WO2021088959A1 - Ptag nanocrystal having porous double hollow sphere structure, and preparation method and application thereof - Google Patents

Abstract

A PtAg nanocrystal having a porous double hollow sphere structure, a preparation method therefor, and application of the material as a methanol oxidation anode catalyst. The preparation method comprises: taking Pt salt and Ag salt as metal precursors, taking N'N-methylenebisacrylamide as a structure-directing agent, adding a reducing agent and performing a one-step hydrothermal reaction to obtain the PtAg nanocrystal. The obtained porous double hollow sphere PtAg nanocrystal, as a methanol oxidation anode catalyst, has the advantages of excellent electrocatalytic activity, stability and the like.

Description

PtAg nanocrystal with porous double hollow sphere structure and preparation method and application thereof

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on November 7, 2019, the application number is 201911080312.7, and the invention title is "A PtAg nanocrystal with a porous double hollow sphere structure and its preparation method and application". The entire content is incorporated into this application by reference.

Technical field

The invention relates to a method for preparing PtAg nanocrystals with a porous double hollow sphere structure, the material obtained therefrom, and the application of the material as an anode catalyst for methanol oxidation, belonging to the technical field of Pt-based alloy nanocrystals.

Background technique

Proton Electrolyte Membrane Fuel Cell (PEMFC) is a new energy device with great application prospects in the 21st century. In addition to the general advantages of fuel cells, such as high power generation efficiency and low environmental pollution, PEMFC also has potential Quick start at room temperature, no electrolyte loss, high specific power and long life. However, the key materials and key technologies of PEMFC still need further breakthroughs, and at the same time, the cost needs to be greatly reduced, which makes it unable to be further commercialized. Catalysts are the key reason for the high cost of fuel cells. During the operation of the battery, efficient catalysts can effectively reduce electrode polarization, thereby improving the voltage and performance of the battery. The ideal PEMFC catalyst usually has the following characteristics: ①High catalytic activity, high catalytic selectivity, more catalytic active sites and better anti-poisoning ability; ②High stability, good corrosion resistance and Anti-oxidation ability; ③A suitable carrier has good conductivity, mass transfer and corrosion resistance, and can produce beneficial interactions with metals; ④Low cost. At present, precious metal Pt is the most commonly used fuel cell catalyst. Compared with other metals, Pt has the advantages of high activity and high stability. However, Pt reserves are scarce and expensive. In the long run, reduce the amount of Pt and develop other technologies. A low-cost catalyst is very important to reduce the cost of PEMFC.

Pt has been widely accepted as the most effective methanol oxidation reaction (MOR) catalyst. However, how to improve the efficiency of Pt catalysts, one of the ways to solve the problem is to combine Pt with other transition metals to form a uniform Pt-based alloy catalyst, such as : PtCu, PtAg, PtCo, PtMn, PtRu and PtNi, etc. Compared with the corresponding single-component, the increase in catalytic activity can be attributed to the bifunctional mechanism and electronic effects between Pt and other metals. However, the formation of Pt-based alloys inevitably leads to the reduction of active Pt atoms on the catalyst surface. Therefore, an ideal Pt-based alloy catalyst should have the characteristics of Pt-rich surface.

In addition to chemical composition, the catalytic performance of Pt-based catalysts also depends on their surface morphology or surface structure. Porous Pt-based nanostructures have been proved to be important catalysts for electrochemical energy conversion due to their excellent physical and chemical properties. For example: (1) The porous structure provides a large enough space for the landing of active species. Provides a short diffusion path for the reactants and products; (2) The special porous structure can effectively inhibit the Ostwald ripening effect, thereby improving the electron transfer between the solid band gaps and promoting the substrate molecules. Mass transfer; (3) The double hollow sphere structure has the advantages of large specific surface area, small surface energy, stable structure, etc., which can provide more active sites for electrocatalytic reactions and has better catalytic stability.

However, the existing porous Pt-based catalysts also have some defects, such as few active sites and unstable structure.

Summary of the invention

The purpose of the present invention is to propose a PtAg nanocrystal with a porous double hollow sphere structure and its preparation method and application. The catalyst prepared by the present invention through a simple and efficient one-step hydrothermal method exhibits excellent performance in methanol oxidation reaction (MOR). Electrocatalytic activity and stability to meet the requirements of application and development in related fields.

In order to achieve the above purpose of the invention, the present invention adopts the following technical solutions:

A method for preparing PtAg nanocrystals, comprising using Pt salt and Ag salt as metal precursors, N'N-methylenebisacrylamide as a structure directing agent, adding a reducing agent, and passing through a one-step hydrothermal reaction to obtain the PtAg nanocrystals.

As a preference:

The solvent for the hydrothermal reaction is selected from water.

The reducing agent is selected from ascorbic acid.

The molar ratio of the N'N-methylenebisacrylamide to the sum of the two metal precursors is (1-100):1.

The Pt salt is selected from H ₂ PtCl ₆ or K ₂ PtCl ₄ ; the Ag salt is selected from AgNO ₃ or Ag(OAc).

The molar ratio of the Pt salt and the Ag salt is (0.01-100):1.

The temperature of the hydrothermal reaction is 100-200°C, and the time is 15-300 min.

The invention also provides the PtAg nanocrystalline material prepared by the above preparation method.

The present invention finally provides the application of the PtAg nanocrystalline material as an anode catalyst for methanol oxidation. The material is used as an anode catalyst for methanol oxidation and has excellent performance.

Ag is a 3d transition metal with abundant reserves and can form a PtAg alloy structure with Pt. The doping of Ag in the present invention can further reduce the amount of precious metal Pt, thereby effectively improving the atom utilization efficiency of precious metal Pt. At the same time, there is a synergistic effect between the doped Ag atoms and Pt atoms, which can effectively improve the electronic structure of Pt atoms, thereby greatly improving the electrocatalytic performance of the Pt-based nanocatalyst for methanol oxidation.

In addition to the influence of composition and structure, the activity of the electrocatalyst also largely depends on its morphology. The binary PtAg alloy nanoporous double hollow sphere structure prepared by the present invention exposes a large specific surface area and abundant The active sites, small surface energy, good stability and porous structure facilitate the mass transfer of reactants and products, so that the electrocatalytic activity and stability of MOR are greatly improved.

The present invention expands from the existing hydrothermal method to prepare the PtAg alloy to prepare the PtAg alloy by the hydrothermal method, thereby having a product with a special morphology, namely a porous double hollow spherical morphology, and the reaction solvent is a pure water phase, which is green and pollution-free.

Technical effect: Compared with the traditional preparation method, the present invention synthesizes PtAg alloy nanocrystals with unique porous double hollow spherical morphology and structure through a simple one-step hydrothermal method. The porous double hollow sphere PtAg nanocrystalline material of the present invention has mild preparation conditions, simple and efficient preparation, and has good electrocatalytic activity and stability for anodic methanol oxidation.

Specifically:

1) The preparation of porous double hollow sphere PtAg nanocrystals with unique morphology requires only one-step hydrothermal method, simple operation, mild conditions, and effectively reduces energy consumption.

2) The uniform size and regular shape of PtAg nanocrystals with porous double hollow sphere structure prepared by one-step hydrothermal method have a porous structure and the morphology is double hollow spheres, which is beneficial to the stability of the structure and exposing more reactive sites. point.

3) The results show that the prepared porous double hollow sphere PtAg nanocrystals exhibit high catalytic activity and stability for the anodic methanol oxidation (MOR) reaction. It is a very potential electrocatalyst for anodic methanol oxidation in the future new energy field. The application prospect is broad.

4) The preparation method of the present invention is simple, economical, green and pollution-free, and can realize large-scale production.

Description of the drawings

Figure 1 is a TEM chart of porous double hollow sphere PtAg nanocrystals prepared according to the method of the present invention;

Figure 2 is a SEM chart of porous double hollow sphere PtAg nanocrystals prepared according to the method of the present invention;

Figure 3 is an XRD pattern of porous double hollow sphere PtAg nanocrystals prepared according to the method of the present invention;

Figure 4 is the cyclic voltammetry curve of commercial Pt black, porous double hollow sphere PtAg nanocrystals in 0.5M sulfuric acid;

Figure 5 shows the methanol oxidation catalytic curves of commercial Pt black and porous double hollow sphere PtAg nanocrystals respectively;

Figure 6 shows the chronoamperometric curves of commercial Pt black and porous double hollow sphere PtAg nanocrystals in a 0.5MH ₂ SO ₄ +1.0MCH _{3 OH solution at a potential of 0.6V.}

Detailed ways

The technical solutions of the present invention will be further described in detail below through specific embodiments.

Example 1

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8 mL of water as the solvent, add 0.75 mL of 0.05 M H ₂ PtCl ₆ aqueous solution and 0.25 mL of 0.05 M AgNO ₃ aqueous solution and mix them thoroughly with ultrasound to make them uniform, and then add 10 mL 10 mg/ mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 2

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8mL of water as a solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 0.25mL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 1mL 10mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 3

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8mL of water as a solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 0.25mL of 0.05M AgNO ₃ aqueous solution to it, and then fully sonicate to make it uniform, then add 10mL 100mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 4

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8 mL of water as the solvent, add 0.75 _{mL of 0.05M K 2} PtCl ₄ aqueous solution and 0.25 mL of 0.05 M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 10 mL 10 mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 5

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: use 8mL of water as the solvent, add 7.5mL of 0.05M K ₂ PtCl ₄ aqueous solution and 0.25mL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 10mL 10mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 6

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8mL of water as the solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 2.5mL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 10mL 10mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 7

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8 mL of water as the solvent, add 0.75 mL of 0.05 M H ₂ PtCl ₆ aqueous solution and 25 μL of 0.05 M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, and then add 10 mL 10 mg/ mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 8

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Using 8mL of water as the solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 25 μL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, and then add 10mL 100mg/ mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 160°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 9

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Use 8mL of water as the solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 0.25mL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 10mL 10mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 100°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitate at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

Example 10

A method for preparing porous double hollow sphere PtAg nanocrystals includes the following steps:

1) Preparation of the reaction solution: Use 8mL of water as the solvent, add 0.75mL of 0.05M H ₂ PtCl ₆ aqueous solution and 0.25mL of 0.05M AgNO ₃ aqueous solution to it, mix and sonicate thoroughly to make it uniform, then add 10mL 10mg /mL of N'N-methylenebisacrylamide, ultrasonically mix well.

2) Preparation of porous double hollow sphere PtAg nanocrystals: Place the above reaction solution in an oven at 200°C for 4 hours, cool to room temperature, centrifuge the resulting black precipitated product at 10000rpm for 5min, and wash it with ethanol four times. The porous double hollow sphere PtAg nanocrystal is obtained.

The morphology of the porous double hollow sphere PtAg nanocrystals prepared above was characterized by TEM and SEM techniques. From the TEM image (Figure 1) and SEM image (Figure 2), it can be seen that the prepared catalyst has an obvious porous double hollow sphere structure.

It can be seen from the XRD pattern of Figure 3 that all the diffraction peak positions are between the peak positions shown on the standard cards of pure Pt (JCPDS: 04-0802) and pure Ag (JCPDS: 04-0783), and there is no difference between the positions of the peaks shown on the standard cards of pure Pt (JCPDS: 04-0802) and pure Ag (JCPDS: 04-0783). The coincident peaks of the standard card prove that the composition of the catalyst precursor is an alloy structure.

Figure 4 is the cyclic voltammetry curve of commercial Pt black and porous double hollow sphere PtAg nanocrystals in 0.5M sulfuric acid. It can be seen from the absorption and desorption peak area of hydrogen that the porous double hollow sphere PtAg nanocrystals are better than commercial Pt black. Has a larger electrochemical catalytic activity area.

Figure 5 is the methanol oxidation catalytic curve of commercial Pt black and porous double hollow sphere PtAg nanocrystals. It can be seen that the porous double hollow sphere PtAg nanocrystals have better catalytic activity for methanol oxidation than commercial Pt black.

Figure 6 is the chronocurrent curve of commercial Pt black, porous double hollow sphere PtAg nanocrystals in a 0.5M H ₂ SO ₄ +1.0M CH ₃ OH solution at a potential of 0.6V. It can be seen that the porous double hollow sphere PtAg nanocrystals are more commercial than commercial PtAg nanocrystals. Pt black has better catalytic stability.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (12)

1. A method for preparing PtAg nanocrystals, which is characterized in that it comprises using Pt salt and Ag salt as metal precursors, N'N-methylenebisacrylamide as a structure directing agent, adding a reducing agent, and passing through a one-step hydrothermal reaction. That is, the PtAg nanocrystal is obtained.
2. The method for preparing PtAg nanocrystals according to claim 1, wherein the solvent for the hydrothermal reaction is selected from water.
3. The method for preparing PtAg nanocrystals according to claim 1, wherein the reducing agent is selected from ascorbic acid.
4. The method for preparing PtAg nanocrystals according to claim 1, wherein the molar ratio of the N'N-methylenebisacrylamide to the sum of the two metal precursors is (1-100):1 .
5. The method for preparing PtAg nanocrystals according to claim 1, wherein the Pt salt is selected from H ₂ PtCl ₆ or K ₂ PtCl ₄ ; and the Ag salt is selected from AgNO ₃ or Ag(OAc).
6. The method for preparing nanocrystals PtAg according to claim 5, characterized in that the H ₂ PtCl ₆ in the form of an aqueous solution of H ₂ PtCl ₆ is provided, the concentration of H ₂ PtCl ₆ aqueous solution is 0.05M; the K ₂ PtCl _{4 is provided} in the form of an aqueous solution, and the concentration of _{the K 2} PtCl _{4 aqueous solution is 0.05M; the AgNO 3 is provided} in the form of an aqueous solution, and the concentration of _{the AgNO 3 aqueous solution is 0.05M.}
7. The method for preparing PtAg nanocrystals according to claim 1 or 5, wherein the molar ratio of the Pt salt to the Ag salt is (0.01-100):1.
8. The method for preparing PtAg nanocrystals according to claim 1, wherein the temperature of the hydrothermal reaction is 100-200°C, and the time is 15-300 min.
9. The method for preparing PtAg nanocrystals according to claim 1, wherein the method for preparing PtAg nanocrystals comprises the following steps:

   (1) Using water as the solvent, adding the Pt salt aqueous solution and the Ag salt aqueous solution, ultrasonically mixing uniformly, then adding N'N-methylenebisacrylamide, ultrasonically mixing uniformly, to obtain a reaction solution;

   (2) The reaction solution is subjected to a one-step hydrothermal reaction.
10. The method for preparing PtAg nanocrystals according to claim 1 or 9, characterized in that, after the hydrothermal reaction, it further comprises cooling to room temperature, centrifuging the resulting black precipitated product at 10000 rpm for 5 min, and washing with ethanol four times .
11. The PtAg nanocrystalline material prepared by the preparation method according to any one of claims 1 to 10 has an alloy structure.
12. Application of the PtAg nanocrystalline material of claim 11 as an anode catalyst for methanol oxidation.

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