A hollow carbon-supported multi-metal catalyst for zinc-air batteries and its preparation method

Abstract

The present invention provides a hollow carbon-supported multi-metal catalyst for zinc-air batteries and a preparation method thereof. A zinc-based zeolite imidazolate framework material (ZIF-8) is synthesized by coordination self-assembly, and two or more acetylacetonate metal compounds (M(acac)) are encapsulated in its internal pore space. X , X=2 or 3) to obtain the composite material M / ZIF‑8. M / ZIF‑8 is placed in Tris‑HCl buffer for dopamine hydrochloride self-polymerization to form a precursor (M / ZIF‑8@PDA), which is then pyrolyzed. During the pyrolysis process, PDA is first carbonized to form a stable shell structure, and the internal components of M / ZIF‑8@PDA decompose under the Kirkendall effect to form stable metal active sites, ultimately forming a hollow structure carbon-supported multi-metal catalyst. The catalyst prepared by the present invention can effectively improve the catalytic efficiency of ORR reaction and OER reaction, and can be applied to rechargeable zinc-air batteries.

Description

Technical Field

[0001] The invention relates to a hollow carbon-supported multi-metal catalyst for a zinc-air battery and a preparation method thereof, belonging to the scientific and technical field of zinc-air batteries. Background Art

[0002] Zinc-air batteries are a new type of energy device with great potential, featuring high efficiency, cleanliness, environmental protection, quietness and vibration-free operation, rapid start-up at low temperatures, adjustable power, and long life. However, some problems with zinc-air battery catalysts seriously hinder the large-scale promotion and application of zinc-air batteries. The disadvantages of the currently used zinc-air battery precious metal-based catalysts mainly include high cost, short life, poor durability, and low conversion efficiency. Among them, the use of precious metals (Pt / Ru) as catalysts results in high costs, and they are easily deactivated, aggregated, and corroded during use, resulting in a short life and poor durability. In addition, precious metal catalysts also have the problem of low catalytic efficiency, which means that a higher amount of catalyst is required to obtain sufficient electrical energy output. Currently, researchers are working hard to explore new catalyst materials and designs to solve these problems and improve the performance and reliability of zinc-air batteries.

[0003] A large amount of work has shown that materials with hollow structures can reduce the transfer resistance of substances inside the catalyst, accelerate the diffusion and transfer of reactants, and increase the reaction rate. At the same time, the specific surface area of ​​the catalyst can be increased, thereby improving the catalytic activity and efficiency. In addition, the type, quantity and metal site distribution of the metal elements in the catalyst are key factors determining the performance and stability of the catalyst. Transition metals can adjust the electronic structure of the catalyst, making it easier to react with oxygen, which can improve the reaction rate and efficiency. Based on the above characteristics, the development technology of multi-metal catalysts with hollow structures has received much attention. For example, Peng et al. (Small, 2021, 17(10): 2007239) developed an efficient, stable and low-cost composite carbon material as an ORR / OER catalyst in flexible metal-air batteries. Through a special heat treatment strategy (NH3 atmosphere), bimetallic nanoparticles were encapsulated in nitrogen-doped hollow carbon nanocubes to prepare a variety of bimetallic doped carbon catalysts (FeCo-NPs / NC, FeNi-NPs / NC and CoNi-NPs / NC catalysts). The results show that FeCo-NPs / NC catalysts exhibit excellent bifunctional electrocatalytic performance in ORR / OER, and also exhibit excellent discharge performance, excellent service life and high power discharge characteristics for zinc / aluminum-air batteries. Li et al. (Journal of the American Chemical Society, 2017, 139(48): 17281-17284) used a host-guest strategy to construct an Fe-Co bimetallic electrocatalyst embedded in nitrogen-doped porous carbon, which exhibited hollow structural characteristics in morphology and studied its ORR reaction activity in acidic electrolytes. Its onset potential (1.06V) and half-wave potential (0.863V) were comparable to those of commercial Pt / C catalysts. The FeCo bimetallic site can reduce the bond breaking barrier of the OO bond, thereby achieving high activity for ORR and high selectivity for the four-electron reduction path. The disadvantages of the above-mentioned literature methods are that they cannot realize the construction of multi-metal active sites, and at the same time, they do not achieve effective regulation of metal content and ratio, resulting in high preparation costs and complex processes.

[0004] To address these issues, we synthesized a hollow carbon-supported multimetallic catalyst derived from M / ZIF-8@PDA as a precursor. This catalyst exhibits advantages such as high specific surface area, reduced mass transfer resistance, enhanced catalyst stability, good controllability, and multifunctionality, which are beneficial for promoting the practical application of zinc-air batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a hollow carbon-supported multi-metal catalyst for zinc-air batteries and a preparation method thereof, wherein a zinc-based zeolite imidazolate framework material (ZIF-8) is synthesized by coordination self-assembly, and two or more acetylacetonate metal compounds (M(acac) X , X = 2 or 3), resulting in the composite material M / ZIF-8. M / ZIF-8 was placed in Tris-HCl buffer to undergo dopamine hydrochloride self-polymerization to form a precursor (M / ZIF-8@PDA), which was then pyrolyzed. During the pyrolysis process, PDA first carbonized to form a stable shell structure. The internal components of M / ZIF-8@PDA then decomposed under the Kirkendall effect, forming stable metal active sites, ultimately forming a hollow carbon-supported multimetallic catalyst.

[0006] The purpose of the present invention is achieved through the following solutions:

[0007] A method for preparing a hollow carbon-supported multi-metal catalyst comprises the following steps:

[0008] (1) Preparation of M / ZIF-8: An appropriate amount of 2-methylimidazole and two or more acetylacetonate metal compounds were mixed and dissolved in a methanol solvent to form a solution A. A certain amount of zinc nitrate hexahydrate was dissolved in a methanol solvent to form a solution B. The two solutions were mixed and stirred to prepare M / ZIF-8;

[0009] (2) Preparation of M / ZIF-8@PDA precursor: Tris(hydroxymethyl)aminomethane was dissolved in methanol by stirring, M / ZIF-8 was added to the above solution, a certain amount of dopamine hydrochloride was added to the mixed solution and stirred for a certain period of time, the obtained product was collected by centrifugation, washed with methanol, and dried to obtain M / ZIF-8@PDA precursor;

[0010] (3) Preparation of hollow carbon-supported multi-metal catalysts: A certain amount of M / ZIF-8@PDA precursor is placed in a high-temperature tube furnace filled with inert gas, and a certain heating time and heating temperature are set. The final product is a hollow carbon-supported multi-metal catalyst.

[0011] Furthermore, in step (1), the acetylacetonate metal compound is one or more of iron acetylacetonate (Fe(acac)3), cobalt acetylacetonate (Co(acac)2), zinc acetylacetonate (Zn(acac)2), platinum acetylacetonate (Pt(acac)2), nickel acetylacetonate (Ni(acac)2), copper acetylacetonate (Cu(acac)2), and manganese acetylacetonate (Mn(acac)3).

[0012] Furthermore, in step (1), the mass ratio of 2-methylimidazole to the acetylacetonate metal compound is 1 to 8: 1. More preferably, the mass ratio of 2-methylimidazole to the acetylacetonate metal compound is 1 to 5: 1.

[0013] Furthermore, in step (1), the mass ratio of 2-methylimidazole to zinc nitrate hexahydrate is 1 to 10:1.

[0014] Furthermore, in step (1), the stirring time is 12 to 24 hours, and the stirring temperature is 10 to 35°C.

[0015] Furthermore, in step (2), the mass ratio of tris(hydroxymethyl)aminomethane to dopamine hydrochloride is 1-5:1, and the mass ratio of M / ZIF-8 to dopamine hydrochloride is 1-10:1.

[0016] Furthermore, in step (2), the drying time is 12 to 24 hours, and the drying temperature is 60 to 80°C.

[0017] Furthermore, in step (3), the inert gas is one of Ar, He, and N2.

[0018] Furthermore, in step (3), the heating time is 1 to 5 hours, and the heating temperature is 900 to 1200°C.

[0019] In the preparation scheme of the present invention, the hollow structure is a regular dodecahedron with an internal cavity, and the shell thickness is determined by the thickness of the PDA layer formed by the polymerization of dopamine. The hollow carbon-supported multi-metal catalyst prepared in this embodiment of the present invention has a cavity size of 200-400 nm and a shell thickness of 10-40 nm.

[0020] In the preparation scheme of the present invention, the loading amount and type of metal elements contained in the catalyst are determined by the mass and type of the encapsulated M(acac)2. The metal M is one or more of Fe, Co, Zn, Ni, Cu, and Mn.

[0021] The present invention proposes a hollow carbon-supported multi-metal catalyst prepared by pyrolysis of an M / ZIF-8@PDA precursor. The catalyst has a hollow porous structure with two or more metal active sites distributed inside.

[0022] The present invention also provides the hollow carbon-supported multi-metal catalyst used in zinc-air battery materials.

[0023] In electrochemical testing, a three-electrode system was constructed using a reversible hydrogen electrode as the reference electrode, a Pt wire as the counter electrode, and a 3mm-diameter glassy carbon electrode coated with the catalyst as the working electrode. The ORR / OER catalytic activity of the catalyst was tested under alkaline conditions using linear voltammetry and chronoamperometry in an O2-saturated 0.1M KOH or 1M KOH electrolyte.

[0024] The technical solution of the present invention has the following advantages and beneficial effects:

[0025] (1) The catalyst prepared by the present invention is characterized by a porous hollow structure, which provides a higher reaction surface area and enhances the catalyst's activity. Furthermore, the synergistic effect of multiple metals can also enhance the catalyst's activity. Therefore, hollow carbon-supported multimetallic catalysts generally have higher catalytic activity. The hollow structure provides improved stability and corrosion resistance, preventing catalyst failure.

[0026] (2) The catalyst prepared by the present invention can effectively improve the catalytic efficiency of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and has excellent electrical output performance when applied to rechargeable zinc-air batteries, with a peak power density of up to 94 mW / cm 2 .

[0027] (3) In addition, carbon-supported multimetallic catalysts can also achieve higher stability by controlling the composition and structure of the metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the SEM photo of the Fe-Co / ZIF-8@PDA precursor prepared in Example 1.

[0029] Figure 2 TEM image of the Fe-Co / ZIF-8@PDA precursor prepared in Example 1.

[0030] Figure 3 This is the XRD photograph of the Fe-Co / ZIF-8@PDA precursor prepared in Example 1.

[0031] Figure 4 This is a SEM photograph of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1.

[0032] Figure 5 This is a TEM photo of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1.

[0033] Figure 6 This is the XRD picture of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1.

[0034] Figure 7This is the LSV curve (ORR) of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1.

[0035] Figure 8 This is the LSV curve (OER) of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1.

[0036] Figure 9 This is the electrical output performance curve of the zinc-air battery equipped with a hollow carbon-supported multi-metal catalyst in Example 1.

[0037] Figure 10 Comparison of IT test data of the hollow-structured carbon-supported multi-metal catalysts prepared in Example 1 and Example 2. DETAILED DESCRIPTION

[0038] Example 1

[0039] A method for preparing a hollow carbon-supported multi-metal catalyst for zinc-air batteries comprises the following steps:

[0040] (1) Preparation of Fe-Co / ZIF-8: 6.16 g of 2-methylimidazole, 2.5 g of ferric acetylacetonate, and 2.5 g of cobalt acetylacetonate were dissolved in 150 ml of methanol to form solution A. 5.95 g of zinc nitrate hexahydrate was dissolved in 150 ml of methanol to form solution B. The two solutions were mixed and stirred at room temperature for 24 h to prepare Fe-Co / ZIF-8.

[0041] (2) Preparation of Fe-Co / ZIF-8@PDA precursor: 0.121 g of tris(hydroxymethyl)aminomethane was dissolved in 100 ml of methanol by stirring. 0.5 g of Fe-Co / ZIF-8 was added to the above solution. 0.09 g of dopamine hydrochloride was added to the mixed solution and stirred for 12 h. The obtained product was collected by centrifugation, washed with methanol, and dried at 70 °C for 24 h.

[0042] (3) Preparation of hollow carbon-supported multi-metal catalysts: 0.5 g of Fe-Co / ZIF-8@PDA precursor was placed in a high-temperature tube furnace filled with N2, heated to 1100°C and kept warm for 2 h. The final product obtained was a hollow carbon-supported multi-metal catalyst.

[0043] Figure 1 and Figure 2 The SEM and TEM images of the Fe-Co / ZIF-8@PDA precursor prepared in Example 1 respectively show that the Fe-Co / ZIF-8@PDA precursor has an obvious heterogeneous structure, the polyhedral particle size is about 400-500 nm, and a PDA layer is distributed on the surface.

[0044] Figure 3This is the XRD pattern of the Fe-Co / ZIF-8@PDA precursor prepared in Example 1. It can be seen that Fe-Co / ZIF-8@PDA has a highly crystalline structure.

[0045] Figure 4 and Figure 5 The SEM and TEM images are respectively of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1. It can be seen that the hollow-structured carbon-supported multi-metal catalyst has a cavity size of 200 to 400 nm and a shell thickness of 10 to 40 nm.

[0046] Figure 6 This is the XRD pattern of the hollow-structured carbon-supported multi-metal catalyst prepared in Example 1. The spectrum shows that graphitic carbon has a broad peak at about 26°, the Fe signal is at 44.6°, and the Co signals are at 44.2°, 51.5°, and 75.8°.

[0047] Figure 7 This is the LSV curve (ORR) of the hollow carbon-supported multi-metal catalyst prepared in Example 1. The material exhibits good ORR catalytic performance, with an onset potential of 0.922 V and a half-wave potential of 0.743 V.

[0048] Figure 8 The LSV curve (OER) of the hollow carbon-supported multimetallic catalyst prepared in Example 1. The material showed good OER catalytic performance with a current density of 10 mA / cm 2 The potential is 1.558V.

[0049] The hollow carbon-supported multi-metal catalyst prepared in Example 1 is used as a zinc-air battery material. The specific steps are as follows:

[0050] The above catalyst was dispersed in ethanol and then drop-coated on a composite electrode as an air electrode, a zinc sheet was used as a metal electrode, and a 6M potassium hydroxide + 0.2M zinc acetate mixed solution was used as an electrolyte to assemble a rechargeable zinc-air battery.

[0051] Figure 9 This is the electrical output performance curve of the zinc-air battery equipped with a hollow carbon-supported multi-metal catalyst in Example 1. It can be seen that the battery peak power density is 94mW / cm 2 .

[0052] Example 2

[0053] A method for preparing a hollow carbon-supported multi-metal catalyst for zinc-air batteries comprises the following steps:

[0054] (1) Preparation of Pt-Co / ZIF-8: 6.16 g of 2-methylimidazole, 2.5 g of platinum acetylacetonate, and 2.5 g of cobalt acetylacetonate were dissolved in methanol to form solution A. 5.95 g of zinc nitrate hexahydrate was dissolved in 200 ml of methanol to form solution B. The two solutions were mixed and stirred at room temperature for 24 h to prepare Pt-Co / ZIF-8.

[0055] (2) Preparation of Pt-Co / ZIF-8@PDA precursor: 0.121 g of tris(hydroxymethyl)aminomethane was dissolved in 100 ml of methanol by stirring. 0.5 g of Pt-Co / ZIF-8 was added to the above solution. 0.15 g of dopamine hydrochloride was added to the mixed solution and stirred for 3 h. The obtained product was collected by centrifugation, washed with methanol, and dried at 70 °C for 24 h.

[0056] (3) Preparation of hollow carbon-supported multi-metal catalysts: 0.5 g of Pt-Co / ZIF-8@PDA precursor was placed in a high-temperature tube furnace filled with N2, heated to 1100°C and kept warm for 2 h. The final product obtained was a hollow carbon-supported multi-metal catalyst.

[0057] Figure 10 Comparison of IT test data for the hollow-structured carbon-supported multi-metallic catalysts prepared in Examples 1 and 2. It can be seen that after 8000 seconds of IT testing, the current decay is relatively low in both cases, with the catalyst prepared in Example 1 exhibiting a current decay of less than 8%, and the catalyst prepared in Example 2 exhibiting a current decay of less than 12%. This demonstrates that the catalysts prepared by the present method possess excellent long-term cycling stability.

[0058] Example 3

[0059] A method for preparing a hollow carbon-supported multi-metal catalyst for zinc-air batteries comprises the following steps:

[0060] (1) Preparation of Fe-Ni / ZIF-8: 6.16 g of 2-methylimidazole, 2.5 g of ferric acetylacetonate, and 2.5 g of nickel acetylacetonate were mixed and dissolved in methanol to form solution A. 5.95 g of zinc nitrate hexahydrate was dissolved in 200 ml of methanol to form solution B. The two solutions were mixed and stirred at room temperature for 24 h to prepare Fe-Ni / ZIF-8.

[0061] (2) Preparation of Fe-Ni / ZIF-8@PDA precursor: 0.121 g of tris(hydroxymethyl)aminomethane was dissolved in 100 ml of methanol by stirring. 0.5 g of Fe-Ni / ZIF-8 was added to the above solution. 0.15 g of dopamine hydrochloride was added to the mixed solution and stirred for 3 h. The obtained product was collected by centrifugation, washed with methanol, and dried at 70 °C for 24 h.

[0062] (3) Preparation of hollow carbon-supported multi-metal catalysts: 0.5 g of Fe-Ni / ZIF-8@PDA precursor was placed in a high-temperature tube furnace filled with N2, heated to 1000°C and kept warm for 2 h. The final product obtained was a hollow carbon-supported multi-metal catalyst.

[0063] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a hollow carbon-supported multi-metal catalyst, characterized in that: The following steps are involved: (1) Preparation of M / ZIF-8: 2-Methylimidazole and two acetylacetonate metal compounds were mixed and dissolved in methanol solvent to form solution A, and zinc nitrate hexahydrate was dissolved in methanol solvent to form solution B. The two solutions were mixed and stirred to prepare M / ZIF-8; (2) Preparation of M / ZIF-8@PDA precursor: Tris(hydroxymethyl)aminomethane was dissolved in methanol by stirring, M / ZIF-8 was added to the above solution, dopamine hydrochloride was added to the mixed solution and stirred, the obtained product was collected by centrifugation, washed with methanol, and dried to obtain M / ZIF-8@PDA precursor; (3) Preparation of hollow carbon-supported multi-metal catalysts: The M / ZIF-8@PDA precursor is placed in a high-temperature tube furnace filled with inert gas and heated. The final product is a hollow carbon-supported multi-metal catalyst with two metal active sites distributed inside. The combination of the two acetylacetonate metal compounds in step (1) is iron acetylacetonate and cobalt acetylacetonate or platinum acetylacetonate and cobalt acetylacetonate; In step (1), the mass ratio of 2-methylimidazole to the acetylacetonate metal compound is 1-8:1; the mass ratio of 2-methylimidazole to zinc nitrate hexahydrate is 1-10:

1.

2. The method for preparing a hollow carbon-supported multi-metal catalyst according to claim 1, characterized in that: In step (1), the stirring time is 12 to 24 hours, and the stirring temperature is 10 to 35°C.

3. The method for preparing a hollow carbon-supported multi-metal catalyst according to claim 1, characterized in that: In step (2), the mass ratio of tris(hydroxymethyl)aminomethane to dopamine hydrochloride is 1-5:1, and the mass ratio of M / ZIF-8 to dopamine hydrochloride is 1-10:

1.

4. The method for preparing a hollow carbon-supported multi-metal catalyst according to claim 1, wherein: In step (2), the drying time is 12 to 24 hours, and the drying temperature is 60 to 80°C.

5. The method for preparing a hollow carbon-supported multi-metal catalyst according to claim 1, characterized in that: In step (3), the inert gas is one of Ar, He, and N2.

6. The method for preparing a hollow carbon-supported multi-metal catalyst according to claim 1, characterized in that: In step (3), the heating time is 1 to 5 hours, and the heating temperature is 900 to 1200°C.

7. A hollow carbon-supported multi-metal catalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The catalyst has a hollow porous structure with two metal active sites distributed inside.

8. Use of the hollow carbon-supported multi-metal catalyst according to claim 7 in zinc-air batteries.

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