Preparation method and application of supported high-dispersed alloy nanocluster catalyst

Abstract

The application discloses a preparation method and application of a supported high-dispersed alloy nanocluster catalyst. The catalyst material comprises a high specific surface area carbon carrier material with a special structure and an alloy nanocluster of two or more than two metals supported on the carrier material. The method is as follows: metal precursors are dissolved in a solvent containing water and an organic substance, the carbon carrier is dispersed in an organic solvent, mixing, heating, adding a reducing chemical reagent, washing, freeze-drying, and the catalyst is prepared. The alloy nanocluster prepared by the method has a small size, a uniform particle size distribution and is well dispersed on the surface of the carbon carrier. The prepared catalyst material is applied to a cathode catalyst of a lithium-oxygen battery and exhibits a good cycle life and a high capacity. The preparation method has the advantages of simple preparation operation and good method universality, and provides an important method and way for efficient preparation of alloy nanocluster catalysts in lithium-oxygen batteries and other energy systems.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, specifically relating to a method and application of a catalyst supported on highly dispersed alloy nanoclusters. Background Technology

[0002] Among the many energy storage systems currently under research, lithium-oxygen batteries (Li-O2) stand out due to their ultra-high theoretical energy density (3500 Wh / kg). -1 Li-O2 batteries are considered a promising next-generation secondary battery. However, the large-scale application of Li-O2 batteries still faces a series of challenges, including high overpotential, short cycle life, and susceptibility to side reactions. Among these challenges, the slow redox reaction kinetics on the air cathode and the insufficient durability of the cathode catalyst are key reasons for these problems. Therefore, designing and developing novel cathode catalysts with high activity and high stability to improve reaction kinetics and enhance catalyst stability is of great significance for promoting the practical application of Li-O2 batteries. Among various catalyst systems, carbon materials' low mass density and high conductivity are advantageous for achieving large battery capacity. Structurally, the pore structure of carbon-based electrodes can be easily adjusted using existing technologies. Meanwhile, metal nanoclusters, due to their small size and high atom utilization, easily achieve a balance between high activity and stability in electrocatalysis, and they also have broad application prospects in photocatalysis, information sensing, and biomedicine. Therefore, in the preparation of supported highly dispersed alloy nanocluster catalysts, finding a simple, controllable, efficient, and universal method to control the size of alloy nanoclusters and maintain high dispersion is of great importance. Yu Wang synthesized Au with a well-defined crystal structure using various ionic ligands. 24 Ag 20 Alloy nanoclusters (J.Am.Chem.Soc.2015,137,13,4324–4327). The nanoclusters synthesized by this method have specific numbers and ratios of metal atoms, but the operation process is relatively complex and cumbersome.

[0003] Chinese patent application CN114523120A discloses a method for preparing metal alloy nanoclusters. The method involves using citrate and ferrous salt as reducing precursors, reacting them with a mixed aqueous solution of a metal precursor and a support to prepare highly dispersed and relatively clean metal alloy nanoclusters. However, the nanoclusters prepared by this method have an average diameter of 3.52–4.76 nm, still exhibiting the problem of relatively large particle size.

[0004] Therefore, it is necessary to find a simple, efficient, and universal method to prepare uniform and highly dispersed alloy nanoclusters while effectively controlling their size. This will not only facilitate the application of supported alloy nanoclusters in electrocatalysis and electrochemical energy storage, but also greatly stimulate their application potential in areas such as information sensing, drug delivery, and medical treatment. Summary of the Invention

[0005] The purpose of this invention is to disclose a simple and universal method for preparing highly dispersed supported alloy nanoclusters with small particle sizes. This significantly reduces the amount of metal used while maintaining high performance and stability in Li-O2 batteries. The catalyst material prepared by this invention, when applied as a cathode catalyst in lithium-oxygen batteries, exhibits excellent cycle life and high capacity. The preparation of alloy nanoclusters significantly improves the capacity and cycle stability of the catalyst in lithium-oxygen batteries while substantially reducing the amount of precious metals used. The preparation method proposed in this invention has important advantages such as simple operation and good versatility, providing an important method and approach for the efficient preparation of alloy nanocluster catalysts in lithium-oxygen batteries and other energy systems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] A method for preparing supported highly dispersed alloy nanocluster catalysts utilizes porous carbon materials as supports to provide a favorable loading environment for a large number of highly dispersed alloy nanoclusters; the alloy components are noble metals or transition metals, preferably two of the following: acetylacetone salts of Pt, Pd, Rh, Ru, Mo, and Fe, or inorganic metal salts.

[0008] In this invention, the metal alloy component is uniformly distributed in the form of nano-atomic clusters on the surface of a carbon support with a special structure and high specific surface area. The preparation method includes steps such as dissolving / dispersing the metal precursor and carbon support in a solvent containing organic matter, low-temperature chemical reduction in the solvent, and freeze-drying. The resulting catalyst exhibits excellent cycle stability and high capacity in lithium-oxygen batteries.

[0009] The specific steps are as follows:

[0010] (1) The carbon support prepared by chemical vapor deposition (CVD) was treated with dilute acid, washed, freeze-dried, and ultrasonically dispersed in an organic solvent for later use.

[0011] (2) Dissolve the metal precursor in deionized water or organic solvent, then mix it with the dispersion from step (1) and sonicate it.

[0012] (3) Transfer the dispersion obtained in step (2) to an oil bath, adjust the reaction temperature, add NaBH4 solution dropwise while stirring, and then continue to maintain the reaction for a certain period of time to ensure complete reaction;

[0013] (4) Cool naturally to room temperature, filter and wash repeatedly, and then freeze dry in a freeze dryer for several hours to obtain a catalyst loaded with highly dispersed alloy nanoclusters.

[0014] Furthermore, the supported highly dispersed alloy nanocluster catalyst has a nanocluster size of less than 2 nanometers and a metal loading of 3% to 20%.

[0015] Further, in step (1), the CVD method uses acetonitrile or pyridine as the carbon source, the heat treatment temperature is 750-950℃, the heat treatment time is 1-2 hours, and the carrier gas is helium, argon or high-purity nitrogen.

[0016] Further, in step (1), the acid treatment temperature is room temperature, and dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid with a concentration of 1 to 6 mol / L is used, and the treatment time is 12 to 24 hours.

[0017] Further, in step (1), the organic solvent includes one or more of methanol, ethanol, isopropanol, ethylene glycol, N-methylpyrrolidone, and N,N-dimethylformamide; the ultrasonic time is 30 to 60 minutes.

[0018] Further, in step (2), the metal precursor includes two of the following: acetylacetone salts of Pt, Pd, Rh, Ru, Mo, and Fe, or inorganic metal salts, in a ratio of 1:1 to 4:1.

[0019] Furthermore, the organic solvent mentioned in step (2) includes one of ethanol, isopropanol, and ethylene glycol; the ultrasonic time is 30 to 60 minutes.

[0020] Further, the reaction temperature in step (3) is 80–150°C; the concentration of the NaBH4 solution is 5–10 mg / ml; and the reaction time is 0.5–2 hours.

[0021] Furthermore, in step (3), the catalyst was dried using freeze-drying technology for 12 to 24 hours.

[0022] In this invention, the catalyst supported on highly dispersed alloy nanoclusters, when used as a cathode catalyst in a Li-O2 battery, produces a cathode with excellent electrochemical performance.

[0023] The electrochemical performance evaluation method of the Li-O2 battery cathode catalyst used in this invention is as follows: a certain mass of supported highly dispersed alloy nanocluster catalyst is used as the cathode catalyst, a certain constant current is applied to the battery using an external circuit, and the charging and discharging is stopped at a specific voltage or the working time is limited. The specific capacity, charge and discharge overpotential or cycle number calculated in this way are used as the standard for evaluating the charge and discharge performance and stability of the battery.

[0024] This invention focuses on combining the two major factors of catalyst structure and performance, maintaining high electrochemical performance and stability of the catalyst while using a low metal loading.

[0025] Compared with the prior art, the advantages of the present invention are:

[0026] (1) The catalyst of the supported high-dispersion alloy nanoclusters described in this invention has a simple and efficient preparation method, is versatile, and has low requirements for reaction conditions and equipment.

[0027] (2) The preparation method described in this invention achieves uniform dispersion of alloy nanoclusters with small size, which greatly improves the utilization rate of metal.

[0028] (3) The catalyst of the supported high-dispersion alloy nanoclusters prepared in this invention exhibits excellent electrochemical performance when applied to the cathode of Li-O2 battery. Attached Figure Description

[0029] Figure 1 The XRD pattern of RuPd / CNCs prepared in Example 1 of this invention;

[0030] Figure 2 TEM image of RuPd / CNCs prepared in Example 1 of this invention;

[0031] Figure 3 HAADF-STEM image of RuPd / CNCs prepared in Example 1 of this invention;

[0032] Figure 4 The graph shows the first charge-discharge performance of RuPd / CNCs prepared in Example 1 of this invention when applied to the cathode of a Li-O2 battery.

[0033] Figure 5 The stability performance of RuPd / CNCs prepared in Example 1 of this invention when applied to the cathode of a Li-O2 battery is shown in the figure.

[0034] Figure 6 The XRD pattern of RuMo / CNCs prepared in Example 2 of this invention;

[0035] Figure 7The stability performance of RuMo / CNCs prepared in Example 2 of this invention when applied to the cathode of a Li-O2 battery is shown in the figure. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0037] Example 1

[0038] (1) Carbon carrier CNCs were prepared by using acetonitrile as carbon source, heat treatment temperature of 850℃, treatment time of 1h, and carrier gas of high-purity nitrogen. After treatment with 1mol / L dilute hydrochloric acid for 24h, freeze drying for 12h, and ultrasonic dispersion in ethanol / ethylene glycol mixed solvent for 30min for later use.

[0039] (2) Dissolve 11.3 mg of ruthenium chloride and 1.9 mg of palladium chloride as metal precursors in ethylene glycol solvent, mix with the solution in step (1), and sonicate for 30 min;

[0040] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 120℃, add 5mg / mL NaBH4 solution, and maintain the reaction for 1h;

[0041] (4) After the solution in step (3) is naturally cooled, washed, and freeze-dried for 12 hours, a catalyst RuPd / CNCs loaded with highly dispersed alloy nanoclusters is obtained.

[0042] The above catalyst was used to prepare an air cathode and its performance in a Li-O2 battery was tested: 2 mg of catalyst, 5% PVDF solution, and N-methylpyrrolidone solution were weighed to prepare a catalyst slurry, which was then drop-coated onto clean carbon paper with a diameter of 1.1 cm. After vacuum drying, the slurry was kept at a catalyst loading of 0.4 mg / cm². 2 (Calculated based on the entire catalyst). A button cell was assembled using a CR2032 battery case. The cathode was carbon paper coated with the catalyst, the current collector was nickel foam, the electrolyte was 1 M ITFSI / TEGDME solution, the separator was glass fiber, and the anode was lithium metal sheet. The battery was assembled in a glove box where the water and oxygen contents were both below 0.1 ppm. The assembled battery was then left to stand for 5 hours under high-purity O2 conditions for later use.

[0043] The test bottle containing the battery was connected to the Xinwei Battery Testing System for constant current charge-discharge testing. The set test current density and final charge-discharge specific capacity were calculated based on the mass of active material on the electrodes. The first charge-discharge performance test method was as follows: the charge-discharge cutoff voltage was limited to 2-4.3V, and the current density was 100mA / g. The cycle stability performance test method was as follows: the current density was 100mA / g, and one charge-discharge cycle was set to 5 or 10 hours. The test was stopped when the final voltage dropped below 2V or rose above 4.5V. The number of cycles obtained from this test was taken as the battery's cycle stability performance.

[0044] The XRD pattern of the RuPd / CNCs prepared in Example 1 is shown in [Figure 1]. Figure 1 No diffraction peaks related to metals Ru or Pd were found in the figure, indicating that the two are highly dispersed; their TEM results are shown in [image missing]. Figure 2 As can be seen, particles with an average size of less than 2 nm are uniformly dispersed on a carbon support with a hollow structure; its HAADF-STEM is shown in... Figure 3 The figure confirms that disordered metal atoms aggregate to form nanoclusters with a size less than 2 nm; the first-cycle charge-discharge performance exhibited when applied to the cathode of a Li-O2 battery is shown in [Figure number missing]. Figure 4 It can be seen that the catalyst applied to the cathode of a Li-O2 battery exhibits an initial charge-discharge specific capacity exceeding 30000 mAh / g and a low charge-discharge overpotential; the cycling performance exhibited by its application to the cathode of a Li-O2 battery is shown in [reference needed]. Figure 5 It can be observed that an excellent cycle life of over 300 cycles (3000 hours) has been achieved.

[0045] Example 2

[0046] (1) Carbon carrier CNCs were prepared by using acetonitrile as carbon source, heat treatment temperature of 850℃, treatment time of 1h, and high-purity argon as carrier gas. After treatment with 1mol / L dilute hydrochloric acid for 24h, freeze drying for 12h, and ultrasonic dispersion in isopropanol / ethylene glycol mixed solvent for 40min.

[0047] (2) Dissolve 11.5 mg of ruthenium chloride and 3 mg of molybdenum chloride as metal precursors in ethylene glycol solvent, mix with the solution from step (1), and sonicate for 40 min;

[0048] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 130℃, add 7.5 mg / mL NaBH4 solution, and maintain the reaction for 0.5 h;

[0049] (4) After the solution in step (3) is naturally cooled, washed, and freeze-dried for 16 hours, the catalyst RuMo / CNCs loaded with highly dispersed alloy nanoclusters is obtained.

[0050] The method for preparing the above catalyst into an air cathode and testing the performance of the Li-O2 battery is the same as in Example 1.

[0051] The XRD pattern of the RuMo / CNCs prepared in Example 2 is shown in [Figure 2]. Figure 6 No diffraction peaks related to metals Ru or Mo were found in the figure, indicating their high dispersion; the cycling performance exhibited when applied to the cathode of a Li-O2 battery is shown in [Figure number missing]. Figure 7 It can be observed that a good cycle life of over 900 hours has been achieved.

[0052] Example 3

[0053] (1) Carbon carriers CNCs were prepared by using pyridine as carbon source, heat treatment temperature of 800℃, treatment time of 1.5h, and high-purity helium as carrier gas. After treatment with 6mol / L dilute nitric acid for 12h, freeze drying for 12h, and ultrasonic dispersion in N-methylpyrrolidone / ethylene glycol mixed solvent for 50min.

[0054] (2) Dissolve 10.6 mg of ruthenium acetylacetonate and 8.1 mg of palladium acetylacetonate as metal precursors in ethylene glycol solvent, mix with the solution in step (1), and sonicate for 50 min;

[0055] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 150℃, add 5 mg / mL NaBH4 solution, and maintain the reaction for 1.5 h;

[0056] (4) After the solution in step (3) is naturally cooled, washed, and freeze-dried for 12 hours, a catalyst RuPd / CNCs loaded with highly dispersed alloy nanoclusters is obtained.

[0057] Example 4

[0058] (1) Carbon carriers CNCs were prepared by using acetonitrile as carbon source, heat treatment temperature of 900℃, treatment time of 2h, and carrier gas of high-purity nitrogen. After treatment with 2mol / L dilute hydrochloric acid for 12h, freeze drying for 12h, and ultrasonic dispersion in N,N-dimethylformamide / ethylene glycol mixed solvent for 40min.

[0059] (2) Dissolve 9.6 mg rhodium chloride and 14.3 mg platinum acetylacetonate as metal precursors in ethylene glycol solvent, mix with the solution in step (1), and sonicate for 40 min;

[0060] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 100℃, add 7.5 mg / mL NaBH4 solution, and maintain the reaction for 1 h;

[0061] (4) After the solution in step (3) is naturally cooled, it is washed and freeze-dried for 18 hours to obtain the catalyst RhPt / CNCs loaded with highly dispersed alloy nanoclusters.

[0062] Example 5

[0063] (1) Carbon carrier CNCs were prepared by using acetonitrile as carbon source, heat treatment temperature of 800℃, treatment time of 1h, and high-purity argon as carrier gas. After treatment with 1mol / L dilute sulfuric acid for 24h, freeze drying for 12h, and ultrasonic dispersion in ethylene glycol / isopropanol mixed solvent for 50min for later use.

[0064] (2) Dissolve 12.2 mg of ruthenium chloride and 1.9 mg of ferric acetylacetone as metal precursors in ethylene glycol solvent, mix with the solution in step (1), and sonicate for 50 min;

[0065] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 130℃, add 7.5 mg / mL NaBH4 solution, and maintain the reaction for 1 h;

[0066] (4) After the solution in step (3) is naturally cooled, washed, and freeze-dried for 24 hours, a catalyst RuFe / CNCs loaded with highly dispersed alloy nanoclusters is obtained.

[0067] Example 6

[0068] (1) Carbon carriers CNCs were prepared by using pyridine as carbon source, heat treatment temperature of 950℃, treatment time of 2h, and high-purity nitrogen as carrier gas. After treatment with 6mol / L dilute hydrochloric acid for 12h, freeze drying for 12h, and ultrasonic dispersion in ethanol / ethylene glycol mixed solvent for 60min.

[0069] (2) Dissolve 7.6 mg of platinum acetylacetonate and 7.4 mg of ruthenium acetylacetonate as metal precursors in ethylene glycol solvent, mix with the solution in step (1), and sonicate for 60 min;

[0070] (3) Transfer the solution obtained in step (2) to an oil bath, adjust the reaction temperature to 150℃, add 10mg / mL NaBH4 solution, and maintain the reaction for 0.5h;

[0071] (4) After the solution in step (3) is naturally cooled, washed, and freeze-dried for 20 hours, a catalyst PtRu / CNCs loaded with highly dispersed alloy nanoclusters is obtained.

[0072] The above embodiments of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a supported, highly dispersed alloy nanocluster catalyst for lithium-oxygen batteries, characterized in that: Includes the following steps: (1) A high specific surface area carbon support prepared by chemical vapor deposition (CVD) is treated with dilute acid, washed, freeze-dried, and ultrasonically dispersed in an organic solvent for later use; the CVD method uses acetonitrile or pyridine as the carbon source, the heat treatment temperature is 750~950℃, the heat treatment time is 1~2 hours, and the carrier gas is helium, argon or high-purity nitrogen; the carbon support has a hollow structure and a specific surface area of ​​1199 m² / g; the dilute acid treatment temperature is room temperature, using dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid with a concentration of 1~6 mol / L, and the treatment time is 12~24 hours; the organic solvent includes one or more of methanol, ethanol, isopropanol, ethylene glycol, N-methylpyrrolidone, and N,N-dimethylformamide; the ultrasonic time is 30~60 minutes. (2) Dissolve the metal precursor in deionized water or an organic solvent, then mix it with the dispersion from step (1) and sonicate it; the metal precursor includes any two metals selected from Pt, Pd, Rh, Ru, Mo, and Fe, and each metal precursor corresponds to an acetylacetone salt or an inorganic metal salt, with a molar ratio of the two metals being 1:1 to 4:1; the organic solvent includes one of ethanol, isopropanol, and ethylene glycol; the sonication time is 30 to 60 minutes; (3) Transfer the dispersion obtained in step (2) to an oil bath with a stirrer, adjust the reaction temperature to 80~150℃, and add NaBH4 solution dropwise while stirring. The concentration of NaBH4 solution is 5~10 mg / ml. After the addition is completed, continue to maintain the temperature and stir for 0.5~2 hours to make the reaction complete. (4) Cool naturally to room temperature, repeatedly filter and wash, and then freeze dry in a freeze dryer for 12 to 24 hours to obtain a catalyst loaded with highly dispersed alloy nanoclusters; in the catalyst, the metal alloy component is uniformly distributed on the surface of a high specific surface area carbon support in the form of nano atomic clusters; the size of the alloy nanoclusters is less than 2 nanometers, and the content of the alloy component is 3wt%-20 wt%.

2. A carbon-based catalyst with supported highly dispersed alloy nanoclusters is prepared by the preparation method described in claim 1.

3. The carbon-based catalyst of the supported highly dispersed alloy nanoclusters as described in claim 2 is applied to lithium-oxygen batteries.

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