Preparation method of annealing-induced NO3-intercalated Ni-based LDH-coated FeOHSO4 oxygen evolution catalytic electrode

Abstract

The invention discloses a preparation method of an annealing-induced NO3-intercalated Ni-based LDH-coated FeOHSO4 oxygen evolution catalytic electrode, and belongs to the technical field of oxygen evolution catalytic electrodes. The method comprises the following steps: carrying out ultrasonic cleaning on foamed nickel by adopting an HCl solution, washing and drying to obtain pretreated foamed nickel; the pretreated foamed nickel is soaked in a nitrate solution, then taken out and annealed, and a NiX LDH electrode is obtained; and soaking the NiX LDH electrode in a ferrous sulfate solution, taking out the NiX LDH electrode, washing the NiX LDH electrode, and drying the NiX LDH electrode to obtain the NiFe LDH-coated FeOHSO4 electrode. The Ni-based LDH catalytic electrode is obtained on the surface of the electrode through dipping, heat preservation and annealing, LDH has a large specific surface area and can expose more active sites and accelerate adsorption and conversion of active substances, and in-situ growth can reduce interface resistance and accelerate electron transmission, so that the conductivity of the electrode is improved, and the oxygen evolution performance of the electrode is improved; the Ni-based LDH-coated FeOHSO4 composite catalytic electrode is prepared by two-step impregnation, and a heterogeneous interface promotes generation of a built-in electric field due to the difference of Fermi levels, accelerates directional migration of electrons at the interface and improves oxygen evolution performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oxygen evolution catalytic electrode, and particularly relates to an annealing-induced NO 3- The application belongs to the technical field of oxygen evolution catalytic electrode, and particularly relates to an annealing-induced NO BACKGROUND

[0002] With the rapid growth of global demand for clean energy, water electrolysis as a sustainable green hydrogen production technology has attracted widespread attention. Through water electrolysis, electrical energy can be converted into chemical energy stored in hydrogen gas, and hydrogen gas combustion only generates water, the whole process is zero carbon emission, which is an important part of building future clean energy system. In the process of water electrolysis, oxygen evolution reaction (OER) occurs at the anode, and catalyst plays a crucial role in OER reaction, which can reduce the activation energy of the reaction, accelerate the reaction rate and improve the efficiency of water electrolysis. At present, although noble metal catalysts (such as Ru, Ir, etc.) show excellent catalytic activity for OER, but due to their scarcity and high cost, it seriously limits the large-scale application. Therefore, developing efficient, low-cost and stable non-noble metal heterogeneous bifunctional catalysts has become a research hotspot and key challenge in the field of water electrolysis.

[0003] Heterogeneous catalysts can achieve efficient oxygen evolution reaction, compared with single-function catalysts and traditional noble metal catalysts, have the following significant advantages: 1) cost and integration advantage: reduce or eliminate the use of noble metal, reduce cost, at the same time can realize HER and OER on the same electrode, simplify the structure of water electrolysis device, reduce the complexity and cost of the system, avoid the compatibility problem that may occur when using two single-function catalysts, which is conducive to improving energy conversion efficiency. 2) Synergistic effect: by reasonably designing the composition and structure of the catalyst, different active sites or components can produce synergistic effect, optimize the adsorption and desorption performance of reaction intermediates, thereby significantly improve the overall catalytic activity. 3) High stability: heterogeneous catalysts usually have good physical and chemical stability, can maintain the relative stability of structure and performance under the harsh conditions of water electrolysis (such as high potential, strong acid and alkali environment), prolong the service life and reduce the long-term operation cost.

[0004] However, there are still many difficulties in developing high-performance heterogeneous bifunctional catalysts at present, such as how to accurately control the active sites on the catalyst surface and achieve good balance between the two reactions, how to optimize the electronic structure of the material, enhance the interaction between the catalyst and the reaction intermediates, and improve the charge transport efficiency, how to improve the corrosion resistance, structural stability and long-term cycle stability of the material, and how to find a process that is simple in process, simple in equipment, simple in operation, low in cost and can realize large-scale batch production, which is one of the key factors to promote the practical application of heterogeneous bifunctional catalysts. SUMMARY

[0005] Therefore, the present application aims to provide an annealing-induced NO 3- The preparation method of the intercalation Ni-based LDH@FeOHSO4 oxygen evolution catalytic electrode has unique material design, preparation method and structure regulation, and can realize high activity, high stability and low cost of water electrolysis performance, thereby providing a new idea and way for large-scale application of hydrogen production by water electrolysis.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: The present application provides an annealing-induced NO 3- The preparation method of the intercalation Ni-based LDH@FeOHSO4 oxygen evolution catalytic electrode comprises the following preparation steps: S1. The foam nickel is cleaned, washed and dried by using HCl solution to obtain pretreated foam nickel; S2. The pretreated foam nickel is soaked in a nitrate solution, and then a NiX LDH electrode is obtained by annealing after taking out; S3. The NiX LDH electrode is soaked in a ferrous sulfate solution, and then a NiFe LDH@FeOHSO4 electrode is obtained by washing and drying after taking out.

[0007] Preferably, the concentration of the HCl solution in S1 is 1-3 mol / L; the ultrasonic time is 15-20 min, and the ultrasonic temperature is 40-50 DEG C; and the cleaning times are 3-5 times.

[0008] Preferably, the nitrate solution in S2 is Fe(NO3)3 solution or Co(NO3)2 solution.

[0009] Preferably, the concentration of the nitrate solution is 0.05-0.2 mol / L.

[0010] Preferably, the soaking time in S2 is 10-15 s.

[0011] Preferably, the annealing temperature in S2 is 150-250 DEG C, and the time is 90-150 min.

[0012] In the present application, the Ni-based LDH catalyst is prepared in situ on the surface of the nickel electrode by the method of annealing the nickel electrode immersed in the nitrate solution, and the preparation of the in-situ electrode of LDH can reduce the charge transfer resistance and improve the catalytic performance, and the preparation process is simple and easy to operate, and the use cost is low. By using the layered structure of LDH, more new active sites are exposed, the adsorption and activation capacity of the reactants is enhanced, and the oxygen evolution catalytic efficiency of the electrode is improved.

[0013] Preferably, the concentration of the ferrous sulfate in S3 is 0.2-0.8 mol / L.

[0014] Preferably, the soaking time in S3 is 1-5h.

[0015] Preferably, the drying temperature in S3 is 60-80 ℃, and the drying time is 12-24h.

[0016] In the present application, FeOHSO4 has a different work function from Ni-based LDH. By constructing FeOHSO4 catalyst on the surface of Ni-based LDH, the difference in two-phase Fermi energy is utilized to generate built-in electric field, accelerate electron migration and surface charge transmission, and accelerate the adsorption and oxidation of OH - .

[0017] At least the following beneficial technical effects are contained: The present application utilizes the method of nickel electrode immersion in nitrate annealing to realize in-situ chemical reaction on the surface of nickel electrode, obtain Ni-based LDH catalytic electrode, significantly reduce the interface resistance, and at the same time, through the way of secondary soaking in ferrous sulfate solution, obtain a layer of FeOHSO4 on the surface of NiX LDH, through the construction of two-phase interface contact, realize the establishment of built-in electric field, promote the interface transfer of electrons and the adsorption and conversion of surface OH - .

[0018] The present application obtains a composite catalytic electrode through one-step immersion annealing and two-step immersion reaction, which is simple to operate, easy to repeat, excellent in performance, and has good characteristics suitable for industrial large-scale production. This means that the present application can be stably applied in industrial production environment, meet the needs of large-scale and batch production of electrodes, and provide strong technical support for the scale development of related industries. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 SEM image of the NiFe LDH@FeOHSO4 electrode prepared in Example 1; Figure 2 SEM image of the NiFe LDH electrode prepared in Example 2; Figure 3 SEM image of the NiCo LDH@FeOHSO4 electrode prepared in Example 5; Figure 4 SEM image of the NiCo LDH electrode prepared in Example 6; Figure 5 Polarization curve diagram of catalyst oxygen evolution in Example 1, 5 and Comparative Example 7. DETAILED DESCRIPTION

[0020] The following detailed description of various exemplary embodiments of the application should not be considered to be limiting of the application, but rather a description of certain aspects, features, and embodiments of the application.

[0021] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Additionally, for a range of values of a parameter, unless otherwise stated, each intervening value of the parameter is also specifically included within the scope of the present application. The intervening values of the parameter are combined with a stated value of the parameter in range form. These are only exemplary of the various preferred embodiments and are not intended to be limiting of the application. Additionally, other variations that are within the spirit of the application will occur to those skilled in the art upon consideration of this description. Accordingly, the application is not limited to the specific embodiments described herein, but is intended to cover all modifications and variations of this description which are within the scope of the application.

[0022] 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 application belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All patents, patent applications, publications, and descriptions mentioned herein are incorporated by reference to the extent allowed by law. In the case of conflict between the descriptions in the specification and the incorporated literature, the specification shall control.

[0023] Various modifications and variations of the described embodiments of the application will be apparent to those skilled in the art without departing from the scope or spirit of the application. Although the application has been described in connection with specific embodiments thereof, it will be understood that the application is capable of further modifications. This patent application is intended to cover any and all variations using like elements to perform similar functions described herein.

[0024] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0025] As used herein, the terms "room temperature", "ambient temperature" are intended to mean 25 ± 2 °C, unless otherwise specified.

[0026] The raw materials or instruments used in the following examples of the present application are commercially available, unless otherwise specified.

[0027] The preparation methods of the examples and comparative examples are shown as follows: An annealing-induced NO 3- The specific steps of the intercalated Ni-based LDH@FeOHSO4 oxygen evolution catalytic electrode are as follows: (1) The untreated foam nickel is placed in a 2 mol / L HCl solution for ultrasonic cleaning, and after being taken out, it is cleaned with deionized water and dried to obtain pretreated foam nickel; the ultrasonic time is 18 min, the ultrasonic temperature is 45 °C, and the cleaning is performed 4 times.

[0028] (2) Under room temperature and stirring conditions, ferric nitrate is dissolved in deionized water to obtain a uniform ferric nitrate solution; the concentration of Fe(NO3)3 is 0.05~0.2 mol / L.

[0029] (3) Immerse the pretreated nickel foam in ferric nitrate solution for 15 s, take it out and put it in a drying oven for annealing at 150~250 ℃ for 60~120 min to obtain NiX LDH electrode in situ on the surface of nickel foam.

[0030] (4) Immerse the NiX LDH electrode in a 0.2~0.8 mol / L ferrous sulfate solution for 1~5h, then take it out, rinse it with deionized water, and dry it at 70 ℃ for 18h to obtain NiX LDH@FeOHSO4.

[0031] The specific parameters for each embodiment are shown in Table 1.

[0032] Table 1

[0033] The specific parameters for each comparative example are shown in Table 2.

[0034] Table 2

[0035] SEM characterization: SEM images of Ni-based LDH and composite catalytic electrodes, as shown in... Figures 1-4 As shown, Figure 1 SEM image of the NiFe LDH@FeOHSO4 electrode prepared in Example 1; Figure 2 SEM image of the NiFe LDH electrode prepared in Example 2; Figure 3 SEM image of the NiCo LDH@FeOHSO4 electrode prepared in Example 5; Figure 4 The image shows a SEM image of the NiCo LDH electrode prepared in Example 6. Meanwhile, all samples from other examples exhibit a distinct layered structure, indicating the successful preparation of the bimetallic hydroxide LDH. Before composite preparation, the LDH layered structure was clearly visible, resembling a foam network. Even after composite preparation, a distinct layered structure was still observed. FeOHSO4 exhibits a coating structure on the Ni-based LDH, further demonstrating the successful preparation of the composite catalyst.

[0036] Electrochemical performance characterization: A 1.0M KOH solution was prepared. A graphite electrode was used as the counter electrode, and an Hg / HgO electrode was used as the reference electrode. The catalytic electrodes obtained in Examples 1-8 and Comparative Examples 1-7 were used as the working electrodes. The electrodes were connected to an electrochemical workstation to test the electrochemical performance of hydrogen evolution. Before the test, the electrodes were activated and the impedance was measured to facilitate subsequent IR compensation. After the test, the reversible hydrogen electrode was calibrated. Taking the catalysts prepared in Examples 1, 5 and Comparative Example 7 as examples, the oxygen evolution polarization curves are as follows: Figure 5 As shown.

[0037] The NiFeLDH@FeOHSO4 electrode prepared in Example 1 exhibits the advantage of a layered structure. The NiFeLDH layered structure provides a high specific surface area, allowing for the introduction of more new active sites. Simultaneously, the in-situ growth structure effectively reduces interfacial resistance, accelerates mass and charge transfer, and enhances the electrode's conductivity and catalytic activity. The FeOHSO4 second phase, with a different work function than the NiLDH, results in different Fermi levels between the two phases, spontaneously generating a built-in electric field that promotes directional electron migration. This optimizes the adsorption, conversion, and desorption processes of hydroxide ions, reducing the overpotential of the oxygen evolution reaction, leading to a significantly superior polarization curve compared to other samples. The unique crystal structure and properties of this multiphase composite enhance the electrochemical performance, stability, and corrosion resistance of the catalytic electrode.

[0038] Example 2 shows a single NiFe LDH structure, and Example 6 shows a single FeOHSO4 phase. Both substances possess certain catalytic properties, but lack the built-in electric field, resulting in inferior performance compared to composite electrodes. Although Example 5 is also a composite NiCo LDH@FeOHSO4 electrode, the interaction between Ni and Fe forms oxygen bridges, accelerating the oxygen evolution reaction. This catalytic effect is stronger than the interaction between Ni and Co, thus the NiCo LDH@FeOHSO4 electrode's performance is somewhat weaker, but its overall performance is still superior to that of a single catalyst. In the comparative examples, excessively high or low concentrations of ferric nitrate and ferrous sulfate disrupt the LDH layered structure, potentially causing FeOHSO4 to transform into other phases, leading to changes in sample performance.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An annealing-induced NO 3- A method for preparing an intercalated Ni-based LDH@FeOHSO4 oxygen evolution catalytic electrode, characterized in that, The preparation steps include the following: S1. Pretreated nickel foam is obtained by ultrasonic cleaning, washing and drying with HCl solution; S2. The pretreated nickel foam is immersed in a nitrate solution, and then removed and annealed to obtain a NiX LDH electrode; S3. Immerse the NiX LDH electrode in ferrous sulfate solution, then remove, wash, and dry to obtain the NiFe LDH@FeOHSO4 electrode.

2. The preparation method according to claim 1, characterized in that, The concentration of HCl solution in S1 is 1~3 mol / L; the ultrasonic time is 15~20 min, the ultrasonic temperature is 40~50℃; and the number of cleaning cycles is 3~5.

3. The preparation method according to claim 1, characterized in that, The nitrate solution in S2 is either Fe(NO3)3 solution or Co(NO3)2 solution.

4. The preparation method according to claim 3, characterized in that, The concentration of the nitrate solution is 0.05~0.2 mol / L.

5. The preparation method according to claim 1, characterized in that, The soaking time in S2 is 10-15 seconds.

6. The preparation method according to claim 1, characterized in that, The annealing temperature in S2 is 150~250℃, and the time is 90~150 min.

7. The preparation method according to claim 1, characterized in that, The concentration of ferrous sulfate in S3 is 0.2~0.8 mol / L.

8. The preparation method according to claim 1, characterized in that, The soaking time in S3 is 1 to 5 hours.

9. The preparation method according to claim 1, characterized in that, The drying temperature in S3 is 60~80 ℃, and the drying time is 12~24 h.

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