CN114481199A

CN114481199A - Ternary metal layered hydroxide NiFeV-LDH and preparation method and application thereof

Info

Publication number: CN114481199A
Application number: CN202210164115.9A
Authority: CN
Inventors: 姚惠琴; 陈利红; 闫海青; 马淑兰
Original assignee: Beijing Normal University; Ningxia Medical University
Current assignee: Beijing Normal University; Ningxia Medical University
Priority date: 2022-02-22
Filing date: 2022-02-22
Publication date: 2022-05-13

Abstract

The ternary metal layered hydroxide NiFeV-LDH has a criss-cross nanosheet structure, has a larger specific surface area and more exposed active sites, is more beneficial to electron transfer and release of generated gas, has good conductivity and lower overpotential, and shows ultra-strong stability under high current density. Therefore, the ternary metal layered hydroxide NiFeV-LDH has the advantages of high activity and high stability when being applied to electrolytic water Oxygen Evolution Reaction (OER), and can realize efficient and stable catalysis of OER. In addition, the raw materials of the NiFeV-LDH are cheap and easy to obtain, and the production cost is low. The ternary metal layered hydroxide NiFeV-LDH is used in the electrolyzed water OER, and can efficiently and stably catalyze the OER. The preparation method of the ternary metal layered hydroxide NiFeV-LDH is simple, the ternary metal layered hydroxide NiFeV-LDH can be prepared by adopting a simple one-step hydrothermal synthesis method, and the raw materials are cheap and easy to obtain, so that the ternary metal layered hydroxide NiFeV-LDH can be applied to industrial production in a large scale.

Description

Ternary metal layered hydroxide NiFeV-LDH and preparation method and application thereof

Technical Field

The application relates to the technical field of preparation of catalysts for water decomposition reaction, in particular to a ternary metal layered hydroxide NiFeV-LDH, and a preparation method and application thereof.

Background

The problems of environmental pollution and resource exhaustion caused by the use of fossil fuels are becoming more serious, and the development of novel energy sources is urgently needed. Hydrogen has the advantages of high combustion value, zero pollution, recyclability and the like, and is one of the most attractive substitutes of the traditional fossil fuel. Electrolysis of water is one of the main means of obtaining hydrogen energy and can be divided into two half-reactions, namely, Oxygen Evolution Reaction (OER) occurring at the anode and Hydrogen Evolution Reaction (HER) occurring at the cathode. Compared with HER, OER has a complex reaction mechanism and a slow kinetic rate, and requires a higher potential to overcome the reaction energy barrier, resulting in a lower efficiency of the energy conversion process. Therefore, highly active catalysts are needed to overcome the reaction energy barrier of OER.

At present, noble metal materials, such as Ru and Pt-based materials, are the most effective OER catalysts, but the catalysts are expensive and have scarce resources, so that the catalysts cannot be applied in large scale. The non-noble metal OER electrocatalyst cannot keep stable under high current density, and lacks practicability. Therefore, the development of a catalyst with low cost, high activity and high stability has become a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above problems in the prior art, the present application aims to provide a ternary metal layered hydroxide NiFeV-LDH, and a preparation method and application thereof, so as to realize the advantages of low cost, high activity and high stability of the OER catalyst.

A first aspect of the application provides a method for preparing a ternary metal layered hydroxide NiFeV-LDH, comprising the steps of:

(1) pretreating foamed nickel;

(2) dissolving an iron source, a vanadium source and an alkali source in deionized water, and stirring to obtain a solution;

wherein the molar ratio A of the iron element (Fe) to the vanadium element (V) satisfies the following condition: a is more than or equal to 0.3:0.7 and less than or equal to 0.7:0.3, the ratio of the total mole number of the iron source and the vanadium source to the mole number of the alkali source is 1 (4-6), and the volume ratio of the mole number of the alkali source to the deionized water is 1 (2.5-4.6) mol/L;

(3) and (2) carrying out hydrothermal reaction on the solution and the foamed nickel obtained in the step (1) at the temperature of 100-140 ℃ for 10-14h, and after the reaction is finished, separating and drying to obtain the ternary metal layered hydroxide NiFeV-LDH.

The second aspect of the application provides a ternary metal layered hydroxide NiFeV-LDH prepared by the method provided by the first aspect of the application, which takes foamed nickel as a substrate and a nickel source, and NiFeV-LDH nanosheet material is grown in situ on the substrate through a hydrothermal synthesis method.

A third aspect of the present application provides a use of the ternary metal layered hydroxide NiFeV-LDH provided in the second aspect of the present application as a catalyst for water splitting reactions.

The ternary metal layered hydroxide NiFeV-LDH has a criss-cross nanosheet structure, has a larger specific surface area and more exposed active sites, is more favorable for electron transfer and release of generated gas, has good conductivity and lower overpotential, and shows super-strong stability under high current density. Therefore, the ternary metal layered hydroxide NiFeV-LDH has the advantages of high activity and high stability when being applied to the water electrolysis OER, and can realize high-efficiency stable catalysis of the OER. In addition, the NiFeV-LDH has cheap and easily available raw materials and low production cost. The ternary metal layered hydroxide NiFeV-LDH is used in the electrolyzed water OER, and can efficiently and stably catalyze the OER. The preparation method of the ternary metal layered hydroxide NiFeV-LDH is simple, the ternary metal layered hydroxide NiFeV-LDH can be prepared by adopting a simple one-step hydrothermal synthesis method, and the raw materials are cheap and easy to obtain, so that the ternary metal layered hydroxide NiFeV-LDH can be applied to industrial production in a large scale.

Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only one embodiment of the present application, and other embodiments can be obtained by those skilled in the art according to the drawings.

FIG. 1 is an X-ray diffraction (XRD) pattern for each of the products of examples 1-3, comparative examples 1-2;

FIG. 2 is a different electron micrograph of the product of example 2(a) is a Scanning Electron Micrograph (SEM), b is an elemental distribution, c is a Transmission Electron Micrograph (TEM), and d is a high-resolution transmission electron micrograph (HRTEM);

FIG. 3 is an X-ray photoelectron spectroscopy (XPS) chart of each of the products of example 2 and comparative examples 1-2;

FIG. 4(a) shows the respective products of example 2 and comparative examples 1-2, nickel foam and RuO₂OER polarization curve of (d);

FIG. 4(b) is an OER polarization curve for each of the products of examples 1-3 and comparative examples 1-2;

FIG. 4(c) is a graph showing the current density at 50mA cm for each of the products of examples 1 to 3 and comparative examples 1 to 2^-2And 100mA cm^-2Comparison graph of overpotential of (1);

FIG. 4(d) is a linear fit of the change in capacitance current density at a potential of 1.25V (vs RHE) versus scan rate for each of the products of example 2, comparative examples 1-2;

FIG. 4(e) is an impedance plot of each of the products of example 2, comparative examples 1-2, and nickel foam;

FIG. 5(a) is a graph of current density versus time for each of the products of example 2 and comparative examples 1-2;

FIG. 5(b) is a comparison of electrocatalytic OER polarization curves before and after the product stability test of example 2;

FIG. 5(c) is an XRD pattern before and after the product stability test of example 2;

FIG. 5(d) is SEM photographs before and after the product stability test of example 2;

FIG. 5(e) is an XPS plot of Fe 2p before and after the product stability test of example 2;

fig. 5(f) is an XPS plot of V2 p before and after the product stability test of example 2.

Detailed Description

The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in this application are within the scope of protection of this application.

(1) pretreating foamed nickel;

wherein the molar ratio A of the iron element to the vanadium element satisfies the following condition: a is more than or equal to 0.3:0.7 and less than or equal to 0.7:0.3, the ratio of the total mole number of the iron source and the vanadium source to the mole number of the alkali source is 1 (4-6), and the volume ratio of the mole number of the alkali source to the deionized water is 1 (2.5-4.6) mol/L;

The preparation method adopts a simple hydrothermal synthesis method to synthesize the ternary metal layered hydroxide NiFeV-LDH in one step. In the preparation process, the adopted production raw materials are cheap and easy to obtain, and the prepared ternary metal layered hydroxide NiFeV-LDH has low cost, high activity and high stability in OER. And the preparation method is simple to operate. Therefore, the preparation method of the application can be applied to industrial production in a large scale.

In the present application, the nickel foam in step (1) is not particularly limited as long as it satisfies the purpose of the present application, and may be selected from nickel foams (type: W60mm T1.6mm L5m, thickness of 1.6mm, pore size of 0.23mm) produced by Shuanghai trade, Inc. of Shenzhen, for example. And, the nickel foam can be added in the form of a sheet of about 1cm × 4cm, or can be added in multiple sheets at a time, thereby increasing the reaction rate.

In some embodiments of the present application, in step (1), the nickel foam is pretreated, which may specifically include the following steps: cutting the foamed nickel into sheets of about 1cm multiplied by 4cm, placing the sheets in a hydrochloric acid solution with the concentration of 1mol/L for ultrasonic cleaning for about 15min, removing NiO on the surface, respectively ultrasonic cleaning by using acetone, deionized water and absolute ethyl alcohol in sequence, and drying in vacuum to obtain the clean foamed nickel sheets.

In some embodiments of the present application, the hydrothermal reaction of step (3) may be carried out in a hydrothermal reaction kettle. The volume of the solution can be 60-90% of the volume of the hydrothermal reaction kettle. The hydrothermal reaction kettle is not particularly limited as long as the purpose of the present invention can be achieved.

It should be noted that the operation steps of the hydrothermal reaction are well known to those skilled in the art, and those skilled in the art can operate according to the relevant hydrothermal reaction parameters provided in the present application, such as the temperature, time, etc. of the hydrothermal reaction.

In some embodiments of the present application, in the step (3), when the solution reacts with the nickel foam obtained in the step (1), the amount of the nickel foam added is 1 to 3, preferably 2.

In some embodiments of the present application, after the reaction in step (3) is completed, the product obtained from the reaction is separated and dried, specifically washed with distilled water and absolute ethyl alcohol, alternatively washed with distilled water and absolute ethyl alcohol until the washing solution is colorless, and dried to obtain the ternary metal layered hydroxide NiFeV-LDH. Of course, the anhydrous ethanol may be replaced by a volatile, low-toxic organic solvent such as acetone to wash the obtained product. The solvent used for washing is not particularly limited in the present application as long as the object of the present application can be satisfied.

In some embodiments of the present application, the drying in step (3) may be drying the product obtained from the reaction at 40-50 ℃ for 10-16h to obtain the clean ternary metal layered hydroxide NiFeV-LDH. Drying in the temperature range is more beneficial to obtaining the ternary metal layered hydroxide NiFeV-LDH with high activity and high stability.

In some embodiments of the present application, the iron source is selected from iron nitrate (Fe (NO)₃)₃·9H₂O), iron sulfate, and iron chloride. The iron source is preferably Fe (NO)₃)₃·9H₂O。

In some embodiments of the present application, the source of vanadium is selected from vanadium trichloride (VCl)₃) Vanadium sulfate (V)₂(SO₄)₃) Any one of the above. The vanadium source is preferably VCl₃。

In some embodiments herein, the alkali source is selected from any one of urea, hexamethylenetetramine. The alkali source is preferably urea.

The ternary metal layered hydroxide NiFeV-LDH prepared by the preparation method of the first aspect of the application takes the foam nickel as the substrate and the nickel source, so that the conductivity of the NiFeV-LDH is improved, the NiFeV-LDH becomes a self-supporting material, the NiFeV-LDH can be directly used as an electrode, the foam nickel serving as a raw material is fully utilized, and the cost is saved; on one hand, electron transfer among metals is beneficial to enhancing OER activity, Fe plays a crucial role as an active site, and iron ions transfer electrons to vanadium ions, so that the high valence state of Fe can be stabilized, and the OER process is accelerated; on one hand, V provides chemical stabilization for an active material FeOOH formed in the OER process, so that excellent stability of the OER is realized. The ternary metal layered hydroxide NiFeV-LDH has a criss-cross nanosheet structure, has a larger specific surface area and more exposed active sites, is more favorable for electron transfer and release of generated gas, has good conductivity and lower overpotential, and shows super-strong stability under high current density. Therefore, the ternary metal layered hydroxide NiFeV-LDH has the advantages of high activity and high stability when being applied to the water electrolysis OER, and can realize high-efficiency stable catalysis of the OER. In addition, the NiFeV-LDH has cheap and easily available raw materials and low production cost.

In some embodiments of the present application, the ternary metal layered hydroxide NiFeV-LDH acts as an oxygen evolution reaction catalyst under alkaline conditions.

It is noted that "LDH" in the present application is a layered metal hydroxide.

Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "part" and "%" are based on mass.

Example 1

< preparation of ternary Metal layered hydroxide NiFeV-LDH >

Pretreating foamed nickel: cutting foamed nickel (manufacturer: Shenzhen Shuanghai trade Limited, model: W60mm T1.6mm L5m) into sheets of 1cm × 4cm, placing the sheets in hydrochloric acid solution with the concentration of 1mol/L for ultrasonic cleaning for about 15min, removing NiO on the surface, respectively ultrasonic cleaning by using acetone, deionized water and absolute ethyl alcohol in sequence, and then drying in vacuum.

Mixing Fe (NO)₃)₃·9H₂O、VCl₃And 0.601g (100mmol) of urea in 36mL of deionized water and stirred to form a clear, uniform yellow solution. Fe (NO)₃)₃·9H₂O and VCl₃The total mole number of the Fe-V catalyst is 2mmol, and the mole ratio A of the Fe and the V is 0.3: 0.7.

The solution and 2 pieces of nickel foam were transferred to a 50mL teflon stainless steel autoclave, sealed and reacted in an oven at 120 ℃ for 12 h. And after the reaction is finished, washing the nickel foam by using distilled water and absolute ethyl alcohol, and drying to obtain the NiFeV-LDH nanosheet material growing on the nickel foam in situ, namely the ternary metal layered hydroxide NiFeV-LDH.

Example 2

The procedure was repeated as in example 1 except that the molar ratio A of Fe to V was adjusted to 0.5: 0.5.

Example 3

The procedure was repeated as in example 1 except that the molar ratio A of Fe to V was adjusted to 0.7: 0.3.

Comparative example 1

The procedure was repeated as in example 1 except that the molar ratio A of Fe to V was adjusted to 0:1 to obtain a binary metal layered hydroxide NiV-LDH.

Comparative example 2

The procedure was repeated as in example 1 except that the molar ratio A of Fe to V was adjusted to 1:0 to obtain a binary metal layered hydroxide NiFe-LDH.

< structural analysis and Performance test >

Note that for convenience of description, the following diagram (&) actually indicates (&) in the diagram, for example, (a) in fig. 1, (b) in fig. 3(a) in fig. 1, and (b) in fig. 3, and so on. The aforementioned "+" represents any one of 1 to 3, and the aforementioned "&" represents any one of a to e.

XRD result analysis:

XRD analyses were performed on the NiFeV-LDH of example 2, the NiV-LDH of comparative example 1, and the NiFe-LDH of comparative example 2, and the obtained XRD patterns are shown in FIG. 1, FIG. 1(c) characterizing the NiFeV-LDH of example 2, FIG. 1(e) characterizing the NiFe-LDH of comparative example 2, and FIG. 1(a) characterizing the NiV-LDH of comparative example 1, and it can be seen that: in NiFeV-LDH, NiV-LDH, NiFe-LDH, strong diffraction peaks were observed for Ni at 44.5 °, 51.8 ° and 76.4 ° (marked "#") (corresponding to standard card JCPDF: 04-0850). For NiFeV-LDH (fig. 1(c)), a series of diffraction peaks at 11.7 °, 23.6 °, 34.8 °, 39.3 °, 46.9 °, 60.0 ° and 61.5 ° correspond to the (003), (006), (012), (015), (018), (110) and (113) crystal planes, respectively. The interlayer spacing was 0.758nm, indicating intercalation by carbonate. The interlayer spacing of NiFe-LDH (FIG. 1(e)) and NiV-LDH (FIG. 1(a)) was 0.769nm and 0.752nm, respectively. The difference of the three LDH layer spacing is due to different metal ions and different radiuses of the laminates, different charge densities of the laminates and different attraction force of anions between the laminates. In LDHs, when the divalent cations are the same, the charge density of the lamellae is related to the radius of the trivalent ions, the ion halfThe smaller the diameter is, the smaller the distance between two metal ions is, the higher the density of positive charges carried by the laminate is, the larger the electrostatic attraction between the laminate and anions between layers is, and the smaller the layer spacing is. Fe³⁺Has an ionic radius of

Greater than V³⁺Ionic radius of

And V is³⁺Easily oxidized to a smaller radius

And

thus, the charge density of the NiFe-LDH plates was lower than that of the NiV-LDH plates, resulting in larger layer spacings of NiFe-LDH (0.769nm) and smaller layer spacings of NiV-LDH (0.752 nm).

XRD analysis was performed on the products obtained with different molar ratios A of Fe and V, and the XRD pattern obtained is shown in FIG. 1. Fig. 1(a) shows the NiFeV-LDH of comparative example 1 when a is 0:1, fig. 1(b) shows the NiFeV-LDH of example 1 when a is 0.3:0.7, fig. 1(c) shows the NiFeV-LDH of example 2 when a is 0.5:0.5, fig. 1(d) shows the NiFeV-LDH of example 3 when a is 0.7:0.3, and fig. 1(e) shows the NiFe-LDH of comparative example 2 when a is 1: 0. From fig. 1(a) to fig. 1(e), the Fe content gradually increases, the V content gradually decreases, and the interlayer distance of each corresponding product gradually increases. In addition, the diffraction peak shapes of NiFeV-LDH (as shown in FIGS. 1(b) - (d)) and NiFe-LDH (as shown in FIG. 1(e)) are sharper and stronger than those of NiV-LDH (as shown in FIG. 1 (a)). This indicates that the presence of Fe is beneficial for improving the crystallinity of the LDH material.

And (3) analyzing the electron microscope result:

FIG. 2(a) is an SEM photograph of NiFeV-LDH of example 2, and from FIG. 2(a), it can be seen that NiFeV-LDH is in a criss-cross NiFeV-LDH nanosheet array, and is vertically and uniformly grown on foamed nickel. The nano sheets with the diameter of about 3 mu m form a three-dimensional firm reticular nano structure, can expose active sites as much as possible, and provides convenience for the transportation of electrolyte and the release of generated gas in the water decomposition process.

FIG. 2(b) is an element distribution diagram of NiFeV-LDH of example 2, and it can be seen from FIG. 2(b) that three metal elements of Ni, Fe and V coexist in NiFeV-LDH and are uniformly distributed.

FIG. 2(c) is a TEM image of NiFeV-LDH of example 2, and from FIG. 2(c), it can be seen that NiFeV-LDH has an ultra-thin nano-sheet morphology.

FIG. 2(d) is an HRTEM photograph of NiFeV-LDH of example 2. from FIG. 2(d), it can be seen that a lattice spacing of 0.25nm exists in NiFeV-LDH, corresponding to the (012) crystal plane of NiFeV-LDH.

XPS results analysis:

XPS analyses were performed on NiFeV-LDH of example 2, NiV-LDH of comparative example 1, and NiFe-LDH of comparative example 2, wherein:

FIG. 3(a) is an XPS survey of NiV-LDH, NiFe-LDH and NiFeV-LDH, demonstrating that three metal elements, Ni, Fe and V, coexist in NiFeV-LDH.

As can be seen from the Ni 2p spectra of NiV-LDH, NiFe-LDH and NiFeV-LDH shown in FIG. 3(b), NiFe-LDH (without V) and NiFeV-LDH (with V) have the same Ni 2p binding energy, and two peaks, each at 873.4eV and 855.9eV, correspond to Ni²⁺Ni 2p of (2)_1/2And Ni 2p_3/2. And Ni of NiV-LDH (Fe-free)²⁺But have higher binding energies, 873.6eV and 856.1 eV. Therefore, in NiFeV-LDH, the valence state of Ni is mainly affected by Fe rather than V.

As can be seen from the Fe 2p spectra of NiFe-LDH and NiFeV-LDH shown in FIG. 3(c), NiFeV-LDH has two peaks at 725.6eV and 711.9eV, which are attributed to Fe³⁺Fe 2p of_1/2And Fe 2p_3/2. The binding energy of NiFeV-LDH is significantly higher compared to the two peaks of NiFe-LDH (without V) at 725.2eV and 711.5eV, indicating that the presence of V results in an increase in the valence state of Fe.

As can be seen from the V2 p spectra of NiV-LDH and NiFeV-LDH shown in FIG. 3(d), the binding energies of the NiV-LDH peaks are 524.7eV and 517.0eV, respectively, and belong to V2 p_1/2And V2 p_3/2. The V2 p binding energy of NiFeV-LDH is 524.5eV (V2 p)_1/2) And 516.8eV (V2 p)_3/2) This reduction in V binding energy compared to NiV-LDH movement of-0.2 eVIs caused by the doping of Fe. Furthermore, the peak at 516.8eV can be fitted with three peaks, 515.8eV, 516.8eV and 517.5eV, belonging to V respectively³⁺、V⁴⁺And V⁵⁺。V⁴⁺And V⁵⁺Indicates the presence of V³⁺Is partially oxidized during the synthesis.

In conclusion, the electronic structure of the binary LDH material (NiFe-LDH or NiV-LDH) is changed after the third metal ion (V or Fe) is added. In the ternary metal hydroxide NiFeV-LDH, V tends to act as an electron acceptor, whereas Fe tends to act as an electron donor, with electrons being transferred from Fe to V. This can be attributed to the high valence V ion (V)⁴⁺And V⁵⁺) It helps to stabilize the high valence state of the adjacent Fe ions. Generally, transition metals having higher valence states will exhibit higher OER performance. It is clear that the synergistic effect of the trimetallic system is crucial for the OER activity of the ternary LDH material.

Electrocatalytic OER test:

the products of each example and comparative example were tested using a standard three-electrode system, each test product being cut into approximately 1cm by 2cm samples, clamped in electrode clamps as working electrodes, partially immersed in an electrolyte to a working area of 1cm²The counter electrode is a graphite electrode and the reference electrode is a mercury/mercury oxide electrode. The electrolyte is a KOH solution of 1 mol/L. The polarization curve was tested using Linear Sweep Voltammetry (LSV) at a sweep rate of 5 mV/s. The test results were as follows:

FIG. 4(a) is a graph showing each product (NiFeV-LDH, NiV-LDH, NiFe-LDH), RuO of example 2 and comparative examples 1-2₂And OER polarization curves of nickel Foam (Ni Foam, abbreviated NF). FIG. 4(b) is an OER polarization curve of each of the products of examples 1-3 and comparative examples 1-2, which were synthesized with different molar ratios of Fe: V A. FIG. 4(c) shows that the respective products of examples 1 to 3 and comparative examples 1 to 2, which were synthesized with different molar ratios of Fe to V A, had a current density of 50mA cm^-2And 100mA cm^-2Comparative overpotential diagram of (1). FIG. 4(d) is a linear fit of the change in capacitance current density at a potential of 1.25V (vs RHE) versus scan rate for each of the products of example 2 and comparative examples 1-2. FIG. 4(e) is an impedance spectrum of each of the products of example 2 and comparative examples 1-2 and foamed nickel,the enlarged impedance maps of the products of example 2 and comparative example 2 are shown in the upper right hand corner of fig. 4 (e).

As can be seen from fig. 4(a) - (c): each product had a current density of 50mA cm^-2When the current density is the same, the potential of NiFeV-LDH is always lower than that of NiV-LDH, NiFe-LDH and RuO₂And NF potential, indicating that NiFeV-LDH exhibits very good OER catalytic activity. Especially, NiFeV-LDH prepared when the molar ratio A of Fe to V is 0.5:0.5 shows better OER catalytic activity. The current density reaches 50mA cm^-2In this case, the NiFeV-LDH prepared in example 2, having a molar ratio of Fe to V, A of 0.5 to 0.5, requires only 269mV overpotential (. eta.)₅₀269mV), the overpotential is much lower than NiFe-LDH (η)₅₀＝296mV)，NiV-LDH(η₅₀＝351mV)，RuO₂(η₅₀416mV) and nickel foam (η)₅₀469mV), indicating that the NiFeV-LDH material prepared has the best OER activity at a Fe: V molar ratio a of 0.5: 0.5. The maximum value of the double layer capacitance (Cdl) of NiFeV-LDH was found by calculation in FIG. 4(d), indicating that its catalytically active surface area exceeds that of NiFe-LDH and NiV-LDH. As can be seen from fig. 4 (e): by comparing the radius of the low-frequency semicircle with the resistance value, the NiFeV-LDH has the smallest charge transfer resistance and the fastest electron transfer rate in OER, which also indicates that the NiFeV-LDH has more excellent OER catalytic performance.

FIG. 5(a) is a graph of current density versus time for the products of example 2 and comparative examples 1-2. FIG. 5(b) is a comparison of electrocatalytic OER polarization curves before and after the product stability test of example 2. As shown in FIG. 5(a), at 200mA cm^-2At high current densities of (2), NiFeV-LDH showed excellent stability, and the initial current density remained 95% after OER testing for 75 h. At this current density, however, NiFe-LDH and NiV-LDH decay rapidly. Reducing current density such as 150mAcm^-2Next, the initial current density of NiV-LDH remained 90% after 20h of electrolysis, and NiFe-LDH still decayed rapidly at this current density. Continuously reducing the current density to 100mA cm^-2It was observed that NiFe-LDH only retained 80% of the initial current density after 20h of electrolysis. Shows that the NiFeV-LDH containing Fe and V has higher electrocatalytic stability, and the synergy (electron transfer) between V and FeIs more beneficial to improving the stability. In FIG. 5(b), the decay amplitude of NiFeV-LDH after stability test was small compared to that before stability test, indicating that the NiFeV-LDH of the present application has high stability.

Fig. 5(c) is an XRD chart before and after the product stability test of example 2, fig. 5(d) is an SEM photograph before and after the product stability test of example 2, fig. 5(e) is an XPS chart of Fe 2p before and after the product stability test of example 2, and fig. 5(f) is an XPS chart of V2 p before and after the product stability test of example 2, and it can be seen from fig. 5(c) - (f) that the variation width before and after the NiFeV-LDH stability test is small, which further indicates that NiFeV-LDH has superior stability.

In conclusion, the ternary metal layered hydroxide NiFeV-LDH has the advantages of low price, simple and convenient preparation method, high activity and high stability in OER, and can be used as an OER catalyst.

The above description is only for the preferred embodiment of the present application and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A preparation method of a ternary metal layered hydroxide NiFeV-LDH comprises the following steps:

(1) pretreating foamed nickel;

2. The production method according to claim 1, wherein the iron source is selected from any one of iron nitrate, iron sulfate, and iron chloride.

3. The production method according to claim 1, wherein the vanadium source is selected from any one of vanadium trichloride and vanadium sulfate.

4. The production method according to claim 1, wherein the alkali source is any one selected from urea and hexamethylenetetramine.

5. A ternary metal layered hydroxide NiFeV-LDH prepared according to the method of any one of claims 1-4, which takes foamed nickel as a substrate and a nickel source, and NiFeV-LDH nanosheet material is grown in situ on the substrate by hydrothermal synthesis.

6. Use of the ternary metal layered hydroxide NiFeV-LDH according to claim 5 as catalyst for water splitting reactions.

7. Use according to claim 6, wherein the ternary metal layered hydroxide NiFeV-LDH acts as an oxygen evolution reaction catalyst under alkaline conditions.