Ordered macroporous carbon supported bimetallic single-atom catalyst, preparation method and application

Abstract

The application provides an ordered macroporous carbon-supported bimetallic monatomic catalyst, a preparation method and application. The preparation method comprises the following steps: S1, synthesizing a polymer microsphere template, preparing a first transition metal-organic precursor solution, putting polystyrene ball templates into the first transition metal-organic precursor solution for normal-temperature immersion for 2 hours to obtain product A; S2, vacuum degassing the product A, performing suction filtration and placing the product A in an oven for drying overnight, placing the product A in a solution with an ammonia water and methanol volume ratio of 1:(0.8-1.2) for vacuum degassing, performing normal-temperature immersion for 20-30 hours, performing suction filtration to obtain the immersed template, placing the template in the oven for drying overnight to obtain a precursor-filled microsphere template; S3, placing the precursor-filled microsphere template in a tube furnace, introducing inert gas, and calcining to obtain product B; S4, mixing the product B with a second transition metal precursor solution, aging, centrifuging, drying, and then placing the product in a tube furnace, introducing inert gas, and calcining at 600-1000 DEG C for 2-4 hours.

Description

Technical Field

[0001] This invention relates to the field of fuel cells and metal-air batteries, specifically to an ordered macroporous carbon-supported bimetallic single-atom catalyst, its preparation method, and its application. Background Technology

[0002] Zinc-air batteries have a high energy density (1086 Wh / kg). -1 Zinc-air batteries, with their advantages of high intrinsic safety, low manufacturing cost, abundant zinc resources, and environmental friendliness, have shown great promise in consumer electronics, communication base stations, power batteries, smart grids, and industrial and commercial energy storage, attracting widespread attention. A typical zinc-air battery consists of a zinc anode, a separator, an air electrode, and an electrolyte. The zinc anode and air electrode generate current through a redox reaction. As the core component of the zinc-air battery, the air electrode plays a crucial role in catalyzing the oxygen reduction / oxygen evolution reaction (ORR / OER) during charging and discharging, thus determining the overall performance of the zinc-air battery, including its discharge capacity, energy density, power density, and service life.

[0003] Currently, air electrode catalysts still face significant challenges, such as low OER / ORR bifunctional catalytic activity, slow reaction kinetics, poor stability, and low mass transfer efficiency. These issues lead to bottlenecks such as low battery energy efficiency, low energy density / power density, and short service life, severely restricting the commercial application of zinc-air rechargeable batteries.

[0004] Currently developed air electrode catalysts mainly include three categories: carbon material systems, transition metal compounds, and transition metal / carbon-based composite systems. These single-atom catalysts maximize the utilization rate of active metals, greatly increase the content of metal-nitrogen coordination at active sites in the material, and promote the ORR / OER reaction towards a four-electron process through strong interaction between metal atoms and carbon supports. They have shown great application potential in the field of zinc-air batteries and have attracted widespread attention.

[0005] However, single-metal single-atom catalysts have relatively simple structures and lack interatomic synergy. Simply controlling the type of central metal atom, atomic coordination structure, and support structure is insufficient to break the linear relationship between the adsorption energies of reaction intermediates and achieve excellent ORR / OER catalytic activity. Bimetallic single-atom catalysts, by constructing bimetallic active sites, can achieve higher metal loading and more flexible active site structures. Furthermore, heteronuclear bimetals with asymmetric adsorption sites can directly regulate the d-band electronic structure and the spin state density of the active center, thereby achieving the optimal adsorption energy with intermediates and significantly improving the bifunctional oxygen electrocatalytic performance and stability.

[0006] Furthermore, the ORR / OER reaction in zinc-air batteries involves a gas-liquid-solid three-phase interface, and the pore structure of the air electrode has a significant impact on mass transfer efficiency and battery performance. An ordered, hierarchical macroporous structure possesses excellent mass transfer capabilities; its high porosity provides efficient transport channels for rapid gas-liquid transport; and its high specific surface area provides a gas-liquid-solid three-phase reaction region, increasing the number of effective catalytic active sites and promoting electron transfer.

[0007] Therefore, the urgent technical problem to be solved is to provide an ordered macroporous carbon-supported bimetallic single-atom catalyst to enhance the application value of zinc-air battery performance. Summary of the Invention

[0008] This invention is made to solve the above-mentioned problems, and aims to provide an ordered macroporous carbon-supported bimetallic single-atom catalyst, its preparation method, and its application.

[0009] This invention provides a method for preparing an ordered macroporous carbon-supported bimetallic single-atom catalyst, characterized by the following steps: S1, synthesizing a polymer microsphere template, preparing a first transition metal-organic precursor solution, immersing the polymer microsphere template in the first transition metal-organic precursor solution at room temperature for 2 hours to obtain product A; S2, degassing product A under vacuum, then filtering and drying it overnight in an oven at 40-60℃, and then degassing it in a solution of ammonia and methanol at a volume ratio of 1:(0.8-1.2). After degassing for 20-40 minutes, the microsphere template is impregnated at room temperature for 20-30 hours. The template is then filtered and dried overnight in an oven at 40-60℃ to obtain a precursor-filled microsphere template. In step S3, the precursor liquid-filled microsphere template is placed in a tube furnace, inert gas is introduced, and calcination is performed to obtain product B. In step S4, product B is mixed with the second transition metal precursor liquid, aged, centrifuged, dried, and then placed in a tube furnace. Inert gas is introduced, and the temperature is increased to 600-1000℃ at 3-7℃ / min for 2-4 hours.

[0010] The method for preparing the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention may also have the following characteristics: wherein the metal ions in the first transition metal-organic precursor and the second transition metal-organic precursor are selected from two or more of the transition metals cobalt, iron, zinc, copper, nickel, manganese, platinum, ruthenium, and iridium, and the metal ion concentration is 60-200 mmol / L; and the first transition metal-organic precursor solution includes at least one of 2-methylimidazole, dopamine hydrochloride, pyrrole, and dicyandiamide.

[0011] The method for preparing the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention may also have the following characteristics: wherein the polymer microsphere template is a polystyrene sphere template, and the preparation method of the polystyrene sphere template is as follows: take 4-6% wt of polystyrene microsphere emulsion into a centrifuge tube, centrifuge multiple times at a speed of 12000-18000 rpm, remove the supernatant and place it in an oven at 40-80℃ to dry overnight.

[0012] The preparation method of the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention may also have the following characteristics: wherein the calcination method in step S3 is to calcine at 3-7℃ / min to 350-450℃ for 4-6h, and then calcine at 3-7℃ / min to 900-940℃ for 2-4h.

[0013] The method for preparing the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention may also have the following features: the mixing and aging step in step S4 is specifically as follows: product B is dispersed in ethanol to obtain dispersion A; anhydrous ferric chloride, cyanuric acid, and dopamine hydrochloride are dispersed in ethanol and water to obtain dispersion B; dispersion B is poured into dispersion A, and ammonia water is added and the mixture is stirred and aged at room temperature for 10-14 hours; the mass ratio of anhydrous ferric chloride, cyanuric acid, and dopamine hydrochloride is 1:(9-11):(1-1.5); and the mass ratio of dispersion A to dispersion B is 1:(5-5.5).

[0014] The present invention also provides an ordered macroporous carbon-supported bimetallic single-atom catalyst, characterized by being prepared by the above-described method for preparing ordered macroporous carbon-supported bimetallic single-atom catalysts.

[0015] The ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention may also have the following characteristics: wherein the three-dimensional porous nitrogen-doped carbon anchored to the first transition metal and the carbon-supported second transition metal single-atom layer coated on the surface of the three-dimensional porous nitrogen-doped carbon substrate have heterogeneous transition metal single atoms, and the inner and outer parts form a core-shell structure, and the dual active metal atomic sites synergistically catalyze the oxygen reduction reaction.

[0016] This invention also provides an application of an ordered macroporous carbon-supported bimetallic single-atom catalyst in a zinc-air battery.

[0017] In the application of the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention in a zinc-air battery, it may also have the following characteristics: wherein the zinc-air battery includes a positive electrode, a negative electrode, a separator, an air inlet and an electrolyte, the catalyst of the positive electrode is an ordered macroporous carbon-supported bimetallic single-atom catalyst, the positive electrode and the negative electrode are placed opposite each other, and the positive electrode and the negative electrode are separated by a separator, wherein the side of the positive electrode with the ordered macroporous carbon-supported bimetallic single-atom catalyst faces away from the air inlet.

[0018] In the application of the ordered macroporous carbon-supported bimetallic single-atom catalyst provided by the present invention in zinc-air batteries, it can also have the following characteristics: wherein the negative electrode material is zinc foil, the separator is glass fiber paper, and the electrolyte is an aqueous solution of potassium hydroxide and zinc acetate.

[0019] The role and effect of invention

[0020] According to the ordered macroporous carbon-supported bimetallic single-atom catalyst, preparation method and application of the present invention, the composite structure of special bimetallic single atoms greatly enhances the intrinsic oxygen reduction reaction activity of traditional zeolite imidazole framework (ZIF) derived single-atom catalysts. The high specific surface area of ​​the ordered hierarchical macroporous structure provides more accessible active sites, and the rich pore structure is also more conducive to the formation of effective three-phase interfaces and rapid mass transfer in electrochemical processes. These characteristics greatly improve the oxygen reduction reaction efficiency.

[0021] In this invention, the heterogeneous bimetallic single-atom layers within a core-shell structure are coupled and synergistically catalyze, significantly enhancing the intrinsic catalytic activity of the carbon-based single-atom catalyst. The ordered porous structure achieves a high specific surface area, exposing a greater number of accessible atomic active sites. The porous microstructure improves the hydrophobic properties of the material surface, facilitating the formation of an effective gas-liquid-solid three-phase reaction interface and increasing the device's output power density. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation of the ordered macroporous carbon-supported bimetallic single-atom catalyst in the embodiments of the present invention;

[0023] Figure 2 This is a SEM image of IrFe-SACs in Embodiment 1 of the present invention;

[0024] Figure 3 This is a SEM image of CuFe-SACs in Example 2 of the present invention;

[0025] Figure 4 This is a SEM image of CoFe-SACs in Comparative Example 1 of the present invention;

[0026] Figure 5These are the ORR performance curves of IrFe-SACs and other bimetallic atom catalysts in Examples 1-3 and Comparative Example 1 of the present invention;

[0027] Figure 6 This is the discharge specific capacity curve of liquid ZABs based on IrFe-SACs and Pt / C-RuO2 in an embodiment of the present invention;

[0028] Figure 7 These are the discharge polarization curves and power density curves of liquid ZABs based on IrFe-SACs and Pt / C-RuO2 in embodiments of the present invention;

[0029] Figure 8 In an embodiment of the present invention, liquid ZABs based on IrFe-SACs and Pt / C-RuO2 air cathodes were used at 5 mA / cm². -2 The constant current charge-discharge cycle curve is shown below. Detailed Implementation

[0030] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the ordered macroporous carbon-supported bimetallic single-atom catalyst, preparation method and application of this invention.

[0031] Example 1

[0032] A method for preparing an ordered macroporous carbon-supported iridium-iron bimetallic single-atom catalyst specifically includes the following steps:

[0033] S1. Take 100 mL of 5% wt polystyrene microsphere emulsion (microsphere diameter: ~500 nm), centrifuge multiple times at 15000 rpm in a centrifuge tube, remove the supernatant, and dry overnight in a 60℃ oven to obtain a polystyrene sphere template. Dissolve and disperse 5.07 g of 2-methylimidazole, 5.82 g of zinc nitrate hexahydrate, and 0.505 g of iridium acetylacetonate in 15 mL of deionized water to form a precursor solution. Immerse the self-assembled polystyrene template in the above precursor solution at room temperature for 2 h to obtain product A.

[0034] S2, product A was degassed under vacuum for 30 min, then filtered to obtain a polystyrene template, which was then dried in an oven at 50°C overnight. The obtained polystyrene template was placed in a solution of ammonia and methanol in a 1:1 volume ratio and degassed under vacuum for 30 min, then impregnated at room temperature for 24 hours. The impregnated template was then filtered and dried in an oven at 50°C overnight to obtain a precursor-filled microsphere template.

[0035] S3, the precursor-filled microsphere template was placed in an argon atmosphere in a tube furnace and calcined at 400℃ for 5 hours at a rate of 5℃ / min, and then calcined at 920℃ for 3 hours at a rate of 5℃ / min to obtain product B.

[0036] S4. Disperse 100 mg of product B in 20 mL of ethanol to obtain dispersion A. Disperse 50 mg of anhydrous ferric chloride, 500 mg of cyanuric acid, and 55 mg of dopamine hydrochloride in 20 mL of ethanol and 10 mL of water to obtain dispersion B. Pour dispersion B into dispersion A, add 750 μL of ammonia water, stir and age at room temperature for 12 h, centrifuge, dry, and then calcine in a tube furnace under an argon atmosphere at a rate of 5 °C / min to 800 °C for 2 hours to obtain the final product.

[0037] Example 2

[0038] Based on Example 1, this example replaces “0.505g iridium acetylacetone” in step S1 with “0.25g copper nitrate trihydrate”.

[0039] Example 3

[0040] Based on Example 1, this example replaces “0.505g iridium acetylacetone” in step S1 with “0.30g nickel nitrate hexahydrate”.

[0041] Comparative Example 1

[0042] Based on Example 1, this example replaces “0.505g iridium acetylacetone” in step S1 with “0.30g cobalt nitrate hexahydrate”.

[0043] Figure 1 This is a flowchart illustrating the preparation process of the ordered macroporous carbon-supported iridium-iron bimetallic single-atom catalyst in the embodiments of the present invention.

[0044] like Figure 1 As shown, a polystyrene microsphere template impregnated with an Ir-MOF precursor was subjected to segmental pyrolysis under an argon atmosphere to remove the microsphere template and carbonize it to obtain a nitrogen-doped carbon support with honeycomb-like channels.

[0045] Figure 2 This is a SEM image of IrFe-SACs in Embodiment 1 of the present invention. Figure 3 This is a SEM image of CuFe-SACs in Example 2 of the present invention. Figure 4 This is a SEM image of CoFe-SACs in Comparative Example 1 of the present invention. Figure 5 These are the ORR performance curves of IrFe-SACs and other bimetallic atom catalysts in Example 3 of the present invention.

[0046] like Figure 2-5As shown, the corresponding carbon support can be prepared from MOFs such as Co or Cu. Then, a layer of Fe composite is anchored on the surface of the porous nitrogen-doped carbon support by polydopamine, and a core-shell structure catalyst is obtained by high-temperature pyrolysis, with a porous carbon inner layer anchored with Ir, Co, or Cu single atoms and an outer layer of Fe single atoms.

[0047] In the two-step pyrolysis, MOFs spontaneously aromatize at high temperatures to form Ir-N x / Fe-N x Highly graphitized nitrogen-doped carbon with single-atom sites. Zinc species evaporate at high temperatures, forming numerous micropores in the carbon matrix, which improves the dispersibility of iridium-iron species and increases specific surface area.

[0048] like Figure 5 As shown, the two transition metal single atoms are coupled and synergistically catalyze each other, and IrFe-SACs exhibit excellent intrinsic catalytic activity for the oxygen reduction reaction: high half-wave potential of the oxygen reduction reaction: E 1 / 2 =0.872V. IrFe-SACs catalyst, Zn foil, and 6.0M KOH containing 0.2M zinc acetate were further used as the positive, negative, and electrolyte air, respectively. Control ZABs were also prepared using Pt / C and RuO2 in a 1:1 mass ratio; the ordered macroporous carbon structure and large reaction surface area provided abundant accessible active sites.

[0049] The optimized gas-liquid-solid three-phase interface with hydrophobic porous carbon structure enables high discharge power density and capacity of zinc-air batteries, demonstrating excellent battery performance.

[0050] Figure 6 The discharge specific capacity curves of liquid ZABs based on IrFe-SACs and Pt / C-RuO2 are shown in the embodiments of the present invention.

[0051] like Figure 6 As shown, at 5mA cm -2 Under these conditions, the specific capacity of the IrFe-SACs air cathode ZABs is 815.1 mAh g. -1 This is superior to Pt / C-RuO2 air cathode ZABs (733.4 mAh g). -1 ).

[0052] Figure 7 These are the discharge polarization curves and power density curves of liquid ZABs based on IrFe-SACs and Pt / C-RuO2 in embodiments of the present invention.

[0053] like Figure 7 As shown, the peak power density of ZABs based on IrFe-SACs is 219 mW / cm². -2It is far superior to ZABs based on Pt / C-RuO2 (114 mW cm⁻¹). -2 ).

[0054] Figure 8 In an embodiment of the present invention, liquid ZABs based on IrFe-SACs and Pt / C-RuO2 air cathodes were used at 5 mA / cm². -2 The constant current charge-discharge cycle curve is shown below.

[0055] like Figure 8 As shown, at 5mA cm -2 The IrFe-SAC-based ZAB maintained constant charge (2.00V) and discharge (1.12V) voltages for more than 1650 cycles (greater than 550 hours), demonstrating its excellent cycle durability.

[0056] The role and effect of the embodiments

[0057] According to the ordered macroporous carbon-supported bimetallic single-atom catalyst, preparation method and application of the present invention, the composite structure of special bimetallic single atoms greatly enhances the intrinsic oxygen reduction reaction activity of traditional zeolite imidazole framework (ZIF) derived single-atom catalysts. The high specific surface area of ​​the ordered hierarchical macroporous structure provides more accessible active sites, and the rich pore structure is also more conducive to the formation of effective three-phase interfaces and rapid mass transfer in electrochemical processes. These characteristics greatly improve the oxygen reduction reaction efficiency.

[0058] In this invention, the heterogeneous bimetallic single-atom layers within a core-shell structure are coupled and synergistically catalyze, significantly enhancing the intrinsic catalytic activity of the carbon-based single-atom catalyst. The ordered porous structure achieves a high specific surface area, exposing a greater number of accessible atomic active sites. The porous microstructure improves the hydrophobic properties of the material surface, facilitating the formation of an effective gas-liquid-solid three-phase reaction interface and increasing the device's output power density.

[0059] The preparation method of this invention has good process versatility and can easily realize the preparation of carbon-based single-atom materials on the surface of air cathodes.

[0060] The ordered hierarchical macroporous carbon-supported bimetallic single-atom catalyst of the present invention has broad application potential in fields such as zinc-air batteries and fuel cells, and has good application prospects.

[0061] The present invention uses 2-methylimidazole, zinc nitrate hexahydrate and iridium acetylacetone to form a precursor solution, which makes the catalyst have excellent intrinsic catalytic activity for oxygen reduction reaction.

[0062] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an ordered macroporous carbon-supported bimetallic single-atom catalyst, characterized in that, Specifically, the steps include the following: S1, synthesize polymer microsphere template, prepare a first transition metal-organic precursor solution, immerse the polymer microsphere template in the first transition metal-organic precursor solution at room temperature for 2 hours to obtain product A, wherein the polymer microsphere template is a polystyrene sphere template; S2, the product A is degassed under vacuum, then filtered and dried in an oven at 40-60℃ overnight, and then placed in a solution of ammonia and methanol at a volume ratio of 1:(0.8-1.2) under vacuum for 20-40 min, and then impregnated at room temperature for 20-30 h. The impregnated template is obtained by filtration and dried in an oven at 40-60℃ overnight to obtain a precursor-filled microsphere template. S3, the microsphere template filled with the precursor fluid is placed in a tube furnace, an inert gas is introduced, and it is calcined to obtain product B; S4, the product B is mixed with the second transition metal precursor liquid, aged, centrifuged, dried, and then placed in a tube furnace. Inert gas is introduced, and the temperature is increased to 600-1000℃ at 3-7℃ / min for calcination for 2-4 hours. Wherein, the metal ions in the first and second transition metal-organic precursors are selected from two or more of the transition metals cobalt, iron, zinc, copper, nickel, manganese, platinum, ruthenium, and iridium, and the concentration of the metal ions is 60-200 mmol / L. The first transition metal-organic precursor solution includes at least one of 2-methylimidazole, dopamine hydrochloride, pyrrole, and dicyandiamide. The calcination method in step S3 is as follows: calcination at 350-450℃ for 4-6 hours by increasing the temperature at 3-7℃ / min, and then calcination at 900-940℃ for 2-4 hours by increasing the temperature at 3-7℃ / min. The specific steps of mixing and aging in step S4 are as follows: dispersing product B in ethanol to obtain dispersion A, dispersing anhydrous ferric chloride, cyanuric acid, and dopamine hydrochloride in ethanol and water to obtain dispersion B, pouring dispersion B into dispersion A, adding ammonia, and then stirring and aging at room temperature for 10-14 hours.

2. The method for preparing the ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 1, characterized in that: in, The preparation method of the polystyrene ball template is as follows: take 4-6%wt of polystyrene microsphere emulsion into a centrifuge tube, centrifuge multiple times at a speed of 12000-18000 rpm, remove the supernatant and dry it overnight in an oven at 40-80℃.

3. The method for preparing the ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 1, characterized in that: in, The mass ratio of anhydrous ferric chloride, cyanuric acid and dopamine hydrochloride is 1:(9-11):(1-1.5), and the mass ratio of dispersion A and dispersion B is 1:(5-5.5).

4. The ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 1, characterized in that: The catalyst was prepared by the method described in any one of claims 1-3 for preparing ordered macroporous carbon-supported bimetallic single-atom catalysts.

5. The ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 4, characterized in that: in, It includes a three-dimensional porous nitrogen-doped carbon anchored to a first transition metal and a carbon-supported second transition metal single-atom layer coated on the surface of the three-dimensional porous nitrogen-doped carbon substrate. The three-dimensional porous nitrogen-doped carbon and the carbon-supported second transition metal single-atom layer have heterogeneous transition metal single atoms, and the inner and outer parts form a core-shell structure. The dual active metal atomic sites synergistically catalyze the oxygen reduction reaction.

6. The application of an ordered macroporous carbon-supported bimetallic single-atom catalyst as described in any one of claims 4-5 in a zinc-air battery.

7. The application of the ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 6 in a zinc-air battery, characterized in that: The zinc-air battery includes a positive electrode, a negative electrode, a separator, an air inlet, and an electrolyte. The catalyst of the positive electrode is the ordered macroporous carbon-supported bimetallic single-atom catalyst. The positive and negative electrodes are arranged opposite to each other and separated by the separator. The side of the positive electrode with the ordered macroporous carbon-supported bimetallic single-atom catalyst faces away from the air inlet.

8. The application of the ordered macroporous carbon-supported bimetallic single-atom catalyst according to claim 7 in a zinc-air battery, characterized in that: The negative electrode is made of zinc foil, the separator is made of glass fiber paper, and the electrolyte is an aqueous solution of potassium hydroxide and zinc acetate.

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