A porous platinum nanotube composite carbon nanomaterial, a preparation method and application thereof in an anode catalyst of a methanol fuel cell

Abstract

The application relates to a kind of porous platinum nanotube composite carbon nanomaterial, preparation method and its application in methanol fuel cell anode catalyst, belong to methanol fuel cell anode catalyst material technical field.PVP, PAA, sodium tellurite, ammonia and water are mixed uniformly, after reaction in hydrothermal kettle, cooling is carried out, and after precipitation with acetone, tellurium nanotube is obtained by centrifugation;Subsequently, tellurium nanotube is dispersed into methanol solution and zinc nitrate and dimethyl imidazole methanol solution are added, to obtain tellurium nanotube loaded with ZIF-8 nanoparticles;On this basis, redox reaction is carried out by using chloroplatinic acid, and porous carbon loaded porous platinum nanotube material is obtained after high-temperature anaerobic annealing.The nanomaterial prepared by the application has high-quality porous structure, and the length-diameter ratio of the material, the graphitization degree of the loaded carbon and the pore structure of the material can be controlled by experimental parameters.The material shows excellent catalytic activity for electrochemical methanol oxidation reaction, has good stability and good process repeatability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of anode catalyst materials of methanol fuel cells, and particularly relates to a porous platinum nanotube composite carbon nanomaterial, a preparation method and application thereof in anode catalysts of methanol fuel cells. BACKGROUND

[0002] The energy structure mainly based on fossil energy such as coal, oil and natural gas has caused serious problems such as energy shortage, resource contention, climate change and environmental pollution, which affect and threaten the survival of human beings and the development of society. Among many energy storage devices, methanol fuel cells, as a representative of low-temperature fuel cells, have the advantages of high power generation efficiency, strong reliability and environmental friendliness, and have attracted widespread attention. As is known, the catalytic activity of a catalyst is mainly determined by the micro-physical structure of a nanomaterial. Therefore, the morphology control of a nanomaterial is an important means to improve the catalytic performance.

[0003] One-dimensional nanomaterials with a porous structure usually have good catalytic activity due to their high specific surface area and more active sites. However, in a one-step synthesis process, it is difficult to directionally prepare one-dimensional nanomaterials by controlling the nucleation and growth of nanomaterials. At present, people mostly use template methods to prepare nanomaterials with a certain morphology. Generally, the template method can be divided into three types: hard template method, soft template method and sacrificial template method. Among them, the core advantage of the sacrificial template method is that the sacrificial template can participate in the redox reaction as a reactant, thereby omitting the template elimination step, and thus realizing the controlled product obtained by using mild synthesis conditions and a simple synthesis process.

[0004] Tellurium nanowires are often used as sacrificial templates for synthesizing one-dimensional nanomaterials due to their simple preparation method, large-scale synthesis and low cost. However, the currently used tellurium nanowires have a small diameter and an ultra-long length, and the controllability of the morphology is poor, which leads to the corresponding poor controllability of platinum nanowire materials. In addition, in the redox reaction of platinum replacement, it is usually necessary to add polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB) and other surface stabilizers again, which reduces the active sites and the catalytic effect of the surface active agents adsorbed on the surface of the catalyst. SUMMARY

[0005] The present application aims to solve the problems in the background art, and provides a porous platinum nanotube composite carbon nanomaterial, a preparation method and application thereof as an anode catalyst of a methanol fuel cell. The preparation process of the present application is simple, environmentally friendly, low in cost and the material has high catalytic activity and stability, solving the problems of uncontrollable morphology of tellurium nanowires and the need to add surface stabilizers in the redox reaction of platinum replacement in the existing preparation methods.

[0006] The application discloses a preparation method of a porous platinum nanotube composite carbon nanomaterial.

[0007] a. Polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), sodium tellurite and water are uniformly mixed, 25% ammonia water by mass fraction is added dropwise into the mixture and uniformly stirred, and then the mixture is reacted at 150-220 DEG C in a hydrothermal kettle for 2-6 hours, and then the mixture is cooled, precipitated by acetone and centrifuged to obtain tellurium nanotubes; the tellurium nanotubes are dispersed into methanol to obtain a tellurium nanotube methanol solution, and the concentration of the tellurium nanotubes is 5-20 mg / mL; wherein, the molar ratio of PVP to PAA is 1:0.1-0.5, the concentration of PVP is 0.01-0.1 g / mL; the concentration of the sodium tellurite aqueous solution is 1-20 mmol / L, and the volume ratio of water, ammonia water and acetone is 1:0.05-0.8:1;

[0008] b. Dimethylimidazole is added into the methanol solution, and the mixture is stirred and dissolved to obtain a dimethylimidazole methanol solution, and the concentration of the dimethylimidazole is 0.1-1.5 mol / L;

[0009] c. Zinc nitrate is added into 200-250 mL of the tellurium nanotube methanol solution obtained in step a and stirred and dissolved, and the concentration of the zinc nitrate is 0.01-0.8 mol / L; and then an equal volume of the dimethylimidazole methanol solution obtained in step b is added into the mixture, and the mixture is stirred and reacted at room temperature for 1.5-3.0 hours to obtain a Te-zif-8 composite material solution;

[0010] d. The Te-zif-8 composite material solution obtained in step c is centrifuged, the centrifuged product is washed by ethanol and then dispersed into 200-250 mL of ethylene glycol, and the concentration is 5-20 mg / mL; then 25-500 μL of 0.05-0.3 g / mL chloroplatinic acid aqueous solution is added, and the mixture is reacted at 70-90 DEG C for 1.5-3.0 hours; finally, the unreacted substances in the reaction product are removed by centrifugation, and the centrifuged product is washed by ethanol and dried;

[0011] e. The dried powder obtained in step d is annealed at 600-1000 DEG C under nitrogen protection for 1.5-3.0 hours, so that the porous platinum nanotube composite carbon nanomaterial is obtained.

[0012] The porous platinum nanotube composite carbon nanomaterial prepared by the application can be used as an anode catalyst material of a methanol fuel cell, a carrier solution is prepared by mixing water, ethanol and a Nafion (5.0wt%) aqueous solution in a volume ratio of 20:20:0.075; 0.1-0.3 milligrams of the porous platinum nanotube composite carbon nanomaterial prepared by the application is dispersed in 1 milliliter of the carrier solution under ultrasonic; then 5-10 μL of the carrier solution containing the porous platinum nanotube composite carbon nanomaterial is dropped on the surface of a glassy carbon electrode, and the test is carried out after complete drying in air; a commercial platinum carbon Pt / C electrode with a platinum mass of 20wt% is used as a performance reference for testing, and the test results are shown in Figs. 1-3. Figure 5 、 6 ,

[0013] Compared with the prior art, the application has the following beneficial effects:

[0014] 1. The synthesis method of the material has high maturity, strong universality and good process repeatability. The product is high-quality nanowires, and has relatively uniform morphology and size, is relatively safe, and has relatively high operability for large-scale synthesis. The length-diameter ratio of the prepared porous platinum nanotube can be controlled, and a hollow structure can be prepared. In addition, the prepared material also has the advantages that the porous structure can be controlled, the carbon loading in the overall material can be controlled, and the porous structure and graphitization degree of the carbon can be controlled.

[0015] 2. The new tellurium nanotube as a template material provides more choices for the template synthesis of other materials, and expands the application range of the tellurium nanotube as a synthesis template. The prepared porous platinum nanotube composite carbon nanomaterial belongs to a new type of anode catalyst material of a methanol fuel cell.

[0016] 3. The prepared porous platinum nanotube composite carbon as an anode catalyst material of a methanol fuel cell has high catalytic performance and stability. In a mixed solution of H2SO4 (1 mol / L) and methanol (1 mol / L), the catalytic activity of the porous platinum catalyst is higher than that of a commercial platinum carbon. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 is a scanning electron microscope (SEM) photo of the tellurium nanotube prepared in step a of Example 1 of the application.

[0018] Figure 2 Fig. 3 is an element distribution curve of the Te-zif-8 composite material prepared in Example 1 of the application.

[0019] Figure 3 Fig. 4 is a transmission electron microscope (TEM) photo of the Te-zif-8 composite material prepared in Example 1 of the application.

[0020] Figure 4This is a scanning electron microscope image of the Te-zif-8 composite material obtained in Example 1 of this invention.

[0021] Figure 5 This is the mass activity curve of the porous platinum nanotube composite carbon nanomaterial prepared in the embodiments of the present invention (mass activity is the current magnitude per unit mass). The horizontal axis represents the potential, and the vertical axis represents the mass activity. The scanning potentials are -0.05~1.05V and 1.05~-0.05V.

[0022] Figure 6 shows the area activity curves (area activity is the current per unit area) of the porous platinum nanotube composite carbon nanomaterials prepared in the embodiments of the present invention. The horizontal axis represents the potential, and the vertical axis represents the area activity. The scanning potentials are -0.05~1.05V and 1.05~-0.05V.

[0023] like Figure 1 As shown, the Te nanowires have uniform morphology and size, with a length of 800 nm to 2 μm and a diameter of 20 to 50 nm.

[0024] like Figure 2 As shown, the composite material contains Te, N and C elements, and no impurity elements are present.

[0025] like Figure 3 As shown, the Zif-8 material loaded on the Te nanowires consists of particles of 20~40 nm in size.

[0026] like Figure 4 As shown, the Pt nanowires have a long rod-like morphology.

[0027] like Figure 5 , 6 As shown, it can be seen that the samples prepared in Examples 1, 2, and 3 are superior to commercial platinum-carbon Pt / C in both mass activity and surface activity. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to embodiments and accompanying drawings. This is intended only to provide a better understanding of the invention and not to limit the scope of protection of the invention.

[0029] Example 1

[0030] a. Mix 2g PVP, 0.4g PAA, 200mg sodium tellurite and 100mL water to obtain a mixed solution. Then add 8mL of 25% ammonia water dropwise to the mixed solution. After stirring evenly, react in a hydrothermal reactor at 200℃ for 4 hours and then cool. After precipitation with 100mL acetone, centrifuge to obtain tellurium nanotubes. Disperse the tellurium nanotubes in methanol to obtain a tellurium nanotube methanol solution with a tellurium nanotube concentration of 10 mg / mL.

[0031] b. Dimethylimidazole was added to the methanol solution, stirred and dissolved to prepare a dimethylimidazole methanol solution with a concentration of 0.8 mol / L.

[0032] c. Zinc nitrate was added to 200 mL of the tellurium nanotube methanol solution, stirred and dissolved, the concentration of zinc nitrate was 0.1 mol / L, and an equal volume of 200 mL of the dimethylimidazole methanol solution was poured into it, and stirred at room temperature for 2 hours to obtain a Te-zif-8 composite material solution.

[0033] d. The Te-zif-8 composite material solution was centrifuged, the centrifuged product was washed with ethanol for multiple times, and then dispersed in 200 mL of ethylene glycol with a concentration of 10 mg / mL; 0.05 mL of 0.05 g / mL chloroplatinic acid aqueous solution was added, and reacted at 80°C for 2 hours; the unreacted substances in the reaction product were removed by centrifugation, and the centrifuged product was washed with ethanol and dried.

[0034] e. The dried powder obtained in step d was annealed at 800°C under nitrogen protection for 2 hours to obtain the porous platinum nanotube composite carbon nanomaterial powder of the application, the product mass was 1.35 g, the nanowire length was 500 nm-2 μm, and the diameter was 10-80 nm.

[0035] Example 2

[0036] a. 2 g of PVP, 0.4 g of PAA, 200 mg of sodium tellurite and 100 mL of water were uniformly mixed, and then 8 mL of 25% ammonia water was added dropwise into the mixed solution, which was stirred uniformly, and then reacted in a hydrothermal kettle at 200°C for 4 hours, and then cooled, precipitated with 100 mL of acetone, and centrifuged to obtain tellurium nanotubes, which were then dispersed in methanol to obtain a tellurium nanotube methanol solution with a concentration of 10 mg / mL.

[0037] b. Dimethylimidazole was added to the methanol solution, stirred and dissolved to prepare a dimethylimidazole methanol solution with a concentration of 0.8 mol / L.

[0038] c. Zinc nitrate was added to 200 mL of the tellurium nanotube methanol solution, stirred and dissolved, the concentration of zinc nitrate was 0.1 mol / L, and an equal volume of 200 mL of the dimethylimidazole methanol solution was poured into it, and stirred at room temperature for 2 hours to obtain a Te-zif-8 composite material solution.

[0039] d. The Te-zif-8 composite solution was centrifuged, the centrifugal product was washed with ethanol for multiple times, and then was dispersed in 200 mL of ethylene glycol at a concentration of 10 mg / mL; 0.1 mL of 0.05 g / mL chloroplatinic acid aqueous solution was added, and the mixture was reacted at 80°C for 2 hours. The unreacted substances in the reaction product were removed by centrifugation, and the centrifugal product was washed with ethanol and dried.

[0040] e. The dry powder product obtained in d was annealed at 800°C for 2 hours under nitrogen protection to obtain a porous platinum nanotube composite carbon nanomaterial powder, the product mass was 1.42 g, the nanowire length was 500 nm-2 μm, and the diameter was 10-80 nm.

[0041] Example 3

[0042] a. 2 g of PVP, 0.4 g of PAA, 200 mg of sodium tellurite, and 100 mL of water were uniformly mixed, 8 mL of 25% ammonia water was added dropwise into the mixed solution, the mixture was uniformly stirred, and then was reacted at 200°C for 4 hours in a hydrothermal kettle, and then was cooled, precipitated with 100 mL of acetone, and centrifuged to obtain tellurium nanotubes. The tellurium nanotubes were dispersed in methanol to obtain a tellurium nanotube methanol solution, and the concentration of the tellurium nanotubes was 10 mg / mL.

[0043] b. Dimethyl imidazole was added into the methanol solution, and was stirred and dissolved to prepare a dimethyl imidazole methanol solution, and the concentration of the solution was 0.8 mol / L.

[0044] c. Zinc nitrate was added into 200 mL of the tellurium nanotube methanol solution and was stirred and dissolved to obtain a solution with a concentration of 0.1 mol / L. An equal volume of 200 mL of the dimethyl imidazole methanol solution was poured into the solution, and the mixture was stirred at room temperature for 2 hours to obtain a Te-zif-8 composite solution.

[0045] d. The Te-zif-8 composite solution was centrifuged, the centrifugal product was washed with ethanol for multiple times, and then was dispersed in 200 mL of ethylene glycol at a concentration of 10 mg / mL; 0.2 mL of 0.05 g / mL chloroplatinic acid aqueous solution was added, and the mixture was reacted at 80°C for 2 hours. The unreacted substances in the reaction product were removed by centrifugation, and the centrifugal product was washed with ethanol and dried.

[0046] e. The dry powder product obtained in d was annealed at 800°C for 2 hours under nitrogen protection to obtain a porous platinum nanotube composite carbon nanomaterial powder, the product mass was 1.56 g, the nanowire length was 500 nm-2 μm, and the diameter was 10-80 nm.

[0047] Example 4

[0048] The porous platinum nanotube composite carbon nanomaterial prepared by the application is used as an anode catalyst material of a methanol fuel cell, a carrier solution is prepared by mixing water, ethanol and a Nafion (5.0 wt%) aqueous solution in a volume ratio of 20:20:0.075; 0.2 mg of the porous platinum nanotube composite carbon nanomaterial is dispersed in 1 ml of the carrier solution under ultrasonic; then 6 μL of the carrier solution containing the porous platinum nanotube composite carbon nanomaterial is dropped on the surface of a glassy carbon electrode, and the porous platinum nanotube composite carbon nanomaterial is completely dried in air and then tested; a commercial platinum carbon Pt / C electrode with a platinum mass of 20 wt% is used as a performance reference and is tested together.

Claims

1. A method for preparing a porous platinum nanotube composite carbon nanomaterial, comprising the following steps: a. mixing polyvinylpyrrolidone, polyacrylic acid, sodium tellurite and water uniformly, adding 25% ammonia water dropwise into the mixture and stirring uniformly, then reacting at 150-220°C in a hydrothermal kettle for 2-6 hours, cooling, precipitating with acetone, centrifuging to obtain tellurium nanotubes; dispersing the tellurium nanotubes into methanol to obtain a tellurium nanotube methanol solution, the concentration of the tellurium nanotubes being 5-20 mg / mL; wherein, The molar ratio of polyvinylpyrrolidone and polyacrylic acid is 1:0.1-0.5, the concentration of PVP is 0.01-0.1 g / mL; the concentration of sodium tellurite aqueous solution is 1-20 mmol / L, and the volume ratio of water, ammonia water and acetone is 1:0.05-0.8:1; b. Dimethylimidazole is added to a methanol solution and stirred to dissolve, obtaining a dimethylimidazole methanol solution, the concentration of dimethylimidazole being 0.1-1.5 mol / L; c. Zinc nitrate is added to 200-250 mL of the tellurium nanotube methanol solution obtained in step a and stirred to dissolve, the concentration of zinc nitrate being 0.01-0.8 mol / L; an equal volume of the dimethylimidazole methanol solution obtained in step b is added, and the mixture is stirred at room temperature for 1.5-3.0 hours, obtaining a Te-zif-8 composite material solution; d. The Te-zif-8 composite material solution obtained in step c is centrifuged, the centrifuged product is washed with ethanol and then dispersed in 200-250 mL of ethylene glycol, the concentration being 5-20 mg / mL; then 25-500 μL of 0.05-0.3 g / mL chloroplatinic acid aqueous solution is added, and the mixture is reacted at 70-90°C for 1.5-3.0 hours; finally, the unreacted substances in the reaction product are removed by centrifugation, and the centrifuged product is washed with ethanol and dried; e. The dried powder obtained in step d is annealed at 600-1000°C for 1.5-3.0 hours under nitrogen protection, obtaining a porous platinum nanotube composite carbon nanomaterial.

2. A porous platinum nanotube composite carbon nanomaterial, characterized in that: The porous platinum nanotube composite carbon nanomaterial is prepared by the method of claim 1.

3. Use of the porous platinum nanotube composite carbon nanomaterial of claim 2 as an anode catalyst for a methanol fuel cell.

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