Preparation method and application of a heterostructured LDH / oxide water electrolysis catalyst

Abstract

This application discloses a method for preparing and applying a heterostructured LDH / oxide water electrolysis catalyst, belonging to the field of electrocatalysis. The preparation method includes the following steps: First, the cut NF (1cm*1cm*0.7mm) is ultrasonically cleaned with HCl, anhydrous ethanol, and deionized water, respectively. Then, the cleaned NF is placed in a metal ion precursor solution (Fe). 3+ Ce 3+ A certain amount of hydrogen peroxide is added dropwise to react and the product is obtained. This application prepared a spherical NiFe-LDH@CeO2 heterostructure using a simple wet chemical etching method. The catalyst preparation process is simple and inexpensive, and electrochemical tests show that the obtained catalyst has good water electrolysis performance.

Description

Technical Field

[0001] This application relates to a method for preparing and applying a heterostructured LDH / oxide water electrolysis catalyst, belonging to the field of electrocatalysis. Background Technology

[0002] To replace traditional fossil fuels, we have made tremendous efforts in developing sustainable, low-carbon energy technologies. Hydrogen is one of the most promising clean fuels among next-generation energy sources. Hydrogen (H2) produced by electrocatalytic water splitting powered by renewable energy sources has high purity and cleanliness. However, due to the slow kinetics of the oxygen evolution reaction (OER) at the anolyte, although noble metal-based materials (such as Ir and Ru) are currently the benchmark for OER electrocatalysts, their rarity and poor stability hinder their application in large-scale applications. To address this issue, considerable effort has been devoted to exploring efficient and stable non-noble metal electrocatalysts, such as transition metal (oxy) hydroxides, oxides, nitrides, phosphides, sulfides, and selenides.

[0003] Layered hydrogen hydroxides (LDHs) exhibit good electrocatalytic performance for OER. However, LDH-based OER electrocatalysts often suffer from insufficient conductivity and active sites, resulting in poor conductivity and catalytic activity. Summary of the Invention

[0004] To address the aforementioned issues, this application proposes a method for preparing and applying a heterostructured LDH / oxide water electrolysis catalyst. A spherical NiFe-LDH@CeO2 heterostructure was prepared using a simple wet chemical etching method, resulting in a simple and low-cost catalyst preparation process. Electrochemical tests show that the obtained catalyst exhibits good water electrolysis performance.

[0005] According to one aspect of this application, a method for preparing a heterostructured LDH / oxide water electrolysis catalyst is provided, comprising the following steps:

[0006] (1) The cut NF (1cm*1cm*0.7mm) was ultrasonically cleaned with HCl, anhydrous ethanol and deionized water respectively;

[0007] (2) Place the cleaned NF in a metal ion precursor solution (Fe 3+ Ce 3+ Hydrogen peroxide was added dropwise to carry out the reaction. After the reaction was completed, the product was dried under vacuum. The product obtained was a NiFe-LDH@CeO2 heterostructure.

[0008] Optionally, in step (1), the concentration of HCl is 3-6 mol / L, the amount of HCl, anhydrous ethanol, and deionized water is 10-30 mL, and the ultrasonic cleaning time is 10-30 min.

[0009] Optionally, in step (2) Fe 3+ Derived from iron salts, including ferric nitrate hexahydrate, ferric sulfate hexahydrate, or ferric chloride hexahydrate; the Ce 3+ The iron salt is derived from cerium salt, including cerium nitrate hexahydrate; the molar ratio of the iron salt to the cerium salt is (0-3):(3-0), and it is ultrasonically dissolved in 10-30 mL of deionized water, with the mass ratio of the metal salt to the water being (1.212-1.302):(10-30).

[0010] Optionally, in step (2), the amount of hydrogen peroxide is 0 to 5 mL and the reaction time is 0 to 30 min.

[0011] Optionally, the vacuum drying temperature in step (2) is 60-70℃ and the drying time is 8-14h.

[0012] According to another aspect of this application, an application of a heterostructured LDH / oxide water electrolysis catalyst is provided, wherein the catalyst is used in the water electrolysis reaction.

[0013] The beneficial effects that this application may produce include, but are not limited to:

[0014] 1. The method for preparing heterostructured LDH / oxide water electrolysis catalyst provided in this application results in a heterostructure where different phases have different band arrangements, leading to charge transfer at the interface. This is beneficial for surface electron modulation of the heterostructure. The establishment of the heterostructure not only promotes electron transfer efficiency at the interface but also helps to increase the surface active sites of the catalyst, thereby improving the conductivity and catalytic activity of the catalyst.

[0015] 2. The method for preparing the heterostructured LDH / oxide water electrolysis catalyst provided in this application directly grows the electrocatalyst on a conductive substrate, which not only avoids the use of expensive conductive polymer binders and electrode preparation, but also improves the electron transfer rate and stabilizes the working electrode. Using nickel foam as a substrate can not only solve the adhesion site problem of catalyst growth, but also improve the conductivity of the catalyst by utilizing the conductivity of nickel foam itself, because the support can improve the activity by interacting with the catalyst, or provide more contact area for the catalyst, etc.

[0016] 3. The preparation method of the heterostructured LDH / oxide water electrolysis catalyst provided in this application is simple to operate and controllable, with low raw material cost and good catalyst performance, and has the potential for industrial application. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0018] Figure 1 The electrochemical performance test results of the products obtained in Examples 1, 2, and 3 of this invention, and Comparative Examples 1-2, are shown below. Figure 1 a represents the LSV curve from the OER test. Figure 1 b is the EIS plot of the OER test. Figure 1 cd represents the LSV curve from the OER test;

[0019] Figure 2 The image shows a SEM image of the catalyst prepared in Example 1.

[0020] Figure 3 This is a TEM image of the catalyst prepared in Example 1. Detailed Implementation

[0021] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0023] Example 1

[0024] The preparation method of NiFe-LDH@CeO2 / NF includes the following steps:

[0025] (1) Cut NF (1cm*1cm*0.7mm) was ultrasonically cleaned for 10min each with 20mL of 6M HCl, anhydrous ethanol and deionized water to remove impurities and oxide layer on the surface of NF.

[0026] (2) Then, the cleaned NF was placed in a metal ion precursor solution. 0.808 g of ferric nitrate nonahydrate and 0.434 g of cerium nitrate hexahydrate were dissolved in 20 mL of deionized water to prepare the metal ion precursor solution. 2 mL of hydrogen peroxide (30 wt%) was added dropwise to react. The entire etching reaction was strictly controlled to a reaction time of 5 min to prepare NiFe-LDH@CeO2 / NF. The NF was dried in a vacuum oven at 70 °C for 12 h.

[0027] Example 2

[0028] The preparation method of NiFe-LDH / NF includes the following steps:

[0029] (1) Cut NF (1cm*1cm*0.7mm) was ultrasonically cleaned for 10min each with 20mL of 6M HCl, anhydrous ethanol and deionized water to remove impurities and oxide layer on the surface of NF.

[0030] (2) Then, the cleaned NF was placed in a metal ion precursor solution. 1.212g of ferric nitrate nonahydrate was dissolved in 20mL of deionized water to prepare the metal ion precursor solution. 2mL of hydrogen peroxide (30wt%) was added dropwise to react. The entire etching reaction was strictly controlled to a reaction time of 5min to prepare NiFe-LDH / NF. The NF was dried in a vacuum oven at 70℃ for 12h.

[0031] Example 3

[0032] The preparation method of CeO2 / NF includes the following steps:

[0033] (1) Cut NF (1cm*1cm*0.7mm) was ultrasonically cleaned for 10min each with 20mL of 6M HCl, anhydrous ethanol and deionized water to remove impurities and oxide layer on the surface of NF.

[0034] (2) Then, the cleaned NF was placed in a metal ion precursor solution. 1.302g of cerium nitrate hexahydrate was dissolved in 20mL of deionized water to prepare a metal ion precursor solution. 2mL of hydrogen peroxide (30wt%) was added dropwise to react. The entire etching reaction was strictly controlled to a reaction time of 5min to prepare CeO2 / NF. The NF was dried in a vacuum oven at 70℃ for 12h.

[0035] Comparative Example 1

[0036] The difference between Comparative Example 1 and Example 1 is that in step (2), 2 mL of hydrogen peroxide (30 wt%) was added to react, and the reaction time of the entire etching reaction was strictly controlled to be 1 min, 10 min and 15 min respectively.

[0037] Comparative Example 2

[0038] The difference between Comparative Example 2 and Example 1 is that in step (2), 0.808g of ferric nitrate nonahydrate and 0.434g of cerium nitrate hexahydrate are replaced with 0.606g of ferric nitrate nonahydrate and 0.651g of cerium nitrate hexahydrate, 0.404g of ferric nitrate nonahydrate and 0.868g of cerium nitrate hexahydrate, and the total amount of metal substances is controlled to be 3 mmol.

[0039] Experimental Example

[0040] The products obtained in Examples 1-3 and Comparative Examples 1-2 were used as catalysts in a 1.0 M KOH solution for water electrolysis and oxygen evolution tests. Electrochemical measurements were performed on an electrochemical workstation (CHI750E) using a standard three-electrode system, with the Hg / HgO electrode as the reference electrode, the graphite electrode as the counter electrode, and the products prepared in Examples 1 and 2 and Comparative Examples 1-2 as the working electrode (geometric area 1 cm × 1 cm). Linear sweep voltammetry (LSV) was used in the 1.0 M KOH solution at a scan rate of 5 mV s⁻¹, as shown in formula E. vs.RHE =E vs.Hg / HgO The potential was calculated using +0.059×pH+0.098, and the potential of the reversible hydrogen electrode (RHE) was also calculated. Electrochemical stability was tested over 50 hours using iT curves at an external voltage of 1.64V.

[0041] See results Figure 1 .

[0042] Figure 1 -a represents the OER performance of Examples 1, 2, 3, and NF. It can be seen that NiFe-LDH@CeO2 / NF has the lowest overpotential at a current density of 100 mA cm⁻¹. -2 At that time, the oxygen evolution overpotential of the material was 250mV.

[0043] Figure 1 The results show that in the OER test, the NiFe-LDH@CeO2 / NF composite material has the lowest internal resistance compared to NiFe-LDH / NF, CeO2 / NF composite material, and NF. This is beneficial for reducing the polarization phenomenon of the catalyst during the catalytic process and can effectively reduce the overpotential of the catalyst during the catalytic process.

[0044] Figure 1 -c represents the OER performance of Example 1 and Comparative Example 1. Figure 1 -d represents the OER performance of Example 1, Example 2, and Comparative Example 2.

[0045] Figure 2 This is a scanning electron microscope (SEM) image of the NiFe-LDH@CeO2 / NF electrode sample. The SEM images clearly show that the NiFe-LDH@CeO2 / NF catalyst has a morphology of sheet-like structures arranged into spherical shapes, with near-spherical nanoparticles uniformly loaded on the NF substrate.

[0046] from Figure 3 It can be seen that NiFe-LDH@CeO2 / NF exhibits a structure composed of thin nanosheets. The lattice spacings of 0.23 and 0.305 nm found in the HRTEM image are attributed to the (015) crystal plane of NiFe-LDH and the (111) crystal plane of CeO2, respectively.

[0047] The results above show that this application, by preparing LDH / oxide heterostructures in situ using a rapid etching method, exhibits low internal resistance under alkaline conditions during OER testing. This effectively reduces polarization during electrocatalysis, resulting in a lower overpotential for the catalyst. Furthermore, the preparation process is simple and efficient, overcoming the drawbacks of complex and time-consuming catalyst preparation processes.

[0048] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing a heterostructured LDH / oxide water electrolysis catalyst, characterized in that, Includes the following steps: (1) The cut 1cm*1cm*0.7mm NF was ultrasonically cleaned with HCl, anhydrous ethanol and deionized water respectively; (2) Place the cleaned NF in the metal ion Fe 3+ Ce 3+ Hydrogen peroxide was added dropwise to the precursor solution to initiate the reaction. After the reaction was complete, the product was dried under vacuum to obtain NiFe-LDH@CeO2 / NF, Fe 3+ From iron salts, Ce 3+ The reaction is derived from cerium salt, wherein the molar ratio of iron salt to cerium salt is (2~3):(3~1), the amount of hydrogen peroxide is 2~5 mL, and the reaction time is 5~30 min.

2. The preparation method of the heterostructured LDH / oxide water electrolysis catalyst according to claim 1, characterized in that, In step (1), the concentration of HCl is 3~6 mol / L, the amount of HCl, anhydrous ethanol and deionized water is 10~30 mL, and the ultrasonic cleaning time is 10~30 min.

3. The preparation method of the heterostructured LDH / oxide water electrolysis catalyst according to claim 1, characterized in that, Fe in step (2) 3+ Derived from iron salts, including ferric nitrate hexahydrate, ferric sulfate hexahydrate, or ferric chloride hexahydrate; the Ce 3+ Derived from cerium salts, including cerium nitrate hexahydrate; ultrasonically dissolved in 10-30 mL of deionized water, with a mass ratio of metal salt to water of (1.212-1.302):(10-30).

4. The method for preparing the heterostructured LDH / oxide water electrolysis catalyst according to claim 1, characterized in that, In step (2), the vacuum drying temperature is 60-70℃ and the drying time is 8-14h.

5. The method for preparing the heterostructured LDH / oxide water electrolysis catalyst according to any one of claims 1 to 4, characterized in that, The catalyst is used in the water electrolysis reaction.

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