Preparation method and application of hollow nanocube Mn1Fe3 PBA@NiFe LDH composite catalyst

Abstract

The application discloses a preparation method of hollow nanocube Mn1Fe3PBA@NiFe LDH composite catalyst, and the composite catalyst adopts a base material, Mn1Fe3PBA nanocubes are prepared through a solution precipitation method, NiFe LDH ball-shaped flowers are prepared through a hydrothermal method, and the Mn1Fe3PBA nanocubes and the NiFe LDH ball-shaped flowers are combined to form the Mn1Fe3PBA@NiFe LDH composite catalyst with a three-dimensional hollow nanocube structure. In addition, the application also discloses application of the hollow nanocube Mn1Fe3PBA@NiFe LDH composite catalyst prepared through the preparation method in an alkaline anode oxygen evolution reaction. In the application, the NiFe LDH provides good conductivity and a skeleton channel, the Mn1Fe3PBA provides additional sites, the combination of the two improves the electronic conductivity of the catalyst, accelerates the catalytic reaction kinetics, enhances the structural stability, improves the service life of the catalyst, reduces the required overpotential in the reaction process, and improves the overall catalytic efficiency.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysis technology, and in particular to a preparation method and application of a hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst. Background Art

[0002] With the increasing consumption of non-renewable fossil fuels and the resulting environmental degradation, the development of new energy sources has become crucial. Electrocatalysis is considered to be one of the most promising options for providing clean and renewable energy and solving global environmental pollution and energy problems. The oxygen evolution reaction (OER), as one of the half-reactions in the electrochemical water splitting process, is more energetic than the hydrogen evolution reaction (HER) due to the slow kinetics of the multi-step proton-coupled electron transfer itself. Although noble metal catalysts such as RuO2 and IrO2 have high OER activity, their limited availability and high cost hinder their widespread application. Therefore, it is urgent to explore potential oxygen evolution reaction catalysts with good catalytic activity and low cost.

[0003] To this end, people have made a lot of efforts to design and synthesize various non-precious metals and their derivatives as efficient OER electrocatalysts. Among them, NiFe LDH is the most widely used, but NiFe LDH electrocatalysts have low electronic conductivity, slow kinetics, and poor stability, which limit their application in OER. The low electronic conductivity stems from the layered structure of NiFe, and the weak connection between its layers limits the electron transfer perpendicular to the layers. Therefore, improving the interaction between the layers is an important task. This paper proposes an effective method to improve the conductivity of NiFe LDH. In addition, the contact resistance between NiFe LDH and the electrode is very large, so the selection of appropriate self-supporting electrodes is very important to eliminate the contact resistance.

[0004] Combining conventional LDHs with other active materials is a simple approach to improving their OER activity. Metal-organic frameworks (MOFs) are a new class of highly porous crystalline materials with a vast surface area, which can provide abundant electrocatalytically active metal sites and facilitate charge / mass transport. Due to their inherent advantages, including high porosity and the ability to flexibly engineer their composition and structure, transition-metal-based MOFs have emerged as promising low-cost OER catalysts. Prussian blue analogs (PBAs) are a special type of MOF that also possess the tunable metal center and porous nature of MOFs, making it easier to patch and modify their internal spatial structure. Furthermore, PBAs have recently attracted attention as OER electrocatalysts due to their water stability, porosity, crystallinity, and redox-active metal centers. PBAs not only act as OER catalytically active sites but also directly provide mass transfer channels within the 150–200 nm range. LDHs, also studied as OER catalysts, possess micrometer- to nanometer-scale mass transfer channels generated by their hydrangea structure. Especially when loaded on highly conductive nickel foam (NF) with three-dimensional porosity and well-defined internal space, the diffusion transport distance of active substances and charges can be significantly shortened and the two-phase mass transfer efficiency can be improved. Summary of the Invention

[0005] In response to the above problems, the present invention aims to provide a method for preparing a hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst to improve the efficiency of the oxygen evolution reaction and the stability of the catalyst, thereby reducing the overpotential, improving the catalytic activity and extending the service life of the electrocatalyst.

[0006] The technical solutions of the present invention are as follows:

[0007] On the one hand, the present invention provides a method for preparing a hollow nano-block Mn1Fe3PBA@NiFeLDH composite catalyst. The composite catalyst adopts a base material, prepares Mn1Fe3PBA nanocubes by a solution precipitation method, prepares NiFeLDH hydrangea by a hydrothermal method, and combines the Mn1Fe3PBA nanocubes and NiFeLDH hydrangea to form a Mn1Fe3PBA@NiFeLDH composite catalyst with a three-dimensional hollow nano-block structure.

[0008] Furthermore, the preparation of the substrate material specifically includes the following steps: 2 The nickel foam was sequentially placed in a 1.0 M hydrochloric acid solution, an acetone solution, anhydrous ethanol and deionized water for ultrasonic treatment to remove surface impurities and an oxide layer, and then placed in a vacuum drying oven at 60° C. for 30 minutes to obtain the substrate material.

[0009] Furthermore, the process of preparing Mn1Fe3PBA nanocubes by the solution precipitation method specifically includes the following steps: dissolving a divalent manganese salt in a mixed solution of deionized water and ethanol and stirring to obtain a transparent solution A, then dissolving a trivalent iron salt in deionized water and ethanol and stirring to obtain a transparent solution B; then adding PVP to the transparent solution B and stirring evenly to obtain a transparent solution C; slowly dripping the transparent solution A into the transparent solution C under vigorous stirring and stirring to obtain a mixed solution; placing the substrate material in the mixed solution and incubating at room temperature, washing and drying to obtain the Mn1Fe3PBA nanocubes.

[0010] Furthermore, the divalent manganese salt is one or more of manganese sulfate monohydrate, manganese chloride, and manganese carbonate, and the trivalent iron salt is one or more of ferric sulfate, ferric chloride, ferric nitrate, and potassium ferrocyanide.

[0011] Furthermore, the molar ratio of the manganese ions in the divalent manganese salt to the iron ions in the trivalent iron salt is 1-3:1-3.

[0012] Furthermore, the molar ratio of the manganese ions in the divalent manganese salt to the iron ions in the trivalent iron salt is 1:3.

[0013] Furthermore, the process of preparing NiFeLDH hydrangea by a hydrothermal method specifically includes the following steps: adding a nickel source, an iron source, urea and ammonium fluoride to deionized water and stirring and mixing to obtain a reaction solution; adding a base material to the reaction solution for a hydrothermal reaction; collecting the precipitated product of the hydrothermal reaction, washing and drying it to obtain NiFeLDH hydrangea.

[0014] Furthermore, the temperature of the hydrothermal reaction is 120° C., and the reaction time is 7 h.

[0015] Furthermore, the preparation of the composite catalyst specifically includes the following steps: placing NiFeLDH hydrangea into the mixed solution, incubating at room temperature to obtain black nickel foam, and washing and drying the black nickel foam to obtain the Mn1Fe3PBA nanocube@NiFeLDH composite catalyst.

[0016] On the other hand, an application of a hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst in alkaline anode oxygen evolution reaction is provided.

[0017] The beneficial effects of the present invention are:

[0018] 1. This paper proposes a novel method for preparing a Mn1Fe3 PBA@NiFe LDH composite catalyst. This method utilizes a hydrothermal method and solution precipitation method, using Ni, Fe, and Mn salts to replace traditional precious metal catalysts, thereby significantly reducing preparation costs and simplifying the preparation process. The catalyst prepared by this method is not only low-cost but also has a simple preparation process.

[0019] 2. The present invention prepares a Mn1Fe3 PBA@NiFe LDH composite catalyst with a hollow block structure by a hydrothermal method and a solution precipitation method. The catalyst uses NiFe LDH as a substrate and induces the growth of nano-cubic Mn1Fe3 PBA on the surface of NiFe LDH by a solution precipitation method, forming an electrocatalyst with excellent microstructure and catalytic performance. This catalyst not only has high conductivity, high activity and good stability, but also its unique three-dimensional (3D) hollow block structure provides a large specific surface area, ensuring sufficient exposure of adsorption sites and active sites. In alkaline media, the catalyst exhibits higher chemical stability. Thanks to the synergistic effect of the two components and the unique heterogeneous structure, the accessibility of the electrolyte to the internal active centers is improved, thereby showing excellent electrocatalytic performance in the OER reaction.

[0020] 3. The present invention also constructs an in situ dual-scale porous structure in the Mn1Fe3PBA@NiFe LDH catalyst. This structure includes Mn1Fe3PBA nanocubes, NiFe LDH hydrangeas, and nickel foam (NF) skeletons, which provide pores of hundreds of nanometers, micrometers to nanometers, and hundreds of micrometers, respectively. The successful construction of this hierarchical mass transfer channel makes the catalyst's OER performance even better, emphasizes the importance of suitable mass transfer channels, and provides potential for industrial-scale application of the Mn1Fe3PBA@NiFe LDH catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Flow chart of the preparation of the Mn1Fe3 PBA@NiFe LDH composite catalyst according to an embodiment of the present invention;

[0022] Figure 2 This is the X-ray diffraction spectrum of NiFe LDH prepared in Example 1 of the present invention;

[0023] Figure 3 X-ray diffraction spectra of Mn1Fe3 PBA and Mn1Fe3 PBA@NiFe LDH prepared in Example 1 of the present invention;

[0024] Figure 4 This is a scanning electron microscope image of the NiFe LDH prepared in Example 1 of the present invention;

[0025] Figure 5 is a scanning electron microscope image of the Mn1Fe3 PBA prepared in Example 1 of the present invention;

[0026] Figure 6 This is an energy dispersive X-ray spectrum image of Mn1Fe3 PBA prepared in Example 1 of the present invention;

[0027] Figure 7 This is a scanning electron microscope image of the Mn1Fe3 PBA@NiFe LDH prepared in Example 1 of the present invention;

[0028] Figure 8 Linear sweep voltammetry curves of Mn1Fe3 PBA, Mn2Fe2 PBA and Mn3Fe1PBA samples prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention;

[0029] Figure 9 Polarization curves of NF, Mn1Fe3 PBA, NiFe LDH and Mn1Fe3 PBA@NiFe LDH samples prepared in Example 1 of the present invention;

[0030] Figure 10 The Tafel plots of NF, Mn1Fe3 PBA, NiFe LDH and Mn1Fe3 PBA@NiFe LDH samples prepared in Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and Examples, but is not intended to limit the scope of the present invention and is only illustrative. It should be noted that, in the case of no conflict, the technical features in the embodiments and embodiments of the present application can be combined with each other. Unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The experimental methods used in the following examples are conventional methods unless otherwise specified. Materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0032] Example 1

[0033] A hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst is prepared by the following steps. The preparation flow chart is as follows: Figure 1 As shown:

[0034] (1) Preparation of base material: 1*1cm 2 The nickel foam was sequentially placed in 1.0 M hydrochloric acid solution, 1.0 M acetone solution, 1.0 M anhydrous ethanol and 1.0 M deionized water for ultrasonic treatment. After the treatment, it was placed in a vacuum drying oven at 60 ° C for 30 min.

[0035] (2) Preparation of Mn1Fe3 PBA: 1 mmol of MnSO4·H2O was dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution A. 3 mmol of K3[Fe(CN)6]·H2O was then dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution B. 2 g of PVP was then added to the transparent solution B and stirred until homogeneous to obtain a transparent solution C. Under vigorous stirring, the transparent solution A was slowly dripped into the transparent solution C and stirred for 30 min to obtain a mixed solution. A nickel foam substrate (NF) was placed in the mixed solution and incubated at room temperature for 24 h to obtain a black NF. Finally, the black NF was washed with anhydrous ethanol and dried at 60°C for 5 h to obtain Mn1Fe3 PBA nanocubes, which were designated as Mn1Fe3 PBA.

[0036] (3) Preparation of NiFe LDH: NiFe LDH was prepared by hydrothermal method. 0.096g Ni(NO3)2·6H2O, 0.189g Fe(NO3)2·9H2O, 20mmol urea and 8mmol NH4F were dissolved in 60mL deionized water and stirred at room temperature for 30 minutes. The solution was then mixed with a pre-treated 1*1cm 2 The NFs were transferred together into a 100 mL Teflon-lined reactor and hydrothermally reacted at 120°C for 7 h to obtain yellow NFs. The yellow NFs were rinsed three times with water and ethanol and dried at 60°C for 5 h to obtain NiFe LDH hydrangea.

[0037] (4) Preparation of Mn1Fe3 PBA@NiFe LDH composite catalyst: 1 mmol of MnSO4·H2O was dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution A. 3 mmol of K3[Fe(CN)6]·H2O was then dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution B. 2 g of PVP was then added to the transparent solution B and stirred until homogeneous to obtain a transparent solution C. Under vigorous stirring, the transparent solution A was slowly dripped into the transparent solution C and stirred for 30 min to obtain a mixed solution. The prepared NiFe LDH hydrangea was placed in the mixed solution and incubated at room temperature for 24 h to obtain a black NF. Finally, the black NF was washed three times with anhydrous ethanol and deionized water and dried at 60°C for 5 h to obtain the desired product, the Mn1Fe3PBA@NiFe LDH composite catalyst.

[0038] Comparative Example 1

[0039] 2 mmol of MnSO4·H2O was dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution D. 2 mmol of K3[Fe(CN)6]·H2O was then dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution E. 2 g of PVP was then added to transparent solution E and stirred until homogeneous, obtaining a transparent solution F. Under vigorous stirring, transparent solution D was slowly added dropwise to transparent solution F and stirred for 30 minutes to obtain a mixed solution. A nickel foam substrate (NF) was placed in the mixed solution and incubated at room temperature for 24 hours. Finally, the black NF was washed with anhydrous ethanol and dried at 60°C for 5 hours. The resulting product was designated Mn2Fe2PBA.

[0040] Comparative Example 2

[0041] 3 mmol of MnSO₄.H₂O was dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution G. 1 mmol of K₃[Fe(CN)₆].H₂O was then dissolved in 20 ml of deionized water and 20 ml of ethanol and stirred to obtain a transparent solution H. 2 g of PVP was then added to transparent solution B and stirred until homogeneous, obtaining a transparent solution I. Under vigorous stirring, transparent solution G was slowly added dropwise to transparent solution I and stirred for 30 minutes to obtain a mixed solution. A nickel foam substrate (NF) was placed in the mixed solution and incubated at room temperature for 24 hours. Finally, the black NF was washed with anhydrous ethanol and dried at 60°C for 5 hours. The resulting product was designated Mn₂Fe₂ PBA.

[0042] Based on the above examples, the following experiments were conducted:

[0043] 1. X-ray diffraction experiment of NiFe LDH

[0044] Taking the NiFe LDH prepared in Example 1 as an example, the NiFe LDH was subjected to X-ray diffraction (XRD) and the results were as follows: Figure 2 The phase of the catalyst was determined by XRD analysis. Figure 2 The diffraction peaks of the prepared nanostructured NiFe LDH were consistent with those of the NiFe LDH standard card (JCPDS No.40-0215), indicating that NiFe LDH was successfully synthesized on NFs.

[0045] 2. X-ray diffraction experiments of Mn1Fe3 PBA and Mn1Fe3 PBA@NiFe LDH

[0046] Taking the Mn1Fe3 PBA and Mn1Fe3 PBA@NiFe LDH prepared in Example 1 as an example, X-ray diffraction analysis was performed on Mn1Fe3 PBA and Mn1Fe3 PBA@NiFe LDH. The results are as follows: Figure 3As shown, the XRD pattern shows that after the growth of Mn1Fe3 PBA, the diffraction peak belonging to Mn1Fe3 PBA (JCPDS No.97-041-6994) appears, while the diffraction peak belonging to NiFe LDH still exists, indicating the successful formation of this heterogeneous structure.

[0047] 3. Scanning electron microscopy experiment of NiFe LDH

[0048] Taking the NiFe LDH prepared in Example 1 as an example, a scanning electron microscope (SEM) experiment was performed on the NiFe LDH. The results are as follows: Figure 4 As shown in the figure, it can be seen that NiFe LDH grows evenly on the surface of NF, presenting a uniform hydrangea-like nanosheet structure.

[0049] 4. Scanning electron microscopy experiment of Mn1Fe3 PBA

[0050] Taking the Mn1Fe3 PBA prepared in Example 1 as an example, a scanning electron microscope experiment was performed on the Mn1Fe3 PBA. The results are as follows: Figure 5 As shown in the figure, it can be seen that Mn1Fe3 PBA grows evenly on the NF surface and presents a uniform nano-square structure.

[0051] 5. X-ray energy spectrum analysis experiment of Mn1Fe3 PBA

[0052] Taking the Mn1Fe3 PBA prepared in Example 1 as an example, the Mn1Fe3 PBA was subjected to X-ray energy spectrum analysis (EDS). The results are as follows: Figure 6 As shown in the figure, its element distribution is shown in the figure. It can be found that the main elements of the catalyst are Mn, Fe, O and S, which are consistent with the raw material composition used in the preparation of the catalyst, and the element distribution is very uniform as can be observed by color.

[0053] 6. Scanning electron microscopy experiment of Mn1Fe3 PBA@NiFe LDH

[0054] Taking the Mn1Fe3 PBA@NiFe LDH prepared in Example as an example, a scanning electron microscope experiment was performed on the Mn1Fe3 PBA@NiFe LDH. The results are as follows: Figure 7As shown in the figure, after the composite, the hydrangea transforms into hollow nanocubes. The PBA grows along the lamellar structure of the LDH, ultimately transforming from a lamellar structure into stacked nanocubes. However, the nanosheets are uneven during growth, forming a hollow structure. Thus, the Mn1Fe3 PBA@NiFe LDH not only forms a nanocubic structure but also hollow defects. Considering the hundreds of micrometer-scale pores of the NF framework, a dual-scale porous structure is successfully constructed in the Mn1Fe3 PBA@NiFe LDH, enabling smooth mass transfer.

[0055] VII. Linear Sweep Voltammetry Experiments of Different PBA Samples

[0056] Taking the PBA samples prepared in Example 1, Comparative Example 1 and Comparative Example 2 as examples, linear sweep voltammetry (LSV) experiments were performed on Mn1Fe3 PBA, Mn2Fe2 PBA and Mn3Fe1 PBA, respectively. The results are shown in FIG. Figure 8 As shown in Figure 2, the effect of different molar ratios of Mn:Fe on the electrocatalytic activity of PBA samples prepared by Figure 8 It can be seen that the best OER activity is shown when the molar ratio of Mn:Fe is 1:3.

[0057] 8. Linear Sweep Voltammetry Experiments of Different Samples

[0058] Using the NF, Mn1Fe3 PBA, NiFe LDH, and Mn1Fe3 PBA@NiFe LDH prepared in Example 1 as samples, a 1.0 M KOH solution was prepared. Specifically, 16.833 g of KOH was weighed and placed in a 500 mL beaker. 300 mL of deionized water was added and ultrasonically shaken to form a homogenous solution. After preparation, the samples were placed in the 1.0 M KOH solution, and their electrochemical properties were tested using a three-electrode system using linear sweep voltammetry (LSV).

[0059] In order to explore the effect of PBA and LDH composite on the electrochemical performance of the material, LSV technique was used to compare the scanning rate of 1mV s -1 Electrochemical OER performance of the samples. OER performance was evaluated with 1 M KOH: Figure 9 Polarization curves of NF, Mn1Fe3PBA, NiFe LDH and Mn1Fe3PBA@NiFe LDH samples; Compared with NiFe LDH, Mn1Fe3PBA and NF, Mn1Fe3PBA@NiFe LDH sample showed the best OER activity, indicating that the composite of layered structure and metal organic framework can effectively improve the OER catalytic activity. Only 225mV overpotential is needed to reach 10mAcm -2This is lower than the 250 mV of NiFe LDH catalyst. Figure 10 The Tafel plots of NF, Mn1Fe3 PBA, NiFe LDH and Mn1Fe3 PBA@NiFe LDH samples are used for kinetic comparison of the catalysts. -2 The Tafel slope at 46.4 mV dec -1 , compared with NiFe LDH (60.1mV dec -1 ) has faster dynamic characteristics.

[0060] The introduction of Mn can improve the electronic conductivity and electrochemical performance of Prussian blue analogs (PBA). Studies have shown that the doping of Mn and Fe not only improves the conductivity but also activates the key H2O deprotonation step. According to Gibbs free energy calculations, the charge depletion of Mn atoms can greatly enhance the adsorption of electron-rich oxygen-containing groups on the surface, which is beneficial for the adsorption and conversion of intermediates in the OER process. The active sites (Mn, Fe and C) of Mn1Fe3 PBA can all adsorb and desorb *OOH, OH and O, thereby accelerating the conversion of intermediates and increasing the OER rate. Since Mn has a lower electronegativity than Fe, the binding strength of Mn to the adsorbed oxygen-containing intermediates is moderate, which may be due to the better OER activity. The transition metal Mn can not only act as an electronic promoter to provide electrons to the iron phase and promote the reduction of the iron system, but also act as a structural promoter to promote the dispersion of the active phase, which has the advantage of improving the reaction activity of the catalyst.

[0061] In summary, the introduction of Mn in OER can improve electronic conductivity, enhance the adsorption of oxygen-containing groups, accelerate the conversion of intermediates, reduce the overpotential, increase the theoretical overpotential of active sites, moderately bind oxygen-containing intermediates, and improve the catalyst reaction activity, which are all key factors for improving OER performance.

[0062] Mn1Fe3 PBA (manganese iron Prussian blue analogue) exhibits higher electronic conductivity. This is because the synergistic effect between different metal atoms improves electronic conductivity and increases specific surface area and electrochemical activity. Mn1Fe3 PBA can alleviate the volume effect by separating into single metal compounds during the insertion / deinsertion of sodium and potassium ions, thereby improving structural stability. Mn Fe PBA has a higher redox potential, which helps to improve the energy density of the battery. MnFe PBA has Mn 3+ / Mn 2+ and Fe 3+ / Fe 2+Two active sites participate in the redox reaction. The introduction of Mn can reduce defects in the PBA framework, thereby improving the stability of the material. MnFe PBA provides a wider operating voltage range as an anode catalyst for the oxygen evolution reaction, which is beneficial for practical applications.

[0063] In summary, MnFe PBA exhibits more advantages in electronic conductivity, structural stability, and redox potential, especially in improving OER performance and stability, MnFe PBA provides more benefits.

[0064] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst, characterized in that: The specific steps include: (1) Preparation of a base material, wherein the base material is nickel foam; (2) adding a nickel source, an iron source, urea, and ammonium fluoride into deionized water and stirring to obtain a reaction solution; adding a substrate material to the reaction solution to carry out a hydrothermal reaction; collecting a precipitate of the hydrothermal reaction, washing, and drying the precipitate to obtain a NiFe LDH hydrangea; (3) Dissolving a divalent manganese salt in a mixed solution of deionized water and ethanol and stirring to obtain a transparent solution A, then dissolving a trivalent iron salt in deionized water and ethanol and stirring to obtain a transparent solution B; then adding PVP to the transparent solution B and stirring evenly to obtain a transparent solution C; slowly dripping the transparent solution A into the transparent solution C under vigorous stirring and stirring to obtain a mixed solution; placing the NiFe LDH hydrangea prepared in step (2) into the mixed solution, incubating at room temperature to obtain black nickel foam; washing and drying the black nickel foam to obtain the Mn1Fe3 PBA nanocube@NiFe LDH composite catalyst.

2. The method for preparing the hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst according to claim 1, characterized in that: The preparation of the substrate material specifically includes the following steps: 2 The nickel foam was sequentially placed in a 1.0 M hydrochloric acid solution, an acetone solution, anhydrous ethanol and deionized water for ultrasonic treatment to remove surface impurities and an oxide layer, and then dried in a vacuum drying oven at 60° C. for 30 minutes to obtain the substrate material.

3. The method for preparing the hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst according to claim 1, characterized in that: The divalent manganese salt is one or more of manganese sulfate monohydrate, manganese chloride, and manganese carbonate, and the trivalent iron salt is one or more of ferric sulfate, ferric chloride, ferric nitrate, and potassium ferrocyanide.

4. The method for preparing the hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst according to claim 1, characterized in that: The molar ratio of the manganese ions in the divalent manganese salt to the iron ions in the trivalent iron salt is 1:

3.

5. The method for preparing the hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 120° C., and the reaction time is 7 h.

6. Use of the hollow nano-block Mn1Fe3 PBA@NiFe LDH composite catalyst as claimed in claim 1 in alkaline anode oxygen evolution reaction.

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