Metal organic framework loaded iridium oxide catalytic material as well as preparation method and application thereof

Abstract

The invention discloses a metal organic framework loaded iridium oxide catalytic material as well as a preparation method and application thereof, and belongs to the technical field of electrolytic catalyst preparation. The preparation method is mainly based on a foamed nickel supported ZIF-67 / NF composite material, iridium (Ir) is introduced through an impregnation method to improve the catalytic performance, the introduction of Ir not only significantly enhances the activity of the catalyst in OER, but also improves the performance of the catalyst in HER by adjusting the electronic structure of Co (OH) 2. The conductivity of the catalyst is optimized by the synergistic effect of the amorphous characteristic of IrOx and the Co (OH) 2 matrix, the overpotential of hydrogen evolution reaction is effectively reduced, and higher electrocatalytic activity and excellent long-term stability are shown.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of electrolytic catalysts, and particularly relates to an iridium oxide catalytic material supported on a metal-organic framework, a preparation method and an application thereof, in particular to a preparation method of an iridium oxide catalytic material supported on a metal-organic framework and its application in alkaline electrocatalytic hydrogen evolution reaction and oxygen evolution reaction. Background Art

[0002] Facing the increasingly severe global energy crisis and environmental pollution problems, developing efficient, economical and environmentally friendly energy storage and conversion technologies has become an important direction of current scientific research. The water splitting reaction, as an ideal green energy conversion pathway, has attracted much attention because it does not produce any harmful emissions during the process of converting water into hydrogen and oxygen. The water splitting reaction includes the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), and its efficiency directly determines the energy conversion efficiency of the electrolytic water process. Electro-catalysts play a crucial role in this process, which can effectively reduce the energy barrier and overpotential of the reaction, thereby improving the energy conversion efficiency.

[0003] Currently, commercial electrolytic water catalysts mainly rely on noble metal-based catalysts, such as IrO used for the oxygen evolution reaction 2 or RuO 2 , and platinum (Pt) used for the hydrogen evolution reaction. In order to overcome the problems of its high cost and scarcity affecting its wide application, more and more researchers are committed to developing transition metal-based catalysts, especially bifunctional catalysts, aiming to reduce the overall cost of water electrolysis and improve the catalytic performance. Such catalysts can not only provide excellent performance in the OER and HER reactions, but also have good stability and low production cost. However, in the process of developing transition metal-based bifunctional catalysts, especially catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), in addition to the problem of slow reaction kinetics of transition metal-based catalysts in OER and HER, there is also the problem of poor stability. For example, the Chinese invention patent with the publication number CN115505949A discloses "an iridium-doped metal-organic framework-derived material, a preparation method thereof and an application in electrocatalytic oxygen evolution", but the material prepared by the disclosed method still has the technical problems of low OER activity and low stability.

[0004] Therefore, how to improve the reaction kinetics and stability of transition metal-based catalysts is a huge challenge for the further optimization of the green energy conversion process. Summary of the Invention

[0005] To overcome the disadvantages of the above-mentioned existing technologies, the purpose of the present invention is 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 purpose, the present invention adopts the following technical solutions:

[0007] The present invention discloses a preparation method of a metal-organic framework-supported iridium oxide catalytic material, including: by an impregnation method, introducing iridium into a ZIF-67 / NF composite material supported by nickel foam containing Co(OH) 2 to obtain an IrOx / Co(OH) 2 / NF composite material, which is the metal-organic framework-supported iridium oxide catalytic material.

[0008] Further, the ZIF-67 used in the present invention is a metal-organic framework (MOF) material. The "ZIF" in its name represents "Zeolitic Imidazolate Frameworks" (zeolite imidazolate framework structure material), and "67" indicates that it is the 67th discovered type of ZIF-based MOF material.

[0009] Further, in the prepared product IrOx / Co(OH) 2 / NF composite material, x has no special meaning. As understood by those skilled in the art, it represents that iridium exists in the form of an oxide in this composite material.

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

[0011] Immerse the ZIF-67 / NF composite material supported by nickel foam containing Co(OH) 2 into a mixed solution containing an alkali and an iridium precursor, carry out a water bath reaction at 60 - 80 °C for 0.5 - 2 h, and then perform washing and drying treatments to obtain the IrOx / Co(OH) 2 / NF composite material.

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

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

[0014] Specifically, ammonia and CO are gradually hydrolyzed at 60–80 °C2 , thus causing the pH value of the system to rise slowly. This gentle pH regulation helps the iridium precursor (such as iridium trichloride) to precipitate uniformly on the surface of Co(OH) 2 / NF and be partially oxidized to form IrOx. At the same time, it can also control the precipitation rate and avoid uneven particle size or agglomeration caused by a sudden increase in pH value.

[0015] The iridium precursor uses iridium trichloride, hexachloroiridic acid (H 2 IrCl 6 ), iridium(III) nitrate (Ir(NO 3 )) 3 ) and other iridium precursors with good water solubility and can be converted into active iridium oxides under the reaction conditions.

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

[0017] Fully mix the dimethylimidazole solution and cobalt nitrate solution to form a ZIF-67 precursor solution;

[0018] Then immerse the nickel foam into the ZIF-67 precursor solution, soak for 3-5 hours, wash and dry to obtain the 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 preferably 32.85 mg mL-1; the concentration of the cobalt nitrate solution is preferably 14.55 mg mL-1.

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

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

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

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

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

[0026] The metal-organic framework supported iridium oxide catalytic material prepared by the present invention has a cluster composite structure and there is an interfacial protection effect: the strong electronic coupling between IrO x and Co(OH) 2 (the 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. After experimental verification, it has a lower overpotential at a current density of 50 mA cm -2 . At the same time, in the stability test, the metal-organic framework supported iridium oxide catalytic material of the present invention did not show obvious overpotential degradation after continuous operation for 500 hours, which all indicate that the metal-organic framework supported iridium oxide catalytic material prepared by the present invention has higher OER activity and stronger stability than the prior art products.

[0027] Furthermore, in the present invention, a solution containing Ir element is fully reacted with the precursor under the water bath condition of 60-80 °C by an impregnation method, so that the Ir element is introduced into ZIF-67@NF in the form of IrOx, and then a cluster composite structure is formed, and the working particle size is smaller. While the prior art document (the invention patent disclosed in CN115505949A) is to soak the obtained material in a mixed solution of nickel nitrate, iridium chloride and urea, and gradually etch and destroy the ZIF 67 precursor under the weak alkaline environment provided by urea, and the dissolved cobalt ions co-precipitate with nickel ions and iridium ions to generate LDH. Using ZIF 67 as a template, etching and precipitation are carried out from the outside to the inside, and the ZIF 67 structure is transformed into flaky CoNiIr ZLDH (ZLDH is the LDH obtained by etching MOF), which is a ZIF 67-derived structure, so that Ni and Ir elements are introduced to form a doping structure. It can be seen that the products prepared by different process 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 by the present invention has higher OER activity and stronger stability. Description of the Drawings

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

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

[0030] Figure 3 is the LSV performance test chart of HER for different catalysts.

[0031] Figure 4 is the LSV performance test chart of OER for different catalysts.

[0032] Figure 5 is the overall water splitting performance test chart.

[0033] Figure 6 is the 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 mode

[0034] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0037] 1. The present invention provides methods for preparing metal organic framework catalytic materials doped with iridium in different proportions at different water bath temperatures and times, and methods for preparing metal organic framework catalytic materials doped with iridium in different proportions. 2 The preparation of the NF / MS composite material is shown in the following example.

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

[0039] Example 1

[0040] 0.025mmol IrCl 3 Doped IrOx / Co(OH) 2 The preparation of the / NF composite material comprises the following steps:

[0041] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0043] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0044] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0045] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 7.46 mg) in a mixed solution (12 mL) and placed in a 70°C constant temperature water bath for 1 hour;

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

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

[0048] Example 2

[0049] 0.05mmol IrCl 3 Doped IrOx / Co(OH) 2 The preparation of the / NF composite material comprises the following steps:

[0050] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0052] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0053] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0054] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 14.9 mg) in a mixed solution (12 mL) and placed in a 70°C constant temperature water bath for reaction for 1 hour;

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

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

[0057] Example 3

[0058] 0.1mmol IrCl 3 Doped IrOx / Co(OH) 2 The preparation of the / NF composite material comprises the following steps:

[0059] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0061] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0062] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0063] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 29.9 mg) in a mixed solution (12 mL) and placed 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 by-products;

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

[0066] Example 4

[0067] 0.15mmol IrCl 3 Doped IrOx / Co(OH) 2Preparation of the IrOx / Co(OH) / NF composite material includes the following steps:

[0068] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg / mL -1 ) and a cobalt nitrate (Co(NO 3 )) solution (40 mL, concentration 14.55 mg / mL 2 ); -1

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

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

[0071] D. Subsequently, take out the nickel foam soaked in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite material.

[0072] E. Immerse the prepared ZIF-67 / NF into a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl 3 , 44.8 mg) and react in a 70 °C constant temperature water bath for 1 hour;

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

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

[0075] The difference between Examples 1 - 4 lies in: the mass of added IrCl 3 is different.

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

[0077] Example 5

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

[0079] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg / mL​-1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

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

[0082] D. Subsequently, take out the nickel foam soaked in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite material.

[0083] E. Immerse the prepared ZIF-67 / NF into a mixed solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 14.9 mg) (12 mL) and react in a 60 °C constant temperature water bath for 1 hour;

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

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

[0086] Example 6

[0087] Preparation of iridium-doped IrOx / Co(OH) 2 / NF composite material at a water bath temperature of 70 °C, including the following steps:

[0088] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

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

[0091] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0092] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 14.9 mg) in a mixed solution (12 mL) and placed in a 70°C constant temperature water bath for reaction for 1 hour;

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

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

[0095] Example 7

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

[0097] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0099] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0100] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0101] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 14.9 mg) in a mixed solution (12 mL) and placed in a constant temperature water bath at 80 °C for 1 hour;

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

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

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

[0105] 3. Iridium-doped IrOx / Co(OH) at different water bath times 2 Preparation of NF / MS composites

[0106] Example 8

[0107] IrOx / Co(OH) doped with iridium under 0.5h water bath time 2 The preparation of the / NF composite material comprises the following steps:

[0108] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0110] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0111] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0112] E. The prepared ZIF-67 / NF was immersed in a solution containing urea (0.5 g) and iridium trichloride (IrCl 3 , 14.9 mg) in a mixed solution (12 mL) and placed in a 70°C constant temperature water bath for 0.5 h;

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

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

[0115] Example 9

[0116] Preparation of iridium-doped IrOx / Co(OH) 2 / NF composite under 1h water bath time, including the following steps:

[0117] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and a cobalt nitrate (Co(NO 3 )) solution (40 mL, concentration 14.55 mg mL 2 ); -1 )

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

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

[0120] D. Subsequently, take out the nickel foam soaked in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite.

[0121] E. Immerse the prepared ZIF-67 / NF into a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl 3 , 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 several times with deionized water to remove the unreacted substances and by-products;

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

[0124] Example 10

[0125] Preparation of iridium-doped IrOx / Co(OH) 2 / NF composite under 1.5h water bath time, including the following steps:

[0126] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and a cobalt nitrate (Co(NO 3 )) 2 ) solution (40 mL, concentration 14.55 mg mL -1);

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

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

[0129] D. Subsequently, take out the nickel foam soaked in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite material.

[0130] E. Immerse the prepared ZIF-67 / NF into a mixed solution (12 mL) containing urea (0.5 g) and iridium trichloride (IrCl 3 , 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 several times with deionized water to remove unreacted substances and by-products;

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

[0133] Example 11

[0134] Preparation of iridium-doped IrOx / Co(OH) 2 / NF composite material under 2h water bath time, including the following steps:

[0135] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and a cobalt nitrate (Co(NO 3 )) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

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

[0138] D. Subsequently, take out the nickel foam soaked in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite material.

[0139] E. Immerse the prepared ZIF-67 / NF into a mixed solution (12 mL) containing urea (0.5 g) and iridium(III) chloride (IrCl 3 , 14.9 mg), and react it in a 70 °C constant temperature water bath for 2 hours;

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

[0141] G. Dry the sample after washing in step F in a vacuum drying oven to finally obtain the IrOx / Co(OH) 2 / NF composite material.

[0142] The difference between Examples 8 - 11 lies in the different reaction times in the constant temperature water bath treatment.

[0143] Example 12

[0144] Preparation of 0.03 mmol Ir(NO 3 ) 3 -doped IrOx / Co(OH) 2 / NF composite material, including the following steps:

[0145] A. First, prepare a dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and a cobalt(II) nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

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

[0148] D. Subsequently, take out the nickel foam after soaking in step C, wash it with deionized water to remove the residual precursor solution, and dry it at 70 °C to obtain the ZIF-67 / NF composite material.

[0149] E. Immerse the prepared ZIF-67 / NF into a mixed solution (12 mL) containing ammonium carbonate (1 mmol) and iridium(III) nitrate (Ir(NO 3 ) 3 , 0.03 mmol), and react it in a 70 °C constant temperature water bath for 1 hour;

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

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

[0152] Example 13

[0153] 0.05mmol H 2 IrCl 6 Doped IrOx / Co(OH) 2 The preparation of the / NF composite material comprises the following steps:

[0154] A. First, prepare dimethylimidazole (DMI) solution (40 mL, concentration 32.85 mg mL -1 ) and cobalt nitrate (Co(NO 3 ) 2 ) solution (40 mL, concentration 14.55 mg mL -1 );

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

[0156] C. Then immerse nickel foam (Nickel Foam, NF, size 2×4 cm) into the solution mixed in step B for 4 hours.

[0157] D. Then, the nickel foam after soaking in step C was taken out, washed with deionized water to remove the residual precursor solution, and dried at 70° C. to obtain a ZIF-67 / NF composite material.

[0158] E. The prepared ZIF-67 / NF was immersed in a solution containing ammonium carbonate (2 mmol) and hexachloroiridic acid (H 2 IrCl 6 , 0.05 mmol) in a mixed solution (12 mL) and placed 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 by-products;

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

[0161] 2. OER and HER performance testing

[0162] In the above embodiments, metal-organic framework catalytic materials doped with iridium in different proportions at different water bath temperatures and times were prepared by the impregnation method. Through Figure 1 the scanning electron microscope images and Figure 2 the Raman shift diagram in (a) in

[0163] proved the successful preparation. For the IrOx / Co(OH) 2 / NF composite material prepared in Example 1, the high-magnification transmission electron microscope images (as shown in Figure 6 ) clearly show that the product is a cluster composite structure, and there is the following interface protection effect: The strong electron coupling between IrO x and Co(OH) 2 (the 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. By comparing the low-magnification transmission electron microscope images shown in the invention patent with the publication number CN115505949A, it can be clearly seen that its product is a doped structure. This structural difference will lead to the strength of the interface protection effect, and the interface protection effect mainly exists in the interface structure of the composite material. The interface protection effect can enhance the interface stability of the catalyst, prevent the catalyst from failing due to interface reactions or physical abrasion during the electrolysis of water, and a stable interface helps to keep the active sites of the catalyst from being damaged, thereby extending the service life of the catalyst. The specific functions are as follows:

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

[0165] 2. Regulate reaction kinetics: Through the interface protection effect, the electronic structure and chemical properties of the catalyst surface can be regulated, thereby affecting the kinetic process of the water electrolysis reaction. For example, in the alkaline water electrolysis hydrogen evolution reaction, the interface 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. Enhance the synergistic effect of multiple components: For multi-component catalysts, the interface protection effect can enhance the synergistic effect between different components and optimize the overall performance of the catalyst. For example, when loading metal clusters on metal oxides or hydroxides, the interface protection effect can promote the electron coupling and interaction between the two, thereby improving the catalytic activity of the catalyst.

[0167] Further analysis shows that in addition to the structural differences of the products described above, the differences in the working particle size will also lead to different performances of the two products. As shown in Figure 4As shown, through high - power transmission electron microscopy scanning, it can be clearly seen that the particle size of the working IrOx clusters during the electrocatalytic process is extremely small, reaching less than 2 nm. In the invention patent disclosed in CN115505949A, only the low - power transmission electron microscopy image of CoNiIr ZLDH@NF is mentioned in its product, and the conclusion is obtained that a three - dimensional porous coating layer is formed on the surface of the nickel foam substrate, the pore walls of the three - dimensional porous coating layer are composed of nanosheets with a thickness of about 5 nm, and Co, Ni, and Ir elements are evenly distributed in the nanosheets. The specific existence form and working particle size of Ir in the product are not clearly mentioned. During the working process of the electrolytic water catalyst, the size of the working particle size has a significant impact on its performance, which is mainly reflected in the following aspects:

[0168] 1. Exposure of active sites: A smaller particle size usually means that the catalyst has a higher specific surface area, thus being able to expose more active sites and improving the efficiency of the catalytic reaction. While a larger particle size may cause some active sites to be partially obscured, reducing the utilization rate of the catalyst.

[0169] 2. Charge transfer efficiency: A smaller particle size can shorten the transport paths of ions and electrons, reduce the transport resistance, and thus improve the charge transfer efficiency. While a larger particle size may lead to longer transport paths of ions and electrons, increase the transport resistance, and reduce the electrolytic water efficiency.

[0170] 3. Dispersibility of the catalyst: A smaller particle size is more likely to be evenly dispersed in the electrolyte, forming a more uniform catalyst layer, thereby improving the electrolytic water performance. While a larger particle size may cause the catalyst to be unevenly dispersed in the electrolyte, forming larger aggregates and reducing the electrolytic water efficiency.

[0171] Therefore, the product of the present invention has higher OER activity and stronger stability compared to the product disclosed in CN115505949A.

[0172] At the same time, during the performance test in this part, commercially available platinum catalyst (Pt / C), Co(OH) 2 / NF and IrO 2 are selected as comparisons, and the results are as Figures 3 - 5 shown.

[0173] It can be seen that the IrOx / Co(OH) 2 / NF composites prepared in Examples 2, 6, and 9 have relatively excellent catalytic performance. Through the Figure 3 HER and Figure 4 OER LSV performance test diagrams, it can be observed that the IrOx / Co(OH) 2 / NF catalyst has a current density of 10 mA / cm 2showed an overpotential of only 36.8 mV, significantly lower than that of commercial platinum catalyst (Pt / C) and Co(OH) 2 / NF. Meanwhile, in the oxygen evolution reaction, the current density reached 10 mA / cm 2 when it showed an overpotential of 215 mV, superior to that of commercial IrO 2 catalyst. In addition, in the overall water splitting reaction, the electrolyzer based on IrOx / Co(OH) 2 / NF only required a cell voltage of 1.55 V to reach a current density of 100 mA cm -2 and showed excellent stability during 500 hours of long-term operation, far exceeding that of traditional IrO 2 or Pt / C catalysts. Therefore, the present invention significantly improved the electrocatalytic water splitting performance and the stability of long-term operation through the synergistic effect of the ZIF-67 / NF substrate and iridium-doped Co(OH) 2 .

[0174] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of an iridium oxide catalytic material supported by a metal-organic framework. This preparation method is mainly based on a ZIF-67 / NF composite supported by nickel foam, and iridium (Ir) is introduced by an impregnation method to improve the catalytic performance. The introduction of Ir not only significantly enhanced the activity of the catalyst in OER, but also improved its performance in HER by regulating the electronic structure of Co(OH) 2 . The amorphous characteristics of IrOx and the synergistic effect of the Co(OH) 2 matrix optimized the conductivity of the catalyst and effectively reduced the overpotential of the hydrogen evolution reaction, demonstrating higher electrocatalytic activity and excellent long-term stability.

[0175] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a metal organic framework supported iridium oxide catalytic material, characterized in that: include: Iridium was introduced into the ZIF-67 / NF composite material supported by nickel foam containing Co(OH)2 by an impregnation method, and an IrOx / Co(OH)2 / NF composite material with a composite cluster structure, i.e., a metal organic framework-supported iridium oxide catalytic material, was obtained through reaction.

2. The method for preparing a metal organic framework-supported iridium oxide catalytic material according to claim 1, characterized in that: include: The ZIF-67 / NF composite material supported by nickel foam containing Co(OH)2 is immersed in a mixed solution containing an alkali and an iridium precursor, reacted at 60-80°C for 0.5-2h, and then washed and dried to obtain an IrOx / Co(OH)2 / NF composite material.

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

4. The method for preparing a metal organic framework-supported iridium oxide catalytic material according to claim 2, characterized in that: The base is urea, ammonium carbonate or ammonium bicarbonate; the iridium precursor is iridium trichloride, hexachloroiridic acid and iridium nitrate.

5. The method for preparing a metal organic framework-supported iridium oxide catalytic material according to any one of claims 1 to 4, characterized in that: The preparation method of the ZIF-67 / NF composite material supported by nickel foam containing Co(OH)2 is as follows: The dimethylimidazole solution and the cobalt nitrate solution are fully mixed to form a ZIF-67 precursor solution; Then, the nickel foam is 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.

6. The method for preparing a metal organic framework-supported iridium oxide catalytic material according to claim 5, characterized in that: 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.

7. The method for preparing a metal organic framework-supported iridium oxide catalytic material according to claim 5, characterized in that: The drying temperature is 60-80℃.

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

9. Use of the metal organic framework-supported iridium oxide catalytic material according to claim 8 in an alkaline electrocatalytic hydrogen evolution reaction.

10. Use of the metal organic framework-supported iridium oxide catalytic material according to claim 8 in oxygen evolution reaction.

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