High-performance self-optimizing stainless steel oxygen evolution electrode and application

Abstract

The invention discloses a high-performance self-optimizing stainless steel oxygen evolution electrode and application. The electrode is obtained through acid etching, annealing and electrochemical oxidation treatment. The stainless steel is a self-optimized electrode, the performance of the stainless steel electrode is remarkably improved by improving the electrochemical active area and conductivity, optimizing the OER reaction mechanism and simplifying the production process, and a solid foundation is laid for actual industrial application.

Description

Technical Field

[0001] The invention relates to the field of new energy technology, and in particular to a high-performance self-optimizing stainless steel oxygen evolution electrode and application thereof. Background Art

[0002] With the rapid development of industry, excessive carbon emissions have aggravated global warming. In order to cope with the threat of climate change, it is crucial to find clean energy that can replace non-fossil energy. Among them, hydrogen energy is regarded as the most promising clean energy. Water electrolysis hydrogen production technology is a low-carbon and environmentally friendly way to produce green hydrogen, but it still faces difficult challenges in promotion and application. The main reason is that reducing the high operating costs caused by catalyst prices and low electrolysis efficiency has always been a major problem. Therefore, the development of low-cost, highly active and highly stable water-splitting electrocatalysts is the core of achieving efficient and sustainable production of hydrogen.

[0003] The oxygen evolution reaction (OER) under alkaline conditions is considered to be a key anode reaction in renewable energy systems. Although noble metal oxides such as RuO2 and IrO2 have been widely used for OER in alkaline media, they are too expensive for large-scale industrial applications. Nickel-iron (Ni-Fe)-based electrocatalysts have become an outstanding choice in the past decade and have become the catalyst of choice for OER in alkaline environments. Most of these NiFe catalyst layers are grown on nickel foam, stainless steel, and carbon cloth, but under industrial high current operation, the catalytic layer is easily separated or leached, resulting in poor stability. In addition, the catalysts prepared under laboratory conditions have the problems of low yield and cumbersome preparation process, which makes it difficult to achieve large-scale synthesis, thus restricting the widespread application of these catalysts in industrial production.

[0004] At present, alkaline electrolysis systems have been widely used, but due to the direct contact between the stainless steel bipolar plate and the anode catalyst, the material difference is prone to produce a potential difference, which makes the catalyst easy to corrode. Stainless steel has rich transition metal elements, such as Fe, Ni, Cr, Mo, etc., which can be used as a source of in-situ growth of OER catalysts and is a suitable candidate for OER electrodes. Secondly, its good conductivity makes it an ideal substrate for electrochemical processes such as OER. In addition, stainless steel is a ubiquitous and inexpensive material. Therefore, active and low-cost OER electrodes made of stainless steel may have great prospects. In the prior art, CN2024103820025 proposes a method for preparing a stainless steel-based anode oxygen evolution electrode for seawater electrolysis, by immersing the stainless steel substrate in an aqueous solution containing halogen oxygen acid salts and alkali metal hydroxides for hydrothermal corrosion, and the final electrode exhibits low overpotential, high catalytic activity, long-lasting stability and excellent corrosion resistance. CN2021108561930 discloses a method for preparing a stainless steel-based catalyst, by anodizing stainless steel in a solution containing NaCl to increase its catalytic activity and expose more active sites. The method is simple and easy to operate, and demonstrates excellent activity and good durability at high current density. CN2024103284865 provides a method for preparing a stainless steel-based oxygen evolution electrode, which uses an electrochemical etching method to corrode the stainless steel surface in an acid solution, and then uses a hydrothermal method to in-situ activate to form an alkaline electrolysis water oxygen evolution catalytic electrode. CN2024102728657 describes a method for preparing a high-performance self-optimizing stainless steel oxygen evolution electrode, which achieves electrode modification through anodic corrosion in a chloride solution combined with subsequent secondary electrolysis in an alkaline solution. CN2022116061739 introduces a method for modifying the surface of stainless steel, which combines hydrothermal corrosion and hydrothermal sulfidation processes to obtain a stainless steel surface with good catalytic activity.

[0005] However, the above methods generally have the problem of relying on complex hydrothermal synthesis steps. Not only do they have high requirements for equipment and operating conditions and are difficult to meet the needs of large-scale industrial production, but there is also insufficient research on the stability testing of electrodes under long-term industrial conditions, and a lack of sufficient verification of their long-term performance in actual application environments, which undoubtedly affects the actual promotion and application of electrodes. Summary of the invention

[0006] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a high-performance self-optimizing stainless steel oxygen evolution electrode and its application. The electrode is obtained by coupled corrosion, annealing and electrochemical activation treatment, which significantly simplifies the preparation process, and the modified stainless steel follows the OPM reaction mechanism when used as an OER anode, thereby greatly improving the catalytic activity and long-term stability of the electrode, and ultimately solving the problems in the prior art that stainless steel needs to be surface modified when used for water electrolysis catalysis, has a high overpotential, and is difficult to meet the needs of industrial alkaline water electrolysis.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A high-performance self-optimizing stainless steel oxygen evolution electrode is prepared by the following steps:

[0009] Step 1: Pre-treat the stainless steel surface to remove impurities on its surface;

[0010] Step 2: placing the stainless steel treated in step 1 in an acid solution, corroding it at 25-50° C. for 1-4 hours, and then cleaning and drying the stainless steel to obtain an acid-etched stainless steel electrode; wherein the concentration of the acid solution is 10-40wt%;

[0011] Step 3: annealing the stainless steel treated in step 2 in an air atmosphere to obtain an air-annealed stainless steel electrode; wherein the annealing temperature is 400-900° C. and the annealing holding time is 1-4 hours;

[0012] Step 4: placing the stainless steel electrode treated in step 3 in an alkaline solution, and electrolyzing the stainless steel as an anode to obtain the stainless steel oxygen evolution electrode; wherein the concentration of the alkali in the alkaline solution is 1-2 mol / L, and the current density during electrolysis is 400-600 mA / cm 2 , the electrolysis time is 100 to 1600 hours.

[0013] Preferably, calculated by weight percentage, the Cr content in the stainless steel is greater than 20%, and the Ni content is greater than 20%.

[0014] Preferably, the stainless steel comprises the following components calculated in weight percentage: 23-25% Cr, 21-23% Ni, 0.04-0.05% Si, 2-4% Mn, and the balance Fe.

[0015] Preferably, in step 1, the stainless steel is placed in a sample and ultrasonically cleaned in deionized water for 10 to 20 minutes.

[0016] Preferably, in step 2, the acid solution comprises one of HF, H2SO4 or HNO3.

[0017] Preferably, in step 3, the heating rate is 2°C / min.

[0018] Preferably, in step 4, the base is one of KOH and NaOH.

[0019] The present invention also provides an application of a high-performance self-optimizing stainless steel oxygen evolution electrode, wherein the high-performance self-optimizing stainless steel oxygen evolution electrode is used for electrolyzing water to evolve oxygen.

[0020] Preferably, the stainless steel oxygen evolution electrode acts as an anode to evolve oxygen during water electrolysis.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. In the present invention, stainless steel is used as a substrate. Through acid etching treatment, the specific surface area and porosity of the stainless steel electrode can be significantly increased. This surface modification not only helps to remove surface impurities, but also creates more active sites, thereby increasing the electrochemical active area (ECSA); subsequently, through air annealing treatment, highly crystalline oxides such as Fe2O3 can be generated on the stainless steel surface, further improving the electronic properties of the electrode and increasing the conductivity of the material; under the combined effect of these treatment steps, the stainless steel electrode exhibits more excellent catalytic performance when used as an anode for oxygen evolution during the electrolysis of water.

[0023] 2. The present invention further converts oxides into active OER substances such as hydroxy oxides through a series of treatment steps on stainless steel, and finally induces the OER reaction mechanism of the stainless steel electrode to be an OPM mechanism with higher catalytic activity and stronger stability; under the OPM mechanism, since there is no production of *OOH intermediates and no direct participation of lattice oxygen, this breaks the limitation of the AEM scaling relationship and reduces the overpotential in the OER process; at the same time, it avoids the problem of catalyst structure collapse caused by lattice oxygen precipitation, ensures the structural stability and durability of the electrode during long-term operation, and fundamentally improves the self-optimization performance of the stainless steel electrode during long-term operation.

[0024] 3. Compared with the complex hydrothermal synthesis method, the preparation process proposed in the present invention is simpler and easier to control, does not require complex equipment or harsh operating conditions, and has low energy consumption, which is very suitable for large-scale industrial production; the stainless steel substrate selected in the present invention has good electrical conductivity and mechanical strength, coupled with the optimized preparation process, so that the final electrode has both efficient catalytic performance and economic efficiency; this makes it possible to achieve efficient and low-cost hydrogen production by electrolysis of water in industry; in summary, the present invention achieves a significant improvement in the performance of stainless steel electrodes by improving the electrochemical active area and conductivity, optimizing the OER reaction mechanism and simplifying the production process, and lays a solid foundation for practical industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope photo of stainless steel without any treatment.

[0026] Figure 2 This is a scanning electron microscope photograph of the stainless steel oxygen evolution electrode obtained in Comparative Example 1 of the present invention.

[0027] Figure 3 This is a scanning electron microscope photograph of the stainless steel-based oxygen evolution electrode obtained in Comparative Example 2 of the present invention.

[0028] Figure 4 This is a scanning electron microscope photograph of the stainless steel-based oxygen evolution electrode obtained in Example 1 of the present invention.

[0029] Figure 5 These are the LSV curves of the stainless steel oxygen evolution electrodes obtained in Comparative Example 1, Comparative Example 2, Example 1, Example 15, Example 16, Example 17, and Example 18 of the present invention and the stainless steel without any treatment.

[0030] Figure 6 The stainless steel-based oxygen evolution electrode obtained in Example 18 of the present invention is 500 mA / cm 2 The stability test diagram below.

[0031] Figure 7 The electrochemical impedance spectra of the stainless steel oxygen evolution electrodes obtained in Comparative Example 1, Comparative Example 2, Example 1, Example 15, Example 16, Example 17, and Example 18 of the present invention and the stainless steel without any treatment are shown.

[0032] Figure 8 This is an electrochemical specific surface area diagram of the stainless steel oxygen evolution electrodes obtained in Comparative Example 1, Comparative Example 2, Example 1, Example 15, Example 16, Example 17, and Example 18 of the present invention and the stainless steel without any treatment.

[0033] Fig. 9Polarization curves of Example 1 with and without TMA+.

[0034] Fig.10 This is the Raman spectrum of Example 1 after OER reaction in TMAOH.

[0035] Fig.11 is the wavelength between 1000-1400 cm at various applied potentials. -1 Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurement diagram was carried out in the range.

[0036] Fig.12 For 50mV s -1 CV curves of SSEAE recorded with and without 0.1 M methanol at scan rate.

[0037] In the figure: SSE is comparative example 1; SSEA is comparative example 2; SSEAE / 800 is example 1; SS is a control sample; SSEAE / 100 is example 15, SSEAE / 200 is example 16, SSEAE / 400 is example 17, and SSEAE / 1600 is example 18. DETAILED DESCRIPTION

[0038] The present invention will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the present invention belong to the scope of protection of the present invention.

[0039] Unless otherwise indicated in specific cases in the present invention, the numerical ranges listed herein include the upper and lower limits, and all integers and fractions within the range, and are not limited to the specific values ​​listed when defining the range.

[0040] 1. A high-performance self-optimizing stainless steel oxygen evolution electrode

[0041] Step 1: Pre-treat the stainless steel surface to remove impurities on its surface;

[0042] Step 2: placing the stainless steel treated in step 1 in an acid solution, corroding it at 25-50° C. for 1-4 hours, and then cleaning and drying the stainless steel to obtain an acid-etched stainless steel electrode; wherein the concentration of the acid solution is 10-40wt%;

[0043] Step 3: annealing the stainless steel treated in step 2 in an air atmosphere to obtain an air-annealed stainless steel electrode; wherein the annealing temperature is 400-900° C., the holding time is 1-4 hours, and the heating rate is 2° C. / min;

[0044] Step 4: placing the stainless steel electrode treated in step 3 in an alkaline solution, and electrolyzing the stainless steel as an anode to obtain the stainless steel oxygen evolution electrode; wherein the concentration of the alkali in the alkaline solution is 1-2 mol / L, and the current density during electrolysis is 400-600 mA / cm 2 , the electrolysis time is 100 to 1600 hours.

[0045] The present invention takes into account that the prior art often relies on complex hydrothermal synthesis steps, which not only has high requirements for equipment and operating conditions, but also has high energy consumption in actual large-scale industrial production. At the same time, the electrolysis of water to produce hydrogen often requires long-term operation, which also puts higher requirements on the stability of the electrode. Based on the limitations of the prior art, the present invention considers improving the preparation method of the electrode, and the stainless steel is prepared after being subjected to coupled corrosion, air annealing and electrochemical oxidation process treatment. The specific surface area and porosity of the stainless steel electrode are greatly increased by acid etching, and then the stainless steel surface is formed by air annealing. Strongly crystalline Fe2O3 and other oxides are generated, and finally, by the electrochemical oxidation method, the oxides are further converted into active OER substances such as hydroxyl oxides, and finally the OER reaction mechanism of the stainless steel electrode is induced to become an OPM mechanism with higher catalytic activity and stronger stability. Because there is no generation of *OOH in the OPM mechanism process, and no lattice oxygen participates in the reaction, the AEM scaling relationship limitation can be broken through, so that the prepared electrode not only has a theoretically high intrinsic activity, but also can avoid the collapse of the catalyst structure due to the precipitation of lattice oxygen, ensuring that the electrode can maintain structural stability during the long-term electrolysis of water. After conducting an in-depth study on the surface of the stainless steel oxygen evolution electrode, the present invention found that the method of the present invention improves the electronic properties and surface structure of the stainless steel surface, increases its specific surface area and porosity, and also improves the electron conduction efficiency. These improvements give the stainless steel electrode better conductivity, enhanced electrochemical active area and electrocatalytic performance, so that it exhibits excellent comprehensive performance in the electrolysis of water to produce hydrogen.

[0046] In some embodiments of the present invention, when acid etching is performed in step 2, the temperature can be controlled by heating in a water bath, and the temperature is maintained at a temperature slightly higher than room temperature, that is, at 25 to 50°C, and the stainless steel sheet is immersed in a reaction vessel so that the acid solution submerges the stainless steel sheet. Under this condition, the stainless steel is corroded for 1 to 4 hours, and then the stainless steel is cleaned and dried to obtain an acid-etched stainless steel electrode. Among them, the selection of the concentration and type of the acid solution will have different effects on the performance of the final electrode. When the concentration of the acid solution is low, the corrosion rate is slow, and the purpose of effectively removing surface impurities or changing the surface structure may not be achieved; when the concentration of the acid solution is too high, it may cause excessive corrosion, damage the stability of the material matrix itself, and affect the stability and catalytic performance of the electrode during the long-term electrolysis of water to produce hydrogen. Therefore, the concentration of the acid solution is controlled between 10 and 40 wt%, preferably 20 wt%, for example, 10 wt%, 20 wt%, 30 wt%, 40 wt%, etc., and all ranges and sub-ranges between the above values; the acid solution includes one of hydrofluoric acid (HF), sulfuric acid (H2SO4) or nitric acid (HNO3). Different types of acids have different effects on stainless steel, and the selection of the appropriate acid type can be determined according to the desired final electrode characteristics. For the control of the corrosion time, it should be controlled between 1 and 4 hours. When the corrosion time is short, it may not be enough to fully achieve the expected surface modification effect; and too long corrosion time may cause unnecessary excessive corrosion, affecting the performance and stability of the electrode. Therefore, the corrosion time is further preferably 2 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, etc., and all ranges and sub-ranges between the above values. It should be understood that in the embodiment, any of the above ranges can be combined with any other ranges in other embodiments to optimize the preparation process of the stainless steel electrode to ensure that it has excellent electrochemical properties and stability.

[0047] In some embodiments of the present invention, in step 3, the stainless steel treated in step 2 is subjected to air annealing to generate oxides such as Fe2O3 with strong crystallinity on the surface of the stainless steel. The stainless steel treated in step 2 is placed in a horizontal furnace and annealed in an air atmosphere to obtain an air-annealed stainless steel electrode. The annealing temperature is controlled between 400 and 900°C. When the annealing temperature is low, it may not be enough to promote the full reorganization of the surface structure and the transformation of inactive substances; when the annealing temperature is too high, it may cause changes in the internal structure of the material or excessive oxidation of the surface, affecting the performance of the final electrode. Therefore, the annealing temperature may be further preferably 700°C, for example, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, etc., and all ranges and sub-ranges between the above values. The holding time of the annealing treatment is controlled between 1 and 4 hours, because a shorter holding time may not provide enough time for the necessary structural changes and chemical reactions to occur on the surface; while a too long holding time will lead to unnecessary energy waste and may cause adverse side reactions. Therefore, the holding time of the annealing treatment is further preferably 2 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, etc., and all ranges and sub-ranges between the above values.

[0048] In some embodiments of the present invention, in step 3, the heating rate during annealing is set to 2°C / min. This rate helps to ensure uniform heating of the sample, reduce the impact of thermal stress on the material structure, and avoid potential defects caused by too fast a temperature rise. By precisely controlling the annealing conditions, the reorganization of the surface structure of stainless steel can be effectively promoted, the oxygen vacancy concentration can be increased, and the transformation of the OER (oxygen evolution reaction) mechanism can be induced, thereby improving the catalytic activity and durability of the electrode. It should be understood that in the embodiments, any of the above ranges can be combined with any other ranges in other embodiments to optimize the preparation process of the stainless steel electrode to ensure that it has excellent electrochemical properties and stability.

[0049] In some embodiments of the present invention, electrochemical oxidation is performed in step 4 to further restructure the stainless steel surface after air annealing. This process can adopt a two-electrode system, with the stainless steel after air annealing as the anode, the graphite rod as the cathode, and the electrolyte as an alkaline solution. Among them, the concentration of the alkali in the alkaline solution is controlled between 1 and 2 mol / L. When the alkali concentration is low, the current transfer efficiency may be insufficient; when the alkali concentration is too high, the solution viscosity may increase and the conductivity may be reduced, both of which will adversely affect the oxygen evolution performance of the electrode. Therefore, the concentration of the alkali in the alkaline solution is further preferably 1 mol / L, for example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, etc., and all ranges and sub-ranges between the above values. The alkali is one of KOH and NaOH. The current density during this electrolysis process affects the effect of the stainless steel surface structural reorganization. When the current density is small, the oxidation rate is slow, and it is difficult to effectively promote the reconstruction of the electrode surface structure; and excessive current density may cause excessive corrosion of the electrode surface, thereby reducing the oxygen evolution performance of the electrode. Therefore, the current density during electrolysis is controlled at 400-600 mA / cm 2 Between, preferably 500mA / cm 2 , for example, 400 mA / cm 2 , 500mA / cm 2 、600mA / cm 2 Etc., and all ranges and sub-ranges between the above values. At the same time, the electrolysis time also needs to be controlled. The shorter electrolysis time is not enough to fully dissolve the inactive substances, the electrode surface oxides cannot be fully converted into hydroxides, the oxygen defect concentration cannot be effectively improved, and the OER reaction mechanism of the stainless steel electrode cannot be induced to change, which will reduce the oxygen evolution performance of the electrode. Excessive electrolysis time will lead to an unnecessary increase in the energy consumption of the entire preparation process, thereby increasing the preparation cost. Therefore, the electrolysis time is controlled between 100 and 1600 hours, preferably 800 hours, for example, 100 hours, 200 hours, 400 hours, 800 hours, 1600 hours, etc., and all ranges and sub-ranges between the above values. It should be understood that in the embodiment, any of the above ranges can be combined with any other ranges in other embodiments to optimize the preparation process of the stainless steel oxygen evolution electrode to ensure that it has excellent electrochemical properties and stability.

[0050] The present invention can effectively promote the reorganization of the surface structure of the stainless steel electrode, increase the oxygen vacancy concentration, induce the transformation of the OER (oxygen evolution reaction) mechanism, and thus enhance the catalytic activity and durability of the electrode by precisely controlling the alkaline solution concentration, current density and electrolysis time.

[0051] In some embodiments of the present invention, the Cr content in the stainless steel is greater than 20%, and the Ni content is greater than 20%, calculated by weight percentage. The present invention is applicable to almost all stainless steels with a mass fraction of Cr and Ni greater than 20%. When the Ni content in the stainless steel is low, the key OER active substance Ni cannot be formed on the electrode surface. x Fe 1-x OOH. When the Cr content in stainless steel is low, the inactive element Cr will not be dissolved in the second step of electrolysis, and the ratio of Ni and Fe will not change, which may not induce changes in the OER reaction mechanism of the stainless steel electrode. In an embodiment, the stainless steel includes the following components, calculated by weight percentage: 23-25% Cr, 21-23% Ni, 0.04-0.05% Si, 2-4% Mn, and the balance is Fe.

[0052] In some embodiments of the present invention, in step 1, the stainless steel sample is ultrasonically cleaned in deionized water to remove loose contaminants, dust and other tiny impurities on the surface to ensure the effectiveness of subsequent processing steps. The time control of ultrasonic cleaning is crucial to achieving a good cleaning effect: too short a time may not completely remove surface contaminants, affecting the quality of subsequent processing; while too long a time may lead to unnecessary energy waste and may cause slight damage to the sample surface. Therefore, the time of ultrasonic cleaning can be controlled to 10 minutes, 15 minutes, 20 minutes, etc., and all ranges and sub-ranges between the above values. It should be understood that in the embodiment, any of the above ranges can be combined with any other ranges in other embodiments to optimize the pretreatment process of the stainless steel sample to ensure that its surface cleanliness reaches the best state, thereby providing an ideal starting condition for subsequent anodic corrosion or other processing steps. In addition, in order to ensure the cleaning effect while avoiding any potential adverse effects on the stainless steel sample, it is recommended to use deionized water as the cleaning medium, because deionized water does not contain minerals and other impurities, which can reduce the risk of secondary contamination. By strictly controlling the time of ultrasonic cleaning and using appropriate cleaning media, the surface quality of the stainless steel sample and the effect of subsequent processing can be effectively improved.

[0053] 2. Application of a high-performance self-optimizing stainless steel oxygen evolution electrode

[0054] The high-performance self-optimizing stainless steel oxygen evolution electrode of the present invention can be used for electrolyzing water to evolve oxygen. In specific implementation, the stainless steel oxygen evolution electrode acts as an anode to evolve oxygen during the electrolysis of water.

[0055] 3. Examples and Comparative Examples

[0056] Example 1

[0057] Step 1: Pretreatment of stainless steel materials:

[0058] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0059] Step 2: Preparation of acid-etched stainless steel electrodes:

[0060] The stainless steel sample was placed in a 20% HF solution and corroded at 30° C. for 2 hours. The stainless steel was then cleaned and dried to obtain a stainless steel sample treated with HF corrosion.

[0061] Step 3: Preparation of air annealed stainless steel electrodes:

[0062] The stainless steel is placed in a horizontal furnace and annealed in an air atmosphere. The temperature is raised to 700°C at a heating rate of 2°C / min and a holding time of 2h to obtain a stainless steel electrode after air annealing.

[0063] Step 4: Preparation of electrochemical oxidation stainless steel electrode:

[0064] A two-electrode system was used, with an anodic corrosion stainless steel electrode as the anode, a graphite rod as the cathode, and a KOH solution as the electrolyte. The anodic corrosion stainless steel electrode was placed in a KOH solution for secondary electrolysis for 800 hours to obtain the final stainless steel oxygen evolution electrode. The current density during structural reconstruction was 500 mA / cm 2 The electrolyte concentration during structural reconstruction was 1 mol / L.

[0065] Example 2

[0066] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 2, the concentration of HF is 10%.

[0067] Example 3

[0068] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 2, the concentration of HF is 30%.

[0069] Example 4

[0070] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 2, the concentration of HF is 40%.

[0071] Example 5

[0072] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 2, the concentration of HNO3 is 20%.

[0073] Example 6

[0074] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 2, the concentration of H2SO4 is 20%.

[0075] Example 7

[0076] An improvement is made on the basis of Example 1, which differs therefrom in that: in step 2, the water bath heating time is 1 hour.

[0077] Example 8

[0078] An improvement is made on the basis of Example 1, which differs therefrom in that: in step 2, the water bath heating time is 3 hours.

[0079] Example 9

[0080] An improvement is made on the basis of Example 1, which differs therefrom in that: in step 2, the water bath heating time is 4 hours.

[0081] Example 10

[0082] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 3, the insulation temperature is 400°C.

[0083] Embodiment 11

[0084] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 3, the insulation temperature is 500°C.

[0085] Example 12

[0086] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 3, the insulation temperature is 600°C.

[0087] Embodiment 13

[0088] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 3, the insulation temperature is 800°C.

[0089] Embodiment 14

[0090] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 3, the insulation temperature is 900°C.

[0091] Embodiment 15

[0092] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 4, the electrolysis time is 100 hours.

[0093] Example 16

[0094] An improvement is made on the basis of Example 1, except that in step 4, the electrolysis time is 200 h.

[0095] Embodiment 17

[0096] An improvement is made on the basis of Example 1, and the difference therefrom is that in step 4, the electrolysis time is 400 h.

[0097] Embodiment 18

[0098] An improvement is made on the basis of Example 1, except that in step 4, the electrolysis time is 1600 h.

[0099] Comparative Example 1

[0100] Step 1: Pretreatment of stainless steel materials:

[0101] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0102] Step 2: Preparation of acid-etched stainless steel electrodes:

[0103] The stainless steel sample was placed in a 20% HF solution and corroded at 30° C. for 2 hours. The stainless steel was then cleaned and dried to obtain a stainless steel sample treated with HF corrosion.

[0104] Comparative Example 2

[0105] Step 1: Pretreatment of stainless steel materials:

[0106] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0107] Step 2: Preparation of acid-etched stainless steel electrodes:

[0108] The stainless steel sample was placed in a 20% HF solution and corroded at 30° C. for 2 hours. The stainless steel was then cleaned and dried to obtain a stainless steel sample treated with HF corrosion.

[0109] Step 3: Preparation of air annealed stainless steel electrodes:

[0110] The stainless steel is placed in a horizontal furnace and annealed in an air atmosphere. The temperature is raised to 700°C at a heating rate of 2°C / min and a holding time of 2h to obtain a stainless steel electrode after air annealing.

[0111] Comparative Example 3

[0112] Step 1: Pretreatment of stainless steel materials:

[0113] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0114] Step 2: Preparation of acid-etched stainless steel electrodes:

[0115] The stainless steel sample was placed in a 20% HF solution and corroded at 30° C. for 2 hours. The stainless steel was then cleaned and dried to obtain a stainless steel sample treated with HF corrosion.

[0116] Step 3: Preparation of electrochemical oxidation stainless steel electrode:

[0117] A two-electrode system was used, with an anodic corrosion stainless steel electrode as the anode, a graphite rod as the cathode, and a KOH solution as the electrolyte. The anodic corrosion stainless steel electrode was placed in a KOH solution for secondary electrolysis for 800 hours to obtain the final stainless steel oxygen evolution electrode. The current density during structural reconstruction was 500 mA / cm 2 The electrolyte concentration during structural reconstruction was 1 mol / L.

[0118] Comparative Example 4

[0119] Step 1: Pretreatment of stainless steel materials:

[0120] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0121] Step 2: Preparation of air annealed stainless steel electrodes:

[0122] The stainless steel is placed in a horizontal furnace and annealed in an air atmosphere. The temperature is raised to 700°C at a heating rate of 2°C / min and a holding time of 2h to obtain a stainless steel electrode after air annealing.

[0123] Step 3: Preparation of electrochemical oxidation stainless steel electrode:

[0124] A two-electrode system was used, with an anodic corrosion stainless steel electrode as the anode, a graphite rod as the cathode, and a KOH solution as the electrolyte. The anodic corrosion stainless steel electrode was placed in a KOH solution for secondary electrolysis for 800 hours to obtain the final stainless steel oxygen evolution electrode. The current density during structural reconstruction was 500 mA / cm 2 The electrolyte concentration during structural reconstruction was 1 mol / L.

[0125] Comparative Example 5

[0126] Step 1: Pretreatment of stainless steel materials:

[0127] Take 654S stainless steel and cut it into rectangles. The untreated 654S stainless steel is marked as SS. Then the stainless steel sample is ultrasonically cleaned in deionized water for 10 minutes to remove impurities on the surface of the stainless steel. Rinse slowly with deionized water for 3 minutes and dry for 6 hours to obtain a rectangular stainless steel sheet.

[0128] Step 2: Preparation of stainless steel electrode for electrochemical oxidation:

[0129] A two-electrode system was used, with an anodic corrosion stainless steel electrode as the anode, a graphite rod as the cathode, and a KOH solution as the electrolyte. The anodic corrosion stainless steel electrode was placed in a KOH solution for secondary electrolysis for 800 hours to obtain the final stainless steel oxygen evolution electrode. The current density during structural reconstruction was 500 mA / cm 2 The electrolyte concentration during structural reconstruction was 1 mol / L.

[0130] 4. Performance Analysis

[0131] 1. Microscopic morphology

[0132] The examples and comparative examples as well as the stainless steel (control sample) not subjected to any treatment were placed on a JSM-7800F scanning electron microscope produced by JEOL Ltd. (JEOL) for microscopic morphology observation.

[0133] Depend on Figure 1 It can be seen that the initial stainless steel surface is relatively flat and smooth. Figure 2 It can be seen that the stainless steel obtained in Comparative Example 1 is corroded into a porous structure, which is greatly beneficial to increase the active specific surface area. Figure 3 It can be seen that many dense grains grow on the porous structure surface of the stainless steel obtained in Comparative Example 2, and these fine grains are in a hexagonal shape. Figure 4It can be seen that the stainless steel surface agglomerates obtained in Example 1 are further decomposed, and their surface is loose and porous, sponge-like, and the active specific surface area is greatly increased. This phenomenon shows that long-term electro-oxidation not only changes the composition of the substance, but also affects its microstructure. It may be due to the continuous oxidation reaction that the original structure is destroyed and reorganized into new amorphous or low-crystallinity hydroxyl compounds.

[0134] 2. Determination of overpotential

[0135] The embodiments and comparative examples, as well as stainless steel (control sample) without any treatment, were placed on a CHI1140C electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. to measure the LSV curve. The oxygen evolution performance test was carried out using a three-electrode system, with a stainless steel electrode as the anode, a graphite rod as the cathode, Hg / HgO as the reference electrode, and a 1 mol / L KOH solution as the electrolyte. This method is different from the second step electrolysis.

[0136] Table 1 Overpotential measurement results of different stainless steel-based electrodes

[0137]

[0138] Depend on Figure 5 , Figure 6 From Table 1 we can see that:

[0139] (1) The overpotentials of all embodiments of the present invention have been greatly reduced, which are significantly lower than those of the comparative examples and the control sample. Even under conditions of higher current density, the overpotentials of the electrodes prepared in the embodiments of the present invention are still relatively low, indicating that after acid etching, annealing and electrochemical oxidation treatment, the overpotential of the stainless steel electrode can be significantly reduced, thereby improving its efficiency as an oxygen evolution reaction (OER) catalyst.

[0140] (2) In Comparative Example 1, only the stainless steel was subjected to acid etching, in Comparative Example 2, acid etching + annealing was used, in Comparative Example 3, acid etching + electrochemical oxidation was used, in Comparative Example 4, annealing + electrochemical oxidation was used, and in Comparative Example 5, only electrochemical oxidation was used. Compared with the control sample, the comparative examples were able to reduce the overpotential of the stainless steel electrode to a certain extent, but the reduction effect was still significantly lower than that of Example 1.

[0141] (3) The control example is the initial stainless steel, and its overpotential (η) can reach a current density (j) of 10 mA cm at 368 mV. -2 In Comparative Example 1, only the stainless steel was treated with acid, and the overpotential (η) was 345 mV to reach a current density (j) of 10 mA·cm -2 Comparative Example 2 uses acid etching + annealing treatment, and its overpotential (η) can reach a current density (j) of 10 mA·cm at 341 mV. -2Example 15 uses corrosion + annealing + electrochemical oxidation for 100 hours, and its overpotential (η) can reach a current density (j) of 10 mA·cm at 300 mV. -2 Example 16 uses corrosion + annealing + electrochemical oxidation for 200 hours, and its overpotential (η) can reach a current density (j) of 10 mA·cm at 288 mV. -2 Example 17 uses corrosion + annealing + electrochemical oxidation for 400 hours, and its overpotential (η) can reach a current density (j) of 10 mA·cm at 277 mV. -2 Example 1 uses corrosion + annealing + electrochemical oxidation for 800 hours, and its overpotential (η) can reach a current density (j) of 10 mA·cm at 188 mV. -2 Example 18 uses corrosion + annealing + electrochemical oxidation for 1600h, and its overpotential (η) can reach a current density (j) of 10mA·cm at 198mV. -2 At the same time, the electrode materials prepared by the same process as above all show a trend of gradually improving performance at different current densities, which indicates that the electrode materials of the present invention have self-optimizing properties.

[0142] (4) In general, the behavior of the electrode material prepared in Example 18 in the 1600-hour stability test showed two trends: in the first 800 hours, the performance of the electrode material was in a very gentle rising stage, and its performance was slowly and continuously improving steadily; then after entering the last 800 hours, the performance of the electrode material entered a stable period, and this stable period lasted for 800 hours; this indicates that the electrode material of the present invention has excellent stability when the oxygen evolution reaction (OER) is carried out for a long time.

[0143] 3. Electrochemical impedance spectroscopy

[0144] The examples and comparative examples, as well as stainless steel without any treatment (control sample), were placed on a CHI1140C electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. to measure electrochemical impedance spectroscopy (EIS).

[0145] Table 2 Electrochemical impedance spectroscopy results of different stainless steel-based electrodes

[0146]

[0147]

[0148] Depend on Figure 7 From Table 2 we can see that:

[0149] (1) The Nyquist plots obtained from the electrochemical impedance spectroscopy test of the stainless steel oxygen evolution electrodes prepared in the examples of the present invention and the comparative examples and the stainless steel without any treatment all show an approximate semicircle. Since the smaller the radius of the semicircle of the Nyquist plot (i.e., the impedance plot), the lower the impedance of the material; therefore, the impedance of the stainless steel oxygen evolution electrodes prepared in the examples is smaller than that of the comparative examples and the control sample, while the impedance of the comparative examples is generally higher, which indicates that the stainless steel electrode of the present invention has a lower impedance, i.e., a better conductivity.

[0150] (2) Comparative Examples 3 to 5 use a combination of two methods. Although the impedance can be reduced to a certain extent, the effect is still lower than the impedance of the three process couplings, that is, the impedance of Example 1, and the impedance gap with the embodiment is large.

[0151] (3) The control example is the initial stainless steel, and the Rct value is 8.223. Comparative Example 1 only acid-etched the stainless steel, and the Rct value was 7.45. Comparative Example 2 used acid etching + annealing treatment, and the Rct value was 7.334. Example 15 used corrosion + annealing treatment + electrochemical oxidation for 100 hours, and the Rct value was 2.232. Example 16 used corrosion + annealing treatment + electrochemical oxidation for 200 hours, and the Rct value was 1.977. Example 17 used corrosion + annealing treatment + electrochemical oxidation for 400 hours, and the Rct value was 1.491. Example 1 used corrosion + annealing treatment + electrochemical oxidation for 800 hours, and the Rct value was 0.861. Example 18 used corrosion + annealing treatment + electrochemical oxidation for 1600 hours, and the Rct value was 0.936. As the process progresses, the stainless steel has continuously improved charge transfer kinetics, which can be attributed to the excellent conductivity of stainless steel and the in-situ development of its surface active materials.

[0152] 4. Determination of electrochemical specific surface area

[0153] The examples and comparative examples, as well as stainless steel (control sample) without any treatment, were placed on a CHI1140C electrochemical workstation produced by Shanghai Chenhua Instrument Co., Ltd. to measure cyclic voltammetry curves (CV curves). The electrochemical specific surface area (C dl ).

[0154] Table 3 Electrochemical specific surface area determination results of different stainless steel-based electrodes

[0155]

[0156]

[0157] Depend on Figure 8As can be seen from Table 3, the electrochemical specific surface area (C dl ). Comparative Examples 1, 2 and 6 only performed one step of the method of the present invention, and such treatment had a very limited effect on the improvement of the electrochemical specific surface area. Comparative Examples 3, 4 and 5 used a combination of two methods, and it was found that the effect was still poor. However, the embodiment of the present invention greatly improved the electrochemical specific surface area of ​​the electrode by coupling acid etching, air annealing and electrochemical oxidation treatment, and the electrochemical specific surface area was increased to 30.9 mF·cm -2 .

[0158] The control example is the original stainless steel, and its double layer capacitance value is 1.8mF cm -2 In Comparative Example 1, only the stainless steel was treated with acid, and the double layer capacitance value was 3.3 mF cm -2 Comparative Example 2 uses acid etching + annealing treatment, and its double layer capacitance value is 3.5mF cm -2 Example 15 uses corrosion + annealing + electrochemical oxidation for 100 hours, and its double layer capacitance value is 13.9mF cm -2 Example 16 uses corrosion + annealing + electrochemical oxidation for 200 hours, and its double layer capacitance value is 15.7mF cm -2 Example 17 uses corrosion + annealing + electrochemical oxidation for 400 hours, and its double layer capacitance value is 20.6mF cm -2 Example 1 uses corrosion + annealing + electrochemical oxidation for 800 hours, and its double layer capacitance value is 30.9mFcm -2 Example 18 used corrosion + annealing + electrochemical oxidation for 1600 hours, and its double layer capacitance value was 28.4mF cm -2 The process of corrosion, annealing and electrochemical oxidation contributes to the increase of the overall active sites of the catalyst, and after the electro-oxidation treatment time reaches 800h, the effect brought by this contribution gradually stabilizes.

[0159] 5. Evolution of catalytic mechanisms

[0160] In the control experiments (with or without TMA+), no changes in the polarization curves were detected, which proves that there is no O in the catalytic process. 2- The Raman spectrum of 1 m TMAOH solution after OER conditions for 800 h shows a weak vibration peak of TMA+, which may be the intermediate between TMA+ ions and O 2-The weak binding force of the intermediates or the residual TMAOH solution left after the OER reaction. Through the analysis of attenuated total reflection (ATR-SEIRAS) and the reaction experiment of the reaction intermediates with methanol, these experimental results show that the OER reaction mechanism of the stainless steel oxygen evolution electrode is the oxide pathway mechanism (OPM).

[0161] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A high-performance self-optimizing stainless steel oxygen evolution electrode, characterized in that: The electrode is prepared by the following steps: Step 1: Pre-treat the stainless steel surface to remove impurities on its surface; Step 2: placing the stainless steel treated in step 1 in an acid solution, corroding it at 25-50° C. for 1-4 hours, and then cleaning and drying the stainless steel to obtain an acid-etched stainless steel electrode; wherein the concentration of the acid solution is 10-40wt%; Step 3: annealing the stainless steel treated in step 2 in an air atmosphere to obtain an air-annealed stainless steel electrode; wherein the annealing temperature is 400-900° C. and the annealing holding time is 1-4 hours; Step 4: placing the stainless steel electrode treated in step 3 in an alkaline solution, and electrolyzing the stainless steel as an anode to obtain the stainless steel oxygen evolution electrode; wherein the concentration of the alkali in the alkaline solution is 1-2 mol / L, and the current density during electrolysis is 400-600 mA / cm 2 , the electrolysis time is 100 to 1600 hours.

2. According to claim 1, the high-performance self-optimizing stainless steel oxygen evolution electrode is characterized in that: Calculated by weight percentage, The Cr content in the stainless steel is greater than 20%, and the Ni content is greater than 20%.

3. The high-performance self-optimizing stainless steel oxygen evolution electrode according to claim 2, characterized in that: Calculated by weight percentage, the stainless steel includes the following components: 23-25% Cr, 21-23% Ni, 0.04-0.05% Si, 2-4% Mn, and the balance is Fe.

4. The high performance self-optimizing stainless steel oxygen evolution electrode according to claim 1, characterized in that: In step 1, the stainless steel is ultrasonically cleaned in deionized water for 10 to 20 minutes.

5. The high performance self-optimizing stainless steel oxygen evolution electrode according to claim 1, characterized in that: In step 2, the acid solution includes one of HF, H2SO4 or HNO3.

6. The high performance self-optimizing stainless steel oxygen evolution electrode according to claim 1, characterized in that: In step 3, the heating rate is 2°C / min.

7. The high performance self-optimizing stainless steel oxygen evolution electrode according to claim 1, characterized in that: In step 4, the base is one of KOH and NaOH.

8. Application of a high-performance self-optimizing stainless steel oxygen evolution electrode, characterized in that: The high-performance self-optimizing stainless steel oxygen evolution electrode described in any of claims 1 to 7 is used for electrolyzing water to evolve oxygen.

9. The use of the high-performance self-optimizing stainless steel oxygen evolution electrode according to claim 8, characterized in that: The stainless steel oxygen evolution electrode acts as an anode to evolve oxygen during the water electrolysis process.

Images