Petal-shaped metal phosphide electrocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of secondary battery processing, and particularly relates to a preparation method of a petal-shaped metal phosphide electrocatalyst, which comprises the following steps: dissolving a metal salt in deionized water, and stirring at 60 DEG C for 1-2 hours until the metal salt is completely dissolved to obtain a solution A; dissolving diammonium hydrogen phosphate in deionized water, and stirring until the diammonium hydrogen phosphate is completely dissolved to obtain a solution B; slowly dripping the solution B into the solution A at 60 DEG C, and continuously stirring for 1-2 hours; dropwise adding a phosphoric acid solution into the mixed solution to adjust the pH value to 6-7; transferring the solution into a high-pressure kettle, and carrying out hydrothermal reaction at 200-220 DEG C for 20-24 hours; after the reaction is finished, after the reaction liquid is cooled to room temperature, centrifuging the reaction liquid, and washing the precipitate with deionized water; performing vacuum drying on a centrifugal separation product to obtain a hydrothermal product; and the dried product is calcined for 4-6 h at the temperature of 700-800 DEG C in the argon atmosphere, and the petal-shaped metal phosphide is obtained. The preparation method provided by the invention has the advantages of being simple in preparation, low in cost, easy to realize and control, good in repeatability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a petal-shaped metal phosphide electrocatalyst and a preparation method and application thereof. Background Art

[0002] In recent years, with the continuous growth of energy consumption, traditional energy sources such as oil, coal, and natural gas have brought serious environmental problems, making the transformation of the energy structure urgent. Although lithium-ion batteries have made significant progress and are widely used in the past few decades, they still cannot meet the growing needs of society. Therefore, one of the tasks we face now is to develop a new generation of energy storage devices to meet this challenge.

[0003] Metal-air batteries have attracted widespread attention due to their extremely high energy density, relative environmental friendliness, and enormous potential for development. However, existing metal-air secondary batteries still suffer from a series of bottlenecks, such as high discharge and charge overpotentials, low energy conversion efficiency, and poor cycling stability. The root cause of these problems lies in the inefficient formation and decomposition of discharge products at the gas-liquid-solid three-phase interface.

[0004] During battery discharge, the cathode surface is often covered with an insoluble peroxide film, which blocks reaction sites and limits battery performance. During charging, the peroxide's poor conductivity hinders charge transfer, increases the decomposition barrier, and leads to an increase in the charge overpotential. These issues limit the performance of metal-air secondary batteries.

[0005] Therefore, there is an urgent need to find an efficient catalyst that can optimize the reaction pathway through catalytic mechanisms to overcome the challenges faced by metal-air secondary batteries and improve battery performance. Traditional catalyst materials include precious metals, metal oxides, and carbon-based catalysts, but the high cost of precious metals and the lack of stability of carbon-based catalysts have limited their large-scale application.

[0006] Metal phosphides have catalytic diversity and can be used in many types of reactions, including redox, hydrogenation, oxidation, carbonylation and formylation, so they have broad application potential in various fields. In lithium-air secondary batteries, metal phosphides have multiple advantages as catalysts. First, they exhibit high catalytic activity and can significantly promote the reaction rate while reducing the reaction activation energy, thereby increasing the reaction yield. In addition, metal phosphides have high stability under high temperature and high pressure conditions, making them suitable for catalytic processes requiring extreme reaction conditions. They also exhibit resistance to poisoning and can continue to effectively catalyze reactions in the presence of harmful substances, enhancing their practicality. On this basis, a petal-shaped metal phosphide electrocatalyst, its preparation method and application are proposed. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a petal-shaped metal phosphide electrocatalyst, a preparation method and application thereof. The petal-shaped metal phosphide catalyst is prepared by a solvothermal method. The catalyst has high oxygen reduction activity, can reduce the binding energy of oxygen molecules, and promote the oxygen reduction reaction, which helps to improve the performance and efficiency of the battery; at the same time, the catalyst has long-term stability and can maintain its activity during multiple cycles of charge and discharge of the battery.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for preparing a petal-shaped metal phosphide electrocatalyst comprises the following steps: first preparing a metal solution; then slowly dripping a diammonium hydrogen phosphate solution into it; then dripping a phosphoric acid solution into it under stirring to adjust the pH value to 6-7; then subjecting the obtained mixed solution to a hydrothermal reaction to obtain a hydrothermal product; and finally subjecting the hydrothermal product to a high-temperature calcination treatment to obtain the petal-shaped metal phosphide.

[0009] The preparation method of the petal-shaped metal phosphide electrocatalyst specifically comprises the following steps: S1. Weigh 3-5 g of metal salt and dissolve it in 80-100 mL of deionized water. Stir at 60°C for 1-2 h until all the salt is dissolved to obtain solution A. S2. Weigh 6-10 g of diammonium hydrogen phosphate and dissolve it in 40-60 mL of deionized water. Stir until completely dissolved to obtain solution B. S3. Maintaining 60°C, slowly drip solution B into solution A. Continue stirring for 1-2 hours after solution B is completely dripped in. S4. Add phosphoric acid solution dropwise to the solution obtained in step S3 to adjust the pH to 6-7; S5. Transfer the solution obtained in step S4 to the inner lining of an autoclave and perform a hydrothermal reaction at 200-220° C. for 20-24 h; S6. After the reaction is completed, the reaction solution is cooled to room temperature, centrifuged, and the precipitate is washed with deionized water; S7, vacuum drying the centrifuged product to obtain a hydrothermal product; S8. calcining the dried product at 700-800° C. for 4-6 hours under an argon atmosphere to obtain a petal-shaped metal phosphide.

[0010] Preferably, the solutions in steps S1-S4 are all kept at a constant temperature of 60°C.

[0011] Preferably, the metal salt used in step S1 is nitrate, chloride or sulfate of iron, cobalt, nickel or manganese, preferably chloride.

[0012] Preferably, the mass of diammonium hydrogen phosphate used in step S2 is 2 to 4 times the mass of the metal salt weighed in step S1.

[0013] Preferably, in step S4, the pH is adjusted to 6-7 with phosphoric acid.

[0014] Preferably, the protective atmosphere for the high temperature treatment in step S8 is argon.

[0015] The petal-shaped metal phosphide electrocatalyst obtained by the preparation method is used as a metal-air secondary battery catalyst.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for preparing a petal-shaped metal phosphide electrocatalyst, which can be obtained by simple hydrothermal synthesis and subsequent heat treatment. It has the advantages of simple preparation steps, low cost, easy control, good repeatability, etc., and can provide an effective idea for subsequent scale-up production.

[0017] (2) The present invention obtains a petal-shaped metal phosphide electrocatalyst through a simple one-step hydrothermal synthesis. The catalyst has high oxygen reduction activity, can reduce the binding energy of oxygen molecules, and promote the oxygen reduction reaction, which helps to improve the performance and efficiency of the battery. At the same time, the catalyst has long-term stability and can maintain its activity during multiple cycles of charge and discharge of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0019] Figure 1 This is the SEM image of Example 2 of the present invention.

[0020] Figure 2 This is the SEM image of Example 4 of the present invention.

[0021] Figure 3 1 is a comparison diagram of the capacity-voltage curves of Example 1 and Example 2 of the present invention.

[0022] Figure 4 The capacity-voltage curves of Example 2 of the present invention at different cycle times are shown as follows: Figure 5 This is a long cycle performance diagram of Example 2 of the present invention.

[0023] Figure 6 This is a long cycle performance diagram of Example 1 of the present invention.

[0024] Figure 7 This is a long cycle performance diagram of Example 3 of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further illustrated below by way of examples, but is not intended to be limiting. Experimental procedures not specifically specified in the examples generally followed conventional conditions, those described in manuals, or those recommended by the manufacturers. The general equipment, materials, and reagents used were all commercially available unless otherwise specified. The raw materials required for the following examples were all commercially available.

[0026] Example 1: Weigh 3 g of cobalt acetate tetrahydrate and dissolve it in 80 mL of deionized water. Stir at 60° C. for 1 h until all salts are dissolved to obtain solution A; weigh 6 g of diammonium hydrogen phosphate and dissolve it in 40 mL of deionized water. Stir until it is completely dissolved to obtain solution B; maintain 60° C. and slowly drip solution B into solution A. After solution B is completely dripped in, continue stirring for 1 h; drip phosphoric acid solution into the obtained solution to adjust the pH to 6-7; transfer the obtained solution to the lining of an autoclave and carry out a hydrothermal reaction at 200° C. for 24 h; after the reaction is completed, the reaction solution is cooled to room temperature, centrifuged, and the precipitate is washed with deionized water; the centrifuged product is vacuum dried to obtain a hydrothermal product; the dried product is calcined at 700° C. for 4 h under an argon atmosphere to obtain a catalyst.

[0027] Example 2: Weigh 3 g of cobalt acetate tetrahydrate and dissolve it in 80 mL of deionized water. Stir at 60°C for 1 h until all salts are dissolved to obtain solution A; weigh 9 g of diammonium hydrogen phosphate and dissolve it in 40 mL of deionized water. Stir until completely dissolved to obtain solution B; maintain 60°C and slowly drip solution B into solution A. After solution B is completely dripped in, continue stirring for 1 h; drip phosphoric acid solution into the obtained solution to adjust the pH to 6-7; transfer the obtained solution to the liner of an autoclave and conduct a hydrothermal reaction at 200°C for 24 h; after the reaction is completed, the reaction solution is cooled to room temperature and centrifuged, and the precipitate is washed with deionized water; the centrifuged product is vacuum dried to obtain a hydrothermal product; the dried product is calcined at 700°C for 4 h under an argon atmosphere to obtain catalyst 2.

[0028] Example 3: Weigh 3 g of cobalt acetate tetrahydrate and dissolve it in 80 mL of deionized water. Stir at 60°C for 1 h until all salts are dissolved to obtain solution A. Weigh 9 g of diammonium hydrogen phosphate and dissolve it in 40 mL of deionized water. Stir until completely dissolved to obtain solution B. Maintain 60°C and slowly drip solution B into solution A. After solution B is completely dripped in, continue stirring for 1 h. Add phosphoric acid solution to the obtained solution and adjust the pH to 6-7. Transfer the obtained solution to the inner liner of an autoclave and conduct a hydrothermal reaction at 220°C for 24 h. After the reaction is completed, the reaction solution is cooled to room temperature and centrifuged. The precipitate is washed with deionized water. The centrifuged product is vacuum dried to obtain a hydrothermal product. The dried product is calcined at 700°C for 4 h under an argon atmosphere to obtain catalyst 3.

[0029] Example 4: Weigh 3 g of cobalt acetate tetrahydrate and dissolve it in 80 mL of deionized water. Stir at 60°C for 1 h until all salts are dissolved to obtain solution A. Weigh 9 g of diammonium hydrogen phosphate and dissolve it in 40 mL of deionized water. Stir until completely dissolved to obtain solution B. Maintaining 60°C, slowly drip solution B into solution A. After solution B is completely dripped in, continue stirring for 1 h. The resulting solution is transferred to the liner of an autoclave and subjected to a hydrothermal reaction at 200°C for 20 h. After the reaction is completed, the reaction solution is cooled to room temperature and centrifuged. The precipitate is washed with deionized water. The centrifuged product is vacuum dried to obtain a hydrothermal product. The dried product is calcined at 700°C for 4 h under an argon atmosphere to obtain catalyst 4.

[0030] Figure 1 and Figure 2 Scanning electron microscopy (SEM) images of Examples 2 and 4 are presented. A closer comparison of these SEM images reveals that without the addition of phosphoric acid for pH adjustment, the petal-shaped phosphide material was not effectively formed. Instead, large, irregular, and massive particles were observed. The petal-shaped catalyst structure possesses a higher surface area, enabling more complete contact with the electrolyte. Furthermore, this unique morphology provides more active sites, resulting in superior catalytic performance.

[0031] Figure 3 A comparison of the capacity-voltage curves of Examples 1 and 2 is presented. This comparison reveals that the ratio of diammonium hydrogen phosphate to metal salt significantly influences the catalytic performance of the final product. Catalyst 2 exhibits a lower catalytic overpotential, which positively impacts the battery's ability to achieve longer-lasting electrochemical cycling.

[0032] exist Figure 4The capacity-voltage curves of Catalyst 2 at different cycle times are shown in Figure 2. Data analysis reveals that after prolonged charge-discharge testing, the battery exhibits minimal polarization, while maintaining significant stability. This demonstrates the catalyst's excellent electrochemical stability and its ability to effectively catalyze battery reactions, thereby reducing polarization.

[0033] By comparison Figure 5 、 Figure 6 、 Figure 7 We can clearly see that the synthesis conditions have a significant impact on the catalytic performance of the final catalyst. High-temperature synthesis and inappropriate raw material ratios may reduce the catalytic activity of the final product. This discovery emphasizes the importance of precise control of synthesis conditions during catalyst synthesis and provides profound inspiration for future catalyst design and battery performance optimization.

[0034] The above content is a preferred embodiment in combination with the preferred embodiments, but it cannot be considered that the specific implementation of the present invention is limited to the embodiments. For those skilled in the art who understand the field to which the present invention belongs, a number of variations and substitutions can be made without departing from the research ideas of the present invention, and these deductions and substitutions are all included in the scope defined by the present invention.

Claims

1. A method for preparing a petal-shaped metal phosphide electrocatalyst, characterized in that: The following steps are involved: S1. Dissolve the metal salt in deionized water and stir at 60°C for 1-2 hours until completely dissolved to obtain solution A; S2. Dissolve diammonium hydrogen phosphate in deionized water and stir until completely dissolved to obtain solution B; S3. Slowly add solution B to solution A at 60°C and continue stirring for 1-2 hours; S4, adding phosphoric acid solution dropwise to the mixed solution to adjust the pH to 6-7; S5, transferring the solution to an autoclave for hydrothermal reaction; S6. After the reaction is completed, the reaction solution is cooled to room temperature, centrifuged, and the precipitate is washed with deionized water; S7. The centrifuged product was vacuum dried to obtain a hydrothermal product; S8. The dried product is calcined at high temperature under an argon atmosphere to obtain a petal-shaped metal phosphide.

2. The preparation method according to claim 1, characterized in that The solutions in steps S1-S4 were kept at a constant temperature of 60°C.

3. The preparation method according to claim 1, characterized in that The metal salt in step S1 is nitrate, chloride or sulfate of iron, cobalt, nickel or manganese.

4. The preparation method according to claim 1, characterized in that The mass of diammonium hydrogen phosphate in step S2 is 2-4 times the mass of the metal salt in step S1.

5. The preparation method according to claim 1, characterized in that The temperature of the hydrothermal synthesis in step S5 is 200-220°C.

6. The preparation method according to claim 1, characterized in that The time for the hydrothermal synthesis in step S5 is 20-24 hours.

7. The preparation method according to claim 1, characterized in that The temperature of the high temperature treatment in step S8 is 700-800°C.

8. The preparation method according to claim 1, characterized in that The time for the high temperature treatment in step S8 is 4-6 hours.

9. A petal-shaped metal phosphide electrocatalyst, characterized in that: The electrocatalyst is prepared by the preparation method according to any one of claims 1 to 8.

10. A metal-air battery, characterized in that: The petal-shaped metal phosphide electrocatalyst according to claim 9 is included.

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