CN120817638B

CN120817638B - A method for preparing ultrathin nickel-iron layered bimetallic hydroxides and its application

Info

Publication number: CN120817638B
Application number: CN202511318336.7A
Authority: CN
Inventors: 张延峰; 苏峰; 宫宏宇; 丁孝涛; 刘丽丽; 吴明军; 蒋有钱; 李杰先; 邢巍
Original assignee: Qingdao Saikesaisi Hydrogen Energy Technology Co ltd; SHANDONG SAIKESAISI HYDROGEN ENERGY CO Ltd
Current assignee: Qingdao Saikesaisi Hydrogen Energy Technology Co ltd; SHANDONG SAIKESAISI HYDROGEN ENERGY CO Ltd
Priority date: 2025-09-16
Filing date: 2025-09-16
Publication date: 2026-01-06
Anticipated expiration: 2045-09-16
Also published as: CN120817638A

Abstract

The invention belongs to the technical field of catalytic electrolysis of water, relates to a catalyst for electrolysis of water, and in particular relates to a preparation method and application of ultrathin ferronickel layered double hydroxide. According to the invention, through low-temperature nucleation reaction, crystal aging growth and formamide lamellar stripping, the growth process of the catalyst crystal is regulated and controlled, and the sheet NiFe-LDH catalyst with high purity, good crystallinity and nano scale is obtained. The ultrathin ferronickel layered double hydroxide is coated on the polytetrafluoroethylene plate, and then the oxygen evolution electrode is further formed by a hot-pressing transfer printing method, so that the coating has good bonding degree with a matrix, is not easy to fall off, and is suitable for industrial large-area production.

Description

Preparation method and application of ultrathin ferronickel layered double hydroxide

Technical Field

The invention belongs to the technical field of catalytic electrolysis of water, relates to a catalyst for electrolysis of water, and in particular relates to a preparation method and application of ultrathin ferronickel layered double hydroxide.

Background

The disclosure of this background section is only intended to increase the understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art already known to those of ordinary skill in the art.

Hydrogen energy is considered as an ideal clean energy source and is one of energy sources with wide development prospects in the future. In the hydrogen production technology, the Anion Exchange Membrane (AEM) hydrogen production technology can simultaneously have the advantages of high current density of Proton Exchange Membrane (PEM) hydrogen production, low cost of alkaline water electrolysis hydrogen production (ALK) technology and the like, and is considered to be the technology with the most development prospect in future large-scale hydrogen production.

The core reactions of water electrolysis to produce hydrogen are two spatially independent half reactions, including the oxygen evolution reaction of four electron transfer (OER) that occurs at the anode and the hydrogen evolution reaction of two electron transfer (HER) that occurs at the cathode. Among them, the reaction energy barrier and the electron transfer rate in the OER process of four electrons are slow, which makes it a major problem that limits the wide application of water splitting, and the use of a catalyst can effectively alleviate these problems. Currently, iridium (Ir), ruthenium (Ru) and their oxides are considered to be the most effective catalysts for catalyzing OER. However, noble metals have low natural reserves and high use costs, and large-scale application can greatly increase the production cost of hydrogen energy, which is unfavorable for the development of hydrogen energy. Compared with the common noble metal catalyst, the transition metal (Fe, co, ni and the like) and the hydroxide thereof have relatively high catalytic activity and low cost, and become a research hot spot in recent years, in particular to a hydrotalcite-structured double-metal hydroxide NiFe-LDH catalyst.

At present, when NiFe-LDH is prepared into an anode material for hydrogen production by water electrolysis, a spraying method and a self-supporting method are mainly adopted, wherein the spraying method is to prepare slurry from NiFe-LDH, an organic solvent (ethanol, isopropanol and the like) and an anionic polymerization liquid and the like according to a certain proportion, then spray the slurry on a base material (nickel felt or foam nickel) directly by using spraying equipment to form an anode, and the self-supporting method is to deposit the NiFe-LDH on the surface of the base material by using hydrothermal, electrodeposition or chemical plating and the like to form the NiFe-LDH anode. Compared with a self-supporting method, the spraying method is simple to operate, is more suitable for preparing a large-area NiFe-LDH anode, and is more beneficial to commercial utilization. However, the spraying method has a disadvantage in that the slurry containing NiFe-LDH is directly sprayed onto the substrate, and the slurry is poor in bonding degree with the substrate and easily falls off. The reason for falling off mainly comprises that firstly NiFe-LDH particles are uneven and have large overall particle size, and then fall off easily in the using process, and secondly, the slurry is prepared by adopting an anionic polymer liquid, and part of the anionic polymer liquid can be oxidized and lose efficacy under the long-time oxygen evolution environment to cause poor adhesion and falling off of a coating.

Disclosure of Invention

In order to overcome the problems, the invention provides a preparation method and application of ultrathin nickel-iron layered double hydroxide (NiFe-LDH).

In order to achieve the technical purpose, the invention adopts the following technical scheme:

The invention provides a preparation method of ultrathin ferronickel layered double metal hydroxide, which is in a nano sheet structure, wherein the thickness of a nano sheet is 8-12 nm, and the preparation method comprises the following steps:

(1) Dissolving nickel salt and ferric salt in water, mixing uniformly to obtain solution A, dissolving sodium carbonate and sodium hydroxide in water, mixing uniformly to obtain solution B;

(2) Adding the solution A and the solution B into ethanol water solution at the same time, and continuously stirring;

(3) Aging the stirred reaction solution at a limited temperature, and collecting and washing a precipitate;

(4) Dispersing the washed precipitate into formamide solution, ultrasonically reacting, collecting the precipitate after the reaction, washing and drying to obtain the ultrathin ferronickel layered double hydroxide.

In one or more embodiments, in step (1), the nickel salt is one or more of nickel chloride, nickel nitrate, nickel sulfate, and nickel acetate.

In one or more embodiments, in step (1), the ferric salt is one or more of ferric chloride, ferric nitrate, and ferric sulfate.

In one or more embodiments, in step (1), the molar ratio of nickel salt to ferric salt is (1-6): 0.2-1.5, preferably 5:1. Under the condition that the proportion is limited, the catalysis performance of the ultrathin nickel-iron layered double hydroxide is optimal.

In one or more embodiments, in step (1), the concentration of nickel salt is 0.3 to 0.5 mM, preferably 0.375 mM mM.

In one or more embodiments, in step (1), the molar ratio of sodium carbonate to sodium hydroxide is (0.2 to 0.6): 1, preferably 0.4:1.

In one or more embodiments, in step (1), the concentration of sodium carbonate is 0.3 to 0.5 mM, preferably 0.4 mM mM.

In one or more embodiments, in the step (2), the volume ratio of the liquid A to the liquid B is (0.8-1.2): 1, preferably 1:1.

In one or more embodiments, in the step (2), the volume fraction of ethanol in the ethanol aqueous solution is 5-30%, preferably 25%.

In one or more embodiments, in the step (2), the volume ratio of the solution A to the ethanol aqueous solution is (0.4-0.6): 1, preferably 0.5:1.

In one or more embodiments, in the step (2), the stirring speed is 1000-3000 r/min, and the stirring time is 2-6 h. The high-speed stirring can lead the reaction process to be more uniform and inhibit the growth and agglomeration of crystal nuclei.

In one or more embodiments, in the step (2), the temperature of the reaction system in the adding process and the stirring process of the liquid A and the liquid B is controlled to be 5-10 ℃. Nucleation at low temperatures can further inhibit the growth rate of the grains.

In one or more embodiments, in the step (2), the pH of the reaction system is controlled to be 9 to 11, preferably 10, during the addition of the liquid a and the liquid B and during the stirring. The pH is limited, so that Ni ²⁺ and Fe ³⁺ can be completely precipitated, unnecessary heterophase generation can be avoided, meanwhile, the reasonable pH can inhibit the Walder ripening effect, and the catalyst is maintained at a limited size.

In one or more embodiments, in the step (3), the aging temperature is 60-90 ℃ and the aging time is 12-24 hours. Under the limited conditions, the crystal grows with aging, so that the NiFe-LDH crystallinity is better.

In one or more embodiments, in step (4), the formamide solution has a volume fraction of formamide of 25 to 55%, preferably 50%. The formamide is capable of exfoliating layered NiFe-LDHs into nano-sheet NiFe LDHs.

In one or more embodiments, in the step (4), the power of the ultrasound is 400-500W, preferably 450W, and the time of the ultrasound reaction is 15-45 min, preferably 30 min.

In one or more embodiments, in the step (3), the washing is performed 3 to 5 times with water.

In one or more embodiments, in the step (4), the washing mode is that water and ethanol are sequentially washed for 3-5 times.

In a second aspect, the invention provides an application of the ultrathin ferronickel layered double hydroxide prepared by the preparation method in the first aspect in catalytic electrolysis of water to prepare hydrogen.

In a third aspect of the present invention, there is provided an oxygen evolution electrode comprising a nickel felt as a substrate coated with a catalyst coating;

the catalyst in the catalyst coating comprises the ultrathin ferronickel layered double hydroxide prepared by the preparation method in the first aspect.

In a fourth aspect of the present invention, there is provided a method for producing an oxygen evolution electrode according to the third aspect, comprising the steps of:

Uniformly mixing the ultrathin ferronickel layered double hydroxide prepared by the preparation method in the first aspect with isopropanol, water and a polymerization solution to obtain catalyst slurry;

spraying catalyst slurry on the upper surface of the first polytetrafluoroethylene plate to form a catalyst coating;

sequentially laminating and placing the pretreated nickel felt and a second polytetrafluoroethylene plate on the upper surface of the catalyst coating;

and hot-pressing the laminated first polytetrafluoroethylene plate, the catalyst coating, the nickel felt and the second polytetrafluoroethylene plate to obtain the oxygen evolution electrode.

In one or more embodiments, the polymerization solution is a polytetrafluoroethylene emulsion, and the mass fraction of Polytetrafluoroethylene (PTFE) in the polytetrafluoroethylene emulsion is 55-65%.

Preferably, the mass of polytetrafluoroethylene in the polymerization solution is 10% -20% of the mass of the catalyst.

In one or more embodiments, a method of pretreatment of a nickel felt includes:

The nickel felt is soaked in sodium hydroxide solution, washed, soaked in hydrochloric acid, washed with water and dried.

Preferably, the mass fraction of the sodium hydroxide solution is 10-30%, and the time for soaking in the sodium hydroxide solution is 60-120 min;

Preferably, the concentration of the hydrochloric acid is 0.5-1.5 mol/L, and the time for soaking in the hydrochloric acid is 5-10 min.

In one or more embodiments, the nickel felt has a porosity of 60-80%.

In one or more embodiments, the hot pressing conditions are a pressure of 5-10 MPa, a temperature of 80-150 ℃ and a time of 300-600 s.

The invention has the beneficial effects that:

(1) According to the invention, through low-temperature nucleation reaction, crystal aging growth and formamide lamellar stripping, the growth process of the catalyst crystal is regulated and controlled, and the sheet NiFe-LDH catalyst with high purity, good crystallinity and nano scale is obtained. Specifically, in the nucleation process, the reaction temperature of the solution, the pH value of the solution and the stirring rotation speed are regulated so that the NiFe-LDH is quickly nucleated at low temperature, high concentration and high rotation speed, the growth rate of NiFe-LDH crystal nuclei is restrained, meanwhile, the temperature time of crystal aging growth is limited, the crystal nuclei can slowly grow, finally the NiFe LDH catalyst with good crystallinity is obtained, the layered NiFe-LDH is stripped through formamide, the NiFe LDH lamellar structure is further separated to obtain a nano-scale lamellar structure, and the nano-scale lamellar NiFe-LDH can be obtained through the synergy of low-temperature nucleation reaction, crystal aging growth and formamide lamellar stripping.

(2) The ultrathin ferronickel layered double hydroxide is coated on the polytetrafluoroethylene plate, and then the oxygen evolution electrode is further formed by a hot-pressing transfer printing method, so that the coating has good bonding degree with a matrix, is not easy to fall off, and is suitable for industrial large-area production.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention.

FIG. 1 is an electron microscopic view of the ultrathin nickel-iron layered double hydroxide obtained in example 1;

FIG. 2 is a powder diffraction (XRD) pattern of the ultrathin nickel-iron layered double hydroxide obtained in example 1;

FIG. 3 is an electron microscopic view of the nickel iron layered double hydroxide obtained in comparative examples 1 to 5, wherein a, b, c, d and e correspond to comparative example 1, comparative example 2, comparative example 3, comparative example 4 and comparative example 5, respectively;

FIG. 4 is a schematic diagram of the hot pressing process of oxygen evolution electrodes;

FIG. 5 is a diagram of oxygen evolution electrode;

FIG. 6 is a Linear Sweep Voltammogram (LSV) of oxygen evolution electrodes prepared from the ultrathin nickel-iron layered double hydroxide obtained in example 1 and the nickel-iron layered double hydroxides obtained in comparative examples 1 to 5.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

In order to enable those skilled in the art to more clearly understand the technical scheme of the present invention, the technical scheme of the present invention will be described in detail with reference to specific embodiments.

The polytetrafluoroethylene emulsion is Japanese Dajin D-210C PTFE emulsion.

Example 1

Preparation of ultrathin ferronickel layered double hydroxide:

(1) Mixing 3.5653g nickel chloride hexahydrate and 0.6757g ferric chloride hexahydrate in 40 mL water to obtain solution A, mixing 1.696g anhydrous sodium carbonate and 1.6g sodium hydroxide in 40 mL water to obtain solution B;

(2) Pouring 20 mL ethanol into 60 mL water to form an ethanol aqueous solution, simultaneously dropwise adding the solution A and the solution B into the ethanol aqueous solution, keeping the dropwise adding speed at 0.5 mL/min, keeping the stirring speed at 1500 r/min in the dropwise adding process, keeping the original speed, continuously stirring for 3h, controlling the temperature of a reaction system in the dropwise adding process and the subsequent stirring process of the solution A and the solution B to be 5 ℃, and controlling the pH value of the reaction system in the dropwise adding process and the subsequent stirring process of the solution A and the solution B to be 10;

(3) After the stirring is completed, transferring the stirred reaction solution into a reaction kettle for ageing growth, wherein the ageing temperature is 60 ℃ and the time is 24 h;

(4) Dispersing the washed precipitate into 100mL formamide solution (formamide 50mL and water 50 mL), performing ultrasonic (450W) reaction for 30min, collecting the precipitate after the reaction, sequentially cleaning the precipitate with water and ethanol for 3-5 times, and drying (25 ℃) overnight in a vacuum environment to obtain the ultrathin ferronickel layered double hydroxide.

Fig. 1 is an electron microscope image of the ultrathin nickel-iron layered double hydroxide obtained in example 1, and it can be seen from the image that the synthesized nickel-iron layered double hydroxide has a nano sheet structure, and the thickness of the nano sheet is about 10 nm a.

Fig. 2 is a powder diffraction image of the ultrathin nickel-iron layered double hydroxide obtained in example 1, from which it can be seen that the synthesized catalyst has diffraction peaks at 11.3 °, 23.01 ° and 34.33 °, which are typical NiFe LDH structures, indicating successful synthesis of NiFe LDH catalysts.

Example 2

In comparison with example 1, the stirring rate in the nucleation in the step (2) was adjusted to 3000r/min, the stirring time was 2h, and the other conditions were exactly the same as in example 1.

The ultrathin ferronickel layered double hydroxide obtained in the embodiment is of a nano sheet structure, and the thickness of the nano sheet is about 9 nm.

Example 3

The temperature at the nucleation in the step (2) was adjusted to 10℃as compared with example 1, and the other conditions were exactly the same as in example 1.

The ultrathin ferronickel layered double hydroxide obtained in the embodiment is of a nano sheet structure, and the thickness of the nano sheet is about 12 nm.

Example 4

The pH at the nucleation in the step (2) was adjusted to 11 as compared with example 1, and the other conditions were exactly the same as in example 1.

The ultrathin ferronickel layered double hydroxide obtained in the embodiment is of a nano sheet structure, and the thickness of the nano sheet is about 8 nm.

Example 5

The temperature of aging in the step (3) was adjusted to 90℃as compared with example 1, and the other conditions were exactly the same as in example 1.

The ultrathin ferronickel layered double hydroxide obtained in the embodiment is of a nano sheet structure, and the thickness of the nano sheet is about 11 nm.

Comparative example 1

In comparison with example 1, the nucleation temperature was adjusted.

(2) Pouring 20 mL ethanol into 60 mL water to form an ethanol water solution, simultaneously dripping the solution A and the solution B into the ethanol water solution, keeping the dripping speed at 0.5 mL/min, keeping the stirring speed at 1500 r/min in the dripping process, keeping the original speed and continuously stirring for 3h after the dripping is finished, controlling the temperature of a reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 25 ℃, and controlling the pH value of the reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 10;

(4) Dispersing the washed precipitate into 100 mL formamide solution (formamide 50mL and water 50 mL), performing ultrasonic (450W) reaction for 30min, collecting the precipitate after the reaction, sequentially cleaning the precipitate with water and ethanol for 3-5 times, and drying the precipitate in a vacuum environment (25 ℃) overnight to obtain the ferronickel layered double hydroxide.

The electron microscopic image of the nickel-iron layered double hydroxide is shown in fig. 3a, and the result shows that the nickel-iron layered double hydroxide obtained in the embodiment has a nano sheet structure with a size of about 50 nm.

Comparative example 2

In comparison with example 1, the pH at nucleation was adjusted.

(2) Pouring 20 mL ethanol into 60 mL water to form an ethanol aqueous solution, simultaneously dropwise adding the solution A and the solution B into the ethanol aqueous solution, keeping the dropwise adding speed at 0.5 mL/min, keeping the stirring speed at 1500 r/min in the dropwise adding process, keeping the original speed and continuously stirring for 3h after the dropwise adding is finished, controlling the temperature of a reaction system in the dropwise adding process and the subsequent stirring process of the solution A and the solution B to be 25 ℃, and controlling the pH value of the reaction system in the dropwise adding process and the subsequent stirring process of the solution A and the solution B to be 14.

The electron microscopic image of the nickel-iron layered double hydroxide is shown in fig. 3b, and the result shows that the nickel-iron layered double hydroxide obtained in the embodiment has a nano sheet structure with a size of about 42 nm.

Comparative example 3

In comparison with example 1, the rotation speed at nucleation was adjusted.

(2) Pouring 20 mL ethanol into 60 mL water to form an ethanol water solution, simultaneously dripping the solution A and the solution B into the ethanol water solution, keeping the dripping speed at 0.5 mL/min, keeping the stirring speed at 500 r/min in the dripping process, keeping the original speed continuously stirring for 3h after the dripping is finished, controlling the temperature of a reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 5 ℃, and controlling the pH value of the reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 10;

The electron microscopic image of the nickel-iron layered double hydroxide is shown in fig. 3c, and the result shows that the nickel-iron layered double hydroxide obtained in the embodiment has a nano sheet structure with a size of about 38 nm.

Comparative example 4

The temperature of aging was adjusted as compared with example 1.

(2) Pouring 20 mL ethanol into 60 mL water to form an ethanol water solution, simultaneously dripping the solution A and the solution B into the ethanol water solution, keeping the dripping speed at 0.5 mL/min, keeping the stirring speed at 1500 r/min in the dripping process, keeping the original speed and continuously stirring for 3 h after the dripping is finished, controlling the temperature of a reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 5 ℃, and controlling the pH value of the reaction system in the dripping process of the solution A and the solution B and in the subsequent stirring process to be 10;

(3) After the stirring is completed, transferring the stirred reaction solution into a reaction kettle for ageing and growing, wherein the ageing temperature is 110 ℃ and the time is 24 h;

The electron microscopic image of the nickel-iron layered double hydroxide is shown in fig. 3d, and the result shows that the nickel-iron layered double hydroxide obtained in the embodiment has a nano sheet structure with a size of about 35 nm.

Comparative example 5

In comparison with example 1, no formamide delamination was carried out.

(3) And after the ageing is finished, collecting a precipitate, sequentially cleaning the precipitate with water and ethanol for 3-5 times, and drying the precipitate in a vacuum environment (25 ℃) overnight to obtain the ferronickel layered double hydroxide.

The electron microscopic image of the nickel-iron layered double hydroxide is shown in fig. 3e, and the result shows that the nickel-iron layered double hydroxide obtained in the embodiment has a nano sheet structure with a size of about 30 nm.

Example 6

The nickel-iron layered double hydroxides prepared in example 1 and comparative examples 1 to 5 were prepared into oxygen evolution electrodes for AEM according to the schematic structure of the hot pressing process shown in fig. 4, respectively. Preparation of oxygen evolution electrode:

respectively carrying out liquid cooling bath ultrasonic treatment on the catalyst of 0.3 g, ethanol of 8 mL, water of 2 mL and polymer of 0.6 mL for 60 min at a cooling bath temperature of 5 ℃ to obtain catalyst slurry after uniform mixing;

Uniformly spraying the catalyst slurry on the upper surface of the first polytetrafluoroethylene plate by using a spraying machine (the spraying speed is 0.5 mL/min) to form a catalyst coating, wherein the area of the catalyst coating is 50 cm ², the thickness is 0.1 mm, and then airing;

Soaking a nickel felt with the diameter of 9.5 cm and the porosity of 70% into a NaOH solution with the mass fraction of 20%, soaking 60: 60min for degreasing, washing with water, soaking in 1 mol/L dilute hydrochloric acid for 10: 10 min, removing an oxide layer on the surface of the nickel felt, washing with water, and drying for later use;

And fastening the laminated first polytetrafluoroethylene plate, the catalyst coating, the nickel felt and the second polytetrafluoroethylene plate, then placing the fastened first polytetrafluoroethylene plate, the catalyst coating, the nickel felt and the second polytetrafluoroethylene plate into a hot press for hot pressing treatment, wherein the hot pressing pressure is 6 MPa, the hot pressing temperature is 100 ℃, the hot pressing time is 300 s, and then removing the first polytetrafluoroethylene plate and the second polytetrafluoroethylene plate to obtain the oxygen evolution electrode.

Comparative example 6

The ultrathin ferronickel layered double hydroxide prepared in the example 1 of 0.3 g is subjected to liquid cooling bath ultrasonic treatment of 60min with 14 mL isopropanol, 6mL of water and 0.06 mL polymer, and the temperature of the liquid cooling bath is 5 ℃, and catalyst slurry is obtained after uniform mixing;

The catalyst slurry was uniformly sprayed on the pretreated nickel felt with a spray coater (spraying speed 0.5 mL/min), without hot pressing, to obtain the oxygen evolution electrode shown in fig. 5.

Example 7

The electrode prepared in example 6 was cut into dimensions of 1 cm ×1.5× 1.5 cm (actual reaction area 1 cm ×1 cm), and the Linear Sweep Voltammograms (LSVs) of the oxygen evolution electrodes prepared by the catalysts in example 1 and comparative examples 1 to 5 were tested on electrochemical work (model Shanghai cinhua CHI 760E), respectively. The test conditions were as follows:

In the three-electrode system, the auxiliary electrode is a platinum electrode, the reference electrode is an Hg/HgO electrode (the reference solution is KOH solution of 1 mol/L), and the electrolyte is KOH solution of 1 mol/L. As can be seen from fig. 6, the polarization potential of example 1 is the lowest at the same current density, which indicates that the ultra-thin nanosheets of the catalyst synthesized in example 1 have high active sites and good electrocatalytic performance.

Example 8

The oxygen evolution electrodes prepared in example 6 and comparative example 6 were respectively subjected to stability test for a long period of time under normal temperature and pressure, the electrolyte was a KOH solution with a mass fraction of 5%, a current density of 1A/cm ², and a run time of 1500 h. The results are shown in Table 1.

TABLE 1 stability test results

The results show that the oxygen evolution electrode formed by hot pressing with the ultrathin ferronickel layered double hydroxide prepared in example 1 as a catalyst had a cell pressure of about 1.9V after 1500 h runs, and no precipitation was found in the lye tank. The nickel-iron layered double hydroxide prepared in comparative examples 1-5 is used as a catalyst, the oxygen evolution electrode formed by hot pressing and the oxygen evolution electrode formed by no hot pressing in comparative example 6 are raised in different degrees in groove pressure after 1500 h runs, and precipitates are formed in an alkali liquor tank, so that the catalyst is easy to fall off due to the fact that the particles of the catalyst are too large, meanwhile, the precipitation amount is maximum in comparative example 6, the groove pressure raising amplitude is maximum, so that the catalyst is poor in combination degree with the surface of a substrate due to the direct spraying process, the catalyst is easy to fall off and unstable in performance, the oxygen evolution electrode is formed by a hot pressing transfer printing method, the combination degree of a coating and the substrate is good, and the catalyst is not easy to fall off, and is suitable for industrial large-area production.

The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing an ultrathin nickel-iron layered bimetallic hydroxide, characterized in that the ultrathin nickel-iron layered bimetallic hydroxide has a nanosheet structure with a thickness of 8-12 nm, comprising the following steps:

(1) Dissolve nickel salt and ferric salt in water and mix well to obtain solution A; dissolve sodium carbonate and sodium hydroxide in water and mix well to obtain solution B;

(2) Add solution A and solution B to the ethanol aqueous solution at the same time and stir continuously; control the temperature of the reaction system to 5~10 ℃ during the addition of solution A and solution B and during the stirring process;

The stirring speed is 1000~3000 r/min, and the stirring time is 2~6 h;

The pH of the reaction system was controlled to be 10-11 during the addition of solutions A and B and during stirring.

(3) The stirred reaction solution is aged at a limited temperature, the precipitate is collected and washed; the aging temperature is 60~90 ℃;

(4) The washed precipitate was dispersed in formamide solution and subjected to ultrasonic reaction. After the reaction, the precipitate was collected, washed, and dried to obtain an ultrathin nickel-iron layered bimetallic hydroxide.

The volume fraction of formamide is 25-55%; during the ultrasonic reaction, the ultrasonic power is 400-500 W and the ultrasonic reaction time is 15-45 min.

2. The preparation method according to claim 1, wherein in step (1), the nickel salt is one or more of nickel chloride, nickel nitrate, nickel sulfate and nickel acetate;

In step (1), the ferric salt is one or more of ferric chloride, ferric nitrate and ferric sulfate;

In step (1), the molar ratio of nickel salt to ferric salt is (1~6):(0.2~1.5).

3. The preparation method according to claim 1, characterized in that, in step (1), the concentration of nickel salt is 0.3~0.5 mM;

In step (1), the molar ratio of sodium carbonate to sodium hydroxide is (0.2~0.6):1;

In step (1), the concentration of sodium carbonate is 0.3~0.5 mM.

4. The preparation method according to claim 1, characterized in that, in step (2), the volume ratio of liquid A to liquid B is (0.8~1.2):1;

In step (2), the volume fraction of ethanol in the aqueous ethanol solution is 5-30%;

In step (2), the volume ratio of solution A to the aqueous ethanol solution is (0.4~0.6):1.

5. The preparation method according to claim 1, characterized in that, in step (3), the aging time is 12~24 h.

6. The application of the ultrathin nickel-iron layered bimetallic hydroxide prepared by the preparation method according to any one of claims 1 to 5 in catalytic electrolysis of water to produce hydrogen.

7. An oxygen evolution electrode, characterized in that it is based on a nickel felt substrate and coated with a catalyst coating;

The catalyst in the catalyst coating includes an ultrathin nickel-iron layered bimetallic hydroxide prepared by the preparation method according to any one of claims 1 to 5.

8. The method for preparing the oxygen evolution electrode according to claim 7, characterized in that it comprises the following steps:

The ultrathin nickel-iron layered bimetallic hydroxide prepared by the preparation method according to any one of claims 1 to 5 is mixed evenly with ethanol, water and polymerization liquid to obtain a catalyst slurry.

The catalyst slurry is sprayed onto the upper surface of the first polytetrafluoroethylene plate to form a catalyst coating.

Pretreated nickel felt and a second polytetrafluoroethylene plate are stacked sequentially on the upper surface of the catalyst coating;

The first polytetrafluoroethylene plate, catalyst coating, nickel felt, and second polytetrafluoroethylene plate after being stacked are hot-pressed to obtain an oxygen evolution electrode.

9. The method for preparing the oxygen evolution electrode as described in claim 8, characterized in that the hot pressing conditions are: pressure of 5~10 MPa, temperature of 80~150 ℃, and time of 300~600 s.