Cluster type self-healing hydroxyl nickel iron oxide / nickel electrode and application thereof in hydrogen production by saline-alkali water splitting

Abstract

The invention discloses a cluster type self-healing hydroxyl nickel iron oxide / nickel electrode and application thereof in hydrogen production by saline-alkali water splitting, and the method comprises the following steps: under a three-electrode system, taking foam metal as a working electrode, and obtaining a metal cluster dispersion liquid in a potassium hydroxide solution electrolyte by adopting a cyclic voltammetry method; under a three-electrode system, taking ferronickel / nickel MOF as a working electrode, taking metal cluster dispersion liquid as electrolyte, and adopting cyclic voltammetry to obtain a target electrode; in an electrolyte formed by mixing a metal cluster dispersion liquid and saline-alkali water, the target electrode is used for saline-alkali water splitting hydrogen production or saline-alkali water splitting complete reaction. The target electrode has high activity and durability and good self-healing performance in saline-alkali water and under industrial large current density (500 mA cm <-2 >).

Description

Technical Field

[0001] The present invention relates to a cluster-type self-healing nickel iron oxyhydroxide / nickel electrode and its application in saline-alkali water electrolysis for hydrogen production, belonging to the technical field of electrolytic water electrodes. Background Art

[0002] Hydrolysis of water for hydrogen production is a clean and green production method. However, the anodic oxygen evolution reaction and the cathodic hydrogen evolution reaction have serious thermodynamic delays, which restrict the activity, stability and energy efficiency of electrolytic water. To improve this unfavorable situation, highly active noble metal catalysts (such as iridium oxide, platinum, etc.) are commercially used for electrolytic water hydrogen production. However, their rarity in reserves and high prices severely restrict the wide application of noble metal catalysts. In addition, most of the above materials require the use of fresh water or purified water as the electrolyte, which exacerbates the consumption of rare fresh water resources and additional investment costs.

[0003] In contrast, a large amount of low-quality water is widely distributed on the earth, such as seawater, inland saline-alkali water, etc. If the synthesized electrode can be directly used or the low-quality water can be simply treated for electrolytic water hydrogen production, it is crucial for the sustainable utilization of clean energy and environmental protection. For this reason, relevant scholars have done some research on seawater and put forward several common guiding principles. However, there are still controversies in the research on other low-quality waters by the above methods. It is necessary to further develop electrodes with high activity, durability and economy, conduct in-depth research on the electrolytic water hydrogen production of other low-quality waters, and promote the high-value utilization of other low-quality waters.

[0004] Self-healing electrocatalysts can automatically repair at the damaged position through special structural design or composition methods, restoring their electrocatalytic activity, and are expected to become potential materials to solve the above problems. At present, common self-healing catalytic electrodes are mainly based on metal ions, such as Ni 2+ , Co 2+ and buffer solutions composed of phosphate, carbonate or borate, which have certain limitations in system design. Summary of the Invention

[0005] The purpose of the present invention is to provide a cluster-type self-healing nickel iron oxyhydroxide / nickel electrode and its preparation method, which has stable hydrogen production performance in saline-alkali water.

[0006] The technical solution to achieve the purpose of the present invention is as follows:

[0007] The cluster-type self-healing nickel iron oxyhydroxide / nickel electrode and its preparation method of the present invention include the following steps:

[0008] Step 1: In a three - electrode electrochemical system, using a foam metal as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, and an alkaline solution as the electrolyte, at a certain stirring rate, at the oxygen evolution reaction potential, cyclic voltammetry is used to obtain a metal cluster dispersion;

[0009] Step 2: In a three - electrode electrochemical system, using a nickel metal - organic framework or a nickel - iron metal - organic framework as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, and using the metal cluster dispersion obtained in Step 1 as the electrolyte, at a certain stirring rate, at the oxygen evolution reaction potential, cyclic voltammetry is used to obtain a cluster - type self - healing nickel - iron oxyhydroxide / nickel electrode.

[0010] Furthermore, the nickel - iron metal - organic framework is obtained by dissolving 2 - thiophenecarboxylic acid, nickel acetate, and iron nitrate in ethanol, and then reacting with a nickel foam substrate in a sealed environment at 150 ± 10 °C for 0.5 - 16 h. Among them, by mass ratio, iron nitrate:(iron nitrate + nickel acetate)=0.05 - 0.20; the nickel metal - organic framework is obtained by dissolving 2 - thiophenecarboxylic acid and nickel acetate in ethanol, and then reacting with a nickel foam substrate in a sealed environment at 150 ± 10 °C for 12 h.

[0011] Furthermore, in Step 1, the alkaline solution is a KOH solution or an NaOH solution with a concentration of 1 - 6 mol / L, preferably 4 - 6 mol / L. The foam metal is foam nickel, foam iron, or foam nickel - iron. The cyclic voltammetry potential is 1.3 - 2.0 V (vs RHE), the number of cyclic voltammetry scans is 20 - 200, and the stirring rate is 500 - 800 r / min.

[0012] Furthermore, in Step 2, the cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the number of cyclic voltammetry scans is 20 - 200, and the stirring rate is 500 - 800 r / min.

[0013] The present invention also provides the use of the above - mentioned cluster - type self - healing nickel - iron oxyhydroxide / nickel electrode. The specific steps are as follows: In a three - electrode electrochemical system, the above - mentioned metal cluster dispersion is mixed with the saline - alkaline water to be decomposed and used as the electrolyte. Using the cluster nickel - iron oxyhydroxide / nickel electrode as the working electrode, Hg / HgO as the reference electrode, and a carbon material or a noble metal material as the counter electrode, an oxygen evolution reaction of saline - alkaline water is carried out.

[0014] Furthermore, the linear sweep voltammetry potential of the oxygen evolution reaction of saline - alkaline water is 1.0 - 1.8 V (vs RHE), the stirring rate is 500 r / min, and the iR compensation is 85%.

[0015] Furthermore, the volume ratio of the metal cluster dispersion to the saline - alkaline water is 10% - 90%, preferably 50% - 90%.

[0016] The present invention also provides the use of the above cluster-type self-healing nickel iron oxyhydroxide / nickel electrode, and the specific steps are as follows: in a two-electrode electrochemical system, the above metal cluster dispersion is mixed with the saline-alkali water to be decomposed as the electrolyte, and the cluster nickel iron oxyhydroxide / nickel electrode is used as the anode, and the platinum-carbon electrode is used as the cathode to carry out the complete reaction of saline-alkali water cracking.

[0017] Further, the linear sweep voltammetry potential of the complete reaction of saline-alkali water cracking is 1.0 - 2.0 V, the stirring rate is 500 r / min, and the iR compensation is 85%.

[0018] Compared with the prior art, the present invention has the following advantages: (1) The three-electrode cyclic voltammetry is used to synthesize the metal cluster dispersion and the cluster-type nickel iron oxyhydroxide / nickel electrode, and the preparation method is simple and can be mass-produced industrially; (2) The cluster-type nickel iron oxyhydroxide / nickel electrode has a hierarchical porous honeycomb structure, the combination between the substrate and the active substance is firm, and a rich active site is provided, which is beneficial to the rapid transfer of electrons and protons and the transport of reaction products; (3) Using saline-alkali water as the electrolyte is beneficial to the high-value utilization of low-quality water; (4) The cluster-type nickel iron oxyhydroxide / nickel electrode material has high activity, persistence and good self-healing performance in saline-alkali water and under industrial large current density (500 mA cm -2 ). Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the synthesis of the cluster-type self-healing nickel iron oxyhydroxide electrode and the process of oxygen evolution reaction in saline-alkali water of the present invention.

[0020] Figure 2 It is the SEM images (a - d) of different magnifications of Ni-MOF in Example 1 of the present invention and its element distribution maps (C, O, S, Ni).

[0021] Figure 3 It is the SEM images (a - c) of different magnifications of NiFe-MOF-5%Fe in Example 2 of the present invention and its element distribution maps (C, O, S, Ni, Fe).

[0022] Figure 4 It is the SEM images (a - c) of different magnifications of NiFe-MOF obtained at a reaction time of 12 h in Example 3 of the present invention and its element distribution maps (C, O, S, Ni, Fe).

[0023] Figure 5 It is the SEM images (a - c) of different magnifications of NiFe-MOF-15%Fe in Example 4 of the present invention and its element distribution maps (C, O, S, Ni, Fe).

[0024] Figure 6SEM images (a-c) of NiFe-MOF-20% Fe at different magnifications and its elemental distribution maps (C, O, S, Ni, Fe) of Example 5 of the present invention.

[0025] Figure 7 SEM images (a-l) of electrodes obtained at different reaction times in Example 3 of the present invention at different magnifications.

[0026] Figure 8 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of MOFs of Examples 1-5 of the present invention and commercial electrodes.

[0027] Figure 9 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of cluster-type nickel iron oxyhydroxide electrodes of Examples 6-9 of the present invention.

[0028] Figure 10 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type nickel iron oxyhydroxide electrode of Example 10 of the present invention in NC / KOH dispersion liquids with different concentrations.

[0029] Figure 11 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type nickel iron oxyhydroxide electrode of Example 11 of the present invention at different potentials.

[0030] Figure 12 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type self-healing nickel iron oxyhydroxide electrode of Example 12 of the present invention at different cyclic voltammetry times.

[0031] Figure 13 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type self-healing nickel iron oxyhydroxide electrode of Example 13 of the present invention at different stirring rates.

[0032] Figure 14 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type nickel iron oxyhydroxide electrode of Example 14 of the present invention in a mixed electrolyte of NC / KOH dispersion liquid with different concentrations and saline-alkali water.

[0033] Figure 15 Linear sweep voltammograms (a: forward sweep, b: reverse sweep) of oxygen evolution reactions of the cluster-type nickel iron oxyhydroxide electrode of Example 15 of the present invention in a mixed electrolyte of NC / KOH dispersion liquid with different volumes and saline-alkali water.

[0034] Figure 16are the Faraday efficiency (a), Tafel slope (b), electrochemically active area (c), AC impedance (d), linear sweep voltammetry curves (e: different electrodes, f: different stirring rates, different cyclic voltammetry times), segmented E-t diagrams (g), and chronopotentiometry diagrams (h) of the oxygen evolution reaction of the electrodes in Examples 6-9 and 14 of the present invention.

[0035] Figure 17 are NiFe-MOF obtained under a reaction time of 12 h in Example 3 of the present invention and NC / Ni in Example 6 x Fe y XRD spectra (a), FTIR spectra (b), Raman spectra (c-d), and high-resolution XPS spectra (e-f) of

[0036] Figure 18 is NC / Ni in Example 6 of the present invention x Fe y SEM images of different magnifications (a-c) of

[0037] Figure 19 is NC / Ni in Example 6 of the present invention x Fe y TEM images of different magnifications (a-e) of

[0038] Figure 20 are the electrochemical performances of the overall saline-alkali water splitting reaction in Example 16 of the present invention (a: linear sweep voltammetry, b: chronopotentiometry, c: gas collection device, d: Faraday efficiency). Detailed implementation manners

[0039] Hydrogen production by water splitting is a clean and green production method. However, the oxygen evolution reaction in water splitting is thermodynamically slow, which restricts the activity, stability, and energy efficiency of water electrolysis. The noble metal catalysts used commercially are severely restricted in their widespread application due to their rarity and high price. In addition, most of the above materials require the use of fresh water or purified water as the electrolyte, which exacerbates the consumption of rare fresh water resources and additional investment costs. There is a large amount of low-quality water widely distributed on the earth, such as seawater, salt lake brine, and saline-alkali water. If the synthesized electrode can be directly used or the low-quality water can be simply treated for hydrogen production by water electrolysis, it is crucial for the sustainable utilization of clean energy and environmental protection. Self-healing electrocatalysts can automatically repair at damaged positions through special structural designs or composition methods and restore their electrocatalytic activity, and are expected to become potential materials to solve the above problems. Currently, common self-healing catalytic electrodes are mainly based on metal ions, such as Ni 2+ 、Co 2+Buffers composed of phosphate, carbonate, or borate have certain limitations in system design. On this basis, we innovatively propose a cluster hydroxy oxide nickel-iron self-supporting electrode for oxygen evolution reaction and water splitting hydrogen production reaction in saline-alkali water, which has a hierarchical porous honeycomb structure composed of one-dimensional nanoribbons. There is a strong binding force between the hydroxy oxide nickel-iron and the substrate, providing a large number of exposed active sites, which is conducive to the rapid transfer of electrons and protons and the rapid transport of reaction products, having high activity and persistence, and showing good self-healing performance.

[0040] Combined with Figure 1 , taking the nickel-iron electrode as an example, the present invention provides a preparation method of a cluster-type self-healing nickel-iron hydroxy oxide electrode and its use in the oxygen evolution reaction in saline-alkali water, including the following steps:

[0041] Step 1: Dissolve 2-thiophenecarboxylic acid, nickel acetate, and iron nitrate in ethanol, and then heat and react with a nickel foam substrate in a closed environment for a period of time to obtain a nickel-iron metal-organic framework;

[0042] Step 2: In a three-electrode electrochemical system, using nickel foam as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, and a potassium hydroxide (KOH) solution as the electrolyte, at the oxygen evolution reaction potential, use cyclic voltammetry to obtain a dispersion of nickel metal clusters;

[0043] Step 3: In a three-electrode electrochemical system, using the nickel-iron metal-organic framework synthesized in Step 1 as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, and using the nickel metal cluster dispersion obtained in Step 2 as the electrolyte, use cyclic voltammetry to obtain a nickel metal cluster nickel-iron hydroxy oxide electrode with self-healing properties;

[0044] Step 4: In a three-electrode electrochemical system, mix the nickel metal cluster dispersion in Step 2 with saline-alkali water as the electrolyte, using the nickel metal cluster nickel-iron hydroxy oxide electrode obtained in Step 3 as the working electrode, Hg / HgO as the reference electrode, and a carbon material or a noble metal material as the counter electrode, and perform an anodic oxygen evolution reaction to obtain excellent electrocatalytic performance.

[0045] The present invention is illustrated by the following examples, but the examples are only used for illustration and cannot be regarded as a limitation on the scope of the invention or the application method of the invention. Unless otherwise specified, the raw materials nickel foam, iron foam, nickel-iron foam, and IrO2 of the present invention are all commercially available.

[0046] Example 1:

[0047] Step 1: Dissolve 0.6 g of nickel acetate and 0.6 g of 2-thiophenecarboxylic acid in ethanol, and stir well to form a uniform mixed solution;

[0048] Step 2: Place the mixed solution obtained in Step 1 and the nickel foam substrate (named NF) in a sealed environment and heat-react at 150 °C for 12 h;

[0049] Step 3: Wash and dry the product obtained in Step 2 to obtain nickel metal-organic framework (named Ni-MOF). Its SEM and elemental distribution maps are as Figure 2 shown.

[0050] Step 4: In a three-electrode electrochemical system, use the Ni-MOF in Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH solution as the electrolyte and perform mechanical stirring. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 5 mV / s, and a linear sweep voltammetry test is carried out to obtain the linear sweep voltammogram of Ni-MOF in 1 mol / L KOH electrolyte, as Figure 8 shown.

[0051] Example 2:

[0052] Step 1: Dissolve 0.57 g of nickel acetate, 0.03 g of iron nitrate and 0.6 g of 2-thiophenecarboxylic acid in ethanol and stir well to form a homogeneous mixed solution;

[0053] Step 2: Place the mixed solution obtained in Step 1 and the nickel foam substrate in a sealed environment and heat-react at 150 °C for 12 h;

[0054] Step 3: Wash and dry the product obtained in Step 2 to obtain nickel-iron metal-organic framework (named NiFe-MOF-5%Fe). Its SEM and elemental distribution maps are as Figure 3 shown.

[0055] Step 4: In a three-electrode electrochemical system, use the NiFe-MOF-5%Fe in Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH solution as the electrolyte and perform mechanical stirring. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 5 mV / s, and a linear sweep voltammetry test is carried out to obtain the linear sweep voltammogram of NiFe-MOF-5%Fe in 1 mol / L KOH electrolyte, as Figure 8 shown.

[0056] Example 3:

[0057] Step 1: Dissolve 0.54 g of nickel acetate, 0.06 g of iron nitrate and 0.6 g of 2-thiophenecarboxylic acid in ethanol and stir well to form a homogeneous mixed solution;

[0058] Step 2: Place the mixed solution obtained in Step 1 and the nickel foam substrate together in a sealed environment and heat at 150 °C for 12 h;

[0059] Step 3: Wash and dry the product obtained in Step 2 to obtain nickel-iron metal-organic framework (named NiFe-MOF). Its SEM and element distribution maps are as Figure 4 shown, and XRD, FTIR, and Raman are as Figure 17 shown.

[0060] In addition, with other process parameters and steps unchanged, the heating times are changed successively to: 0.5 h, 2 h, 4 h, 8 h, and 16 h. The SEM of the nickel-iron metal-organic frameworks obtained at different reaction times is as Figure 7 shown. Step 4: In a three-electrode electrochemical system, use the NiFe-MOF (heating time is 12 h) obtained in Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH solution as the electrolyte and perform mechanical stirring. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), and the scanning rate is 5 mV / s. Perform linear sweep voltammetry testing to obtain the linear sweep voltammogram of NiFe-MOF in 1 mol / L KOH electrolyte, as Figure 8 shown.

[0061] Example 4:

[0062] Step 1: Dissolve 0.51 g of nickel acetate, 0.09 g of iron nitrate, and 0.6 g of 2-thiophenecarboxylic acid in ethanol, and stir well to form a homogeneous mixed solution;

[0063] Step 2: Place the mixed solution obtained in Step 1 and the nickel foam substrate together in a sealed environment and heat at 150 °C for 12 h;

[0064] Step 3: Wash and dry the product obtained in Step 2 to obtain a precursor of nickel iron oxyhydroxide, namely nickel-iron metal-organic framework (named NiFe-MOF-15%Fe). Its SEM and element distribution maps are as Figure 5 shown.

[0065] Step 4: In a three-electrode electrochemical system, use NiFe-MOF-15%Fe in Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH solution as the electrolyte and perform mechanical stirring. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), and the scanning rate is 5 mV / s. Perform linear sweep voltammetry testing to obtain the linear sweep voltammogram of NiFe-MOF-15%Fe in 1 mol / L KOH electrolyte, as Figure 8 shown.

[0066] Example 5:

[0067] Step 1: Dissolve 0.48 g of nickel acetate, 0.12 g of iron nitrate and 0.6 g of 2-thiophenecarboxylic acid in an ethanol solution, and stir well to form a homogeneous mixed solution;

[0068] Step 2: Place the mixed solution obtained in Step 1 and the nickel foam substrate in a closed environment and heat-react at 150 °C for 12 h;

[0069] Step 3: Wash and dry the product obtained in Step 2 to obtain a precursor of nickel iron oxyhydroxide, namely nickel iron metal-organic framework (named NiFe-MOF-20%Fe). The SEM and its elemental distribution maps are as Figure 6 shown.

[0070] Step 4: In a three-electrode electrochemical system, use NiFe-MOF-20%Fe in Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH solution as the electrolyte and conduct mechanical stirring. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 5 mV / s, and perform a linear sweep voltammetry test to obtain the linear sweep voltammogram of NiFe-MOF-20%Fe in 1 mol / L KOH electrolyte, as Figure 8 shown.

[0071] Example 6:

[0072] Step 1: Fabricate 1 piece of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, prepare 1 mol / L KOH electrolyte, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8 - 2.0 V (vs RHE), the scanning rate is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min to obtain a dispersion of nickel clusters (named NC / KOH);

[0073] Step 2: Use the NC / KOH dispersion obtained in Step 1 as the electrolyte, use the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode. The cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min to obtain nickel cluster nickel iron oxyhydroxide (named NC / Ni x Fe y OOH). The XRD, FTIR, Raman, and XPS are as Figure 17 shown, and the SEM and TEM are respectively as Figure 18 and 19 shown;

[0074] Step 3: In a three-electrode electrochemical system, use the NC / KOH solution obtained in Step 1 as the electrolyte, and use the NC / Ni x Fe y OOH as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed is 500 r / min, Hg / HgO as the reference electrode, the oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 5 mV / s, and the current density for Faraday efficiency test is 100 mA cm -2 , perform linear sweep voltammetry characteristics and Faraday efficiency tests, so as to obtain NC / Ni x Fe y OOH's linear sweep voltammogram and Faraday efficiency in the NC / KOH dispersion, as shown in Figure 9 and Figure 16 a shown in.

[0075] Example 7:

[0076] Step 1: Fabricate 1 piece of foam iron with a size of 1 cm × 1 cm × 1.6 mm (named Fe) as the working electrode, prepare a 4 mol / L KOH electrolyte, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry reaction potential is 1.8 - 2.0 V (vs RHE), the scanning speed is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, so as to obtain a dispersion of iron clusters (named Fe / KOH);

[0077] Step 2: Use the Fe / KOH dispersion obtained in Step 1 as the electrolyte, use the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, so as to obtain iron cluster nickel iron oxyhydroxide (named Fe / Ni x Fe y OOH);

[0078] Step 3: Use the Fe / KOH solution obtained in Step 1 as the electrolyte, use the Fe / Ni x Fe y OOH as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed is 500 r / min, Hg / HgO as the reference electrode, the oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 5 mV / s, and the current density for Faraday efficiency test is 100 mA cm -2 , perform linear sweep voltammetry characteristics and Faraday efficiency tests, so as to obtain Fe / Nix Fe y The linear sweep voltammetry curve and Faraday efficiency of FeOOH in the Fe / KOH dispersion are shown in a of Figure 9 and Figure 16 respectively.

[0079] Example 8:

[0080] Step 1: Fabricate 1 piece of nickel foam iron with a size of 1 cm × 1 cm × 1.6 mm (named Ni 0.5 Fe 0.5 ) as the working electrode, prepare 1 mol / L KOH electrolyte solution, use a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry reaction potential is 1.8 - 2.0 V (vs RHE), the scanning speed is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, so as to obtain a dispersion of nickel-iron clusters (named Ni 0.5 Fe 0.5 / KOH);

[0081] Step 2: Use the Ni 0.5 Fe 0.5 / KOH dispersion obtained in Step 1 as the electrolyte, use the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9 - 1.7 V (vsRHE), the scanning speed is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, so as to obtain nickel-iron cluster nickel iron oxyhydroxide (named Ni 0.5 Fe 0.5 / Ni x Fe y OOH);

[0082] Step 3: Use the Ni 0.5 Fe 0.5 / KOH solution obtained in Step 1 as the electrolyte, use the Ni 0.5 Fe 0.5 / Ni x Fe y OOH obtained in Step 2 as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed is 500 r / min, Hg / HgO as the reference electrode, the oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 5 mV / s, and the Faraday efficiency test current density is 100 mAcm -2 , conduct linear sweep voltammetry characteristics and Faraday efficiency tests, so as to obtain Ni 0.5 Fe 0.5 / Ni x Fe y OOH in Ni 0.5Fe 0.5 Linear sweep voltammograms in the / KOH dispersion are shown respectively as Figure 9 follows.

[0083] Example 9:

[0084] Step 1: Using the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, a 4 mol / L KOH solution as the electrolyte, the cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 100 mV / s, the cyclic scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, thereby obtaining nickel-iron oxyhydroxide (named Ni x Fe y OOH);

[0085] Step 2: Using a 4 mol / L KOH solution as the electrolyte, with the Ni x Fe y OOH obtained in Step 1 as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed is 500 r / min, Hg / HgO as the reference electrode, the oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), and the scanning rate is 5 mV / s, to perform a linear sweep voltammetry characteristic test, thereby obtaining the linear sweep voltammogram of Ni x Fe y OOH in a 4 mol / L KOH dispersion, as shown in Figure 9 the following figure.

[0086] Example 10:

[0087] Step 1: Prepare 3 pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, respectively prepare 1, 4, and 6 mol / L KOH electrolytes, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry potential is 1.8 - 2.0 V (vs RHE), the scanning rate is 100 mV / s, the scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, thereby obtaining dispersions of nickel clusters (named NC / 1M KOH, NC / 4M KOH, NC / 6M KOH);

[0088] Step 2: Using the NC / 1M KOH, NC / 4M KOH, and NC / 6M KOH solutions obtained in Step 1 as the electrolytes, with the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9 - 1.7 V vs RHE, the scanning rate is 100 mV / s, the scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, thereby obtaining nickel cluster nickel-iron oxyhydroxide (named NC / Ni x Fey OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-6);

[0089] Step 3: Using the NC / 1M KOH, NC / 4M KOH, and NC / 6M KOH dispersions obtained in Step 1 as electrolytes, with the NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-6 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, perform linear sweep voltammetry tests. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scan rate is 5 mV / s, the electrolyte rotation speed is 500 r / min, so as to obtain the linear sweep voltammograms of NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-6 in NC / 1M KOH, NC / 4M KOH, and NC / 6M KOH electrolytes, as shown in Figure 10 shown.

[0090] Example 11:

[0091] Step 1: Fabricate 2 pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, prepare a 4 mol / L KOH electrolyte, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Activate the nickel foam iron by cyclic voltammetry. The oxygen evolution reaction potentials are 1.3 - 1.8 V (vs RHE) and 1.8 - 2.0 V (vs RHE) respectively, the scan rate is 100 mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500 r / min, so as to obtain the dispersions of nickel clusters (named NC / 4M KOH-1.3 and NC / 4M KOH-2.0);

[0092] Step 2: Using the NC / 4M KOH-1.3 and NC / 4M KOH-2.0 solutions obtained in Step 1 as electrolytes, with the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 100 mV / s, the scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min, thereby obtaining nickel cluster nickel iron oxyhydroxide (named NC / Ni x Fe y OOH-1.3, NC / Ni x Fe y OOH-2.0);

[0093] Step 3: Using the NC / 4M KOH-1.3 and NC / 4M KOH-2.0 solutions obtained in Step 1 as electrolytes, and using the NC / Ni x Fe y OOH-1.3 and NC / Ni x Fe y OOH-2.0 obtained in Step 2 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, perform linear sweep voltammetry curve testing. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 5 mV / s, and the electrolyte rotation speed is 500 r / min, thereby obtaining the linear sweep voltammetry curves of NC / Ni x Fe y OOH-1.3 and NC / Ni x Fe y OOH-2.0 in the NC / 4M KOH-1.3 and NC / 4M KOH-2.0 electrolytes, as shown Figure 11 as follows.

[0094] Example 12:

[0095] Step 1: Fabricate 3 pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, prepare a 4 mol / L KOH electrolyte, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8 - 2.0 V vs RHE, the scanning rate is 100 mV / s, and the scanning times are 20, 100, and 200 cycles respectively, and the electrolyte rotation speed is 500 r / min, thereby obtaining a dispersion of nickel clusters (named NC / 4M KOH-20, NC / 4M KOH-100, NC / 4M KOH-200);

[0096] Step 2: Use the NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200 solutions obtained in Step 1 as the electrolyte, the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 100 mV / s, the scanning time is 100 cycles, and the electrolyte rotation speed is 500 r / min to obtain nickel cluster nickel iron oxyhydroxide (named NC / Ni x Fe y OOH-20, NC / Ni x Fe y OOH-100, NC / Ni x Fe y OOH-200);

[0097] Step 3: Use the NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200 solutions obtained in Step 1 as the electrolyte, and the NC / Ni x Fe y OOH-20, NC / Ni x Fe y OOH-100, NC / Ni x Fe y OOH-200 obtained in Step 2 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode to perform linear sweep voltammetry curve testing. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 5 mV / s, and the electrolyte rotation speed is 500 r / min to obtain the linear sweep voltammetry curves of NC / Ni x Fe y OOH-20, NC / Ni x Fe y OOH-100, NC / Ni x Fe y OOH-200 in NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200 electrolytes, as shown in Figure 12 shown.

[0098] Example 13:

[0099] Step 1: Fabricate 3 pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, prepare 4 mol / L KOH electrolyte solution, use a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8 - 2.0 V (vs RHE), the scanning rate is 100 mV / s, the scanning time is 100 cycles, and the rotation speed of the electrolyte is 500 r / min, so as to obtain a nickel cluster dispersion (named NC / 4M KOH);

[0100] Step 2: Use the NC / 4M KOH solution obtained in Step 1 as the electrolyte, take the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 100 mV / s, the scanning time is 100 cycles, and the rotation speed of the electrolyte is 500 r / min, so as to obtain nickel cluster nickel iron oxyhydroxide;

[0101] Step 3: Use the NC / 4M KOH solution obtained in Step 1 as the electrolyte, take the NC / Ni x Fe y OOH obtained in Step 2 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, and conduct linear sweep voltammetry curve tests. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning rate is 5 mV / s, and the rotation speeds of the electrolyte are 0, 500, and 800 r / min respectively, so as to obtain the linear sweep voltammetry curves of NC / Ni x Fe y OOH in NC / 4M KOH - 0, NC / 4M KOH - 500, and NC / 4M KOH - 800 electrolytes, as shown Figure 13 as follows

[0102] Example 14:

[0103] Step 1: Fabricate 6 pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm as the working electrode, prepare 1 - 6 mol / L KOH electrolyte solution, use a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8 - 2.0 V (vs RHE), the scanning rate is 100 mV / s, the scanning times are 100 cycles respectively, and the rotation speed of the electrolyte is 500 r / min, so as to obtain nickel cluster dispersions (named NC / 1M KOH, NC / 2M KOH, NC / 3M KOH, NC / 4M KOH, NC / 5M KOH, NC / 6M KOH);

[0104] Step 2: Respectively use the NC / 1M KOH, NC / 2M KOH, NC / 3M KOH, NC / 4M KOH, NC / 5M KOH, and NC / 6M KOH solutions obtained in Step 1 as electrolytes, use the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 100 mV / s, the scanning time is 100 cycles, and the rotation speed of the electrolyte is 500 r / min respectively, so as to obtain nickel cluster nickel iron oxyhydroxide (named NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-2, NC / Ni x Fe y OOH-3, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-5, NC / Ni x Fe y OOH-6);

[0105] Step 3: Respectively mix the NC / 1M KOH, NC / 2M KOH, NC / 3M KOH, NC / 4M KOH, NC / 5M KOH, and NC / 6M KOH solutions obtained in Step 1 with saline-alkali water (SAW), and the mixing volume ratio is 1:1. Respectively use the 6 kinds of mixed solutions as electrolytes, use the NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-2, NC / Ni x Fe y OOH-3, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-5, NC / Ni x Fe y OOH-6 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The oxygen evolution reaction potential is 0.9 - 1.7 V (vs RHE), the scanning speed is 5 mV / s, the rotation speed of the electrolyte is 500 r / min respectively, conduct linear sweep voltammetry curve test, AC impedance test, Tafel slope simulation, segmented E-t (10 - 500 mA cm -2 ) test, and chronopotentiometry test (500 mA cm -2 ), so as to obtain NC / Nix Fe y OOH-1, NC / Ni x Fe y OOH-2, NC / Ni x Fe y OOH-3, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-5, NC / Ni x Fe y Linear sweep voltammograms of OOH-6 in electrolytes of NC / (1M KOH+SAW), NC / (2M KOH+SAW), NC / (3M KOH+SAW), NC / (4M KOH+SAW), NC / (5M KOH+SAW), NC / (6M KOH+SAW), as Figure 14 shown; Tafel slopes, electrochemically active areas, impedance values, segmented E-t diagrams and chronopotentiometry curves, as Figure 16 shown.

[0106] Example 15:

[0107] Step 1: Fabricate 6 pieces of nickel foam with a size of 1 cm×1 cm×1.6 mm as the working electrode, prepare a 4 mol / L KOH electrolyte, use a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, with a cyclic voltammetry potential of 1.8 - 2.0 V (vs RHE), a scanning rate of 100 mV / s, a scanning time of 100 cycles respectively, and an electrolyte rotation speed of 500 r / min, so as to obtain a dispersion of nickel clusters;

[0108] Step 2: Use the NC / 4M KOH solution obtained in Step 1 as the electrolyte, use the NiFe-MOF in Example 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, with a cyclic voltammetry potential of 0.9 - 1.7 V (vs RHE), a scanning rate of 100 mV / s, a scanning time of 100 cycles, and an electrolyte rotation speed of 500 r / min respectively, so as to obtain nickel cluster nickel iron oxyhydroxide;

[0109] Step 3: Mix the NC / 4M KOH solution obtained in Step 1 with saline water (SAW) respectively, with mixing volume ratios of 0%, 10%, 30%, 50%, 70%, 90% respectively. Use the 6 kinds of mixed solutions as electrolytes respectively, and use the NC / Ni in Step 2 x Fe yOOH was used as the working electrode, the graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode. The oxygen evolution reaction potential was 0.9 - 1.7 V (vs RHE), the scanning rate was 5 mV / s, and the electrolyte rotation speed was 500 r / min respectively. Linear sweep voltammetry tests were carried out to obtain NC / Ni x Fe y The linear sweep voltammetry curves of OOH in NC / (0% KOH + SAW), NC / (10% KOH + SAW), NC / (30% KOH + SAW), NC / (50% KOH + SAW), NC / (70% KOH + SAW), NC / (90% KOH + SAW) electrolytes are as Figure 15 shown.

[0110] Example 16:

[0111] Step 1: Six pieces of nickel foam with a size of 1 cm × 1 cm × 1.6 mm were made as the working electrode. A 4 mol / L KOH electrolyte was prepared. The graphite carbon rod was used as the counter electrode, and Hg / HgO was used as the reference electrode. The cyclic voltammetry potential was 1.8 - 2.0 V (vs RHE), the scanning rate was 100 mV / s, the scanning time was 100 cycles respectively, and the electrolyte rotation speed was 500 r / min to obtain a dispersion of nickel clusters.

[0112] Step 2: The NC / 4M KOH solution obtained in Step 1 was used as the electrolyte. The NiFe-MOF in Example 3 was used as the working electrode, the graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential was 0.9 - 1.7 V (vs RHE), the scanning rate was 100 mV / s, the scanning time was 100 cycles, and the electrolyte rotation speed was 500 r / min to obtain nickel cluster nickel iron oxyhydroxide.

[0113] Step 3: In a two-electrode electrochemical system, the NC / 4M KOH solution obtained in Step 1 was mixed with saline-alkali water at a volume ratio of 1:1 as the electrolyte. Using the NC / Ni x Fe y OOH electrode as the anode and the platinum-carbon electrode as the cathode, with an electrolyte rotation speed of 500 r / min, the total reaction potential for saline-alkali water cracking was 1.0 - 2.0 V, the scanning rate was 5 mV / s, and the current density for Faraday efficiency test was 100 mA cm -2 , and linear sweep voltammetry characteristics, Faraday efficiency and chronopotentiometry tests were carried out to obtain the linear sweep voltammetry curve, Faraday efficiency and stability of NC / Ni x Fe y OOH in the mixed electrolyte of NC / KOH dispersion and saline-alkali water, as Figure 20 shown.

[0114] Figure 2 SEM images and elemental distribution maps of 0 wt% Fe (i.e., Ni-MOF) in Example 1. Among them, as can be seen from Figure 2 (a-d) in it, the synthesized Ni-MOF has a hierarchical porous honeycomb structure composed of randomly distributed quasi-one-dimensional nanobelts, and the elements C, O, S, and Ni are evenly distributed without element segregation.

[0115] Figure 3 SEM images and elemental distribution maps of 5 wt% Fe (i.e., NiFe-MOF-5% Fe) in Example 2. Among them, as can be seen from Figure 3 (a-c) in it, the synthesized NiFe-MOF-5% Fe has a hierarchical porous honeycomb structure composed of randomly distributed quasi-one-dimensional nanobelts, and the elements C, O, S, Ni, and Fe are evenly distributed without element segregation.

[0116] Figure 4 SEM images and elemental distribution maps of 10 wt% Fe (i.e., NiFe-MOF) in Example 3. Among them, as can be seen from Figure 4 (a-c) in it, the synthesized NiFe-MOF has a hierarchical porous honeycomb structure composed of randomly distributed quasi-one-dimensional nanobelts, and the elements C, O, S, Ni, and Fe are evenly distributed without element segregation.

[0117] Figure 5 SEM images and elemental distribution maps of NiFe-MOF-15% Fe containing 15 wt% Fe in Example 4.

[0118] Among them, as can be seen from Figure 5 (a-c) in it, the synthesized NiFe-MOF-15% Fe has a hierarchical porous honeycomb structure composed of randomly distributed quasi-one-dimensional nanobelts, and the elements C, O, S, Ni, and Fe are evenly distributed without element segregation.

[0119] Figure 6 SEM images and elemental distribution maps of 20 wt% Fe (i.e., NiFe-MOF-20% Fe) in Example 5.

[0120] Among them, as can be seen from Figure 6 (a-c) in it, the synthesized NiFe-MOF-20% Fe has a hierarchical porous honeycomb structure composed of randomly distributed quasi-one-dimensional nanobelts, and the elements C, O, S, Ni, and Fe are evenly distributed without element segregation. Combining Examples 1-4, the MOFs with different iron contents synthesized by this method have consistent morphologies and uniform elemental distributions, showing good universality.

[0121] Figure 7SEM images of MOF electrodes with different growth times in Example 3. Among them, from (a - h) in Figure 7 , it can be seen that the morphology of the MOF electrode gradually nucleates and grows from the initial small particles into quasi - one - dimensional nanobelts and large particles with random distribution. From 12 h to 16 h, as shown in (i - l), the morphology of the MOF electrode is a honeycomb structure with hierarchical pores composed of single randomly distributed quasi - one - dimensional nanobelts, indicating that the growth of the MOF electrode is completed and the morphology no longer changes.

[0122] Figure 8 Linear sweep voltammograms of the oxygen evolution reaction of MOFs in Examples 1 - 5 and commercial electrodes IrO2, NF, NiFe - MOF - Bulk (prepared with reference to Mater. Chem. Front., 2023, 7, 5005). By comparing the linear sweep voltammograms of MOFs with different iron contents such as Ni - MOF, NiFe - MOF - 5%Fe, NiFe - MOF (reaction time 12 h, NiFe - MOF - 10%Fe), NiFe - MOF - 15%Fe, NiFe - MOF - 20%Fe, it can be seen that NiFe - MOF has the best oxygen evolution reaction activity, and subsequent cluster - type nickel iron oxyhydroxide electrodes are all synthesized with NiFe - MOF as the precursor.

[0123] Next, the effects of different types of cluster (NC, Fe, Ni 0.5 Fe 0.5 ) dispersions on the oxygen evolution reaction activity of nickel iron oxyhydroxide (Ni x Fe y OOH) electrodes were studied. Figure 9 Linear sweep voltammograms of the oxygen evolution reaction in Examples 6 - 9. By comparing the linear sweep voltammograms of NC / Ni x Fe y OOH, Fe / Ni x Fe y OOH, Ni 0.5 Fe 0.5 / Ni x Fe y OOH electrodes in the corresponding cluster dispersions, it can be seen that the oxygen evolution reaction activities of the three cluster - activated nickel iron oxyhydroxide electrodes are all better than those of the non - cluster - activated nickel iron oxyhydroxide electrodes, and the NC / Ni x Fe y OOH electrode has the best activity in the NC / KOH electrolyte. Subsequent NC / Ni x Fe y OOH electrodes are all synthesized with NC as the activating substance.

[0124] Figure 10Linear sweep voltammetry curve of the oxygen evolution reaction in Example 10. The nickel cluster dispersions (NC / 1M KOH, NC / 4M KOH, NC / 6M KOH) were obtained by cyclic voltammetry activation of nickel foam in electrolytes with different concentrations (1M KOH, 4M KOH, 6M KOH). By testing NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y The linear sweep voltammetry curves of the OOH-6 electrode in the corresponding electrolytes show that the NC / Ni x Fe y OOH electrode has good activity in the cluster dispersions of all three concentrations. Among them, the NC / Ni x Fe y OOH-4 electrode has better activity. Subsequent studies on the NC / Ni x Fe y OOH performance were mainly carried out in the NC / 4M KOH dispersion.

[0125] Figure 11 Linear sweep voltammetry curve of the oxygen evolution reaction in Example 11. The activity of the NC / Ni x Fe y OOH electrode in the NC / 4M KOH dispersion synthesized at different cyclic voltammetry potentials was studied. By comparing and analyzing the activities of the NC / Ni x Fe y OOH electrode in the NC / KOH-2.0 dispersion synthesized at a cyclic voltammetry potential of 1.8 - 2.0V (vs RHE) and the NC / KOH-1.3 dispersion synthesized at a cyclic voltammetry potential of 1.3 - 1.8V (vs RHE), it can be seen that the activity of the NC / Ni x Fe y OOH-2.0 electrode is better than that of the NC / Ni x Fe y OOH-1.3 electrode. Subsequent NC / Ni x Fe y OOH performance studies required NC to be mainly synthesized at a potential of 1.8 - 2.0V vs RHE.

[0126] Figure 12 Linear sweep voltammetry curve of the oxygen evolution reaction in Example 12. Nickel cluster dispersions were synthesized at different cyclic voltammetry times, and the activity of the NC / Ni x Fe y OOH electrode in the above nickel cluster dispersions was studied. By comparing and analyzing NC / Ni x Fey From the linear sweep voltammograms of the OOH electrode in the nickel cluster dispersion after cyclic voltammetric activation at 20, 100, and 200 cycles, it can be seen that NC / Ni x Fe y OOH-100 and NC / Ni x Fe y The activities of the OOH-200 electrodes are almost the same and slightly better than that of NC / Ni x Fe y The activity of the OOH-20 electrode, and subsequently NC / Ni x Fe y The required NC activation time for OOH performance study is 100 cycles.

[0127] Figure 13 and Figure 16 (f) in is the linear sweep voltammogram of the oxygen evolution reaction in Example 13. The effect of different stirring speeds on the activity of the NC / Ni x Fe y OOH electrode was studied. From Figure 13 it can be seen that the activity of the NC / Ni x Fe y OOH electrode in NC / 4MKOH-0 is significantly lower than that of the NC / Ni x Fe y OOH electrode in NC / 4M KOH-500 and NC / 4M KOH-800, and in NC / 4M KOH-500 and NC / 4M KOH-800, the NC / Ni x Fe y OOH electrode activities are comparable, indicating that the rotation speed has a greater impact on the activity, but after greater than 500 r / min, the impact is basically gone. From Figure 16 (f) in it can be seen that when the mechanical stirring speed is 0 r / min, after the NC / Ni x Fe y OOH electrode works for 1 cyclic voltammetry in the NC / 4M KOH electrolyte, the performance deteriorates, and then the NC / Ni x Fe y OOH works for 1 cyclic voltammetry in the NC / 4M KOH electrolyte at 500 r / min, the performance improves; then, the NC / Ni x Fe y OOH works for 10 cyclic voltammograms in the NC / 4M KOH electrolyte at 0 r / min, the performance deteriorates again, and then the NC / Ni x Fe y OOH works for 10 cyclic voltammograms in the NC / 4M KOH electrolyte at 500 r / min, the performance improves again; finally, the NC / Ni x Fey After 100 cyclic voltammograms of OOH working in NC / 4M KOH electrolyte at 0 r / min, the performance deteriorated for the third time, and then NC / Ni x Fe y After 100 cyclic voltammograms of OOH working in NC / 4M KOH electrolyte at 500 r / min, the performance improved for the third time, fully indicating that appropriate stirring can help NC / Ni x Fe y OOH achieves good self-healing performance in NC / 4M KOH electrolyte.

[0128] Figure 14 Linear sweep voltammogram of the oxygen evolution reaction for Example 14. The effects of different concentrations of nickel cluster dispersions on the activity of the NC / Ni x Fe y OOH electrode were studied. When the volume ratio of the nickel cluster dispersion to the saline-alkali water was fixed at 1:1, by comparing the linear sweep voltammograms of the NC / Ni x Fe y OOH electrode in NC / (1M KOH + SAW), NC / (2M KOH + SAW), NC / (3M KOH + SAW), NC / (4M KOH + SAW), NC / (5M KOH + SAW), NC / (6M KOH + SAW) electrolytes respectively, it can be seen that when the electrolyte is NC / (4M KOH + SAW), the NC / Ni x Fe y OOH electrode has the best activity.

[0129] Figure 15 Linear sweep voltammogram of the oxygen evolution reaction for Example 15. The effects of different volumes of NC / 4M KOH dispersion on the activity of the NC / Ni x Fe y OOH electrode were studied. When the concentration of the KOH solution was fixed at 4 mol / L, by comparing the linear sweep voltammograms of the NC / Ni x Fe y OOH electrode in NC / (0% KOH + SAW), NC / (10% KOH + SAW), NC / (30% KOH + SAW), NC / (50% KOH + SAW), NC / (70% KOH + SAW), NC / (90% KOH + SAW) electrolytes respectively, it can be seen that when the electrolyte is NC / (50% KOH + SAW), the NC / Ni x Fe y OOH electrode has the best activity.

[0130] Figure 16are the Faraday efficiency (a), Tafel slope (b), electrochemically active area (c), AC impedance (d), linear sweep voltammogram (e - f), segmented E - t plot (g), and chronopotentiogram (h) of the oxygen evolution reaction in Examples 6 - 9 and 14. Through analysis, it can be seen that NC / Ni x Fe y OOH electrode has the highest Faraday efficiency (98.2%) when working in the NC / (4M KOH + SAW) electrolyte, the smallest Tafel slope (47.4 mV dec -1 ), the largest C dl value (2.58 mF cm -2 ), the smallest impedance value (0.29 Ω), the lowest overpotential (149 mV@10 mA cm -2 ), the best stability (activity decay < 5% at 100 h@500 mA cm -2 ), and good self - healing performance, and NC is a heterogeneous catalyst reaction.

[0131] Figure 17 are the XRD patterns (a), FTIR spectra (b), Raman spectra (c - d), and high - resolution XPS spectra (e - f) of the NiFe - MOF in Example 3 and the NC / Ni x Fe y OOH electrode in Example 6. From the XRD pattern (a), it can be seen that a characteristic peak corresponding to the (020) crystal plane of NiFe - MOF appears at 2θ = 6.48°, while NC / Ni x Fe y OOH shows an amorphous structure. From the FTIR spectrum (b), it can be seen that the characteristic peaks at 1662 cm -1 and 1278 cm -1 in the ligand disappear in the MOF composite material, further confirming the synthesis of NiFe - MOF; the characteristic peaks at 1584, 1521, and 775 cm -1 disappear, indicating the reconstruction of NiFe - MOF after cyclic voltammetry activation. From the Raman spectra (c - d), it can be seen that a characteristic peak of M - O (Ni -1 / Fe 2+ ) appears at 554 cm 3+ , and characteristic peaks of carboxylate in the ligand appear at 1532, 1340, and 1241 cm -1 , further indicating the existence of NiFe - MOF; after cyclic voltammetry activation of NiFe - MOF, characteristic peaks corresponding to NiOOH appear at 554 and 475 cm -1 , thus indicating that the reconstruction product of NiFe - MOF is NC / Ni x Fe yOOH. The high-resolution XPS spectra (e-f) show the presence of high-valent nickel (Ni 3+δ ) and a shift towards higher binding energy, further confirming the synthesis of NC / Ni x Fe y OOH.

[0132] Figure 18 These are the SEM images (a-c) of the NC / Ni x Fe y OOH electrode of Example 6 of the present invention. As can be seen from Figure 18 , the NC / Ni x Fe y OOH electrode completely inherits the hierarchical porous honeycomb structure composed of one-dimensional nanobelts in NiFe-MOF.

[0133] Figure 19 These are the TEM images (a-e) of the NC / Ni x Fe y OOH electrode of Example 6 of the present invention. As can be seen from Figure 19 , the EDS element distribution is uniform, and the selected electron diffraction pattern shows the (210), (002), and (011) crystal planes corresponding to NiOOH. Through the multi-faceted structural characterization of the NC / Ni x Fe y OOH electrode, it can be confirmed that the precursor NiFe-MOF was successfully synthesized in Example 3, and the NC / Ni x Fe y OOH electrode was successfully synthesized in Example 6.

[0134] Figure 20 These are the electrochemical performances (a-d) of the overall reaction of saline-alkali water splitting in Example 16. As can be seen from Figure 20 , the NC / Ni x Fe y OOH||Pt / C electrode has good activity (1.411 V@10 mA cm -2 ), high Faraday efficiency (95.2%@500 mA cm -2 ), and durability (100 h@500 mA cm -2 with less than 10% activity decay) in the overall reaction of saline-alkali water splitting.

Claims

1. A preparation method of a cluster-type self-healing nickel iron hydroxyoxide / nickel electrode, characterized in that, It includes the following steps: Step 1: In a three-electrode electrochemical system, using a foam metal as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, and an alkaline solution as the electrolyte, at a certain stirring rate, at the oxygen evolution reaction potential, cyclic voltammetry is used to obtain a metal cluster dispersion; Step 2: In a three-electrode electrochemical system, using a nickel metal-organic framework or a nickel-iron metal-organic framework as the working electrode, Hg / HgO as the reference electrode, a carbon material or a noble metal material as the counter electrode, using the metal cluster dispersion obtained in Step 1 as the electrolyte, at a certain stirring rate, at the oxygen evolution reaction potential, cyclic voltammetry is used to obtain a cluster-type self-healing nickel iron oxyhydroxide electrode or a nickel electrode.

2. The method according to claim 1, wherein The nickel-iron metal-organic framework is obtained by dissolving 2-thiophenecarboxylic acid, nickel acetate, and iron nitrate in ethanol, and then reacting with a nickel foam substrate in a closed environment at 150 ± 10 °C for 0.5 - 16 h. Among them, by mass ratio, iron nitrate: (iron nitrate + nickel acetate) = 0.05 - 0.20; the nickel metal-organic framework is obtained by dissolving 2-thiophenecarboxylic acid and nickel acetate in ethanol, and then reacting with a nickel foam substrate in a closed environment at 150 ± 10 °C for 12 h; the alkaline solution is a KOH solution or an NaOH solution, with a concentration of 1 - 6 mol / L, preferably 4 - 6 mol / L, and the foam metal is foam nickel, foam iron, or foam nickel-iron.

3. The method according to claim 1, characterized in that, In Step 1, the cyclic voltammetry potential is 1.3 - 2.0 V (vs RHE), the number of cyclic voltammetry scan cycles is 20 - 200, and the stirring rate is 500 - 800 r / min; in Step 2, the cyclic voltammetry potential is 0.9 - 1.7 V (vs RHE), the number of cyclic voltammetry scan cycles is 20 - 200, and the stirring rate is 500 - 800 r / min.

4. A cluster-type self-healing nickel iron oxyhydroxide / nickel electrode prepared by the method according to any one of claims 1 - 3.

5. Application of the cluster-type self-healing nickel iron oxyhydroxide / nickel electrode prepared by the method according to any one of claims 1 - 3 in saline-alkali water splitting for hydrogen production.

6. The application according to claim 5, wherein In a three-electrode electrochemical system, after mixing the metal cluster dispersion with the saline-alkali water to be decomposed as the electrolyte, using the cluster-type self-healing nickel iron oxyhydroxide / nickel electrode as the working electrode, Hg / HgO as the reference electrode, and a carbon material or a noble metal material as the counter electrode, saline-alkali water oxygen evolution reaction is carried out.

7. The application according to claim 6, characterized in that The linear sweep voltammetry potential of the saline-alkali water oxygen evolution reaction is 1.0 - 1.8 V (vs RHE), the stirring rate is 500 r / min, and the iR compensation is 85%; the volume ratio of the metal cluster dispersion to the saline-alkali water is 10% - 90%, preferably 50% - 90%.

8. Application of the cluster-type self-healing nickel iron oxyhydroxide / nickel electrode prepared by the method according to any one of claims 1 - 3 in the overall saline-alkali water splitting reaction.

9. The application according to claim 8, characterized in that, In a two-electrode electrochemical system, after mixing the metal cluster dispersion with the saline-alkali water to be decomposed as the electrolyte, using the cluster-type self-healing nickel iron oxyhydroxide / nickel electrode as the anode and a platinum-carbon electrode as the cathode, the overall saline-alkali water splitting reaction is carried out.

10. The application according to claim 9, wherein, The linear sweep voltammetry potential of the complete reaction of saline-alkali water cracking is 1.0 - 2.0 V, the stirring rate is 500 r / min, and the iR compensation is 85%; the volume ratio of the metal cluster dispersion liquid to the saline-alkali water is 10% - 90%, preferably 50% - 90%.

Images