Polyoxometalate metal cluster, preparation method and application thereof
The preparation of polyacid metal clusters via hydrothermal reaction solves the synthesis and stability problems of nickel-based metal hydroxides in existing technologies, achieving efficient and low-cost catalyst preparation suitable for catalytic applications in fuel cells, water electrolysis, and metal-air batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN TEXTILE UNIV
- Filing Date
- 2025-06-06
- Publication Date
- 2026-06-12
AI Technical Summary
Existing technologies struggle to achieve precise synthesis, structural stability, and large-scale preparation, hindering the practical application of non-precious metal catalysts. In particular, nickel-based metal hydroxides suffer from insufficient exposure of active sites and poor structural stability in their two-dimensional layered structures, particularly in fuel cells, water electrolysis, and metal-air batteries.
Polyacid metal clusters were prepared by a hydrothermal reaction method. Multidentate chelating ligands such as polyacrylic acid and its derivatives were reacted with metal salts at 100-160℃ to form stable metal clusters through precise molecular recognition and self-assembly mechanisms, thus constructing a regular layered structure.
It achieves efficient and low-cost catalyst synthesis, significantly improves catalytic activity and stability, reduces overpotential, and is suitable for large-scale industrial production. It is applicable to CO2 reduction, water electrolysis and urea oxidation reactions.
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Figure CN120945409B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, and in particular to a polyacid metal cluster, its preparation method, and its application. Background Technology
[0002] Nickel-based metal hydroxides are considered ideal candidates to replace precious metals due to their low cost and theoretical activity potential, and have attracted much attention in the field of energy technology (such as fuel cells, water electrolysis, and metal-air batteries). However, the intrinsic defects of their two-dimensional layered structure lead to two major bottleneck problems: insufficient exposure of active sites and poor structural stability.
[0003] Metal cluster catalysts, due to their atomic-level dispersion characteristics, can significantly improve the utilization rate of metal atoms to over 90%, providing a new direction for solving the aforementioned problems. However, existing synthesis technologies have the following key drawbacks: High-temperature pyrolysis (above 600℃) can prepare metal clusters, but the high temperature increases the particle size from 2 nm to 5 nm, while also inducing carbonization to cover active sites, and the energy consumption cost is as high as 30 kWh / g; Microemulsion methods can achieve 3 nm-level particle size control, but template agent residue (5-8 wt%) causes catalyst poisoning; Electrochemical deposition methods can obtain 2 nm-level clusters, but the loss rate of active material exceeds 30% / 100 cycles due to substrate dependence and interfacial stress problems; while photochemical reduction, atomic layer deposition and other methods are limited by low quantum yield (<0.1%) and slow growth rate (0.1 nm / cycle), and their batch production capacity (<0.5 g / h) and cost (>50 USD / g) are far from meeting the needs of industrialization. The aforementioned problems collectively highlight the technical barriers to synergistic optimization of precise synthesis, structural stability, and large-scale preparation, which severely restricts the practical application of metal cluster catalysts.
[0004] In summary, existing technologies struggle to balance precise synthesis, structural stability, and large-scale preparation, severely hindering the practical application of non-precious metal catalysts. Summary of the Invention
[0005] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a polyacid metal cluster, its preparation method, and its application.
[0006] The first objective of this invention is to provide a method for preparing polyacid metal clusters, which involves subjecting a metal salt, water, and a multidentate chelate ligand to a hydrothermal reaction, washing and centrifuging the resulting solid, and drying it to obtain polyacid metal clusters.
[0007] Furthermore, the multidentate chelating ligand is a polymer containing a carboxylic acid group.
[0008] Furthermore, the multidentate chelating ligand comprises polyacrylic acid or a derivative thereof.
[0009] Furthermore, the molecular weight of the multidentate chelating ligand ranges from 1,000 to 50,000, and each repeating unit contains at least one carboxylic acid group.
[0010] Furthermore, the hydrothermal reaction temperature is 100-160℃, and the reaction time is 6-18 h.
[0011] Furthermore, the washing process involves washing several times with deionized water and anhydrous ethanol until the solution is clear.
[0012] Furthermore, the metal salt is one or more of nickel, cobalt, iron, manganese, and cerium; the metal salt is one or more of nitrate, chloride, sulfate, or sulfate.
[0013] Furthermore, the mass-to-volume ratio of the metal salt, water, and multidentate chelate ligand is 0.005~3.0 g: 5~100 mL: 5~1500 uL.
[0014] A second objective of this invention is to provide a polyacid metal cluster obtained by the above-described preparation method.
[0015] A third objective of this invention is to provide an application of the polyacid metal clusters described above, characterized in that it is a catalyst for CO2 reduction, water electrolysis, and urea oxidation.
[0016] This invention relates to a polyacid-metal cluster material prepared via a hydrothermal reaction method. The catalyst uses nickel hydroxyoxide (NiOOH) as its framework, utilizing the strong coordination ability of carboxylic acid groups to anchor metal ions and form stable bonds. Simultaneously, the synergistic effect of polyacid groups guides the assembly of metal clusters. During assembly, the components interact dynamically and synergistically, ultimately constructing a well-ordered layered structure through precise molecular recognition and self-assembly mechanisms. Significantly different from metal catalysts prepared by conventional methods (such as nickel-based catalysts), this material exhibits clear lattice fringes and significantly superior long-range order compared to traditional nickel-based catalysts and commercially available ruthenium oxide. It also exhibits a lower overpotential and demonstrates significant differences in promoting water electrolysis and urea oxidation. In the oxygen evolution reaction (OER), the overpotential was significantly reduced by 229 mV compared to conventional nickel-based catalysts at a current density of 50 mA / cm². In the urea oxidation reaction (UOR), the overpotential required to reach a current density of 10 mA / cm² was only 96 mV (compared to the theoretical voltage of conventional water electrolysis). Furthermore, after continuous operation at a constant current density of 100 mA / cm² for 10 hours, the overpotential remained unchanged, demonstrating excellent stability.
[0017] The preparation method of this invention utilizes low-cost raw materials, has a short synthesis time, low synthesis temperature, simple steps, minimal environmental impact, is non-toxic, consumes little energy, has a higher yield, and is conducive to large-scale industrial production, thus having a promising future. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the structure of the polyacid metal cluster prepared in Example 1;
[0019] Figure 2 HAADF-STEM and SEM images of the polyacid metal clusters prepared in Example 1;
[0020] Figure 3 TEM image of the polyacid metal clusters prepared in Example 1;
[0021] Figure 4 Raman images of the polyacid metal clusters prepared in Examples 1 and 4;
[0022] Figure 5 Linear sweep voltammetry (LSV) curves of the oxygen evolution reaction (OER) of the polyacid metal clusters prepared in Example 1 and the conventional nickel-based catalyst prepared in Comparative Example 1;
[0023] Figure 6 Linear sweep voltammetry (LSV) curves of the urea oxidation reaction (UOR) of the polyacid metal clusters prepared in Example 1 and the conventional nickel-based catalyst prepared in Comparative Example 1.
[0024] Figure 7 Chronopotential curves of the polyacid metal clusters prepared in Example 1 and the conventional nickel-based catalyst prepared in Comparative Example 1. Detailed Implementation
[0025] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.
[0026] A method for preparing polyacid metal clusters includes the following steps:
[0027] S1: Add a metal salt with a mass content of 3-22% and a multidentate chelate ligand with a molecular weight of 1000-50000 to a volume of 5mL-100mL of deionized water to obtain a catalyst precursor.
[0028] S2: Pour the catalyst precursor into the liner, place the liner in the reactor and react at 100~160℃ for 6~18h. Cool to room temperature, wash with ethanol 3-9 times, dry at 30-120℃ for 3-15h, and then grind into powder to obtain the polyacid metal cluster catalyst.
[0029] Example 1
[0030] A method for preparing polyacid metal clusters includes the following steps:
[0031] Step 1: Add 1.16 g of nickel nitrate hexahydrate and 53.3 μL of polyacrylic acid with a molecular weight of 2000 to 30 mL of water and disperse by ultrasonication to obtain the catalyst precursor;
[0032] Step 2: Pour the catalyst precursor into a 50 mL liner, place the liner in the reactor and react at 120℃ for 12 h. After cooling to room temperature, wash with ethanol 3 times, dry at 80℃ for 5 h, and grind into powder to obtain the catalyst.
[0033] Example 2
[0034] A method for preparing polyacid metal clusters includes the following steps:
[0035] Step 1: Add 1.16 g of nickel nitrate hexahydrate and 40 μL of polyacrylic acid with a molecular weight of 2000 to 30 mL of water and disperse by ultrasonication to obtain the catalyst precursor;
[0036] Step 2: Pour the catalyst precursor into a 50 mL liner, place the liner in the reactor and react at 120℃ for 12 h. After cooling to room temperature, wash with ethanol 3 times, dry at 80℃ for 5 h, and grind into powder to obtain the catalyst.
[0037] Example 3
[0038] A method for preparing polyacid metal clusters includes the following steps:
[0039] Step 1: Add 1.16 g of nickel nitrate hexahydrate and 80 μL of polyacrylic acid with a molecular weight of 2000 to 30 mL of water and disperse by ultrasonication to obtain the catalyst precursor;
[0040] Step 2: Pour the catalyst precursor into a 50 mL liner, place the liner in the reactor and react at 120℃ for 12 h. After cooling to room temperature, wash with ethanol 3 times, dry at 80℃ for 5 h, and grind into powder to obtain the catalyst.
[0041] Example 4
[0042] A method for preparing polyacid metal clusters includes the following steps:
[0043] Step 1: Add 0.904 g of nickel nitrate hexahydrate, 0.359 g of ferric nitrate nonahydrate and 53.3 μL of polyacrylic acid with a molecular weight of 2000 to 30 mL of water and disperse by ultrasonication to obtain the catalyst precursor;
[0044] Step 2: Pour the catalyst precursor into a 50 mL liner, place the liner in the reactor and react at 120℃ for 12 h. After cooling to room temperature, wash with ethanol 3 times, dry at 80℃ for 5 h, and grind into powder to obtain the catalyst.
[0045] Comparative Example 1
[0046] A method for preparing a conventional nickel-based hydroxide catalyst (Ni(OH)2) includes the following steps:
[0047] Step 1: Add 1.16 g of nickel nitrate nonahydrate to 30 mL of water to obtain the catalyst precursor;
[0048] Step 2: Pour the catalyst precursor into a 50 mL liner, place the liner in the reactor and react at 120°C for 12 h. After cooling to room temperature, wash with ethanol 3 times, dry at 80°C for 5 h, and grind into powder to obtain the nickel-based hydroxide catalyst.
[0049] The conventional nickel-based hydroxide catalyst (Ni(OH)2) prepared in Comparative Example 1 of this application, the polyacid metal cluster (NiOOH@PAA) prepared in Example 1, and commercial RuO2 (purchased from Aladdin) were directly used as working electrodes. Hg / HgO (filled with 20% KOH) and Pt wire were used as reference and counter electrodes, respectively. Tests were conducted in an alkaline medium of 1.0 M KOH at a scan rate of 5 mV / s, and the LSV curves of Ni(OH)2, NiOOH@PAA, and commercial RuO2 were measured sequentially. The test results are as follows: Figure 5 As shown, the catalytic activity of NiOOH@PAA prepared in Example 1 is significantly improved compared to Ni(OH)2 and commercial RuO2. Notably, at a current density of 10 mA / cm², the catalytic activity is significantly enhanced. 2 At that time, the potential of NiOOH@PAA was only 1.53 V, which was 76 mV and 64 mV lower than that of Ni(OH)2 and commercial RuO2, respectively.
[0050] In addition, the conventional nickel-based hydroxide catalyst (Ni(OH)2) prepared in Comparative Example 1 of this application, the polyacid metal cluster (NiOOH@PAA) prepared in Example 1, and commercial RuO2 (purchased from Aladdin) were directly used as working electrodes. Hg / HgO (filled with 20% KOH) and Pt wire were used as reference and counter electrodes, respectively. Tests were conducted in an alkaline medium of 1.0 M KOH and 0.33 M Urea at a scan rate of 5 mV / s. The LSV curves of Ni(OH)2, NiOOH@PAA, and commercial RuO2 were measured sequentially. The test results are as follows: Figure 6As shown, the catalytic activity of NiOOH@PAA prepared in Example 1 is significantly improved compared to Ni(OH)2 and commercial RuO2. Notably, at a current density of 10 mA / cm², the catalytic activity is significantly enhanced. 2 At that time, the potential of NiOOH@PAA was only 1.326 V, and the required overpotential was only 96 mV (compared to the theoretical voltage of traditional water electrolysis), which is 52 mV and 255 mV lower than Ni(OH)2 and commercial RuO2, respectively, and 240 mV lower than the oxygen evolution reaction overpotential of the material.
[0051] The NiOOH@PAA prepared in Example 1 was subjected to a fixed current density of 10 mA / cm². 2 Stability tests were conducted under alkaline conditions with 1.0 M KOH. The test results are as follows: Figure 7 As shown, the image presents an almost flat line, and the overpotential remains unchanged after about 10 hours, indicating that it has excellent stability.
[0052] Figure 1 This is a schematic diagram of the material structure of the polyacid-metal cluster in Example 1. It can be seen that the catalyst uses nickel hydroxyoxide (NiOOH) as its basic framework structure. The carboxylic acid groups anchor the metal sites with their strong coordination ability, forming stable coordination bonds with the metal ions. Simultaneously, the polyacid groups guide the material assembly into metal clusters through synergistic effects. In this complex assembly process, dynamic interactions and synergistic effects exist between the components. Through precise molecular recognition and self-assembly mechanisms, a regular layered structure is ultimately constructed.
[0053] Figure 2 HAADF-STEM and SEM images of the polyacid metal clusters prepared in Example 1 are shown. The images reveal a distinct lamellar morphology, with the layers interwoven or extended. Under dark-field imaging conditions, the contours and distribution of the layers are highlighted by differences in electron scattering, exhibiting rich structural details and unique two-dimensional structural characteristics. The highly developed porous lamellar structure is interconnected, forming a complex yet orderly network. This architecture significantly increases the specific surface area of the material, providing a structural basis for its applications in adsorption, catalysis, or energy storage, and contributing to improved efficiency in mass transport and interfacial reactions.
[0054] Figure 3The TEM image of Example 1 shows that the metal clusters in the material are uniformly distributed, indicating that under the conditions of this example, the metal clusters achieved good dispersion in the matrix without obvious agglomeration, demonstrating the effectiveness of cluster distribution control during material preparation. Clearly discernible lattice fringes were further observed in the high-resolution region of the image (inset bar is 1 nm). This phenomenon indicates that the metal clusters have a well-defined crystal structure, and the lattice fringes correspond to specific interplanar spacings, reflecting good crystallinity of the clusters. This provides important microstructural evidence for the study of the structure-property relationship of the material and also confirms the order and regularity of the material prepared in Example 1 at the crystal structure level.
[0055] Figure 4 Raman images of the polyacid metal clusters prepared in Examples 1 and 4, showing the in-plane stretching vibration peaks in the Ni-O plane (located at 480-500 cm⁻¹). -1 The Ni-O out-of-plane stretching vibration peak (located at 480-500 cm⁻¹) is similar to that of the Ni-O plane. -1 The presence of ), combined with the Raman characteristic vibrational modes of nickel hydroxyl oxide (NiOOH) in the literature, confirms the formation of the NiOOH structure. Simultaneously, at 1044 cm⁻¹... -1 The presence of peaks on both sides may be related to the superoxide element or related structures in NiOOH, while in Example 4 (Fe 3+ The Ni-O peak shifts in the doped system, a phenomenon that can be attributed to Fe. 3+ Ions and Ni 3+ The lattice distortion caused by the difference in ionic radii indicates that Fe 3+ Successfully doped into the NiOOH lattice. And 1470 cm⁻¹ -1 The peaks on the left and right correspond to the stretching vibrations (ν(C=O)) of the C=O bonds in the carboxylic acid groups of polyacrylic acid (PAA), further confirming the successful coordination of PAA in the composite system.
[0056] For any points not covered above, existing technologies shall apply.
[0057] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for producing a polyacid metal cluster, characterized by, A metal salt, water, and a multidentate chelating ligand are subjected to a hydrothermal reaction. The resulting solid is washed, centrifuged, and dried to obtain a polyacid metal cluster. The multidentate chelating ligand is polyacrylic acid. The metal salt is a nickel salt or a combination of a nickel salt and an iron salt.
2. The preparation method according to claim 1, characterized in that, The molecular weight of the multidentate chelating ligand ranges from 1,000 to 50,000, and each repeating unit contains at least one carboxylic acid group.
3. The preparation method according to claim 1, characterized in that, The hydrothermal reaction temperature is 100-160℃, and the reaction time is 6-18 h.
4. The preparation method according to claim 1, characterized in that, The washing process involves washing the solution several times with deionized water and anhydrous ethanol until the solution is clear.
5. The preparation method according to claim 1, characterized in that, The metal salt is one or more of the following: nitrate, chloride, and sulfate.
6. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the metal salt, water, and multidentate chelate ligand is 0.005~3.0 g: 5~100 mL: 5~1500 uL.
7. A polyacid metal cluster, characterized in that, It is obtained by the preparation method described in any one of claims 1-6.
8. An application of the polyacid metal cluster as described in claim 7, characterized in that, Catalysts used in water electrolysis and urea oxidation.