Preparation method of nickel-iron-tungsten oxygen evolution electrode

Abstract

The invention provides a preparation method of a nickel-iron-tungsten oxygen evolution electrode, and belongs to the technical field of hydrogen energy. The method comprises the following steps: by taking a nickel-iron alloy matrix as a working electrode, carrying out electrochemical oxidation-reduction activation treatment at room temperature in a mixed solution of tungstate, nitrate and chloride, and then carrying out heat treatment on the nickel-iron alloy matrix. In the electrochemical oxidation process, nickel ions and iron ions are dissolved out of the nickel-iron alloy matrix, meanwhile, electrochemical oxidation of chloride ions is carried out to form active chlorine, and the nickel ions and the iron ions are further chemically etched out; in the electrochemical reduction process, nitrate radicals and water on the electrode are reduced to generate hydroxyl radicals; in the process, nickel and iron ions on the electrode are combined with tungstate radicals and hydroxyl radicals to form a nickel-iron-tungsten composite hydroxide; and a nickel-iron-tungsten composite oxide is formed in the subsequent heat treatment process, so that the oxygen evolution activity and stability are further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen energy, and particularly relates to a preparation method of a nickel-iron-tungsten oxygen evolution electrode. Background Art

[0002] The development of intermittent renewable energy sources such as wind energy and solar energy has stimulated great interest in the development of new electrochemical technologies for energy storage and conversion. These include lithium / sodium batteries, metal-air batteries, supercapacitors, fuel cells, and electrolyzers. Among these technologies, water electrolysis for hydrogen production is one of the most attractive technologies to address the challenges of renewable energy fluctuations and is suitable for long-term energy storage. The anodic oxygen evolution reaction (OER) and the cathodic hydrogen evolution reaction (HER) are the core reactions of water electrolysis for hydrogen production. In these two reactions, OER is a complex process involving four-electron discharge, decoupling of four protons, and the formation of an oxygen double bond. Due to its high overpotential (η), OER is the rate-limiting step in water electrolysis for hydrogen production and also causes high electrical energy consumption.

[0003] Noble metal ruthenium and iridium-based catalyst materials are considered to be the most active electrocatalysts for OER in acidic and alkaline media at present, but their limited reserves and high costs undoubtedly hinder their large-scale application. The research community has made extensive efforts to develop highly active, stable, and affordable OER catalysts. In an alkaline system, based on traditional nickel-based oxygen evolution electrodes, researchers have prepared nickel-iron catalysts to reduce the OER overpotential. Chinese Patent CN202011445346.4 discloses a preparation method of a tungsten-based oxygen evolution catalyst coated with transition metal hydroxide. By reacting nickel foam in a high-temperature and high-pressure hydrothermal reaction kettle containing sulfate, ammonium salt, and tungstate to obtain an intermediate product, and then performing high-temperature calcination in a reducing atmosphere, a primary product of nickel foam-supported tungsten oxide-tungsten bronze nanocomposite is obtained. The primary product is immersed in a mixed solution of alkali metal nitrate or nitric acid and a soluble transition metal salt and reacted for a certain time to obtain a tungsten-based oxygen evolution catalyst coated with transition metal hydroxide. This preparation process directly in-situ loads the tungsten-based oxygen evolution catalyst coated with transition metal hydroxide, avoiding the use of binders, but the preparation process of this method requires a high-temperature and high-pressure hydrothermal step, and the safety needs to be improved. Chinese Patent CN202210686366.3 discloses a preparation method of a high-efficiency nickel-iron alloy oxygen evolution electrode. By electroplating in a mixed solution of nickel sulfate, ferrous sulfate, citric acid, and ascorbic acid, the current density for electroplating with a nickel mesh as the substrate is 20 mA / cm 2 The electroplating temperature is 60 °C to prepare a high-efficiency nickel-iron alloy oxygen evolution electrode. This preparation process is economical and simple, and a Ni-Fe oxygen evolution electrode with a uniform and stable structure and composition is prepared by electrodeposition. Under the test conditions of 25 °C and 30% KOH, the Ni-Fe sample has a current density of 10 mA / cm 2The potential at the current density is 398 mV. The performance of this electrode is better than that of the nickel mesh, but there is still room for significant improvement.

[0004] In summary, the current nickel-iron-based oxygen evolution electrodes have a cumbersome preparation process, which affects the safety and feasibility of industrial preparation of the electrodes. How to introduce highly active components by a simple, reliable and controllable method while improving the OER activity and stability has become the main development direction of current nickel-iron-based oxygen evolution electrodes. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a preparation method of a nickel-iron-tungsten oxygen evolution electrode. The preparation method provided by the present invention is simple, highly controllable, easy to scale up, and the prepared electrode has the characteristics of high current density and high stability.

[0006] Technical Solution: The present invention provides a preparation method of a nickel-iron-tungsten oxygen evolution electrode, including:

[0007] (1) Pretreat the conductive substrate by degreasing, pickling, and water washing in sequence.

[0008] (2) Using a nickel-iron alloy substrate as the working electrode, perform electrochemical etching treatment in a mixed solution of tungstate, nitrate, and chloride to obtain a nickel-iron-tungsten composite hydroxide. The electrochemical etching treatment includes electrochemical oxidation treatment and electrochemical reduction treatment carried out in multiple cycles.

[0009] (3) After rinsing the obtained nickel-iron-tungsten composite hydroxide, put it into a muffle furnace for heat treatment to obtain a nickel-iron-tungsten oxygen evolution electrode.

[0010] The conductive substrate described in step (1) is a nickel-iron alloy mesh.

[0011] The tungstate described in step (2) includes sodium tungstate, ammonium tungstate, or ammonium metatungstate. The concentration of the tungstate is 0.001 - 0.05 mol / L.

[0012] The chloride described in step (2) includes one or two of sodium chloride, potassium chloride, ammonium chloride, nickel chloride, and iron chloride. The concentration of the chloride is 0.001 - 0.1 mol / L.

[0013] The nitrate described in step (2) includes one or two of sodium nitrate, potassium nitrate, nickel nitrate, and iron nitrate. The concentration of the nitrate is 0.001 - 0.1 mol / L.

[0014] The current density of the electrochemical oxidation treatment described in step (2) is 2 - 50 mA / cm 2 , and the time of the electrochemical oxidation treatment is 1 - 20 min.

[0015] The current density of the electrochemical reduction treatment described in step (2) is -2 to -50 mA / cm 2 , and the time of the electrochemical reduction treatment is 1 to 20 min.

[0016] The number of cycles of the cycle described in step (2) is 5 - 100.

[0017] The temperature of the heat treatment described in step (3) is 100 °C to 380 °C, and the time of the heat treatment is 1 h to 12 h.

[0018] The present invention provides a nickel-iron-tungsten oxygen evolution electrode prepared by the preparation method described in the above technical solution, which can be used in the application of electrolytic water for hydrogen production. Compared with the prior art, the present invention has the following remarkable advantages:

[0019] The main preparation process of the nickel-iron-tungsten oxygen evolution electrode described in the present invention is carried out at room temperature, and the subsequent high-temperature heat treatment step does not require atmosphere protection. The preparation method described in the present invention is simple and easy to operate, and is convenient for large-scale production.

[0020] The OER activity of the nickel-iron-tungsten oxygen evolution electrode described in the present invention is significantly better than that of the noble metal and non-noble metal catalysts reported in current research, and the activity is better than that of commercial IrO2. At 1 M KOH and 27 °C, the overpotential is <280 mV at 10 mA / cm 2 ; and the overpotential is <900 mV at 1000 mA / cm 2 (without solution voltage drop compensation).

[0021] The nickel-iron-tungsten oxygen evolution electrode described in the present invention has excellent stability. It shows excellent stability after 500 LSVs at 0 V to 1 V (relative to the saturated calomel electrode) in 1 M KOH at 27 °C. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a scanning electron microscope image (SEM) of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1.

[0023] Figure 2 It is an X-ray energy chromatogram (EDS) of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1.

[0024] Figure 3 It is a linear sweep voltammogram of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1 at 1 M KOH and 27 °C.

[0025] Figure 4 It is a linear sweep voltammetry cycle diagram of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1 at 1 M KOH and 27 °C.

[0026] Figure 5Linear sweep voltammetry cycling diagram of a nickel-iron-tungsten composite hydroxide obtained in Comparative Example 2 at 1 M KOH and 27 °C. Detailed implementation manners

[0027] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings of the specification and preferred embodiments, but this should not be construed as limiting the scope of the present invention to the following examples. Without departing from the above method idea of the present invention, various substitutions or changes made according to common general technical knowledge and customary means in the art should be included within the scope of the present invention.

[0028] Example 1

[0029] Cut the nickel-iron alloy into pieces with an effective area of 1 cm * 1 cm. Put the cut nickel-iron alloy substrate into absolute ethanol and perform ultrasonic degreasing treatment for 20 minutes. Then put it into 3 mol / L hydrochloric acid and perform ultrasonic treatment for 10 minutes. Then put it into ultrapure water and perform ultrasonic treatment for 20 minutes. After each stage of ultrasonic treatment, rinse it repeatedly with ultrapure water three times. Take it out and dry it at room temperature for later use.

[0030] Prepare a mixed solution with a molar concentration ratio of sodium chloride, sodium nitrate, and sodium tungstate of 1:4:4, where the concentration of sodium chloride is 0.005 mol / L. Perform two-electrode periodic electrochemical treatment at 27 °C. Use the pretreated nickel-iron alloy substrate as the working electrode and a graphite rod as the counter electrode in the mixed solution. In the first stage, apply an oxidation current of 5 mA for 2 min. In the second stage, apply a reduction current of -5 mA for 2 min. React for 80 cycles. After the reaction is completed, rinse it repeatedly with ultrapure water to obtain a nickel-iron-tungsten composite hydroxide.

[0031] Put the obtained nickel-iron-tungsten composite hydroxide into a muffle furnace, heat it to 350 °C and perform heat treatment for 1 h, and then cool it to room temperature to obtain a heat-treated nickel-iron-tungsten oxygen evolution electrode.

[0032] Use the above-prepared nickel-iron-tungsten oxygen evolution electrode for electrocatalytic oxygen evolution reaction. The specific steps are as follows: Construct a three-electrode system, where the working electrode is the nickel-iron-tungsten oxygen evolution electrode, the reference electrode is a mercury / mercurous chloride electrode, and the counter electrode is a titanium ruthenium electrode.

[0033] Figure 1 Shown is a scanning electron microscope photograph (SEM) of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1. The surface of the nickel-iron-tungsten oxygen evolution electrode is composed of dense nanospheres. This structure increases the electrochemically active specific surface area of the catalyst, increases the number of active sites, and effectively improves the electrocatalytic performance of the catalyst.

[0034] Figure 2 Shown is an X-ray energy chromatogram of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1. The distributions of Ni, Fe, W, and O elements are uniform.

[0035] Figure 3 Shown is that in Example 1, a nickel-iron-tungsten oxygen evolution electrode was tested for OER performance in 1 M KOH solution at a scanning rate of 5 mV / s. At 10 mA / cm 2 the overpotential was only 270 mV, and at 1000 mA / cm 2 the overpotential was only 822 mV. (The data was not compensated for resistance). The results show that this material has excellent OER activity.

[0036] Figure 4 Shown is the linear sweep voltammetry cycle diagram of a nickel-iron-tungsten oxygen evolution electrode obtained in Example 1 in 1 M KOH at 27 °C. As the number of cyclic test periods increases, the performance does not decline, demonstrating excellent stability.

[0037] Example 2

[0038] In this example, while ensuring that the total charge during the electrochemical redox treatment is the same as that in Example 1, the current density and the number of cycles during the electrochemical redox treatment were changed. The nickel-iron alloy was cut into pieces with an effective area of 1 cm × 1 cm. The cut nickel-iron alloy substrate was put into absolute ethanol and ultrasonically degreased for 20 minutes, then put into 3 mol / L hydrochloric acid and ultrasonically treated for 10 minutes, and then put into ultrapure water and ultrasonically treated for 20 minutes. After each ultrasonic treatment, it was repeatedly rinsed three times with ultrapure water. It was taken out and dried at room temperature for later use.

[0039] A mixed solution with a molar concentration ratio of sodium chloride, sodium nitrate, and sodium tungstate of 1:4:4 was prepared, where the concentration of sodium chloride was 0.005 mol / L. Two-electrode periodic electrochemical treatment was carried out at 27 °C. The pretreated nickel-iron alloy substrate was used as the working electrode, and a graphite rod was used as the counter electrode in the mixed solution. In the first stage, a 20 mA oxidation current was applied for 2 min, and in the second stage, a -20 mA reduction current was applied for 2 min. The reaction was carried out for 20 cycles. After the reaction was completed, it was repeatedly rinsed clean with ultrapure water to obtain nickel-iron-tungsten composite hydroxide.

[0040] The obtained nickel-iron-tungsten composite hydroxide was put into a muffle furnace and heated to 350 °C for heat treatment for 1 h, and then cooled to room temperature to obtain a heat-treated nickel-iron-tungsten oxygen evolution electrode.

[0041] The above-prepared nickel-iron-tungsten oxygen evolution electrode was used for electrocatalytic oxygen evolution reaction. The specific steps were as follows: A three-electrode system was constructed, where the working electrode was nickel-iron-tungsten composite hydroxide, the reference electrode was a mercury / mercurous chloride electrode, and the counter electrode was a titanium ruthenium electrode. The OER performance was tested in 1 M KOH solution. At 10 mA / cm 2 the overpotential was only 272 mV, and at 1000 mA / cm 2The overpotential is only 839 mV. (The data is not compensated for resistance). The results show that this material has good OER activity. Linear sweep voltammetry cycling tests were carried out at 1 M KOH and 27 °C. As the number of cycling test cycles increased, the performance did not decline, demonstrating excellent stability.

[0042] Comparative Example 1

[0043] In this comparative example, the difference from Example 2 is that a solution without tungstate was used during the electrochemical redox treatment. The nickel-iron alloy was cut into pieces with an effective area of 1 cm * 1 cm. The cut nickel-iron alloy substrate was put into absolute ethanol and ultrasonically degreased for 20 minutes. Then it was put into 3 mol / L hydrochloric acid and ultrasonically treated for 10 minutes, and then put into ultrapure water and ultrasonically treated for 20 minutes. After each stage of ultrasonic treatment, it was repeatedly rinsed three times with ultrapure water. It was taken out and dried at room temperature for later use.

[0044] A mixed solution with a molar concentration ratio of sodium chloride to sodium nitrate of 1:4 was prepared, where the concentration of sodium chloride was 0.005 mol / L. Two-electrode periodic electrochemical treatment was carried out at 27 °C. The pretreated nickel-iron alloy substrate was used as the working electrode, and a graphite rod was used as the counter electrode in the mixed solution. In the first stage, a 20 mA oxidation current was applied for 2 min, and in the second stage, a -20 mA reduction current was applied for 2 min. The reaction was cycled 20 times. After the reaction was completed, it was repeatedly rinsed clean with ultrapure water to obtain nickel-iron composite hydroxide.

[0045] The obtained nickel-iron composite hydroxide was put into a muffle furnace and heated to 350 °C for heat treatment for 1 h, and then cooled to room temperature to obtain the heat-treated nickel-iron oxygen evolution electrode.

[0046] The nickel-iron oxygen evolution electrode prepared above was used for electrocatalytic oxygen evolution reaction. The specific steps were as follows: A three-electrode system was constructed, where the working electrode was the nickel-iron oxygen evolution electrode, the reference electrode was the mercury / mercurous chloride electrode, and the counter electrode was the titanium ruthenium electrode. The OER performance was tested in a 1 M KOH solution. The overpotential at 10 mA / cm 2 was 317 mV, and the overpotential at 1000 mA / cm 2 was only 856 mV. (The data is not compensated for resistance). The test results show that when a solution without tungstate was used during electrochemical redox, the OER performance was worse than that of Example 2, indicating that the introduction of tungstate greatly improved the OER activity.

[0047] Comparative Example 2

[0048] In this comparative example, the difference from Example 1 is that heat treatment is not adopted. The nickel-iron alloy is cut into pieces with an effective area of 1 cm * 1 cm. The cut nickel-iron alloy substrate is put into absolute ethanol and ultrasonically degreased for 20 minutes, then put into 3 mol / L hydrochloric acid and ultrasonically treated for 10 minutes, and then put into ultrapure water and ultrasonically treated for 20 minutes. After each stage of ultrasonic treatment, it is repeatedly rinsed three times with ultrapure water. Take it out and dry it at room temperature for later use.

[0049] A mixed solution with a molar concentration ratio of sodium chloride, sodium nitrate, and sodium tungstate of 1:4:4 is prepared, where the concentration of sodium chloride is 0.005 mol / L. Two-electrode periodic electrochemical treatment is carried out at 27 °C. The pretreated nickel-iron alloy substrate is used as the working electrode, and a graphite rod is used as the counter electrode in the mixed solution. In the first stage, a 5 mA oxidation current is applied for 2 min, and in the second stage, a -5 mA reduction current is applied for 2 min. The cycle period is 80 cycles of reaction. After the reaction is completed, it is repeatedly rinsed with ultrapure water to obtain nickel-iron-tungsten composite hydroxide.

[0050] The nickel-iron-tungsten composite hydroxide prepared above is used for electrocatalytic oxygen evolution reaction. The specific steps are as follows: A three-electrode system is constructed, where the working electrode is the nickel-iron-tungsten composite hydroxide, the reference electrode is the mercury / mercurous chloride electrode, and the counter electrode is the titanium ruthenium electrode. The OER performance is tested in a 1 M KOH solution. When the current density is 10 mA / cm 2 the overpotential is only 227 mV, and when the current density is 1000 mA / cm 2 the overpotential is only 826 mV. (The data has not been compensated for resistance). The results show that this material has good OER activity.

[0051] Figure 5 The linear sweep voltammetry cycle diagram of a nickel-iron-tungsten composite hydroxide obtained in Comparative Example 2 at 1 M KOH and 27 °C is shown. As the number of cycle test periods increases, the performance deteriorates, indicating that the OER stability of the sample without heat treatment needs to be improved.

[0052] The above is only the preferred embodiment of the present invention. The protection scope of the present invention is not limited to the above embodiments. All process schemes that have no substantial difference from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A preparation method of a nickel-iron-tungsten oxygen evolution electrode, characterized in that nickel-iron-tungsten composite hydroxide is in-situ grown on a conductive substrate at room temperature by an electrochemical oxidation-reduction method, and a nickel-iron-tungsten composite oxide oxygen evolution catalytic material is formed by subsequent heat treatment, improving the oxygen evolution activity and stability. The preparation method of the nickel-iron-tungsten oxygen evolution electrode includes the following steps: (1) The conductive substrate is pretreated by degreasing, pickling, and water washing in sequence; (2) Using a nickel-iron alloy substrate as the working electrode, electrochemical etching treatment is carried out in a mixed solution of tungstate, nitrate, and chloride to obtain nickel-iron-tungsten composite hydroxide. The electrochemical etching treatment includes cyclic electrochemical oxidation treatment and electrochemical reduction treatment; (3) After the obtained nickel-iron-tungsten composite hydroxide is rinsed clean, it is put into a muffle furnace for heat treatment to obtain nickel-iron-tungsten composite oxide, that is, the nickel-iron-tungsten oxygen evolution electrode.

2. The preparation method according to claim 1, wherein, The conductive substrate selected is a nickel-iron alloy mesh.

3. The preparation method according to claim 1, wherein The tungstate includes sodium tungstate, ammonium tungstate, or ammonium metatungstate. The concentration of the tungstate is 0.001 - 0.05 mol / L.

4. The preparation method according to claim 1, characterized in that, The chloride includes one or two of sodium chloride, potassium chloride, ammonium chloride, nickel chloride, and iron chloride. The concentration of the chloride is 0.001 - 0.1 mol / L.

5. The preparation method according to claim 1, characterized in that, The nitrate includes one or two of sodium nitrate, potassium nitrate, nickel nitrate, and iron nitrate. The concentration of the nitrate is 0.001 - 0.1 mol / L.

6. The preparation method according to claim 1, wherein The current density of the electrochemically oxidative treatment is 2 to 50 mA / cm 2 , and the single-time of the electrochemically oxidative treatment is 1 to 20 min.

7. The preparation method according to claim 1, characterized in that, The current density of the electrochemically reduction treatment is -2 to -50 mA / cm 2 , and the time for a single electrochemically reduction treatment is 1 to 20 min.

8. The preparation method according to claim 1, characterized in that, The number of cycles of the cycle is 5 - 100.

9. The preparation method according to claim 1, characterized in that, The temperature of the heat treatment is 100°C - 380°C, and the time of the heat treatment is 1 h - 12 h.

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