A low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst and its efficient preparation method and application

Abstract

A low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst and its efficient preparation method and application. The present invention belongs to the field of LDH-type oxygen evolution electrocatalysts. The purpose of the present invention is to solve the technical problems of low energy efficiency of NiFe‑LDH-type electrodes synthesized by hydrothermal method and poor electrocatalytic oxygen evolution performance of NiFe‑LDH-type electrodes prepared by pulse electrodeposition. The present invention uses an aqueous solution of nickel salt and iron salt as an electrolyte solution, and a pretreated nickel-based material as a working electrode, and performs constant voltage deposition in a three-electrode system. During the deposition process, stirring is continued to obtain an electrocatalyst. The method of the present invention has a simple process and a high energy efficiency ratio. The obtained product has a regular shape and uniform size, and is evenly loaded on a carrier, which significantly improves the active sites and electron transfer capacity. When applied to the electrocatalytic oxygen evolution reaction, it reaches 10 mA·cm ‑2 The overpotential required for the current density is as low as 189mV, with excellent performance.

Description

Technical Field

[0001] The present invention belongs to the field of LDH type oxygen evolution electrocatalysts, and in particular relates to a low overpotential Ni3Fe based LDH type oxygen evolution electrocatalyst and an efficient preparation method and application thereof. Background Art

[0002] The depletion of fossil fuels and the growing demand for energy have brought huge challenges to mankind. In addition, the environmental problems caused by the energy consumption process have made the development of clean, renewable green energy urgent. Hydrogen energy, as a clean, efficient and zero-carbon secondary energy source, is considered to be the mainstream direction of clean energy development in the future. The development of hydrogen energy is a strategic choice for mankind to get rid of dependence on fossil energy and ensure energy security. The electrolysis of water to produce hydrogen is currently a key to solving the problem of renewable energy, but the oxygen evolution reaction (OER) is a bottleneck that urgently needs to be broken through in the field of electrolysis of water to produce hydrogen, and slow kinetics is still a fatal disadvantage. The most effective electrocatalysts for improving OER performance are RuO2 and IrO2, but their high prices and scarce reserves hinder their industrial applications. Therefore, there is an urgent need to develop cheap, efficient and durable OER electrocatalysts to replace precious metal catalysts.

[0003] Research in recent years has shown that layered double hydroxides (LDHs) are a new type of 2D layered nanomaterials, consisting of positively charged metal cation layers and negatively charged interlayer anions. Due to the adjustable main cations, exchangeable interlayer anions, and structural memory effects, LDHs are considered to be ideal materials for exploring efficient OER electrocatalysts. Researchers have conducted in-depth studies on various transition metals, among which NiFe-based LDH-type catalysts performed the best and can further improve the OER activity of the catalyst, providing an effective strategy for the development of efficient and inexpensive OER catalysts, which has far-reaching significance for accelerating the popularization of the conversion and storage of new renewable energy sources.

[0004] At present, the commonly used methods for synthesizing LDH-type catalysts include hydrothermal synthesis and electrodeposition synthesis. Compared with the time-consuming and energy-intensive hydrothermal synthesis method, the electrodeposition synthesis method is more popular. The current electrodeposition method used to synthesize NiFe-based LDH-type catalysts is mainly pulse electrodeposition. Although this method is time-consuming and energy-efficient, the electrocatalytic oxygen evolution performance of the obtained catalyst is poor. For example, Yang Yang et al. prepared NiFe-LDH electrodes on carbon cloth using pulse electrodeposition. The obtained samples are composed of multiple layer structures attached to the carbon cloth substrate in a flower shape. The size is very small and the growth is uneven, which leads to poor electrocatalytic oxygen evolution performance of the material. The crystallinity, structural composition and micromorphology of LDH-type catalysts are closely related to the electrocatalytic oxygen evolution performance. The simple and rapid synthesis of efficient NiFe-LDH-type electrodes has always been a problem that needs to be solved in this field. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problems of low energy efficiency of NiFe-LDH type electrodes synthesized by hydrothermal method and poor electrocatalytic oxygen evolution performance of NiFe-LDH type electrodes prepared by pulse electrodeposition, and to provide a low overpotential Ni3Fe-based LDH type oxygen evolution electrocatalyst and its efficient preparation method and application.

[0006] One of the objects of the present invention is to provide a method for efficiently preparing a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst, the preparation method being carried out according to the following steps:

[0007] An aqueous solution of nickel salt and iron salt is used as the electrolyte solution, and the pretreated nickel-based material is used as the working electrode. Constant voltage deposition is carried out in a three-electrode system with continuous stirring during the deposition process to obtain a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst.

[0008] It is further defined that nickel salts include nickel sulfate, nickel nitrate, nickel carbonate, and nickel phosphate, and iron salts include iron sulfate and iron nitrate.

[0009] It is further defined that the electrolyte solution comprises at least one nitrate salt.

[0010] It is further defined that the nickel salt concentration in the electrolyte solution is 0.1 to 1.0 mol / L, and the iron salt concentration is 0.05 to 0.5 mol / L.

[0011] Further defined, the parameters of constant voltage deposition are: voltage of -0.9 to -1.5 V, current density of 50 to 300 mA / cm 2 , time is 3 to 30 minutes, temperature is 10 to 50℃.

[0012] It is further defined that the nickel-based material is nickel foam, nickel sheet or nickel mesh.

[0013] It is further defined that the pretreatment process is as follows: the nickel-based material is ultrasonically cleaned in acetone, HCl aqueous solution, ethanol, and deionized water in sequence, and then vacuum dried.

[0014] The second object of the present invention is to provide a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst prepared by the above method, wherein the electrocatalyst is a nano-microsphere composed of nano-sheets.

[0015] The third object of the present invention is to provide a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst prepared by the above method for use in an electrocatalytic oxygen evolution reaction.

[0016] It is further defined that the electrocatalyst reaches 10 to 100 mA·cm -2 The overpotential required for the current density is as low as 180-265mV.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The essential feature of the present invention is to provide a highly efficient preparation method of a Ni3Fe-based LDH-type oxygen evolution electrocatalyst with simple preparation process, low price and excellent performance. The present invention adopts constant voltage deposition and adjusts the carrier selection and process parameter control to obtain a Ni3Fe-based LDH-type oxygen evolution electrocatalyst with regular nanoparticle shape and uniform size, which is uniformly loaded on the carrier, significantly improving the active sites and electron transfer capacity, and when applied to the electrocatalytic oxygen evolution reaction, it reaches 10mA·cm -2 The overpotential required for the current density is as low as 189mV, with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The morphology of blank NF and Ni3Fe-LDH / NF-8 in Example 2; (a) - blank NF, (b) - SEM image of Ni3Fe-LDH / NF-8; (c) TEM image of Ni3Fe-LDH / NF-8;

[0020] Figure 2 is the XRD pattern of Ni3Fe-LDH / NF-8 of Example 2;

[0021] Figure 3 HAADF-STEM image and EDS mapping image of Ni3Fe-LDH / NF-8 of Example 2. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0024] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0025] Example 1: The highly efficient preparation method of the low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst of this embodiment is carried out by the following steps:

[0026] Step 1:

[0027] An electrolyte aqueous solution containing 0.27 mol / L Ni(NO)3·6H2O and 0.09 mol / L Fe(NO)3·9H2O is prepared as an electrolyte solution;

[0028] Step 2:

[0029] The nickel foam was firstly ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60°C until completely dry, thereby obtaining the pretreated nickel foam.

[0030] Step 3:

[0031] The pretreated nickel foam was used as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. The temperature was 25 °C and the current density was 100 mA / cm 2 Electrochemical deposition was performed at a constant voltage of -1 V for 5 min with continuous stirring during the deposition process. After the deposition, the sample was rinsed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum drying oven at 60 °C overnight to obtain a Ni3Fe-based LDH-type oxygen evolution electrocatalyst, which was recorded as Ni3Fe-LDH / NF-5.

[0032] Example 2: The highly efficient preparation method of the low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst of this embodiment is carried out by the following steps:

[0033] Step 1:

[0034] An electrolyte aqueous solution containing 0.27 mol / L Ni(NO)3·6H2O and 0.09 mol / L Fe(NO)3·9H2O is prepared as an electrolyte solution;

[0035] Step 2:

[0036] The nickel foam was firstly ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60°C until completely dry, thereby obtaining the pretreated nickel foam.

[0037] Step 3:

[0038] The pretreated nickel foam was used as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. The temperature was 25 °C and the current density was 100 mA / cm 2 Electrochemical deposition was carried out at a constant voltage of -1 V for 8 min with continuous stirring during the deposition process. After the deposition, the sample was rinsed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum drying oven at 60°C overnight to obtain a Ni3Fe-based LDH-type oxygen evolution electrocatalyst, which was recorded as Ni3Fe-LDH / NF-8.

[0039] The scanning electron microscope image of Ni3Fe-LDH / NF-8 in this embodiment is as follows Figure 1 As shown, Figure (a) reveals the 3D porous structure of the blank NF substrate, which provides abundant sites for the growth of the catalyst, and its strong conductivity is conducive to electron transfer and accelerates the occurrence of oxygen evolution reaction; Figure (b) shows the spherical structural characteristics of Ni3Fe-LDH / NF-8, and the transmission electron microscopy TEM results in Figure (c) further confirm that the synthesized sample is a nanosphere composed of nanosheets.

[0040] The XRD spectrum of Ni3Fe-LDH / NF-8 in this example is as follows Figure 2 As shown, the (003), (006), (012), and (110) diffraction peaks shown in the sample are typical characteristic peaks of hydrotalcite-like LDH materials (JCPDS#40-0215), indicating the successful preparation of Ni3Fe-LDH. However, it is worth noting that the crystallinity of the material is not high, which is beneficial to the electrocatalytic performance and is conducive to the generation of more active sites, which has been confirmed by many studies in recent years.

[0041] The chemical composition of Ni3Fe-LDH / NF-8 in this embodiment was determined by HAADF-STEM. Figure 3 As shown, the mapping shows that each element is evenly distributed on the substrate.

[0042] Example 3: The highly efficient preparation method of the low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst of this embodiment is carried out by the following steps:

[0043] Step 1:

[0044] An electrolyte aqueous solution containing 0.27 mol / L Ni(NO)3·6H2O and 0.09 mol / L Fe(NO)3·9H2O is prepared as an electrolyte solution;

[0045] Step 2:

[0046] The nickel foam was firstly ultrasonically cleaned in acetone for 15 minutes, then ultrasonically cleaned in a 2 mol / L HCl aqueous solution for 15 minutes, and finally ultrasonically cleaned in ethanol and deionized water for 10 minutes each, and then vacuum dried in a vacuum drying oven at 60°C until completely dry, thereby obtaining the pretreated nickel foam.

[0047] Step 3:

[0048] The pretreated nickel foam was used as the working electrode, the platinum electrode as the counter electrode, and the Ag / AgCl electrode as the reference electrode. The temperature was 25 °C and the current density was 100 mA / cm 2 Electrochemical deposition was performed at a constant voltage of -1 V for 12 min with continuous stirring during the deposition process. After the deposition, the sample was rinsed repeatedly with ethanol and deionized water for 3 times and then dried in a vacuum drying oven at 60 °C overnight to obtain a Ni3Fe-based LDH-type oxygen evolution electrocatalyst, which was recorded as Ni3Fe-LDH / NF-12.

[0049] Comparative Example 1: A method for preparing a Ni(OH)2 / NF oxygen evolution electrocatalyst comprises the following steps:

[0050] 87 mg Ni(NO)3·6H2O was dissolved in a mixed solution of 30 mL deionized water and 10 mL ethanol, stirred on a magnetic stirrer for 10 min, and then the solution was transferred to a 50 mL polytetrafluoroethylene liner. The treated nickel foam was then immersed in the solution, and the liner was transferred to a stainless steel reactor, sealed, and hydroheated at 180°C for 6 h. The reactor was naturally cooled to room temperature, and the reactor was taken out. The product was repeatedly rinsed with ethanol and deionized water for 3 times, and then dried in a vacuum drying oven at 60°C for 12 h to obtain Ni(OH)2 / NF.

[0051] Comparative Example 2: A method for preparing a RuO2 / NF oxygen evolution electrocatalyst comprises the following steps:

[0052] 5 mg of RuO2 powder and 32 μL of 5 wt.% Nafion solution were dissolved in 0.968 mL of a mixture of water and ethanol, wherein the volume ratio of water to ethanol was 4:1. The mixture was then ultrasonicated for at least 30 min to obtain a uniform mixture. Subsequently, 50 μL of the mixture was dropped onto a 1 cm*1 cm nickel foam and dried in a 60°C vacuum drying oven for later use.

[0053] Application examples:

[0054] The electrocatalysts prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to electrocatalytic oxygen evolution reaction in 1M KOH solution.

[0055] Detection test:

[0056] The electrocatalytic oxygen production (OER) performance of all the above catalyst materials was tested in a standard three-electrode electrolyzer, where the cycle scan range was 0.1-1.1 V and the scan rate was 5 mV / s. The results are shown in Table 1. It should be noted that all the potentials obtained with the Hg / HgO electrode as the reference electrode in the electrocatalytic test were converted into reversible hydrogen electrode potentials in the property diagram.

[0057] Table 1 Electrocatalytic oxygen production (OER) performance

[0058] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 <![CDATA[10mA·cm -2 Current density required overpotential (mV)]]> 199 189 197 - 291 <![CDATA[100mA·cm -2 Current density required overpotential (mV)]]> 261 248 254 329 386

[0059] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An efficient preparation method of a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst, characterized in that: The method proceeds as follows: The aqueous solution of Ni(NO)3·6H2O and Fe(NO)3·9H2O was used as the electrolyte solution. The concentration of Ni(NO)3·6H2O in the electrolyte solution was 0.27 mol / L, and the concentration of Fe(NO)3·9H2O in the electrolyte solution was 0.09 mol / L. The pretreated nickel-based material was used as the working electrode. Constant voltage deposition was carried out in a three-electrode system. Stirring was continued during the deposition process. The voltage was -1 V and the current density was 100 mA / cm 2 , the time is 5-12min, and a low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst is obtained. The electrocatalyst is a nano-microsphere composed of nanosheets, and the electrocatalyst reaches 10-100 mA·cm -2 The overpotential required for the current density is as low as 180~265mV.

2. The method according to claim 1, characterized in that The constant voltage deposition temperature is 10~50℃.

3. The method according to claim 1, characterized in that The nickel-based material is nickel foam, nickel sheet or nickel mesh.

4. The method according to claim 1, characterized in that: Pretreatment process: The nickel-based material is ultrasonically cleaned in acetone, HCl aqueous solution, ethanol, and deionized water in sequence, and then vacuum dried.

5. Use of the low overpotential Ni3Fe-based LDH-type oxygen evolution electrocatalyst prepared by the method according to any one of claims 1 to 4 in an electrocatalytic oxygen evolution reaction.

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