Method for preparing oxygen evolution electrode, oxygen evolution electrode and electrolytic cell

Abstract

The present disclosure relates to a method for preparing an oxygen evolution electrode, an oxygen evolution electrode and an electrolytic cell. The method (100) comprises: preparing a thin film on the surface of a conductive substrate by means of magnetron sputtering, wherein the thin film at least contains a catalyst substance serving as a catalyst in an oxygen evolution reaction and a soluble substance that can dissolve in an alkaline solution (102); and making the thin film come into contact with the alkaline solution, such that the soluble substance dissolves in the alkaline solution, so that a porous catalyst layer consisting of the catalyst substance is formed on the surface of the conductive substrate, and the conductive substrate and the porous catalyst layer form an oxygen evolution electrode (104). The method of the present disclosure can improve the catalytic activity and stability of an oxygen evolution electrode, and facilitates large-scale oxygen evolution electrode preparation, and can effectively reduce the production cost and the application cost.

Description

Method for preparing oxygen evolution electrode, oxygen evolution electrode and electrolytic cell Technical Field

[0001] The embodiments of the present disclosure generally relate to the technical field of electrocatalysis and water electrolysis for hydrogen production, and in particular to a method for preparing an oxygen evolution electrode, an oxygen evolution electrode, and an electrolyzer. Background Art

[0002] With the dwindling availability of natural energy and the rapidly increasing demand for it, the development of new energy sources has become a research hotspot. In the search for efficient and sustainable energy conversion and storage solutions, hydrogen, as a green, clean, and efficient renewable energy source, has emerged as the most promising energy option. Among the many hydrogen production methods, water electrolysis is recognized as a pollution-free and effective method.

[0003] The process of hydrogen production by water electrolysis includes hydrogen evolution reaction and oxygen evolution reaction (OER), among which OER is an essential and decisive step in many new energy conversion and storage processes / devices (e.g., solar water splitting, rechargeable metal-air batteries, renewable fuel cells, and water electrolysis for hydrogen production). However, OER involves a complex multi-step proton-coupled electron transfer process and the formation of oxygen-oxygen bonds, resulting in slow reaction kinetics and harsh reaction conditions, requiring catalysts to accelerate the reaction. Ruthenium dioxide and iridium dioxide are currently known OER catalysts with low overpotential and Tafel slope, but their high cost, scarcity of raw materials and stability hinder their large-scale industrial application.

[0004] Compared with single nickel (Ni) materials as OER catalysts, nickel-iron (NiFe) two-component materials have higher OER catalytic activity due to the synergistic effect of Fe, making them oxygen evolution electrode materials with industrial prospects. The application of NiFe-related oxygen evolution electrodes in the field of water electrolysis is beneficial to reducing the overpotential of the electrode, thereby reducing the energy consumption of water electrolysis, which is beneficial to reducing energy consumption. Common preparation methods for NiFe-related oxygen evolution electrodes include ultrasonic spraying, in situ growth, etc. The oxygen evolution electrodes prepared by these methods have high OER activity, but poor stability and are difficult to use for large-scale production. Therefore, how to obtain an oxygen evolution electrode with high activity and high stability is still a challenging topic. Summary of the Invention

[0005] According to the first aspect of the present disclosure, a method for preparing an oxygen evolution electrode is provided. The method comprises: using magnetron sputtering to prepare a thin film on the surface of a conductive substrate, wherein the thin film contains at least a catalyst substance that acts as a catalyst in the oxygen evolution reaction and a soluble substance that can be dissolved in an alkaline solution; and contacting the thin film with an alkaline solution to dissolve the soluble substance in the alkaline solution, so that a porous catalyst layer composed of the catalyst substance is formed on the surface of the conductive substrate, and the conductive substrate and the porous catalyst layer form an oxygen evolution electrode. The oxygen evolution electrode prepared using this method can improve the catalytic activity and stability of oxygen evolution, and this method is easy to prepare oxygen evolution electrodes on a large scale, which can effectively reduce the production cost and application cost of the oxygen evolution electrode.

[0006] In some embodiments, the soluble substance includes at least one of aluminum, zinc, silicon, silicon oxide, aluminum oxide, and zinc oxide.

[0007] In some embodiments, the catalyst material includes at least one of the following: iron nickel oxide, iron oxide, nickel oxide.

[0008] In some embodiments, the iron-nickel oxide includes nickel ferrite.

[0009] In some embodiments, forming a thin film includes forming the thin film on a conductive substrate using a sputtering target during magnetron sputtering. The sputtering target includes a first type of target and a second type of target. The first type of target is configured to form a catalyst material in the thin film during magnetron sputtering. The second type of target is configured to form a soluble material in the thin film during magnetron sputtering.

[0010] In some embodiments, the first type of target material includes a target material formed of at least one of the following substances: iron-nickel oxide, elemental iron, iron oxide, elemental nickel, or nickel oxide.

[0011] In some embodiments, the second type of target material includes a target material formed of at least one of the following substances: zinc, zinc oxide, silicon, silicon oxide, aluminum, or aluminum oxide.

[0012] In some embodiments, the distance between the sputtering target and the conductive substrate is in the range of 4 cm to 12 cm, the sputtering power of the magnetron sputtering is in the range of 80 W to 250 W, the sputtering time is in the range of 2 h to 6 h, and the sputtering gas pressure is in the range of 0.5 Pa to 3 Pa.

[0013] In some embodiments, the conductive substrate is selected from at least one of nickel foam, nickel felt, nickel mesh, titanium felt, and titanium foam.

[0014] In some embodiments, the pore size of the porous catalyst layer is in the range of 10 nm to 800 nm.

[0015] In some embodiments, the thickness of the porous catalyst layer is greater than 200 nm.

[0016] In some embodiments, the molar content of soluble substances in the film is in the range of 5% to 45%.

[0017] According to a second aspect of the present disclosure, an oxygen evolution electrode is further provided, wherein the oxygen evolution electrode is prepared by the method according to the first aspect of the present disclosure.

[0018] According to a third aspect of the present disclosure, an electrolytic cell is also provided. The electrolytic cell is used to electrolyze an electrolyte to produce oxygen and hydrogen. The electrolytic cell comprises: a cathode for the hydrogen evolution reaction; an anode for the oxygen evolution reaction, the anode being composed of the oxygen evolution electrode according to the second aspect of the present disclosure; and a conductive diaphragm separating the anode and cathode.

[0019] In some embodiments, the electrolyte comprises an alkaline solution.

[0020] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. In the various drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0022] FIG1 shows a flow chart of a method for preparing an oxygen evolution electrode according to an embodiment of the present disclosure.

[0023] FIG2 shows a schematic diagram of the structure of an electrolytic cell according to an embodiment of the present disclosure.

[0024] FIG3 shows a schematic diagram of a three-electrode system for testing the oxygen evolution activity of an oxygen evolution electrode according to an embodiment of the present disclosure.

[0025] FIG4 schematically shows half-cell OER polarization curves obtained by electrochemically testing the oxygen evolution electrode according to the embodiment of the present disclosure and the oxygen evolution electrode of the comparative example using a three-electrode system.

[0026] FIG5 schematically shows single cell polarization curves obtained by electrochemically testing an oxygen evolution electrode according to an embodiment of the present disclosure and an oxygen evolution electrode of a comparative example using a two-electrode system.

[0027] FIG6 schematically shows the results of a stability test of an oxygen evolution electrode according to an embodiment of the present disclosure using a two-electrode system. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0029] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "one example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or identical objects.

[0030] As previously described, NiFe dual-component materials exhibit high oxygen evolution catalytic activity, enabling them to reduce electrode overpotential when used in water electrolysis. However, NiFe-based oxygen evolution electrodes prepared by methods such as ultrasonic spray coating and in-situ growth suffer from poor stability and are difficult to manufacture on a large scale. Consequently, existing methods for preparing oxygen evolution electrodes suffer from complex preparation processes, low catalytic activity, and poor stability.

[0031] To at least partially address one or more of the aforementioned and other potential issues, exemplary embodiments of the present disclosure provide a method for preparing an oxygen evolution electrode. The method comprises: using magnetron sputtering to form a thin film on the surface of a conductive substrate, the thin film containing at least a catalyst substance that acts as a catalyst in the oxygen evolution reaction and a soluble substance that is soluble in an alkaline solution; and contacting the thin film with an alkaline solution to dissolve the soluble substance in the alkaline solution, thereby forming a porous catalyst layer composed of the catalyst substance on the surface of the conductive substrate. The conductive substrate and the porous catalyst layer form the oxygen evolution electrode.

[0032] Figure 1 shows a flow chart of a method 100 for preparing an oxygen evolution electrode according to an embodiment of the present disclosure. It should be understood that the method shown in Figure 1 may also include additional steps not shown, and the scope of the present disclosure is not limited in this respect.

[0033] As shown in FIG1 , in method 100 , at 102, magnetron sputtering is used to form a thin film on the surface of a conductive substrate. The thin film contains at least a catalyst material that serves as a catalyst in the oxygen evolution reaction and a soluble substance that is soluble in an alkaline solution. In one embodiment, the catalyst material may include at least one of the following: iron-nickel oxide (such as nickel ferrite), iron oxide, and nickel oxide. The soluble substance may include at least one of aluminum, zinc, silicon, silicon oxide, aluminum oxide, and zinc oxide.

[0034] To this end, a first type of target material and a second type of target material can be provided as sputtering targets in magnetron sputtering. The first type of target material can be configured as a catalyst material in a thin film formed in magnetron sputtering, and the second type of target material can be configured as a soluble material in a thin film formed in magnetron sputtering. For example, the first type of target material may include a target material formed from at least one of the following substances: iron-nickel oxide, iron element, iron oxide, nickel element, or nickel oxide. The second type of target material may include a target material formed from at least one of the following substances: zinc element, zinc oxide, silicon element, silicon oxide, aluminum element, or aluminum oxide.

[0035] Prior to magnetron sputtering, the conductive substrate may be cleaned to obtain a cleaned conductive substrate. For example, the conductive substrate may be treated by ultrasonic cleaning using deionized water, hydrochloric acid, anhydrous ethanol, etc., in sequence, and repeated 3 to 5 times to remove grease, organic matter, and oxides on the surface of the conductive substrate.

[0036] The conductive substrate can then be placed in a growth chamber, and the growth chamber can be evacuated to a background vacuum. A sputtering target comprising a first target material and a second target material can then be placed in the growth chamber. The distance between the sputtering target and the conductive substrate is in the range of 4 cm to 12 cm, preferably in the range of 4 cm to 10 cm, and more preferably in the range of 4 cm to 8 cm.

[0037] Then, a protective gas, such as argon, is filled into the growth chamber. Oxygen can also be simultaneously filled into the growth chamber so that the first type target material and / or the second type target material react with the oxygen to generate iron-nickel oxide and / or oxide as a soluble substance during magnetron sputtering.

[0038] The sputtering power is in the range of 80 W to 250 W, preferably in the range of 80 W to 180 W, more preferably in the range of 80 W to 120 W. The sputtering time is in the range of 2 h to 6 h, preferably in the range of 2 h to 5 h, more preferably in the range of 2 h to 4 h. The sputtering gas pressure is in the range of 0.5 Pa to 3 Pa, preferably in the range of 0.5 Pa to 2 Pa, more preferably in the range of 0.5 Pa to 1 Pa.

[0039] During magnetron sputtering, electrons fly toward the substrate under the action of an electric field. During this process, the electrons collide with argon (Ar) atoms in the shielding gas, ionizing them to produce Ar positive ions and new electrons. Under the action of the electric field, the new electrons fly toward the substrate, and the Ar positive ions are accelerated by the electric field toward a sputtering target comprising a first type of target material and a second type of target material, bombarding the surface of the sputtering target material with high energy, causing the sputtering target material to sputter. Neutral atoms or molecules on the surface of the first type of target material (e.g., iron-nickel oxide, iron, iron oxide, nickel, or nickel oxide) and neutral atoms or molecules on the surface of the second type of target material (e.g., zinc, zinc oxide, silicon, silicon oxide, aluminum, or aluminum oxide) gain sufficient kinetic energy to break away from the target material surface and co-deposit on the substrate surface to form a thin film, thereby forming a thin film comprising at least a catalyst substance and a soluble substance soluble in an alkaline solution.

[0040] When using iron or nickel as the first type of target, the iron atoms or nickel atoms sputtered from the target surface can react with the oxygen in the growth chamber to generate corresponding oxides, such as iron oxide or nickel oxide. When using an iron-containing material (e.g., iron or iron oxide) and a nickel-containing material (e.g., nickel or nickel-iron oxide) as the first type of target at the same time, and the first type of target contains iron or nickel, the atoms or molecules sputtered from the first type of target surface can react with the oxygen in the growth chamber to generate iron-nickel oxide. Thus, a catalyst substance for oxygen evolution reaction and formed in the thin film can be generated during the sputtering process.

[0041] When zinc, silicon or aluminum is used as the second type of target material, the zinc atoms, silicon atoms or aluminum atoms sputtered from the surface of the second type of target material can react with the oxygen in the growth chamber to generate corresponding oxides, such as zinc oxide, silicon oxide or aluminum oxide, as soluble substances formed in the thin film.

[0042] After sputtering, the molar content of soluble matter in the formed film is within a range of 5% to 45%. If the molar content of soluble matter is less than 5%, the catalyst layer will not form sufficient voids after alkali washing, which will not help improve the adsorption of hydroxide ions. If the molar content of soluble matter is greater than 45%, the catalyst layer will have excessive voids after alkali washing, which may easily cause the oxygen evolution electrode to collapse during electrolysis. The molar content of soluble matter is preferably within a range of 10% to 30%, and more preferably within a range of 10% to 15%.

[0043] The material of the conductive substrate is not particularly limited. A conductive substrate composed of at least one selected from the group consisting of nickel, iron, mild steel, stainless steel, vanadium, molybdenum, copper, silver, manganese, platinum group, graphite, and chromium can be used. An alloy composed of two or more metals or a mixture of two or more conductive substances can also be used. Among them, from the aspects of the conductivity of the substrate and the resistance in the use environment, materials such as titanium, nickel, titanium-based alloys, and nickel-based alloys are preferred as the conductive substrate. In some embodiments, the conductive substrate can be at least one of nickel foam, nickel felt, nickel mesh, titanium felt, and titanium foam to increase the specific surface area of ​​the electrode.

[0044] As an example, iron-nickel oxide or a material capable of forming iron-nickel oxide may be used as target A, including but not limited to iron-nickel oxide (NiFeO x ), iron target, nickel target, etc.; target B is a substance soluble in alkaline solution, including but not limited to Al, Zn, Si, etc. Target A and target B are combined to form a multi-target. Thin films are co-deposited on a conductive substrate by magnetron sputtering of multiple targets under the following conditions: background vacuum is 1×10 -5 Pa~6×10 -5 Pa, the target distance is 4 cm to 12 cm, the sputtering atmosphere is pure argon or a mixture of argon and oxygen, the gas flow rate is 20 sccm to 50 sccm, the sputtering power is 80 W to 250 W, the sputtering time is 2 h to 6 h, and the sputtering pressure is 0.5 Pa to 3 Pa. The molar content of soluble substances such as Zn, Al or Si in the sputtered film is approximately in the range of 5% to 45%.

[0045] At 104, the thin film is contacted with an alkaline solution to dissolve the soluble material in the alkaline solution, forming a porous catalyst layer composed of the catalyst material on the surface of the conductive substrate. The conductive substrate and the porous catalyst layer form an oxygen evolution electrode. As the soluble material in the thin film dissolves in the alkaline solution, a large number of pores are formed in the space originally occupied by the soluble material. In this way, an oxygen evolution electrode with a high specific surface area can be obtained.

[0046] As an example, the oxygen evolution electrode obtained after sputtering can be cleaned under alkaline conditions to remove soluble substances such as Zn, Al or Si in the thin film on the surface of the oxygen evolution electrode that can be dissolved in alkali. The alkaline solution can be a solution of sodium hydroxide, potassium hydroxide or the like. The molar concentration of the alkaline solution (in terms of hydroxide ions, the same below) can be 1 mol / L to 15 mol / L, preferably 3 mol / L to 10 mol / L, and more preferably 5 mol / L to 8 mol / L. If necessary, a hot alkaline solution can be used for cleaning. Taking Zn as an example of a soluble substance, the chemical reaction of the alkaline washing process is as shown in formula (1): Zn+2OH - +2H2O→Zn(OH)42- +H2 (1)

[0047] After the alkaline washing is completed, an oxygen evolution electrode can be obtained, and a porous catalyst layer is provided on the surface of the oxygen evolution electrode, so that the oxygen evolution electrode has a high specific surface area.

[0048] During the sputtering process, the atoms or molecules sputtered from the surface of the first type of target material can be compounded with the atoms or molecules sputtered from the surface of the second type of target material, so that some of the atoms from the second type of target material occupy the positions of the atoms in the catalyst material. As an example, taking the first type of target material as iron and nickel, and the second type of target material as zinc, during the sputtering process, the iron atoms and nickel atoms sputtered from the surface of the first type of target material can react with the oxygen in the growth chamber to form iron-nickel oxide (for example, nickel ferrite). Some of the zinc atoms sputtered from the surface of the second type of target material can occupy the positions of the iron atoms in the iron-nickel oxide. When the oxygen evolution electrode is cleaned under alkaline conditions, the zinc atoms occupying the positions of the iron atoms in the iron-nickel oxide react with the alkaline solution, so that atomic vacancies are generated in the iron-nickel oxide. These atomic vacancies are conducive to OH - The adsorption of ions can enhance the catalytic activity of the oxygen evolution electrode.

[0049] In one embodiment, the pore size of the porous catalyst layer obtained after alkali washing is in the range of 10 nm to 800 nm, preferably in the range of 10 nm to 600 nm, and more preferably in the range of 10 nm to 400 nm. The thickness of the formed porous catalyst layer may be greater than 200 nm. As an example, the pore size of the porous catalyst layer can be measured using gas adsorption, mercury porosimetry, or scanning electron microscopy.

[0050] In this way, a method for preparing a high-performance oxygen evolution anode using magnetron sputtering technology and an alkaline washing process is provided. In this method, a target material that can sputter to form a highly active OER catalyst (for example, iron-nickel oxide) and a target material that can sputter to form a soluble substance (for example, Zn, Al, Si or its oxide) are used as dual targets. Magnetron sputtering technology is used to uniformly deposit the catalyst material and the soluble substance on the surface of a conductive substrate such as nickel foam by controlling the vacuum degree, sputtering time, and sputtering distance in the magnetron sputtering to form a thin film. By preparing a catalyst-containing film by magnetron sputtering, it is possible to achieve stable adhesion of the catalyst to the substrate surface of the oxygen evolution electrode, thereby improving the stability of the oxygen evolution electrode.

[0051] In addition, by co-depositing the catalyst and soluble substances on the surface of the conductive substrate and then removing the soluble substances by reacting with an alkaline solution, the specific surface area of ​​the catalyst layer on the oxygen evolution electrode can be increased, thereby improving the electrolysis performance of the oxygen evolution electrode. On the other hand, the removal of soluble substances can generate atomic vacancies in the catalyst layer, which is beneficial to the formation of hydroxide ions (OH- ) is adsorbed on the surface of the oxygen evolution electrode, thereby improving the catalytic activity of oxygen evolution. Furthermore, the above-mentioned method for preparing the oxygen evolution electrode is simple in process, low in cost, and easy to prepare on a large scale.

[0052] The oxygen evolution electrode according to an embodiment of the present disclosure can be used in anion exchange membrane (AEM) water electrolysis. FIG2 shows a schematic diagram of the structure of an electrolytic cell 200 for water electrolysis according to an embodiment of the present disclosure. It should be noted that FIG2 is merely an example of the electrolytic cell of the present disclosure and is not intended to be limiting.

[0053] As shown in FIG2 , the electrolytic cell 200 may include a cathode 201 for hydrogen evolution reaction, an anode 202 for oxygen evolution reaction, and a conductive diaphragm 203 for separating the anode and the cathode. The anode 202 may be an oxygen evolution electrode prepared by the method 100 described in FIG1 . The conductive diaphragm 203 is an anion exchange membrane that allows hydroxide ions to pass through. The electrolytic cell 200 may be used to electrolyze the electrolyte 204 in the electrolytic cell 200 to produce oxygen and hydrogen. In some embodiments, the electrolyte 204 in the electrolytic cell 200 may include an alkaline solution or pure water. As an example, the alkaline solution may be an aqueous solution of a substance such as sodium hydroxide or potassium hydroxide to increase the OH in the alkaline electrolytic cell. - When direct current is applied to the electrolytic cell 200 filled with the electrolyte 204, water molecules undergo hydrogen evolution reaction and oxygen evolution reaction at the cathode 201 and anode 202, respectively, thereby decomposing into hydrogen and oxygen.

[0054] Because the catalyst layer on anode 202 is deposited on the electrode surface via magnetron sputtering, the catalyst remains stably attached to anode 202 during the oxygen evolution reaction and is not easily removed, thereby improving the stability of the electrolyzer. Furthermore, due to the large specific surface area of ​​the catalyst layer and the presence of atomic vacancies within the catalyst layer, the catalytic activity of the catalyst layer on anode 202 of this electrode cell during the oxygen evolution reaction is enhanced.

[0055] The oxygen evolution electrode according to the embodiment of the present disclosure may be electrochemically tested using a two-electrode system and a three-electrode system.

[0056] When using a two-electrode system for electrochemical testing, the electrolytic cell 200 described above in conjunction with FIG2 can be used as a full-cell alkaline membrane single-cell electrolytic cell to evaluate the water electrolysis activity of the oxygen evolution electrode according to the embodiments of the present disclosure. For example, an anion exchange membrane is used as the conductive diaphragm 203, a 0.5 mm nickel foam is used as the cathode 201, an iron-nickel oxide oxygen evolution electrode according to the embodiments of the present disclosure is used as the oxygen evolution anode 202, and a KOH solution is used as the electrolyte 204. The cathode 201 and anode 202 are respectively attached to both sides of the conductive diaphragm 203. The prepared iron-nickel oxide electrode, nickel foam, and anion exchange membrane form a membrane electrode. The membrane electrode is assembled and fastened using a fixture, and the electrolyte 204 is passed through the fixture. The temperature of the single-cell electrolytic cell 200 is set to 80°C, and the cathode 201 and anode 202 are fed from both sides. The assembled single-cell electrolytic cell 200 is electrochemically polarized using the "Solartron" electrochemical comprehensive testing system.

[0057] Figure 3 shows a schematic diagram of a three-electrode system 300 for testing the oxygen evolution activity of an oxygen evolution electrode according to an embodiment of the present disclosure. The three-electrode system 300 includes a working electrode 301, a reference electrode 302, a counter electrode 303, and an electrolyte 304. The reference electrode 302 is used to accurately study the electrode voltage of the working electrode 301. The working electrode 301, the reference electrode 302, and the electrolyte 304 form a first circuit for testing the electrochemical reaction process of the working electrode. The working electrode 301 and the counter electrode 303 are used to transmit electrons, forming a second circuit.

[0058] The intrinsic activity test of the oxygen evolution electrode according to an embodiment of the present disclosure can be performed in a half-cell using a three-electrode system 300. As an example, a KOH solution is used as the electrolyte 304, the oxygen evolution electrode according to an embodiment of the present disclosure is fixed on a Pt electrode holder as the working electrode 301, a Hg-HgO electrode is used as the reference electrode 302, and a graphite carbon rod is used as the counter electrode 303. The catalyst is tested for OER activity in the KOH solution using a linear voltammetric scan program in the potential window of 1.0V to 1.8V (vs. RHE (reversible hydrogen electrode)).

[0059] The following is a detailed description of the preparation and electrochemical testing process of the oxygen evolution electrode according to the embodiment of the present disclosure and the oxygen evolution electrode of the comparative example.

[0060] Example 1: This example will exemplarily illustrate the technical solution of preparing an oxygen evolution electrode using the method of the embodiment of the present disclosure and performing electrochemical testing on it.

[0061] Step 1: ultrasonically clean a 0.5 mm thick nickel foam substrate using deionized water, 3 mol / L HCl, and anhydrous ethanol in sequence, and repeat this process three times to obtain a treated substrate.

[0062] Step 2: Buy nickel iron oxide (NiFeO x ) material is target material A, and Zn is target material B to form a double target.

[0063] Step 3: Transfer the cleaned substrate to the sample base of the equipment, turn on the mechanical pump to pre-vacuum to 20Pa, turn on the molecular pump to start high vacuum, and after a period of time, the molecular pump can pump the pressure of the reaction chamber to 5×10 -5 Pa, to achieve the vacuum conditions required for the experiment; open the argon flow valve to control the flow rate at 40sccm, and after the gas is introduced for 5 minutes, control the chamber pressure to 1.0Pa through the plate valve; turn on the sputtering power supply, adjust the target A sputtering power supply to 150W, and pre-sputter for 5 minutes to remove impurities on the target surface; then turn on the target B power supply to 150W, and pre-sputter for 5 minutes to remove impurities on the target surface; turn on the target A and target B power supplies again and sputter for a total of 3 hours, where the power of target A is 200W and the power of target B is 100W. After the sputtering is completed, turn off the sputtering power supply.

[0064] Step 4: Soak the obtained electrode in a 3 mol / L KOH solution for 2 h to obtain a porous iron-nickel oxide oxygen evolution electrode.

[0065] Step 5: Test the electrode prepared in Step 4. Using the three-electrode system shown in Figure 3, the intrinsic activity of the prepared porous iron-nickel oxide electrode was tested in a half-cell. KOH solution was used as the electrolyte. The porous iron-nickel oxide electrode prepared in Step 4 was fixed to a Pt electrode holder as the working electrode. A Hg-HgO electrode was used as the reference electrode, and a graphite carbon rod was used as the counter electrode. The OER activity of the catalyst was tested in KOH solution using a linear voltammetric sweep procedure in the potential window of 1.0 V to 1.8 V (vs. RHE).

[0066] Step 6: Test the electrode prepared in step 4. Use the two-electrode system in Figure 2 to evaluate the electrolytic water activity of the prepared porous iron-nickel oxide electrode in an alkaline membrane single-cell electrolyzer. An anion exchange membrane is used as a diaphragm, a 0.5mm nickel foam is used as the cathode, and the porous iron-nickel oxide electrode prepared in step 4 is used as the oxygen evolution electrode as the anode. The cathode and anode electrodes are respectively attached to both sides of the anion exchange membrane. The prepared porous iron-nickel oxide electrode, nickel foam, and anion exchange membrane form a membrane electrode. The membrane electrode is assembled and fastened using a fixture, and KOH electrolyte is passed into the fixture. The electrolytic cell temperature is set to 80°C, and the cathode and anode are fed on both sides. The test is conducted at 1A / cm using a strong electrochemical comprehensive test system. 2 The electrolysis performance of water under .

[0067] Comparative Example 1: This comparative example will exemplarily illustrate the technical solution of preparing an iron-nickel oxide oxygen evolution electrode by spraying and performing electrochemical testing on it.

[0068] Step 1: Disperse the purchased iron-nickel oxide with a particle size of 20 nm to 60 nm into a dispersion of 5 mg / ml, and evenly spray it on the nickel foam by ultrasonic spraying to prepare an electrode.

[0069] Step 2: Test the electrode prepared in step 1. Use the two-electrode system in Figure 2 to evaluate the water electrolysis activity of the iron-nickel oxide electrode in an alkaline membrane single-cell electrolyzer. Use an anion exchange membrane as a diaphragm, 0.5mm nickel foam is used as the cathode, and the iron-nickel oxide electrode prepared in step 1 is used as the oxygen evolution electrode as the anode. The cathode and anode electrodes are respectively attached to both sides of the anion exchange membrane. The prepared iron-nickel oxide electrode, nickel foam, and anion exchange membrane form a membrane electrode. The membrane electrode is assembled and fastened using a fixture, and KOH electrolyte is passed into the fixture. The electrolytic cell temperature is set to 80°C, and the cathode and anode are fed on both sides. Use the power-strong electrochemical comprehensive test system to test at 1A / cm 2 The electrolysis performance of water under .

[0070] Step 3: Test the electrode prepared in Step 1. Using the three-electrode system shown in Figure 3, the intrinsic activity of the prepared iron-nickel oxide electrode was tested in a half-cell. KOH solution was used as the electrolyte. The electrode prepared in Step 1 was fixed to a Pt electrode holder as the working electrode. A Hg-HgO electrode was used as the reference electrode, and a graphite carbon rod was used as the counter electrode. The catalyst OER activity was tested in KOH solution using a linear voltammetric sweep procedure in the potential window of 1.0 V to 1.8 V (vs. RHE).

[0071] Comparative Example 2: This comparative example will exemplarily illustrate the technical solution of preparing an iron-nickel oxide oxygen evolution electrode by a common magnetron sputtering method and performing electrochemical testing on it.

[0072] Step 1: ultrasonically clean a 0.5 mm thick nickel foam substrate using deionized water, 3 mol / L HCl, and anhydrous ethanol in sequence, and repeat this process three times to obtain a treated substrate.

[0073] Step 2: Buy nickel iron oxide (NiFeO x ) The material is target A and target B is not used.

[0074] Step 3: Transfer the cleaned substrate to the sample base of the equipment, turn on the mechanical pump to pre-vacuum to 20Pa, turn on the molecular pump to start high vacuum, and after a period of time, the molecular pump can pump the pressure of the reaction chamber to 5×10 -5Pa, to achieve the vacuum conditions required for the experiment; open the argon flow valve to control the flow rate at 40sccm, and after the gas is introduced for 5 minutes, control the chamber pressure to 1.0Pa through the plate valve; turn on the sputtering power supply, adjust the target A sputtering power supply to 150W, and pre-sputter for 5 minutes to remove impurities on the target surface; then sputter on the substrate for 3 hours with a sputtering power of 200W. After the sputtering is completed, turn off the sputtering power supply.

[0075] Step 4: Test the electrode prepared in Step 3. Using the three-electrode system shown in Figure 3, the intrinsic activity of the prepared iron-nickel oxide electrode was tested in a half-cell. KOH solution was used as the electrolyte. The electrode prepared in Step 3 was fixed to a Pt electrode holder as the working electrode. A Hg-HgO electrode was used as the reference electrode, and a graphite carbon rod was used as the counter electrode. The catalyst OER activity was tested in KOH solution using a linear voltammetric sweep procedure in the potential window of 1.0 V to 1.8 V (vs. RHE).

[0076] Step 5: Test the electrode prepared in step 3. Use the two-electrode system in Figure 2 to evaluate the electrolytic water activity of the iron-nickel oxide electrode in an alkaline membrane single-cell electrolyzer. An anion exchange membrane is used as a diaphragm, a 0.5mm loaded nickel foam is used as the cathode, and the iron-nickel oxide electrode prepared in step 3 is used as the anode as the oxygen evolution electrode. The cathode and anode electrodes are respectively attached to both sides of the anion exchange membrane. The prepared porous iron-nickel oxide electrode, nickel foam, and anion exchange membrane form a membrane electrode. The membrane electrode is assembled and fastened using a fixture, and KOH electrolyte is passed into the fixture. The electrolytic cell temperature is set to 80°C, and the cathode and anode are fed on both sides. Using the power-strong electrochemical comprehensive test system, the test is conducted at 1A / cm 2 The electrolysis performance of water under .

[0077] Figure 4 schematically shows half-cell OER polarization curves obtained by electrochemically testing the oxygen evolution electrode according to an embodiment of the present disclosure, the oxygen evolution electrode of Comparative Example 1, and the oxygen evolution electrode of Comparative Example 2 using the three-electrode system shown in Figure 3. The iron-nickel oxide electrodes prepared in Example 1, Comparative Example 1, and Comparative Example 2 were tested for intrinsic activity using the three-electrode system shown in Figure 3. The curve in Figure 4 shows the relationship between the voltage and current density of the working electrode. At the same current density, the lower the voltage of the working electrode, the better the oxygen evolution performance of the electrode.

[0078] As can be seen from Figure 4, at the same current density, the voltage of the electrode prepared in Example 1 is significantly lower than the voltages of the electrodes prepared in Comparative Examples 1 and 2. This indicates that the electrode prepared by the magnetron sputtering co-deposition process and the alkaline washing process has superior oxygen evolution performance compared to the electrode prepared by spraying and the electrode prepared by magnetron sputtering deposition of a single material.

[0079] Figure 5 schematically shows the single-cell polarization curves obtained by electrochemically testing the oxygen evolution electrode according to the embodiment of the present disclosure, the oxygen evolution electrode of Comparative Example 1, and the oxygen evolution electrode of Comparative Example 2 using the two-electrode system shown in Figure 2. Using the two-electrode system shown in Figure 2, the iron-nickel oxide electrode prepared in Example 1, Comparative Example 1, and Comparative Example 2 is used as the anode, and the same cathode material and the same ion exchange membrane are used to assemble into a single-cell electrolyzer, and the water electrolysis activity test is carried out using the single-cell electrolyzer. Since the same cathode material and the same ion exchange membrane are used in different single-cell electrolyzers, the difference in water electrolysis performance of different single-cell electrolyzers is caused by the difference in oxygen evolution performance of the anode material. The curve in Figure 5 shows the relationship between the voltage required for water electrolysis and the current density. At the same current density, the lower the voltage required for water electrolysis, the better the oxygen evolution performance of the anode material.

[0080] As can be seen from Figure 5, at the same current density, the voltage required for the electrolysis of water in the single-cell electrolyzer assembled with the electrodes prepared in Example 1 is significantly lower than the voltage required for the electrolysis of water in the single-cell electrolyzer assembled with the electrodes prepared in Comparative Examples 1 and 2. In other words, compared with the single-cell electrolyzers assembled with the electrodes prepared in Comparative Examples 1 and 2, the single-cell electrolyzer assembled with the electrodes prepared in Example 1 consumes less energy to obtain the same amount of hydrogen production. This shows that, compared with the electrodes prepared by the spraying method and the electrodes prepared by magnetron sputtering deposition of a single material, the electrodes prepared by the magnetron sputtering co-deposition process and the alkaline washing process have better oxygen evolution performance.

[0081] As can be seen from Figures 4 and 5, according to the method disclosed in the present invention, the electrode performance of the porous iron-nickel oxide electrode prepared by the magnetron sputtering co-deposition process and the alkaline washing process is significantly better than that of the electrode prepared by ordinary magnetron sputtering only depositing the catalyst, and is also significantly better than that of the electrode prepared by the spraying method. This is because soluble substances such as Zn are added during the deposition process, and the soluble substances are subsequently removed by alkaline washing. The sacrificial material gives the electrode a larger specific surface area, which facilitates the transport of ions and increases the reaction activity. In addition, the electrode performance of the porous iron-nickel oxide electrode prepared by the magnetron sputtering co-deposition process and the alkaline washing process is significantly better than that of the electrode prepared by the spraying method. The electrode prepared by the magnetron sputtering method has a larger specific surface area than the sprayed electrode, which is beneficial to improving the catalytic activity. At the same time, the removal of the co-deposited Zn element by alkali washing may create atomic vacancies, so that the substrate of the porous iron-nickel oxide electrode exposes more active sites, improves the intrinsic activity, and is beneficial to OH - adsorption, thereby enhancing the catalytic activity.

[0082] Figure 6 schematically shows the results of a stability test of the oxygen evolution electrode according to an embodiment of the present disclosure using the two-electrode system shown in Figure 2. Using the two-electrode system shown in Figure 2, the iron-nickel oxide electrode prepared in Example 1 was subjected to a stability test. Specifically, the iron-nickel oxide electrode prepared in Example 1 was used as the anode, and suitable cathode materials and ion exchange membranes were selected to assemble into a single-cell electrolyzer, and the single-cell electrolyzer was used to perform multiple test cycles to characterize the stability of the electrolyzer. The same current density mode was used in each cycle test to measure the voltage required for the single-cell electrolyzer to electrolyze water. If the voltage measured after multiple cycle tests drops, it indicates that the electrolysis performance of the single-cell electrolyzer has deteriorated. The curve in Figure 6 shows the change in the voltage required for the single-cell electrolyzer to electrolyze water over time in multiple test cycles.

[0083] As can be seen from Figure 6, in the cycle test of up to 130 hours, the voltage required for the electrolysis of water in the single-cell electrolyzer assembled by the porous iron-nickel oxide electrode prepared in Example 1 did not drop significantly. This shows that the single-cell electrolyzer has stable electrolysis performance and can maintain stable operation for a long time. This further shows that the oxygen evolution electrode according to the embodiment of the present disclosure has excellent stability. This is because the catalyst layer prepared by magnetron sputtering is obtained by atomic deposition, has a large bonding force with the substrate, and is not easy to fall off from the substrate. In contrast, the electrode catalyst layer prepared by spraying relies on the adhesion of a high molecular polymer to the substrate, has a relatively weak bonding force with the substrate, and is easy to fall off from the substrate.

[0084] Thus, the method according to the present invention can be used to quickly prepare a porous iron-nickel oxide oxygen evolution electrode with high activity and high stability. The oxygen evolution electrode prepared according to the method of the present invention can reduce the electrolysis voltage and reduce the energy consumption of water electrolysis. The method of the present invention uses a magnetron sputtering method to prepare the oxygen evolution electrode. The process is simple. During the preparation process, there is no need to introduce precursors and organic solvents, and there is no need for reaction processes such as mixing, dissolution, adsorption and reduction, which shortens the steps and time for preparing the oxygen evolution electrode. Compared with the spraying method, the magnetron sputtering method saves a large amount of solution-like raw materials and reducing agent materials, and also saves the energy consumption of calcination, drying and other processes, so it can significantly reduce production costs. In the process of preparing the oxygen evolution electrode by the magnetron sputtering method, no solvent-type chemical waste is generated, thereby avoiding pollution to the environment. Whether in terms of ease of preparation, economy or catalytic performance and service life, the oxygen evolution electrode prepared according to the method of the present invention has excellent performance, which can greatly improve the economic benefits of industrial water electrolysis.

[0085] While various embodiments of the present disclosure have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

[0086] The above are merely optional embodiments of the present disclosure and are not intended to limit the present disclosure. Those skilled in the art will readily appreciate that the present disclosure may be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, and the like made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure.

Claims

1. A method (100) for preparing an oxygen evolution electrode, comprising: Using magnetron sputtering, a thin film (102) is prepared on the surface of a conductive substrate, wherein the thin film at least contains a catalyst substance that serves as a catalyst in an oxygen evolution reaction and a soluble substance that can be dissolved in an alkaline solution; as well as The film is brought into contact with the alkaline solution (104) so ​​that the soluble substance dissolves in the alkaline solution, thereby forming a porous catalyst layer composed of the catalyst substance on the surface of the conductive substrate, and the conductive substrate and the porous catalyst layer form the oxygen evolution electrode.

2. The method (100) according to claim 1, wherein: The soluble substance includes at least one of aluminum, zinc, silicon, silicon oxide, aluminum oxide, and zinc oxide.

3. The method (100) according to claim 1 or 2, wherein: The catalyst material includes at least one of the following: iron-nickel oxide, iron oxide, and nickel oxide.

4. The method (100) according to claim 3, wherein: The iron-nickel oxide includes nickel ferrite.

5. The method (100) according to any one of claims 1, 2 and 4, wherein: The preparing the thin film comprises: in the magnetron sputtering, using a sputtering target to prepare the thin film on the conductive substrate, Wherein, the sputtering target material includes a first type of target material and a second type of target material; The first type of target material is configured to form a catalyst substance in the thin film during the magnetron sputtering; The second type of target is configured to form the soluble substance in the thin film during the magnetron sputtering.

6. The method (100) according to claim 5, wherein: The first type of target material includes a target material formed by at least one of the following substances: iron-nickel oxide, iron alone, iron oxide, nickel alone, and nickel oxide.

7. The method (100) according to claim 5, wherein: The second type of target material includes a target material formed of at least one of the following substances: zinc element, zinc oxide, silicon element, silicon oxide, aluminum element, and aluminum oxide.

8. The method (100) according to any one of claims 1, 2, 4 and 6-7, wherein: The conductive substrate is selected from at least one of nickel foam, nickel felt, nickel mesh, titanium felt and titanium foam.

9. The method (100) according to any one of claims 1, 2, 4 and 6-7, wherein: The pore size of the porous catalyst layer is in the range of 10 nm to 800 nm.

10. The method (100) according to any one of claims 1, 2, 4 and 6-7, wherein: The thickness of the porous catalyst layer is greater than 200 nm.

11. The method (100) according to any one of claims 1, 2, 4 and 6-7, wherein: The molar content of the soluble substance in the film is in the range of 5% to 45%.

12. An oxygen evolution electrode prepared by the method according to any one of claims 1 to 11.

13. An electrolytic cell (200) for electrolyzing an electrolyte (204) to produce oxygen and hydrogen, wherein the electrolytic cell (200) comprises: A cathode (201) for a hydrogen evolution reaction; an anode (202) for oxygen evolution reaction, the anode (202) being composed of the oxygen evolution electrode according to claim 12; and A conductive separator (203) separates the anode (202) and the cathode (201).

14. The electrolytic cell (200) according to claim 13, wherein: The electrolyte (204) includes an alkaline solution.

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