Preparation of nickel-iron coordination covalent organic framework material and application of nickel-iron coordination covalent organic framework material in water electrolysis
By constructing the nickel-iron coordinated covalent organic framework material TD-COF-Fe/Ni-x, the problems of poor electronic conductivity and limited stability of FeOOH were solved, efficient electrocatalytic oxygen evolution reaction was achieved, and the efficiency and stability of water electrolysis were improved.
Patent Information
- Application Number
- CN202510946438.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-09
- Publication Date
- 2025-10-10
AI Technical Summary
Existing OER catalysts such as FeOOH have poor electronic conductivity and limited structural stability, resulting in insufficient catalytic performance and durability, which limits the improvement of water electrolysis efficiency.
By constructing a nickel-iron coordinated covalent organic framework material TD-COF-Fe/Ni-x, combining the composite structure of TD-COF and FeOOH, Ni doping is used to improve the electronic structure and active site exposure of FeOOH, forming a porous structure to promote electrolyte transport and bubble desorption.
The reaction energy barrier is significantly reduced, the OER performance of the electrocatalyst is improved, and the efficiency and stability of water electrolysis are enhanced.
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Figure CN120757730A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of material technology, and specifically relates to the preparation and water electrolysis application of a nickel-iron coordinated covalent organic framework material TD-COF-Fe / Ni-x. Background Art
[0002] Water electrolysis is a highly promising technology that can convert electricity generated by renewable energy sources (such as solar and wind energy) into chemical energy and store it in the form of hydrogen, achieving clean energy conversion and storage. The oxygen evolution reaction (OER), the anodic reaction in water electrolysis, involves a four-electron transfer process and has sluggish kinetics, making it a key bottleneck restricting overall electrolysis efficiency. Therefore, the development of high-performance OER electrocatalysts is crucial to reducing energy consumption and improving water electrolysis efficiency.
[0003] Currently, precious metal-based materials (such as IrO2 and RuO2) are considered the most effective OER catalysts, but their high cost and scarcity limit their large-scale application. In recent years, transition metal-based catalysts (such as oxides, hydroxides, and sulfides of iron, cobalt, and nickel) have attracted widespread attention due to their low cost, abundant resources, and good catalytic activity. Among them, iron-based oxyhydroxide (FeOOH), as a typical OER catalyst, has a unique layered structure and abundant active sites, which can effectively promote the OER reaction. However, pure FeOOH materials have problems such as poor electronic conductivity and limited structural stability, resulting in the catalytic performance and durability still needing to be improved. Summary of the Invention
[0004] The present invention provides a preparation and water electrolysis application of a nickel-iron coordinated covalent organic framework material TD-COF-Fe / Ni-x. By constructing a composite structure of TD-COF and FeOOH (Ni is doped into the FeOOH lattice), the problems of insufficient exposure of active sites, poor electronic conductivity, and limited stability of existing OER catalysts are solved, thereby achieving a highly efficient electrocatalytic oxygen evolution reaction.
[0005] The technical solution of the present invention is to provide a method for preparing a nickel-iron coordinated covalent organic framework material TD-COF-Fe / Ni-x, comprising the following steps: S1. Synthesis of TD-COF framework: 3,3'-dihydroxybenzidine and 1,3,5-triformylphloroglucinol were added to an aqueous acetic acid solution in a solvent system. The mixture was subjected to a freeze-evacuation-thaw cycle and then sealed. The mixture was reacted at 100-120°C for 2-4 days, filtered, washed, and dried to obtain TD-COF. S2. Preparation of TD-COF-Fe / Ni-x: Dissolve TD-COF, iron salt and nickel salt in a mixed solution of methanol and acetic acid, mix and react at 40-80°C for 2-12 h, and filter and dry to obtain TD-COF-Fe / Ni-x.
[0006] Optionally, the solvent in S1 is a mixed system of 1,4-dioxane and mesitylene in a volume ratio of 1:0.75~1.25.
[0007] Optionally, the molar ratio of 3,3'-dihydroxybenzidine to 1,3,5-triformylphloroglucinol is 1-2:1.
[0008] Optionally, the iron salt and nickel salt in S2 are acetates, nitrates or sulfates thereof.
[0009] Optionally, the mass ratio of TD-COF to iron salt and nickel salt is 1:(0.13~0.520):(0.13~0.525) Optionally, in the mixed solution of methanol and acetic acid, the volume ratio of the two is 45:0.75~1.25.
[0010] The present invention also relates to TD-COF-Fe / Ni-x obtained by the preparation method, wherein the molar ratio x of the NO2 tridentate ligand in TD-COF is 0.25 to 1.00, preferably 0.75.
[0011] The present invention also relates to a method for preparing a TD-COF / Ni-doped FeOOH composite, which comprises using TD-COF-Fe / Ni-x as a precursor and dispersing it in a KOH solution to form a TD-COF / Ni-doped FeOOH composite, or using TD-COF-Fe / Ni-x to directly catalyze an oxygen evolution reaction in an alkaline environment to convert the material into a TD-COF / Ni-doped FeOOH composite in situ.
[0012] The present invention also relates to the use of a TD-COF / Ni-doped FeOOH composite as a catalyst for oxygen evolution reaction in water electrolysis. The TD-COF / Ni-doped FeOOH composite is mixed with carbon black and carbon nanotubes in a mass ratio of 2:0.5-1.5:1.5-0.5, ground, and then dispersed in a mixed solution of ethanol, water, and Nafion solution to prepare a slurry that is coated on the surface of a conductive substrate for use as an electrode.
[0013] Optionally, the ratio of the TD-COF / Ni-doped FeOOH composite to the electrode area is 0.8~2.0 mg:1 cm²; and the conductive substrate is carbon cloth, nickel foam, or glassy carbon electrode.
[0014] The present invention has the following beneficial effects: The TD-COF material prepared by the present invention uses 3,3'-dihydroxybenzidine and 1,3,5-triformylphloroglucinol as raw materials to synthesize the TD-COF framework, which has a layered porous structure and can be used as a carrier to load metal oxide or hydroxide nanoparticles, promote material transport and exposure of active sites, and improve the dispersibility and stability of the active material; the specific loaded metals are Fe²⁺ and Ni²⁺, which coordinate with the CN and C=O bonds in the TD-COF framework to form a chelate. At the same time, under alkaline conditions, the TD-COF framework is stably combined with FeOOH through hydrogen bonds and coordination, and Ni doping regulates the electronic structure of FeOOH. At the same time, the porous structure of COF promotes electrolyte transport and bubble desorption, achieves efficient catalysis, significantly reduces the reaction energy barrier, and thus improves the OER performance of the electrocatalyst. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 Schematic diagram of the synthesis of TD-COF framework.
[0016] Figure 2 Schematic diagram of the TD-COF coordinated metal structure.
[0017] Figure 3 (a) XRD patterns of TD-COF and TD-COF-Fe / Ni-x (x = 0.50, 0.75, 1.00) at 2°~40°, (b) XRD patterns of TD-COF-Fe / Ni-0.75 and TD-COF-Fe / Ni-0.75 (alkaline treatment) at 10°~80°.
[0018] Figure 4 (a), (b) TD-COF; (c), (d) SEM images of TD-COF-Fe / Ni-0.75 at different magnifications.
[0019] Figure 5 EDS-mapping image of TD-COF-Fe / Ni-0.75.
[0020] Figure 6 (a) Fourier transform infrared images of TD-COF, TD-COF-Fe / Ni-0.75, DHBD, and TP, (b) Locally enlarged Fourier transform infrared images of TD-COF and TD-COF-Fe / Ni-0.75.
[0021] Figure 7(a) LSV plots of carbon cloth-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), TD-COF, TD-COF-Fe-1.50, and blank carbon cloth, (b) Tafel plots of carbon cloth-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), and TD-COF.
[0022] Figure 8 (a) LSV plots of glassy carbon-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), TD-COF, and blank glassy carbon, (b) Tafel plots of glassy carbon-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), and TD-COF, (c) LSV plots of nickel foam-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), TD-COF, and blank nickel foam, (d) Tafel plots of nickel foam-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00), and TD-COF.
[0023] Figure 9 (a) LSV plot of TD-COF-Fe / Ni-0.75 (nitrate) and TD-COF-Fe / Ni-0.75 (sulfate), (b) Tafel plot of TD-COF-Fe / Ni-0.75 (nitrate) and TD-COF-Fe / Ni-0.75 (sulfate).
[0024] Figure 10 (a) CV graph of carbon cloth-based TD-COF, (b) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.25, (c) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.50, (d) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.75, (e) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.50, (f) Double layer capacitance of TD-COF and TD-COF-Fe / Ni-x.
[0025] Figure 11 LSV / ECSA of carbon cloth-based TD-COF-Fe / Ni-x (x=0.25, 0.50, 0.75, 1.00) and TD-COF.
[0026] Figure 12 Stability test of TD-COF-Fe / Ni-0.75.
[0027] Figure 13 This is the XRD pattern of the material before and after alkali treatment in Comparative Example 2. DETAILED DESCRIPTION
[0028] The experimental methods in the following examples are conventional methods unless otherwise specified. The materials used in the following examples are commercially available products unless otherwise specified.
[0029] The present invention uses 3,3'-dihydroxybenzidine and 1,3,5-triformylphloroglucinol to synthesize TD-COF containing CN bond and C=O bond, specifically Figure 1 As shown. When the obtained TD-COF is subjected to metal chelation, the nickel and iron ions are connected and fixed by CN and C=O to form Figure 2 TD-COF-Fe / Ni-x with tridentate coordination is shown.
[0030] Example 1 (TD-COF-Fe / Ni-0.25) Synthesis of TD-COF: 97 mg of 3,3'-dihydroxybenzidine (DHBD, 0.45 mmol) and 63 mg of 1,3,5-triformylphloroglucinol (TP, 0.3 mmol) were dispersed in 3 mL of 1,4-dioxane and 3 mL of mesitylene. The mixture was sonicated for 30 min and transferred to a 10 mL Pyrex tube. Finally, 0.6 mL of 6 mol / L aqueous acetic acid was added to the mixture. After sonication for 10 min, the Pyrex tube was subjected to three freeze-pump-thaw cycles and then flame-sealed. After cooling to room temperature, the sealed tube was placed in a 120°C oven for 3 days. The liquid in the Pyrex tube was filtered to obtain a solid cake. The cake was washed three times with N,N'-dimethylformamide (DMF) and acetone. The washed sample was filtered, and the filter cake was dried in a vacuum oven at 60°C for 12 h. The dried filter cake was collected and stored.
[0031] Preparation of TD-COF-Fe / Ni-0.25: Measure 9 mL of methanol and 200 μL of acetic acid into a flask to prepare a solution. Weigh 20 mg of TD-COF, 2.6 mg of iron acetate tetrahydrate, and 2.6 mg of nickel acetate tetrahydrate and add them to the above solution. Place the flask containing the mixture in a magnetic stirrer and stir in a 60°C water bath for 10 h. After cooling to room temperature, add 6 mL of anhydrous ethanol and stir for 5 minutes, then filter. Place the collected solid in a vacuum drying oven and dry it under vacuum at 60°C for 10 h.
[0032] Preparation of carbon cloth-based electrode: Weigh 3 mg of TD-COF-Fe / Ni-0.25 powder, 1.5 mg of carbon black, and 1.5 mg of carbon nanotubes, add them to a mortar, grind them thoroughly, add them to a mixed solvent of 780 μL of ethanol and 200 μL of water, and add 20 μL of Nafion solution. Ultrasonicate for 1 hour to obtain a black uniformly dispersed slurry. Take 200 μL of the above slurry and drop it on the surface of the carbon cloth. The carbon cloth area is 1 cm 2 , heated on a hot plate and dried, and the loading capacity was about 1.0 mg cm -2 Electrode Preparation of nickel foam-based electrode: The slurry preparation method is the same as above, and the slurry is drop-coated on the nickel foam substrate with a loading of about 2.0 mg cm -2 .
[0033] Preparation of glassy carbon-based electrodes: The slurry preparation method is the same as above, and the slurry is drop-coated on the surface of the glassy carbon electrode with a loading of about 0.8 mg cm -2 .
[0034] Example 2 (TD-COF-Fe / Ni-0.50) 20 mg of TD-COF, 5.2 mg of ferric acetate tetrahydrate and 5.2 mg of nickel acetate tetrahydrate were used as raw materials and the synthesis method was the same as TD-COF-Fe / Ni-0.25.
[0035] Example 3 (TD-COF-Fe / Ni-0.75) 20 mg of TD-COF, 7.8 mg of ferric acetate tetrahydrate, and 7.8 mg of nickel acetate tetrahydrate were used as raw materials and the synthesis method was the same as TD-COF-Fe / Ni-0.25.
[0036] Example 4 (TD-COF-Fe / Ni-1.00) 20 mg of TD-COF, 10.4 mg of ferric acetate tetrahydrate, and 10.5 mg of nickel acetate tetrahydrate were used as raw materials and the synthesis method was the same as that of TD-COF-Fe / Ni-0.25.
[0037] Example 5 (TD-COF-Fe / Ni-0.75 (nitrate)) 20 mg of TD-COF, 12.7 mg of ferric nitrate nonahydrate and 6.1 mg of ferric nitrate hexahydrate were used as raw materials and the synthesis method was the same as TD-COF-Fe / Ni-0.75.
[0038] Example 6 (TD-COF-Fe / Ni-0.75 (sulfate)) 20 mg of TD-COF, 8.8 mg of ferrous sulfate heptahydrate and 8.3 mg of nickel sulfate hexahydrate were used as raw materials and the synthesis method was the same as TD-COF-Fe / Ni-0.75.
[0039] Comparative Example 1 (TD-COF-Fe-1.50) 20 mg of TD-COF and 15.6 mg of ferric acetate tetrahydrate were used as raw materials, and the synthesis method was the same as that in Example 3.
[0040] XRD characterization was performed on TD-COF in Example 1 and TD-COF-Fe / Ni-x (x=0.50, 0.75, 1.00) in Examples 2 to 4. Figure 3 , where TD-COF exhibits a characteristic peak at 3.3° (attributed to the (100) crystal plane), and the characteristic peaks appearing between 25° and 26.8° are caused by the π-π stacking between layers, corresponding to the (001) plane. However, the peak intensity is low, and the crystallinity of the synthesized material is low. After subsequent metal chelation treatment, it was found that the characteristic peak (100) crystal plane of TD-COF-Fe / Ni-x shifted slightly to the right, indicating that the interplanar spacing of TD-COF after metal chelation was reduced. This is because when metal ions are introduced and combined with the coordination sites in TD-COF, stronger coordination bonds are formed, resulting in adjacent layers or structural units being pulled closer and the interplanar spacing being reduced. In addition, the crystallinity of TD-COF-Fe / Ni-x increased slightly, and the prominent peaks appearing at 11.2° and 12.5° were attributed to the (210) and (300) crystal planes. This indicates that during the metal chelation process, the metal coordination of iron and nickel promoted the secondary growth of the TD-COF material, achieving the effect of secondary crystallization, thereby promoting an increase in crystallinity.
[0041] In order to verify the existence form of the coordinated metal when tested in 1 M KOH solution, 40 mg of TD-COF-Fe / Ni-0.75 was dispersed in 135 mL of 1 M KOH solution and stirred for 6 h before phase analysis. XRD characterization is shown in Figure 2. Figure 3 As shown in (b), the treated TD-COF-Fe / Ni-0.75 exhibits characteristic peaks of FeO(OH) (PDF#97-015-9970), while the untreated TD-COF-Fe / Ni-0.75 lacks obvious peaks characteristic of superoxide phases. Therefore, when TD-COF-Fe / Ni-x is tested in an alkaline environment, the coordinated metal ions transform into superoxides, which lowers the reaction energy barrier and promotes the OER reaction process.
[0042] The TD-COF in Example 1 and the TD-COF-Fe / Ni-0.75 in Example 3 were characterized by SEM. Figure 4TD-COF-Fe / Ni-0.75 under different magnifications. It can be seen that the TD-COF framework network layer accumulation structure is not damaged before and after the metal chelation. TD-COF-Fe / Ni-x can still expose more active sites, and such a structure can effectively improve the OER catalytic performance. Figure 5 As shown in the figure, after metal chelation, the Fe and Ni elements are uniformly distributed in TD-COF-Fe / Ni-0.75, and the element content of TD-COF-Fe / Ni-0.75 is shown in Table 1.
[0043] Table 1
[0044] According to the specific data in Table 1, the Fe / Ni ratio in TD-COF-Fe / Ni-0.75 is 4:1.
[0045] The Fourier infrared spectra of TD-COF in Example 1, TD-COF-Fe / Ni-0.75 in Example 3, and DHBD and TP are shown in Figure 6 (a), and the Fourier infrared local magnification of TD-COF and TD-COF-Fe / Ni-0.75 is shown in Figure 6 (b). Figure 6 In (a), 3357.5 cm -1 , 3284.8 cm -1 belong to -NH2 of 3,3'-dihydroxybenzidine, and 2910 cm -1 belong to -CHO of 1,3,5-triformylphloroglucinol, which disappear in the Fourier infrared spectrum of the synthesized TD-COF. At the same time, C=O appears at 1621.7 cm -1 , C=C appears at 1581.7 cm -1 , C-N appears at 1299.4 cm -1 , which indicates that the designed TD-COF material is successfully synthesized, which is mutually corroborated with the detection results of XRD. Analyzing Figure 6 (b), Fe-O appears at 417.9 cm -1 , and Figure 6 In (a), the C=C and C=O corresponding peak values of TD-COF-Fe / Ni-0.75 compared with TD-COF obviously shift, which is due to the coordination of N and O on TD-COF with metal ions. It indicates that the metal ions are successfully coordinated to the TD-COF framework.
[0046] TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) and TD-COF were coated on carbon cloth to form electrodes, and then LSV tests were carried out in an alkaline environment of 1.0 M KOH. The LSV graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) in Examples 1-4, TD-COF in Example 1, TD-COF-Fe-1.50 in Comparative Example 1, and a blank carbon cloth control on a carbon cloth substrate are shown in Figure 7 The Tafel graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) in Examples 1-4, and TD-COF in Example 1 are shown in Figure 7 (b) and Table 2.
[0047] Table 2
[0048] It was found from this that TD-COF-Fe / Ni-0.75 was significantly superior to the OER performance of the samples prepared in other examples, with an overpotential of 311 mV at 10 mA cm -2 and a Tafel slope of 51 mV dec -1 The performance of the complex prepared by simply introducing iron salt, that is, TD-COF-Fe-1.50, was much lower than that of TD-COF-Fe / Ni-0.75 prepared by introducing a nickel-iron composite salt.
[0049] The OER-LSV performance of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) and TD-COF loaded on electrodes of nickel foam and glassy carbon substrates is shown in Figure 8 , (a) LSV graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00), TD-COF, and a blank glassy carbon on a glassy carbon substrate, (b) Tafel graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) and TD-COF, (c) LSV graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00), TD-COF, and a blank nickel foam on a nickel foam substrate, and (d) Tafel graphs of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) and TD-COF. The OER-LSV performance of TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00) and TD-COF on a nickel foam substrate was 10 mA cm -2The overpotential and Tafel of glassy carbon-based TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00), TD-COF 10 mA cm -2 The overpotential and Tafel are shown in Table 4.
[0050] Table 3
[0051] Table 4
[0052] Nickel foam-based TD-COF-Fe / Ni-0.75, at 10 mA cm -2 The overpotential is only 275 mV and the Tafel slope is only 55 mV dec. -1 .
[0053] If ferric nitrate or nickel nitrate (or ferric sulfate or nickel sulfate) is used as the iron and nickel sources, TD-COF-Fe / Ni-0.75 (nitrate) (or TD-COF-Fe / Ni-0.75 (sulfate)) is prepared and coated on a carbon cloth substrate, the OER performance is tested. Figure 9 And Table 5.
[0054] Table 5
[0055] The experimental results show that the OER performance of Examples 5 and 6 cannot be compared with that of Example 3. This may be because the coordination ability of the acetate ion in acetate is stronger than that of nitrate and sulfate, and it can promote the transformation of superoxide catalytic active sites under alkaline conditions.
[0056] Figure 10 The figures are as follows: (a) CV graph of carbon cloth-based TD-COF, (b) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.25, (c) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.50, (d) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.75, (e) CV graph of carbon cloth-based TD-COF-Fe / Ni-0.50, (f) double-layer capacitance of TD-COF and TD-COF-Fe / Ni-x. C of carbon cloth-based TD-COF-Fe / Ni-x (x = 0.25, 0.50, 0.75, 1.00), TD-COF dlThe ECSA is shown in Table 6. It can be seen that after metal chelation, the parallel plate capacitance decreases, likely due to the clogging of certain TD-COF pores during the chelation process by the transition metals iron and nickel. Compared to Examples 1 to 4, the capacitance drop for TD-COF-Fe / Ni-0.75 (Example 3) is less pronounced, only decreasing by 9% compared to the capacitance of TD-COF alone.
[0057] Table 6
[0058] In order to measure the catalytic performance difference per unit electrochemical active area, the ratio of LSV / ECSA was used for normalization. Figure 11 As shown in the comparison of unit electrochemical active area, as the content of iron and nickel increases, the catalytic performance per unit electrochemical active area becomes stronger, indicating that the chelated iron and nickel and the subsequent in-situ conversion generated Ni-FeOOH are the main active centers.
[0059] TD-COF-Fe / Ni-0.75 (Example 3) was subjected to a 10 mA cm -2 Stability test under current density. Figure 12 As shown in the figure, the overpotential of TD-COF-Fe / Ni-0.75 only fluctuates between 310-320 mV, and is maintained at 3% overall, and there is no obvious decline after running for 22 h.
[0060] Comparative Example 2 (Composite Material of Covalent Triazine Framework (CTF) Chelated Bimetallic Salt CTF-Fe / Ni-0.41) a) Mix 2,2'-bipyridine-5,5'-dimethanol, 1,1'-biphenyl-4,4'-bis(carboximide) dihydrochloride, and cesium carbonate (molar ratio of approximately 1:2:2.3) and add dimethyl sulfoxide. The mixture is reacted at 100°C for 24 hours, and CTF is obtained by filtration, washing, and drying.
[0061] b) Weigh 30 mg of CTF, 6.2 mg of Ni(CH3COO)24H2O, and 6.2 mg of Fe(CH3COO)24H2O (at this point, the bidentate pyridinic N in CTF is chelated with the metal salt in a 1:1 ratio); grind and add 15 mL of methanol and 200 μL of acetic acid; heat the mixture to 60°C for 12 h, then wash and dry to obtain CTF-Fe / Ni-0.41 chelated metal. The reaction process is shown below.
[0062]
[0063] c) The CTF chelated metal obtained in step b) is subjected to alkali treatment, specifically, it is dissolved in 1 M KOH and stirred at room temperature for 6 hours to obtain a sample, and then washed with deionized water and anhydrous ethanol to pH = 7, and then centrifuged to obtain a sample and dried.
[0064] XRD tests were performed on the CTF chelated metal obtained in step b) and the alkali-treated CTF chelated metal (KOH treated) obtained in step b) respectively. Figure 13 .
[0065] Compared to the CTF framework for chelating Ni / Fe salts, even after KOH treatment, the chelated Ni / Fe single atoms are difficult to convert into transition metal superoxides. The TD-COF framework used in the present invention, with its unique "tridentate O2N1" chelation sites, can effectively promote the conversion of chelated Ni / Fe single atoms into transition metal superoxides through the coordination of oxygen elements. In addition, in terms of salt selection, the composite prepared using acetate in the present invention exhibits excellent performance, while the performance of the composite is significantly reduced after replacing the Ni / Fe salt with sulfate and nitrate. In-depth exploration of the reasons for this is that the coordination ability of the oxygen atoms in the acetate group is significantly stronger than that of the sulfate and nitrate groups. This strong coordination property helps the single atomic iron originally in the chelated state to form a superoxide iron structure with iron oxygen octahedrons and iron oxygen tetrahedrons, thereby promoting the formation of nickel-doped superoxide iron, the OER electrocatalytic active component in the composite.
[0066] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent of the present invention shall be based on the appended claims.
Claims
1. A method for preparing a nickel-iron coordinated covalent organic framework material TD-COF-Fe / Ni-x, characterized in that: The following steps are involved: S1. Synthesis of TD-COF framework: 3,3'-dihydroxybenzidine and 1,3,5-triformylphloroglucinol were added to an aqueous acetic acid solution in a solvent system. The mixture was subjected to a freeze-evacuation-thaw cycle and then sealed. The mixture was reacted at 100-120°C for 2-4 days. The mixture was filtered, washed, and dried to obtain TD-COF. S2. Preparation of TD-COF-Fe / Ni-x: Dissolve TD-COF, iron salt and nickel salt in a mixed solution of methanol and acetic acid, mix and react at 40-80°C for 2-12 h, and filter and dry to obtain TD-COF-Fe / Ni-x.
2. The preparation method according to claim 1, wherein: The solvent in S1 is a mixed system of 1,4-dioxane and mesitylene with a volume ratio of 1:0.75~1.
25.
3. The preparation method according to claim 1, wherein: The molar ratio of 3,3'-dihydroxybenzidine to 1,3,5-triformylphloroglucinol is 1-2:
1.
4. The preparation method according to claim 1, wherein: The iron salt and nickel salt in S2 are acetates, nitrates or sulfates.
5. The preparation method according to claim 1, wherein: The mass ratio of TD-COF to iron salt and nickel salt is 1:(0.13~0.520):(0.13~0.525).
6. The preparation method according to claim 1, wherein: In the mixed solution of methanol and acetic acid, the volume ratio of the two is 45:0.75~1.
25.
7. The TD-COF-Fe / Ni-x obtained by the preparation method according to any one of claims 1 to 6, wherein the molar ratio x of the NO2 tridentate ligand in TD-COF is 0.25 to 1.
00.
8. A method for preparing a TD-COF / Ni-doped FeOOH composite, characterized by: The TD-COF-Fe / Ni-x obtained by the preparation method according to any one of claims 1 to 6 is used as a precursor and dispersed in a KOH solution to form a TD-COF / Ni-doped FeOOH composite; or the TD-COF-Fe / Ni-x obtained by the preparation method according to any one of claims 1 to 6 is directly subjected to catalytic oxygen evolution reaction in an alkaline environment to convert the material into a TD-COF / Ni-doped FeOOH composite in situ.
9. Use of the TD-COF / Ni-doped FeOOH composite obtained by the preparation method of claim 8 as a catalyst for oxygen evolution reaction by electrolysis of water, characterized in that: The TD-COF / Ni-doped FeOOH composite is mixed with carbon black and carbon nanotubes in a mass ratio of 2:0.5-1.5:1.5-0.5, ground, and dispersed in a mixed solution of ethanol, water, and Nafion solution to prepare a slurry, which is coated on the surface of a conductive substrate for use as an electrode.
10. The use according to claim 9, characterized in that: The ratio of TD-COF / Ni-doped FeOOH composite to electrode area is 0.8~2.0 mg:1 cm²; the conductive substrate is carbon cloth, nickel foam or glassy carbon electrode.