Vanadium-doped waugh-type heteropolyacid salt material, and preparation method and application thereof

Abstract

This invention discloses a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The preparation method of [OH)5]·7H2O material belongs to the field of inorganic materials. This method involves dissolving cobalt nitrate hexahydrate, potassium permanganate, ammonium fluoride, ammonium molybdate tetrahydrate, and ammonium metavanadate in pure water, reacting them at a constant temperature in a hydrothermal reactor, filtering after the reaction, drying the resulting product in an oven, calcining it in a muffle furnace, and then cooling it to obtain the target product. This invention effectively improves the pseudocapacitive performance of Waugh-type heteropolyacid salts through V element doping. The resulting material exhibits a microscopic structure of alternating lamellar and blocky structures. This structure facilitates electrolyte wetting and penetration, significantly enhancing the pseudocapacitive contribution. Simultaneously, the interconnected lamellar network constructs a continuous conductive pathway, facilitating rapid electron transport between the active material and the current collector.

Description

Technical Field

[0001] This invention discloses a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 [OH)5]·7H2O materials, their preparation methods and applications, belong to the field of supercapacitor technology in inorganic materials. Background Technology

[0002] With the global energy crisis and environmental pollution becoming increasingly severe, the development of efficient, clean, and sustainable electrochemical energy storage technologies has become an urgent need in the energy sector. Supercapacitors, as a novel energy storage device situated between traditional capacitors and secondary batteries, have shown broad application prospects in the energy storage field due to their advantages such as high power density, rapid charge-discharge capability, excellent cycle life, and environmental friendliness. Electrode materials, as the core component of supercapacitors, directly determine the energy storage capacity and lifespan of the device. Therefore, designing and fabricating electrode materials that possess both high specific capacity and good cycle stability has become a key direction for overcoming the technological bottlenecks of supercapacitors.

[0003] Transition metal oxides are considered highly promising pseudocapacitive electrode materials due to their abundant resources, low cost, environmental friendliness, and high theoretical specific capacitance. Among them, cobalt-based oxides are particularly promising because they can achieve Co… 2+ / Co 3+ Reversible redox reactions have attracted much attention; manganese-based oxides have been widely studied due to their large reserves and diverse valence states; molybdenum-based materials have become ideal candidate systems for pseudocapacitors due to their excellent redox activity. However, single-component transition metal oxides generally suffer from inherent defects such as low intrinsic conductivity and slow ion diffusion kinetics, and their crystal structure is prone to collapse during long-term charge-discharge cycles, leading to a significant decrease in actual specific capacity, which seriously restricts their practical applications. Summary of the Invention

[0004] This invention provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 [OH)5]·7H2O material is proposed to address the low conductivity of existing transition metal oxide electrode materials. The preparation process is as follows: cobalt nitrate hexahydrate, potassium permanganate, ammonium fluoride, ammonium molybdate tetrahydrate, and ammonium metavanadate are added sequentially to pure water and stirred until homogeneous. After thorough mixing, the solution is transferred to a hydrothermal reactor and placed in an oven for constant-temperature reaction. After the reaction is complete, the product is removed, washed, dried at a constant temperature, and then calcined in a muffle furnace. Cooling in the furnace yields the target product. This synthesis method is simple to operate, uses inexpensive raw materials, and is suitable for large-scale industrial applications.

[0005] The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] of this invention 27The XRD pattern of the [OH)5]·7H2O material exhibits characteristic diffraction peaks at diffraction angles of 11.37°, 15.37°, 18.75°, 22.43°, 25.90°, 37.19°, and 44.10°; its XPS pattern shows characteristic peaks at binding energies of 641 eV and 653.25 eV, 803.1 eV, 232.08 eV, 235.23 eV, 530.01 eV, and 531.94 eV; and its infrared spectrum shows a peak at a wavenumber of 586.36 cm⁻¹. -1 943.19 cm -1 906.54 cm -1 1625.99 cm -1 and 3358.06 cm -1 It has a characteristic absorption peak.

[0006] The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] of this invention 27 The preparation method of [OH)5]·7H2O material includes the following steps:

[0007] The first step is to disperse cobalt nitrate hexahydrate in deionized water, then add potassium permanganate and ammonium fluoride in sequence, and stir until well mixed.

[0008] The second step is to add ammonium molybdate tetrahydrate and ammonium metavanadate and stir until homogeneous. The resulting mixed solution is then transferred to a hydrothermal reactor and placed in an oven for constant temperature reaction, followed by natural cooling.

[0009] The third step is to remove the product from the hydrothermal reactor, clean and filter it, and then place the filter cake in an oven to dry it.

[0010] The fourth step involves calcining the dried product in a muffle furnace and then cooling it to obtain vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27 (OH)5]·7H2O material.

[0011] In the above technical solution, the molar ratio of cobalt nitrate hexahydrate, potassium permanganate and ammonium fluoride in the first step is 3:1:12.

[0012] In the above technical solution, the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate in the second step can be selected as 99:1, 98:2, 97:3 or 95:5.

[0013] In the above technical solution, the sum of the molar amounts of ammonium molybdate tetrahydrate and ammonium metavanadate in the second step is equal to the sum of the molar amounts of cobalt nitrate hexahydrate and potassium permanganate in the first step.

[0014] In the above technical solution, the constant temperature reaction temperature in the second step is 140℃, and the reaction time is 8 hours.

[0015] In the above technical solution, the third step uses pure water to clean and filter the product. Specifically, the product is placed in pure water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, and then filtered. This cleaning process is repeated 3 times.

[0016] In the above technical solution, the drying temperature in the third step is 80℃ and the drying time is 1 hour.

[0017] In the above technical solution, the calcination temperature in the fourth step is 300℃, the constant temperature calcination time is 3 hours, the time to heat up to the calcination temperature is 2 hours, and the time to cool down to below 200℃ after calcination is 2 hours.

[0018] The present invention also provides the above-mentioned vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 Application of [OH)5]·7H2O material in supercapacitors. Beneficial effects of the invention

[0019] This invention provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The preparation method of [OH)5]·7H2O material is simple, convenient, and uses widely available and inexpensive raw materials, showing good prospects for industrial production and promotion. The introduction of V doping effectively enhances the pseudocapacitive performance of this Waugh-type heteropolyacid salt material. Microstructural characterization shows that the obtained material exhibits an alternating stacked morphology of plate and block structures. This structure facilitates the full wetting and penetration of the electrolyte within the material, thus significantly enhancing the pseudocapacitive contribution. Simultaneously, the overlapping lamellar network forms a continuous conductive pathway, facilitating rapid electron transport between the active material and the current collector, further improving the electrochemical response performance of the material and providing a new technical path for the design and development of high-performance pseudocapacitive materials. Attached Figure Description

[0020] Figure 1 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 [(OH)5]·7H2O XRD pattern of the material.

[0021] Figure 2 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 Three-dimensional crystal packing structure diagram of (OH)5]·7H2O material.

[0022] Figure 3 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 SEM image of the material [(OH)5]·7H2O.

[0023] Figure 4 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 Elemental distribution diagrams of the material [OH)5]·7H2O; where: (a) is the Mn elemental distribution diagram, (b) is the Co elemental distribution diagram, (c) is the Mo elemental distribution diagram, and (d) is the O elemental distribution diagram.

[0024] Figure 5 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 XPS images of the material [OH)5]·7H2O; where: (a) is the full spectrum scan; (b) is the Mn 2p fine spectrum; (c) is the Co 2p fine spectrum; (d) is the Mo3d fine spectrum; and (e) is the O 1s fine spectrum.

[0025] Figure 6 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 Infrared spectrum of the material [(OH)5]·7H2O.

[0026] Figure 7 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 3 of this invention 27 Raman spectrum of the material [(OH)5]·7H2O.

[0027] Figure 8 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 5 of this invention 27 [OH)5]·7H2O material at a current density of 0.001 A / cm 2 GCD plot at time.

[0028] Figure 9 The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 5 of this invention 27 CV plot of the (OH)5]·7H2O material at a scan rate of 0.005V / s.

[0029] Figure 10The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] in Example 5 of this invention 27 Specific capacity diagram of (OH)5]·7H2O material. Detailed Implementation

[0030] The present invention is further described below through specific examples. However, these examples are merely exemplary and are not limited to the scope of protection of the present invention. In the following examples, unless otherwise specified, the reagents, materials, and instruments used are all conventional reagents, materials, and instruments, all of which are commercially available. The reagents involved can also be synthesized by conventional synthetic methods.

[0031] Example 1

[0032] This embodiment provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The specific preparation process of the (OH)5]·7H2O material is as follows.

[0033] First, weigh 0.87309 g of cobalt nitrate hexahydrate and disperse it in deionized water. After stirring and dissolving, add 0.15803 g of potassium permanganate and 0.44448 g of ammonium fluoride in sequence, and continue stirring until the mixture is homogeneous.

[0034] In the second step, 4.8941 g of ammonium molybdate tetrahydrate and 0.0047 g of ammonium metavanadate were added to the above mixed solution in sequence, and the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate was controlled at 99:1. The mixture was stirred continuously for 2 hours.

[0035] The third step is to transfer the thoroughly stirred mixture to a hydrothermal reactor, place it in an oven and react at a constant temperature of 140 °C for 8 hours, and then allow it to cool naturally to room temperature after the reaction is complete.

[0036] The fourth step involves removing the reaction product from the hydrothermal reactor and cleaning and filtering it with deionized water. Specifically, the product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, followed by filtration. This cleaning process is repeated three times.

[0037] Fifth step: Place the cleaned filtered product in an oven and dry it at 80 ℃ for 1 hour.

[0038] Step 6: The dried product is placed in a muffle furnace for calcination at 300 °C for 2 hours, followed by constant-temperature calcination for 3 hours. After calcination, the product is cooled in the furnace to below 200 °C for 2 hours, ultimately yielding vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27(OH)5]·7H2O material.

[0039] Example 2

[0040] This embodiment provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The specific preparation process of the (OH)5]·7H2O material is as follows.

[0041] First, weigh 0.87309 g of cobalt nitrate hexahydrate and disperse it in deionized water. After stirring and dissolving, add 0.15803 g of potassium permanganate and 0.44448 g of ammonium fluoride in sequence, and continue stirring until the mixture is homogeneous.

[0042] In the second step, 4.8446 g of ammonium molybdate tetrahydrate and 0.00935 g of ammonium metavanadate were added to the above mixed solution in sequence, and the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate was controlled at 98:2. The mixture was stirred continuously for 2 hours.

[0043] The third step is to transfer the thoroughly stirred mixture to a hydrothermal reactor, place it in an oven and react at a constant temperature of 140 °C for 8 hours, and then allow it to cool naturally to room temperature after the reaction is complete.

[0044] The fourth step involves removing the reaction product from the hydrothermal reactor and cleaning and filtering it with deionized water. Specifically, the product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, followed by filtration. This cleaning process is repeated three times.

[0045] Fifth step: Place the cleaned filtered product in an oven and dry it at 80 ℃ for 1 hour.

[0046] Step 6: The dried product is placed in a muffle furnace for calcination at 300 °C for 2 hours, followed by constant-temperature calcination for 3 hours. After calcination, the product is cooled in the furnace to below 200 °C for 2 hours, ultimately yielding vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27 (OH)5]·7H2O material.

[0047] Example 3

[0048] This embodiment provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The specific preparation process of the (OH)5]·7H2O material is as follows.

[0049] First, weigh 0.87309 g of cobalt nitrate hexahydrate and disperse it in deionized water. After stirring and dissolving, add 0.15803 g of potassium permanganate and 0.44448 g of ammonium fluoride in sequence, and continue stirring until the mixture is homogeneous.

[0050] In the second step, 4.7952 g of ammonium molybdate tetrahydrate and 0.01404 g of ammonium metavanadate were added to the above mixed solution in sequence, and the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate was controlled at 97:3. The mixture was stirred continuously for 2 hours.

[0051] The third step is to transfer the thoroughly stirred mixture to a hydrothermal reactor, place it in an oven and react at a constant temperature of 140 °C for 8 hours, and then allow it to cool naturally to room temperature after the reaction is complete.

[0052] The fourth step involves removing the reaction product from the hydrothermal reactor and cleaning and filtering it with deionized water. Specifically, the product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, followed by filtration. This cleaning process is repeated three times.

[0053] Fifth step: Place the cleaned filtered product in an oven and dry it at 80 ℃ for 1 hour.

[0054] Step 6: The dried product is placed in a muffle furnace for calcination at 300 °C for 2 hours, followed by constant-temperature calcination for 3 hours. After calcination, the product is cooled in the furnace to below 200 °C for 2 hours, ultimately yielding vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27 (OH)5]·7H2O material.

[0055] X-ray diffraction combined with Rietveld full-spectrum fitting was used to analyze V-doped Waugh-type [Mn(H2O)4][CoMo9O] grown in situ on a nickel foam substrate. 27 The phase structure of the (OH)5]·7H2O electrode material was characterized. Figure 1The XRD results showed that all the characteristic diffraction peaks of the sample were in high agreement with the standard card PDF#97-017-3400, and could be clearly attributed to the diffraction signals of each crystal plane of the Waugh-type compound. The characteristic peaks at 11.37°, 15.37°, 18.75°, 22.43°, 25.90°, 37.19° and 44.10° corresponded to the (110), (012), (211), (122), (401), (143) and (054) crystal planes, respectively, confirming that the synthetic route successfully prepared pure phase Waugh-type heteropolyacid salt crystals with complete coordination water and crystal water structures. The Waugh-type crystal structure is complete and ordered. The presence of a large amount of coordination water and crystal water in its structure not only provides abundant reversible redox active centers for Mo, Co, and Mn multimetals, but also helps to build interconnected electrolyte ion diffusion channels. The introduced V doping can further synergistically enhance the pseudocapacitive contribution of the supercapacitor, resulting in a synergistic effect on the overall energy storage performance.

[0056] Figure 2 It shows the Waugh type [Mn(H2O)4][CoMo9O] 27 The structure exhibits a three-dimensional crystal stacking structure of [(OH)5]·7H2O. In this structure, the Co atom at the heteropoly anion center is tightly wrapped by nine MoO6 octahedra connected by shared vertices and edges via oxygen bridges, forming a cage-like anion cluster [CoMo9O] modified with five bridged hydroxyl groups. 27 (OH)5] 2- The Mn center forms a glycocation [Mn(H2O)4] with four coordinated water molecules. 2+ The polyacid units are dispersed in the interstitial sites between adjacent heteropolyanion clusters, balancing the negative charge of the framework through electrostatic attraction and intermolecular hydrogen bonding, and crosslinking the discrete polyacid units into a long-range ordered three-dimensional lattice. Furthermore, seven free lattice water molecules are distributed in the intercellular voids; these coordinated waters, framework hydroxyl groups, and lattice water together construct interconnected hydrophilic channels within the crystal, providing a structural basis for the rapid transport of electrolyte ions. From the perspective of supercapacitor electrode applications, the rigid Waugh-type cage-like framework can effectively buffer the lattice strain caused by ion insertion and extraction during charging and discharging, thereby significantly improving the cycle stability of the electrode. The abundant bridging oxygen, hydroxyl groups, and hydrated groups within the crystal can significantly improve the wettability of the electrolyte to the electrode material, shorten the ion diffusion path, and contribute to improved rate performance. Simultaneously, the three transition metal ions Co, Mn, and Mo, uniformly dispersed in the ordered framework, can undergo multiple reversible redox reactions, synergistically providing a large number of pseudocapacitive active sites; while the naturally formed regular channels of the three-dimensional stacked structure facilitate the full exposure of the active surface and the efficient penetration of electrolyte ions.

[0057] Figure 3The SEM characterization results clearly revealed the Waugh-type [Mn(H2O)4][CoMo9O] 27 The microstructure of [OH)5]·7H2O was analyzed. The sample exhibited regular elongated sheet-like and blocky morphologies, with crystal sizes ranging from submicron to several micrometers. The crystal surfaces were smooth and flat with distinct crystal contours, confirming the material's excellent crystal integrity. Numerous sheet-like crystals were interleaved and stacked to form loose aggregates, and the interstices between the sheets created a rich micron-scale pore structure, which is beneficial for electrolyte wetting and ion transport. Analysis of the structure-performance relationship of electrochemical energy storage reveals that the aforementioned lamellar staggered stacking structure has multiple beneficial effects on the performance of supercapacitors. First, the open channels between the lamellar crystals can significantly improve the wetting efficiency of the electrolyte and shorten the ion diffusion distance, thereby optimizing the rate response of the electrode. Second, the flat and exposed crystal faces provide fully exposed redox active sites for Co, Mn, and Mo multi-metals, which is beneficial to enhancing the pseudocapacitive contribution. Third, the interconnected lamellar crystal network constructs a continuous conductive path, which is conducive to the rapid transport of electrons between the active material and the current collector. In addition, the lamellar crystal framework can effectively buffer the lattice stress caused by ion insertion and extraction during charging and discharging, suppress the structural pulverization and shedding of the active material, and thus significantly improve the long-cycle stability of the electrode.

[0058] Figure 4 It is of the Waugh type [Mn(H2O)4][CoMo9O] 27 Elemental distribution diagram of [OH)5]·7H2O Figure 4 (a) is a distribution map of Mn elements. Figure 4 (b) is a distribution map of Co element. Figure 4 (c) is a distribution map of Mo element. Figure 4 (d) shows the distribution of O element. The signal regions of the four elements highly overlap, and the signal intensity distribution is continuous and uniform, which intuitively indicates that in the Waugh-type heteropolyacid salt obtained by hydrothermal synthesis, the Mn, Co, and Mo metal sites have been uniformly dispersed at the nanometer to micrometer scale within the crystal framework, without the appearance of metal phase segregation or oxide agglomeration.

[0059] Figure 5 It is of the Waugh type [Mn(H2O)4][CoMo9O] 27 XPS plot of [(OH)5]·7H2O. Figure 5 a is the XPS full-scan spectrum of Waugh-type heteropolyacid salts, clearly showing the characteristic photoelectron emission peaks of Mn 2p, Co 2p, Mo 3d, and O 1s. Figure 5 In the fine spectrum of b's Mn 2p orbitals, the orbitals split into Mn 2p. 3 / 2 and Mn 2p 1 / 2Two sets of spin bimodals have binding energies at approximately 641 eV and 653.25 eV, respectively; among them, Mn 2p 3 / 2 The deconvolution can be divided into three components, which are assigned to Mn in sequence. 2+ (640.39 eV), Mn 3+ (641.94 eV) and Mn 4+ (645.25 eV) indicates that the Mn on the material surface exhibits a multi-valence coexistence characteristic, and this multi-level redox couple provides a rich source of activity for pseudocapacitance. Figure 5 In the Co 2p spectrum of c, Co 2p can be observed. 3 / 2 and Co2p 1 / 2 Co 2p 3 / 2 Further fitting to Co 3+ (780.7 eV) and Co 2+ Two main peaks (784.36 eV), the latter accompanied by a satellite peak at 796.86 eV; Co 2p 1 / 2 The peak value is located at 803.1 eV, Co. 2+ / Co 3+ The reversible transformation of Co constitutes the core energy storage site of heteropoly anions. V doping modulates the electron cloud density around Co, thereby altering the Co composition. 2+ With Co 3+ The ratio of [specific components] improves the redox reaction kinetics. Figure 5 The 3d spectrum of Mo exhibits a standard spin-split doublet. 5 / 2 and Mo 3d 3 / 2 The peaks are located at 232.08 eV and 235.23 eV respectively, and the main peak is attributed to Mo. 6+ .exist Figure 5 In the O 1s spectrum of electron doping, the peak at 530.01 eV is attributed to the metal-oxygen bond, while the peak at 531.94 eV corresponds to the surface hydroxyl oxygen and coordinated water and water of crystallization. The presence of a large number of oxygen-containing hydrophilic groups is conducive to the construction of wetting channels and promotes the rapid diffusion of electrolyte ions. V doping can not only adjust the bond energy of the metal-oxygen bond, but also increase the surface hydroxyl content, thereby synergistically optimizing electrochemical performance.

[0060] To verify the integrity of the sample's framework structure and hydration state, vanadium-doped Waugh-type [Mn(H2O)4][CoMo9O] was subjected to [further analysis]. 27 The (OH)5]·7H2O sample was analyzed by infrared spectroscopy, such as Figure 6 As shown. Located at 943.19 cm. -1 and 906.54cm -1 The absorption peak can be attributed to the antisymmetric stretching vibration of the terminal oxygen Mo=O; 705.95 cm⁻¹ -1 and 648.08 cm-1 The absorption peak at 586.36 cm⁻¹ is attributed to the antisymmetric stretching vibration of Mo-O-Mo; while the absorption peak at 586.36 cm⁻¹ is attributed to the antisymmetric stretching vibration of Mo-O-Mo. -1 The low-frequency vibration peaks at this location can be attributed to the bending vibrations of Mo-O-Mo or the stretching vibrations of the Co-O bonds in the distorted octahedron. No significant frequency shift was observed in the aforementioned metal-oxygen framework vibration peaks, indicating that V... 5+ Doping did not cause significant changes in the framework topology, only resulting in localized lattice perturbations, confirming that vanadium doping enters the heteropolyanionic framework via substitution rather than forming independent oxide impurity phases. In the higher wavenumber region, at 3358.06 cm⁻¹... -1 The broad and strong absorption peak at 1625.99 cm⁻¹ is attributed to the OH stretching vibration of the water of crystallization and coordinated water. -1 The absorption peak at 1406.1 cm⁻¹ corresponds to the HOH bending vibration of water molecules. -1 The absorption peak at this point can be attributed to the deformation bending vibration of the bridging hydroxyl groups in the heteropoly anionic framework, which explains the [CoMo9O]... 27 (OH)5] 2- The presence of the hydroxyl group provides direct evidence. The characteristic peaks related to the hydration structure did not show significant shifts or splits induced by vanadium doping, indicating that the formation of the VO bond did not disrupt the coordination environment of the hydroxyl group within the framework, and the crystal water and coordination water structures within the framework were completely preserved. Considering all the infrared characteristic absorption peaks, this result is consistent with the target compound [Mn(H2O)4][CoMo9O] 27 The molecular structures of [(OH)5]·7H2O are highly similar, further confirming the successful construction of the Waugh-type framework and the effective maintenance of the water-containing structure.

[0061] Waugh type [Mn(H2O)4][CoMo9O 27 The Raman spectrum of the material [OH)5]·7H2O is shown below. Figure 7 As shown. In the low-frequency region, 81.94 cm -1 96.09 cm -1 114.92 cm -1 126.92 cm -1 and 153.46 cm -1 The Raman peak at that location is attributed to lattice vibrations and [CoMo9O] 27 (OH)5] 2- The overall skeletal bending vibration mode of the anion; 197.45 cm⁻¹ -1 216.51 cm -1 and 240.13 cm -1 The peak at this point can be attributed to the bending vibration of Mo-O-Mo and the deformation vibration of the Co-O bond. 289.66 cm⁻¹ -1 336.80 cm -1and 377.58 cm -1 The Raman peak at 472.24 cm⁻¹ can be attributed to the distorted vibrational mode of the MoO₆ octahedron. In the mid-frequency region, the peak at 472.24 cm⁻¹... -1 The peak at 667.70 cm⁻¹ can be attributed to the deformation vibration or antisymmetric stretching vibration of Mo-O-Mo. In the high-frequency region, the peak at 667.70 cm⁻¹... -1 The peak at 819.61 cm⁻¹ can be attributed to the symmetric stretching vibration of Mo-O-Mo. -1 The peak at 885.53 cm⁻¹ can be attributed to the symmetrical vibration of the MoO₆ octahedron; -1 935.44 cm -1 and 994.15 cm -1 The three strong peaks at this point belong to the symmetric and antisymmetric stretching vibration modes of Mo=O. It is noteworthy that at approximately 970 cm⁻¹... -1 No independent new peaks attributable to the stretching vibration of V=O were observed nearby. This may be attributed to the low doping level of V, whose vibrational signal is overshadowed by the strong, broad peak of the main Mo=O, or to the coupling between the V=O stretching vibration and the Mo=O vibration, which prevents the generation of a distinguishable independent Raman scattering peak. The aforementioned Raman characteristic peaks confirm that [CoMo9O] 27 (OH)5] 2- Successful construction of anionic framework structure.

[0062] Example 4

[0063] This embodiment provides a vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The specific preparation process of the (OH)5]·7H2O material is as follows.

[0064] First, weigh 0.87309 g of cobalt nitrate hexahydrate and disperse it in deionized water. After stirring and dissolving, add 0.15803 g of potassium permanganate and 0.44448 g of ammonium fluoride in sequence, and continue stirring until the mixture is homogeneous.

[0065] In the second step, 4.6963 g of ammonium molybdate tetrahydrate and 0.0047 g of ammonium metavanadate were added to the above mixed solution in sequence, and the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate was controlled at 99:1. The mixture was stirred continuously for 2 hours.

[0066] The third step is to transfer the thoroughly stirred mixture to a hydrothermal reactor, place it in an oven and react at a constant temperature of 140 °C for 8 hours, and then allow it to cool naturally to room temperature after the reaction is complete.

[0067] The fourth step involves removing the reaction product from the hydrothermal reactor and cleaning and filtering it with deionized water. Specifically, the product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, followed by filtration. This cleaning process is repeated three times.

[0068] Fifth step: Place the cleaned filtered product in an oven and dry it at 80 ℃ for 1 hour.

[0069] Step 6: The dried product is placed in a muffle furnace for calcination at 300 °C for 2 hours, followed by constant-temperature calcination for 3 hours. After calcination, the product is cooled in the furnace to below 200 °C for 2 hours, ultimately yielding vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27 (OH)5]·7H2O material.

[0070] Example 5

[0071] This embodiment provides a method for using vanadium-doped Waugh-type heteropolyacid salts [Mn(H2O)4][CoMo9O] 27 The method for preparing the working electrode of a supercapacitor by in-situ growth of [OH)5]·7H2O material on the surface of nickel foam is as follows.

[0072] The first step is to weigh out cobalt nitrate hexahydrate, potassium permanganate and ammonium fluoride according to the amounts described in Examples 1 to 4, disperse them in deionized water and stir until fully mixed.

[0073] In the second step, according to the amounts described in Examples 1 to 4, ammonium molybdate tetrahydrate and ammonium metavanadate are weighed and added to the mixed solution obtained in the first step, and stirred continuously for 2 hours.

[0074] The third step involves transferring the thoroughly stirred mixture to a hydrothermal reactor and adding a 1 cm × 1 cm × 0.15 cm nickel foam sheet to the reactor. The sealed hydrothermal reactor is then placed in an oven and reacted at a constant temperature of 140 °C for 8 hours. After the reaction is complete, the mixture is allowed to cool naturally to room temperature.

[0075] The fourth step is to remove the nickel foam from the hydrothermal reactor, clean and filter it with deionized water. Specifically, the product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, and then filtered. The above cleaning process is repeated 3 times.

[0076] Fifth step: Place the cleaned nickel foam in an oven and dry it at 80 ℃ for 1 hour.

[0077] Step 6: The dried nickel foam is placed in a muffle furnace for calcination at 300 ℃ for 2 hours, followed by constant-temperature calcination for 3 hours. After calcination, the foam is cooled in the furnace to below 200 ℃ for 2 hours, thus obtaining vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] grown in situ on the surface of the nickel foam. 27 [(OH)5]·7H2O working electrode.

[0078] Step 7: Using a platinum electrode as the counter electrode and a mercury oxide electrode as the reference electrode, the above-mentioned vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] is grown. 27 Nickel foam with [OH)5]·7H2O was used as the working electrode, and 3 mol / L KOH solution was used as the electrolyte. A three-electrode system was assembled and its electrochemical performance was tested. This in-situ growth method effectively avoids the use of conductive binders, which helps to reduce interfacial contact resistance and improve the overall conductivity and structural stability of the electrode.

[0079] Figure 8 Vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] grown in situ on nickel foam 27 [OH)5]·7H2O material at a current density of 0.001 A / cm 2 The GCD plots at different current densities show that the 5% V sample has the longest discharge time, while the discharge times of the 2% V, 1% V, and 3% V samples decrease sequentially, indicating that the 5% V doped material has high pseudocapacitive performance at this current density.

[0080] Figure 9 Vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] grown in situ on nickel foam 27 The CV curve of the (OH)5]·7H2O material at a scan rate of 0.005 V / s. All samples showed obvious redox characteristic peaks. With the increase of vanadium doping ratio, the peak current of the redox peak increased synchronously. The peak current of the 5% V doped sample was significantly higher than that of the 1% V and 2% V doped samples, followed by the 3% V doped sample. This indicates that appropriate vanadium doping can increase the redox couple and construct a synergistic energy storage system with the active sites of Mo, Co, and Mn.

[0081] Figure 10 Vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] grown in situ on nickel foam 27 Specific capacitance diagram of [OH)5]·7H2O material. The areal specific capacitance of the 3% V-doped sample is superior to the other three groups at high current densities, with a specific capacitance as high as 26.5 F·cm² at a current density of 0.002 A / cm².-2 The initial specific capacity of the 5% V, 2% V, and 1% V samples decreased sequentially. Furthermore, the 3% V sample exhibited the smallest capacity decay at high current densities, indicating optimal stability. When the vanadium doping concentration increased to 5%, excess V easily induced lattice distortion and aggregation of surface active sites, thus weakening ion transport kinetics. Therefore, the optimal vanadium doping concentration was 3%.

[0082] Based on the description in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] 27 The material, characterized by [OH)5]·7H2O, is characterized by, Its XRD pattern shows characteristic peaks at diffraction angles of 11.37°, 15.37°, 18.75°, 22.43°, 25.90°, 37.19°, and 44.10°; its XPS pattern shows characteristic peaks at binding energies of 641 eV, 653.25 eV, 803.1 eV, 232.08 eV, 235.23 eV, 530.01 eV, and 531.94 eV; and its infrared spectrum shows a peak at a wavenumber of 586.36 cm⁻¹. -1 943.19 cm -1 906.54 cm -1 1625.99 cm -1 and 3358.06 cm -1 It has a characteristic absorption peak.

2. The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] as described in claim 1 27 The preparation method of [(OH)5]·7H2O material is characterized by, Includes the following steps: The first step is to disperse cobalt nitrate hexahydrate in deionized water, then add potassium permanganate and ammonium fluoride in sequence, and stir until well mixed. The second step is to add ammonium molybdate tetrahydrate and ammonium metavanadate and stir until homogeneous. The resulting mixed solution is then transferred to a hydrothermal reactor and placed in an oven for constant temperature reaction, followed by natural cooling. The third step is to remove the product from the hydrothermal reactor, clean and filter it, and then place the filter cake in an oven to dry it. The fourth step involves calcining the dried product in a muffle furnace and then cooling it to obtain vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O]. 27 (OH)5]·7H2O material.

3. The preparation method according to claim 2, characterized in that, In the first step, the molar ratio of cobalt nitrate hexahydrate, potassium permanganate, and ammonium fluoride is 3:1:

12.

4. The preparation method according to claim 2, characterized in that, In the second step, the molar ratio of ammonium molybdate tetrahydrate to ammonium metavanadate is 99:1, 98:2, 97:3, or 95:

5.

5. The preparation method according to claim 2, characterized in that, In the second step, the sum of the molar amounts of ammonium molybdate tetrahydrate and ammonium metavanadate is equal to the sum of the molar amounts of cobalt nitrate hexahydrate and potassium permanganate in the first step.

6. The preparation method according to claim 2, characterized in that, In the second step, the constant temperature reaction temperature is 140℃, and the constant temperature reaction time is 8 hours.

7. The preparation method according to claim 2, characterized in that, In the third step, deionized water is used to clean and filter the reaction product. Specifically, the reaction product is dispersed in deionized water to form a suspension, ultrasonically treated in an ultrasonic cleaner for 2 minutes, and then filtered. The above cleaning operation is repeated 3 times.

8. The preparation method according to claim 2, characterized in that, In the third step, the drying temperature is 80℃ and the drying time is 1 hour.

9. The preparation method according to claim 2, characterized in that, In the fourth step, the calcination temperature is 300℃, the constant temperature calcination time is 3 hours, the time to raise the temperature to this temperature is 2 hours, and the time to cool down to below 200℃ after calcination is 2 hours.

10. The vanadium-doped Waugh-type heteropolyacid salt [Mn(H2O)4][CoMo9O] as described in claim 1 27 Application of [OH)5]·7H2O material in supercapacitors.

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