A nickel-iron-based oxygen evolution electrode and its preparation method and application

Abstract

The present invention provides a nickel-iron-based oxygen evolution electrode and a preparation method and application thereof, belonging to the field of hydrogen energy technology. The present invention uses a nickel-iron alloy substrate as a working electrode, performs electrochemical surface reconstruction treatment in a mixed solution of molybdate and chloride, and during the electrochemical oxidation process, the nickel-iron alloy substrate dissolves nickel and iron ions, while electrochemical oxidation of chloride ions occurs to form active chlorine, and nickel and iron ions are chemically etched out, and during the electrochemical reduction process, the electrode cathode generates hydroxide, and the nickel and iron ions combine with molybdate and hydroxide to form nickel-iron-molybdenum oxide, and during the next electrochemical oxidation process, the nickel-iron-molybdenum oxide is oxidized to form nickel-iron-molybdenum hydroxide oxide, and part of the molybdenum is dissolved, so as to achieve the regulation of the surface composition, valence state and structure of the nickel-iron alloy substrate, which not only improves the current density, but also improves the stability of the electrode, and the whole process can be carried out at room temperature, and the method is simpler and controllable.

Description

Technical Field

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

[0002] Hydrogen production from water electrolysis using renewable electricity is an effective way to achieve green hydrogen production, and is also a key development path for the development of the hydrogen energy industry in countries around the world. Proton exchange membrane water electrolysis, alkaline water electrolysis, alkaline anion exchange membrane water electrolysis and solid oxide water electrolysis are the four main methods of hydrogen production by electrolysis. Among them, alkaline water electrolysis is the main method of commercial hydrogen production by water electrolysis, with the advantages of relatively low cost and large scale. Water electrolysis is mainly composed of anode oxygen evolution reaction (OER) and cathode hydrogen evolution reaction (HER), among which the overpotential loss of anode OER is the main factor causing the high power consumption of hydrogen production by water electrolysis, and the low current density affects the hydrogen production rate of hydrogen production equipment by electrolysis.

[0003] In order to reduce the overvoltage of the oxygen evolution reaction at the anode of alkaline water electrolysis hydrogen production, researchers prepared nickel-iron electrocatalysts to reduce the OER overpotential based on the traditional nickel oxygen evolution electrode. Chinese patent CN202010597907.6 discloses a method for preparing a high-performance nickel-iron-based oxygen evolution electrocatalytic nanocomposite material, which is a Ni3S4 / FeS2 composite material with a cross-linked uniform nanosheet structure and a size of 200-300nm; comprising the following steps: (1) dissolving an iron source and a nickel source in an alkaline environment solvent and stirring evenly, and performing a hydrothermal reaction in an autoclave to obtain a primary product; the hydrothermal reaction temperature is 120°C and the hydrothermal reaction time is 6h; (2) further sulfiding the obtained primary product through a hydrothermal reaction, washing the product, and drying it to obtain a high-performance Ni3S4 / FeS2 oxygen evolution electrocatalytic material; the hydrothermal reaction temperature is 90°C and the hydrothermal reaction time is 9h. This patent requires two hydrothermal steps to prepare a nickel-iron-based oxygen evolution electrocatalytic nanocomposite material, especially the first step is higher than 100°C, and there are high temperature and high pressure reaction conditions. In addition, the nickel-iron-based oxygen evolution electrocatalytic nanocomposite prepared by the patent is a powder material, which requires the introduction of a binder later to stably coat it on a conductive substrate to serve as an oxygen evolution electrode. Chinese patent CN202310037653.6 discloses a nickel-iron oxyhydroxide oxygen evolution electrode and a preparation method thereof, wherein a conductive substrate is reacted in a high-temperature and high-pressure hydrothermal reactor containing nickel salts, iron salts and high-valent metal salts, and a nickel-iron M (M = chromium, molybdenum, tungsten) composite oxide is directly grown in situ on the conductive substrate, and then the electrode is placed in an alkaline solution containing chloride ions, and a positive potential anodic oxidation process is applied to remove the high-valent metal M element in the composite oxide, thereby realizing the preparation of a nickel-iron oxyhydroxide oxygen evolution electrode with high OER activity. The preparation process directly loads the nickel-iron-based catalyst in situ, avoiding the use of a binder, but the preparation process of this method requires a high-temperature and high-pressure hydrothermal step to load the precursor nickel-iron M composite oxide.

[0004] In summary, the current nickel-iron-based oxygen evolution electrodes have a complicated preparation process, especially the high temperature and high pressure hydrothermal reaction process, which affects the safety of the industrial preparation of the electrode. How to use a simple, reliable and controllable method to introduce highly active components while improving the OER stability has become the main development direction of the current nickel-iron-based oxygen evolution electrodes. Summary of the invention

[0005] The purpose of the present invention is to provide a nickel-iron-based oxygen evolution electrode and its preparation method and application. The preparation method provided by the present invention does not require a high temperature and high pressure hydrothermal process, the method is simple, the controllability is strong, and the prepared electrode has high current density and high stability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a nickel-iron based oxygen evolution electrode, comprising:

[0008] A nickel-iron alloy substrate is used as a working electrode, and an electrochemical surface reconstruction treatment is performed in a mixed solution of molybdate and chloride to obtain a nickel-iron-based oxygen evolution electrode; the electrochemical surface reconstruction treatment includes cyclic electrochemical oxidation treatment and electrochemical reduction treatment.

[0009] Preferably, the molybdate comprises sodium molybdate or ammonium molybdate.

[0010] Preferably, the concentration of molybdate in the mixed solution of molybdate and chloride is 0.001-0.05 mol / L.

[0011] Preferably, the chloride includes one or two of sodium chloride, potassium chloride, ammonium chloride, nickel chloride and ferric chloride.

[0012] Preferably, the concentration of chloride in the mixed solution of molybdate and chloride is 0.001-0.1 mol / L.

[0013] Preferably, the potential of the electrochemical oxidation treatment is 1 to 5 V, and the time of the electrochemical oxidation treatment is 1 to 20 min.

[0014] Preferably, the potential of the electrochemical reduction treatment is -1 to -5 V, and the time of the electrochemical reduction treatment is 0.5 to 10 min.

[0015] Preferably, the number of cycles of the cycle is 2-60.

[0016] The present invention provides a nickel-iron based oxygen evolution electrode prepared by the preparation method described in the above technical scheme.

[0017] The present invention also provides the use of the nickel-iron based oxygen evolution electrode described in the above technical solution in hydrogen production by electrolysis of water.

[0018] The present invention provides a method for preparing a nickel-iron-based oxygen evolution electrode, comprising: using a nickel-iron alloy substrate as a working electrode, performing an electrochemical surface reconstruction treatment in a mixed solution of molybdate and chloride to obtain a nickel-iron-based oxygen evolution electrode; the electrochemical surface reconstruction treatment includes cyclic electrochemical oxidation treatment and electrochemical reduction treatment. The present invention uses a nickel-iron alloy substrate as a working electrode, cyclically performing electrochemical oxidation treatment and electrochemical reduction treatment in a mixed solution of molybdate and chloride, during the electrochemical oxidation process, the nickel-iron alloy substrate dissolves nickel and iron ions, and electrochemical oxidation of chloride ions occurs to form active chlorine, and nickel and iron ions are chemically etched out, during the electrochemical reduction process, the electrode cathode generates hydroxide, and the nickel and iron ions are combined with molybdate and hydroxide to form nickel-iron-molybdenum oxide, and during the next electrochemical oxidation process, the nickel-iron-molybdenum oxide is oxidized to form a hydroxyl oxide of nickel-iron-molybdenum, and part of the molybdenum is dissolved, so as to achieve the regulation of the surface composition, valence state and structure of the nickel-iron alloy substrate, not only improving the current density, but also improving the stability of the electrode, the whole process can be carried out at room temperature, and the method is simpler and controllable. The results of the embodiment show that the current density reaches 6600-6700A / m when the nickel-iron-based oxygen evolution potential prepared by the present invention is used as the anode, a commercial nickel-based hydrogen evolution cathode and a commercial diaphragm are used, 30% potassium hydroxide is used as the electrolyte, the electrolysis temperature is 90°C, and the single-chamber cell voltage is 1.98V. 2 . DETAILED DESCRIPTION

[0019] The present invention provides a method for preparing a nickel-iron based oxygen evolution electrode, comprising:

[0020] A nickel-iron alloy substrate is used as a working electrode, and an electrochemical surface reconstruction treatment is performed in a mixed solution of molybdate and chloride to obtain a nickel-iron-based oxygen evolution electrode; the electrochemical surface reconstruction treatment includes cyclic electrochemical oxidation treatment and electrochemical reduction treatment.

[0021] Unless otherwise specified, the present invention has no particular limitation on the sources of the raw materials, and commercially available products known to those skilled in the art may be used.

[0022] In the present invention, the nickel-iron alloy substrate is preferably a nickel-iron alloy mesh. The present invention has no particular limitation on the type of the nickel-iron alloy mesh, and the type of nickel-iron alloy mesh well known to those skilled in the art can be used. In the present invention, the nickel-iron alloy mesh preferably includes a nickel-iron composite woven mesh or a foamed nickel-iron mesh. The present invention uses a mesh substrate to improve the utilization efficiency of the electrode and the exposure degree of the active sites.

[0023] The present invention has no special limitation on the size of the nickel-iron alloy substrate, which can be selected according to actual needs. In an embodiment of the present invention, the size of the nickel-iron alloy substrate is preferably 10 cm*10 cm.

[0024] In the present invention, the nickel-iron alloy substrate is preferably pretreated before use; the pretreatment preferably includes alkaline washing, primary water washing, acid washing, secondary water washing and drying performed in sequence.

[0025] In the present invention, the alkali washing preferably uses a mixed solution of sodium carbonate, sodium hydroxide and sodium silicate; in the mixed solution of sodium carbonate, sodium hydroxide and sodium silicate, the concentration of sodium carbonate is preferably 10-30 g / L, more preferably 20 g / L; the concentration of sodium hydroxide is preferably 10-30 g / L, more preferably 20 g / L; the concentration of sodium silicate is preferably 5-15 g / L, more preferably 10 g / L. The present invention has no special limitation on the amount of the mixed solution of sodium carbonate, sodium hydroxide and sodium silicate, as long as it can cover the nickel-iron alloy substrate.

[0026] In the present invention, the temperature of the alkali washing is preferably 20-30°C; the time of the alkali washing is preferably 10-30 minutes, more preferably 20 minutes; the alkali washing is preferably carried out under ultrasonic conditions. The present invention has no special limitation on the power of the ultrasound, and the ultrasonic power familiar to those skilled in the art can be used. In the present invention, the alkali washing is mainly to remove the oil stains on the surface of the nickel-iron alloy substrate. The present invention limits the parameters such as the temperature and time of the alkali washing to the above range, which can fully remove the oil stains on the surface of the nickel-iron alloy substrate.

[0027] The present invention has no special limitation on the operation of the one-time water washing, and the water washing technical scheme well known to those skilled in the art can be adopted.

[0028] In the present invention, the pickling preferably uses an acidic solution; the acidic solution preferably includes hydrochloric acid, sulfuric acid or nitric acid; the concentration of the acidic solution is preferably 0.2-3 mol / L. The present invention has no particular limitation on the amount of the acidic solution, as long as it can cover the nickel-iron alloy substrate.

[0029] In the present invention, the pickling temperature is preferably 20-30°C; the pickling time is preferably 5-30 minutes. In the present invention, the pickling is mainly to remove the oxides on the surface of the nickel-iron alloy substrate. The present invention limits the concentration of the acidic solution, the temperature and time of the pickling to the above ranges, and can fully remove the oxides on the surface of the nickel-iron alloy substrate.

[0030] The present invention has no special limitation on the operation of the secondary water washing, and the water washing technical scheme well known to those skilled in the art can be adopted.

[0031] The present invention has no special limitation on the drying operation, and any drying technical solution well known to those skilled in the art may be used.

[0032] The present invention preferably uses a titanium electrode or a graphite electrode as the counter electrode.

[0033] In the present invention, the molybdate preferably includes sodium molybdate or ammonium molybdate; the concentration of molybdate in the mixed solution of molybdate and chloride is preferably 0.001-0.05 mol / L, more preferably 0.01-0.03 mol / L. The present invention limits the concentration of molybdate to the above range, which can form a sufficient surface active layer with nickel-iron ions without causing a large amount of reagent waste, thereby further improving the electrode performance.

[0034] In the present invention, the chloride preferably includes one or two of sodium chloride, potassium chloride, ammonium chloride, nickel chloride and ferric chloride; the concentration of chloride in the mixed solution of molybdate and chloride is preferably 0.001-0.1 mol / L, more preferably 0.02-0.04 mol / L. The present invention limits the concentration of chloride to the above range, which can have a suitable etching degree on the nickel-iron alloy substrate and further improve the electrode performance.

[0035] In the present invention, the potential of the electrochemical oxidation treatment is preferably 1 to 5V (potential compared to a saturated calomel electrode), more preferably 2 to 2.5V; the time of the electrochemical oxidation treatment is preferably 1 to 20min, more preferably 2 to 5min. In the present invention, during the electrochemical oxidation treatment, nickel and iron ions are dissolved from the nickel-iron alloy matrix, and electrochemical oxidation of chloride ions occurs to form active chlorine, and nickel and iron ions are chemically etched out. The present invention limits the potential and time of the electrochemical oxidation treatment within the above range, which can form more nickel and iron ions, and is conducive to the subsequent reaction.

[0036] In the present invention, the potential of the electrochemical reduction treatment is preferably -1 to -5V (potential compared to saturated calomel electrode), more preferably -1.5 to -3V; the time of the electrochemical reduction treatment is preferably 0.5 to 10min, more preferably 1 to 5min. In the present invention, during the electrochemical reduction treatment, hydroxide is generated at the negative electrode of the electrode, and nickel and iron ions combine with molybdate and hydroxide to form nickel-iron-molybdenum oxide. In the next electrochemical oxidation process, the nickel-iron-molybdenum oxide is oxidized to form nickel-iron-molybdenum hydroxide oxide, and part of the molybdenum is dissolved. The present invention limits the potential and time of the electrochemical reduction treatment within the above range, which can form more nickel-iron-molybdenum oxide and further improve the electrode performance.

[0037] In the present invention, the number of cycles is preferably 2 to 60, more preferably 10 to 30. The present invention limits the number of cycles to the above range, which can achieve the regulation of the surface composition, valence and structure of the nickel-iron alloy matrix, and further improve the electrode performance.

[0038] After the electrochemical surface reconstruction treatment is completed, the present invention preferably sequentially washes and dries the electrode after the electrochemical surface reconstruction treatment to obtain a nickel-iron-based oxygen evolution electrode.

[0039] The present invention has no special limitation on the washing and drying operations, and the washing and drying technical solutions well known to those skilled in the art can be adopted.

[0040] The present invention adopts a voltage step method, takes a nickel-iron alloy substrate as a working electrode, cyclically performs electrochemical oxidation treatment and electrochemical reduction treatment in a mixed solution of molybdate and chloride, controls various process parameters, and realizes regulation and control of the surface composition, valence state and structure of the nickel-iron alloy substrate, which not only improves the current density but also improves the stability of the electrode, and the whole process can be carried out at room temperature, and the method is simpler and controllable.

[0041] The present invention provides a nickel-iron based oxygen evolution electrode prepared by the preparation method described in the above technical scheme.

[0042] The nickel-iron-based oxygen evolution electrode prepared by the present invention has high current density and stability when producing hydrogen by electrolyzing water.

[0043] The present invention also provides the use of the nickel-iron based oxygen evolution electrode described in the above technical solution in hydrogen production by electrolysis of water.

[0044] The present invention has no special limitation on the operation of using the nickel-iron based oxygen evolution electrode in producing hydrogen by electrolysis of water, and the technical scheme of using the oxygen evolution electrode in producing hydrogen by electrolysis of water well known to those skilled in the art can be adopted.

[0045] The nickel-iron-based oxygen evolution electrode provided by the present invention can significantly increase the current density at the same voltage and reduce the overpotential when applied to hydrogen production by electrolysis of water, which helps to increase the hydrogen production rate of alkaline water hydrogen production equipment at the same hydrogen production power consumption and reduce the hydrogen production power consumption and cost.

[0046] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example 1

[0048] (1) A commercial nickel-iron woven mesh having a size of 10 cm*10 cm is subjected to ultrasonic degreasing treatment at room temperature for 20 min in a mixed solution of 20 g / L sodium carbonate-20 g / L sodium hydroxide-10 g / L sodium silicate. After the degreasing is completed, the residual degreasing liquid is washed away with deionized water; the degreasing nickel-iron woven mesh is then pickled in a 10 g / L HCl solution at room temperature for 10 min. After the pickling is completed, the nickel-iron woven mesh is rinsed with deionized water and dried;

[0049] (2) Using the degreased and pickled nickel-iron woven mesh as the working electrode and the commercial titanium mesh as the auxiliary electrode, in a mixed solution containing 0.03 mol / L sodium molybdate and 0.02 mol / L sodium chloride, a positive potential of 2.5 V was applied for 2 min, and then a negative potential of -3.0 V was applied for 1 min, and this was repeated 30 times. After the electrochemical surface reconstruction treatment was completed, it was rinsed with deionized water and dried at 80°C to obtain a nickel-iron woven mesh with nickel-iron-molybdenum composite oxide-hydroxy oxide reconstructed on the surface. The nickel-iron woven mesh with nickel-iron-molybdenum composite oxide-hydroxy oxide was used as the nickel-iron-based oxygen evolution electrode 1.

[0050] The nickel-iron-based oxygen evolution electrode 1 prepared in this embodiment was cut and used as an anode in a circular plate-frame electrolytic cell with an effective diameter of 10 cm. A commercial nickel-based hydrogen evolution cathode and a commercial diaphragm were used. The electrolyte was 30% potassium hydroxide, the electrolysis temperature was 90°C, the single-chamber cell voltage was 1.98V, and the current density reached 6500-6600A / m 2 , and the current density remains basically stable over time, demonstrating the characteristics of low voltage, high current density and high stability hydrogen production by electrolysis.

[0051] Example 2

[0052] The degreasing and pickling process is consistent with that in Example 1. A commercial nickel-iron woven mesh with a size of 10 cm*10 cm after degreasing and pickling is used as the working electrode, and a commercial titanium mesh is used as the auxiliary electrode. In a mixed solution containing 0.01 mol / L ammonium molybdate and 0.04 mol / L ammonium chloride, a positive potential of 2.0 V is applied for 3 min, and then a negative potential of -1.5 V is applied for 1 min. This is repeated 10 times. After the electrochemical surface reconstruction treatment is completed, it is rinsed with deionized water and dried at 80°C to obtain a nickel-iron woven mesh with nickel-iron-molybdenum composite oxide-hydroxy oxide reconstructed on the surface. The nickel-iron woven mesh with nickel-iron-molybdenum composite oxide-hydroxy oxide is used as the nickel-iron-based oxygen evolution electrode 2.

[0053] The nickel-iron-based oxygen evolution electrode 2 prepared in this embodiment was cut and used as an anode in a circular plate-frame electrolytic cell with an effective diameter of 10 cm. A commercial nickel-based hydrogen evolution cathode and a commercial diaphragm were used. The electrolyte was 30% potassium hydroxide, the electrolysis temperature was 90°C, the single-chamber cell voltage was 1.98V, and the current density reached 6600-6700A / m 2, and the current density remains basically stable over time, demonstrating the characteristics of low voltage, high current density and high stability hydrogen production by electrolysis.

[0054] Comparative Example 1

[0055] The nickel-iron foam mesh with a size of 10 cm*10 cm was only subjected to degreasing and pickling treatment, wherein the degreasing and pickling process was consistent with that in Example 1, and the nickel-iron foam mesh oxygen-evolving electrode after degreasing and pickling was cut and used as an anode in a circular plate-frame electrolytic cell with an effective diameter of 10 cm, the electrolyte was 30% potassium hydroxide, the electrolysis temperature was 90°C, the single-chamber cell voltage was 1.98V, and the current density was only 3300-3500A / m 2 .

[0056] Compared with Examples 1 and 2, it is demonstrated that the nickel-iron-molybdenum oxide-hydroxy oxide electrode prepared by the method of the present invention can significantly improve the current density of electrolytic hydrogen production under the same voltage in the application of alkaline water electrolysis to produce hydrogen, which helps to increase the hydrogen production rate of alkaline water hydrogen production equipment under the same hydrogen production power consumption and reduce the cost of hydrogen production.

[0057] Comparative Example 2

[0058] A commercial nickel-plated ruthenium mesh electrode was used as the oxygen anode. After cutting, it was used in a circular plate-frame electrolytic cell with an effective diameter of 10 cm. The electrolyte was 30% potassium hydroxide, the electrolysis temperature was 90°C, the single-chamber cell voltage was 1.98V, and the current density was 6700-6800A / m 2 .

[0059] Compared with Example 1 and Example 2, it is shown that the electrode prepared by the method of the present invention achieves the oxygen evolution performance of commercial precious metal ruthenium electrodes, which helps to reduce the cost of electrolytic hydrogen production equipment.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-iron based oxygen evolution electrode, comprising: A nickel-iron alloy substrate is used as a working electrode, and an electrochemical surface reconstruction treatment is performed in a mixed solution of molybdate and chloride to obtain a nickel-iron based oxygen evolution electrode. The electrochemical surface reconstruction treatment includes cyclic electrochemical oxidation treatment and electrochemical reduction treatment; The concentration of molybdate in the mixed solution of molybdate and chloride is 0.001-0.05 mol / L; the concentration of chloride in the mixed solution of molybdate and chloride is 0.001-0.1 mol / L; the potential of the electrochemical oxidation treatment is 1-5 V, and the time of the electrochemical oxidation treatment is 1-20 min; the potential of the electrochemical reduction treatment is -1-5 V, and the time of the electrochemical reduction treatment is 0.5-10 min; the number of cycles of the cycle is 2-60.

2. The preparation method according to claim 1, characterized in that: The molybdate includes sodium molybdate or ammonium molybdate.

3. 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 ferric chloride.

4. A nickel-iron based oxygen evolution electrode prepared by the preparation method according to any one of claims 1 to 3.

5. Application of the nickel-iron based oxygen evolution electrode according to claim 4 in hydrogen production by electrolysis of water.