MOF (Metal Organic Framework) material rich in coordination defects as well as preparation method and application of MOF material

Abstract

The invention discloses an MOF (Metal Organic Framework) material rich in coordination defects as well as a preparation method and application of the MOF material. The preparation method of the MOF material rich in coordination defects comprises the following steps: 1) preparing foamed nickel loaded with nickel-cobalt layered double hydroxides; and 2) dissolving 2, 6-naphthalenedicarboxylic acid and ferrocenecarboxylic acid in a mixed solvent composed of N, N-dimethylformamide and water, and then adding the foamed nickel loaded with the nickel-cobalt layered double hydroxides to carry out solvothermal reaction. The MOF material is rich in coordination defects, has the advantages of being excellent in catalytic performance, good in stability and the like when used as an electrode material for hydrogen production through water electrolysis, can effectively reduce energy consumption of hydrogen production through water electrolysis and improve the efficiency of hydrogen production through water electrolysis, and is low in production cost, wide in raw material source, simple in preparation method and suitable for industrial production. The method is suitable for large-scale industrial production and application.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by electrolysis of water, and in particular to a MOF material rich in coordination defects and a preparation method and application thereof. Background Art

[0002] Hydrogen energy is a secondary clean energy source, which has the advantages of being green and environmentally friendly, and having abundant raw material sources, and has a very broad application prospect. At present, hydrogen is mainly produced in industry by high-temperature cracking of methane (methane decomposes into carbon and hydrogen at high temperature). This method not only has high energy consumption, but also produces polluting gases such as carbon dioxide, which seriously restricts the application of hydrogen energy. Hydrogen production by water electrolysis is a method of producing hydrogen and oxygen by electrolyzing water. This method can use renewable energy to produce hydrogen (first convert renewable energy into electrical energy, and then use it to electrolyze water to produce hydrogen), and has better application prospects than high-temperature cracking of methane to produce hydrogen.

[0003] The hydrogen production from water electrolysis (OWS) reaction includes two half reactions: the cathode hydrogen evolution reaction (HER) and the anode oxygen evolution reaction (OER). The OER reaction involves a four-electron transfer process (the HER reaction only involves a two-electron transfer process), and the kinetic process is slow, which is a key factor restricting the efficiency of water electrolysis. Therefore, a catalyst is needed to promote the oxygen evolution reaction. At present, the commonly used oxygen evolution reaction catalysts are mainly precious metal (e.g., platinum, iridium, etc.) catalysts. These catalysts have high catalytic activity, but due to the scarcity and high price of precious metal resources, the cost of hydrogen production from water electrolysis remains high. MOF material is a material with a periodic network structure assembled from a metal source and an organic ligand, which has the advantages of abundant resources and low price. MOF materials will be converted into metal hydroxide oxides during the OER reaction, and metal hydroxide oxides can promote the OER reaction as the real active site of the OER reaction, so MOF materials are expected to replace precious metal catalysts. However, the catalytic activity of existing MOF materials is low and the stability is poor, which is difficult to fully meet the requirements of practical applications.

[0004] Therefore, it is of great significance to develop a MOF material with high catalytic activity and good stability. Summary of the invention

[0005] The purpose of the present invention is to provide a MOF material rich in coordination defects and a preparation method and application thereof.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a MOF material rich in coordination defects comprises the following steps:

[0008] 1) dissolving a cobalt salt, a nickel salt and a quaternary ammonium salt type cationic surfactant in a mixed solvent consisting of a low-carbon alcohol and water, and then adding nickel foam to carry out a solvothermal reaction to obtain a nickel foam loaded with a nickel-cobalt layered double metal hydroxide;

[0009] 2) 2,6-naphthalene dicarboxylic acid and ferrocene carboxylic acid are dissolved in a mixed solvent consisting of N,N-dimethylformamide and water, and then nickel foam loaded with nickel-cobalt layered double hydroxide is added for solvothermal reaction to obtain a MOF material rich in coordination defects.

[0010] Preferably, a method for preparing a MOF material rich in coordination defects comprises the following steps:

[0011] 1) dissolving a cobalt salt, a nickel salt and a quaternary ammonium salt type cationic surfactant in a mixed solvent consisting of a low-carbon alcohol and water, adding a nickel foam to carry out a solvothermal reaction, washing the product with water and anhydrous ethanol, and drying the product to obtain a nickel foam loaded with a nickel-cobalt layered double metal hydroxide;

[0012] 2) Dissolving 2,6-naphthalene dicarboxylic acid and ferrocene carboxylic acid in a mixed solvent consisting of N,N-dimethylformamide and water, adding nickel foam loaded with nickel-cobalt layered double hydroxide to carry out a solvothermal reaction, washing the product with water and anhydrous ethanol, and then drying to obtain a MOF material rich in coordination defects.

[0013] Preferably, the cobalt salt in step 1) is at least one of cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate.

[0014] Preferably, the nickel salt in step 1) is at least one of nickel nitrate, nickel sulfate, nickel chloride and nickel acetate.

[0015] Preferably, the quaternary ammonium salt cationic surfactant in step 1) is at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride and octadecyltrimethylammonium bromide.

[0016] Preferably, the low-carbon alcohol in step 1) is at least one of methanol, ethanol and propanol.

[0017] Preferably, in step 1), the volume ratio of the low-carbon alcohol to water in the mixed solvent consisting of low-carbon alcohol and water is 3 to 6:1.

[0018] Preferably, the molar ratio of the cobalt salt, nickel salt and quaternary ammonium salt type cationic surfactant in step 1) is 1:1-3:2-4.

[0019] Preferably, in step 1), the mass ratio of the cobalt salt to the nickel foam is 1:0.1-5.

[0020] Preferably, the solvent thermal reaction in step 1) is carried out at a temperature of 140° C. to 200° C., and the reaction time is 5 h to 15 h.

[0021] Preferably, in step 2), the molar ratio of 2,6-naphthalene dicarboxylic acid to ferrocene carboxylic acid is 1:0.1 to 1.0.

[0022] Preferably, in step 2), the volume ratio of N,N-dimethylformamide to water in the mixed solvent consisting of N,N-dimethylformamide and water is 1 to 2:1.

[0023] Preferably, in step 2), the mass ratio of the 2,6-naphthalene dicarboxylic acid to the nickel foam loaded with nickel-cobalt layered double hydroxide is 1:0.05-5.

[0024] Preferably, the solvent thermal reaction in step 2) is carried out at a temperature of 100° C. to 150° C., and the reaction time is 10 h to 20 h.

[0025] A MOF material rich in coordination defects is prepared by the above preparation method.

[0026] A catalyst for oxygen evolution reaction by electrolysis of water comprises the above-mentioned MOF material rich in coordination defects.

[0027] An application of the MOF material rich in coordination defects as described above in hydrogen production by water electrolysis.

[0028] The beneficial effects of the present invention are as follows: the MOF material of the present invention is rich in coordination defects, and using it as an electrode material for hydrogen production by water electrolysis has the advantages of excellent catalytic performance and good stability, etc., and can effectively reduce the energy consumption of hydrogen production by water electrolysis and improve the efficiency of hydrogen production by water electrolysis. In addition, the MOF material has low production cost, a wide source of raw materials, and a simple preparation method, and is suitable for large-scale industrial production and application.

[0029] Specifically:

[0030] 1) The MOF material of the present invention is rich in coordination defects. The incorporation of defects makes the MOF material contain a large number of unsaturated metal sites, and the unsaturated metal sites are more easily oxidized and can be converted into more metal hydroxide oxides, thereby significantly improving the OER activity of the MOF material;

[0031] 2) The MOF material of the present invention has excellent stability, can effectively resist volume expansion and structural damage, and can maintain the stability of structure and performance after long-term use;

[0032] 3) The MOF material of the present invention has low production cost, wide raw material sources, and simple preparation method, and is suitable for large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The NiCo LDH / NF in Example 1 and the NiCo NDC-Fc in Example 1 0.67 SEM images of NiCo NDC / NF and NiCo NDC / NF in Comparative Example 1.

[0034] Figure 2 NiCo NDC-Fc in Example 1 0.67 / NF EDS diagram.

[0035] Figure 3 NiCo NDC-Fc in Example 1 0.67 / Element distribution diagram of NF.

[0036] Figure 4 NiCo LDH / NF and NiCo NDC-Fc in Example 1 0.67 / NF’s XRD pattern.

[0037] Figure 5 NiCo NDC-Fc in Example 1 0.67 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 Fourier transform infrared spectrum of / NF.

[0038] Figure 6 NiCo NDC-Fc in Example 1 0.67 Electron paramagnetic resonance spectra of NiCo NDC / NF and Comparative Example 1.

[0039] Figure 7 NiCo NDC-Fc in Example 1 0.67 Nitrogen adsorption-desorption isotherms of NiCo NDC / NF and Comparative Example 1.

[0040] Figure 8 NiCo NDC-Fc in Example 1 0.67 / NF, NiCo NDC-Fc1 / NF in Example 2, NiCo NDC-Fc1 / NF in Example 3 0.43 / NF, NiCo NDC-Fc in Example 4 0.25 / NF, NiCo NDC-Fc in Example 5 0.11 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 LSV curve of / NF.

[0041] Fig. 9 NiCo NDC-Fc in Example 10.67 / NF, NiCo NDC-Fc1 / NF in Example 2, NiCo NDC-Fc1 / NF in Example 3 0.43 / NF, NiCo NDC-Fc in Example 4 0.25 / NF, NiCo NDC-Fc in Example 5 0.11 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 Overpotential diagram of / NF.

[0042] Fig.10 NiCo NDC-Fc in Example 1 0.67 / NF, NiCo NDC-Fc1 / NF in Example 2, NiCo NDC-Fc1 / NF in Example 3 0.43 / NF, NiCo NDC-Fc in Example 4 0.25 / NF, NiCo NDC-Fc in Example 5 0.11 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 Tafel slope plot of / NF.

[0043] Fig.11 NiCo NDC-Fc in Example 1 0.67 / NF, NiCo NDC-Fc1 / NF in Example 2, NiCo NDC-Fc1 / NF in Example 3 0.43 / NF, NiCo NDC-Fc in Example 4 0.25 / NF, NiCo NDC-Fc in Example 5 0.11 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 / NF double layer capacitance diagram.

[0044] Fig.12 NiCo NDC-Fc in Example 1 0.67 / NF, NiCo NDC-Fc1 / NF in Example 2, NiCo NDC-Fc1 / NF in Example 3 0.43 / NF, NiCo NDC-Fc in Example 4 0.25 / NF, NiCo NDC-Fc in Example 5 0.11 / NF, NiCo NDC / NF in Comparative Example 1, and NiCo NDC-Cc in Comparative Example 2 0.67 Electrochemical impedance spectroscopy of NF.

[0045] Fig.13 NiCo NDC-Fc in Example 1 0.67 / NF constant voltage stability test results.

[0046] Fig.14 NiCo NDC-Fc in Example 1 0.67 CV curve of / NF.

[0047] Fig.15 This is the CV curve of NiCo NDC / NF in Comparative Example 1.

[0048] Fig.16 NiCo NDC-Fc in Example 1 0.67 Comparison of metal redox peaks of NiCo NDC / NF and Comparative Example 1. DETAILED DESCRIPTION

[0049] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0050] Embodiment 1:

[0051] A MOF material rich in coordination defects, the preparation method of which is as follows:

[0052] 1) 348 mg (1.2 mmol) of Co(NO3)2·6H2O, 524 mg (1.8 mmol) of Ni(NO3)2·6H2O and 1 g (2.7 mmol) of cetyltrimethylammonium bromide (CTAB) were stirred and dissolved in a mixed solvent consisting of methanol and deionized water (mixed with 60 mL of anhydrous methanol and 12 mL of deionized water) to form a uniform solution, and then the solution was injected into a high-pressure reactor, and 0.126 g of nickel foam (large The small size is 1.5cm×3cm×1mm; the nickel foam was pretreated as follows: the nickel foam was ultrasonically cleaned with 2.0mol / L hydrochloric acid, deionized water and anhydrous ethanol for 20min respectively, then placed in a vacuum drying oven at 60°C for drying), reacted at 180°C for 6h, naturally cooled to room temperature, and then the product was taken out for multiple water washings and multiple anhydrous ethanol washings, and then placed in a vacuum drying oven at 60°C for drying overnight to obtain a nickel foam loaded with nickel-cobalt layered double hydroxide (denoted as NiCo LDH / NF);

[0053] 2) 130 mg (0.6 mmol) of 2,6-naphthalene dicarboxylic acid and 92 mg (0.4 mmol) of ferrocene carboxylic acid were stirred and dissolved in a mixed solvent consisting of N,N-dimethylformamide and deionized water (mixed with 32 mL of N,N-dimethylformamide and 16 mL of deionized water) to form a uniform solution, and then the solution was injected into a high-pressure reactor, and 0.1 g of nickel foam loaded with nickel-cobalt layered double hydroxide was added, and the reaction was carried out at 130°C for 12 h, and the reaction was naturally cooled to room temperature. The product was taken out and washed with water and anhydrous ethanol for multiple times, and then placed in a vacuum drying oven at 60°C for overnight to obtain a MOF material rich in coordination defects (denoted as NiCo NDC-Fc 0.67 / NF).

[0054] Comparative Example 1:

[0055] A MOF material (denoted as NiCo NDC / NF) is prepared in the same manner as in Example 1 except that the amount of 2,6-naphthalene dicarboxylic acid in step 2) is adjusted from "0.6 mmol" to "1 mmol" and the amount of ferrocene carboxylic acid in step 2) is adjusted from "0.4 mmol" to "0".

[0056] Comparative Example 2:

[0057] A MOF material (denoted as NiCo NDC-Cc 0.67 / NF), except that the ferrocenecarboxylic acid in step 2) is replaced by an equal molar amount of 1-cyclopentenecarboxylic acid during the preparation, the rest is exactly the same as in Example 1.

[0058] Performance Testing:

[0059] 1) The nickel foam loaded with nickel-cobalt layered double hydroxide (NiCo LDH / NF) in Example 1, the MOF material rich in coordination defects (NiCo NDC-Fc 0.67 The scanning electron microscope (SEM) images of the MOF material (NiCo NDC / NF) and the comparative example 1 are as follows Figure 1 shown.

[0060] Depend on Figure 1 It can be seen that NiCo LDH / NF presents a nanosheet morphology, which is then further converted into NiCo NDC-Fc in situ. 0.67 / NF, the nanosheet morphology is maintained.

[0061] 2) The MOF material rich in coordination defects in Example 1 (NiCo NDC-Fc 0.67 / NF) EDS diagram is as follows Figure 2 The element distribution diagram is shown in Figure 3 shown.

[0062] Depend on Figure 2 and Figure 3 It can be seen that NiCo NDC-Fc 0.67 C, O, Fe, Co and Ni exist in the NiCo NDC-Fc / NF. The incorporation of the defective ligand (ferrocenecarboxylic acid) introduces the Fe element. 0.67 / NF is a nickel foam substrate with a high Ni content (39.48wt%), while the contents of C, O, Fe and Co are 33.30wt%, 8.12wt%, 5.30wt% and 13.8wt%, respectively. After selecting the material area, a surface scan was performed. The results showed that C, O, Fe, Co and Ni elements are evenly distributed in NiCoNDC-Fc 0.67 / NF surface.

[0063] 3) The nickel foam (NiCo LDH / NF) loaded with nickel-cobalt layered double hydroxide and the MOF material rich in coordination defects (NiCo NDC-Fc 0.67 The X-ray diffraction (XRD) pattern of Figure 4 shown.

[0064] Depend on Figure 4 It can be seen that NiCo NDC-Fc 0.67 The peak positions of NiCo LDH / NF (near 7° and 14.18°) correspond to those of MOF materials synthesized with 2,6-naphthalene dicarboxylic acid as ligand, indicating that the transition from NiCo LDH / NF to NiCo NDC-Fc has been successfully achieved. 0.67 / NF conversion.

[0065] 4) MOF material rich in coordination defects in Example 1 (NiCo NDC-Fc 0.67 / NF), the MOF material in Comparative Example 1 (NiCo NDC / NF) and the MOF material in Comparative Example 2 (NiCo NDC-Cc 0.67 The Fourier transform infrared spectrum of Figure 5 shown.

[0066] Depend on Figure 5 It can be seen that when NiCo LDH / NF is converted in situ to NiCo NDC-Fc 0.67 / NF, the C=O and CO stretching vibration absorption peaks of the carboxyl group in the free ligand disappeared after the formation of MOF, indicating that the carboxyl group in the ligand was coordinated with the metal ion.

[0067] 5) The MOF material rich in coordination defects in Example 1 (NiCo NDC-Fc 0.67The electron paramagnetic resonance spectra of the MOF material (NiCo NDC / NF) and the MOF material (NiCo NDC / NF) in Comparative Example 1 are shown in FIG. Figure 6 shown.

[0068] Depend on Figure 6 It can be seen that NiCo NDC-Fc 0.67 / NF presents an obvious characteristic signal at g=2.23, which is enhanced and broadened, indicating that the incorporation of ferrocenecarboxylic acid produces a large number of unpaired electrons in the MOF material.

[0069] 6) MOF material rich in coordination defects in Example 1 (NiCo NDC-Fc 0.67 The nitrogen adsorption-desorption isotherms of the MOF material (NiCo NDC / NF) and the MOF material (NiCo NDC / NF) in Comparative Example 1 are as follows: Figure 7 shown.

[0070] Depend on Figure 7 It can be seen that NiCo NDC-Fc 0.67 The nitrogen adsorption-desorption isotherms of NiCo NDC / NF and NiCo NDC / NF are both of type I+IV, indicating the presence of micropores and mesopores in the materials. 0.67 The adsorption amount of / NF increased and the surface area increased.

[0071] Embodiment 2:

[0072] A MOF material rich in coordination defects (denoted as NiCo NDC-Fc1 / NF), except that the amount of 2,6-naphthalene dicarboxylic acid in step 2) is adjusted from "0.6mmol" to "0.5mmol" and the amount of ferrocenecarboxylic acid in step 2) is adjusted from "0.4mmol" to "0.5mmol" during preparation, the rest is exactly the same as Example 1.

[0073] Embodiment 3:

[0074] A MOF material rich in coordination defects (denoted as NiCo NDC-Fc 0.43 / NF), except that the amount of 2,6-naphthalene dicarboxylic acid in step 2) is adjusted from "0.6mmol" to "0.7mmol" and the amount of ferrocene carboxylic acid in step 2) is adjusted from "0.4mmol" to "0.3mmol", the rest is exactly the same as Example 1.

[0075] Embodiment 4:

[0076] A MOF material rich in coordination defects (denoted as NiCo NDC-Fc 0.25 / NF), except that the amount of 2,6-naphthalene dicarboxylic acid in step 2) is adjusted from "0.6mmol" to "0.8mmol" and the amount of ferrocene carboxylic acid in step 2) is adjusted from "0.4mmol" to "0.2mmol", the rest is exactly the same as Example 1.

[0077] Embodiment 5:

[0078] A MOF material rich in coordination defects (denoted as NiCo NDC-Fc 0.11 / NF), except that the amount of 2,6-naphthalene dicarboxylic acid in step 2) is adjusted from "0.6mmol" to "0.9mmol" and the amount of ferrocene carboxylic acid in step 2) is adjusted from "0.4mmol" to "0.1mmol", the rest is exactly the same as Example 1.

[0079] Electrochemical performance test:

[0080] 1) The MOF material rich in coordination defects (NiCo NDC-Fc 0.67 / NF, NiCo NDC-Fc1 / NF, NiCo NDC-Fc 0.43 / NF、NiCo NDC-Fc 0.25 / NF and NiCo NDC-Fc 0.11 / NF, collectively referred to as NiCo NDC-Fc x / NF), the MOF material in Comparative Example 1 (NiCo NDC / NF) and the MOF material in Comparative Example 2 (NiCo NDC-Cc 0.67 / NF) as the working electrode, carbon rod as the counter electrode, Hg / HgO electrode as the reference electrode, and 1.0 mol / L KOH aqueous solution as the electrolyte to assemble a three-electrode system, and then perform electrochemical tests. The obtained LSV curve is as follows Figure 8 As shown, the overpotential diagram is Fig. 9 As shown, the Tafel slope diagram is as follows Fig.10 As shown, the double layer capacitance diagram is as follows Fig.11 The electrochemical impedance spectroscopy diagram is shown in Fig.12 shown.

[0081] Depend on Figure 8 and Fig. 9 It can be seen that NiCo NDC-Fc 0.67 The onset potential of / NF is 1.32 V, and it has the lowest overpotential at any current density after the OER reaction occurs; 10 mA cm -2 When NiCo NDC-Fc 0.67 The overpotential of / NF is 220mV, even at 100mA·cm-2 At high current density, NiCo NDC-Fc 0.67 The overpotential of NiCo NDC-Fc x / NF had significantly higher catalytic activity than NiCo NDC / NF; NiCo NDC-Cc 0.67 / NF introduced the defective ligand 1-cyclopentenecarboxylic acid (Cc), which does not contain Fe element compared with the ferrocene ligand. Therefore, by comparing the performance of MOF materials without Fe defects and MOF materials without defects, the overpotential of MOF materials without Fe defects is smaller, indicating that the introduction of defects can effectively improve the activity of MOF materials, and the oxygen evolution performance of the material is better after the introduction of Fe-defective ligands.

[0082] Depend on Fig.10 It can be seen that NiCo NDC-Fc 0.67 The slope of the Tafel curve of / NF is 37mV·dec -1 , which is much smaller than other materials, indicating that NiCo NDC-Fc 0.67 / NF has faster kinetics and the best catalytic activity for oxygen evolution reaction (the smaller the Tafel slope, the smaller the change of overpotential with the increase of current density, and the better the electrocatalytic performance).

[0083] Depend on Fig.11 It can be seen that NiCo NDC-Fc 0.67 / NF has the largest active specific surface area and exposes more active sites, that is, the number of active sites that can participate in the oxygen evolution reaction increases, which is more conducive to promoting the occurrence of reconstruction in the material and improving the oxygen evolution performance.

[0084] Depend on Fig.12 It can be seen that NiCo NDC-Fc 0.67 / NF has the smallest diameter semicircle, so its charge transfer resistance is the smallest. Compared with other materials, it has the strongest charge transfer ability and better oxygen evolution reaction activity (electrochemical impedance spectroscopy is to use a small amplitude AC signal to perturb the electrode and observe the system's follow-up of the perturbation in a steady state. The general impedance spectrum is a semicircle at high frequencies, and the diameter of the semicircle represents the charge transfer resistance R at the interface between the electrode and the solution. ct , the smaller the diameter, R ct The smaller it is, the stronger the charge transfer capacity is and the better the catalytic performance of the catalyst is).

[0085] 2) The MOF material (NiCo NDC-Fc 0.67 / NF) as the working electrode, carbon rod as the counter electrode, Hg / HgO electrode as the reference electrode, and 1.0 mol / L KOH aqueous solution as the electrolyte to assemble a three-electrode system, and then use the chronoamperometry method to perform stability test. The constant voltage stability test results are shown in the figure below. Fig.13 shown.

[0086] Depend on Fig.13 It can be seen that NiCo NDC-Fc 0.67 / NF at current density 60mA·cm -2 After 100h of long-term testing at the corresponding voltage, the current density hardly changed, indicating that NiCo NDC-Fc 0.67 / NF has excellent stability and is suitable for industrial applications.

[0087] 3) The MOF material (NiCo NDC-Fc 0.67 / NF) and the MOF material (NiCo NDC / NF) in Comparative Example 1 were used as working electrodes, carbon rods as counter electrodes, Hg / HgO electrodes as reference electrodes, and 1.0 mol / L KOH aqueous solution as electrolyte to assemble a three-electrode system, and then electrochemical cyclic voltammetry was performed to obtain NiCo NDC-Fc 0.67 The CV curve of / NF is as follows Fig.14 As shown in Figure 2, the CV curve of NiCo NDC / NF is as follows: Fig.15 As shown, NiCo NDC-Fc 0.67 Comparison of metal redox peaks of NiCo NDC / NF and NiCo NDC / NF Fig.16 shown.

[0088] Depend on Figures 14 to 16 It can be seen that by increasing the number of scans of the material CV curve, it is found that NiCo NDC-Fc 0.67 / NF redox peak area increased significantly, indicating that more metal sites in the material were oxidized and the defective NiCo NDC-Fc 0.67 / NF redox peak area is significantly larger than that of NiCo NDC / NF, indicating that NiCo NDC-Fc 0.67 / NF contains more unsaturated metal sites, and further by comparing the CV graphs before and after defect doping, it can be seen that the oxidation peak of the metal from 2-valent to 3-valent has shifted negatively after defect doping, indicating that NiCo NDC-Fc 0.67 The unsaturated metal sites in / NF are more susceptible to oxidation.

[0089] In summary, the present invention converts NiCo LDH / NF into NiCo NDC-Fc x / NF, and the NiCo NDC-Fc was tuned by adjusting the ratio of the main ligand (2,6-naphthalene dicarboxylic acid) to the defective ligand (ferrocene carboxylic acid). x / NF defect content and performance, and finally obtained a catalyst for oxygen evolution reaction in water electrolysis with excellent catalytic performance and good stability.

[0090] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a MOF material rich in coordination defects, characterized in that: The following steps are involved: 1) dissolving a cobalt salt, a nickel salt and a quaternary ammonium salt type cationic surfactant in a mixed solvent consisting of a low-carbon alcohol and water, and then adding nickel foam to carry out a solvothermal reaction to obtain a nickel foam loaded with a nickel-cobalt layered double metal hydroxide; 2) 2,6-naphthalene dicarboxylic acid and ferrocene carboxylic acid are dissolved in a mixed solvent consisting of N,N-dimethylformamide and water, and then nickel foam loaded with nickel-cobalt layered double hydroxide is added for solvothermal reaction to obtain a MOF material rich in coordination defects.

2. The preparation method according to claim 1, characterized in that: The cobalt salt in step 1) is at least one of cobalt nitrate, cobalt sulfate, cobalt chloride and cobalt acetate; the nickel salt in step 1) is at least one of nickel nitrate, nickel sulfate, nickel chloride and nickel acetate; the quaternary ammonium salt cationic surfactant in step 1) is at least one of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride and octadecyltrimethylammonium bromide; the low-carbon alcohol in step 1) is at least one of methanol, ethanol and propanol.

3. The preparation method according to claim 1 or 2, characterized in that: Step 1) The molar ratio of the cobalt salt, the nickel salt and the quaternary ammonium salt type cationic surfactant is 1:1-3:2-4.

4. The preparation method according to claim 1 or 2, characterized in that: Step 1) The solvent thermal reaction is carried out at a temperature of 140° C. to 200° C., and the reaction time is 5 h to 15 h.

5. The preparation method according to claim 1, characterized in that: In step 2), the molar ratio of 2,6-naphthalene dicarboxylic acid to ferrocene carboxylic acid is 1:0.1-1.

6. The preparation method according to claim 1 or 5, characterized in that: Step 2) The solvent thermal reaction is carried out at a temperature of 100° C. to 150° C. and the reaction time is 10 h to 20 h.

7. The preparation method according to any one of claims 1, 2 and 5, characterized in that: The mass ratio of the cobalt salt and the nickel foam in step 1) is 1:0.1-5; the volume ratio of the low-carbon alcohol and water in the mixed solvent composed of low-carbon alcohol and water in step 1) is 3-6:1; the mass ratio of the 2,6-naphthalene dicarboxylic acid and the nickel foam loaded with nickel-cobalt layered double metal hydroxide in step 2) is 1:0.05-5; the volume ratio of N,N-dimethylformamide and water in the mixed solvent composed of N,N-dimethylformamide and water in step 2) is 1-2:

1.

8. A MOF material rich in coordination defects, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. A catalyst for oxygen evolution reaction by electrolysis of water, characterized in that: The MOF material comprising the coordination defect-rich material according to claim 8.

10. Use of the MOF material rich in coordination defects as claimed in claim 8 in hydrogen production by water electrolysis.

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