A catalyst for metal-organic coordination, its preparation method and application

Abstract

This invention relates to a metal-organic coordination catalyst, its preparation method, and its application. The preparation method includes the following steps: pretreatment of nickel foam; dissolving ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water to obtain an electrolyte; chemically depositing an intermediate catalyst in the electrolyte; and preparing the catalyst using a solvothermal method, wherein the mixed solution is prepared by dissolving 2,5-dihydroxyterephthalic acid in deionized water, anhydrous ethanol, and N,N-dimethylformamide (DMF), and the intermediate catalyst is completely immersed in the mixed solution to obtain the catalyst. This invention combines electrochemical deposition and a solvothermal method to synthesize a catalyst with a unique rod-like morphology. The samples achieved 100, 500, and 1000 mA / cm². 2 It requires only 264, 296 and 308 mV overpotentials at current densities, respectively, and can maintain stability for 1000 hours at a current density of 1000 mA / cm2; at the same time, it has high production efficiency, low cost, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of catalyst materials, specifically relating to a metal-organic coordinated catalyst, its preparation method, and its application. Background Technology

[0002] Nickel-iron based catalysts have attracted widespread attention in the field of energy catalysis due to their excellent electrochemical activity and relatively low material cost. Notably, these catalysts can be reconstructed in situ during electrochemical testing, transforming into a nickel-iron hydroxyl oxide phase with even higher catalytic activity. This characteristic is one of the key factors driving their in-depth research and application exploration.

[0003] The document CN 118422267 B, titled "A Preparation Method and Electrocatalyst of Iron-Sulfur Doped Nickel Hydroxide Electrocatalyst," has the following problems: 1. It limits the iron ion content in the electrolyte, making it difficult for iron compounds to deposit on the substrate; 2. Only deionized water is added in the hydrothermal reaction, and the reaction time is short, so this step of the reaction is not complete; 3. Because sulfides undergo reconstruction during testing, under long-term operation or high current density conditions, this reconstruction process is often accompanied by instability of the catalyst structure, and may even lead to the dissolution of active components, resulting in a decline in catalytic performance and severely restricting its reliability and durability in practical electrochemical devices.

[0004] Given the problems with existing technologies, there is an urgent need for a nickel-iron-based catalyst with stable structure and catalytic performance that can effectively ensure reliability and durability in electrochemical devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as unstable catalytic performance and difficulty in ensuring reliability and durability in electrochemical devices, this invention provides a metal-organic coordinated catalyst, its preparation method, and its application.

[0006] To achieve the objectives of this invention, the technical solution provided by this invention is: a method for preparing a catalyst that coordinates a metal with an organic compound, comprising the following steps: Step 1: Pretreatment of nickel foam: The nickel foam was ultrasonically cleaned in dilute hydrochloric acid. Step 2, Electrochemical Deposition: 2.1 Dissolve ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water to obtain the electrolyte; 2.2. Using a standard three-electrode electrochemical workstation, with a mercury / mercury oxide electrode as the reference electrode, a carbon rod as the counter electrode, and pretreated nickel foam as the working electrode, deposition was carried out in the electrolyte. 2.3 After deposition, the intermediate catalyst is obtained by washing with deionized water and then air drying.

[0007] Step 3: Solvothermal preparation of catalyst: 3.1 Dissolve 2,5-dihydroxyterephthalic acid in a solution prepared with deionized water, anhydrous ethanol and N,N-dimethylformamide (DMF) to obtain a mixed solution; 3.2 Completely immerse the intermediate catalyst in the mixed solution; 3.3 After the reaction, the catalyst is washed and dried to obtain the catalyst.

[0008] Furthermore, in step 2.1 above, the ratio of ferric nitrate nonahydrate, nickel nitrate hexahydrate, and deionized water is 0.015 mol: 0.005 mol: 100 ml.

[0009] Furthermore, in step 2.2 above, the chronoamperometry method is used for deposition, the deposition voltage is -1.5V relative to the reference electrode, and the deposition time is 5 minutes.

[0010] Furthermore, in step 3.1 above, 0.25-0.75 mmol of 2,5-dihydroxyterephthalic acid is dissolved in 60 ml of solution, which is prepared by deionized water, anhydrous ethanol and N,N-dimethylformamide in a volume ratio of 1:1:1.

[0011] Furthermore, in step 3.3 above, the reaction conditions are 160°C for 12 hours.

[0012] Furthermore, the pretreatment process in step one above is as follows: cut the nickel foam, place it in 30 ml of 3 mol / L dilute hydrochloric acid and sonicate for 15 minutes. After that, wash it repeatedly with anhydrous ethanol several times, and then vacuum dry it; the obtained nickel foam is stored for later use.

[0013] Furthermore, in the pretreatment process of step one above, vacuum drying involves placing the sample in a vacuum oven and drying it at 80°C for 6 hours.

[0014] Furthermore, the catalyst prepared by the above method is a metal-organic coordinated catalyst.

[0015] Furthermore, the above-mentioned metal-organic coordinated catalysts are applied in electrochemical water splitting reactions.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention combines electrochemical deposition and solvothermal methods to synthesize a DHTA-NiFeOOH@NF catalyst with a unique rod-like morphology: In step one, the nickel foam was cleaned with 3 mol / L dilute hydrochloric acid to remove the inert oxides on the surface of the nickel foam, making it easier to synthesize catalysts on it later.

[0017] In step two, nickel-iron hydroxyl oxides can be directly grown on nickel foam using electrochemical deposition, which reduces the impact on catalyst stability caused by morphology reconstruction during the electrochemical reaction. This invention requires only 5 minutes for deposition, improving production efficiency.

[0018] In step three, during the solvothermal preparation process, the introduction of the organic ligand DHTA can bring more hydrophilic functional groups to the catalyst surface, adsorb more water molecules, and thus accelerate the completion of the oxygen evolution reaction.

[0019] 2. The preparation method used in this invention features a short deposition time in the electrochemical deposition step, and in the solvothermal step, after the catalyst and solution are loaded into the reaction vessel, no further manual operation is required. Therefore, the synthesis method is simple and can be mass-produced in a short time. Moreover, the raw materials used are all abundant transition metals, thus inexpensive. This reduces the overall cost and makes it suitable for large-scale industrial production.

[0020] 3. The 0.5-DHTA-NiFeOOH@NF catalyst prepared in this invention exhibits excellent OER performance. In a classic three-electrode system with 1M KOH as the electrolyte, the sample achieves OERs of 100, 500, and 1000 mA / cm². 2 It requires only 264, 296 and 308 mV overpotentials at current densities, respectively, and can maintain stability for 1000 hours at a current density of 1000 mA / cm2. Attached Figure Description

[0021] Figure 1 This is a transmission electron microscope (TEM) image of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention; Figure 2 This is a transmission electron microscope (TEM) image of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention; Figure 3 This is a scanning electron microscope image of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention; Figure 4 The X-ray diffraction pattern of 0.5-DHTA-NiFeOOH@NF in the embodiment of the present invention is shown below. Figure 5 The X-ray photoelectron spectrum of 0.5-DHTA-NiFeOOH@NF in this embodiment of the invention is shown below. Figure 6The X-ray photoelectron spectrum of 0.5-DHTA-NiFeOOH@NF in this embodiment of the invention is shown below. Figure 7 The image shows the Raman spectrum of 0.5-DHTA-NiFeOOH@NF in this embodiment of the invention. Figure 8 The infrared spectrum of 0.5-DHTA-NiFeOOH@NF in this embodiment of the invention; Figure 9 This is the 77K nitrogen adsorption-desorption isotherm of 0.5-DHTA-NiFeOOH@NF in the embodiments of the present invention; Figure 10 This is a linear sweep voltammetry curve of alkaline OER for 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention. Figure 11 This is the Tafel slope curve of 0.5-DHTA-NiFeOOH@NF in the embodiments of the present invention; Figure 12 The C of 0.5-DHTA-NiFeOOH@NF in the embodiments of the present invention dl Value diagram; Figure 13 The EIS curve of 0.5-DHTA-NiFeOOH@NF in the embodiments of the present invention; Figure 14 In this embodiment of the invention, 0.5-DHTA-NiFeOOH@NF was used at 1000 mA / cm. 2 The results of a 1000-hour chronopotential stability test at current density are shown in the figure. Figure 15 The figure shows the test results of the 0.5-DHTA-NiFeOOH@NF anion exchange membrane water splitting system as the anode in this embodiment of the invention, which operated stably for 1000 hours at a current density of 1000 mA / cm2 and at temperatures of 25°C and 60°C. Figure 16 This is the in-situ infrared spectrum of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention; Figure 17 This is the in-situ Raman spectrum of 0.5-DHTA-NiFeOOH@NF in this embodiment of the invention; Figure 18 This is the differential electrochemical mass spectrum of 0.5-DHTA-NiFeOOH@NF in the embodiments of the present invention; Figure 19 This is a theoretical model diagram of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention; Figure 20This is a differential charge density diagram of 0.5-DHTA-NiFeOOH@NF in an embodiment of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments: Example: A method for preparing a metal-organic coordinated catalyst (X-DHTA-NiFeOOH@NF), comprising the following steps: Step 1: Pretreatment of nickel foam: Cut the nickel foam into 1cm pieces. A 2cm sample was placed in 30ml of 3mol / L dilute hydrochloric acid and sonicated for 15 minutes. After sonication, it was washed three times with anhydrous ethanol and then placed in a vacuum oven at 80℃ for 6 hours. The pretreated nickel foam was then stored for later use.

[0023] Step 2, Electrochemical Deposition: First, 0.015 mol of ferric nitrate nonahydrate and 0.005 mol of nickel nitrate hexahydrate were dissolved in 100 ml of deionized water, and the resulting solution was used as the electrolyte in electrochemical deposition.

[0024] Then, using a standard three-electrode electrochemical workstation, with a mercury / mercury oxide electrode as the reference electrode, a carbon rod as the counter electrode, and pretreated nickel foam as the working electrode, deposition was performed in the electrolyte. The deposition voltage was -1.5V relative to the reference electrode, and the deposition time was 5 minutes.

[0025] Finally, the intermediate catalyst obtained after deposition was washed three times with deionized water, and then dried naturally and stored for later use.

[0026] Step 3: Solvothermal preparation of catalyst: First, X mmol (X=0.25, 0.5, 0.75) of 2,5-dihydroxyterephthalic acid (DHTA) was dissolved in 60 ml of a mixed solution of deionized water, anhydrous ethanol and N,N-dimethylformamide (DMF) in a volume ratio of 1:1:1, and then the solution was transferred to the reaction vessel. The intermediate catalyst obtained in the electrochemical deposition step is then placed into the reactor and completely immersed in the solution.

[0027] Finally, the reactor was placed in an oven and reacted at 160°C for 12 hours. During this process, DHTA was able to coordinate with the nickel-iron elements in the intermediate catalyst. After the reaction was completed, the reactor was removed, cleaned, and dried to obtain the final X-DHTA-NiFeOOH@NF catalyst (X=0.25, 0.5, 0.75).

[0028] Among them, 0.5-DHTA-NiFeOOH@NF showed the best performance and is the optimal embodiment.

[0029] Transmission electron microscopy (TEM) image of the 0.5-DHTA-NiFeOOH@NF catalyst prepared in the example is shown below. Figure 1 and Figure 2 The dendritic structure of the nickel foam substrate can be observed; scanning electron microscope image is shown below. Figure 3 The catalyst can be seen to have a rod-like structure; the X-ray powder diffraction pattern is shown below. Figure 4 It can be seen that the catalyst is amorphous, as only the crystalline peaks of nickel foam are observed; the X-ray photoelectron spectroscopy spectrum is shown below. Figure 5 and Figure 6 As can be seen, Ni exists primarily in a structure coordinated with O, while Fe exists primarily as trivalent iron; the Raman spectrum is shown below. Figure 7 We can see peaks belonging to hydroxyl groups in the 3000-3600 cm⁻¹ range, and peaks belonging to nickel hydroxyl oxide and iron hydroxyl oxide around 500 cm⁻¹; see the infrared spectrum. Figure 8 Peaks belonging to C / C, CO, CH bonds and hydroxyl groups can be observed; the 77K nitrogen adsorption-desorption isotherm diagram is shown below. Figure 9 As can be seen, the adsorption-desorption curve of this catalyst is of type IV.

[0030] Electrochemical OER performance testing and mechanism analysis of the best embodiment 0.5-DHTA-NiFeOOH@NF: The 0.5-DHTA-NiFeOOH@NF catalyst obtained in the examples underwent OER performance testing using a conventional three-electrode system on an electrochemical workstation. The electrolyte was a 1M KOH solution, the carbon rod served as the counter electrode, and the mercury / mercuric oxide electrode served as the reference electrode. Because 0.5-DHTA-NiFeOOH@NF is a self-supporting electrode, it only needs to be clamped with a platinum electrode clip to function as the working electrode. The alkaline OER linear sweep voltammetry curve of the 0.5-DHTA-NiFeOOH@NF catalyst is shown below. Figure 10 As can be seen, the catalyst exhibits excellent catalytic activity at 1000 mA / cm². 2 At the given current density, its overpotential requires only 308 mV; the Tafel slope curve and C of the 0.5-DHTA-NiFeOOH@NF catalyst are shown. dl See values ​​and EIS curves. Figure 11 , 12 And 13, we can see that the catalyst has a lower Tafel slope and impedance as well as a higher C dl Value. 1000mA / cm 2 The results of the 1000-hour chronopotential stability test at current density are shown in the figure. Figure 14 The catalyst exhibits significant catalytic stability. The test results of 0.5-DHTA-NiFeOOH@NF as the anode in the anion exchange membrane water splitting system, stable operation for 1000 hours at a current density of 1000 mA / cm² and at temperatures of 25℃ and 60℃, are shown in the figure. Figure 15 As can be seen, this catalyst also exhibits excellent stability in the overall water splitting system; the in-situ infrared and in-situ Raman spectra of 0.5-DHTA-NiFeOOH@NF are shown below. Figure 16 and 17 It can be seen that water molecules gradually accumulated on the catalyst surface and the catalyst underwent some in-situ reconstruction during the test; the differential electrochemical mass spectrum of 0.5-DHTA-NiFeOOH@NF is shown in [reference needed]. Figure 18 It can be seen that the oxygen evolution reaction mechanism of this catalyst is a two-site coupled pathway (OPM); the theoretical model of 0.5-DHTA-NiFeOOH@NF can be found in [link to theoretical model]. Figure 19 As can be seen, the organic ligand DHTA coordinates with nickel and iron atoms through the oxygen atom in the carboxyl group on the benzene ring; the differential charge density plot of 0.5-DHTA-NiFeOOH@NF is shown in [reference needed]. Figure 20 It can be seen that the introduction of DHTA promotes electron transfer and charge distribution in the catalyst.

[0031] The foregoing descriptions are merely preferred embodiments of the present invention and do not impose any limitations on the structure of the present invention. It should be clear to those skilled in the art that any improvements to the present invention, equivalent substitutions of selected components, additions of auxiliary components, selection of specific methods, and other changes made within the scope of knowledge possessed by those skilled in the art, without departing from the spirit of the present invention, all fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a catalyst coordinated with a metal and an organic compound, characterized in that, Includes the following steps: Step 1: Pretreatment of nickel foam: The nickel foam was ultrasonically cleaned in dilute hydrochloric acid. Step 2, Electrochemical Deposition: 2.1 Dissolve ferric nitrate nonahydrate and nickel nitrate hexahydrate in deionized water to obtain the electrolyte; 2.

2. Using a standard three-electrode electrochemical workstation, with a mercury / mercury oxide electrode as the reference electrode, a carbon rod as the counter electrode, and pretreated nickel foam as the working electrode, deposition was carried out in the electrolyte. 2.3 After deposition, the intermediate catalyst is obtained by washing with deionized water and then air drying. Step 3: Solvothermal preparation of catalyst: 3.1 Dissolve 2,5-dihydroxyterephthalic acid in a solution prepared with deionized water, anhydrous ethanol and N,N-dimethylformamide (DMF) to obtain a mixed solution; 3.2 Completely immerse the intermediate catalyst in the mixed solution; 3.3 After the reaction, the catalyst is washed and dried to obtain the catalyst.

2. The method for preparing a metal-organic coordinated catalyst according to claim 1, characterized in that, In step 2.1, the ratio of ferric nitrate nonahydrate, nickel nitrate hexahydrate, and deionized water is 0.015 mol: 0.005 mol: 100 ml.

3. The method for preparing a metal-organic coordinated catalyst according to claim 1, characterized in that, In step 2.2, the chronoamperometry method is used for deposition, the deposition voltage is -1.5V relative to the reference electrode, and the deposition time is 5 minutes.

4. The method for preparing a metal-organic coordinated catalyst according to claim 1, characterized in that, In step 3.1, 0.25-0.75 mmol of 2,5-dihydroxyterephthalic acid is dissolved in 60 ml of a solution prepared by deionized water, anhydrous ethanol and N,N-dimethylformamide in a volume ratio of 1:1:

1.

5. The method for preparing a metal-organic coordinated catalyst according to claim 1, characterized in that, In step 3.3, the reaction conditions are 160°C for 12 hours.

6. The method for preparing a metal-organic coordinated catalyst according to claim 1, characterized in that, The pretreatment process in step one is as follows: cut the nickel foam, place it in 30 ml of 3 mol / L dilute hydrochloric acid and sonicate for 15 minutes. After that, wash it repeatedly with anhydrous ethanol several times, and then vacuum dry it; the obtained nickel foam is stored for later use.

7. The method for preparing a metal-organic coordinated catalyst according to claim 6, characterized in that, In the pretreatment process of step one, vacuum drying involves placing the item in a vacuum oven and drying it at 80°C for 6 hours.

8. The catalyst for metal-organic coordination prepared by the method according to claim 1.

9. The application of the metal-organic coordinated catalyst prepared by the method according to claim 1 in the electrochemical water splitting reaction.

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