Anode electrode and preparation method thereof, membrane electrode and water electrolyser

Abstract

The embodiment of the invention discloses an anode electrode and a preparation method thereof, a membrane electrode and a water electrolyser, the anode electrode comprises a precursor and oxygen-containing anions on a functional layer, the oxygen-containing anions can effectively regulate and control a local electronic structure of a metal active center of the precursor, and the electronic structure can optimize adsorption energy of an OER reaction intermediate; meanwhile, oxygen-containing anions are also beneficial to breaking a compact hydrated cation layer at an electrode / electrolyte interface, and the transmission rate and concentration of reactants such as hydroxyl (OH-) near metal active sites in the oxygen evolution process are improved, so that the catalytic activity of the catalyst under high current density is remarkably enhanced; in addition, the existence of oxygen-containing anions is also beneficial to enhancing the strength of metal-oxygen bonds (M-O), so that metal ions are anchored, the dissolution of the metal ions is inhibited, and the stability is remarkably improved.

Description

Technical Field

[0001] This application relates to the technical field of catalytic materials, specifically to an anode electrode and its preparation method, a membrane electrode, and a water electrolyzer. Background Technology

[0002] In alkaline water electrolysis systems, the oxygen evolution reaction (OER) at the anolyte is a critical factor limiting overall energy efficiency and equipment lifespan. Currently, the catalytic activity of commercially available anode electrodes mainly relies on noble metal oxides, such as RuO2 and IrO2. However, these oxides are expensive, scarce, and prone to dissolution and deactivation under strongly alkaline conditions, thus limiting their large-scale application.

[0003] In recent years, non-precious metal-based catalysts, especially nickel, iron, and cobalt-based compounds, have gradually become a research hotspot due to their advantages such as low cost, wide availability, and high catalytic activity.

[0004] However, non-noble metal-based compounds at high current densities (≥1 A / cm²) 2 Problems such as metal ion dissolution, lattice oxygen escape, and structural collapse can easily occur under these conditions, leading to a rapid decline in catalytic activity and making it difficult to meet the requirements of industrial-grade electrolyzers for material lifespan and stability. Summary of the Invention

[0005] This application provides an anode electrode and its preparation method, a membrane electrode and a water electrolyzer, aiming to solve the problem of rapid decay of catalytic activity caused by poor stability of existing anode electrodes under high current density, metal ion dissolution and lattice oxygen escape.

[0006] In a first aspect, this application provides an anode electrode, the anode electrode comprising a conductive substrate and a functional layer located on the conductive substrate; The functional layer includes a precursor and oxygen-containing anions contained in the interlayer and / or surface of the precursor. The precursor includes layered double hydroxides, hydroxides and / or metal oxides.

[0007] Optionally, in some embodiments of this application, the layered double hydroxide, hydroxide, and / or metal oxide is nickel-iron-based, nickel-manganese-based, nickel-cobalt-based, or cobalt-iron-based layered double hydroxide, hydroxide, and / or metal oxide; and / or The oxygen-containing anion includes at least one selected from nitrate, phosphate, formate, sulfate, borate, molybdate, tungstate, vanadate, and chromate; and / or The conductive substrate includes at least one of metal foam, metal felt, metal mesh, and carbon fiber products.

[0008] Optionally, in some embodiments of this application, the metal element content in the nickel-iron-based, nickel-manganese-based, nickel-cobalt-based, and cobalt-iron-based morphological double hydroxides, hydroxides, and / or metal oxides is 1 to 4 times that of the former and the latter.

[0009] Optionally, in some embodiments of this application, the mass percentage of the oxygen-containing anion in the precursor is 0.4% to 5%.

[0010] Optionally, in some embodiments of this application, the thickness of the anode electrode is 0.1 to 1 mm.

[0011] Optionally, in some embodiments of this application, the areal density of the anode electrode is 100 to 1500 g / m³. 2 .

[0012] Secondly, embodiments of this application provide a method for preparing an anode electrode, used to prepare the anode electrode as described above, the preparation method comprising the following steps: Provide a conductive substrate; The precursor is grown in situ on the conductive substrate, and the precursor includes layered double hydroxides, hydroxides and / or oxides. The precursor is placed in an electrolyte containing oxygen-containing anions, and oxygen-containing anions are introduced by a pulse voltage method to form the anode electrode.

[0013] Optionally, in some embodiments of this application, the step of growing the precursor in situ on the conductive substrate includes: The metal source is dissolved in a solvent to obtain a precursor solution; The conductive substrate is placed in the precursor solution and subjected to a hydrothermal reaction at a preset temperature to obtain the precursor.

[0014] Optionally, in some embodiments of this application, the metal source includes at least two of nickel salt, iron salt, manganese salt, and cobalt salt; and / or the molar ratio of the metal sources ranges from 0.5 to 3; and / or The preset temperature range is 80°C. o C to 90 o C or 180°C to 200°C.

[0015] Optionally, in some embodiments of this application, the conductive substrate loaded with layered double hydroxides, hydroxides, and / or metal oxides is used as the anode, and the step of applying a pulse voltage method includes: Provides an electrolyte containing oxygen-containing anions; The conductive substrate loaded with layered double hydroxides, hydroxides and / or metal oxides is placed in an electrolyte, and the anode electrode is obtained by applying pulses and relaxation cycles alternately.

[0016] Optionally, in some embodiments of this application, the voltage of the pulse ranges from 1.2V to 1.4V; and / or The duration of the pulse ranges from 3 seconds to 10 seconds; and / or The system is at an open-circuit potential during the relaxation period; and / or the relaxation time ranges from 6 s to 20 s; and / or The number of alternating cycles ranges from 50 to 200.

[0017] Thirdly, embodiments of this application provide a membrane electrode, which includes an anode electrode as described above or an anode electrode prepared by the aforementioned anode electrode preparation method.

[0018] Fourthly, embodiments of this application provide a water electrolyzer, the electrolyzer including a membrane electrode as described above or an anode electrode as described above.

[0019] The anode electrode in this embodiment includes a precursor and oxygen-containing anions in its functional layer. The oxygen-containing anions can effectively modulate the local electronic structure of the precursor, thereby optimizing the adsorption energy of the OER reaction intermediate. At the same time, the oxygen-containing anions can form strong hydrogen bonds with the dense hydrated cation layer at the electrode / electrolyte interface, providing a transport channel for hydroxide ions (OH-), increasing the transport rate and concentration of hydroxide ions (OH-) near the metal active site, thereby significantly enhancing the catalytic activity of the catalyst at high current densities. In addition, the presence of oxygen-containing anions also helps to enhance the strength of the metal-oxygen bond (MO), thereby anchoring metal ions and inhibiting the dissolution of metal ions, thus significantly improving stability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the method for preparing the anode electrode provided in the embodiments of this application; Figure 2 This is the result of the stability test of the embodiment of this application, a time-voltage curve. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] According to a first aspect of the embodiments of this application, an anode electrode is provided, the anode electrode including a conductive substrate and a functional layer located on the conductive substrate; The functional layer includes a precursor, the interlayer and / or surface of which contain oxygen-containing anions. The precursor includes layered double hydroxides, hydroxides and / or metal oxides.

[0024] It is understood that oxyanions exist in the form of ionic groups and are part of layered double hydroxides, hydroxides, and / or metal oxides. For example, taking layered double hydroxides (LDHs) as an example, during electrochemical treatment, oxyanions in the electrolyte are driven by electrochemical polarization to move to the vicinity of the precursor. Some of these oxyanions combine with the positively charged LDH main layer through electrostatic interactions and hydrogen bonds, replacing the original interlayer anions (carbonate ions, CO32-) of the LDH. 2- The metal is intercalated into the interlayer of the LDH, and at the same time, some of the metals that are poorly coordinated with the surface are chemically adsorbed onto the precursor surface through covalent bonds.

[0025] By adopting the above scheme, the anode electrode of this application embodiment includes a precursor and oxygen-containing anions in the functional layer. The oxygen-containing anions can effectively regulate the local electronic structure of the metal active center of the precursor, and this electronic structure can optimize the adsorption energy of the reaction intermediates in the OER process. At the same time, the oxygen-containing anions form hydrogen bonds with the dense hydrated cation layer at the electrode / electrolyte interface, which is OH- - The transport to the functional layer surface opens channels, improving OH - The transport rate and concentration near the metal active sites significantly enhance the catalytic activity of the anode electrode at high current densities. It should also be noted that the combination of oxygen-containing anions with the metal active sites of the precursor enhances the bond energy of the metal-oxygen bond, effectively anchoring the metal active sites. This interaction effectively suppresses the dissolution of metal ions under high potential and high current density conditions, as well as the resulting lattice oxygen loss and structural collapse, allowing the functional layer to maintain structural integrity and catalytic activity even under harsh industrial conditions.

[0026] In some embodiments of this application, the anode electrode includes a non-precious metal anode electrode.

[0027] By adopting the above scheme, non-precious metal-based compounds are directly grown on a conductive substrate as OER catalysts. Through the synergistic effect between different metal species and the further optimization of the metal active sites by the introduction of oxygen-containing anions, OER catalytic activity almost comparable to that of precious metal oxides (such as IrO2 and RuO2) is achieved, and even better stability than precious metal oxides in alkaline water electrolysis. It is understandable that, compared to precious metal oxides, non-precious metal-based compounds have the advantages of high reserves and low cost, which is beneficial to the industrial development of hydrogen production through water electrolysis.

[0028] In some embodiments of this application, the layered double hydroxide, hydroxide and / or metal oxide are nickel-iron-based, nickel-manganese-based, nickel-cobalt-based and cobalt-iron-based layered double hydroxides, hydroxides and / or metal oxides.

[0029] By adopting the above scheme, the first metal (M1), nickel and / or cobalt, is the main active site. The introduced second metal (M2), iron, manganese, and / or cobalt, can regulate the electronic structure of the first metal site, reducing the energy barrier for forming a highly active phase (M1M2OOH). Simultaneously, the second metal can also serve as a supplementary active site, synergistically catalyzing the OER reaction with the first metal, thereby enhancing the catalytic activity of the functional layer. The introduced oxygen-containing anions alter the electron density and d-band center of the metal active center through metal-oxygen bonds (MO), increasing the proportion of high-valence metal ions and forming highly oxidized active sites. This further optimizes the adsorption energy of intermediates (*OH, *O, *OOH) in the oxygen evolution process of water electrolysis, reducing the reaction energy barrier of the rate-determining step of OER, thereby improving the OER catalytic performance of the anode electrode. It should also be noted that during the OER process, layered double hydroxides, hydroxides, and / or metal oxides are reconstructed into a more reactive hydroxyl oxide (M1M2OOH) phase. The presence of oxygen-containing anions can promote and stabilize this reconstruction process, forming a highly active, amorphous surface structure rich in anions. This structure exhibits high activity and high stability, thereby ensuring the efficient and long-term stable operation of the functional layer. In some embodiments of this application, the oxygen-containing anions include at least one selected from nitrate, phosphate, formate, sulfate, borate, molybdate, tungstate, vanadate, and chromate.

[0030] By employing the above scheme, different oxygen-containing anions possess different geometric configurations, charge numbers, and electronegativity. It is precisely because of these differences that different oxygen-containing anions can be selected to regulate the local electronic structure of the precursor. Furthermore, selecting different oxygen-containing anions can optimize their adsorption strength on the precursor. Different oxygen-containing anions can form strong coordination or strong electrostatic interactions with the metal ions of the precursor. This strong interaction enhances the strength of the metal-oxygen covalent bond, effectively locking the active metal sites and preventing their dissolution during the catalytic OER process due to harsh anodic oxidation conditions. This fundamentally solves the performance degradation caused by changes in catalyst chemical composition and mechanical damage under high current densities.

[0031] In some embodiments of this application, the conductive substrate includes at least one of metal foam, metal felt, metal mesh, and carbon fiber products.

[0032] In some embodiments of this application, the mass percentage of oxyanions in the precursor is 0.4% to 5%. Exemplarily, the mass percentage of oxyanions in the precursor is 0.4%, 0.6%, 0.8%, 1%, 1.3%, 1.5%, 1.7%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.1%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, and any value between two adjacent values.

[0033] By employing the above scheme, the mass percentage of oxygen-containing anions in the precursor is controlled within the aforementioned range, achieving precise control of the anolyte performance. Too few oxygen-containing anions are insufficient to produce significant electronic regulation and anchoring effects; while excessive oxygen-containing anions may cover metal active sites. The oxygen-containing anion content within the aforementioned range significantly improves stability while ensuring optimal catalytic activity, solving the problem that traditional layered double hydroxides, hydroxides, and / or metal oxides struggle to achieve both high activity and high stability. In some embodiments of this application, the metal element content in nickel-iron-based, nickel-manganese-based, nickel-cobalt-based, and cobalt-iron-based layered double hydroxides, hydroxides, and / or metal oxides is 1 to 4 times the ratio of the former to the latter. Exemplarily, the metal element content ratio is 1, 0.5, 2, 2.5, 3, 3.5, 4, or any value between two adjacent values. By employing the above scheme and controlling the metal content ratio within the aforementioned range, the resulting local geometry and electronic structure exhibit optimal adsorption energy for the OER reaction intermediate, which is most conducive to the reaction. This ratio of functional layers achieves maximum activity while maintaining structural stability and conductivity.

[0034] In some embodiments of this application, the thickness of the anode electrode is 0.1 to 1 mm. Exemplarily, the thickness of the anode electrode is 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 0.9 mm, 1 mm, and any value between two adjacent values.

[0035] By adopting the above scheme, the thickness of the anode electrode can be controlled within the above range, which is beneficial for adapting to water electrolysis cells with different structures.

[0036] In some embodiments of this application, the areal density of the anode electrode is 100 g / m³. 2 Up to 1500g / m 2 For example, the areal density of the anode electrode is 100 g / m³. 2 300g / m 2 500g / m 2 700g / m 2 900g / m 2 1100g / m 2 1300g / m 2 1500g / m 2 And any value between the two adjacent values ​​mentioned above.

[0037] By adopting the above scheme and controlling the areal density of the anode electrode within the above range, it is beneficial to achieve optimal water-gas transport in the water electrolyzer, so that the electrolyte can be delivered to the electrode as quickly as possible to participate in the reaction, and the product gas can be discharged quickly to avoid the burial of active sites due to gas accumulation; at the same time, it has sufficient surface area to provide active sites for the reaction to occur.

[0038] According to a second aspect of the embodiments of this application, a method for preparing an anode electrode is provided, for preparing an anode electrode as described above. Please refer to [link to relevant documentation]. Figure 1 The preparation method includes the following steps: S10, Provides a conductive substrate; S20. In-situ growth of precursors on a conductive substrate; S30. Place the precursor in an electrolyte containing oxygen-containing anions, and introduce oxygen-containing anions by pulse voltage method to form an anode electrode. By adopting the above-described scheme, the embodiments of this application directly grow layered double hydroxides, hydroxides, and / or metal oxides as precursors on a conductive substrate, avoiding the problem of using binders in powder catalysts. The precursor is electrochemically treated using a pulsed voltage method to introduce oxygen-containing anions, forming the anode electrode. This helps to solve the problem of irreversible structural collapse and other mechanical damage to the precursor during electrochemical treatment. This scheme provides an anode electrode that solves the problem of poor operational stability caused by metal ion dissolution during the catalytic oxygen evolution process.

[0039] In some embodiments of this application, the step of growing a precursor in situ on a conductive substrate includes: The metal source is dissolved in a solvent to obtain a precursor solution; The conductive substrate is placed in the precursor solution and heated at a preset temperature to obtain the precursor.

[0040] By adopting the above scheme, the precursor is grown in situ on the conductive substrate, rather than physically adhered. This structure helps to ensure that the final functional layer is not easily detached from the conductive substrate or pulverized under harsh conditions of high current density and large oxygen scouring, thus solving the mechanical stability problem of the functional layer. In addition, the chemical connection between the precursor and the conductive substrate allows electrons to be transferred to the conductive substrate through the active sites of the catalytic reaction, which greatly reduces the interfacial contact resistance, which is beneficial to the OER reaction and thus achieves efficient catalysis.

[0041] In some embodiments of this application, the metal source includes at least two of the following: nickel salt, iron salt, manganese salt, and cobalt salt.

[0042] Understandably, the fundamental role of these types of metal salts is to provide the metal ions required for the synthesis of layered double hydroxides.

[0043] Understandably, taking nickel-iron base-based double hydroxides as an example, under hydrothermal conditions, nickel and iron ions co-precipitate with ionized hydroxide ions in the solution and undergo grain ripening and growth to obtain the precursor.

[0044] In some embodiments of this application, the molar ratio of the metal sources ranges from 0.5 to 3. For example, the molar ratio of the nickel source to the iron source can be 0.5, 0.8, 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, 3, or any value between two adjacent values ​​mentioned above.

[0045] By adopting the above scheme, a suitable molar ratio helps to form a more stable and active crystal phase, ensuring that the metal content ratio in the product is controlled within the required range, achieving optimal local geometry and electronic structure, thereby guaranteeing high activity and high stability of the anode electrode. In some embodiments of this application, the preset temperature range is 80°C. o C to 90 o C. For example, the preset temperature can be 80. o C, 81 o C, 82 o C, 83 o C, 84 o C, 85 o C, 86 o C, 87 o C、88 o C, 89o C, 90 o C and any value between the two adjacent values ​​mentioned above.

[0046] By employing the above-described scheme and setting the temperature within the aforementioned range, layered double hydroxides with specific morphologies can be grown in situ on a conductive substrate. The lamellar array structure of LDH significantly increases the specific surface area, exposing more active sites. Simultaneously, it provides a channel for electrolyte wetting and the rapid release of oxygen generated during the reaction, preventing bubbles from clogging the metal active sites. In some embodiments of this application, the preset temperature ranges from 180°C. o C to 200 o C. For example, the preset temperature can be 180°C. o C, 182 o C, 184 o C, 186 o C, 188 o C, 190 o C, 192 o C, 194 o C, 196 o C, 198 o C, 200 o C and any value between the two adjacent values ​​mentioned above.

[0047] By adopting the above scheme and setting the temperature within the above range, oxides with specific morphologies can be grown in situ on a conductive substrate. At high temperatures, the hydroxides that precipitate first are unstable and undergo dehydration reactions, while the metal oxides are much more thermodynamically stable than the hydroxides. Ultimately, under high-temperature hydrothermal conditions, well-crystallized metal oxides with uniform particle size are formed.

[0048] In some embodiments of this application, the step of placing the precursor in an electrolyte containing oxygen-containing anions and electrochemically treating it using a pulsed voltage method includes: The precursor is placed in an electrolyte containing oxygen-containing anions, and the anode electrode is obtained by alternating cycles of pulse application and relaxation.

[0049] By adopting the above scheme, a pulsed voltage is applied to drive the oxygen-containing anions in the electrolyte to intercalate or adsorb into the precursor, and the lattice stress is released through relaxation. By alternating between applying pulses and relaxation, structural collapse and channel blockage caused by excessive oxidation of the precursor are prevented, which would result in poor catalytic performance of the synthesized anode electrode.

[0050] In some embodiments of this application, the voltage of the pulse ranges from 1.2V to 1.4V. Exemplarily, the voltage of the pulse can be 1.2V, 1.25V, 1.3V, 1.35V, 1.4V, or any value between two adjacent values ​​mentioned above.

[0051] In some embodiments of this application, the pulse duration ranges from 3s to 10s. Exemplarily, the pulse duration can be 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, or any value between two adjacent values ​​mentioned above.

[0052] By employing the above scheme and within a suitable time range, it is beneficial to control the degree of precursor reaction. The pulse duration determines the reaction time. If the time is too short, the anions will not have enough time to move to the vicinity of the anode and interact with the precursor under the influence of the electric field. If the time is too long, it may cause irreversible damage to the functional layer under continuous oxidation potential. The degree of reaction introducing oxygen-containing anions can be controlled by increasing the number of cycles.

[0053] In some embodiments of this application, the system is at an open-circuit potential during the relaxation period. In some embodiments of this application, the relaxation time ranges from 6s to 20s. Exemplarily, the relaxation time can be 6s, 7s, 8s, 9s, 10s, 12s, 15s, 17s, 20s, or any value between two adjacent values ​​mentioned above.

[0054] By adopting the above scheme, the appropriate relaxation period can release the lattice stress, thereby preventing structural collapse and channel blockage caused by excessive oxidation of the functional layer. The relaxation time is twice the applied pulse time, allowing the oxidation reaction system enough time to recover to a stable state and release the lattice stress.

[0055] In some embodiments of this application, the number of alternating cycles ranges from 50 to 200. Exemplarily, the number of cycles can be 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, or any value between two adjacent values ​​mentioned above.

[0056] According to a third aspect provided in the embodiments of this application, a membrane electrode is provided, the membrane electrode including an anode electrode as described above.

[0057] By adopting the above-described scheme, the membrane electrode provided in this application embodiment has all the beneficial effects of the aforementioned anode electrode, which will not be repeated here.

[0058] According to a fourth aspect provided in the embodiments of this application, a water electrolyzer is provided, the electrolyzer including the membrane electrode as described above.

[0059] By adopting the above-described scheme, the water electrolyzer provided in this application embodiment includes all the beneficial effects of the membrane electrode as described above, which will not be repeated here.

[0060] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0061] Example 1 A membrane electrode is prepared by the following steps: S100, dissolve 0.1M nickel nitrate hexahydrate and 0.05M ferric chloride in pure water to obtain a precursor solution; S200. The conductive nickel felt substrate is placed vertically in the precursor solution at 85°C. o A nickel felt-loaded precursor was obtained by bathing in a water bath at C for 4 hours, then washed with ethanol and dried at room temperature. S300, Place the above precursor in a container containing the target oxygen-containing anion PO4. 3- In a potassium hydroxide solution with a 0.2 M concentration of oxygen-containing anions, a pulse voltage of 1.35 V was applied for 5 s, followed by a relaxation time of 10 s. This process was repeated 150 times, alternating between pulse and relaxation cycles. The electrode was then cleaned with ethanol and dried at room temperature to obtain an anode electrode with a thickness of 0.4 mm and an areal density of 500 g / m³. 2 ; S400: Carbon cloth, Pt / C coated anion exchange membrane, and the aforementioned anode electrode are placed sequentially and hot-pressed for a period of time to form an AEM membrane electrode for use in an AEM water electrolysis cell. The hot-pressing pressure is 300 psi, the hot-pressing temperature is 80℃, and the hot-pressing time is 15 minutes to obtain the membrane electrode.

[0062] Example 2 The difference between Example 2 and Example 1 lies in the duration of the applied pulse voltage and the relaxation time. In this example, the constant voltage time is 3 seconds and the relaxation time is 6 seconds, while the rest remains the same as in Example 1.

[0063] Example 3 The difference between Example 3 and Example 1 lies in the duration of the applied pulse voltage and the relaxation time. In this example, the constant voltage time is 10s and the relaxation time is 20s, while the rest remains the same as in Example 1.

[0064] Example 4 The difference between Example 4 and Example 1 lies in the number of alternating cycles. In this example, the number of alternating cycles is 50, while the rest remains the same as in Example 1.

[0065] Example 5 The difference between Example 5 and Example 1 lies in the number of alternating cycles. In this example, the number of alternating cycles is 200, while the rest remains the same as in Example 1.

[0066] Example 6 The difference between Example 6 and Example 1 is that the concentration of oxygen-containing anions is different. In this example, the concentration of oxygen-containing anions is 0.05M, and the rest is the same as in Example 1.

[0067] Example 7 The difference between Example 7 and Example 1 is the concentration of oxygen-containing anions. In this example, the concentration of oxygen-containing anions is 0.5M, while the rest is the same as in Example 1.

[0068] Example 8 The difference between Example 8 and Example 1 lies in the type of oxyanion used; in this example, the oxyanion is WO4. 2- The rest remains the same as in Example 1.

[0069] Example 9 The difference between Example 9 and Example 1 is that the precursor solution is different. In this example, the precursor solution is 0.1M nickel nitrate hexahydrate and 0.05M manganese chloride dissolved in pure water, and the rest is the same as in Example 1.

[0070] Example 10 The difference between Example 10 and Example 1 is that the temperature applied in step S200 is different. In this example, the conductive substrate and the precursor solution are placed in a reaction vessel and reacted at 180°C for 4 hours. The rest is the same as in Example 1.

[0071] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that step S300 is missing, while the rest is the same as Example 1.

[0072] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 lies in the molar ratio of nickel salt to iron salt. In this comparative example, the molar ratio of nickel salt to iron salt is 1:2, while the rest remains unchanged from Comparative Example 1.

[0073] Comparative Example 3 The difference between Comparative Example 3 and Comparative Example 1 lies in the molar ratio of nickel salt to iron salt. In this comparative example, the molar ratio of nickel salt to iron salt is 3:1, while the rest remains unchanged from Comparative Example 1.

[0074] Comparative Example 4 The difference between Comparative Example 4 and Example 9 is that step S300 is missing, while the rest is the same as Example 9.

[0075] Comparative Example 5 The difference between Comparative Example 5 and Example 10 is that step S300 is missing, while the rest is the same as Example 10.

[0076] Performance testing: The membrane electrode assembly, cathode plate (with flow field), anode plate (with flow field), end plate, and insulating plate were assembled into a water electrolysis cell for testing. The test conditions were: the temperature of the electrolysis cell was 80°C. o C, The electrolyte is a 1M KOH solution; (1) Oxygen-containing anions: The amount of oxygen-containing anions introduced is evaluated by EDS testing of the content of a certain element unique to oxygen-containing anions; (2) Polarization performance: Using an electrochemical workstation and the step current method, the system current density was measured from 0 A / cm². 2 Increased to 1A / cm 2 The step size is 0.1A, the test time for each current is 10s, and a voltage value is recorded every second. The average voltage of each current is recorded. (3) Charge transfer resistance: Using an electrochemical workstation, the constant voltage AC impedance of the test object was tested under a constant current of 2A. The high frequency was set to 100,000 Hz, the low frequency to 1 Hz, and the amplitude to 200 mA. After fitting the test results, the charge transfer resistance (Rct) value was recorded. (4) Stability: Using an electrochemical workstation, the chronoamperometry method was adopted, and the current density of the system was 1A / cm2. The AEMWE stability curve was obtained after data processing. (5) Metal leaching: The Fe content of the sample before and after 200h stability test was tested using an XRF testing instrument.

[0077] The test results of the water electrolyzer are shown in Table 1. Table 1

[0078] The test results of the oxygen-containing anion content are shown in Table 2. Table 2

[0079] The changes in metal content during the catalytic process are shown in Table 3. Table 3

[0080] Compared with Comparative Examples 1-5, Examples 1-10 combine pulsed voltage and relaxation in step S300, while Comparative Examples 1-5 lack step S300. As shown in Table 1, the charge transfer resistance decreases after the introduction of oxygen-containing anions, indicating an improvement in the intrinsic activity of the catalyst. This may be due to the oxygen-containing anions modulating the local electronic structure of the active sites, optimizing the adsorption energy of the reaction intermediates, thus achieving high OER catalytic activity; or it may be due to the strong hydrogen bond formed between the oxygen-containing anions and the hydrated cation layer at the double layer, resulting in OH groups. -Migration opens up pathways, promoting the adsorption of reactants at active sites and thus enhancing catalytic activity. This enhanced activity is reflected in the polarization performance of the electrolyzer; at the same current density, the cell voltage is lower after introducing a catalyst containing oxygen anions.

[0081] Combining Example 1 and Comparative Example 1 with Table 3, it can be seen that the loss of metallic iron ions decreases after the introduction of oxygen-containing anions; combined with Figure 2 It can be seen that when a constant current density (1 A / cm²) is applied... 2 During long-term stable operation, the introduction of oxygen-containing anions resulted in a slower rise in cell voltage. Overall, this indicates that the presence of oxygen-containing anions can inhibit the dissolution of metal ions from the catalyst, thereby improving catalyst stability. In the electrolytic cell, this manifests as a slower rise in cell voltage under constant current density (1 A / cm²). 2 During long-term stable operation, the tank pressure rises more slowly after the introduction of oxygen-containing anions. This may be achieved through the interaction between oxygen-containing anions and metal sites, which enhances the metal-oxygen bond.

[0082] Compared to Examples 1 and 6-7, the concentration of oxygen-containing anions in the electrolyte during the electrochemical treatment was changed. Table 2 shows that, according to EDS testing, the mass percentage of oxygen-containing anions in Examples 1 and 6-7 ranged from 0.47% to 4.52%. No phosphorus (P) was introduced during the initial preparation process; the P in the product could only originate from phosphate groups in the electrolyte during the electrochemical treatment in step S300. The presence of P proves the successful introduction of phosphate groups, and the P content in the product increases with the increase of phosphate concentration in the electrolyte during step S300. This indicates that the amount of oxygen-containing anions in the product can be controlled by adjusting the concentration of oxygen-containing anions in the electrolyte. Furthermore, Table 1 shows that too few oxygen-containing anions are insufficient to produce a significant electronic modulation effect to improve catalyst activity; while excessive oxygen-containing anions may cover metal active sites and inhibit catalyst activity. An appropriate amount of oxygen-containing anions is beneficial for improving catalyst activity, resulting in lower cell voltage in the electrolyzer.

[0083] Compared with Comparative Example 4, Example 9 combines pulsed voltage with relaxation in step S300, while Comparative Example 4 lacks step S300. As shown in Table 1, the prepared nickel-manganese layered double hydroxide exhibits similar performance optimization to the nickel-iron layered double hydroxide after the introduction of anionic groups, with a lower cell voltage at the same current density. The method of introducing oxygen-containing anions to optimize OER catalytic activity is universally applicable to other metal-based layered double hydroxides.

[0084] Comparing Example 10 and Comparative Example 5, Example 10 combines pulsed voltage application with relaxation in step S300, while Comparative Example 5 lacks step S300. As shown in Table 1, the prepared nickel-iron oxide exhibits similar performance optimization to the nickel-iron layered double hydroxide after the introduction of anionic groups, with a lower cell voltage at the same current density. The method of introducing oxygen-containing anions to optimize OER catalytic activity is universally applicable to metal oxides.

[0085] The foregoing has provided a detailed description of an anode electrode and its preparation method, a membrane electrode, and a water electrolyzer provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An anode electrode, characterized in that, The anode electrode includes a conductive substrate and a functional layer located on the conductive substrate; The functional layer includes a precursor and oxygen-containing anions contained in the interlayer and / or surface of the precursor. The precursor includes layered double hydroxides, hydroxides and / or metal oxides.

2. The anode electrode according to claim 1, characterized in that, The layered double hydroxides, hydroxides, and / or metal oxides are nickel-iron-based, nickel-manganese-based, nickel-cobalt-based, and cobalt-iron-based layered double hydroxides, hydroxides, and / or metal oxides; and / or The oxygen-containing anion includes at least one selected from nitrate, phosphate, formate, sulfate, borate, molybdate, tungstate, vanadate, and chromate; and / or The conductive substrate includes at least one of metal foam, metal felt, metal mesh, and carbon fiber products.

3. The anode electrode according to claim 2, characterized in that, The metal element content ratio in the layered double hydroxides, hydroxides and / or metal oxides of nickel-iron-based, nickel-manganese-based, nickel-cobalt-based and cobalt-iron-based materials is 1 to 4 times that of the latter.

4. The anode electrode according to claim 1, characterized in that, The mass percentage of the oxygen-containing anion in the precursor is 0.4% to 5%.

5. The anode electrode according to claim 1, characterized in that, The thickness of the anode electrode is 0.1 to 1 mm.

6. The anode electrode according to claim 1, characterized in that, The areal density of the anode electrode is 100 to 1500 g / m³. 2 .

7. A method for preparing an anode electrode, characterized in that, The method for preparing the anode electrode as described in any one of claims 1 to 6 comprises the following steps: Provide a conductive substrate; The precursor is grown in situ on the conductive substrate, wherein the precursor comprises layered double hydroxides, hydroxides and / or metal oxides; The precursor is placed in an electrolyte containing oxygen-containing anions, and oxygen-containing anions are introduced by a pulse voltage method to form the anode electrode.

8. The method for preparing the anode electrode according to claim 7, characterized in that, The step of growing the precursor in situ on the conductive substrate includes: The metal source is dissolved in a solvent to obtain a precursor solution; The conductive substrate is placed in the precursor solution and heated at a preset temperature to obtain the precursor.

9. The method for preparing the anode electrode according to claim 8, characterized in that, The metal source includes at least two of nickel salts, iron salts, manganese salts, and cobalt salts; the molar ratio of the metal sources ranges from 0.5 to 3; and / or The preset temperature range is 80°C. o C to 90 o C or 180°C to 200°C.

10. The method for preparing the anode electrode according to claim 7, characterized in that, The step of placing the precursor in an electrolyte containing oxygen-containing anions and treating it using a pulse voltage method includes: The precursor is placed in an electrolyte containing oxygen-containing anions, and the anode electrode is obtained by alternating cycles of pulse application and relaxation.

11. The method for preparing the anode electrode according to claim 10, characterized in that, The voltage of a single pulse ranges from 1.2V to 1.4V; and / or The duration of a single pulse ranges from 3 seconds to 10 seconds; and / or The single relaxation time ranges from 6s to 20s; and / or The number of alternating cycles ranges from 50 to 200.

12. A membrane electrode, characterized in that, The membrane electrode includes an anode electrode as described in any one of claims 1 to 6 or an anode electrode prepared by the method described in any one of claims 7 to 11.

13. A water electrolysis cell, characterized in that, The electrolytic cell includes the membrane electrode as described in claim 12 or the anode electrode as described in any one of claims 1 to 6.

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