Self-reconfigurable oxygen evolution electrode, preparation method and application

Abstract

The application discloses a self-reconfigurable oxygen evolution electrode, a preparation method and application, and relates to the technical field of electrochemistry. The preparation method comprises the following steps: taking a nickel substrate as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode, and placing the electrodes in a NiCo2O4 precursor solution; performing constant potential electrodeposition on the nickel substrate to obtain a precursor electrode with a Ni-Co LDH precursor on the surface; placing the precursor electrode into a heating device for heating and heat preservation, then taking out the precursor electrode for cooling to obtain a NiCo2O4 electrode with a spinel structure; and placing the NiCo2O4 electrode into an iron nitrate nonahydrate aqueous solution and a sodium hydroxide solution in sequence, and loading alpha-Fe2O3 nanoparticles on the surface of the NiCo2O4 electrode by using a continuous ion layer adsorption reaction method to obtain the self-reconfigurable oxygen evolution electrode. The preparation method of the self-reconfigurable oxygen evolution electrode constructs a composite catalytic layer composed of the spinel structure NiCo2O4 and alpha-Fe2O3 on the nickel substrate, and can adapt to power fluctuation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrolytic hydrogen production, and particularly relates to a self-reconfigurable oxygen evolution electrode, a preparation method and application. BACKGROUND

[0002] In the face of rapid consumption of traditional fossil energy and environmental pollution problems, hydrogen production using renewable energy is an important measure to achieve large-scale carbon emission reduction and plays a huge role in chemical industry, transportation, energy storage and the like. Key factors affecting the cost of hydrogen production using renewable energy are, on the one hand, the cost of electrolytic cell equipment. On the other hand, the cost of electricity. At present, the alkaline water electrolysis technology requires to work under stable or nearly stable power. Renewable energy such as wind power and photovoltaic power has natural fluctuation characteristics, which leads to unstable operation of the electrolytic cell and cannot realize effective use of energy. For example, when the input power fluctuates, the temperature, potential and the like in the electrolytic cell change instantaneously, and the mass transfer response of water and alkali solution is slow, resulting in local high temperature or high voltage in the electrolytic cell, which seriously damages the core components such as the diaphragm and the electrode, affects the service life of the electrolytic cell and greatly increases the use cost. The electrode is the main place for water electrolysis to occur and is the key to catalyze water decomposition. It is crucial to ensure stable and efficient operation of the electrode under fluctuating current density, while the traditional electrode is difficult to maintain stable and efficient electrolysis effect under low load and high load.

[0003] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art with regard to the application. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a self-reconfigurable oxygen evolution electrode, which constructs a composite catalytic layer composed of spinel structure NiCo2O4 and α-Fe2O3 on a nickel substrate, and can adapt to power fluctuation.

[0005] In order to achieve the above-mentioned purpose, a specific embodiment of the present application provides a preparation method of a self-reconfigurable oxygen evolution electrode, which comprises: placing a nickel substrate as a working electrode, a platinum sheet as a counter electrode and a saturated mercury-mercury electrode as a reference electrode in a NiCo2O4 precursor solution, performing constant potential electrodeposition on the nickel substrate to obtain a precursor electrode with a Ni-Co LDH precursor on the surface; heating and heat preserving the precursor electrode in a heating device, and then taking out the precursor electrode for cooling to obtain a NiCo2O4 electrode with spinel structure; loading α-Fe2O3 nanoparticles on the surface of the NiCo2O4 electrode using a continuous ion layer adsorption reaction method by sequentially placing the NiCo2O4 electrode in a ferric nitrate nonahydrate aqueous solution and a sodium hydroxide solution to obtain a self-reconfigurable oxygen evolution electrode.

[0006] In one or more embodiments of the present application, the deposition potential of the potentiostatic electrodeposition is -0.5 ~ -2.0 V relative to the saturated calomel electrode; the deposition temperature is 25 ~ 30°C; and the deposition time is 5 ~ 30 min.

[0007] In one or more embodiments of the present application, heating and holding the precursor electrode in a heating device and then taking out the precursor electrode for cooling comprises: heating the precursor electrode in the heating device to 250 ~ 500°C at a heating rate of 2 ~ 4°C / min and holding for 2 ~ 3 h, and then naturally cooling to 20 ~ 30°C.

[0008] In one or more embodiments of the present application, loading α-Fe2O3 nanoparticles on the surface of the NiCo2O4 electrode using the continuous ion layer adsorption reaction method comprises: immersing the NiCo2O4 electrode in an aqueous iron nitrate nonahydrate solution for 5 ~ 30 s so that Fe 3+ is adsorbed onto the surface of the NiCo2O4 electrode, taking it out and immersing it in deionized water for 25 ~ 35 s; immersing the washed NiCo2O4 electrode in a sodium hydroxide solution for 20 ~ 60 s so that OH - reacts with Fe 3+ on the surface of the NiCo2O4 electrode to generate Fe(OH)3 precipitate, taking it out and immersing it in deionized water for 25 ~ 35 s; repeating the above two steps multiple times, and then drying the washed NiCo2O4 electrode at 55 ~ 65°C; and heat treating the dried NiCo2O4 electrode in air at 200 ~ 400°C for 0.5 ~ 2 h to convert amorphous Fe(OH)3 into α-Fe2O3 and load it on the surface of the NiCo2O4 electrode.

[0009] In one or more embodiments of the present application, the concentration of the aqueous iron nitrate nonahydrate solution is 0.02 ~ 0.04 M; and / or, the concentration of the sodium hydroxide solution is 0.08 ~ 0.16 M.

[0010] In one or more embodiments of the present application, the preparation of the precursor solution comprises: dissolving nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and sodium nitrate in deionized water, magnetically stirring for 25 ~ 35 min until completely clear and transparent, and adjusting the pH to 6 ~ 6.5 to obtain the NiCo2O4 precursor solution.

[0011] In one or more embodiments of the present application, the concentration of the nickel nitrate hexahydrate is 0.05 ~ 0.1 M; and / or; the concentration of the cobalt nitrate hexahydrate is 0.1 ~ 0.2 M; and / or; the concentration of the sodium nitrate is 0.1 ~ 0.2 M.

[0012] In one or more embodiments of the present application, the preparation method of the self-reconfigurable oxygen evolution electrode further comprises pretreating the nickel substrate; the pretreatment comprises: sequentially ultrasonic cleaning the nickel substrate in acetone, anhydrous ethanol and deionized water for 10-20 min; soaking the cleaned nickel substrate in dilute hydrochloric acid for 5-10 min; taking out the nickel substrate from the dilute hydrochloric acid and rinsing with deionized water, and then drying in a vacuum drying oven at 55-65°C for 2-3 h.

[0013] Another specific embodiment of the present application provides a self-reconfigurable oxygen evolution electrode prepared by the preparation method of any one of the preceding embodiments.

[0014] Still another specific embodiment of the present application provides the use of the self-reconfigurable oxygen evolution electrode as described above in the field of hydrogen production by alkaline electrolysis of water with fluctuating power supply.

[0015] Compared with the prior art, the preparation method of the self-reconfigurable oxygen evolution electrode of the present application uses the two-step method of potentiostatic electrodeposition and successive ion layer adsorption reaction to construct a composite catalytic layer composed of spinel-structured NiCo2O4 and α-Fe2O3 on a nickel substrate. The nickel substrate provides a conductive framework and a large specific surface area, the NiCo2O4 layer is a highly efficient OER catalyst at low to moderate current density of fluctuating power supply, and the highly dispersed α-Fe2O3 nanoparticles serve as a "backup" catalyst precursor. When the input power of the fluctuating power supply increases dramatically and the current density rises to a certain critical value, the electrode potential also rises, and in the high potential and strong alkaline environment, the originally weakly active α-Fe2O3 will undergo irreversible electrochemical reconfiguration and transform into highly active γ-FeOOH (or iron-doped Ni / CoOOH). This process occurs in situ, thereby realizing the "self-upgrading" catalytic ability of the electrode under high power fluctuation, so that the electrode always maintains high efficiency. Therefore, the self-reconfigurable oxygen evolution electrode is mainly provided with activity by NiCo2O4 at low current density (such as when wind and solar power is weak), and when the current density rises sharply, the α-Fe2O3 will be in situ converted into highly active γ-FeOOH at high potential, realizing "self-reconfiguration" to adapt to power fluctuations, solving the problem of high efficiency of oxygen evolution at a wide current density, and the self-reconfiguration process is fast and can keep up with the rapid changes of fluctuating power supply, avoiding the rapid deactivation of a single material under non-design conditions. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any inventive labor.

[0017] Figure 1 This is a flowchart of a method for preparing a self-reconfigurable oxygen evolution electrode according to an embodiment of the present invention;

[0018] Figure 2 The diagram shows the initial state and LSV curve of the self-reconfigurable oxygen evolution electrode after reconfiguration and activation in Embodiment 1 of the present invention.

[0019] Figure 3 This is a stability curve of a self-reconfigurable oxygen evolution electrode in one embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions in the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0021] like Figure 1 As shown, a method for preparing a self-reconfigurable oxygen evolution electrode in one embodiment of the present invention includes steps S1-S3.

[0022] Step S1: Place a nickel substrate as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode in a NiCo2O4 precursor solution, and perform constant potential electrodeposition on the nickel substrate to obtain a precursor electrode with a Ni-Co LDH (Ni-Co layered double hydroxide) precursor on its surface.

[0023] Specifically, in step S1, nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and sodium nitrate are first dissolved in deionized water, and the solution is magnetically stirred for 25-35 minutes until completely clear and transparent, and the pH is adjusted to 6-6.5 to obtain a NiCo2O4 precursor solution. Preferably, the concentration of nickel nitrate hexahydrate is 0.05-0.1 M (mol / L), the concentration of cobalt nitrate hexahydrate is 0.1-0.2 M, and the concentration of sodium nitrate is 0.1-0.2 M.

[0024] Then, the pretreated nickel substrate is used as a working electrode, a platinum sheet is used as a counter electrode, and a saturated calomel electrode is used as a reference electrode in a three-electrode system to be placed in the prepared NiCo2O4 precursor solution for constant potential electrodeposition on the nickel substrate. Preferably, the deposition potential for the constant potential electrodeposition is -0.5 ~ -2.0 V (vs. SCE), wherein vs. SCE refers to the deposition voltage relative to the saturated calomel electrode; the deposition temperature is 25 ~ 30 °C; and the deposition time is 5 ~ 30 min. In addition, a magnetic stirrer can be added to the precursor solution during the constant potential electrodeposition, and the speed of the magnetic stirrer is controlled at 180 ~ 220 rpm to stir the precursor solution, so as to ensure that the NiCo2O4 precursor is uniformly plated on the surface of the nickel substrate.

[0025] After the constant potential electrodeposition of the nickel substrate is completed, the nickel substrate is taken out, repeatedly washed with deionized water to remove the loose particles attached to the surface of the nickel substrate, and then the nickel substrate is dried at 55 ~ 65 °C for 1 ~ 2 h to obtain a precursor electrode with a surface having a Ni-Co LDH precursor.

[0026] In an embodiment, the nickel substrate can be selected from pure nickel materials such as nickel mesh, nickel foam, and nickel felt. Preferably, the nickel substrate is nickel foam. Since the surface of the nickel substrate may be contaminated with dirt, oil, and an oxide layer during storage, the nickel substrate can also be pretreated before use. Specifically, the pretreatment of the nickel substrate includes: first cutting the nickel substrate with an area density of ≥320 g / m² into a size of (2-3) cm * (4-5) cm, and then ultrasonic cleaning the nickel substrate in acetone, anhydrous ethanol, and deionized water in sequence for 10-20 min to remove oil and contaminants on the surface of the nickel substrate. Then, the ultrasonic cleaned nickel substrate is immersed in 2 ~ 4 M dilute hydrochloric acid for 5 ~ 10 min to remove the oxide layer on the surface of the nickel substrate and make it hydrophilic, so as to facilitate the subsequent attachment of the precursor layer. Then, the nickel substrate is taken out of the dilute hydrochloric acid and washed with deionized water, and then dried in a vacuum drying oven at 55 ~ 65 °C for 2 ~ 3 h to obtain a pretreated nickel substrate.

[0027] Step S2: placing the precursor electrode into a heating device for heating and heat preservation, and then taking out the precursor electrode for cooling to obtain a NiCo2O4 electrode with a spinel structure.

[0028] Specifically, in step S2, the dried precursor electrode is placed into a heating device, such as a muffle furnace or a tube furnace, and heated to 250 ~ 500 °C at a heating rate of 2 ~ 4 °C / min and heat preserved for 2 ~ 3 h, and then naturally cooled to 20 ~ 30 °C, so that the precursor electrode with a surface having a Ni-Co LDH precursor is converted into a NiCo2O4 electrode with high catalytic activity.

[0029] Step S3: The NiCo2O4 electrode is sequentially immersed in a ferric nitrate nine hydrate aqueous solution and a sodium hydroxide solution, and α-Fe2O3 nanoparticles are loaded on the surface of the NiCo2O4 electrode by using a continuous ion layer adsorption reaction method to obtain a self-reconfigurable oxygen evolution electrode for fluctuating power supply.

[0030] Specifically, in step S3, the NiCo2O4 electrode is immersed in a ferric nitrate nine hydrate aqueous solution for 5-30 s to make Fe 3+ adsorbed onto the surface of the NiCo2O4 electrode, and then the NiCo2O4 electrode is taken out and immersed in deionized water for 25-35 s to remove excess ions physically adsorbed on the surface of the NiCo2O4 electrode. Preferably, the concentration of the ferric nitrate nine hydrate aqueous solution is 0.02-0.04 M.

[0031] Then, the immersed NiCo2O4 electrode is immersed in a sodium hydroxide solution for 20-60 s to make OH - react with Fe 3+ on the surface of the NiCo2O4 electrode to generate Fe(OH)3 precipitate, and then the NiCo2O4 electrode is taken out and immersed in ionized water for 25-35 s to remove byproducts and loose particles. Preferably, the concentration of the sodium hydroxide solution is 0.08-0.16 M.

[0032] The above two steps are repeated multiple times to ensure that a thin layer of α-Fe2O3 nanoparticles with high purity and high bonding strength is obtained on the surface of the NiCo2O4 electrode. Preferably, the above two steps are repeated 10-20 times. Then, the immersed NiCo2O4 electrode is dried at 55-65°C.

[0033] The dried NiCo2O4 electrode is heat-treated in air at 200-400°C for 0.5-2 hours to convert amorphous Fe(OH)3 into α-Fe2O3 and load the α-Fe2O3 on the surface of the NiCo2O4 electrode, thereby obtaining a self-reconfigurable oxygen evolution electrode with NiCo2O4 and α-Fe2O3 loaded on the surface.

[0034] The preparation method of the self-reconfigurable oxygen evolution electrode uses a two-step method of potentiostatic electrodeposition and continuous ion layer adsorption reaction to construct a composite catalytic layer composed of spinel-structured NiCo2O4 and α-Fe2O3 on a nickel substrate. At a low to moderate current density, the spinel-structured NiCo2O4 on the surface of the self-reconfigurable oxygen evolution electrode provides activity; at a high potential and strong alkaline environment, the α-Fe2O3 will be converted into super-highly active γ-FeOOH (or iron-doped Ni / CoOOH), realizing the "self-reconfiguration" of the oxygen evolution electrode to adapt to the power fluctuation of the fluctuating power supply.

[0035] The application will be further described below in conjunction with specific examples and comparative examples.

[0036] Example 1

[0037] Step S1: Foam nickel with an area density of 400 g / m2was selected as the nickel substrate and cut into a size of 2 cm*4 cm. Then, the nickel substrate was sequentially ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 min, and then the ultrasonically cleaned nickel substrate was immersed in 3M dilute hydrochloric acid for 5 min. Then, the nickel substrate was taken out of the dilute hydrochloric acid and rinsed with deionized water, and then dried in a 60°C vacuum drying oven for 2 h to obtain a pretreated nickel substrate. 0.05 M nickel nitrate hexahydrate, 0.1 M cobalt nitrate hexahydrate, and 0.1 M sodium nitrate were dissolved in deionized water, magnetically stirred for 30 min until completely clear and transparent, and the pH was adjusted to 6.5 to obtain a NiCo2O4 precursor solution. The pretreated nickel substrate was placed as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode in the prepared NiCo2O4 precursor solution, and constant potential electrodeposition was performed on the nickel substrate. The deposition potential was -1 V (vs. SCE), the deposition temperature was 25°C, and the deposition time was 20 min. The speed of the magnetic stirrer was 200 rpm. After the constant potential electrodeposition of the nickel substrate was completed, the nickel substrate was taken out, repeatedly rinsed with deionized water, and then dried at 60°C for 1 h to obtain a precursor electrode with a Ni-Co LDH precursor on the surface.

[0038] Step S2: The dried precursor electrode was placed in a muffle furnace and heated to 300°C at a heating rate of 2°C / min and kept for 2 h, and then naturally cooled to 25°C.

[0039] Step S3: The NiCo2O4 electrode was immersed in a 0.02M aqueous ferric nitrate solution for 20 s, and then the NiCo2O4 electrode was taken out and immersed in deionized water for 30 s. Then, the immersed NiCo2O4 electrode was immersed in a 0.08M sodium hydroxide solution for 30 s, and then taken out and immersed in ionized water for 30 s.

[0040] The above two steps were repeated 10 times. Then, the immersed NiCo2O4 electrode was dried at 60°C.

[0041] The dried NiCo2O4 electrode was heat-treated in air at 300°C for 1 hour to obtain a self-restructured oxygen evolution electrode.

[0042] Example 2

[0043] The difference from Example 1 is that the electrodeposition potential is -2 V (vs. SCE).

[0044] Example 3

[0045] The difference from Example 1 is that the time of electrodeposition is 30 min.

[0046] Example 4

[0047] The difference from Example 1 is that in step S2, heating to 500°C is at a heating rate of 2°C / min.

[0048] Example 5

[0049] The difference from Example 1 is that in step S3, the NiCo2O4 electrode is immersed in 0.02M aqueous ferric nitrate nonahydrate solution for 30s, and the NiCo2O4 electrode is immersed in 0.08M sodium hydroxide solution for 60s, and the two steps are repeated 5 times.

[0050] Example 6

[0051] The difference from Example 1 is that in step S3, the NiCo2O4 electrode is immersed in 0.02M aqueous ferric nitrate nonahydrate solution for 30s, and the NiCo2O4 electrode is immersed in 0.08M sodium hydroxide solution for 60s, and the two steps are repeated 20 times.

[0052] Example 7

[0053] The difference from Example 1 is that in step S3, the dried NiCo2O4 electrode is heat treated in air at 400°C for 0.5 hour.

[0054] Example 8

[0055] The difference from Example 1 is that in step S3, the dried NiCo2O4 electrode is heat treated in air at 300°C for 1.5 hours.

[0056] Example 9

[0057] The difference from Example 1 is that in step S3, the dried NiCo2O4 electrode is heat treated in air at 200°C for 2 hours.

[0058] Comparative Example 1

[0059] The difference from Example 1 is that in step S2, heating to 650°C is at a heating rate of 2°C / min.

[0060] Comparative Example 2

[0061] The difference from Example 1 is that the NiCo2O4 electrode is immersed in 0.02M aqueous ferric nitrate nonahydrate solution and 0.08M sodium hydroxide solution for the immersion step, and the step is repeated 50 times.

[0062] Comparative Example 3

[0063] The difference from Example 1 is that the dried NiCo204electrode is heat treated in air at 500°C for 10 min in step S3.

[0064] Comparative Example 4

[0065] The difference from Example 1 is that only step S1 and step S2 are implemented, obtaining an oxygen evolution electrode with only a NiCo204catalytic layer on the surface.

[0066] Comparative Example 5

[0067] The difference from Example 1 is that the nickel substrate is immersed in a 0.02M aqueous solution of iron nitrate nonahydrate for 20s, and then the nickel substrate is taken out and immersed in deionized water for 30s. Subsequently, the immersed nickel substrate is immersed in a 0.08M sodium hydroxide solution for 30s, and then taken out and immersed in ionized water for 30s.

[0068] The above two steps are repeated 10 times. Then the immersed nickel substrate is dried at 60°C.

[0069] The dried nickel substrate is heat treated in air at 300°C for 1 hour, obtaining an oxygen evolution electrode with only an a-Fe203catalytic layer.

[0070] The electrodes prepared in Examples 1-9 and Comparative Examples 1-5 are subjected to electrochemical tests. Specifically, the electrochemical tests are carried out using a Bio Logic electrochemical workstation, a saturated calomel reference electrode, a 30wt% KOH solution, and a temperature of 80°C to test the LSV curves of the electrodes prepared in Examples 1-9 and Comparative Examples 1-5, and the oxygen evolution overpotential (ORE overpotential) at a current density of 500mA / cm 2 is calculated.

[0071] Table 1 Test data of the electrodes prepared in Examples 1-9 and Comparative Examples 1-5

[0072]

[0073] As can be seen from the above table, the oxygen evolution electrodes of Examples 1-9 have lower ORE overpotentials than the oxygen evolution electrodes of Comparative Examples 1-5, and the lower the overpotential, the lower the energy consumption required for the oxygen evolution electrode to undergo oxygen evolution reaction, and the higher the activity.

[0074] The oxygen evolution electrodes prepared in Comparative Examples 4-5 are tested under fluctuating power supply. The oxygen evolution electrode of Comparative Example 4, which has only a NiCo204catalytic layer, can stably operate at low to medium current density under fluctuating power supply, but its efficiency rapidly decreases or even cannot work at high current density. The oxygen evolution electrode of Comparative Example 5, which has only an a-Fe203catalytic layer, cannot stably operate at low to medium current density under fluctuating power supply.

[0075] The self-reconfigurable oxygen evolution electrode in Example 1 was tested at a low scan rate to test the initial LSV curve of the self-reconfigurable oxygen evolution electrode and the LSV curve of the electrode after the electrode was "reconfigured and activated" (polarized at a higher constant current density for several hours). As shown in Figure 2 , the initial OER performance of the self-reconfigurable oxygen evolution electrode was 277 mV@5000 A / m 2 , and the electrode performance after reconfiguration was 254 mV@5000 A / m 2 . Thus, the LSV curve after reconfiguration and activation showed that the electrode could reach a higher current density at the same overpotential, indicating that the self-reconfigurable oxygen evolution electrode achieved "self-upgrading" at high pressure and could meet the use requirements of high pressure.

[0076] The stability of the self-reconfigurable oxygen evolution electrode of Example 1 was tested. Specifically, the self-reconfigurable oxygen evolution electrode of Example 1 was operated under fluctuating power for 1000 hours, and the current density was set to jump between multiple steps, each step was maintained for a period of time, and the potential-time curve was recorded. Among them, the anode of the electrolytic cell was the self-reconfigurable oxygen evolution electrode of Example 1, the cathode was a pure nickel mesh, the diaphragm was a PPS diaphragm, the electrolyte was 30wt% concentration of KOH, and the cell temperature was 82℃.

[0077] As shown in Figure 3 , when the current step changes, the potential of the self-reconfigurable oxygen evolution electrode of Example 1 can quickly stabilize to a new platform, the response is fast, the dynamic performance is good, and it is shown that the self-reconfigurable oxygen evolution electrode of Example 1 has excellent stability under fluctuating power output.

[0078] Another embodiment of the present application provides a self-reconfigurable oxygen evolution electrode prepared by the above preparation method.

[0079] Still another embodiment of the present application provides an application of a self-reconfigurable oxygen evolution electrode in the field of hydrogen production by alkaline electrolysis of water under fluctuating power.

[0080] In summary, the preparation method of the self-reconfigurable oxygen evolution electrode of the application uses the two-step method of potentiostatic electrodeposition and successive ion layer adsorption reaction to construct a composite catalytic layer composed of spinel structure NiCo2O4 and α-Fe2O3 on a nickel substrate. The nickel substrate provides a conductive skeleton and a large specific surface area, the NiCo2O4 layer is a high-efficiency OER catalyst at a low to moderate current density of fluctuating power supply, and the highly dispersed α-Fe2O3 nanoparticles serve as a "backup" catalyst precursor. When the input power of the fluctuating power supply increases dramatically and the current density rises to a certain critical value, the electrode potential rises accordingly. In a high potential and strong alkaline environment, the originally weak OER active α-Fe2O3 will undergo irreversible electrochemical reconfiguration and transform into super-highly active γ-FeOOH (or iron-doped Ni / CoOOH). This process occurs in situ, thereby realizing the "self-upgrading" catalytic ability of the electrode under high power fluctuation, so that the electrode always maintains high efficiency. Therefore, the self-reconfigurable oxygen evolution electrode is mainly provided by NiCo2O4 at a low current density (such as when wind and solar power is weak), and when the current density rises sharply, the α-Fe2O3 will be in situ converted into high-activity γ-FeOOH at a high potential to realize "self-reconfiguration" to adapt to power fluctuations, solving the problem of high-efficiency oxygen evolution efficiency of the electrode under a wide current density. The self-reconfiguration process is fast and can keep up with the rapid changes of the fluctuating power supply, avoiding the rapid deactivation of a single material under non-design conditions.

[0081] It is apparent to those skilled in the art that the present disclosure is not limited to the details of the foregoing exemplary embodiments, and that the present disclosure can be implemented in other specific forms without departing from the spirit or essential characteristics of the present disclosure. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present disclosure should be defined by the appended claims rather than the above description, and it is intended to include all changes falling within the meaning and range of equivalents of the elements of the claims. Any reference signs in the claims should not be considered as limiting the claims involved.

[0082] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing a self-reconfigurable oxygen evolution electrode, characterized in that, Comprising: placing a nickel substrate as a working electrode, a platinum sheet as a counter electrode, and a saturated calomel electrode as a reference electrode in a NiCo2O4 precursor solution, performing constant potential electrodeposition on the nickel substrate to obtain a precursor electrode with a Ni-Co LDH precursor on the surface; placing the precursor electrode into a heating device, heating to 250-500°C at a heating rate of 2-4°C / min and maintaining for 2-3h, then taking out the precursor electrode and naturally cooling to 20-30°C to obtain a NiCo2O4 electrode with a spinel structure; placing the NiCo2O4 electrode into a ferric nitrate nonahydrate aqueous solution and a sodium hydroxide solution in sequence, loading α-Fe2O3 nanoparticles on the surface of the NiCo2O4 electrode using a successive ionic layer adsorption reaction method to obtain a self-reconstruction type oxygen evolution electrode; wherein loading α-Fe2O3 nanoparticles on the surface of the NiCo2O4 electrode using a successive ionic layer adsorption reaction method comprises: immersion of the NiCo2O4 electrode into an aqueous solution of iron nitrate nonahydrate for 5-30 s, so that Fe 3+ is adsorbed onto the surface of the NiCo2O4 electrode, removal and washing in deionized water for 25-35 s; immersing the NiCo2O4 electrode after the soaking into a sodium hydroxide solution for 20-60s, so that OH - reacts with Fe on the surface of the NiCo2O4 electrode to generate Fe(OH)3 precipitate, which is taken out and soaked with deionized water for 25-35s; 3+ reacts with Fe on the surface of the NiCo2O4 electrode to generate Fe(OH)3 precipitate, which is taken out and soaked with deionized water for 25-35s; repeating the above two steps multiple times, then drying the washed NiCo2O4 electrode at 55-65°C; heat treating the dried NiCo2O4 electrode in air at 200-400°C for 0.5-2h to convert amorphous Fe(OH)3 into α-Fe2O3 and load it on the surface of the NiCo2O4 electrode.

2. The method of claim 1, wherein the self-reconfiguring oxygen evolution electrode is prepared by the steps of: The deposition potential of the constant potential electrodeposition relative to the saturated calomel electrode is -0.5 to -2.0 V; the deposition temperature is 25-30°C; and the deposition time is 5-30 min.

3. The method of claim 1, wherein the self-reconfiguring oxygen evolution electrode is prepared by the steps of: The concentration of the ferric nitrate nonahydrate aqueous solution is 0.02-0.04 M; and / or, The concentration of the sodium hydroxide solution is 0.08-0.16 M.

4. The method of claim 1, wherein the self-reconfiguring oxygen evolution electrode is prepared by the steps of: The preparation of the precursor solution comprises: dissolving nickel nitrate hexahydrate, cobalt nitrate hexahydrate, and sodium nitrate in deionized water, magnetically stirring for 25-35 min until completely clear and transparent, and adjusting the pH to 6-6.5 to obtain the NiCo2O4 precursor solution.

5. The method of claim 4, wherein the self-reconfiguring oxygen evolution electrode is prepared by the steps of: The concentration of the nickel nitrate hexahydrate is 0.05-0.1 M; and / or; The concentration of the cobalt nitrate hexahydrate is 0.1-0.2 M; and / or; The concentration of the sodium nitrate is 0.1-0.2 M.

6. The method of claim 1, wherein the self-reconfiguring oxygen evolution electrode is prepared by the steps of: Also comprising pretreating the nickel substrate, the pretreatment comprising: ultrasonically cleaning the nickel substrate in acetone, anhydrous ethanol, and deionized water in sequence for 10-20 min; immersing the cleaned nickel substrate in dilute hydrochloric acid for 5-10 min; taking out the nickel substrate from the dilute hydrochloric acid and rinsing with deionized water, then drying in a vacuum drying oven at 55-65°C for 2-3h.

7. A self-reconstruction type oxygen evolution electrode prepared by the preparation method of any one of claims 1-6.

8. Use of the self-reconstruction type oxygen evolution electrode of claim 7 in the field of hydrogen production by alkaline electrolysis of water from fluctuating power sources.

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