Preparation method and application of heterostructure LDH / oxide electrolyzed water catalyst

Abstract

The invention discloses a preparation method and application of a heterostructure LDH / oxide electrolyzed water catalyst, and belongs to the field of electrocatalyst.The preparation method comprises the following steps that firstly, cut NF (1 cm * 1 cm * 0.7 mm) is subjected to ultrasonic cleaning with HCl, absolute ethyl alcohol and deionized water, then the cleaned NF is placed in a metal ion precursor solution (Fe < 3 + > and Ce < 3 + >), and the metal ion precursor solution (Fe < 3 + > and Ce < 3 + >) is obtained; dropwise adding a certain amount of hydrogen peroxide for reaction to obtain a product. The spherical NiFe-LDH-CeO2 heterostructure is prepared through a simple wet chemical etching method, the preparation process of the catalyst is simple, the cost is low, and an electrochemical test shows that the obtained catalyst is good in water electrolysis effect.

Description

Technical Field

[0001] The present application relates to a preparation method and application of a heterogeneous structure LDH / oxide water electrolysis catalyst, belonging to the field of electrocatalysis. Background Art

[0002] In order to replace traditional fossil fuels, we have made great efforts to develop sustainable and low-carbon emission energy technologies. Hydrogen is one of the most promising clean fuels for next-generation energy. Hydrogen (H2) produced by electrocatalytic water splitting powered by renewable energy is of high purity and cleanliness. Due to the slow kinetics of the oxygen evolution reaction (OER) on the anode. Although noble metal-based (such as Ir and Ru) materials are currently the benchmark for OER electrocatalysts, their rarity and poor stability hinder their use in large-scale applications. To address this issue, considerable efforts have been spent on exploring efficient and stable non-noble metal electrocatalysts such as transition metal (oxy)hydroxides, oxides, nitrides, phosphides, sulfides and selenides.

[0003] Layered double hydroxides (LDHs) exhibit promising electrocatalytic performance for OER. However, LDH-based OER electrocatalysts often have insufficient electrical conductivity and active sites, resulting in poor conductivity and catalytic activity. Summary of the invention

[0004] In order to solve the above problems, this application proposes a preparation method and application of a heterostructured LDH / oxide water electrolysis catalyst. A spherical NiFe-LDH@CeO2 heterostructure is prepared by a simple wet chemical etching method, which makes the catalyst preparation process simple and low-cost. Electrochemical tests show that the obtained catalyst has a good effect on water electrolysis.

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

[0006] (1) The cut NF (1 cm*1 cm*0.7 mm) 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 react, and vacuum drying was performed after the reaction was completed. The obtained product was a NiFe-LDH@CeO2 heterostructure.

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

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

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

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

[0012] According to another aspect of the present application, an application of a heterostructured LDH / oxide water electrolysis catalyst is provided, and the catalyst is applied to a water electrolysis reaction.

[0013] The beneficial effects of this application include but are not limited to:

[0014] 1. The preparation method of the heterostructure LDH / oxide water electrolysis catalyst provided in the present application, the obtained heterostructure makes the energy band arrangement of different phases different, which will lead to charge transfer at the interface, which is conducive to the surface electron modulation of the heterostructure. The establishment of the heterostructure not only promotes the efficiency of electron transfer at the interface, but also helps to increase the surface active sites of the catalysis, and improve the conductivity and catalytic activity of the catalyst.

[0015] 2. The preparation method of the heterogeneous structure LDH / oxide water electrolysis catalyst provided in the present application directly grows the electrocatalyst on a conductive substrate, which not only avoids the use of expensive conductive polymer adhesives and the preparation of electrodes, but also improves the electron transfer rate and stabilizes the working electrode; using nickel foam as the substrate can not only solve the attachment site of catalyst growth, but also improve the conductivity of the catalyst with the help of the conductivity of nickel foam itself, because the carrier can improve the activity by interacting with the catalyst, or provide more contact area for the catalyst.

[0016] 3. The preparation method of the heterogeneous structure LDH / oxide water electrolysis catalyst provided in this application has a simple and controllable preparation process, low raw material cost, good catalyst performance, and has the potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

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

[0019] Figure 2 This is the SEM image of the catalyst prepared in Example 1;

[0020] Figure 3 This is the TEM image of the catalyst prepared in Example 1. DETAILED DESCRIPTION

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

[0022] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in this patent are for demonstration purposes only.

[0023] Example 1

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

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

[0026] (2) The cleaned NF was then 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 a metal ion precursor solution. 2 mL of hydrogen peroxide (30 wt%) was added dropwise to react. The entire etching reaction was strictly controlled to have a reaction time of 5 min to prepare NiFe-LDH@CeO2 / NF, and the product was dried in a vacuum oven at 70 °C for 12 h.

[0027] Example 2

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

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

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

[0031] Example 3

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

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

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

[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 %) is added dropwise for reaction, and the reaction time of the entire etching reaction is 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), 0.808 g of ferric nitrate nonahydrate and 0.434 g of cerium nitrate hexahydrate are replaced by 0.606 g of ferric nitrate nonahydrate and 0.651 g of cerium nitrate hexahydrate, 0.404 g of ferric nitrate nonahydrate and 0.868 g of cerium nitrate hexahydrate, and the amount of total metal substances is controlled to be 3 mmol.

[0039] Experimental example

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

[0041] Results Figure 1 .

[0042] Figure 1 -a is 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 -2 The oxygen evolution overpotential of the material is 250mV.

[0043] Figure 1 -b The results show that in the OER test, the NiFe-LDH@CeO2 / NF composite material has the smallest internal resistance compared with NiFe-LDH / NF, CeO2 / NF composite material, and NF, which is beneficial to 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 is the OER performance of Example 1 and Comparative Example 1, Figure 1 -d is the OER performance of Example 1, Example 2, and Comparative Example 2.

[0045] Figure 2 This is a scanning electron microscope image of the NiFe-LDH@CeO2 / NF electrode sample. From the SEM image, it can be clearly seen that the morphology of the NiFe-LDH@CeO2 / NF catalyst is a spherical combination of sheets, and the nearly spherical nanoparticles are uniformly loaded on the NF substrate.

[0046] from Figure 3 It can be seen that NiFe-LDH@CeO2 / NF presents a structure composed of thin nanosheets. The lattice spacing 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] From the above results, it can be seen that the present application uses a rapid etching method to in-situ prepare LDH / oxide heterostructures, and performs OER tests under alkaline conditions, showing a small internal resistance, which can effectively reduce the polarization phenomenon during the electrocatalytic process, so that the catalyst exhibits a lower overpotential during the catalytic process. At the same time, the preparation process of the present application is simple and efficient, which solves the shortcomings of complex catalyst preparation process and long cycle.

[0048] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A method for preparing a heterogeneous structure LDH / oxide water electrolysis catalyst, characterized in that: The following steps are involved: (1) The cut NF (1 cm*1 cm*0.7 mm) was ultrasonically cleaned with HCl, anhydrous ethanol, and deionized water respectively; (2) Place the cleaned NF in a metal ion precursor solution (Fe 3+ 、Ce 3+ ), hydrogen peroxide was added dropwise to react, and vacuum drying was performed after the reaction was completed. The obtained product was a NiFe-LDH@CeO2 heterostructure.

2. The method for preparing 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 amounts of HCl, anhydrous ethanol and deionized water are 10-30 mL, and the ultrasonic cleaning time is 10-30 min.

3. The method for preparing the heterogeneous structure LDH / oxide water electrolysis catalyst according to claim 1, characterized in that: In step (2), Fe 3+ From iron salts, including iron nitrate hexahydrate, iron sulfate hexahydrate or iron chloride hexahydrate; the Ce 3+ The cerium salt includes hexahydrated cerium nitrate; the molar ratio of the iron salt to the cerium salt is (0-3): (3-0), and the iron salt is ultrasonically dissolved in 10-30 mL of deionized water, and the mass ratio of the metal salt to water is (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 the step (2), the amount of hydrogen peroxide is 0 to 5 mL, and the reaction time is 0 to 30 min.

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

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

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