 ·H 2 O as electrolytes.

[0029] Example 1

[0030] Preparation of nanosheet catalysts assembled from platinum particles:

[0031] Dissolve 1000-2000 μL potassium chloroplatinate, 400-1000 μL amide solvent such as N-methyl-2-pyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, polyvinylpyrrolidone, and 40-100 μL surfactant such as dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride in 3-6 ml water, and then stir with a magnetic stirrer at a speed of 100-300 rpm for 6-10 minutes.

[0032] Then, 400-1000 μl of a reducing agent such as ethylene glycol, formaldehyde, citric acid, hematoxylin and the like is added to the mixture, followed by ultrasonic treatment and a hydrothermal reaction in a sand bath.

[0033] The obtained mixture was placed in a sand bath at room temperature to 80°C for hydrothermal reaction for 5-8 hours. After cooling to room temperature, it was washed with ethanol for more than 3 times. The washed sample was placed in a vacuum oven for 12 hours. Finally, the catalyst was obtained.

[0034] The structure of the Pt nanosheets sample prepared in Example 1 was characterized. Figure 1 .

[0035] Figure 1 All the diffraction peaks that appear in the sample correspond to those of pure platinum, proving that it is pure platinum; Figure 2 It shows that the Ptnanosheets sample has a sheet-like structural morphology.

[0036] Example 2

[0037] Study on the application of the Pt nanosheets sample prepared in Example 1 as a catalyst in electrocatalytic ammonia oxidation:

[0038] AOR electrocatalytic test was performed on an electrochemical workstation using a standard three-electrode system. A 1M KOH solution containing 0.1M NH3·H2O was used as the electrolyte, a platinum carbon electrode modified with Pt nanosheets was used as the working electrode (5 mg of the Pt nanosheets sample prepared in Example 1 was dispersed in 1000 μL of ethanol containing 10 uL of 5wt% Nafion, and the ink was prepared by ultrasonication for 1 h; then 10 μL of the ink was dropped onto the polished platinum carbon electrode to obtain the working electrode), a platinum wire was used as the counter electrode, and a Hg / HgO electrode was used as the reference electrode.

[0039] At the same time, a control example was set up in which commercial Pt / C was used as a catalyst to replace Pt nanosheets to prepare a working electrode. The Pt content in the Pt / C was 20%, and the other conditions were the same as above.

[0040] like Figure 3 and Figure 4 As shown in the figure, the AOR curves under different electrolytes of 1 M KOH and 0.1 M NH3·H2O as well as the catalytic activities of different catalysts in the AOR process show that the AOR catalytic activity of Pt nanosheets in alkaline media is significantly better than that of Pt / C.

[0041] from Figure 5 and Figure 6 As shown, the AOR curves under different NH3·H2O concentrations and different KOH concentrations respectively;

[0042] from Figure 7 It can be seen that Pt nanosheets are stable in alkaline medium.

[0043] from Figure 8 It can be seen that the AOR catalytic activity of Pt nanosheets in alkaline medium is higher than that of Pt / C even after 100 cycles of CV.

[0044] In summary, the AOR catalytic activity of the Pt nanosheets prepared in the present invention in alkaline medium is better than that of the commercial Pt / C catalyst and has good stability.

[0045] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a quasi-two-dimensional nanosheet catalyst self-assembled from platinum nanoparticles, characterized in that: The following steps are involved: Dissolve a platinum source, an amide solvent such as N-methyl-2-pyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, polyvinylpyrrolidone, and a surfactant such as dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride in a solvent, and then stir with a magnetic stirrer; Then, a reducing agent such as ethylene glycol, formaldehyde, citric acid, anhydrous hemic acid, etc. is added to the mixture, followed by ultrasonic treatment and hydrothermal reaction in a sand bath; After the reaction is completed, the mixture is cooled to room temperature, and the obtained material is washed, centrifuged, and dried to obtain platinum nanosheets.

2. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The platinum source is potassium chloroplatinate.

3. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The stirring speed is set at 100-300 rpm and the time is 6-10 minutes.

4. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The solvent is water.

5. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The ultrasonication lasts for 30 min.

6. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The hydrothermal reaction temperature is room temperature-80°C and the reaction time can be 5-8h.

7. The method for preparing the quasi-two-dimensional nanosheet catalyst self-assembled by platinum nanoparticles according to claim 1, characterized in that: The washing is ethanol washing.

8. A quasi-two-dimensional nanosheet catalyst self-assembled by platinum nano-ions prepared according to the preparation method according to any one of claims 1 to 7.

9. The use of the platinum nanoparticle self-assembled quasi-two-dimensional nanosheet catalyst in an electrocatalytic ammonia oxidation reaction according to claim 8, characterized in that: The electrocatalytic ammonia oxidation reaction is an ammonia oxidation reaction in an alkaline medium using 1M KOH as an electrolyte.

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