Polyoxometalate electrocatalytic oxygen evolution material, preparation method and application thereof

Abstract

Polyoxometalate electrocatalytic oxygen production material and its preparation method and application, relate to an electrocatalytic oxygen production material and its preparation method and application, belong to the field of electrochemical oxygen production energy storage materials.The present application solves the problems of high oxygen overpotential and large electrochemical impedance of the existing polyoxometalate as an electrode active material for electrocatalytic oxygen production.Method: I, dissolve Na2WO4 in deionized water, heat and constant temperature stirring, get No.1 solution; II, drop the hydrochloric acid aqueous solution containing SbCl3 in No.1 solution, constant temperature stirring, get No.2 solution; III, add CoCl2 to No.2 solution, stir well to get No.3 solution, add hydrochloric acid to adjust pH value, constant temperature stirring, cool to room temperature, filter, get the product.The polyoxometalate electrode material is used as a catalytic material for oxygen production.The material has good oxygen production performance; the material changes little before and after circulation.

Description

Technical Field

[0001] The present invention relates to an electrocatalytic oxygen-generating material and a preparation method and application thereof, belonging to the field of electrochemical oxygen-generating energy storage materials. Background Art

[0002] The overconsumption of traditional fossil fuels and the rapid deterioration of the environment have forced the development of safe, clean, and energy-dense renewable energy sources. Water electrolysis is an effective way to produce clean energy—hydrogen. However, the oxygen evolution reaction (OER), a half-reaction in water electrolysis, involves a four-electron transfer process, which limits the efficiency of hydrogen production. Therefore, the overpotential of the OER is crucial for electrocatalytic materials. Therefore, reducing the OER overpotential and increasing the active vacancy sites in the material are key to improving energy storage.

[0003] Polyoxometalates (POMs) offer the advantages of numerous active vacancy sites and high activity as electrocatalytic oxygen production materials. However, their weak conductivity and poor water solubility have hindered their widespread application. Therefore, reducing the overpotential for oxygen production in POMs and improving their conductivity are key research goals.

[0004] Most current strategies use polyoxometalates in combination with other substances or utilize modified polyoxometalates as electrode active materials. This can only change their morphology and composition, but it is difficult to fundamentally improve the performance of the material. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problems of high oxygen production overpotential and large electrochemical impedance of existing polyoxometalate electrode active materials for electrocatalytic oxygen production, and to provide a polyoxometalate electrocatalytic oxygen production material and its preparation method and application.

[0006] The molecular formula of the polyoxometalate electrode material is

[0007] Na9·[Na4(H2O) 18 Co3(H2O)4(OH){SbW9O 33}2]·20H2O, molecular weight is 4070, molecular structure formula is W 18 Co3Sb2[μ4-O]4[μ3-O]8[μ2-O] 32 Na 13 --[H2O] 42 [O] 22 [OH] - .

[0008] The preparation method of the polyoxometalate electrode material is carried out according to the following steps:

[0009] 1. Dissolve Na2WO4 in deionized water, heat to 90°C, and stir at 90°C for 10 minutes to obtain Solution 1; wherein the mass volume ratio of Na2WO4 to deionized water is (3-4) g: (20-30) mL;

[0010] 2. Add 1 mL of hydrochloric acid aqueous solution containing 0.3-0.4 g of SbCl3 dropwise to solution No. 1 and stir at 90°C for 10 minutes to obtain solution No. 2;

[0011] The concentration of hydrochloric acid in the hydrochloric acid aqueous solution containing SbCl3 is 6 mol / L;

[0012] 3. Add 0.1-0.2 g of CoCl2 to solution No. 2, stir thoroughly to obtain solution No. 3, add 6 mol / L hydrochloric acid to adjust the pH value to 6.2-6.5, stir at a constant temperature of 90°C for 1-2 hours, cool to room temperature, filter out the precipitate, and refrigerate the filtrate for 10-35 days to obtain the polyoxometalate material.

[0013] In step 1, the mass volume ratio of Na2WO4 to deionized water is 3.3 g: 20 mL.

[0014] In step 2, a hydrochloric acid aqueous solution containing 0.394 g of SbCl3 is added dropwise to solution No. 1.

[0015] The mass of CoCl2 in step 3 is 0.129g.

[0016] The polyoxometalate electrode material is used as a catalytic material to produce oxygen.

[0017] The structure of the polyoxometalate electrocatalytic oxygen production material of the present invention is composed of two centrosymmetric {SbW9O 33} 9- It is composed of polyoxyanions, three Co and three Na in the center and ten Na on the periphery. Among them, Sb is three-coordinated and forms a trihedral structure with the three surrounding O atoms. W is six-coordinated and connects the six surrounding O atoms to form a tetrahedral bipyramid structure. These polyhedral structures share O atoms to form two cage cluster structures containing 1 Sb, 9 W and 3 Co and Na elements. The remaining three sodium ions, a total of ten, are connected to the outside of the polyoxoacid ball, extending their "hands" to both sides of the polyoxoacid ball. At the same time, the Na5 in the periphery and the next Na7 are connected in a "branch" shape to form a one-dimensional chain. Two Na5 and Na7 are connected to form a ring, extending in a two-dimensional plane. Furthermore, Na5 and O23 are connected through hydrogen bond supramolecular interactions, extending in three-dimensional space to form a three-dimensional structure with ABAB arrangement.

[0018] The polyoxometalate electrocatalytic oxygen production material prepared by the present invention is a purely inorganic heteropolyoxometalate. When used as an electrocatalytic oxygen production material, it has an ultra-low oxygen production overpotential and stable cycling stability, exhibiting stable electrochemical performance. When using a 0.5 mol / L KOH solution as the electrolyte, the material exhibits an oxygen production overpotential of 329 mV, demonstrating excellent oxygen production performance. After 24 hours of cycling, the electrochemical transfer resistance of the electrode material is 2.6 Ω and 2.8 Ω, respectively, indicating little change before and after cycling. The polyoxometalate electrode material, when used as a catalytic material for oxygen production, has an overpotential of 329 mV, lower than the 450 mV of Co3O4, also used as an electrocatalytic oxygen production material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a molecular structure model diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0020] Figure 2 This is a one-dimensional structural diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0021] Figure 3 This is a two-dimensional structural diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0022] Figure 4 This is a three-dimensional structural diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0023] Figure 5 This is a solid ultraviolet absorption spectrum of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0024] Figure 6 This is a differential thermal gravimetric spectrum of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0025] Figure 7 This is the XRD pattern of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0026] Figure 8 This is a cyclic voltammetry curve of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0027] Figure 9 This is a graph of electrocatalytic oxygen production of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0028] Figure 10 This is a chronoamperometry diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1;

[0029] Figure 11This is the electrochemical impedance spectroscopy diagram of the polyoxometalate electrocatalytic oxygen production material prepared in Example 1 before and after the chronocurrent. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0031] Specific embodiment 1: The molecular formula of the polyoxometalate electrode material in this embodiment is

[0032] Na9·[Na4(H2O) 18 Co3(H2O)4(OH){SbW9O 33}2]·20H2O, molecular weight is 4070, molecular structure formula is W 18 Co3Sb2[μ4-O]4[μ3-O]8[μ2-O] 32 Na 13 --[H2O] 42 [O] 22 [OH] - .

[0033] Specific embodiment 2: The preparation method of the polyoxometalate electrode material in specific embodiment 1 is carried out according to the following steps:

[0034] 1. Dissolve Na2WO4 in deionized water, heat to 90°C, and stir at 90°C for 10 minutes to obtain Solution 1; wherein the mass volume ratio of Na2WO4 to deionized water is (3-4) g: (20-30) mL;

[0035] 2. Add 1 mL of hydrochloric acid aqueous solution containing 0.3-0.4 g of SbCl3 dropwise to solution No. 1 and stir at 90°C for 10 minutes to obtain solution No. 2;

[0036] The concentration of hydrochloric acid in the hydrochloric acid aqueous solution containing SbCl3 is 6 mol / L;

[0037] 3. Add 0.1-0.2 g of CoCl2 to solution No. 2, stir thoroughly to obtain solution No. 3, add 6 mol / L hydrochloric acid to adjust the pH value to 6.2-6.5, stir at a constant temperature of 90°C for 1-2 hours, cool to room temperature, filter out the precipitate, and refrigerate the filtrate for 10-35 days to obtain the polyoxometalate material.

[0038] Specific embodiment 3: This embodiment differs from specific embodiment 2 in that the mass volume ratio of Na2WO4 to deionized water in step 1 is 3.3 g:20 mL. Other aspects are the same as specific embodiment 2.

[0039] Specific embodiment 4: This embodiment differs from specific embodiment 2 or 3 in that in step 2, a hydrochloric acid aqueous solution containing 0.394 g of SbCl 3 is added dropwise to solution No. 1. Other aspects are the same as specific embodiment 2 or 3.

[0040] Specific embodiment 5: This embodiment differs from specific embodiments 2 to 4 in that the mass of CoCl2 in step 3 is 0.129 g. Other aspects are the same as those of specific embodiments 2 to 4.

[0041] Specific embodiment 6: The difference between specific embodiments 1 to 5 is that the polyoxometalate electrode material is used as a catalytic material for oxygen production. Other aspects are the same as specific embodiments 1 to 5.

[0042] The following examples are used to verify the effects of the present invention:

[0043] Example 1:

[0044] The preparation method of the polyoxometalate electrode material is carried out according to the following steps:

[0045] 1. Dissolve Na2WO4 in deionized water, heat to 90°C, and stir at 90°C for 10 minutes to obtain Solution 1; wherein the mass volume ratio of Na2WO4 to deionized water is 3.3g:20mL;

[0046] 2. Add 1 mL of hydrochloric acid solution containing 0.394 g of SbCl3 dropwise to solution No. 1 and stir at 90°C for 10 minutes to obtain solution No. 2;

[0047] The concentration of hydrochloric acid in the hydrochloric acid aqueous solution containing SbCl3 is 6 mol / L;

[0048] 3. Add 0.129 g of CoCl2 to solution No. 2 and stir thoroughly to obtain solution No. 3. Add 6 mol / L hydrochloric acid to adjust the pH to 6.2. Stir at a constant temperature of 90°C for 1 hour. Cool to room temperature, filter out the precipitate, and refrigerate the filtrate for 10 to 35 days to obtain a polymetallic acid electrode material, which is a blue-purple block compound.

[0049] The molecular formula of the polyoxometalate electrode material is:

[0050] Na9·[Na4(H2O) 18 Co3(H2O)4(OH){SbW9O 33}2]·20H2O.

[0051] The method for testing metal oxoate electrode materials is as follows:

[0052] 1. Cyclic voltammetry curves: In a typical three-electrode system, with a KOH solution of 0.5 mol / L as the electrolyte and a voltage window of -0.15 to 0 V, the cyclic voltammetry curves of the oxygen-producing electrode material were measured at scan rates of 10 mV / s, 20 mV / s, 40 mV / s, 60 mV / s, 80 mV / s, and 100 mV / s, respectively.

[0053] 2. Electrocatalytic oxygen evolution curve: OER performance measured in a typical three-electrode system using a 0.5 mol / L KOH solution as the electrolyte. When the current density is 10 mA / cm 2 When , the overpotential is 329mV.

[0054] 3. Chronoamperometric test: Under the condition of a three-electrode system (using a KOH solution with a concentration of 0.5 mol / L as the electrolyte solution) with a voltage window of 659 mV, there was no significant decrease in the current after 24 hours of circulation, indicating that the electrode material is very stable.

[0055] 4. AC impedance test: The AC impedance spectrum of the electrode material was tested before and after 24 hours of circulation (using a KOH solution with a concentration of 0.5 mol / L as the electrolyte solution). The electrochemical transfer resistance of the electrode material was 2.6 and 2.8 Ω, respectively, indicating that the electrode material did not change much before and after timing and had good stability.

[0056] The crystallographic parameters of the polyoxometalate electrode material described in this embodiment are shown in Table 1:

[0057] Table 1

[0058]

[0059]

[0060] (*R1=Σ||F o |-|F c || / Σ|F o |,wR2=[Σ(w(F o 2 -F c 2 ) 2 ) / Σ(wF o 2 ) 2 ] 1 / 2 ).

[0061] The bond length data of the polyoxometalate electrode material described in this embodiment are shown in Table 2:

[0062] Table 2

[0063]

[0064]

[0065] The bond angle data of the polyoxometalate electrode material described in this embodiment are shown in Table 3:

[0066] Table 3

[0067]

[0068]

[0069]

[0070]

[0071] The hydrogen bonding data of the polyoxometalate electrode material described in this embodiment are shown in Table 4:

[0072] Table 4

[0073]

[0074]

[0075] The infrared absorption spectrum of the polyoxometalate electrode material of this embodiment is shown in FIG. Figure 5 As shown. Figure 5 It can be seen that its characteristic peak is at 680cm -1 , 760cm -1 , 896cm -1 , respectively assigned to ν(Co-O a ),ν(W=O d ) and ν(WO b -W) stretching vibration absorption, at 2322cm -1 , 5850cm -1 The absorption peaks on the left and right are attributed to the vibration absorption of H2O, which is consistent with the crystal structure analysis.

[0076] The differential thermal gravimetric spectrum of the polyoxometalate electrode material of this embodiment is as follows: Figure 6 The polyoxometalate undergoes a three-step weight loss process. The first step, between 0°C and 100°C, involves the loss of crystalline water, with a weight loss rate of 7.9% (theoretical value: 10.92%). The second step, between 200°C and 300°C, involves the loss of lattice water, with a weight loss rate of 7.1%. Finally, between 300°C and 900°C, the crystal framework collapses, with a weight loss rate of 12%. This is consistent with crystal structure analysis.

[0077] The XRD pattern of the polyoxometalate electrode material of this embodiment is as follows Figure 7The figure describes the simulated XRD and experimental XRD patterns of the substance. The peaks of the tested XRD spectrum are basically consistent with those of the simulated XRD, indicating that the substance is a pure phase.

[0078] Electrode Fabrication: Cut carbon cloth into 1 x 1 cm pieces and rinse with sulfuric acid and deionized water. To prepare the electrode, a slurry was prepared using conductive carbon and polyoxometalate electrode materials in a 1:2 mass ratio using ethanol as the solvent. The well-dispersed slurry was evenly applied to the surface of the carbon cloth and dried at room temperature for 2 hours to form a uniform thin film electrode. A Nafion membrane (5 μL) was then applied to the slurry-laden carbon cloth and dried at room temperature.

[0079] The electrocatalytic performance of polyoxometalate electrode materials was tested using a CHI 660E electrochemical workstation.

[0080] Figure 8 The following are cyclic voltammograms of a polyoxometalate electrode material. In a typical three-electrode system, with a 0.5 mol / L KOH solution as the electrolyte, the material's cyclic voltammograms were measured at scan rates of 10 mV / s, 20 mV / s, 40 mV / s, 60 mV / s, 80 mV / s, and 100 mV / s, respectively, within a voltage window of -0.15 to 0 V. As can be seen from the figure, all of the cyclic voltammograms are approximately parallelogram-shaped, and their shapes do not change with increasing scan speed, indicating that the polyoxometalate electrode material has stable electrochemical performance.

[0081] Figure 9 The OER performance of polyoxometalate electrode materials in a three-electrode system was studied using a 0.5 mol / L KOH solution as the electrolyte. 2 When , the overpotential of the substance is 329mV, and it has strong oxygen production performance.

[0082] Figure 10 This is a chronoamperometry plot of the substance at an oxygen evolution overpotential of 329 mV in a three-electrode system using a 0.5 mol / L KOH solution as the electrolyte. This plot shows no significant difference in the chronoamperometry after 12 hours of testing, demonstrating its excellent electrochemical stability.

[0083] AC impedance test: Figure 11 The AC impedance spectrum of the metal oxoate electrode material was tested before and after 24 hours of chronoamperometry (using a 0.5 mol / L KOH solution as the electrolyte solution). Figure 11 Among them, ■ is before timing, ● is after timing), in the low frequency area ( Figure 11The electrochemical transfer resistances of the electrode materials (where ■ represents before timing and ● represents after timing) are 2.6Ω and 2.8Ω, respectively, demonstrating excellent stability. In the high-frequency region, the slope remains unchanged, indicating no change in electron diffusion capacity.

Claims

1. Polyoxometalate electrode material, characterized in that The molecular formula of the polyoxometalate electrode material is Na9·[Na4(H2O) 18 Co3(H2O)4(OH){SbW9O 33 }2] ·20H2O, molecular weight is 4070, molecular structure formula is W 18 Co3Sb2[μ4-O]4[μ3-O]8[μ2-O] 32 Na 13 --[H2O] 42 [O] 22 [OH] - ; The structure of the polyoxometalate electrode material is composed of two centrosymmetric {SbW9O 33 } 9- It is composed of polyoxyanions, three Co and three Na in the center and ten Na on the periphery; Among them, Sb is three-coordinated and forms a trihedral structure with the three surrounding O atoms. W is six-coordinated and connects the six surrounding O atoms to form a tetrahedral bipyramid structure. These polyhedral structures share O atoms to form two cage cluster structures containing one Sb, nine W and three Co and Na elements. The remaining three sodium ions, a total of ten, are connected to the outside of the polyacid sphere, extending their "hands" to both sides of the polyacid sphere. At the same time, Na5 in the periphery and the next Na7 are connected in a "branch" shape to form a one-dimensional chain. Two Na5 and Na7 are connected to form a ring, extending in a two-dimensional plane. Furthermore, Na5 and O23 are connected through hydrogen bond supramolecular interactions, extending in three-dimensional space to form an ABAB-arranged three-dimensional structure.

2. The method for preparing the polyoxometalate electrode material according to claim 1, characterized in that The preparation method of the polyoxometalate electrode material is carried out according to the following steps:

1. Dissolve Na2WO4 in deionized water, heat to 90°C, and stir at 90°C for 10 minutes to obtain Solution 1; wherein the mass volume ratio of Na2WO4 to deionized water is (3-4) g: (20-30) mL; 2. Add 1 mL of hydrochloric acid aqueous solution containing 0.3-0.4 g of SbCl3 dropwise to solution No. 1 and stir at 90°C for 10 minutes to obtain solution No. 2; The concentration of hydrochloric acid in the hydrochloric acid aqueous solution containing SbCl3 is 6 mol / L; 3. Add 0.1-0.2 g of CoCl2 to solution No. 2, stir thoroughly to obtain solution No. 3, add 6 mol / L hydrochloric acid to adjust the pH value to 6.2-6.5, stir at a constant temperature of 90°C for 1-2 hours, cool to room temperature, filter out the precipitate, and refrigerate the filtrate for 10-35 days to obtain the polyoxometalate material.

3. The method for preparing the polyoxometalate electrode material according to claim 2, characterized in that In step 1, the mass volume ratio of Na2WO4 to deionized water is 3.3 g: 20 mL.

4. The method for preparing the polyoxometalate electrode material according to claim 2, characterized in that In step 2, a hydrochloric acid aqueous solution containing 0.394 g of SbCl3 is added dropwise to solution No.

1.

5. The method for preparing the polyoxometalate electrode material according to claim 2, characterized in that The mass of CoCl2 in step 3 is 0.129g.

6. The use of the polyoxometalate electrode material according to claim 1, characterized in that The polyoxometalate electrode material is used as a catalytic material to produce oxygen.

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