Cluster-type self-healing hydroxyl nickel-iron / nickel electrode and its application in hydrogen production by cracking of saline water

Abstract

The application discloses a cluster type self-healing nickel oxyhydroxide / iron-nickel electrode and application thereof in hydrogen production by cracking of saline water, and steps are as follows: under a three-electrode system, a foam metal is used as a working electrode, a cyclic voltammetry method is adopted in a potassium hydroxide solution electrolyte, and a metal cluster dispersion liquid is obtained; under the three-electrode system, a nickel iron / nickel MOF is used as the working electrode, the metal cluster dispersion liquid is used as the electrolyte, the cyclic voltammetry method is adopted, and a target electrode is obtained; and the target electrode is used in hydrogen production by cracking of saline water or a whole reaction of cracking of saline water in the electrolyte obtained by mixing the metal cluster dispersion liquid and the saline water. The target electrode has higher activity and durability and good self-healing performance under the saline water and industrial large current density (500 mA cm ‑2 ).

Description

Technical Field

[0001] This invention relates to a cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode and its application in hydrolysis of saline-alkali water for hydrogen production, belonging to the field of water electrolysis electrode technology. Background Technology

[0002] Water splitting for hydrogen production is a clean and environmentally friendly method, but the significant thermodynamic delays in the anodic oxygen evolution reaction and the cathode hydrogen evolution reaction limit the activity, stability, and energy efficiency of water electrolysis. To mitigate this, highly active precious metal catalysts (such as iridium oxide and platinum) are commercially used for water electrolysis, but their scarcity and high price severely restrict their widespread application. Furthermore, most of these materials require freshwater or purified water as the electrolyte, exacerbating the consumption of scarce freshwater resources and incurring additional investment costs.

[0003] In contrast, the Earth is rich in low-quality water, such as seawater and inland saline water. If synthesized electrodes can be used directly or after simple treatment of this low-quality water for hydrogen production via water electrolysis, it would be crucial for achieving sustainable use of clean energy and environmental protection. To this end, scholars have conducted some research on seawater and proposed several common guiding principles; however, the application of these methods to other low-quality water remains controversial. Further development of highly active, durable, and economical electrodes is needed to conduct in-depth research on hydrogen production from the cracking of other low-quality waters, promoting the high-value utilization of these water resources.

[0004] Self-healing electrocatalysts, through special structural design or composition methods, can automatically repair damaged sites and restore their electrocatalytic activity, showing promise as potential materials for solving the aforementioned problems. Currently, common self-healing catalytic electrodes are mainly based on metal ions, such as Ni. 2+ Co 2+ Buffer solutions composed of phosphate, carbonate, or borate have certain limitations in system design. Summary of the Invention

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

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

[0007] The cluster-type self-healing nickel-iron / nickel oxide electrode and its preparation method described in this invention include the following steps:

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

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

[0010] Furthermore, the nickel-iron metal-organic framework is obtained by dissolving 2-thiophenecarboxylic acid, nickel acetate, and ferric nitrate in ethanol, and then reacting them together with a nickel foam substrate in a closed environment at 150±10℃ for 0.5-16 h, wherein, by mass ratio, ferric nitrate:(ferric 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 them together with a nickel foam substrate in a closed environment at 150±10℃ for 12 h.

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

[0012] Furthermore, in step two, the cyclic voltammetric potential is 0.9-1.7V (vs RHE), the number of cyclic voltammetric 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 hydroxyl oxide / nickel electrode. The specific steps are as follows: in a three-electrode electrochemical system, the above-mentioned metal cluster dispersion is mixed with the salt water to be decomposed and used as the electrolyte. The cluster-type nickel-iron hydroxyl oxide / nickel electrode is used as the working electrode, Hg / HgO is used as the reference electrode, and carbon material or noble metal material is used as the counter electrode to carry out the oxygen evolution reaction of salt water.

[0014] Furthermore, the linear sweep voltammetric potential for the oxygen evolution reaction in saline-alkali water was 1.0-1.8 V (vs RHE), the stirring rate was 500 r / min, and the iR compensation was 85%.

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

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

[0017] Furthermore, the linear sweep voltammetric potential for the complete salt-alkali water cracking reaction was 1.0-2.0 V, the stirring rate was 500 r / min, and the iR compensation was 85%.

[0018] Compared with the prior art, the advantages of this invention are: (1) The three-electrode cyclic voltammetry synthesis of metal cluster dispersions and cluster-type nickel-iron / nickel hydroxyl oxide electrodes is simple and can be mass-produced industrially; (2) The cluster-type nickel-iron / nickel hydroxyl oxide electrode has a hierarchical porous honeycomb structure, with a strong bond between the substrate and the active material, and provides abundant active sites, which is conducive to the rapid transfer of electrons and protons and the transport of reaction products; (3) The use of saline-alkali water as the electrolyte is conducive to the high-value utilization of low-quality water; (4) The cluster-type nickel-iron / nickel hydroxyl oxide electrode material is effective in saline-alkali water and industrial high current density (500 mA cm⁻¹). -2 It exhibits high activity, durability, and good self-healing properties. Attached Figure Description

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

[0020] Figure 2 These are SEM images (ad) of Ni-MOF at different magnifications and their elemental distribution maps (C, O, S, Ni) in Embodiment 1 of the present invention.

[0021] Figure 3 These are SEM images (ac) of NiFe-MOF-5%Fe at different multiples and their elemental distribution maps (C, O, S, Ni, Fe) in Example 2 of this invention.

[0022] Figure 4 These are SEM images (ac) of NiFe-MOF obtained at different folds and their elemental distribution maps (C, O, S, Ni, Fe) obtained in Example 3 of this invention with a reaction time of 12h.

[0023] Figure 5 These are SEM images (ac) of NiFe-MOF-15%Fe at different multiples and their elemental distribution maps (C, O, S, Ni, Fe) of Example 4 of the present invention.

[0024] Figure 6These are SEM images (ac) of NiFe-MOF-20%Fe at different multiples and their elemental distribution maps (C, O, S, Ni, Fe) of Example 5 of the present invention.

[0025] Figure 7 These are SEM images (al) of the electrode obtained at different reaction times in Example 3 of the present invention at different magnifications.

[0026] Figure 8 These are linear scanning voltammetric curves (a: forward scan, b: reverse scan) of the MOFs and oxygen evolution reaction of commercial electrodes in Examples 1-5 of this invention.

[0027] Figure 9 These are linear scanning voltammetric curves (a: forward scan, b: reverse scan) of the oxygen evolution reaction of the clustered hydroxyl nickel-iron electrode of Examples 6-9 of the present invention.

[0028] Figure 10 These are linear sweep voltammetric curves (a: forward sweep, b: reverse sweep) of the oxygen evolution reaction of the clustered nickel-iron hydroxyl oxide electrode in different concentrations of NC / KOH dispersions according to Example 10 of the present invention.

[0029] Figure 11 These are linear scanning voltammetric curves (a: forward scan, b: reverse scan) of the oxygen evolution reaction of the clustered hydroxyl nickel-iron electrode in Example 11 of this invention at different potentials.

[0030] Figure 12 These are linear scanning voltammetric curves (a: forward scan, b: reverse scan) of the oxygen evolution reaction of the cluster-type self-healing nickel-iron hydroxyl oxide electrode of Example 12 of the present invention at different cyclic voltammetric times.

[0031] Figure 13 These are linear sweep voltammetric curves (a: forward sweep, b: reverse sweep) of the oxygen evolution reaction of the cluster-type self-healing nickel-iron hydroxyl oxide electrode of Example 13 of the present invention at different stirring rates.

[0032] Figure 14 The linear sweep voltammetric curves (a: forward sweep, b: reverse sweep) of the oxygen evolution reaction of the clustered nickel-iron hydroxyl oxide electrode in Example 14 of this invention in different concentrations of NC / KOH dispersion and saline-alkali water mixed electrolyte are shown.

[0033] Figure 15 The linear sweep voltammetric curves (a: forward sweep, b: reverse sweep) of the oxygen evolution reaction of the clustered nickel-iron hydroxyl oxide electrode of Example 15 of the present invention in different volumes of NC / KOH dispersion and saline-alkali water mixed electrolyte are shown.

[0034] Figure 16The following are the Faraday efficiency (a), Tafel slope (b), electrochemical active area (c), AC impedance (d), linear sweep voltammetry curves (e: different electrodes, f: different stirring rates and different cyclic voltammetry times), segmented Et plots (g), and chronovoltammograms (h) of the oxygen evolution reaction of electrodes in Examples 6-9 and 14 of this invention.

[0035] Figure 17 The NiFe-MOF obtained in Example 3 of this invention with a reaction time of 12 h and the NC / Ni in Example 6 are examples of the present invention. x Fe y XRD spectrum (a), FTIR spectrum (b), Raman spectrum (cd), and high-resolution XPS spectrum (ef) of OOH.

[0036] Figure 18 This is the NC / Ni of Embodiment 6 of the present invention. x Fe y SEM images of OOH at different folds (ac).

[0037] Figure 19 This is the NC / Ni of Embodiment 6 of the present invention. x Fe y TEM images of OOH at different magnifications (ae).

[0038] Figure 20 The electrochemical performance of the salt-alkali water splitting reaction in Example 16 of this invention is shown in the figures (a: linear sweep voltammetry, b: chronoscopic potential, c: gas collection device, d: Faraday efficiency). Detailed Implementation

[0039] Water splitting for hydrogen production is a clean and green method, but the oxygen evolution reaction in water splitting is thermodynamically slow, limiting the activity, stability, and energy efficiency of water electrolysis. The rarity and high price of commercially available precious metal catalysts severely restrict their widespread application. Furthermore, most of the aforementioned materials require freshwater or purified water as the electrolyte, exacerbating the consumption of scarce freshwater resources and incurring additional investment costs. However, large quantities of low-quality water, such as seawater, brine, and saline water, are widely distributed on Earth. If synthesized electrodes could be used directly or after simple treatment of low-quality water for water electrolysis to produce hydrogen, it would be crucial for achieving sustainable use of clean energy and environmental protection. Self-healing electrocatalysts, through special structural design or composition methods, can automatically repair damaged sites and restore their electrocatalytic activity, showing promise as potential materials for solving the above problems. Currently, common self-healing catalytic electrodes are mainly based on metal ions, such as Ni. 2+ Co 2+Buffer solutions composed of phosphate, carbonate, or borate ions have certain limitations in system design. Building upon this, we innovatively propose a clustered hydroxyl oxide nickel-iron self-supporting electrode for oxygen evolution reaction and water splitting to produce hydrogen in saline-alkali water. This electrode features a hierarchical porous honeycomb structure composed of one-dimensional nanoribbons, exhibiting strong bonding between the hydroxyl oxide nickel-iron and the substrate. This provides numerous exposed active sites, facilitating rapid electron and proton transfer and rapid transport of reaction products. It demonstrates high activity and durability, and exhibits excellent self-healing properties.

[0040] Combination Figure 1 Taking a nickel-iron electrode as an example, this invention provides a method for preparing a cluster-type self-healing hydroxyl oxide nickel-iron electrode and its application in the oxygen evolution reaction of saline-alkali water, including the following steps:

[0041] Step 1: Dissolve 2-thiophenecarboxylic acid, nickel acetate and ferric nitrate in ethanol, and then heat and react them together with the 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, carbon material or noble metal material as the counter electrode, and potassium hydroxide (KOH) solution as the electrolyte, a dispersion of nickel metal clusters is obtained by cyclic voltammetry at the oxygen evolution reaction potential.

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

[0044] Step 4: In the three-electrode electrochemical system, the nickel metal cluster dispersion from Step 2 is mixed with saline-alkali water as the electrolyte. The nickel metal cluster hydroxyl oxide nickel-iron electrode obtained in Step 3 is used as the working electrode, Hg / HgO is used as the reference electrode, and carbon material or noble metal material is used as the counter electrode to carry out the anodic oxygen evolution reaction and obtain excellent electrocatalytic performance.

[0045] This invention is illustrated by the following examples, but these examples are for illustrative purposes only and should not be construed as limiting the scope or application of the invention. Unless otherwise specified, the raw materials of this invention—foamed nickel, foamed iron, foamed nickel-iron, and IrO2—are all commercially available.

[0046] Example 1:

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

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

[0049] Step 3: The product obtained in Step 2 is washed and dried to obtain a nickel metal-organic framework (named Ni-MOF). Its SEM image and elemental distribution are shown below. Figure 2 As shown.

[0050] Step 4: In a three-electrode electrochemical system, the Ni-MOF from Step 3 is used as the working electrode, the graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, and 1 mol / L KOH solution as the electrolyte. Mechanical stirring is performed, the oxygen evolution reaction potential is 0.9-1.7 V (vs RHE), and the scan rate is 5 mV / s. Linear sweep voltammetry is then performed to obtain the linear sweep voltammetry curve of Ni-MOF in the 1 mol / L KOH electrolyte, as shown below. Figure 8 As shown.

[0051] Example 2:

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

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

[0054] Step 3: The product obtained in Step 2 was washed and dried to obtain a nickel-iron metal-organic framework (named NiFe-MOF-5%Fe). Its SEM image and elemental distribution are shown below. Figure 3 As shown.

[0055] Step 4: In the three-electrode electrochemical system, using NiFe-MOF-5%Fe from Step 3 as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, and 1 mol / L KOH solution as the electrolyte, mechanical stirring was performed. The oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), and the scan rate was 5 mV / s. Linear sweep voltammetry was conducted to obtain the linear sweep voltammetry curve of NiFe-MOF-5%Fe in 1 mol / L KOH electrolyte, as shown below. Figure 8 As shown.

[0056] Example 3:

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

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

[0059] Step 3: The product obtained in Step 2 is washed and dried to obtain a nickel-iron metal-organic framework (named NiFe-MOF). Its SEM image and elemental distribution map are shown below. Figure 4 As shown, XRD, FTIR, and Raman spectroscopy are as follows: Figure 17 As shown.

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

[0061] Example 4:

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

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

[0064] Step 3: The product obtained in Step 2 is washed and dried to obtain the precursor of nickel-iron hydroxyl oxide, namely the nickel-iron metal-organic framework (named NiFe-MOF-15%Fe). SEM images and its elemental distribution are shown below. Figure 5 As shown.

[0065] Step 4: In the three-electrode electrochemical system, NiFe-MOF-15%Fe from Step 3 was used as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, and 1 mol / L KOH solution as the electrolyte. Mechanical stirring was performed, with the oxygen evolution reaction potential at 0.9-1.7 V (vs RHE). The scan rate was 5 mV / s. Linear sweep voltammetry was conducted to obtain the linear sweep voltammetry curve of NiFe-MOF-15% Fe in the 1 mol / L KOH electrolyte, as shown below. Figure 8 As shown.

[0066] Example 5:

[0067] Step 1: Dissolve 0.48g nickel acetate, 0.12g ferric nitrate and 0.6g 2-thiophenecarboxylic acid in ethanol solution and stir thoroughly to form a homogeneous mixture;

[0068] Step 2: Place the mixed solution obtained in Step 1 together with the nickel foam substrate in a sealed environment and heat at 150°C for 12 hours;

[0069] Step 3: The product obtained in Step 2 is washed and dried to obtain the precursor of nickel-iron hydroxyl oxide, namely the nickel-iron metal-organic framework (named NiFe-MOF-20%Fe). SEM images and its elemental distribution are shown below. Figure 6 As shown.

[0070] Step 4: In the three-electrode electrochemical system, NiFe-MOF-20%Fe from Step 3 was used as the working electrode, a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, and 1 mol / L KOH solution as the electrolyte. Mechanical stirring was performed, with the oxygen evolution reaction potential at 0.9-1.7 V (vs RHE). The scan rate was 5 mV / s. Linear sweep voltammetry was conducted to obtain the linear sweep voltammetry curve of NiFe-MOF-20%Fe in the 1 mol / L KOH electrolyte. Figure 8 As shown.

[0071] Example 6:

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

[0073] Step 2: Using the NC / KOH dispersion obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential was 0.9-1.7V (vs RHE), the scan rate was 100mV / s, the cyclic scan time was 100 cycles, and the electrolyte rotation speed was 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide (named NC / Ni x Fe y OOH), XRD, FTIR, Raman, XPS such as Figure 17 As shown, SEM and TEM are respectively as follows Figure 18 and 19 As shown;

[0074] Step 3: In the three-electrode electrochemical system, the NC / KOH solution obtained in Step 1 is used as the electrolyte, along with the NC / Ni solution from Step 2. x Fe y OOH was used as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed was 500 r / min, Hg / HgO was used as the reference electrode, the oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the Faraday efficiency test current density was 100 mA / cm². -2 Linear sweep current-voltage characteristics and Faraday efficiency were tested to obtain NC / Ni x Fe y The linear sweep voltammetric curves and Faraday efficiency of OOH in NC / KOH dispersion are shown below. Figure 9 and Figure 16 As shown in 'a'.

[0075] Example 7:

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

[0077] Step 2: Using the Fe / KOH dispersion obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential was 0.9-1.7V (vs RHE), the scan rate was 100mV / s, the cyclic scan time was 100 cycles, and the electrolyte rotation speed was 500r / min, thereby obtaining iron cluster hydroxyl iron oxide (named Fe / Ni x Fe y OOH);

[0078] Step 3: Use the Fe / KOH solution obtained in Step 1 as the electrolyte, and the Fe / Ni solution from Step 2... x Fe y OOH was used as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed was 500 r / min, Hg / HgO was used as the reference electrode, the oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the Faraday efficiency test current density was 100 mA cm⁻¹. -2 Linear sweep voltammetry and Faraday efficiency tests were performed to obtain the Fe / Ni ratio.x Fe y The linear sweep voltammetric curves and Faraday efficiency of OOH in Fe / KOH dispersion are shown below. Figure 9 and Figure 16 As shown in 'a'.

[0079] Example 8:

[0080] Step 1: Make one piece of foamed nickel-iron (nickel-iron) measuring 1cm × 1cm × 1.6mm (name it Ni). 0.5 Fe 0.5 Using a graphite carbon rod as the working electrode and Hg / HgO as the reference electrode, a 1 mol / L KOH electrolyte was prepared. Cyclic voltammetry was used with a reaction potential of 1.8–2.0 V (vs RHE), a scan rate of 100 mV / s, a cycle time of 100 revolutions, and an electrolyte rotation speed of 500 r / min to obtain a dispersion of nickel-iron clusters (named Ni). 0.5 Fe 0.5 / KOH);

[0081] Step 2: Take the Ni obtained in Step 1 0.5 Fe 0.5 Using KOH dispersion as the electrolyte, NiFe-MOF (as in Example 3) as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry was 0.9-1.7 V (vs RHE), the scan rate was 100 mV / s, the cyclic scan time was 100 cycles, and the electrolyte rotation speed was 500 r / min, thereby obtaining nickel-iron cluster hydroxyl iron oxide (named NiFeO). 0.5 Fe 0.5 / Ni x Fe y OOH);

[0082] Step 3: Take the Ni obtained in Step 1 0.5 Fe 0.5 / KOH solution as electrolyte, with Ni in step two 0.5 Fe 0.5 / Ni x Fe y OOH was used as the working electrode, a graphite carbon rod as the counter electrode, the electrolyte rotation speed was 500 r / min, Hg / HgO was used as the reference electrode, the oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the Faraday efficiency test current density was 100 mA / cm². -2 Linear sweep current-voltage characteristics and Faraday efficiency were tested to obtain Ni 0.5 Fe 0.5 / Ni x Fe y OOH in Ni 0.5Fe 0.5 The linear sweep voltammetric curves of the KOH dispersion are shown below. Figure 9 As shown.

[0083] Example 9:

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

[0085] Step 2: Use 4 mol / L KOH solution as the electrolyte, and Ni from Step 1... x Fe y Using OOH as the working electrode and a graphite carbon rod as the counter electrode, the electrolyte rotation speed was 500 r / min. Hg / HgO was used as the reference electrode. The oxygen evolution reaction potential was 0.9–1.7 V (vs RHE). The scan rate was 5 mV / s. Linear scan voltammetry was performed to obtain the Ni... x Fe y Linear sweep voltammetric curve of OOH in 4 mol / L KOH dispersion, as shown Figure 9 As shown.

[0086] Example 10:

[0087] Step 1: Prepare three pieces of nickel foam with dimensions of 1cm×1cm×1.6mm as working electrodes, and prepare 1, 4, and 6 mol / L KOH electrolytes respectively. Use a graphite carbon rod as the counter electrode and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8-2.0V (vsRHE), the scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min to obtain dispersions of nickel clusters (named NC / 1M KOH, NC / 4M KOH, and 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 electrolyte, with NiFe-MOF from Example 3 as the working electrode, 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 scan rate was 100 mV / s, the scan time was 100 cycles, and the electrolyte rotation speed was 500 r / min, thereby obtaining nickel cluster hydroxyl iron oxide (named NC / Ni x Fey OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y OOH-6);

[0089] Step 3: Use the NC / 1M KOH, NC / 4M KOH, and NC / 6M KOH dispersions obtained in Step 1 as the electrolyte, and the NC / Ni from Step 2 as the electrolyte. x Fe y OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y Using OOH-6 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, linear sweep voltammetry was performed. The oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the electrolyte rotation speed was 500 r / min, thus obtaining NC / Ni x Fe y OOH-1, NC / Ni x Fe y OOH-4, NC / Ni x Fe y Linear sweep voltammetric curves of OOH-6 in NC / 1M KOH, NC / 4M KOH, and NC / 6M KOH electrolytes, as shown below Figure 10 As shown.

[0090] Example 11:

[0091] Step 1: Prepare two pieces of nickel foam measuring 1cm×1cm×1.6mm as working electrodes, prepare a 4mol / L KOH electrolyte, use a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Activate the nickel foam using cyclic voltammetry. The oxygen evolution reaction potentials are 1.3-1.8V (vs RHE) and 1.8-2.0V (vs RHE), respectively. The scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min, thereby obtaining a dispersion 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 the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential was 0.9-1.7V (vs RHE), the scan rate was 100mV / s, the scan time was 100 cycles, and the electrolyte rotation speed was 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide (named NC / Ni x Fe y OOH-1.3, NC / Ni x Fe y OOH-2.0);

[0093] Step 3: Use the NC / 4M KOH-1.3 and NC / 4M KOH-2.0 solutions obtained in Step 1 as the electrolyte, and then use the NC / Ni solution from Step 2... x Fe y OOH-1.3, NC / Ni x Fe y Using OOH-2.0 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, linear sweep voltammetry was performed. The oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the electrolyte rotation speed was 500 r / min, thus obtaining NC / Ni x Fe y OOH-1.3, NC / Ni x Fe y Linear sweep voltammetric curves of OOH-2.0 in NC / 4M KOH-1.3 and NC / 4M KOH-2.0 electrolytes are shown below. Figure 11 As shown.

[0094] Example 12:

[0095] Step 1: Prepare three pieces of nickel foam with a size of 1cm×1cm×1.6mm as working electrodes, prepare a 4mol / L KOH electrolyte, use a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Use cyclic voltammetry with a potential of 1.8-2.0V vs RHE, a scan rate of 100mV / s, and scan times of 20, 100, and 200 cycles respectively. Rotate the electrolyte at 500r / min to obtain a dispersion of nickel clusters (named NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200).

[0096] Step 2: Using the NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200 solutions obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential was 0.9-1.7V (vs RHE), the scan rate was 100mV / s, the scan time was 100 cycles, and the electrolyte rotation speed was 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide (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 from Step 2... x Fe y OOH-20, NC / Ni x Fe y OOH-100, NC / Ni x Fe y Using OOH-200 as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, linear sweep voltammetry was performed. The oxygen evolution reaction potential was 0.9-1.7 V (vs RHE), the scan rate was 5 mV / s, and the electrolyte rotation speed was 500 r / min, thus obtaining NC / Ni x Fe y OOH-20, NC / Ni x Fe y OOH-100, NC / Ni x Fe y Linear sweep voltammetric curves of OOH-200 in NC / 4M KOH-20, NC / 4M KOH-100, and NC / 4M KOH-200 electrolytes, as shown below Figure 12 As shown.

[0098] Example 13:

[0099] Step 1: Prepare three pieces of nickel foam measuring 1cm×1cm×1.6mm as working electrodes, prepare a 4mol / L KOH electrolyte, use a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The cyclic voltammetry potential is 1.8-2.0V (vs RHE), the scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min, thereby obtaining a nickel cluster dispersion (named NC / 4M KOH).

[0100] Step 2: Using the NC / 4M KOH solution obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9-1.7V (vs RHE), the scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide;

[0101] Step 3: Use the NC / 4M KOH solution obtained in Step 1 as the electrolyte, and the NC / Ni solution from Step 2... x Fe y Using OOH as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, linear sweep voltammetry was performed. The oxygen evolution reaction potential was 0.9–1.7 V (vs RHE), the scan rate was 5 mV / s, and the electrolyte rotation speed was 0, 500, and 800 r / min, respectively, thus obtaining NC / Ni x Fe y Linear sweep voltammetric curves of OOH in NC / 4M KOH-0, NC / 4M KOH-500, and NC / 4M KOH-800 electrolytes, as shown below Figure 13 As shown.

[0102] Example 14:

[0103] Step 1: Prepare 6 pieces of nickel foam with a size of 1cm×1cm×1.6mm as working electrodes, prepare 1-6mol / L KOH electrolyte, use graphite carbon rod as counter electrode, use Hg / HgO as reference electrode, set cyclic voltammetry potential of 1.8-2.0V (vs RHE), scan rate of 100mV / s, scan time of 100 cycles, and electrolyte rotation speed of 500r / min to obtain dispersions of nickel clusters (named NC / 1M KOH, NC / 2M KOH, NC / 3M KOH, NC / 4M KOH, NC / 5M KOH, NC / 6M KOH);

[0104] Step 2: 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 were used as electrolytes. The NiFe-MOF from 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 0.9-1.7V (vs RHE), the scan rate was 100mV / s, the scan time was 100 cycles, and the electrolyte rotation speed was 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide (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: 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 solution (SAW) at a volume ratio of 1:1. Use each of the six mixtures as an electrolyte, with the NC / Ni solution obtained in Step 2 as the electrolyte. 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 was used as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The oxygen evolution reaction potential was 0.9-1.7V (vs RHE). The scan rate was 5mV / s, and the electrolyte rotation speed was 500r / min. Linear sweep voltammetry, AC impedance spectroscopy, Tafel slope simulation, and segmented Et(10-500mA cm) were performed. -2 ) test, chronopotential test (500mA cm -2 ), thereby obtaining 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 voltammetric curves 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), and NC / (6M KOH+SAW) are shown below. Figure 14 As shown; Tafel slope, electrochemical active area, impedance value, piecewise Et plot and chronopotential curve, as follows. Figure 16 As shown.

[0106] Example 15:

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

[0108] Step 2: Using the NC / 4M KOH solution obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9-1.7V (vs RHE), the scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide;

[0109] Step 3: Mix the NC / 4M KOH solution obtained in Step 1 with saline solution (SAW) at volume ratios of 0%, 10%, 30%, 50%, 70%, and 90%, respectively. Use these six mixtures as electrolytes, with the NC / Ni solution from Step 2 as the electrolyte. x Fe yOOH was used as the working electrode, a graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode. The oxygen evolution reaction potential was 0.9-1.7 V (vs RHE). The scan rate was 5 mV / s, and the electrolyte rotation speed was 500 r / min. Linear sweep voltammetry was performed to obtain the NC / Ni... x Fe y Linear sweep voltammetric curves of OOH in electrolytes of NC / (0% KOH+SAW), NC / (10% KOH+SAW), NC / (30% KOH+SAW), NC / (50% KOH+SAW), NC / (70% KOH+SAW), and NC / (90% KOH+SAW) are shown below. Figure 15 As shown.

[0110] Example 16:

[0111] Step 1: Prepare 6 pieces of nickel foam with a size of 1cm×1cm×1.6mm as working electrodes, prepare 4mol / L KOH electrolyte, use graphite carbon rod as counter electrode, use Hg / HgO as reference electrode, cyclic voltammetry potential of 1.8-2.0V (vs RHE), scan rate of 100mV / s, scan time of 100 cycles, electrolyte rotation speed of 500r / min, thereby obtaining a dispersion of nickel clusters;

[0112] Step 2: Using the NC / 4M KOH solution obtained in Step 1 as the electrolyte, with NiFe-MOF from Example 3 as the working electrode, graphite carbon rod as the counter electrode, and Hg / HgO as the reference electrode, the cyclic voltammetry potential is 0.9-1.7V (vs RHE), the scan rate is 100mV / s, the scan time is 100 cycles, and the electrolyte rotation speed is 500r / min, thereby obtaining nickel cluster hydroxyl iron oxide;

[0113] Step 3: In the two-electrode electrochemical system, the NC / 4M KOH solution obtained in Step 1 is mixed with saline solution at a volume ratio of 1:1 as the electrolyte, and the NC / Ni solution from Step 2 is used as the electrolyte. x Fe y The OOH electrode was used as the anode, the platinum-carbon electrode as the cathode, the electrolyte rotation speed was 500 r / min, the total reaction potential for saline-alkali water splitting was 1.0-2.0 V, the scan rate was 5 mV / s, and the Faraday efficiency test current density was 100 mA cm⁻¹. -2 Linear scan voltammetric characteristics, Faraday efficiency, and chronopotential were tested to obtain NC / Ni x Fe y Linear sweep voltammetry curves of OOH in a mixed electrolyte of NC / KOH dispersion and saline solution, Faraday efficiency and stability, such as Figure 20 As shown.

[0114] Figure 2 The image shows the SEM image and elemental distribution of the 0wt% Fe (Ni-MOF) from Example 1. The image is composed of... Figure 2 As can be seen from (ad), the synthesized Ni-MOF is a honeycomb structure with hierarchical pores composed of randomly distributed quasi-one-dimensional nanoribbons. C, O, S and Ni elements are uniformly distributed without element segregation.

[0115] Figure 3 The image shows the SEM image and elemental distribution of 5wt% Fe (NiFe-MOF-5%Fe) in Example 2. The image is composed of... Figure 3 As can be seen from (ac), the synthesized NiFe-MOF-5%Fe is a honeycomb structure with hierarchical pores composed of randomly distributed quasi-one-dimensional nanoribbons. The C, O, S, Ni and Fe elements are uniformly distributed without element segregation.

[0116] Figure 4 The image shows the SEM image and elemental distribution of the 10wt% Fe NiFe-MOF from Example 3. Figure 4 As can be seen from (ac), the synthesized NiFe-MOF is a honeycomb structure with hierarchical pores composed of randomly distributed quasi-one-dimensional nanoribbons. The C, O, S, Ni and Fe elements are uniformly distributed without element segregation.

[0117] Figure 5 The image shows the SEM image and elemental distribution of the NiFe-MOF-15%Fe containing 15wt%Fe in Example 4.

[0118] Among them, by Figure 5 As can be seen from (ac), the synthesized NiFe-MOF-15%Fe is a honeycomb structure with hierarchical pores composed of randomly distributed quasi-one-dimensional nanoribbons. The C, O, S, Ni and Fe elements are uniformly distributed without element segregation.

[0119] Figure 6 The image shows the SEM image and elemental distribution of 20wt% Fe (NiFe-MOF-20%Fe) in Example 5.

[0120] Among them, by Figure 6 As can be seen from (ac), the synthesized NiFe-MOF-20%Fe is a honeycomb structure with hierarchical pores composed of randomly distributed quasi-one-dimensional nanoribbons. The C, O, S, Ni and Fe elements are uniformly distributed without element segregation. Combined with Examples 1-4, the MOFs with different iron contents synthesized by this method have consistent morphology and uniform element distribution, and have good universality.

[0121] Figure 7SEM images of MOF electrodes grown at different times in Example 3. Among them, [images are shown]. Figure 7 As shown in (ah), the morphology of the MOF electrode gradually changes from small particles to randomly distributed quasi-one-dimensional nanoribbons and large particles, extending from 12h to 16h, as shown in Figure (il). The morphology of the MOF electrode is a honeycomb structure with hierarchical pores composed of a single randomly distributed quasi-one-dimensional nanoribbon, indicating that the MOF electrode growth is complete and the morphology no longer changes.

[0122] Figure 8 Linear sweep voltammetry (SSW) curves of the oxygen evolution reaction (OER) of MOFs in Examples 1-5 and commercial electrodes IrO2, NF, and NiFe-MOF-Bulk (prepared according to Mater. Chem. Front., 2023, 7, 5005) are shown. By comparing the SSW curves of MOFs with different iron contents (Ni-MOF, NiFe-MOF-5%Fe, NiFe-MOF-10%Fe (reaction time 12 h), NiFe-MOF-15%Fe, NiFe-MOF-20%Fe), it can be seen that NiFe-MOF has the best OER activity. Subsequent clustered nickel-iron hydroxyl oxide electrodes were synthesized using NiFe-MOF as a precursor.

[0123] Next, we will study different types of clusters (NC, Fe, Ni). 0.5 Fe 0.5 ) dispersion of nickel ferric hydroxide (Ni x Fe y The effect of OOH) electrode on oxygen evolution reaction activity. Figure 9 Linear sweep voltammetry curves of the oxygen evolution reaction in Examples 6-9 are shown, compared with NC / Ni x Fe y OOH, Fe / Ni x Fe y OOH, Ni 0.5 Fe 0.5 / Ni x Fe y Linear sweep voltammetry curves of the OOH electrode in the corresponding cluster dispersions show that the activity of the three cluster-activated nickel-iron hydroxyl oxide electrodes is superior to that of the unactivated nickel-iron hydroxyl oxide electrode, and the NC / Ni ratio is also higher. x Fe y The OOH electrode exhibits optimal activity in the NC / KOH electrolyte, followed by NC / Ni... x Fe y OOH electrodes are all synthesized using NC as the activating agent.

[0124] Figure 10Linear sweep voltammetry curves of the oxygen evolution reaction in Example 10 are shown. Dispersions of nickel clusters obtained by cyclic voltammetry activation of nickel foam in electrolytes of different concentrations (1M KOH, 4M KOH, 6M KOH) were studied (NC / 1M KOH, NC / 4M KOH, NC / 6M KOH). The NC / Ni ratio was tested. 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 electrolyte show that NC / Ni x Fe y The OOH electrode exhibited good activity in cluster dispersions of three different concentrations, with NC / Ni showing particularly good activity. x Fe y The OOH-4 electrode exhibits better activity, followed by NC / Ni x Fe y The performance study of OOH was mainly conducted in NC / 4M KOH dispersion.

[0125] Figure 11 Linear sweep voltammetry curves for the oxygen evolution reaction in Example 11 are shown. The NC / Ni ratio was investigated. x Fe y The activity of the OOH electrode in the synthesis of NC / 4M KOH dispersions at different cyclic voltammetric potentials was analyzed. A comparative analysis of NC / Ni... x Fe y The activity of the OOH electrode in synthesizing NC / KOH-2.0 dispersion at cyclic voltammetry potentials of 1.8–2.0 V (vs RHE) and NC / KOH-1.3 dispersion at cyclic voltammetry potentials of 1.3–1.8 V (vs RHE) indicates that NC / Ni x Fe y The OOH-2.0 electrode exhibits superior activity compared to the NC / Ni electrode. x Fe y OOH-1.3 electrode, subsequent NC / Ni x Fe y The NC required for OOH performance studies was mainly synthesized at potentials of 1.8-2.0V vs RHE.

[0126] Figure 12 Linear sweep voltammetry curves for the oxygen evolution reaction in Example 12 are shown. Nickel cluster dispersions were synthesized at different cyclic voltammetric times, and the NC / Ni ratio was investigated. x Fe y The activity of the OOH electrode in the above nickel cluster dispersion was compared and analyzed with that of NC / Ni. x Fey Linear sweep voltammetric curves of the OOH electrode in nickel cluster dispersions activated by 20, 100, and 200 cycles of cyclic voltammetry show that NC / Ni x Fe y OOH-100 and NC / Ni x Fe y The activity of the OOH-200 electrode is almost the same, and slightly better than that of NC / Ni. x Fe y The activity of the OOH-20 electrode, and subsequent NC / Ni x Fe y The required NC activation time for the OOH performance study was 100 cycles.

[0127] Figure 13 and Figure 16 (f) in the figure represents the linear sweep voltammetry curve of the oxygen evolution reaction in Example 13. The effect of different stirring speeds on NC / Ni was investigated. x Fe y The effect of OOH electrode activity. Figure 13 It can be seen that NC / Ni x Fe y The activity of the OOH electrode in NC / 4MKOH-0 is significantly lower than that in NC / Ni. x Fe y The activity of the OOH electrode in NC / 4M KOH-500 and NC / 4M KOH-800, and in NC / 4M KOH-500 and NC / 4M KOH-800, NC / Ni x Fe y The OOH electrode activity was similar, indicating that the rotation speed had a significant impact on the activity, but the effect was negligible above 500 r / min. Figure 16 From (f), we can see that when the mechanical stirring speed is 0 r / min, NC / Ni x Fe y The OOH electrode deteriorated after one cycle of voltammetry in NC / 4M KOH electrolyte, followed by NC / Ni x Fe y After one cycle of voltammetry in NC / 4M KOH electrolyte at 500 r / min, the performance of OOH improved; subsequently, NC / Ni x Fe y After 10 cycles of voltammetry in NC / 4M KOH electrolyte at 0 r / min, the performance of OOH deteriorated again, followed by NC / Ni x Fe y After 10 cycles of voltammetry in NC / 4M KOH electrolyte at 500 r / min, the performance of OOH improved again; finally, NC / Ni x Fey After 100 cycles of voltammetry in NC / 4MKOH electrolyte at 0 r / min, the performance of OOH deteriorated for the third time, followed by NC / Ni x Fe y After 100 cyclic voltammetry cycles in NC / 4M KOH electrolyte at 500 rpm, the performance of OOH improved for the third time, fully demonstrating that proper stirring can help NC / Ni x Fe y OOH exhibits good self-healing properties in NC / 4M KOH electrolyte.

[0128] Figure 14 Linear sweep voltammetry curves for the oxygen evolution reaction in Example 14 were obtained. The effect of different nickel cluster dispersion concentrations on the NC / Ni ratio was investigated. x Fe y The effect of OOH electrode activity. When the volume ratio of nickel cluster dispersion to saline solution is fixed at 1:1, the NC / Ni ratio is compared. x Fe y Linear sweep voltammetry curves of the OOH electrode in electrolytes of NC / (1M KOH+SAW), NC / (2M KOH+SAW), NC / (3M KOH+SAW), NC / (4M KOH+SAW), NC / (5M KOH+SAW), and NC / (6M KOH+SAW) show that when the electrolyte is NC / (4M KOH+SAW), NC / Ni x Fe y The OOH electrode exhibits the best activity.

[0129] Figure 15 Linear sweep voltammetry curves for the oxygen evolution reaction in Example 15 were obtained. The effects of different volumes of NC / 4MKOH dispersion on NC / Ni were investigated. x Fe y The effect of OOH electrode activity. When the KOH solution concentration was fixed at 4 mol / L, the NC / Ni ratio was compared... x Fe y Linear sweep voltammetry curves of the OOH electrode in electrolytes of NC / (0% KOH+SAW), NC / (10% KOH+SAW), NC / (30% KOH+SAW), NC / (50% KOH+SAW), NC / (70% KOH+SAW), and NC / (90% KOH+SAW) show that when the electrolyte is NC / (50% KOH+SAW), NC / Ni x Fe y The OOH electrode exhibits the best activity.

[0130] Figure 16The following are the Faraday efficiency (a), Tafel slope (b), electrochemical active area (c), AC impedance (d), linear sweep voltammetry (ef), piecewise Et plot (g), and chronopotential plot (h) of the oxygen evolution reaction in Examples 6-9 and 14. Analysis shows that NC / Ni x Fe y The OOH electrode exhibits the highest Faraday efficiency (98.2%) and the lowest Tafel slope (47.4 mV dec) when operating in NC / (4M KOH+SAW) electrolyte. -1 The largest C dl Value (2.58mF cm) -2 The lowest impedance value (0.29Ω) and the lowest overpotential (149mV@10mA cm) are also mentioned. -2 ), with the best stability (100h@500mA cm). -2 It exhibits low activity decay (<5%) and good self-healing properties, and NC is a heterogeneous catalyst reaction.

[0131] Figure 17 It is the NiFe-MOF of Example 3 and the NC / Ni of Example 6. x Fe y XRD (a), FTIR (b), Raman (cd), and high-resolution XPS (ef) spectra of the OOH electrode. From XRD (a), it can be seen that a characteristic peak corresponding to the NiFe-MOF(020) crystal plane appears at 2θ = 6.48°, while the NC / Ni... x Fe y OOH exhibits an amorphous structure. The FTIR spectrum (b) shows that the ligand at 1662 cm⁻¹... -1 and 1278cm -1 The characteristic peaks at 1584, 1521, and 775 cm⁻¹ disappear in the synthesized MOF material, further confirming the synthesis of NiFe-MOF; -1 The disappearance of the characteristic peak at 554 cm⁻¹ indicates that NiFe-MOF underwent reconstruction after cyclic voltammetry activation. Raman spectroscopy (cd) shows that... -1 MO(Ni) appeared at the location 2+ / Fe 3+ Characteristic peaks, 1532, 1340 and 1241 cm⁻¹ -1 The presence of characteristic peaks for the carboxylate group in the ligand further confirms the existence of NiFe-MOF; and after cyclic voltammetric activation, NiFe-MOF showed peaks at 554 and 475 cm⁻¹. -1 The presence of characteristic peaks corresponding to NiOOH indicates that the reconstructed NiFe-MOF is NC / Ni. x Fe yOOH. High-valence nickel (Ni) appeared in the high-resolution XPS spectrum (ef). 3+δ And a shift toward higher binding energy occurred, further confirming NC / Ni x Fe y Synthesis of OOH.

[0132] Figure 18 This is the NC / Ni of Embodiment 6 of the present invention. x Fe y SEM image (ac) of the OOH electrode. Figure 18 It can be seen that NC / Ni x Fe y The OOH electrode fully inherits the hierarchical porous honeycomb structure composed of one-dimensional nanoribbons in NiFe-MOF.

[0133] Figure 19 This is the NC / Ni of Embodiment 6 of the present invention. x Fe y TEM image (ae) of the OOH electrode. Figure 19 It can be seen that the EDS elemental distribution is uniform, and the selected electron diffraction pattern shows the (210), (002), and (011) crystal planes corresponding to NiOOH. Through analysis of NC / Ni... x Fe y Multi-faceted structural characterization of the OOH electrode confirms the successful synthesis of the precursor NiFe-MOF in Example 3 and the successful synthesis of NC / Ni in Example 6. x Fe y OOH electrode.

[0134] Figure 20 This is the electrochemical performance (ad) of the complete salt-alkali water splitting reaction in Example 16. (From...) Figure 20 It can be seen that NC / Ni x Fe y The OOH||Pt / C electrode exhibits good activity in the complete reaction of salt-alkali water cracking (1.411V@10mA cm). -2 High Faraday efficiency (95.2% @ 500 mA cm⁻¹) -2 ) and durability (100h@500mA cm -2 (Active decay is less than 10%).

Claims

1. A method for preparing a cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode, characterized in that, Includes the following steps: Step 1: In a three-electrode electrochemical system, using foam metal as the working electrode, Hg / HgO as the reference electrode, carbon material or noble metal material as the counter electrode, and alkaline solution as the electrolyte, a metal cluster dispersion is obtained by cyclic voltammetry at a certain stirring rate and at the oxygen evolution reaction potential. The foam metal is foam nickel, foam iron, or foam nickel iron. Step 2: In the three-electrode electrochemical system, a nickel metal-organic framework or a nickel-iron metal-organic framework is used as the working electrode, Hg / HgO is used as the reference electrode, and a carbon material or noble metal material is used as the counter electrode. The metal cluster dispersion obtained in Step 1 is used as the electrolyte. Under a certain stirring rate and at the oxygen evolution reaction potential, cyclic voltammetry is used to obtain a cluster-type self-healing hydroxyl oxide nickel-iron electrode or a nickel electrode.

2. The method as described in claim 1, characterized in that, The nickel-iron metal-organic framework is obtained by dissolving 2-thiophenecarboxylic acid, nickel acetate, and ferric nitrate in ethanol, and then reacting them together with a nickel foam substrate in a closed environment at 150±10 °C for 0.5-16 h. The mass ratio of ferric nitrate to (ferric nitrate + nickel acetate) is 0.05-0.

20.

3. The method as described in claim 1, characterized in that, The nickel metal-organic framework was obtained by dissolving 2-thiophenecarboxylic acid and nickel acetate in ethanol, and then reacting them together with a nickel foam substrate in a closed environment at 150±10 °C for 12 h.

4. The method as described in claim 1, characterized in that, The alkaline solution is a KOH solution or a NaOH solution with a concentration of 1-6 mol / L.

5. The method as described in claim 4, characterized in that, The concentration of the alkaline solution is 4~6 mol / L.

6. The method as described in claim 1, characterized in that, In step one, the cyclic voltammetric potential is 1.3-2.0 V vs RHE, the number of cyclic voltammetric scans is 20-200, and the stirring rate is 500-800 r / min; in step two, the cyclic voltammetric potential is 0.9-1.7 V vs RHE, the number of cyclic voltammetric scans is 20-200, and the stirring rate is 500-800 r / min.

7. The cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode prepared by the method according to any one of claims 1-6.

8. The application of the cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode prepared by any one of claims 1-6 in the oxygen evolution reaction of salt-alkali water cracking, characterized in that, The metal cluster dispersion was mixed with the alkaline water to be decomposed and then used as the electrolyte.

9. The application as described in claim 8, characterized in that, In a three-electrode electrochemical system, the cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode is used as the working electrode, Hg / HgO is used as the reference electrode, and carbon material or noble metal material is used as the counter electrode to carry out the oxygen evolution reaction in salt-alkali water.

10. The application of the cluster-type self-healing nickel-iron / nickel hydroxyl oxide electrode prepared by any one of claims 1-6 in the whole reaction of saline-alkali water cracking, characterized in that, The metal cluster dispersion was mixed with the alkaline water to be decomposed and then used as the electrolyte.

11. The application as described in claim 10, characterized in that, In the two-electrode electrochemical system, the cluster-type self-healing nickel-iron / nickel oxide electrode is used as the anode and the platinum-carbon electrode is used as the cathode to carry out the salt-alkali water cracking reaction.

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