Shape-controllable cobalt-based MOF catalytic electrode and preparation method and application thereof

Abstract

The application discloses a morphology-controllable cobalt-based MOF catalytic electrode and a preparation method and application thereof, and belongs to the field of nanometer catalytic material preparation technology and hydrogen production by water electrolysis. The MOF catalytic electrode is prepared by using divalent cobalt ions and a novel 2,4,6,-tris(3,5-dicarboxyphenylamino)-1,3,5-triazine organic ligand as precursors, N,N-dimethylformamide and methanol as solvents, and a hot solvent method in situ growth on a substrate. The morphology of the MOF and the catalytic performance can be controlled by adjusting the solvent ratio, the preparation temperature and time and other conditions. The novel MOF catalytic electrode prepared by the application does not use noble metals, the used material is relatively low in price, can be directly used as a high-performance oxygen evolution and hydrogen evolution electrode, does not need to additionally introduce a binder and is firmly combined with the electrode, simplifies the electrode / catalyst preparation process and has good catalytic stability, and therefore has a wide application prospect in the field of alkaline water electrolysis hydrogen production.

Description

Technical Field

[0001] This invention relates to nanocatalytic material preparation technology and the field of hydrogen production through water electrolysis. Specifically, it relates to MOF catalytic electrodes that are grown in situ on substrate surfaces with controllable morphology, maintain high catalytic activity and high stability under alkaline conditions, as well as their preparation methods and applications. Background Technology

[0002] Hydrogen is considered one of the most promising energy carriers for the future due to its high energy density, abundant raw materials, and the fact that its combustion product is only water. Currently, industrial hydrogen production primarily relies on fossil fuels, and this process exacerbates fossil fuel consumption and carbon dioxide emissions. However, utilizing renewable energy sources such as wind and solar power for water electrolysis to produce hydrogen is an effective technology for sustainable development, considering both energy and environmental factors. Currently, in industrial water electrolysis for hydrogen production, the actual applied voltage often exceeds 2V, far exceeding the theoretical value of 1.23V, resulting in significant energy waste. Furthermore, the oxygen evolution catalysts currently used are mainly Ir and Ru-based compounds, while the hydrogen evolution catalysts are primarily platinum group metal catalysts. Although these catalysts have excellent performance, their scarcity and high cost severely hinder their large-scale application. Therefore, developing inexpensive, efficient, and stable new catalysts is one of the most effective ways to improve the efficiency of water electrolysis for hydrogen production and reduce the cost of hydrogen production.

[0003] MOF (Metal-Organic Fabric) materials are periodic porous coordination polymers that self-assemble using metal ions as bonding sites and organic ligands as support structures through coordination bonds, hydrogen bonds, π-π bonds, van der Waals forces, and other interactions. Due to their numerous metal centers, large specific surface area, rich pore structure, designable topological units, and flexible and tunable composition, they have attracted considerable attention from researchers in the field of catalysis. Cobalt is abundant, inexpensive, environmentally friendly, and contains various variable valence states, making it a widely studied material for cobalt-based water electrolysis catalysts. If suitable organic ligands can be introduced to self-assemble with cobalt ions to form MOF materials with a topologically porous network structure, and the characteristics of the organic ligands and inorganic metal ion components in the MOF structure can be fully utilized, it is hoped that high-performance water electrolysis MOF catalysts can be prepared. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a cobalt-based MOF catalytic electrode that is free of precious metals, has a simple preparation process, can be grown in situ on the substrate surface, and has a morphology that can be controlled, as well as its preparation method and application. The microstructure of the MOF catalytic electrode is adjusted by the controllable self-assembly of cobalt ions with a novel 2,4,6,-tris(3,5-dicarboxyphenylamino)-1,3,5-triazine (H6TDPAT) ligand in different volume ratios of N,N-dimethylformamide (DMF) and methanol solvent, thereby achieving high catalytic activity and high stability in the alkaline water electrolysis catalysis process.

[0005] A method for preparing a cobalt-based MOF catalytic electrode with tunable morphology, characterized by comprising the following steps:

[0006] Divalent cobalt ions were added to a mixed solvent of DMF and methanol and stirred to obtain a cobalt ion solution;

[0007] The organic ligand is then added to a mixed solvent of DMF and methanol and stirred to obtain an organic ligand solution;

[0008] Then, the cobalt ion solution and the organic ligand solution were mixed and stirred and poured into the inner liner of the reactor. The cleaned growth substrate was then placed in the reactor, sealed, and heated in an oven. After the set time was reached, the reactor was removed and allowed to cool naturally. Finally, the reactor was cleaned and dried to obtain a cobalt-based MOF catalytic electrode with tunable morphology.

[0009] In step (1), the solvent is a mixture of DMF and methanol;

[0010] The divalent cobalt ion is cobalt nitrate hexahydrate (Co(NO3)2·6H2O), and the ratio of Co(NO3)2·6H2O to the mixed solvent in the cobalt ion solution is 29.1 mg: 2-20 mL, more preferably 29.1 mg: 5 mL;

[0011] The organic ligand is H6TDPAT, and the ratio of H6TDPAT to the mixed solvent in the organic ligand solution is 12.4 mg: 2-20 mL, more preferably 12.4 mg: 5 mL.

[0012] In step (1), the cobalt ion solution is stirred magnetically for 10 to 30 minutes;

[0013] The organic ligand solution was stirred magnetically for 30–120 minutes.

[0014] The DMF and methanol mixed solvent is DMF and methanol in different volume ratios, with the volume ratio ranging from DMF:methanol = 1:0 to 1:4.

[0015] The growth substrate is foamed iron, foamed nickel, titanium mesh, or carbon cloth.

[0016] The cleaned growth substrate was obtained using the following steps:

[0017] First, sonicate in acetone for 5–15 minutes, then sonicate in ethanol for 5–15 minutes, then sonicate in 0.1–1 mol / L hydrochloric acid for 5–15 minutes, then rinse with deionized water for 3–10 minutes, and finally dry quickly with nitrogen to obtain the cleaned growth substrate.

[0018] The conditions for sealing and heating in an oven are: solvent heating temperature of 80-180℃, and time set from 20 minutes to 72 hours.

[0019] Cleaning and drying specifically include:

[0020] Rinse with a mixture of DMF and methanol for 3 to 5 minutes, then dry in a forced-air drying oven at 50°C to 70°C for 5 to 10 minutes.

[0021] A further preferred embodiment is a method for preparing a cobalt-based MOF catalytic electrode with tunable morphology, comprising the following steps:

[0022] (1) Add 29.1 mg Co(NO3)2·6H2O to a 5 mL DMF and methanol mixture and stir magnetically for 10–30 minutes at room temperature; then add 12.4 mg H6TDPAT to the same mixture and stir magnetically for 30–120 minutes at room temperature; then mix and pour the mixture into a 20 mL polytetrafluoroethylene (PTFE) reactor liner. The DMF and methanol mixture is prepared in different volume ratios, ranging from DMF:methanol = 1:0 to 1:4. The cleaned growth substrate is then placed inside, sealed, and heated in an oven at 80–180 °C for 20 minutes to 72 hours. After the set time, the electrode is removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode is cleaned with the DMF and methanol mixture used in the preparation for 3–5 minutes and dried at 60 °C for 5–10 minutes.

[0023] In step (1), the concentrations of Co(NO3)2·6H2O and organic ligand H6TDPAT are 10 mmol / L and 2 mmol / L, respectively. Due to the different dissolution rates, the preferred stirring times for Co(NO3)2·6H2O and organic ligand H6TDPAT are 20 minutes and 60 minutes, respectively.

[0024] In step (1), the volume ratio of the DMF and methanol mixed solvent ranges from DMF:methanol = 1:0 to 1:4. When using iron foam as a substrate and reacting at 160°C for 24 hours, the morphology of the MOF catalytic electrode nanoarray can be controlled by varying the ratio of DMF to methanol. Preferred preparation conditions are when the solvent is only DMF (i.e., DMF:methanol = 1:0) and DMF:

[0025] When methanol is in a ratio of 4:1 and 2:1, a particulate nanoarray MOF catalytic electrode is prepared; when DMF:

[0026] When methanol is in a 1:1 ratio, a nanoarray MOF catalytic electrode with interconnected particles is obtained; when DMF:

[0027] When methanol = 1:2, a two-dimensional sheet-like nanoarray MOF catalytic electrode is obtained; when DMF: methanol = 1:4, a thin film MOF catalytic electrode is obtained by connecting the collapsed two-dimensional nanosheets.

[0028] In step (1), the growth substrate can be electrodes commonly used in water electrolysis, such as foamed iron, foamed nickel, titanium mesh, and carbon cloth. The cleaning of the electrodes, such as foamed iron, involves first sonicating in acetone for 5–15 minutes, then sonicating in ethanol for 5–15 minutes, followed by sonicating in 0.1–1 mol / L hydrochloric acid for 5–15 minutes, then rinsing with deionized water for 3–10 minutes, and finally quickly drying with nitrogen gas and promptly placing them in the mixed solution for the next experiment. The preferred cleaning times are: sonicating in acetone for 15 minutes, sonicating in ethanol for 15 minutes, sonicating in 1 mol / L hydrochloric acid for 15 minutes, and rinsing with deionized water for 5 minutes.

[0029] In step (1), the solvothermal heating temperature is 80–180℃ (specific experimental conditions are 80℃, 100℃, 120℃, 140℃, 160℃, and 180℃), and the set time is 20 minutes to 72 hours (specific experimental conditions are 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, 120 minutes, 180 minutes, 6 hours, 12 hours, 18 hours, 24 hours, and 72 hours). When using foamed iron as a substrate, the preferred preparation conditions are 160℃ and 24 hours.

[0030] In step (1), the prepared MOF catalytic electrode is cleaned by rinsing it for 3-5 minutes with a solvent of the same DMF to methanol ratio used during its preparation, and then drying it in a forced-air drying oven at 60°C for 5-10 minutes. The preferred conditions are cleaning for 5 minutes and drying at 60°C for 10 minutes.

[0031] A novel morphology-tunable cobalt-based MOF catalytic electrode includes particulate nanoarrays, interconnected nanoarrays, two-dimensional sheet nanoarrays, and thin-film MOF catalytic electrodes prepared using iron foam as a substrate. It also includes MOF catalytic electrodes grown in situ on other substrates (such as nickel foam, titanium mesh, carbon cloth, etc.).

[0032] The novel morphology-tunable MOF catalytic electrodes prepared by this invention exhibit different oxygen evolution and hydrogen evolution performances due to variations in their microstructure. When iron foam is used as the preferred substrate, the resulting two-dimensional sheet-like nanoarray MOF catalytic electrode exhibits optimal oxygen evolution and hydrogen evolution performance under alkaline water electrolysis conditions.

[0033] The novel morphology-tunable cobalt-based MOF catalyst prepared by this invention has the following outstanding advantages compared with existing materials and technologies:

[0034] This invention selects cobalt ions and a novel H6TDPAT organic ligand, and by adjusting the solvent ratio, a morphology-tunable MOF catalytic electrode can be obtained. This electrode maintains high catalytic activity and stability under alkaline water electrolysis conditions. The novel MOF can be grown in situ on various substrate surfaces without the need for binders, simplifying the electrode fabrication process. The prepared MOF catalytic electrode does not use precious metals; the materials used are relatively inexpensive and exhibit high catalytic activity and stability, making it easier to achieve large-scale industrial production. Attached Figure Description

[0035] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided:

[0036] Figure 1 Field emission scanning electron microscope (FESEM) images of a MOF catalytic electrode grown in situ at 160 °C for 24 hours on a foamed iron substrate. (a) Solvent is DMF only, (b) Solvent is DMF:methanol = 1:1, (c) Solvent is DMF:methanol = 1:2, (d) Solvent is DMF:methanol = 1:4.

[0037] Figure 2 This is a high-resolution transmission electron microscope image of a two-dimensional sheet-like nanoarray MOF catalytic electrode.

[0038] Figure 3 (a), (b), and (c) are linear sweep voltammetry curves of oxygen evolution, hydrogen evolution, and two-electrode systems for the foamed iron, granular nanoarray, and two-dimensional sheet nanoarray MOF catalytic electrodes, respectively; (d) is the current density-time curve of the two-dimensional sheet nanoarray MOF catalytic electrode.

[0039] Figure 4 Linear scanning voltammetry curves of MOF catalytic electrodes (foamed iron, particulate nanoarrays (corresponding to SEM images) and two-dimensional sheet nanoarrays (corresponding to SEM images) in a two-electrode system are shown; confirming the influence of controlling the morphology of MOF catalytic electrodes on the performance of full water electrolysis. Detailed Implementation

[0040] The present invention will be described in detail below with reference to embodiments, but the present invention is not limited thereto.

[0041] Example 1

[0042] 29.1 mg Co(NO3)2·6H2O was added to 5 mL of DMF solvent and magnetically stirred for 10 minutes at room temperature. Then, 12.4 mg H6TDPAT was added to 5 mL of DMF solvent and magnetically stirred for 60 minutes at room temperature. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 15 minutes, then in ethanol for 15 minutes, followed by sonication in 1 mol / L hydrochloric acid for 15 minutes. It was then rinsed with deionized water for 5 minutes and rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 160°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode was cleaned with DMF for 3 minutes and dried at 60°C for 10 minutes.

[0043] Example 2

[0044] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 10 minutes at room temperature, with a DMF to methanol volume ratio of 1:1. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 60 minutes at room temperature, again with a DMF to methanol volume ratio of 1:1. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 15 minutes, then in ethanol for 15 minutes, followed by sonication in 1 mol / L hydrochloric acid for 15 minutes. Afterward, it was rinsed with deionized water for 5 minutes and then rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 160°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode was cleaned with a DMF to methanol volume ratio of 1:1 for 3 minutes and dried at 60°C for 10 minutes.

[0045] Example 3

[0046] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 20 minutes at room temperature, with a DMF to methanol volume ratio of 1:2. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 120 minutes at room temperature, again with a DMF to methanol volume ratio of 1:2. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 15 minutes, then in ethanol for 15 minutes, followed by sonication in 1 mol / L hydrochloric acid for 15 minutes. Afterward, it was rinsed with deionized water for 5 minutes and rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 160°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode was cleaned with a DMF to methanol volume ratio of 1:2 for 3 minutes and dried at 60°C for 10 minutes.

[0047] Example 4

[0048] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 20 minutes at room temperature, with a DMF to methanol volume ratio of 1:4. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 120 minutes at room temperature, again with a DMF to methanol volume ratio of 1:4. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 15 minutes, then in ethanol for 15 minutes, followed by sonication in 1 mol / L hydrochloric acid for 15 minutes. Afterward, it was rinsed with deionized water for 5 minutes and then rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 160°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the MOF catalytic electrode was cleaned with a DMF to methanol volume ratio of 1:4 for 3 minutes and dried at 60°C for 10 minutes.

[0049] Example 5

[0050] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 10 minutes at room temperature, with a DMF to methanol volume ratio of 1:1. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 60 minutes at room temperature, again with a DMF to methanol volume ratio of 1:1. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 10 minutes, then in ethanol for 10 minutes, followed by sonication in 1 mol / L hydrochloric acid for 10 minutes. Afterward, it was rinsed with deionized water for 10 minutes and rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 80°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode was cleaned with a DMF to methanol volume ratio of 1:1 for 5 minutes and dried at 60°C for 10 minutes.

[0051] Example 6

[0052] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 10 minutes at room temperature, with a DMF to methanol volume ratio of 1:1. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 60 minutes at room temperature, again with a DMF to methanol volume ratio of 1:1. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The foamed iron was cleaned by sonicating in acetone for 10 minutes, then in ethanol for 10 minutes, followed by sonication in 1 mol / L hydrochloric acid for 10 minutes. Afterward, it was rinsed with deionized water for 10 minutes and rapidly dried with nitrogen. The electrode was then placed in the reactor liner as a growth substrate, sealed, and heated in an oven to 180°C for 24 hours. After the set time, it was removed and allowed to cool naturally. Finally, the prepared MOF catalytic electrode was cleaned with a DMF to methanol volume ratio of 1:1 for 5 minutes and dried at 60°C for 10 minutes.

[0053] Example 7

[0054] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 20 minutes at room temperature, with a DMF to methanol volume ratio of 1:2. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 120 minutes at room temperature, again with a DMF to methanol volume ratio of 1:2. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The nickel foam was cleaned by sonicating in acetone for 10 minutes, then in ethanol for 10 minutes, followed by sonicating in 0.1 mol / L hydrochloric acid for 10 minutes. It was then rinsed with deionized water for 5 minutes and rapidly dried with nitrogen. The resulting material was then placed in the reactor liner as a growth substrate, sealed, and placed in an oven heated to 160°C for 12 hours. After the set time, it was removed and allowed to cool naturally. Finally, the in-situ grown MOF catalyst iron foam electrode was cleaned with a DMF to methanol volume ratio of 1:2 for 5 minutes and dried at 60°C for 5 minutes.

[0055] Example 8

[0056] 29.1 mg Co(NO3)2·6H2O was added to a 5 mL DMF and methanol mixture and magnetically stirred for 20 minutes at room temperature, with a DMF to methanol volume ratio of 1:2. Then, 12.4 mg H6TDPAT was added to the same 5 mL DMF and methanol mixture and magnetically stirred for 120 minutes at room temperature, again with a DMF to methanol volume ratio of 1:2. The mixture was then stirred and poured into a 20 mL PTFE reactor liner. The titanium mesh was cleaned by sonicating it in acetone for 5 minutes, then in ethanol for 5 minutes, followed by sonicating it in 0.1 mol / L hydrochloric acid for 5 minutes. It was then rinsed with deionized water for 3 minutes and rapidly dried with nitrogen. The mesh was then placed in the reactor liner as a growth substrate, sealed, and placed in an oven heated to 160°C for 12 hours. After the set time, it was removed and allowed to cool naturally. Finally, the in-situ grown MOF catalyst foam electrode was cleaned with a DMF to methanol volume ratio of 1:2 for 3 minutes and dried at 60°C for 5 minutes.

[0057] Performance Test 1

[0058] Blank iron foam without MOF growth, and the granular nanoarray and two-dimensional sheet nanoarray MOF catalytic electrodes prepared in Examples 1 and 3 above were used as working electrodes, named "iron foam," "iron foam + MOF (DMF)," and "iron foam + MOF (DMF + methanol)," respectively. A platinum sheet was used as the counter electrode, and a mercury / mercury oxide electrode was used as the reference electrode. The electrolyte was a 1 mol / L potassium hydroxide (KOH) solution. Tests were conducted in a three-electrode system at a scan rate of 5 mV / s, while the full water electrolysis performance test was conducted in a two-electrode system. Linear scanning voltammetry, current density-time curves, and other related electrochemical performance tests were performed at room temperature.

[0059] The performance test results are as follows:

[0060] Test results show that "foamed iron", "foamed iron + MOF(DMF)" and "foamed iron + MOF(DMF + methanol)" react at an oxygen evolution reaction current density of 10 mA / cm². 2 The overpotentials were 362 mV, 241 mV, and 221 mV, respectively, at a hydrogen evolution reaction current density of -10 mA / cm². 2 The overpotentials were 323 mV, 237 mV, and 211 mV, respectively, confirming that the MOF catalytic electrode possesses high oxygen evolution and hydrogen evolution performance. Furthermore, the two-dimensional sheet-like nanoarray MOF catalytic electrode prepared with DMF:methanol = 1:2 solvent exhibits even higher oxygen evolution and hydrogen evolution performance due to its larger specific surface area and higher electron transport capacity. The full electrolysis performance test results under the two-electrode system show that the foamed iron + MOF (DMF + methanol) achieves 10 mA / cm² at 1.697 V. 2 It has a high current density and good stability over 18 hours.

[0061] Figure 1 Field emission scanning electron microscope (FESEM) images of MOF catalytic electrodes prepared by in-situ growth at 160°C for 24 hours on a foamed iron substrate. (a) shows the particulate nanoarray MOF catalytic electrode obtained in Example 1 when the solvent was only DMF. At this time, the nanoparticles were small and dense. When methanol was added to a DMF:methanol volume ratio of 1:1 (Example 2), the nanoparticles gradually increased in size and began to connect with each other, thus obtaining a nanoarray MOF catalytic electrode with interconnected particles (b). With the continued increase of methanol solvent, the nanoparticles gradually transformed into a two-dimensional nanosheet structure, i.e., the two-dimensional sheet-like nanoarray MOF catalytic electrode obtained in Example 3 when DMF:methanol = 1:2 (c). When DMF:methanol = 1:4 (Example 4), the nanosheet structure collapsed and connected to form a thin film, thus obtaining a thin film MOF catalytic electrode (d).

[0062] Figure 2This is a high-resolution transmission electron microscope (TEM) image of the two-dimensional sheet-like nanoarray MOF catalytic electrode in Example 3. The image shows that some regions exhibit a clear lattice structure, but the overall lattice distribution is not long-range ordered. Therefore, it can be determined that the fabricated MOF catalytic electrode has a low degree of crystallinity.

[0063] Figure 3 (a) and (b) are the linear sweep voltammetric curves of oxygen evolution and hydrogen evolution of blank foamed iron (foamed iron) without MOF growth, and the particulate nanoarray and two-dimensional sheet nanoarray MOF catalytic electrodes prepared in Example 1 (foamed iron + MOF(DMF)) and Example 3 (foamed iron + MOF(DMF + methanol)) respectively. The oxygen evolution reaction current density of foamed iron + MOF(DMF) and foamed iron + MOF(DMF + methanol) is 10 mA / cm². 2 The overpotentials were 241 mV and 221 mV, respectively, at a hydrogen evolution reaction current density of -10 mA / cm². 2 The overpotentials were 237 mV and 211 mV, respectively, which were significantly lower than the 362 mV (oxygen evolution) and 323 mV (hydrogen evolution) of the blank foamed iron. These results indicate that the catalytic performance of this catalyst is superior to most similar non-noble metal catalysts and also superior to the Ru / Ir catalyst. Therefore, this MOF catalytic electrode has high oxygen evolution and hydrogen evolution performance. Moreover, the two-dimensional sheet-like nanoarray MOF catalytic electrode exhibits even higher oxygen evolution and hydrogen evolution performance due to its larger specific surface area and higher electron transport capacity. (c) shows the full electrolysis performance of the above electrodes in a two-electrode system. The results show that the two-dimensional sheet-like nanoarray MOF catalytic electrode has the best performance, reaching 10 mA / cm² at 1.697 V. 2 The current density is shown in (d). The current density-time diagram of the two-dimensional sheet-like nanoarray MOF catalytic electrode in the two-electrode system is shown. After continuous testing at a voltage of 1.697V for 18 hours, the current density did not decrease, which confirms that it has good stability.

[0064] Therefore, this invention achieves a morphology-tunable cobalt-based MOF catalytic electrode by combining cobalt ions with the novel organic ligand H6TDPAT and adjusting the solvent ratio. This catalytic electrode exhibits excellent oxygen and hydrogen evolution performance in alkaline water electrolysis tests while maintaining high stability. Thus, this simple, efficient, stable, and inexpensive MOF catalytic electrode has broad application prospects in the field of alkaline water electrolysis.

[0065] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a morphology-tunable cobalt-based MOF catalytic electrode, characterized in that, Includes the following steps: Divalent cobalt ions were added to a mixed solvent of N,N-dimethylformamide (DMF) and methanol and magnetically stirred for 10-30 minutes to obtain a cobalt ion solution. The divalent cobalt ion is cobalt nitrate hexahydrate Co(NO3)2•6H2O, and the ratio of Co(NO3)2•6H2O to the mixed solvent in the cobalt ion solution is 29.1 mg: 2~20 mL; The organic ligand is then added to a mixed solvent of DMF and methanol and magnetically stirred for 30-120 minutes to obtain an organic ligand solution. The DMF and methanol mixed solvent is DMF and methanol in different volume ratios, with the volume ratio ranging from DMF:methanol = 1:0.01 to 1:

4. The organic ligand is 2,4,6,-tris(3,5-dicarboxyphenylamino)-1,3,5-triazine H6TDPAT, and the ratio of H6TDPAT to the mixed solvent in the organic ligand solution is 12.4 mg: 2~20 mL. Then, the cobalt ion solution and the organic ligand solution are mixed and stirred and poured into the inner liner of the reactor. The cleaned growth substrate, which is iron foam, is then placed in the reactor. The reactor is sealed and placed in an oven for heating. After the set time is reached, the reactor is removed and allowed to cool naturally. Finally, the reactor is cleaned and dried to obtain a cobalt-based MOF catalytic electrode with tunable morphology.

2. The method for preparing a morphology-tunable cobalt-based MOF catalytic electrode according to claim 1, characterized in that, The cleaned growth substrate was obtained using the following steps: First, sonicate in acetone for 5-15 minutes, then sonicate in ethanol for 5-15 minutes, then sonicate in 0.1-1 mol / L hydrochloric acid for 5-15 minutes, then rinse with deionized water for 3-10 minutes, and finally dry quickly with nitrogen to obtain the cleaned growth substrate.

3. The method for preparing a morphology-tunable cobalt-based MOF catalytic electrode according to claim 1, characterized in that, The conditions for sealing and heating in an oven are: solvent heating temperature of 80~180°C, and time set from 20 minutes to 72 hours.

4. The method for preparing a morphology-tunable cobalt-based MOF catalytic electrode according to claim 1, characterized in that, Cleaning and drying specifically include: Rinse with a mixture of DMF and methanol for 3-5 minutes, then dry in a forced-air drying oven at 50-70°C for 5-10 minutes.

5. A morphology-tunable cobalt-based MOF catalytic electrode prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the morphology-tunable cobalt-based MOF catalytic electrode according to claim 5 in the catalysis of oxygen evolution and hydrogen evolution in water electrolysis under alkaline conditions.

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