A nickel-zinc-iron ternary oxygen evolution electrode, a preparation method and application thereof

Abstract

The present application relates to a kind of nickel-zinc iron ternary oxygen electrode and its preparation method and application, including the following steps: (a) on the conductive substrate, electrodepositing nickel-zinc pre-plating layer is plated;(b) the conductive substrate of the nickel-zinc pre-plating layer of plating is as anode, nickel electrode is as cathode, be placed in the hydroxide aqueous solution containing iron source, under the condition of 70-90 DEG C, anode potential 1.8V~2.2V electrochemical oxidation is carried out.The conductive substrate of the nickel-zinc pre-plating layer of plating is as anode, nickel electrode is as cathode to carry out electrochemical oxidation, so that the metal zinc in pre-plating layer can be anodically dissolved, and soluble zincate ion is generated, so that abundant pore and defect are formed in-situ in electrode interior;Iron ion in electrolyte occurs replacement reaction on dissolved zinc site or exposed nickel site, and is introduced into electrode skeleton;So that more stable, active, and substrate combined firmly Porous ternary nickel-zinc iron composite electrode is finally obtained.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, and relates to a nickel-zinc-iron ternary oxygen evolution electrode, its preparation method, and its application. Background Technology

[0002] Alkaline water electrolysis for hydrogen production is a technology based on the principle of electrolysis, which uses an alkaline electrolyte solution to decompose water molecules, thereby generating hydrogen and oxygen. This technology uses direct current to pass through an electrolytic cell, causing water molecules to undergo a redox reaction at the electrodes, thus decomposing them into hydrogen and oxygen. The core principle of this technology is that an alkaline electrolyte solution (such as potassium hydroxide or sodium hydroxide solution) can enhance the conductivity of water, reduce energy consumption during the electrolysis process, and improve electrolysis efficiency.

[0003] Nickel-iron based materials are considered one of the most promising catalyst systems to replace noble metals due to their excellent intrinsic activity in the oxygen evolution reaction (OER) and good chemical stability in alkaline environments. To further enhance their performance, researchers often introduce a third element (such as Zn, Co, or Mo) to modulate the electronic structure of nickel-iron materials, increase the number of active sites, or construct special microstructures. The introduction of zinc has attracted particular attention because it can not only act as a structure-directing agent but also potentially generate beneficial electronic modulation effects in the material. However, finding a simple, controllable, and stable method to effectively and firmly integrate nickel, iron, and zinc into the same electrode structure to form a highly active stable phase remains a significant challenge.

[0004] Existing methods for preparing ternary nickel-zinc-iron electrodes mainly include hydrothermal methods, high-temperature pyrolysis methods, and traditional co-electrodeposition methods. Among these, the electrodeposition method is relatively simple, but the reduction potentials of the three metal ions (nickel, iron, and zinc) differ significantly (especially Zn). 2+ The reduction potential of Zn is much more negative than that of Ni. 2+ / Ni and Fe 2+ In simple mixed salt electrolytes, uniform co-deposition of nickel-zinc-iron (NiZn-Fe) compounds is difficult to achieve, easily leading to component segregation and phase separation, resulting in a deposited layer with a non-uniform microstructure. This structural inhomogeneity weakens the overall conductivity, mechanical stability, and catalytic performance uniformity of the electrode, and its performance is prone to rapid degradation under harsh oxygen evolution reaction (OER) conditions. More importantly, regardless of the method used to directly prepare the ternary nickel-zinc-iron composite, the active phase on its final surface is usually an (hydro)oxide generated in situ during the electrochemical OER. However, there is a significant difference between the initially prepared metallic or oxide structure and the active phase structure in the final working state. This indirect transformation may lead to insufficient exposure of active sites and poor structural stability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a nickel-zinc-iron ternary oxygen evolution electrode, which can directly construct a nickel-zinc-iron ternary oxygen evolution electrode with similar activity to the working state, uniform composition, stable structure, and strong bonding with the substrate under mild conditions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a nickel-zinc-iron ternary oxygen evolution electrode, comprising the following steps: (a) Nickel-zinc layer electrodeposition: Electrodeposition of a nickel-zinc pre-plating layer on a conductive substrate; (b) Electrochemical oxidation and iron replacement: The conductive substrate with a nickel-zinc pre-plated layer is used as the anode and the nickel electrode is used as the cathode. The substrate is placed in an aqueous hydroxide solution containing an iron source and electrochemical oxidation is carried out at 70-90°C and an anode potential of 1.8V~2.2V.

[0007] Optimally, step (a) is as follows: placing the conductive substrate in an aqueous solution containing nickel salt, zinc salt and complexing agent, at a pH of 4-5 and a current density of 10-30 mA cm⁻¹. -2 Electrodeposition is performed under specific conditions.

[0008] Optimally, in step (a), the nickel salt is a mixture selected from one or more of nickel sulfate, nickel chloride, and nickel nitrate, the zinc salt is a mixture selected from one or more of zinc sulfate, zinc chloride, and zinc nitrate, and the complexing agent is potassium pyrophosphate, ammonium chloride, or sodium citrate.

[0009] Furthermore, the concentration of the nickel salt is 0.6~1 mol / L, and the concentration of the zinc salt is 0.3~0.8 mol / L.

[0010] Further, the concentration of potassium pyrophosphate is 150~350 g / L, the concentration of ammonium chloride is 10~50 g / L, and the concentration of sodium citrate is 80~150 g / L.

[0011] Ideally, in step (a), the conductive substrate is ultrasonically cleaned sequentially in acetone, hydrochloric acid solution, and deionized water before use.

[0012] Ideally, in step (b), the iron source is a mixture of one or more of ferric sulfate, ferric nitrate, ferric chloride, and potassium ferrate, with a concentration of 5 to 20 ppm.

[0013] Ideally, in step (b), the hydroxide is potassium hydroxide or sodium hydroxide with a concentration of 6-8 mol / L.

[0014] Another object of the present invention is to provide a nickel-zinc-iron ternary oxygen evolution electrode, which is prepared by the above-described preparation method.

[0015] Another object of the present invention is to provide the application of a nickel-zinc-iron ternary oxygen evolution electrode in the oxygen evolution reaction of alkaline water electrolysis.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The preparation method of the nickel-zinc-iron ternary oxygen evolution electrode of the present invention uses a conductive substrate coated with a nickel-zinc pre-plating layer as the anode and a nickel electrode as the cathode for electrochemical oxidation. This allows the metallic zinc in the pre-plating layer to undergo anodic dissolution, generating soluble zincate ions (such as Zn(OH)4). 2- This process creates abundant pores and defects in situ inside the electrode. Iron ions (or iron complexes) in the electrolyte undergo a displacement reaction at the dissolved zinc sites or exposed nickel sites and are introduced into the electrode framework. Some nickel and iron are oxidized to generate highly active hydroxyl oxides / hydroxides (such as NiOOH, FeOOH) species. This ultimately results in a more stable, active, and firmly bonded porous ternary nickel-zinc-iron composite electrode. Attached Figure Description

[0017] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is an electron microscope image of the nickel-zinc-iron ternary oxygen evolution electrode in Example 1; Figure 2 This is a comparison image of the nickel-zinc-iron ternary oxygen evolution electrode in Example 1 and the blank substrate LSV; Figure 3 The image shows the stability test results of the nickel-zinc-iron ternary oxygen evolution electrode in Example 1. Detailed Implementation

[0018] The present invention discloses a method for preparing a nickel-zinc-iron ternary oxygen evolution electrode, comprising the following steps: (a) nickel-zinc layer electrodeposition: electrodepositing a nickel-zinc pre-plating layer on a conductive substrate; (b) electrochemical oxidation and iron replacement: placing the conductive substrate with the nickel-zinc pre-plating layer as the anode and the nickel electrode as the cathode in an aqueous hydroxide solution containing an iron source, and performing electrochemical oxidation at 70-90°C and an anode potential of 1.8V-2.2V. Using the conductive substrate with the nickel-zinc pre-plating layer as the anode and the nickel electrode as the cathode for electrochemical oxidation allows for anodic dissolution of the metallic zinc in the pre-plating layer, generating soluble zincate ions (such as Zn(OH)₄). 2-This process creates abundant pores and defects in situ within the electrode. Iron ions (or iron complexes) in the electrolyte undergo displacement reactions at dissolved zinc sites or exposed nickel sites, and are introduced into the electrode framework. Some nickel and iron are oxidized to generate highly active hydroxyl oxides / hydroxides (such as NiOOH, FeOOH) species. Ultimately, a more stable, active, and firmly bonded porous ternary nickel-zinc-iron composite electrode is obtained (i.e., this invention effectively regulates the chemical composition and three-dimensional morphology of the electrode through the "sacrificial template" effect of zinc and the in-situ displacement of iron, significantly improving its oxygen evolution performance, structural stability, and ability to bond with the substrate).

[0019] In step (a), the conductive substrate is ultrasonically cleaned sequentially in acetone, hydrochloric acid solution (1~4 mol / L), and deionized water (preferably for 5~15 minutes) before use to remove surface oil, oxides, and impurities. It is then rinsed with pure water and dried for later use. The conductive substrate is a nickel mesh, nickel foam, or nickel felt.

[0020] In step (a), the conductive substrate is placed in an aqueous solution (i.e., an electrolyte) containing nickel salt, zinc salt, and a complexing agent, at a pH of 4-5 and a current density of 10-30 mA cm⁻¹. -2 Electrodeposition is performed under the following conditions (preferably for 10-40 min). The nickel salt is a mixture selected from one or more of nickel sulfate, nickel chloride, and nickel nitrate; the zinc salt is a mixture selected from one or more of zinc sulfate, zinc chloride, and zinc nitrate; and the complexing agent is potassium pyrophosphate, ammonium chloride, or sodium citrate. The concentration of the nickel salt is 0.6-1 mol / L, and the concentration of the zinc salt is 0.3-0.8 mol / L. The concentration of the potassium pyrophosphate is 150-350 g / L, the concentration of the ammonium chloride is 10-50 g / L, and the concentration of the sodium citrate is 80-150 g / L.

[0021] In step (b), the iron source is a mixture selected from one or more of ferric sulfate, ferric nitrate, ferric chloride, and potassium ferrate, with a concentration of 5-20 ppm. The hydroxide is potassium hydroxide or sodium hydroxide, with a concentration of 6-8 mol / L. That is, step (b) involves applying a constant anodic potential to the two-electrode system for 4-20 hours.

[0022] The above preparation method can produce a nickel-zinc-iron ternary oxygen evolution electrode, which can be used as an electrode in the alkaline water electrolysis oxygen evolution reaction.

[0023] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Example 1

[0026] This embodiment provides a nickel-zinc-iron ternary oxygen evolution electrode and its preparation method, as detailed below: (a) Pretreatment: The conductive substrate (nickel-based substrate, commercially available nickel mesh) is placed in acetone, 3M (i.e. mol / L) hydrochloric acid solution and deionized water respectively for ultrasonic cleaning for 10 minutes each to remove surface oil, oxides and impurities, and then rinsed with pure water and dried for later use.

[0027] Nickel-zinc layer electrodeposition: A nickel-zinc alloy layer is deposited on a conductive substrate using an electrodeposition method. The electrolyte used for electrodeposition is an aqueous solution (pH=4.5) containing 0.84 M nickel salt (nickel chloride), 0.6 M zinc salt (zinc chloride), and 100 g / L complexing agent (sodium citrate); the current density is controlled at 20 mA cm⁻¹. -2 The time is 30 minutes to obtain a conductive substrate with a nickel-zinc pre-plating layer (i.e., an electrode with a nickel-zinc pre-plating layer).

[0028] (b) Electrochemical oxidation and iron replacement: An electrode with a nickel-zinc pre-plated layer was used as the anode and placed in a 7 M potassium hydroxide aqueous solution containing 10 ppm potassium ferrate as the iron source. Electrochemical oxidation was performed at 80°C with a nickel electrode as the cathode and a constant anolytical potential of 1.8 V applied to the two-electrode system for 10 h, yielding the following result: Figure 1 The nickel-zinc-iron ternary oxygen evolution electrode is shown.

[0029] Figure 1 It can be seen that abundant pores and defects are formed inside the electrode, while iron ions (or iron complexes) in the electrolyte undergo a displacement reaction at dissolved zinc sites or exposed nickel sites, and are introduced into the electrode framework, as shown in Table 1, forming a nanosheet structure and increasing the active area. Using an electrochemical workstation, at 7 MKOH and 80°C, the LSV (linear sweep voltammetry) curves of the nickel-zinc-iron electrode of this embodiment and the untreated substrate (blank substrate; i.e., a commercially available nickel mesh was sequentially ultrasonically cleaned for 10 minutes each in acetone, 3M (i.e., mol / L) hydrochloric acid solution, and deionized water to remove surface oil, oxides, and impurities, and then rinsed and dried with pure water) were tested, as shown below. Figure 2 and Figure 3 As shown, the results are displayed at a current density of 500 mA / cm². 2 Under the given conditions, the overpotential of the nickel-iron-zinc electrode was 260 mV lower than that of the blank substrate, showing a significant effect.

[0030] Table 1. Nickel, Zinc, and Iron Element Content

[0031] The results of the above electrodes after 100 hours of operation are shown in Table 2.

[0032]

[0033] Example 2

[0034] This embodiment provides a nickel-zinc-iron ternary oxygen evolution electrode and its preparation method, as detailed below: (a) Pretreatment: The conductive substrate (nickel-based substrate, commercially available nickel mesh) was placed in acetone, 3M (mol / L) hydrochloric acid solution and deionized water for ultrasonic cleaning for 10 minutes each to remove surface oil, oxides and impurities, and then rinsed with pure water and dried for later use.

[0035] Nickel-zinc layer electrodeposition: A nickel-zinc alloy layer is deposited on a conductive substrate using an electrodeposition method. The electrolyte used for electrodeposition is an aqueous solution (pH=4.0) containing 0.63 M nickel salt (nickel chloride), 0.73 M zinc salt (zinc chloride), and 150 g / L complexing agent (sodium citrate); the current density is controlled at 10 mA cm⁻¹. -2 The time is 40 minutes to obtain a conductive substrate with a nickel-zinc pre-plating layer (i.e., an electrode with a nickel-zinc pre-plating layer).

[0036] (b) Electrochemical oxidation and iron replacement: An electrode with a nickel-zinc pre-plated layer was used as the anode and placed in an aqueous solution of potassium hydroxide with a concentration of 6 M containing 20 ppm iron source (potassium ferrate). Electrochemical oxidation was carried out at a temperature of 90 °C, with a nickel electrode as the cathode and a constant anode potential of 2.2 V applied to the two-electrode system for 20 h.

[0037] Example 3

[0038] This embodiment provides a nickel-zinc-iron ternary oxygen evolution electrode and its preparation method, as detailed below: (a) Pretreatment: The conductive substrate (nickel-based substrate, commercially available nickel mesh) was placed in acetone, 3M (mol / L) hydrochloric acid solution and deionized water for ultrasonic cleaning for 10 minutes each to remove surface oil, oxides and impurities, and then rinsed with pure water and dried for later use.

[0039] Nickel-zinc layer electrodeposition: A nickel-zinc alloy layer is deposited on a conductive substrate using an electrodeposition method. The electrolyte used for electrodeposition is an aqueous solution (pH=5.0) containing 1 M nickel salt (nickel chloride), 0.37 M zinc salt (zinc chloride), and 80 g / L complexing agent (sodium citrate); the current density is controlled at 30 mA cm⁻¹. -2 The time is 10 minutes, and a conductive substrate with a nickel-zinc pre-plating layer (i.e. an electrode with a nickel-zinc pre-plating layer) is obtained.

[0040] (b) Electrochemical oxidation and iron replacement: An electrode with a nickel-zinc pre-plated layer was used as the anode and placed in an aqueous solution of potassium hydroxide with a concentration of 8 M containing 5 ppm of iron source potassium ferrate. At a temperature of 70 °C, a nickel electrode was used as the cathode and a constant anode potential of 1.8 V was applied to the two-electrode system for 4 h to carry out electrochemical oxidation.

[0041] Comparative Example 1 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that step (a) does not contain zinc salt.

[0042] Comparative Example 2 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that step (a) does not contain nickel salt.

[0043] Comparative Example 3 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that step (a) does not contain a complexing agent.

[0044] Comparative Example 4 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that step (b) does not contain an iron source (potassium ferrate).

[0045] Comparative Example 5 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that in step (b), it is placed in an aqueous solution containing 5 ppm of potassium ferrate, an iron source.

[0046] Comparative Example 6 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Example 1, except that: In step (a), the electrolyte is an aqueous solution (pH=4.5) containing 0.84 M nickel salt (nickel chloride), 0.6 M zinc salt (zinc chloride), 100 g / L complexing agent (sodium citrate) and 10 ppm iron source potassium ferrate. In step (b), the electrode with the pre-plated layer is used as the anode and placed in a 7 M potassium hydroxide aqueous solution for electrochemical oxidation.

[0047] Comparative Example 7 This example provides an oxygen evolution electrode and its preparation method, which is basically the same as that in Comparative Example 6, except that in step (b), the electrode with the pre-plated layer is directly immersed in an 8 M potassium hydroxide aqueous solution for 30 min, then rinsed several times with ultrapure water and air-dried naturally.

[0048] The performance of the oxygen evolution electrodes of Examples 1-3 and Comparative Examples 1-7 was tested, and the results are shown in Table 3.

[0049] Table 3 Performance test table of oxygen evolution electrodes in Examples 1-3 and Comparative Examples 1-7 Oxygen Evolution Electrode <![CDATA[Overpotential (mV @ 500mA cm -2 )]]> Example 1 297 Example 2 305 Example 3 310 Comparative Example 1 380 Comparative Example 2 430 Comparative Example 3 408 Comparative Example 4 446 Comparative Example 5 377 Comparative Example 6 358 Comparative Example 7 342 Untreated electrode 558 The stability and ultrasonic weight loss rate of the oxygen evolution electrodes of Examples 1-3 and Comparative Examples 1-7 were also tested, and the results are shown in Table 4.

[0050] Table 4. Stability and ultrasonic weight loss rate test results of oxygen evolution electrodes in Examples 1-3 and Comparative Examples 1-7. Oxygen Evolution Electrode <![CDATA[Overpotential after 100 h of stability (mV @ 500 mA cm -2 ).]]> Ultrasonic weight loss rate (%) Example 1 303 0.22 Example 2 306 0.31 Example 3 315 0.50 Comparative Example 1 435 1.54 Comparative Example 2 487 2.31 Comparative Example 3 488 2.46 Comparative Example 4 497 2.77 Comparative Example 5 431 1.88 Comparative Example 6 422 2.53 Comparative Example 7 407 3.19 Untreated electrode 562 0.08 Note: The ultrasonic conditions are 20% KOH, 2 hours, and 60℃.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-zinc-iron ternary oxygen evolution electrode, characterized in that, Includes the following steps: (a) Nickel-zinc layer electrodeposition: Electrodeposition of a nickel-zinc pre-plating layer on a conductive substrate; (b) Electrochemical oxidation and iron replacement: The conductive substrate with a nickel-zinc pre-plated layer is used as the anode and the nickel electrode is used as the cathode. The substrate is placed in an aqueous hydroxide solution containing an iron source and electrochemical oxidation is carried out at 70-90°C and an anode potential of 1.8V~2.2V.

2. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 1, characterized in that, Step (a) involves placing the conductive substrate in an aqueous solution containing nickel salt, zinc salt, and a complexing agent at a pH of 4-5 and a current density of 10-30 mAcm. -2 Electrodeposition is performed under specific conditions.

3. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 2, characterized in that: In step (a), the nickel salt is a mixture selected from one or more of nickel sulfate, nickel chloride and nickel nitrate, the zinc salt is a mixture selected from one or more of zinc sulfate, zinc chloride and zinc nitrate, and the complexing agent is potassium pyrophosphate, ammonium chloride or sodium citrate.

4. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 3, characterized in that: The concentration of the nickel salt is 0.6~1 mol / L, and the concentration of the zinc salt is 0.3~0.8 mol / L.

5. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 3, characterized in that: The concentration of potassium pyrophosphate is 150~350 g / L, the concentration of ammonium chloride is 10~50 g / L, and the concentration of sodium citrate is 80~150 g / L.

6. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 1, characterized in that: In step (a), the conductive substrate is ultrasonically cleaned in acetone, hydrochloric acid solution and deionized water in sequence before use.

7. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 1, characterized in that: In step (b), the iron source is a mixture of one or more of ferric sulfate, ferric nitrate, ferric chloride and potassium ferrate, with a concentration of 5 to 20 ppm.

8. The method for preparing the nickel-zinc-iron ternary oxygen evolution electrode according to claim 1, characterized in that: In step (b), the hydroxide is potassium hydroxide or sodium hydroxide, with a concentration of 6-8 mol / L.

9. A nickel-zinc-iron ternary oxygen evolution electrode, characterized in that: It is prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of the nickel-zinc-iron ternary oxygen evolution electrode according to claim 9, characterized in that: Application in the alkaline electrolysis of water for oxygen evolution.

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