Metal organic framework supported iridium oxide catalytic material, preparation method and application thereof

Abstract

The application discloses a kind of metal organic framework supported iridium oxide catalytic materials and preparation method and application thereof, belong to electrolytic catalyst preparation technical field.The preparation method is mainly based on ZIF-67 / NF composite material supported by nickel foam, and introduces iridium (Ir) by impregnation method to improve catalytic performance, the introduction of Ir not only significantly enhances the activity of catalyst in OER, also by adjusting the electronic structure of Co (OH) 2, improves its performance in HER.IrOx Amorphous state characteristics and the synergistic effect of Co (OH) 2 matrix optimize the conductivity of catalyst, and effectively reduce the overpotential of hydrogen evolution reaction, show higher electrocatalytic activity and excellent long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic catalyst preparation technology, specifically relating to a metal-organic framework supported iridium oxide catalytic material, its preparation method and application, particularly a method for preparing a metal-organic framework supported iridium oxide catalytic material and its application in alkaline electrocatalytic hydrogen evolution reaction and oxygen evolution reaction. Background Technology

[0002] Faced with the increasingly severe global energy crisis and environmental pollution, developing efficient, economical, and environmentally friendly energy storage and conversion technologies has become an important direction in contemporary scientific research. Water splitting, as an ideal green energy conversion pathway, has attracted much attention because it converts water into hydrogen and oxygen without producing any harmful emissions. Water evolution reactions include the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), and their efficiency directly determines the energy conversion efficiency of the water electrolysis process. Electrocatalysts play a crucial role in this process, effectively reducing the energy barrier and overpotential of the reaction, thereby improving energy conversion efficiency.

[0003] Currently, commercially available water electrolysis catalysts mainly rely on noble metal-based catalysts, such as IrO2 or RuO2 used in the oxygen evolution reaction (OER) and platinum (Pt) used in the hydrogen evolution reaction (HER). To overcome the impact of their high cost and scarcity on their widespread application, an increasing number of researchers are dedicated to developing transition metal-based catalysts, particularly bifunctional catalysts, aiming to reduce the overall cost of water electrolysis and improve catalytic performance. These catalysts not only provide excellent performance in OER and HER reactions but also exhibit good stability and low production costs. However, in the development of transition metal-based bifunctional catalysts, especially for OER and HER, in addition to the slow reaction kinetics of transition metal-based catalysts in OER and HER, poor stability is also a problem. For example, Chinese invention patent CN115505949A discloses "An iridium-doped metal-organic framework-derived material and its preparation method and its application in electrocatalytic oxygen evolution," but the material prepared by the disclosed method still suffers from low OER activity and poor stability.

[0004] Therefore, improving the reaction kinetics and stability of transition metal-based catalysts will be a huge challenge for further optimization of green energy conversion processes. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a metal-organic framework supported iridium oxide catalytic material, its preparation method and application, so as to solve the technical problems of slow reaction kinetics and poor stability of existing metal-based catalysts.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing a metal-organic framework-supported iridium oxide catalytic material, comprising: introducing iridium into a ZIF-67 / NF composite material supported by nickel foam containing Co(OH)2 by impregnation, and obtaining an IrOx / Co(OH)2 / NF composite material, i.e., a metal-organic framework-supported iridium oxide catalytic material, by water bath reaction.

[0008] Furthermore, the ZIF-67 used in this invention is a metal-organic framework (MOF) material. The "ZIF" in its name stands for "Zeolitic Imidazolate Frameworks," and "67" indicates that it is the 67th discovered ZIF-type MOF material.

[0009] Furthermore, in the prepared IrOx / Co(OH)2 / NF composite material, x has no special meaning and, as is understood in the art, represents iridium in the form of an oxide in the composite material.

[0010] Specifically, the preparation method of the present invention includes:

[0011] The ZIF-67 / NF composite material containing Co(OH)2 and nickel foam support was immersed in a mixed solution containing alkali and iridium precursor, and reacted in a water bath at 60-80℃ for 0.5-2h. After washing and drying, the IrOx / Co(OH)2 / NF composite material was obtained.

[0012] Furthermore, in the mixed solution of alkali and iridium precursor, the molar ratio of alkali to iridium precursor is (1-3):(0.03-0.06).

[0013] Furthermore, other types of alkalis such as urea, ammonium carbonate, or ammonium bicarbonate are used, mainly to play the role of slow-release alkali, which can gradually release ammonia under heating conditions, playing a similar role in regulating pH value and precipitation process.

[0014] Specifically, under conditions of 60–80℃, the system is gradually hydrolyzed to generate ammonia and CO2, which causes the pH value of the system to rise slowly. This mild pH regulation helps the iridium precursor (e.g., iridium trichloride) to precipitate uniformly on the Co(OH)2 / NF surface and be partially oxidized to form IrOx. At the same time, it can control the precipitation rate and avoid uneven particle size or agglomeration caused by a sudden increase in pH value.

[0015] The iridium precursors used are iridium trichloride, hexachloroiridium acid (H2IrCl6), iridium(III) nitrate (Ir(NO3)3), and other iridium precursors that are water-soluble and can be converted into active iridium oxides under reaction conditions.

[0016] Preferably, the preparation method of the ZIF-67 / NF composite material containing Co(OH)2 and nickel foam support is as follows:

[0017] The dimethylimidazole solution and cobalt nitrate solution were thoroughly mixed to form the ZIF-67 precursor solution;

[0018] Then, the nickel foam was immersed in the ZIF-67 precursor solution for 3-5 hours, washed, and dried to obtain a ZIF-67 / NF composite material supported by nickel foam containing Co(OH)2.

[0019] Furthermore, the concentration of the dimethylimidazole solution is 20-50 mg mL⁻¹, and the concentration of the cobalt nitrate solution is 10-30 mg mL⁻¹; the volume ratio of the dimethylimidazole solution to the cobalt nitrate solution is 1:1.

[0020] More preferably, the concentration of the dimethylimidazole solution is 32.85 mg mL⁻¹; and the concentration of the cobalt nitrate solution is 14.55 mg mL⁻¹.

[0021] Furthermore, the drying temperature is 60-80℃.

[0022] The present invention also discloses a metal-organic framework-supported iridium oxide catalytic material, namely IrOx / Co(OH)2 / NF composite material, prepared by the above method.

[0023] The present invention also discloses the application of the above-mentioned metal-organic framework supported iridium oxide catalytic material in alkaline electrocatalytic hydrogen evolution reaction and oxygen evolution reaction.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention provides a method for preparing iridium oxide catalysts supported on metal-organic frameworks. This method is primarily based on a nickel foam-supported ZIF-67 / NF composite material, and iridium (Ir) is introduced via impregnation to improve catalytic performance. The introduction of Ir not only significantly enhances the catalyst's activity in the hydrogen evolution reaction (OER) but also improves its performance in the hydrogen evolution reaction (HER) by adjusting the electronic structure of Co(OH)₂. The amorphous properties of IrOx and the synergistic effect with the Co(OH)₂ matrix optimize the catalyst's conductivity and effectively reduce the overpotential of the hydrogen evolution reaction, exhibiting higher electrocatalytic activity and excellent long-term stability.

[0026] The metal-organic framework-supported iridium oxide catalyst prepared by this invention has a clustered composite structure and exhibits an interfacial protection effect: IrO x The strong electronic coupling with Co(OH)₂ (a negative shift of the Co 2p binding energy by 0.5 eV in XPS) enhances the structural stability of Co(OH)₂ and suppresses its non-specific exfoliation during synthesis or storage. Experimental verification at 50 mA cm⁻¹ further confirms this. -2 The metal-organic framework-supported iridium oxide catalyst of the present invention exhibits a lower overpotential at a lower current density. Furthermore, in the stability test, no significant overpotential degradation was observed after 500 hours of continuous operation. These findings indicate that the metal-organic framework-supported iridium oxide catalyst prepared by the present invention has higher OER activity and stronger stability than existing products.

[0027] Furthermore, this invention utilizes an immersion method to fully react a solution containing Ir with the precursor under a water bath at 60-80°C, thereby introducing Ir into ZIF-67@NF in the form of IrOx, thus forming a clustered composite structure with a small working particle size. In contrast, existing technology (patent CN115505949A) involves immersing the obtained material in a mixed solution of nickel nitrate, iridium chloride, and urea. Under the weakly alkaline environment provided by urea, the ZIF 67 precursor is gradually etched and destroyed. The dissolved cobalt ions co-precipitate with nickel and iridium ions to form LDH. Using ZIF 67 as a template, etching and precipitation proceed from the outside in, transforming the ZIF 67 structure into a sheet-like CoNiIr ZLDH (ZLDH obtained by etching MOF), a ZIF 67-derived structure, thus introducing Ni and Ir elements and forming a doped structure. It is evident that products prepared by different processing methods have different structures, and this structural difference leads to performance differences. The IrOx / Co(OH)2 / NF composite material with a composite cluster structure prepared in this invention has higher OER activity and stronger stability. Attached Figure Description

[0028] Figure 1Scanning electron microscope images of Co(OH)2 / NF (a) and IrOx / Co(OH)2 / NF (b), low magnification (c) and high magnification (d) of IrOx / Co(OH)2 / NF, HAADF-STEM (e) and its corresponding elemental mapping images of IrOx / Co(OH)2 / NF (f).

[0029] Figure 2 Raman spectra of Co(OH)2 / NF and IrOx / Co(OH)2 / NF (a); Co 2p spectra of Co(OH)2 / NF and IrOx / Co(OH)2 / NF (b); Ir 4f spectra of IrOx / Co(OH)2 / NF (c); O1s spectra of Co(OH)2 / NF and IrOx / Co(OH)2 / NF (d).

[0030] Figure 3 The graph shows the LSV performance test results for HER with different catalysts.

[0031] Figure 4 The graph shows the LSV performance test results for OER with different catalysts.

[0032] Figure 5 This is a graph showing the performance of water hydrolysis.

[0033] Figure 6 This is a high-magnification transmission electron microscope image of the IrOx / Co(OH)2 / NF composite material prepared in Example 1 of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] The present invention will now be described in further detail with reference to the accompanying drawings:

[0037] I. This invention provides methods for preparing metal-organic framework catalytic materials with different proportions of iridium doping under different water bath temperatures and times. The preparation of IrOx / Co(OH)2 / NF composite materials with different proportions of iridium doping is shown in the following examples.

[0038] 1. Preparation of IrOx / Co(OH)2 / NF composites with different iridium doping ratios

[0039] Example 1

[0040] The preparation of 0.025 mmol IrCl3-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0041] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0042] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0043] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0044] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0045] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 7.46 mg) and react in a constant temperature water bath at 70 °C for 1 hour.

[0046] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0047] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0048] Example 2

[0049] The preparation of 0.05 mmol IrCl3-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0050] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0051] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0052] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0053] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0054] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 1 hour.

[0055] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0056] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0057] Example 3

[0058] The preparation of 0.1 mmol IrCl3-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0059] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0060] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0061] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0062] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0063] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 29.9 mg) and react in a 70°C constant temperature water bath for 1 hour.

[0064] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0065] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0066] Example 4

[0067] The preparation of 0.15 mmol IrCl3-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0068] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0069] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0070] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0071] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0072] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 44.8 mg) and react in a constant temperature water bath at 70 °C for 1 hour.

[0073] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0074] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0075] The difference between Examples 1-4 is that the mass of IrCl3 added is different.

[0076] 2. Preparation of iridium-doped IrOx / Co(OH)2 / NF composites at different water bath temperatures

[0077] Example 5

[0078] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material at a water bath temperature of 60℃ includes the following steps:

[0079] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0080] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0081] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0082] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0083] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a constant temperature water bath at 60 °C for 1 hour.

[0084] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0085] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0086] Example 6

[0087] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material at a water bath temperature of 70℃ includes the following steps:

[0088] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0089] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0090] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0091] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0092] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 1 hour.

[0093] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0094] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0095] Example 7

[0096] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material at 80℃ water bath temperature includes the following steps:

[0097] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0098] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0099] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0100] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0101] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in an 80°C constant temperature water bath for 1 hour.

[0102] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0103] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0104] The difference between Examples 5 and 7 is that the treatment temperature of the constant temperature water bath is different.

[0105] 3. Preparation of iridium-doped IrOx / Co(OH)2 / NF composite materials under different water bath times

[0106] Example 8

[0107] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material under a 0.5-hour water bath includes the following steps:

[0108] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0109] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0110] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0111] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0112] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 0.5 hours.

[0113] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0114] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0115] Example 9

[0116] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material under 1-hour water bath time includes the following steps:

[0117] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0118] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0119] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0120] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0121] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 1 hour.

[0122] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0123] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0124] Example 10

[0125] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material under a 1.5-hour water bath includes the following steps:

[0126] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0127] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0128] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0129] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0130] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 1.5 hours.

[0131] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0132] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0133] Example 11

[0134] The preparation of iridium-doped IrOx / Co(OH)2 / NF composite material under a 2-hour water bath includes the following steps:

[0135] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0136] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0137] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0138] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0139] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl3, 14.9 mg) and react in a 70°C constant temperature water bath for 2 hours.

[0140] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0141] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0142] The difference between Examples 8-11 is that the constant temperature water bath treatment time is different.

[0143] Example 12

[0144] The preparation of 0.03 mmol Ir(NO3)3-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0145] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0146] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0147] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0148] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0149] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing ammonium carbonate (1 mmol) and iridium nitrate (Ir(NO3)3, 0.03 mmol) and react in a constant temperature water bath at 70 °C for 1 hour.

[0150] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0151] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0152] Example 13

[0153] The preparation of 0.05 mmol H2IrCl6-doped IrOx / Co(OH)2 / NF composite material includes the following steps:

[0154] A. First, prepare a 40 mL solution of dimethylimidazole (DMI) with a concentration of 32.85 mg / mL. -1 ) and cobalt nitrate (Co(NO3)2) solution (40 mL, concentration 14.55 mg / mL) -1 );

[0155] B. Thoroughly mix the two solutions prepared in step A to form the ZIF-67 precursor solution;

[0156] C. Then, immerse the nickel foam (NF, size 2×4cm) in the solution prepared in step B and soak for 4 hours.

[0157] D. Subsequently, the foamed nickel soaked in step C is removed, washed with deionized water to remove residual precursor solution, and dried at 70°C to obtain ZIF-67 / NF composite material.

[0158] E. Immerse the prepared ZIF-67 / NF in a mixed solution (12 mL) containing ammonium carbonate (2 mmol) and hexachloroiridium acid (H2IrCl6, 0.05 mmol) and react in a 70°C constant temperature water bath for 1 hour.

[0159] F. Wash the sample after the reaction in step E with deionized water several times to remove unreacted substances and byproducts;

[0160] G. The sample washed in step F is dried in a vacuum drying oven to finally obtain the IrOx / Co(OH)2 / NF composite material.

[0161] II. OER and HER Performance Testing

[0162] The above embodiments partially demonstrate the preparation of iridium-doped metal-organic framework catalytic materials with different proportions at different water bath temperatures and times via an impregnation method. Figure 1 Scanning electron microscope images and Figure 2 The Raman displacement diagram in (a) proves that the preparation was successful.

[0163] The IrOx / Co(OH)2 / NF composite material prepared in Example 1 was analyzed by high-magnification transmission electron microscopy (TEM) images (e.g.) Figure 6 As shown, the product clearly has a clustered composite structure and exhibits the following interface protection effect: IrO x The strong electronic coupling with Co(OH)₂ (a negative shift of the Co 2p binding energy by 0.5 eV in XPS) enhances the structural stability of Co(OH)₂ and inhibits its non-specific shedding during synthesis or storage. A comparison with the low-magnification transmission electron microscopy image shown in the invention patent with publication number CN115505949A clearly indicates that the product has a doped structure. This structural difference leads to an increase in the strength of the interfacial protection effect, which mainly exists in the interfacial structure of the composite material. The interfacial protection effect can enhance the interfacial stability of the catalyst, preventing catalyst failure during water electrolysis due to interfacial reactions or physical wear. A stable interface helps to maintain the active sites of the catalyst, thereby extending the catalyst's lifespan. Specific functions are as follows:

[0164] 1. Promotes charge transport: The interface protection effect can optimize charge transport between the catalyst and the electrolyte, reduce the energy barrier of charge transport, and thus increase the rate of water electrolysis reaction.

[0165] 2. Regulation of reaction kinetics: Through the interfacial protection effect, the electronic structure and chemical properties of the catalyst surface can be controlled, thereby affecting the kinetic process of water electrolysis. For example, in the alkaline water electrolysis hydrogen evolution reaction, the interfacial protection effect can promote the enrichment, reorientation and activation of water molecules, reduce the water dissociation energy barrier, and improve the efficiency of the hydrogen evolution reaction.

[0166] 3. Enhanced Synergistic Effects Among Multi-Components: For multi-component catalysts, the interfacial protection effect can enhance the synergistic effects between different components and optimize the overall performance of the catalyst. For example, when metal clusters are supported on metal oxides or hydroxides, the interfacial protection effect can promote electronic coupling and interaction between the two, thereby improving the catalytic activity of the catalyst.

[0167] Further analysis reveals that, in addition to the structural differences described above, variations in working particle size also lead to performance differences between the two products. For example... Figure 4 As shown, high-magnification transmission electron microscopy (TEM) scans clearly reveal that the working IrOx clusters in the electrocatalytic process have extremely small particle sizes, reaching below 2 nm. However, the invention patent published in CN115505949A only mentions that low-magnification TEM images of CoNiIr ZLDH@NF show a three-dimensional porous coating layer formed on the surface of a nickel foam substrate. The pore walls of this three-dimensional porous coating layer are composed of nanosheets approximately 5 nm thick, and Co, Ni, and Ir elements are uniformly distributed within the nanosheets. It does not explicitly mention the specific form of Ir in the product or the working particle size. In the operation of water electrolysis catalysts, the size of the working particle size has a significant impact on its performance, mainly in the following aspects:

[0168] 1. Exposure of active sites: Smaller particle size usually means that the catalyst has a higher specific surface area, which can expose more active sites and improve the efficiency of catalytic reaction. Larger particle size may cause active sites to be partially blocked, reducing the utilization rate of catalyst.

[0169] 2. Charge transport efficiency: Smaller particle size can shorten the transport path of ions and electrons, reduce transport resistance, and thus improve charge transport efficiency. Larger particle size may lead to longer transport paths of ions and electrons, increase transport resistance, and reduce water electrolysis efficiency.

[0170] 3. Catalyst dispersibility: Smaller particle sizes are easier to disperse uniformly in the electrolyte, forming a more uniform catalyst layer, thereby improving the performance of water electrolysis. Larger particle sizes may lead to uneven dispersion of the catalyst in the electrolyte, forming larger agglomerates and reducing the efficiency of water electrolysis.

[0171] Therefore, the product disclosed in this invention has higher OER activity and stronger stability than the product disclosed in CN115505949A.

[0172] Meanwhile, in the performance testing of this section, commercially available platinum catalysts (Pt / C), Co(OH)2 / NF, and IrO2 were used as comparisons, and the results are as follows: Figures 3-5 As shown.

[0173] It can be seen that the IrOx / Co(OH)2 / NF composite materials prepared in Examples 2, 6, and 9 exhibit superior catalytic performance. Figure 3 HER and Figure 4 The LSV performance test graph of the OER shows that the current density of the IrOx / Co(OH)2 / NF catalyst reaches 10 mA / cm² in the hydrogen evolution reaction. 2 It exhibits an overpotential of only 36.8 mV, significantly lower than that of commercial platinum catalysts (Pt / C) and Co(OH)2 / NF, while achieving a current density of 10 mA / cm² in the oxygen evolution reaction. 2 The overpotential was observed to be 215 mV, which is superior to commercial IrO2 catalysts. Furthermore, in the total water splitting reaction, the IrOx / Co(OH)2 / NF-based electrolyzer only required a 1.55 V cell voltage to achieve 100 mA / cm². -2 The current density was significantly higher than that of conventional IrO2 or Pt / C catalysts, and the stability during 500 hours of long-term operation was excellent, far exceeding that of traditional IrO2 or Pt / C catalysts. Therefore, this invention significantly improves the electrocatalytic water splitting performance and long-term stability through the synergistic effect of the ZIF-67 / NF substrate and iridium-doped Co(OH)2.

[0174] To address the shortcomings of existing technologies, this invention provides a method for preparing iridium oxide catalytic materials supported by metal-organic frameworks. This method primarily utilizes a nickel foam-supported ZIF-67 / NF composite material and introduces iridium (Ir) via impregnation to improve catalytic performance. The introduction of Ir not only significantly enhances the catalyst's activity in OER but also improves its performance in HER by adjusting the electronic structure of Co(OH)₂. The amorphous properties of IrOx and the synergistic effect with the Co(OH)₂ matrix optimize the catalyst's conductivity and effectively reduce the overpotential of the hydrogen evolution reaction, exhibiting higher electrocatalytic activity and excellent long-term stability.

[0175] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing an iridium oxide catalytic material supported on a metal-organic framework, characterized in that, include: The ZIF-67 / NF composite material containing nickel foam support was immersed in a mixed solution containing alkali and iridium precursor by impregnation. The reaction was carried out at 60-80 °C for 0.5-2 h, followed by washing and drying to obtain the IrOx / Co(OH)2 / NF composite material with a composite cluster structure, namely the iridium oxide catalyst supported by the metal-organic framework.

2. The method for preparing the metal-organic framework-supported iridium oxide catalytic material according to claim 1, characterized in that, In a mixed solution of alkali and iridium precursor, the molar ratio of alkali to iridium precursor is (1-3):(0.03-0.06).

3. The method for preparing the metal-organic framework-supported iridium oxide catalytic material according to claim 1, characterized in that, The alkali used is urea, ammonium carbonate, or ammonium bicarbonate; the iridium precursor is iridium trichloride, hexachloroiridium acid, or iridium nitrate.

4. The method for preparing the metal-organic framework-supported iridium oxide catalytic material according to any one of claims 1-3, characterized in that, The preparation method of ZIF-67 / NF composite material containing nickel foam support is as follows: The dimethylimidazole solution and cobalt nitrate solution were thoroughly mixed to form the ZIF-67 precursor solution; Then, the nickel foam was immersed in the ZIF-67 precursor solution for 3-5 hours, washed, and dried to obtain the ZIF-67 / NF composite material containing nickel foam support.

5. The method for preparing the metal-organic framework-supported iridium oxide catalytic material according to claim 4, characterized in that, The concentration of the dimethylimidazole solution is 20-50 mg / mL, and the concentration of the cobalt nitrate solution is 10-30 mg / mL; the volume ratio of the dimethylimidazole solution to the cobalt nitrate solution is 1:

1.

6. The method for preparing the metal-organic framework-supported iridium oxide catalytic material according to claim 4, characterized in that, The drying temperature is 60-80 °C.

7. A metal-organic framework-supported iridium oxide catalytic material prepared by the preparation method according to any one of claims 1-6, characterized in that, The iridium oxide catalyst supported by this metal-organic framework has a cluster composite structure, and the IrO in the cluster composite structure is... x The clusters have a particle size of less than 2 nm.

8. The application of the metal-organic framework-supported iridium oxide catalyst of claim 7 in alkaline electrocatalytic hydrogen evolution reaction.

9. The application of the metal-organic framework-supported iridium oxide catalyst of claim 7 in the oxygen evolution reaction.

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