A sandglass type polyoxometalate material, a preparation method and application thereof

Abstract

The application discloses a sandglass-shaped polyoxometalate material and a preparation method and application thereof. A novel sandglass-shaped polyoxometalate material is prepared by a solvent-thermal synthesis method, and the structure thereof is systematically characterized by single crystal X-ray diffraction, infrared spectroscopy and the like. The results show that there is a rich and continuous hydrogen bond network in the crystal structure of the material, which provides an efficient transmission channel for the directional migration of protons and electrons, and can significantly accelerate the transfer rate of protons / electrons in the crystal framework. At the same time, a strong coordination effect and a synergistic effect are formed among the metal center, the organic ligand and the polyoxometalate anion in the material, not only realizing the ordered assembly of the structure units, but also effectively strengthening the structural stability of the crystal framework, and greatly improving the electrochemical stability of the material.

Description

Technical Field

[0001] This invention relates to the field of electrode materials, specifically to an hourglass-shaped polyoxometalate material, its preparation method, and its application. Background Technology

[0002] Polyoxometalates (POMs) are a class of cluster-based inorganic compounds constructed by coordination bonds between transition metal atoms and oxygen atoms. They possess unique advantages such as strong structural tunability, abundant redox active sites, and the ability to undergo reversible multi-electron redox reactions, making them a promising next-generation supercapacitor electrode material.

[0003] Polyoxometalates with well-ordered hydrogen bond networks exhibit significant performance advantages in supercapacitor energy storage due to their unique structural synergistic effects: the highly ordered hydrogen bond network provides protons with continuous jumping sites following the Grotthuss mechanism, constructing efficient and unobstructed proton transport channels, significantly improving the intrinsic proton conductivity of the material, thereby reducing electrode internal resistance and optimizing rate performance; the dynamic reversibility of hydrogen bonds ensures that the material maintains its self-supporting structural strength at room temperature, and the hydrogen bond network can uniformly anchor polyoxometalate clusters, avoiding agglomeration and stacking, ensuring that each active center fully participates in reversible redox reactions, maximizing pseudocapacitance utilization, and endowing the material with ultra-high specific capacitance.

[0004] Although hydrogen bond network structures offer a novel approach to optimizing the performance of polyoxometalate electrode materials, existing traditional polyoxometalate materials still suffer from several common technical defects in practical applications: First, the materials are easily dissolved and lost in polar electrolyte systems, and the continuous loss of active materials leads to extremely poor electrode cycle stability, failing to meet the requirements for long-term use; Second, the intrinsic electronic conductivity of the materials is low, limiting the charge transport rate, and the rate performance degrades significantly under high current density charge and discharge; Third, traditional preparation processes are cumbersome, have harsh reaction conditions, and high production costs, and the morphology and crystal structure of the products are poorly controllable, making it difficult to achieve precise control and stable mass production. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide an hourglass-shaped polyoxometalate material with novel structure, high conductivity, and high electrochemical stability.

[0006] This invention is achieved through the following technical solution: On one hand, the present invention provides an hourglass-shaped polyoxometalate material, wherein the molecular formula of the hourglass-shaped polyoxometalate material is H8Cd[Mo6O] 12 [(OH)3(HPO4)4]2·2Cl·2(HPy)·2Me2NH, where Py is pyridine and Me2NH is dimethylamine.

[0007] The hourglass-shaped polyoxometalate material described in this invention has a triclinic crystal system and a space group of [missing information]. P-1 The unit cell parameters are a =13.298(2) Å, b =13.314(2) Å, c =15.723(3) Å, α =112.498(7)°, β =103.961(7)°, γ =103.425(7)°, V =2326.7(7) Å 3 .

[0008] Furthermore, the present invention also provides a method for preparing the above-mentioned hourglass-shaped polyoxometalate material, comprising the following steps: (1) Add cadmium salt, molybdate, phosphoric acid and pyridine to deionized water and N,N-dimethylformamide, and then stir evenly at room temperature to obtain a reaction solution; (2) The reaction solution is transferred to the reaction vessel to react, and red blocky crystals are obtained, which are hourglass-shaped polyoxometalate materials.

[0009] In a preferred embodiment of the present invention, in step (1), the mass ratio of the cadmium salt to the molybdate is 1:(1-2.5).

[0010] In a preferred embodiment of the present invention, in step (1), the mass ratio of molybdate to pyridine is 1:(3-4).

[0011] In a preferred embodiment of the present invention, in step (1), the cadmium salt is selected from hydrated cadmium chloride.

[0012] In a preferred embodiment of the present invention, in step (1), the molybdate is selected from at least one of sodium molybdate or ammonium molybdate.

[0013] In a preferred embodiment of the present invention, in step (2), the reaction temperature is 140-160℃ and the reaction time is 2-4 days.

[0014] On the other hand, the present invention also provides the application of the above-mentioned hourglass-shaped polyoxometalate material as a supercapacitor electrode material.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention presents a novel hourglass-shaped polyoxometalate material synthesized using a solvothermal method. The structure was systematically characterized by single-crystal X-ray diffraction and infrared spectroscopy. The results show that the material's crystal structure contains a rich and continuous hydrogen bond network, providing an efficient transport channel for the directional migration of protons and electrons, significantly accelerating the proton / electron transfer rate within the crystal framework. Simultaneously, strong coordination and synergistic effects are formed among the metal center, organic ligands, and polyoxometalate anions, not only achieving the ordered assembly of structural units but also effectively strengthening the structural stability of the crystal framework and significantly improving the material's electrochemical stability. Attached Figure Description

[0016] Figure 1 This is a basic structural unit diagram of the hourglass-shaped polyoxometalate material prepared in Example 1; Figure 2 This is a diagram of the hydrogen-bonded chain structure of the internal components of the hourglass-shaped polyoxometalate material prepared in Example 1; Figure 3 This is a diagram of the internally assembled hydrogen-bonded layered structure of the hourglass-shaped polyoxometalate material prepared in Example 1; Figure 4 The infrared spectrum of the hourglass-shaped polyoxometalate material prepared in Example 1 is shown below. Figure 5 The powder X-ray diffraction pattern of the hourglass-shaped polyoxometalate material prepared in Example 1 is shown below. Figure 6 Cyclic voltammetry at different scan rates in sulfuric acid electrolyte solution is obtained by using the hourglass-shaped polyoxometalate material prepared in Example 1 as the working electrode.

[0017] Figure 7 The hourglass-shaped polyoxometalate material prepared in Example 1 is used as the working electrode, and the constant current charge-discharge diagram is shown in sulfuric acid electrolyte solution at different current densities.

[0018] Figure 8 The diagram shows the retention rate of the specific capacitance when the hourglass-shaped polyoxometalate material prepared in Example 1 is used as the working electrode and subjected to constant current charging / discharging for 500 cycles in a sulfuric acid electrolyte solution. Detailed Implementation

[0019] The present invention will be further illustrated below through specific embodiments. The following embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Example 1

[0020] 0.29 g of CdCl2·H2O, 0.49 g of Na2MoO4·2H2O, 2 mL of H3PO4 and 2 mL of pyridine were added to 6 mL of deionized water and 1 mL of N,N-dimethylformamide. The mixture was stirred at room temperature for 30 minutes, then transferred to a reaction vessel and reacted at 150 °C for 3 days. After cooling to a certain temperature, red blocky crystals were obtained, which are hourglass-shaped polyoxometalate materials with a yield of 31%. Example 2

[0021] Add 0.35 g of CdCl2·H2O and 0.55 g of (NH4)6Mo7O 24 · 4H2O, 2 mL H3PO4 and 2 mL pyridine were added to 6 mL deionized water and 1 mL N,N-dimethylformamide, and then stirred at room temperature for 30 minutes. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 3 days. After cooling to a certain temperature, red blocky crystals were obtained, which are hourglass-shaped polyoxometalate materials. Example 3

[0022] Add 0.25 g of CdCl2·H2O and 0.55 g of (NH4)6Mo7O 24 · 4H2O, 2 mL H3PO4 and 2 mL pyridine were added to 6 mL deionized water and 1 mL N,N-dimethylformamide, and then stirred at room temperature for 30 minutes. The mixture was then transferred to a reaction vessel and reacted at 160 °C for 2 days. After cooling to a certain temperature, red blocky crystals were obtained, which are hourglass-shaped polyoxometalate materials.

[0023] Example 4: Structural Characterization The hourglass-shaped polyoxometalate material prepared in Example 1 was characterized by infrared spectroscopy, and its infrared spectrum was obtained. Figure 4 As shown, 1024cm -1 960cm -1 743cm -1 496cm -1 These characteristic peaks correspond to hourglass-type polyacids {P4Mo6O} 31 In anions v (Mo=O), v (PO), v Characteristic vibrations of (Mo-O-Mo), 1623 cm⁻¹ -1 1465cm -1 The characteristic peaks correspond to the characteristic vibrations of pyridine molecules.

[0024] X-ray crystallography was performed on the hourglass-shaped polyoxometalate material prepared in Example 1. X-ray diffraction data were collected at 293 K using a Bruker SMART APEX II instrument with Mo-Kα radiation (λ = 0.71073) and ω and θ scanning modes. The structure of the hourglass-shaped polyoxometalate material prepared in Example 1 was analyzed using OLEX2 software. The X-ray crystallographic parameters are shown in Table 1.

[0025] Table 1 Crystallographic parameters of the compounds

[0026] Powder X-ray diffraction analysis was performed on the hourglass-shaped polyoxometalate material prepared in Example 1, as follows: Figure 5 As shown, the experimentally measured spectrum and the characteristic peak positions of the fitted spectrum of the crystal are consistent, which confirms that the experimentally obtained crystal structure is consistent with the crystal structure resolved using OLEX2.

[0027] X-ray diffraction analysis of the single crystal indicates that the hourglass-shaped polyoxometalate material prepared in Example 1 belongs to the triclinic crystal system. P-1 The space group consists of one Cd atom, two pyridine molecules, two dimethylamine molecules, and two {P4Mo6O} atoms. 31 Anions. Cd atoms and {P4Mo6O} 31 The O8, O9, and O19 atoms in the anion exhibit a six-coordinate structure. Numerous hydrogen bonds exist within the compound, with adjacent {P4Mo6O} atoms... 31 Hydrogen bonds between anions form supramolecular layered structures and supramolecular framework structures. Adjacent independent anions are interconnected by hydrogen bonds to form chain structures, and adjacent chains form supramolecular layered structures through hydrogen bonds (e.g., Figure 1-3 These abundant hydrogen bond networks facilitate the rapid shuttle of protons and electrons within the structure, which can significantly improve the conductivity of the prepared materials.

[0028] Example 5: Electrochemical Energy Storage Performance Measurement Preparation of the working electrode: The hourglass-shaped polyoxometalate material prepared in Example 1, Ketjen black, and polyvinylidene fluoride were mixed in a certain mass ratio (1:1:1), and then N-methylpyrrolidone was added to form a paste. The paste was ground for about 5 minutes, coated on the surface of carbon paper, and the electrode was dried at 60 °C overnight.

[0029] The hourglass-shaped polyoxometalate material prepared in Example 1 was subjected to electrochemical performance testing. The material was prepared as a carbon paper electrode as the working electrode in a 0.5 M sulfuric acid electrolyte solution, with silver / silver chloride as the reference electrode and platinum as the counter electrode. Scan rates of 20, 40, 60, 80, 100, 150, and 200 mV s were used. -1 Cyclic voltammetry tests were then performed on the electrode prepared from the hourglass-shaped polyoxometalate. The results are as follows: Figure 6 As shown, the material exhibits three pairs of reversible redox peaks, indicating that the prepared hourglass-shaped polyoxometalate material has a clear redox process.

[0030] At current densities of 1 A g -1 2 A g -1 3 A g -1 4 A g -1 5 A g -1 At that time, a constant current charge-discharge test was performed on the electrode prepared from the hourglass-shaped polyoxometalate material. The results are as follows: Figure 7 As shown, the maximum specific capacitance reaches 116mAh g. -1 This indicates that the prepared hourglass-shaped polyoxometalate material can be used as a high-rate electrode material.

[0031] The electrode prepared from this hourglass-shaped polyoxometalate material was subjected to cyclic charge-discharge tests in a 0.5 M sulfuric acid electrolyte solution, and the results are as follows: Figure 8 As shown, the specific capacitance retention rate remained stable at 91.5% after 500 charge / discharge cycles. This indicates that the prepared hourglass-shaped polyoxometalate material has high electrochemical stability.

[0032] In summary, the hourglass-shaped polyoxometalate material prepared by this invention not only has good redox activity and excellent conductivity, but also high electrochemical stability. It is a supercapacitor electrode material with high energy storage activity and shows potential application value in the field of energy storage.

Claims

1. An hourglass-shaped polyoxometalate material, characterized in that, The hourglass-shaped polyoxometalate material has the chemical formula H8Cd[Mo6O] 12 [(OH)3(HPO4)4]2·2Cl·2(HPy)·2Me2NH, where Py is pyridine and Me2NH is dimethylamine.

2. The hourglass-shaped polyoxometalate material according to claim 1, characterized in that, The hourglass-shaped polyoxometalate material has a triclinic crystal system and a space group of [missing information]. P-1 The unit cell parameters are a =13.298(2) Å, b =13.314(2) Å, c =15.723(3) Å, α =112.498(7)°, β =103.961(7)°, γ =103.425(7)°, V =2326.7(7) Å 3 .

3. A method for preparing an hourglass-shaped polyoxometalate material as described in claim 1 or 2, characterized in that, The steps include the following: (1) Cadmium salt, molybdate, phosphoric acid and pyridine are added to deionized water and N,N-dimethylformamide, and then stirred evenly at room temperature to obtain a reaction solution; the cadmium salt is selected from hydrated cadmium chloride; the molybdate is selected from at least one of sodium molybdate or ammonium molybdate; (2) The reaction solution is transferred to a reaction vessel to react and red blocky crystals are obtained, which are hourglass-shaped polyoxometalate materials; the reaction temperature is 140-160℃ and the reaction time is 2-4 days.

4. The method for preparing the hourglass-shaped polyoxometalate material according to claim 3, characterized in that, In step (1), the mass ratio of the cadmium salt to the molybdate is 1:(1-2.5).

5. The method for preparing the hourglass-shaped polyoxometalate material according to claim 3, characterized in that, In step (1), the mass ratio of molybdate to pyridine is 1:(3-4).

6. An application of the hourglass-shaped polyoxometalate material as described in claim 1 or 2, characterized in that, The hourglass-shaped polyoxometalate material is used as an electrode material for supercapacitors.

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