A multi-metal MOFs array catalyst grown on the surface of a metal substrate and a preparation method and application thereof

Abstract

The present application relates to the field of catalysis technology, and particularly relates to a method for preparing a multi-metal MOFs array catalyst grown on the surface of a metal substrate under room temperature conditions, a multi-metal MOFs array catalyst grown on the surface of a metal substrate prepared by the method, and application of the catalyst in electrocatalytic OER. The method for preparing the OER catalyst comprises: synthesizing a multi-metal hydroxide by a co-precipitation method; and mixing a multi-metal hydroxide solution, an organic ligand solution, a metal substrate and a metal salt under room temperature for a period of time, to obtain a multi-metal MOFs array catalyst grown on the surface of a metal substrate. The present application uses a sacrificial hydroxide template method to grow a multi-metal MOFs array on the surface of a metal substrate to obtain an OER catalytic electrode, which avoids the dependence on a binder and harsh synthesis conditions, and is suitable for various metal elements and proportions. The OER catalyst has the advantages of excellent OER catalytic activity and excellent stability.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and more particularly to a method for preparing a multi-metal MOF array catalyst grown on a metal substrate at room temperature, the multi-metal MOF array catalyst grown on a metal substrate, and the application of the catalyst in electrocatalytic OER. Background Technology

[0002] The electrochemical oxygen evolution reaction (OER) plays a crucial role in energy conversion and storage systems such as hydrogen fuel cells, zinc-air batteries, and water electrolysis hydrogen production equipment.

[0003] Metal-organic frameworks (MOFs) possess high specific surface areas and tunable nanostructures, making them an effective way to integrate transition metal elements as supports for developing transition metal-based OER catalysts. However, MOFs are typically in powder form, requiring binders (such as Nafion) to load them onto electrodes. This not only limits the catalyst loading but also leads to high charge transfer resistance at the interface. Furthermore, existing synthetic methods are limited by factors such as the inability to form array structures with large specific surface areas, incompatibility with multiple metal components, and dependence on stringent synthetic conditions (such as hydrothermal methods). These problems result in less than ideal performance and limited tunability of MOFs as OER catalysts.

[0004] The above research indicates that developing a method for preparing multi-metal MOF array catalysts grown on metal substrates at room temperature is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-metal MOF array catalyst grown on the surface of a metal substrate, its preparation method and application.

[0006] The present invention also provides a multi-metal MOF array catalyst grown on the surface of a metal substrate prepared by the above method. This OER catalyst has the advantages of excellent catalytic activity and excellent stability in the oxygen evolution reaction.

[0007] This invention also provides an application of the above-mentioned multi-metal MOF array catalyst grown on a metal substrate in the electrocatalytic oxygen evolution reaction. The inventors' research shows that, when this multi-metal MOF array catalyst grown on a metal substrate is used as the working electrode to catalyze the electrochemical oxygen evolution reaction, it achieves a high efficiency of 1 mol L⁻¹. -1 The lowest Tafel slope was 17 mV dec when working in potassium hydroxide solution. -1 The current density is 10 mA cm⁻¹ -2The lowest overpotential was 197 mV, indicating that the OER catalyst has excellent catalytic activity for the oxygen evolution reaction, and therefore has good application prospects in industrial water electrolysis.

[0008] The first aspect of the object of this invention is:

[0009] A room-temperature method for preparing multi-metal MOF array catalysts grown on a metal substrate is provided, which employs a sacrificial hydroxide template method. The specific steps are as follows:

[0010] The first step involves mixing a metal A salt solution and a sodium hydroxide solution, followed by centrifugation and washing to obtain a multi-metal hydroxide. The second step involves mixing the multi-metal hydroxide solution, a trimesic acid solution, and a metal B substrate at room temperature with shaking for a period of time to obtain a multi-metal MOF array catalyst grown on the metal substrate surface. Alternatively, the second step can involve mixing the multi-metal hydroxide solution, trimesic acid solution, a metal B substrate, and a metal C salt at room temperature with shaking for a period of time to obtain the same multi-metal MOF array catalyst grown on the metal substrate surface.

[0011] In this invention, the polymetallic hydroxide is prepared according to existing methods, and in this invention, it is prepared by co-precipitation.

[0012] In this invention, when only metal B substrate is used in the second step without adding metal C salt, metal A and metal B together contain two types of metals. Metal A contains cobalt and nickel, and the metal B substrate is cobalt foam or nickel foam. Alternatively, metal A and metal B together contain 3 to 5 types of metals. Metal A contains cobalt and nickel, and 1 to 3 of the following: chromium, iron, copper, zinc, lanthanum, cerium, and europium; the metal B substrate is any one of cobalt foam, iron foam, nickel foam, or iron-nickel foam.

[0013] Alternatively, in the second step, when metal B is used as the substrate and metal C salt is added, metals A, B, and C together contain 3 to 5 metals. Among them, metal A contains cobalt and nickel, and 0 to 3 of chromium, iron, copper, zinc, lanthanum, cerium, and europium; metal B substrate is any one of foamed cobalt, foamed iron, foamed nickel, or foamed iron-nickel; metal C contains 1 to 3 of chromium, iron, copper, zinc, lanthanum, cerium, and europium.

[0014] In this invention, the combined molar fraction of cobalt and nickel in metal A is 66.7% to 100%. The total metal content in metal C salt is 0.01% to 10% of the total metal content in the polymetallic hydroxide solution. By changing the metal content within the above range, the metal content in the multimetal MOF array catalyst grown on the metal substrate surface can be controlled. Too high or too low a content will prevent MOF array growth.

[0015] In this invention, the concentration of the polymetallic hydroxide solution is 0.4~0.5 mol / L. -1 The concentration of the pyromellitic acid solution is 0.3~0.75 mol / L. -1 By adjusting the concentrations of the polymetallic hydroxide solution and the trimesin solution within the aforementioned range, the MOF array can fully cover the metal substrate surface. Concentrations that are too high or too low will prevent MOF array growth.

[0016] In this invention, the solvents in the polymetallic hydroxide solution and the trimellitic acid solution are solvents commonly used in the field of material synthesis, such as DMF, deionized water, and anhydrous ethanol. The volume ratio of the polymetallic hydroxide solution to the trimellitic acid solution is 1:2.2 to 1:1.8; if it is too high or too low, MOF array growth cannot be achieved.

[0017] In this invention, the rotational speed of the oscillating mixture is 200~500 r / min. -1 MOF array growth cannot be achieved when the rotation speed is too low or too high.

[0018] In this invention, the oscillation mixing time is 3 to 15 hours. If the time is too short or too long, MOF array growth cannot be achieved.

[0019] The second aspect of the object of this invention is:

[0020] A multi-metal MOFs array catalyst grown on a metal substrate is provided, which is prepared by the room temperature preparation method of the multi-metal MOFs array catalyst grown on a metal substrate.

[0021] The third aspect of the object of this invention is:

[0022] This invention provides a method for preparing a multi-metal MOF array catalyst grown on a metal substrate using the room temperature method described above, or the application of the multi-metal MOF array catalyst grown on a metal substrate in the electrocatalytic oxygen evolution reaction.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The room temperature preparation method of the multi-metal MOFs array catalyst grown on the surface of the metal substrate provided by the present invention uses the sacrificial hydroxide template method to construct the multi-metal MOFs array catalyst grown on the surface of the metal substrate, which avoids the dependence on binders (such as Nafion) and harsh reaction conditions (such as hydrothermal reaction). The process is simple and easy to operate. By changing the metal composition and ratio in the multi-metal hydroxide, the metal types and contents in the MOFs can be adjusted, which is beneficial to the regulation of catalyst function and performance optimization.

[0025] (2) The multi-metal MOF array catalyst grown on the surface of a metal substrate provided by the present invention has an array bonding structure, which provides a large electrochemical active area; the multi-metal MOF array is connected to the metal substrate through an amorphous MOF layer, ensuring the robustness and reliability of the structure; it has excellent catalytic performance and stability at 10, 100, 300, and 500 mA·cm⁻¹ -2 At current densities of 100 mAcm, it exhibited overpotentials as low as 197, 224, 290, and 321 mV, respectively, and showed overvoltages of 107, 224, 290, and 321 mV for 240 consecutive hours. -2 The potential remained stable and the structure did not collapse during the OER test.

[0026] Figure and Table Description

[0027] Figure 1 This is a micrograph of the multimetal MOF array catalyst grown on the surface of a metal substrate prepared in Example 1.

[0028] Figure 2 This is a SEM image of the multimetal MOF array catalyst grown on the surface of a metal substrate prepared in Example 1.

[0029] Figure 3 The images show TEM and EDS images of the multi-metal MOF array catalyst grown on the surface of a metal substrate prepared in Example 1.

[0030] Figure 4 These are microscopic images of the multimetal MOF array catalysts grown on the surface of the metal substrate obtained in Examples 2-7.

[0031] Figure 5 The images show SEM and EDS images of the multi-metal MOF array catalysts grown on the surface of the metal substrates prepared in Examples 2-7.

[0032] Figure 6 These are microscopic images of the multimetal MOF array catalysts grown on the surface of a metal substrate, prepared in Examples 8-12.

[0033] Figure 7 The images show SEM and EDS images of the multi-metal MOF array catalysts grown on the surface of the metal substrate prepared in Examples 8-12.

[0034] Figure 8 This is a micrograph of the MOF catalyst grown on the surface of a metal substrate prepared in Comparative Example 1.

[0035] Figure 9 This is a micrograph of the MOF catalyst grown on the surface of a metal substrate prepared in Comparative Example 2.

[0036] Figure 10This is a micrograph of the MOF catalyst grown on the surface of a metal substrate prepared in Comparative Example 3.

[0037] Figure 11 This is a micrograph of the MOF catalyst grown on the surface of a metal substrate prepared in Comparative Example 4.

[0038] Figure 12 This is a micrograph of the MOF catalyst grown on the surface of a metal substrate prepared in Comparative Example 5.

[0039] Figure 13 Microscopic images of MOF catalysts grown on metal substrates prepared in Comparative Example 6.

[0040] Figure 14 The LSV curves are for the multi-metal MOF array catalysts grown on the surface of the metal substrate prepared in Examples 2-7.

[0041] Figure 15 The LSV curves are for the multi-metal MOF array catalysts grown on the surface of the metal substrate prepared in Examples 1 and 8-12.

[0042] Figure 16 The OER catalyst in Example 1 of this invention is at 100 mA cm⁻¹ -2 The diagram shows the operational stability test results under the specified current density.

[0043] Figure 17 The OER catalyst in Example 1 of this invention is at 100 mA cm⁻¹ -2 At a current density of 25°C, 1 mol L -1 SEM image after running in KOH solution for 240 h. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to embodiments and figures, but the implementation of the present invention is not limited thereto.

[0045] In this invention, the polymetallic hydroxide is prepared according to existing methods. In a specific embodiment of this invention, it is prepared by co-precipitation.

[0046] Example 1

[0047] The first step involves preparing cobalt nitrate, nickel nitrate, and europium nitrate in a ratio of 4.75:4.75:0.5 to achieve a total metal ion concentration of 1 mol / L. -1 11.25 ml of aqueous solution; prepare a solution with a concentration of 1 mol / L. -1 22.5 mL of sodium hydroxide aqueous solution; mix the two solutions in a 1:2 volume ratio, centrifuge and wash to obtain polymetallic hydroxide;

[0048] The second step involves dispersing 2.25 mmol of polymetallic hydroxide in 5 mL of deionized water; dissolving 3.33 mmol of trimesic acid in a mixture of 5 mL of anhydrous ethanol and 5 mL of DMF; mixing the two solutions and placing them into a 2×2 cm [material / tablet / material]. 2 Foamed iron was added, and 0.1125 mmol of chromium nitrate was added; the mixture was shaken at 350 rpm for 15 h on a shaker to obtain a multi-metal MOF array catalyst grown on the surface of a metal substrate.

[0049] Figure 1 This is a micrograph of the multimetal MOF array catalyst grown on a metal substrate obtained in Example 1. It shows that the catalyst surface has a uniform and dense array structure.

[0050] Figure 2 The image shows a SEM image of the multi-metal MOF array catalyst grown on the surface of a metal substrate prepared in Example 1. It shows that the catalyst surface has a uniform and dense array structure, and the MOF array is connected to the metal substrate through an amorphous MOF layer.

[0051] Figure 2 The images show the TEM and EDS spectra of the multi-metal MOF array catalyst grown on the metal substrate obtained in Example 1. The EDS spectra show that all elements have clear signals and are uniformly distributed, indicating that the multi-metal MOFs were successfully prepared.

[0052] Example 2

[0053] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0054] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 9.99:0.01.

[0055] In the second step, chromium nitrate is not added.

[0056] Example 3

[0057] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0058] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 8:2.

[0059] In the second step, chromium nitrate is not added.

[0060] Example 4

[0061] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0062] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 7:3.

[0063] In the second step, chromium nitrate is not added.

[0064] Example 5

[0065] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0066] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 6:4.

[0067] In the second step, chromium nitrate is not added.

[0068] Example 6

[0069] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0070] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 5:5.

[0071] In the second step, chromium nitrate is not added.

[0072] Example 7

[0073] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0074] In the first step, europium nitrate is not added, and the ratio of cobalt nitrate to nickel nitrate is 4:6.

[0075] In the second step, chromium nitrate is not added.

[0076] Figure 4 These are microscopic images of the multi-metal MOF array catalysts grown on the surface of metal substrates prepared in Examples 2-7. They demonstrate that changing the metal ratio in the multi-metal hydroxide does not affect the formation of the array structure.

[0077] Figure 5 The images show SEM and EDS images of the multi-metal MOF array catalysts grown on the metal substrate surface prepared in Examples 2-7. The ratio of cobalt and nickel in the MOFs varies with the corresponding ratio in the multi-metal hydroxide, indicating that the elemental ratios in the multi-metal MOF array catalysts grown on the metal substrate surface are adjustable.

[0078] Example 8

[0079] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0080] Europium nitrate is not added in the first step.

[0081] Example 9

[0082] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0083] In the first step, europium nitrate is replaced with copper nitrate.

[0084] Example 10

[0085] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0086] In the first step, europium nitrate is replaced with zinc nitrate.

[0087] Example 11

[0088] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0089] In the first step, europium nitrate is replaced with lanthanum nitrate.

[0090] Example 12

[0091] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this embodiment is basically the same as that in Example 1, except that:

[0092] In the first step, europium nitrate is replaced with cerium nitrate.

[0093] Figure 6 These are microscopic images of the multi-metal MOF array catalysts grown on the surface of metal substrates prepared in Examples 8-12. They demonstrate that changing the quantity and type of metals in the multi-metal hydroxide does not affect the formation of the array structure.

[0094] Figure 7 The images show SEM and EDS images of the multi-metal MOF array catalysts grown on the metal substrate surface prepared in Examples 8-12. The number and type of metal elements in the MOFs vary with the corresponding number and type in the multi-metal hydroxide, indicating that the number and type of elements in the multi-metal MOF array catalysts grown on the metal substrate surface are adjustable.

[0095] Comparative Example 1

[0096] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0097] In the second step, the polymetallic hydroxide is replaced with a mixture of cobalt nitrate, nickel nitrate, and europium nitrate in a ratio of 4.75:4.75:0.5.

[0098] Comparative Example 2

[0099] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0100] In the second step, the amount of polymetallic hydroxide was changed to 1.5 mmol.

[0101] Comparative Example 3

[0102] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0103] In the second step, the amount of pyromellitic acid was changed to 1.125 mmol.

[0104] Comparative Example 4

[0105] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0106] In the second step, the volume of DMF is changed to 1 mL.

[0107] Comparative Example 5

[0108] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0109] In the second step, the rotation speed of the oscillation mixing is changed to 150 rpm.

[0110] Comparative Example 6

[0111] The preparation method of the multi-metal MOF array catalyst grown on the surface of a metal substrate provided in this comparative example is basically the same as that in Example 1, except that:

[0112] In the second step, the oscillation and mixing time is changed to 20 hours.

[0113] Figure 8The image shown is a micrograph of the MOF catalyst grown on the surface of a metal substrate, as shown in Comparative Example 1. It demonstrates that MOF arrays cannot be fabricated without the use of multimetal hydroxides.

[0114] Figure 9 Microscopic images of MOF catalysts grown on metal substrates were prepared for Comparative Example 2. This indicates that the concentration of the multimetal hydroxide solution did not meet the requirement of 0.4–0.5 mol / L. -1 At that time, MOF arrays will not be able to be produced.

[0115] Figure 10 Microscopic images of MOF catalysts grown on metal substrates for Comparative Example 3 are shown. This indicates that the concentration of trimesic acid does not conform to the range of 0.3–0.75 mol / L. -1 At that time, MOF arrays will not be able to be produced.

[0116] Figure 11 The image shown is a micrograph of the MOF catalyst grown on the surface of a metal substrate, as shown in Comparative Example 4. This indicates that MOF arrays cannot be prepared when the volume ratio of the multimetal hydroxide solution to the trimesic acid solution is not within the range of 1:2.2 to 1:1.8.

[0117] Figure 12 The image shown is a micrograph of the MOF catalyst grown on the surface of a metal substrate, as shown in Comparative Example 5. This indicates that MOF arrays cannot be fabricated if the shaking mixing speed is less than 200–500 rpm.

[0118] Figure 13 The image shown is a micrograph of the MOF catalyst grown on the surface of a metal substrate, as shown in Comparative Example 6. This indicates that MOF arrays cannot be fabricated if the shaking mixing time is less than 3–15 h.

[0119] Performance testing

[0120] Figure 14 The LSV curves are for the multi-metal MOF array catalysts grown on the surface of the metal substrate prepared in Examples 2-7.

[0121] Figure 15 The LSV curves are for the multi-metal MOF array catalysts grown on the surface of the metal substrate prepared in Examples 1 and 8-12.

[0122] Figure 14 and Figure 15 This indicates that the catalytic performance can be tuned by adjusting the proportion, quantity, and type of metal elements in the multi-metal MOF array catalyst grown on the metal substrate surface. The multi-metal MOF array catalyst grown on the metal substrate surface exhibits catalytic performance modulation at 10, 100, 300, and 500 mA·cm⁻¹. -2The overpotentials were as low as 197, 224, 290, and 321 mV at the given current densities, indicating that the multi-metal MOF array catalyst grown on the metal substrate has excellent OER catalytic performance.

[0123] Figure 16 The OER catalyst in Example 1 of this invention is at 100 mA cm⁻¹ -2 The diagram shows the operational stability test results under the specified current density.

[0124] Figure 17 The OER catalyst in Example 1 of this invention is at 100 mA cm⁻¹ -2 At a current density of 25°C, 1 mol L -1 SEM image after running in KOH solution for 240 h.

[0125] Figure 16 and Figure 17 This indicates that the catalyst has excellent stability.

[0126] Finally, it should be noted that, obviously, by further adjusting the proportion, quantity, and type of metal elements, better OER catalytic performance and stability can be achieved, or it can be used to catalyze other electrochemical reactions. Therefore, the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit it.

Claims

1. A method for preparing a multi-metal MOF array catalyst grown on a metal substrate, characterized in that, The specific steps are as follows: Step 1: Mix the metal A salt solution and sodium hydroxide solution by stirring, centrifugation and washing to obtain the polymetallic hydroxide; Step 2: Mix the multimetal hydroxide solution, trimesic acid solution, and metal B substrate by shaking at room temperature for a period of time to obtain a multimetal MOF array catalyst grown on the surface of the metal substrate; or, Step 2: Mix the multimetal hydroxide solution, trimesic acid solution, metal B substrate, and metal C salt by shaking at room temperature for a period of time to obtain a multimetal MOF array catalyst grown on the surface of the metal substrate.

2. The preparation method according to claim 1, characterized in that, The metals A and B together contain two types of metals, wherein metal A contains cobalt and nickel, and the substrate of metal B is cobalt foam or nickel foam.

3. The preparation method according to claim 1, characterized in that, The metals A and B together contain 3 to 5 kinds of metals. Metal A contains cobalt and nickel, as well as 1 to 3 kinds of chromium, iron, copper, zinc, lanthanum, cerium and europium. The substrate of metal B is any one of foamed cobalt, foamed iron, foamed nickel and foamed iron-nickel.

4. The preparation method according to claim 1, characterized in that, The metals A, B, and C comprise a total of 3 to 5 metals. Metal A includes cobalt and nickel, and 0 to 3 of the following: chromium, iron, copper, zinc, lanthanum, cerium, and europium. Metal B has a substrate of any one of foamed cobalt, foamed iron, foamed nickel, or foamed iron-nickel. Metal C comprises 1 to 3 of the following: chromium, iron, copper, zinc, lanthanum, cerium, and europium.

5. The preparation method according to any one of claims 1-4, characterized in that, The combined molar fraction of cobalt and nickel in metal A is 66.7% to 100%.

6. The preparation method according to claim 1 or 4, characterized in that, The total amount of metal in the metal C salt is 0.01% to 10% of the total amount of metal in the polymetallic hydroxide solution.

7. The synthesis method according to claim 1, characterized in that, The concentration of the polymetallic hydroxide solution is 0.4~0.5 mol / L. -1 The concentration of the pyromellitic acid solution is 0.3~0.75 mol / L. -1 The volume ratio of pyromellitic acid solution to polymetallic hydroxide solution is 1.8:1 to 2.2:

1.

8. The preparation method according to claim 1, characterized in that, The rotational speed of the oscillating mixer is 200~500 r·min. -1 The oscillation and mixing time is 3 to 15 hours.

9. A multi-metal MOF array catalyst grown on a metal substrate, prepared by any one of the preparation methods according to claims 1 to 8.

10. The application of the catalyst according to claim 9 in the electrocatalytic oxygen evolution reaction.

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