NiFe-LDH Oxygen Evolution Electrode and Its Preparation Method

Abstract

This application provides a NiFe-LDH oxygen evolution electrode and its preparation method. The preparation method of the NiFe-LDH oxygen evolution electrode includes the following steps: using a conductive substrate as the working electrode, it is placed in a first electroplating solution for a first electrodeposition treatment. The first electroplating solution contains a first ferrous salt, a first nickel salt, and polytetrafluoroethylene (PTFE), and a first catalyst layer is deposited on the conductive substrate to form a first catalyst layer. This application forms a first catalyst layer by electrodepositing a conductive substrate in an electroplating solution containing a first ferrous salt, a first nickel salt, and PTFE. The first catalyst layer has a heterogeneous surface composed of hydrophilic catalyst active centers and dispersed hydrophobic PTFE sites, which can significantly reduce the average desorption diameter of bubbles, shorten bubble residence time, improve mass transfer efficiency, eliminate bubble shielding effect, and enhance the bonding strength between the catalyst layer and the conductive substrate, as well as the interior of the catalyst layer, thereby improving the mechanical stability and service life of the electrode.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by water electrolysis, and in particular to a NiFe-LDH oxygen evolution electrode and its preparation method. Background Technology

[0002] In the process of producing hydrogen through water electrolysis, the hydrogen evolution reaction (HER) occurs at the cathode and the oxygen evolution reaction (OER) occurs at the anode. Among them, the oxygen evolution reaction at the anode involves a four-electron-proton coupling transfer process, which has slow reaction kinetics and high energy loss, and is a key bottleneck restricting the overall efficiency of water electrolysis and increasing energy consumption costs.

[0003] Traditional OER electrodes are mostly prepared by coating powdered catalysts with binders such as Nafion (perfluorosulfonic acid resin) and PVDF (polyvinylidene fluoride). These non-self-supporting electrodes have significant drawbacks: the insulating properties of the binder increase interfacial resistance, reduce electron transport efficiency, and it easily encapsulates active sites and blocks pores, hindering electrolyte and gas mass transfer and degrading catalytic performance and stability. To address these issues, self-supporting electrodes have become a research hotspot. These electrodes are formed by in-situ growth of active materials on a substrate, resulting in superior electron conduction and mass transfer, and a more stable structure.

[0004] Electrodeposition is a common method for fabricating self-supporting electrodes. For example, patent CN116445964A discloses the deposition of a nickel-iron hydroxide (NiFe-LDH) layer on a conductive substrate via electroplating. The NiFe-LDH oxygen evolution electrode prepared by this method exhibits outstanding activity. However, at high current densities (500 mA / cm²), [further action is required]. 2 Under the above conditions, the NiFe-LDH oxygen evolution electrode still faces serious structural stability challenges, making long-term stable operation difficult. Firstly, the bubble shielding effect leads to impeded mass transfer and performance degradation: The NiFe-LDH surface is strongly hydrophilic, causing bubbles to easily pinnate and coalesce into large bubbles, covering the reaction interface and reducing the effective active area. This also triggers local current, pH, and temperature anomalies, accelerating catalyst corrosion and dissolution, and structural collapse, further deteriorating electrode stability and catalytic performance. Secondly, bubble erosion easily leads to mechanical failure: Under high current, the electrode rapidly evolves oxygen. The shear and impact forces generated by the bubbles repeatedly act on the brittle and weakly bonded inorganic catalyst layer, easily causing crack propagation, leading to catalyst layer cracking and peeling, and rapid electrode failure. Summary of the Invention

[0005] Therefore, it is necessary to provide a NiFe-LDH oxygen evolution electrode and its preparation method to solve the problems of difficult bubble desorption and poor structural stability of traditional electrodeposited self-supporting electrodes under high current density. To solve the above problems, this application uses an electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene to electrodeposit a conductive substrate to form a first catalytic layer. This first catalytic layer has a heterogeneous surface composed of hydrophilic catalyst active centers and dispersed hydrophobic polytetrafluoroethylene sites. The hydrophobic sites are beneficial for degassing, while the polytetrafluoroethylene can act as a stress buffer, improving the mechanical stability and service life of the electrode under high current impact.

[0006] A method for preparing a NiFe-LDH oxygen evolution electrode includes the following steps:

[0007] Using a conductive substrate as the working electrode, a first electrodeposition process is performed in a first electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene, thereby depositing a first catalytic layer on the conductive substrate.

[0008] In one embodiment, the conductive substrate is at least one of nickel foam, nickel mesh, nickel felt, and stainless steel mesh.

[0009] In one embodiment, the first ferrous salt includes at least one of FeCl2, FeSO4, and Fe(NO3)2.

[0010] In one embodiment, the first nickel salt includes at least one of NiCl2, NiSO4, and Ni(NO3)2.

[0011] In one embodiment, the concentration of ferrous ions in the first electroplating solution is 0.005 mol / L to 0.1 mol / L, and the concentration of nickel ions is 0.005 mol / L to 0.4 mol / L.

[0012] In one embodiment, the first electroplating solution further contains a first conductive salt, which includes at least one of KCl, NaCl, Na2SO4, and K2SO4.

[0013] In one embodiment, the concentration of total metal ions in the first electroplating solution is 0.01 mol / L to 0.5 mol / L.

[0014] In one embodiment, the concentration of the polytetrafluoroethylene is 10 g / L to 20 g / L.

[0015] In one embodiment, during the first electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the Ag / AgCl reference electrode.

[0016] In one embodiment, the deposition time of the first electrodeposition treatment is 300s to 1200s.

[0017] In one embodiment, the thickness of the first catalyst layer is 0.2 μm to 2 μm.

[0018] In one embodiment, prior to the first electrodeposition process, the preparation method further includes the following steps:

[0019] The conductive substrate is placed in a second electroplating solution for a second electrodeposition treatment. The second electroplating solution contains a second ferrous salt and a second nickel salt, but does not contain polytetrafluoroethylene. A second catalytic layer is deposited on the conductive substrate, and the second catalytic layer is located between the conductive substrate and the first catalytic layer.

[0020] In one embodiment, the second ferrous salt includes at least one of FeCl2, FeSO4, and Fe(NO3)2.

[0021] In one embodiment, the second nickel salt includes at least one of NiCl2, NiSO4, and Ni(NO3)2.

[0022] In one embodiment, the concentration of ferrous ions in the second electroplating solution is 0.005 mol / L to 0.1 mol / L, and the concentration of nickel ions is 0.005 mol / L to 0.4 mol / L.

[0023] In one embodiment, the second electroplating solution further contains a second conductive salt, which includes at least one of KCl, NaCl, Na2SO4, and K2SO4.

[0024] In one embodiment, the concentration of total metal ions in the second electroplating solution is 0.01 mol / L to 0.5 mol / L.

[0025] In one embodiment, during the second electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the reference electrode.

[0026] In one embodiment, the deposition time for the second electrodeposition process is 20s to 60s.

[0027] In one embodiment, the thickness of the second catalyst layer is 20 nm to 100 nm.

[0028] A NiFe-LDH oxygen evolution electrode is prepared by the preparation method described in any of the above embodiments.

[0029] Compared with traditional technologies, the beneficial effects of this application are as follows:

[0030] The method for preparing the NiFe-LDH oxygen evolution electrode provided in this application involves electrodepositing a conductive substrate in an electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene (PTFE) to form a first catalyst layer. The first catalyst layer has a heterogeneous surface composed of hydrophilic catalyst active centers and dispersed hydrophobic PTFE sites. Oxygen bubbles preferentially adsorb, polymerize, and rapidly desorb at the hydrophobic sites, avoiding pinning at the hydrophilic active sites. This significantly reduces the average desorption diameter of the bubbles, shortens their residence time, improves mass transfer efficiency, and eliminates the bubble shielding effect. PTFE possesses high molecular flexibility and excellent chemical stability. Introducing it into the brittle metal hydroxide catalyst layer can act as a stress buffer, effectively dissipating the impact and shear stress generated by bubble scouring, inhibiting the generation and propagation of microcracks in the catalyst layer, enhancing the bonding strength between the catalyst layer and the conductive substrate, and within the catalyst layer itself. This significantly improves the mechanical stability and service life of the NiFe-LDH oxygen evolution electrode under high current impact. Detailed Implementation

[0031] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] The method for preparing a NiFe-LDH oxygen evolution electrode according to an embodiment of this application includes the following steps:

[0035] Using a conductive substrate as the working electrode, a first electrodeposition process is performed in a first electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene, thereby depositing a first catalyst layer on the conductive substrate.

[0036] Under the influence of an electric field, a hydrogen evolution reaction occurs on the surface of the conductive substrate, consuming H₂. + Or generate OH - This causes a rapid increase in the pH value of the micro-region at the electrode-solution interface. When the micro-region pH value reaches the precipitation threshold of metal hydroxide, the metal ions undergo hydrolysis and precipitation. Simultaneously, polytetrafluoroethylene migrates to the electrode surface under the influence of electric field force or adsorption force, is captured in situ, and deposits synchronously with the metal hydroxide.

[0037] The aforementioned method for preparing the NiFe-LDH oxygen evolution electrode involves electrodepositing a conductive substrate in an electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene (PTFE) to form a first catalytic layer. The first catalytic layer has a heterogeneous surface composed of hydrophilic catalyst active centers and dispersed hydrophobic PTFE sites. Oxygen bubbles preferentially adsorb, polymerize, and rapidly desorb at the hydrophobic sites, avoiding pinning at the hydrophilic active sites. This significantly reduces the average desorption diameter of the bubbles, shortens their residence time, improves mass transfer efficiency, and eliminates the bubble shielding effect.

[0038] Polytetrafluoroethylene (PTFE) possesses high molecular flexibility and excellent chemical stability. Introducing it into a brittle metal hydroxide catalyst layer can act as a stress buffer, effectively dissipating the impact and shear stress generated by bubble erosion, inhibiting the generation and propagation of microcracks in the catalyst layer, enhancing the bonding strength between the catalyst layer and the conductive substrate, and between the catalyst layer itself, and significantly improving the mechanical stability and service life of the electrode under high current impact.

[0039] Optionally, the conductive substrate is at least one of nickel foam, nickel mesh, nickel felt, and stainless steel mesh. In some examples, the conductive substrate is nickel foam. Nickel foam has a three-dimensional interconnected porous structure, a large specific surface area, excellent conductivity, and moderate mechanical strength, making it suitable as a conductive framework for self-supporting electrodes.

[0040] In some of these examples, the conductive substrate is pretreated before electrodeposition to remove oil, oxide layers, impurities, and burrs from its surface, ensuring a clean and activated substrate surface that facilitates the uniform and robust deposition of the subsequent catalytic layer.

[0041] In some of these examples, preprocessing includes the following steps:

[0042] The conductive substrate is ultrasonically cleaned in an organic solvent to remove surface grease and other organic impurities. Organic solvents include, but are not limited to, acetone and ethanol. For example, the conductive substrate is ultrasonically cleaned sequentially in acetone and ethanol. Subsequently, the conductive substrate is ultrasonically cleaned in a hydrochloric acid solution to remove the surface oxide layer and inorganic impurities. It is then rinsed with deionized water until neutral and dried for later use.

[0043] In some examples, a three-electrode electrolysis system is constructed in the first electrodeposition process, with a conductive substrate as the working electrode and the counter electrode being, but not limited to, nickel foam, nickel metal plate, etc. Using the aforementioned counter electrode allows for the replenishment of nickel ions to the electroplating solution during the electroplating process. The reference electrode can be, but is not limited to, a silver / silver chloride (Ag / AgCl) electrode. The working electrode, counter electrode, and reference electrode are placed together in the first electroplating solution for the first electrodeposition process, depositing a first catalyst layer on the surface of the conductive substrate.

[0044] In some examples, during the first electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the reference electrode. Further, the potential of the working electrode is -0.9V to -1.0V relative to the reference electrode. In some specific examples, the potential of the working electrode is -0.8V, -0.85V, -0.9V, -0.95V, -1.0V, -1.05V, -1.1V, etc., relative to the reference electrode. Within this potential range, metal ions can stably undergo hydrolysis and precipitation, forming a first catalyst layer with moderate crystallinity, uniform morphology, and strong bonding.

[0045] Optionally, in the first electroplating solution, the first ferrous salt includes, but is not limited to, at least one of FeCl2, FeSO4, and Fe(NO3)2. The first nickel salt includes, but is not limited to, at least one of NiCl2, NiSO4, and Ni(NO3)2.

[0046] In some examples, polytetrafluoroethylene (PTFE) is first prepared as an emulsion and then added to the electroplating solution, which improves the dispersibility of PTFE in the first electroplating solution. In some examples, the solid content of the PTFE emulsion is 50% to 70%, specifically, for example, 50%, 55%, 60%, 65%, 70%, etc.

[0047] In some of these examples, the concentration of ferrous ions in the first electroplating solution is 0.005 mol / L to 0.1 mol / L, specifically, for example, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, etc.

[0048] In some of these examples, the concentration of nickel ions in the first electroplating solution is 0.005 mol / L to 0.4 mol / L, specifically, for example, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, etc.

[0049] In some of these examples, the first electroplating solution also includes a first conductive salt to provide sufficient free ions, significantly improving the conductivity of the electroplating solution and ensuring the uniform and stable conduction of the electrodeposition process.

[0050] Optionally, the first conductive salt may include, but is not limited to, at least one of KCl, NaCl, Na₂SO₄, and K₂SO₄. In some examples, the concentration of the first conductive salt is 0.1 mol / L to 0.5 mol / L, specifically, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0051] In some examples, the concentration of total metal ions in the first electroplating solution is 0.01 mol / L to 0.5 mol / L. Further, the concentration of total metal ions in the first electroplating solution is 0.1 mol / L to 0.4 mol / L. In some specific examples, the concentration of total metal ions in the first electroplating solution is 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0052] In some examples, the concentration of polytetrafluoroethylene (PTFE) in the first electroplating solution is 5 g / L to 50 g / L. More specifically, the concentration of PTFE is 12 g / L to 18 g / L. Within this concentration range, the PTFE content is moderate, avoiding excessive coverage of catalytic active sites and ensuring sufficient catalytic reaction active centers. Simultaneously, the hydrophobic sites can rapidly guide bubble desorption, eliminating the bubble shielding effect and achieving a synergistic improvement in catalytic activity and mass transfer efficiency. In some specific examples, the PTFE concentration is 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, etc.

[0053] In some examples, the deposition time for the first electrodeposition treatment is 300 s to 1800 s. Further, the deposition time for the first electrodeposition treatment is 500 s to 1000 s. In some specific examples, the deposition time for the first electrodeposition treatment is 300 s, 400 s, 500 s, 600 s, 700 s, 800 s, 900 s, 1000 s, 1100 s, 1200 s, 1300 s, 1400 s, 1500 s, 1600 s, 1700 s, 1800 s, etc.

[0054] In some examples, the temperature of the first electrodeposition treatment is 20°C to 60°C. Further, the temperature of the first electrodeposition treatment is 30°C to 50°C. In some specific examples, the temperature of the first electrodeposition treatment is 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0055] In some examples, the first electrolyte is subjected to ultrasonic treatment during the first electrodeposition process. This allows the polytetrafluoroethylene (PTFE) to be evenly dispersed in the first electrolyte, preventing PTFE agglomeration and sedimentation, and improving deposition uniformity.

[0056] In some examples, the thickness of the first catalyst layer is 0.2 μm to 2 μm, specifically 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, etc.

[0057] In some of these examples, the following steps are included prior to the first electrodeposition process:

[0058] A conductive substrate is placed in a second electroplating solution for a second electrodeposition treatment. The second electroplating solution contains a second ferrous salt and a second nickel salt, but does not contain polytetrafluoroethylene. A second catalytic layer is deposited on the conductive substrate, and the second catalytic layer is located between the conductive substrate and the first catalytic layer.

[0059] Studies have found that polytetrafluoroethylene (PTFE) deposited at the interface between the conductive substrate and the catalyst layer reduces electron conduction efficiency and degrades electrode performance. In the example above, a second catalyst layer free of PTFE is deposited on the surface of the conductive substrate before the first electrodeposition treatment. This avoids PTFE distribution in the interface region between the conductive substrate and the catalyst, eliminates insulation barriers, and improves the electrical contact and electron conduction efficiency between the conductive substrate and the catalyst. Consequently, the electrode simultaneously possesses high catalytic activity, low impedance, excellent mechanical stability, and rapid mass transfer capability.

[0060] In some examples, a three-electrode electrolysis system is constructed in the second electrodeposition process. A conductive substrate serves as the working electrode, and the counter electrode can be, for example, but is not limited to, nickel foam or a nickel metal plate. Using this counter electrode allows for the replenishment of nickel ions to the electroplating solution during the electroplating process. The reference electrode can be, but is not limited to, a silver / silver chloride (Ag / AgCl) electrode. The working electrode, counter electrode, and reference electrode are placed together in the second electroplating solution for the second electrodeposition process, depositing a second catalyst layer on the surface of the conductive substrate.

[0061] In some examples, during the second electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the reference electrode. Further, the potential of the working electrode is -0.9V to -1.0V relative to the reference electrode. In some specific examples, the potential of the working electrode is -0.8V, -0.85V, -0.9V, -0.95V, -1.0V, -1.05V, -1.1V, etc., relative to the reference electrode. Within this potential range, metal ions can stably undergo hydrolysis and precipitation, forming a second catalyst layer with moderate crystallinity, uniform morphology, and strong bonding.

[0062] Optionally, in the second electroplating solution, the second ferrous salt includes, but is not limited to, at least one of FeCl2, FeSO4, and Fe(NO3)2. The second nickel salt includes, but is not limited to, at least one of NiCl2, NiSO4, and Ni(NO3)2.

[0063] In some examples, the concentration of ferrous ions in the second electroplating solution is 0.005 mol / L to 0.1 mol / L, specifically, for example, 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, etc.

[0064] In some examples, the concentration of nickel ions in the second electroplating solution is 0.005 mol / L to 0.4 mol / L, specifically 0.005 mol / L, 0.01 mol / L, 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, etc.

[0065] In some of these examples, the second electroplating solution also includes a second conductive salt to provide sufficient free ions, significantly improving the conductivity of the electroplating solution and ensuring the uniform and stable conduction of the electrodeposition process.

[0066] Optionally, the second conductive salt may include, but is not limited to, at least one of KCl, NaCl, Na₂SO₄, and K₂SO₄. In some examples, the concentration of the second conductive salt is 0.1 mol / L to 0.5 mol / L, specifically, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0067] In some examples, the concentration of total metal ions in the second electroplating solution is 0.01 mol / L to 0.5 mol / L. Further, the concentration of total metal ions in the second electroplating solution is 0.1 mol / L to 0.4 mol / L. In some specific examples, the concentration of total metal ions in the second electroplating solution is 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc.

[0068] In some examples, the deposition time for the second electrodeposition treatment is 20 s to 60 s. Further, the deposition time for the second electrodeposition treatment is 30 s to 50 s. In some specific examples, the deposition time for the second electrodeposition treatment is 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, etc.

[0069] In some examples, the temperature of the second electrodeposition process is 20°C to 60°C. Further, the temperature of the second electrodeposition process is 30°C to 50°C. In some specific examples, the temperature of the second electrodeposition process is 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0070] In some examples, the thickness of the second catalyst layer is 20nm to 100nm, specifically 20nm, 40nm, 60nm, 80nm, 100nm, etc.

[0071] Furthermore, this application also provides a NiFe-LDH oxygen evolution electrode, which is prepared by any of the preparation methods described above.

[0072] The following specific embodiments further illustrate the present invention. These specific embodiments are provided to better understand the present invention, but are not intended to limit the scope of the invention and do not constitute a limitation on its content or protection.

[0073] Example 1

[0074] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0075] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0076] Step 2: Conductive substrate electrodeposition treatment. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being a nickel metal sheet, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentrations of ferrous ions were 0.05 mol / L, nickel ions were 0.2 mol / L, potassium ions were 0.25 mol / L, and polytetrafluoroethylene was 10 g / L. The potential of the working electrode was -0.9 V vs Ag / AgCl. The electrodeposition treatment took 600 s, depositing a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene on the conductive substrate, with a thickness of approximately 0.75 μm, thus obtaining the NiFe-LDH oxygen evolution electrode.

[0077] Example 2

[0078] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0079] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0080] Step 2: Conductive substrate electrodeposition treatment. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being nickel foam, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentrations of ferrous ions were 0.02 mol / L, nickel ions were 0.08 mol / L, potassium ions were 0.4 mol / L, and polytetrafluoroethylene was 20 g / L. The potential of the working electrode was -1.1 V vs Ag / AgCl. The electrodeposition treatment took 1800 s, depositing a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene on the conductive substrate, with a thickness of approximately 2 μm, resulting in a NiFe-LDH oxygen evolution electrode.

[0081] Example 3

[0082] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0083] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0084] Step 2: The first step of electrodeposition on the conductive substrate. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being nickel foam, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, and KCl. In the electroplating solution, the concentrations of ferrous ions were 0.1 mol / L, nickel ions were 0.3 mol / L, and potassium ions were 0.1 mol / L. The potential of the working electrode was -0.8 V vs Ag / AgCl. The electrodeposition time was 30 s, resulting in the deposition of an iron-nickel hydroxide on the conductive substrate with a thickness of approximately 50 nm.

[0085] Step 3: The second electrodeposition treatment of the conductive substrate. The three-electrode electrolysis system is the same as in Step 2. The electroplating solution is a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentration of ferrous ions is 0.1 mol / L, the concentration of nickel ions is 0.3 mol / L, the concentration of potassium ions is 0.1 mol / L, and the concentration of polytetrafluoroethylene is 10 g / L. The potential of the working electrode is -0.8 V vs Ag / AgCl. The deposition time of the electrodeposition treatment is 1200 s, and a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene is deposited on the conductive substrate, with a thickness of about 1.5 μm, to obtain the NiFe-LDH oxygen evolution electrode.

[0086] Example 4

[0087] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0088] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0089] Step 2: The first step of electrodeposition on the conductive substrate. A three-electrode electrolytic system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being a nickel metal sheet, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, and KCl. In the electroplating solution, the concentrations of ferrous ions were 0.05 mol / L, nickel ions were 0.15 mol / L, and potassium ions were 0.3 mol / L. The potential of the working electrode was -1.05 V vs Ag / AgCl. The electrodeposition time was 60 s, resulting in the deposition of an iron-nickel hydroxide on the conductive substrate with a thickness of approximately 100 nm.

[0090] Step 3: The second electrodeposition treatment of the conductive substrate. The three-electrode electrolysis system is the same as in Step 2. The electroplating solution is a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentration of ferrous ions is 0.05 mol / L, the concentration of nickel ions is 0.15 mol / L, the concentration of potassium ions is 0.3 mol / L, and the concentration of polytetrafluoroethylene is 20 g / L. The potential of the working electrode is -1.05 V vs Ag / AgCl. The deposition time of the electrodeposition treatment is 600 s, and a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene is deposited on the conductive substrate with a thickness of approximately 0.75 μm, resulting in the NiFe-LDH oxygen evolution electrode.

[0091] Example 5

[0092] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0093] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0094] Step 2: The first step of electrodeposition on the conductive substrate. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being a nickel metal sheet, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, and KCl. In the electroplating solution, the concentrations of ferrous ions were 0.01 mol / L, nickel ions were 0.04 mol / L, and potassium ions were 0.45 mol / L. The potential of the working electrode was -0.95 V vs Ag / AgCl. The electrodeposition time was 20 s, resulting in the deposition of an iron-nickel hydroxide on the conductive substrate with a thickness of approximately 20 nm.

[0095] Step 3: The second electrodeposition treatment of the conductive substrate. The three-electrode electrolysis system is the same as in Step 2. The electroplating solution is a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentration of ferrous ions is 0.01 mol / L, the concentration of nickel ions is 0.04 mol / L, the concentration of potassium ions is 0.45 mol / L, and the concentration of polytetrafluoroethylene is 50 g / L. The potential of the working electrode is -0.95 V vs Ag / AgCl. The deposition time of the electrodeposition treatment is 300 s, and a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene is deposited on the conductive substrate, with a thickness of about 0.5 μm, to obtain the NiFe-LDH oxygen evolution electrode.

[0096] Example 6

[0097] This embodiment provides a method for preparing a NiFe-LDH oxygen evolution electrode, including the following steps:

[0098] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0099] Step 2: The first step of electrodeposition on the conductive substrate. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being a nickel metal sheet, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, and KCl. In the electroplating solution, the concentrations of ferrous ions were 0.05 mol / L, nickel ions were 0.25 mol / L, and potassium ions were 0.2 mol / L. The potential of the working electrode was -0.9 V vs Ag / AgCl. The electrodeposition time was 40 s, resulting in the deposition of an iron-nickel hydroxide on the conductive substrate with a thickness of approximately 60 nm.

[0100] Step 3: The second electrodeposition treatment of the conductive substrate. The three-electrode electrolysis system is the same as in Step 2. The electroplating solution is a mixed aqueous solution of FeCl2, NiCl2, KCl, and polytetrafluoroethylene. In the electroplating solution, the concentration of ferrous ions is 0.05 mol / L, the concentration of nickel ions is 0.25 mol / L, the concentration of potassium ions is 0.2 mol / L, and the concentration of polytetrafluoroethylene is 5 g / L. The potential of the working electrode is -0.9 V vs Ag / AgCl. The deposition time of the electrodeposition treatment is 1200 s, and a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene is deposited on the conductive substrate, with a thickness of about 1.5 μm, to obtain the NiFe-LDH oxygen evolution electrode.

[0101] Comparative Example 1

[0102] The preparation method of the NiFe-LDH oxygen evolution electrode in this comparative example includes the following steps:

[0103] Step 1, Conductive substrate pretreatment. Nickel foam was selected as the conductive substrate and ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 15 minutes each to remove oil stains. Then, it was ultrasonically cleaned with dilute hydrochloric acid for 10 minutes to remove the oxide layer. Finally, it was rinsed with deionized water until neutral and dried at room temperature for later use.

[0104] Step 2: Conductive substrate electrodeposition treatment. A three-electrode electrolysis system was constructed, with the working electrode being the conductive substrate obtained in Step 1, the counter electrode being a graphite rod, and the reference electrode being an Ag / AgCl electrode. The electroplating solution was a mixed aqueous solution of FeCl2, NiCl2, and KCl. In the electroplating solution, the concentration of ferrous ions was 0.05 mol / L, the concentration of nickel ions was 0.2 mol / L, and the concentration of potassium ions was 0.25 mol / L. The potential of the working electrode was -0.9 V vs Ag / AgCl. The electrodeposition treatment took 600 s, depositing a catalyst layer containing iron-nickel hydroxide and polytetrafluoroethylene on the conductive substrate, with a thickness of approximately 0.5 μm, thus obtaining the NiFe-LDH oxygen evolution electrode.

[0105] The only difference between this comparative example and Example 1 is that polytetrafluoroethylene was not added to the electroplating solution.

[0106] The performance of the NiFe-LDH oxygen evolution electrodes prepared in the above embodiments and comparative examples was tested. The performance testing methods are as follows:

[0107] Using the NiFe-LDH oxygen evolution electrode provided in the above embodiments and comparative examples as the working electrode, a carbon rod as the counter electrode, Hg / HgO as the reference electrode, 1 mol / L KOH as the reaction medium, and a test temperature of 25°C, the electrode reached 100 mA / cm² as determined by CV testing. 2 The required oxygen evolution overpotential and Tafel slope at the specified current density were obtained by chronopotentialization at 500 mA / cm². 2 The potential decay rate under long-term operation at current density was measured by recording and measuring the average desorption diameter of bubbles during the reaction process using high-speed imaging. The test results are shown in Table 1.

[0108] Table 1

[0109]

[0110] As shown in Table 1, compared with Comparative Example 1, the NiFe-LDH oxygen evolution electrodes prepared in Examples 1-6 of this application have improved in terms of catalytic activity, bubble desorption effect and long-term operational stability.

[0111] The NiFe-LDH oxygen evolution electrodes prepared in Examples 1-6 of this application have oxygen evolution overpotentials of 239 mV to 258 mV and Tafel slopes of 33.2 mV / dec to 36.7 mV / dec, both lower than those of Comparative Example 1 (292 mV and 46.3 mV / dec). This indicates that the introduction of a polytetrafluoroethylene (PTFE) catalyst layer can effectively improve the oxygen evolution catalytic activity and reaction kinetics of the electrode. Among them, Examples 3-6, which employ a double-layer catalyst layer structure, exhibit even better performance, with overpotentials further reduced to 239 mV to 247 mV and Tafel slopes as low as 33.2 mV / dec to 35.8 mV / dec. This demonstrates that depositing a bottom catalyst layer without PTFE first can eliminate interfacial insulation barriers, optimize electron conduction efficiency, and thus further improve the electrode's catalytic performance.

[0112] The NiFe-LDH oxygen evolution electrodes prepared in Examples 1-6 of this application have an average bubble desorption diameter of 37.2 μm to 42.8 μm, which is significantly smaller than the 102.6 μm of Comparative Example 1. This indicates that the hydrophobic polytetrafluoroethylene sites dispersed in the catalyst layer can guide bubbles to preferentially adsorb, polymerize, and rapidly desorb at the hydrophobic sites, significantly reducing the average bubble desorption diameter, shortening the bubble residence time, effectively mitigating the bubble shielding effect, and improving mass transfer efficiency; and effectively preventing mechanical damage to the electrode structure caused by the rupture of large bubbles.

[0113] The NiFe-LDH oxygen evolution electrodes prepared in Examples 1-6 of this application, at 500 mA / cm², 2 The potential decay rate under high current density is 0.029 mV / h to 0.034 mV / h, which is significantly lower than the 0.276 mV / h of Comparative Example 1. This indicates that the introduction of polytetrafluoroethylene (PTFE) can play a stress buffering role, effectively dissipating the impact and shear stress generated by bubble erosion, inhibiting the generation and propagation of microcracks in the catalyst layer, enhancing the bonding strength between the catalyst layer and the conductive substrate, and significantly improving the mechanical stability and service life of the electrode under high current impact.

[0114] In summary, the method for preparing the NiFe-LDH oxygen evolution electrode provided in this application introduces polytetrafluoroethylene during the electrodeposition process to construct a catalytic layer with a hydrophilic-hydrophobic heterogeneous surface, and further optimizes it into a bilayer catalytic layer structure. This method achieves high catalytic activity, rapid bubble desorption, and excellent long-term operational stability, and can meet the long-term operational requirements of industrial alkaline water electrolysis for hydrogen production under high current density.

[0115] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a NiFe-LDH oxygen evolution electrode, characterized in that, Includes the following steps: Using a conductive substrate as the working electrode, a first electrodeposition process is performed in a first electroplating solution containing a first ferrous salt, a first nickel salt, and polytetrafluoroethylene, thereby depositing a first catalytic layer on the conductive substrate.

2. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 1, characterized in that, It meets at least one of the following characteristics (1) to (3): (1) The conductive substrate is at least one of nickel foam, nickel mesh, nickel felt and stainless steel mesh; (2) The first ferrous salt includes at least one of FeCl2, FeSO4, and Fe(NO3)2; (3) The first nickel salt includes at least one of NiCl2, NiSO4, and Ni(NO3)2.

3. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 1, characterized in that, It meets at least one of the following characteristics (1) to (4): (1) In the first electroplating solution, the concentration of ferrous ions is 0.005 mol / L to 0.1 mol / L, and the concentration of nickel ions is 0.005 mol / L to 0.4 mol / L; (2) The first electroplating solution also contains a first conductive salt, which includes at least one of KCl, NaCl, Na2SO4, and K2SO4; (3) The concentration of total metal ions in the first electroplating solution is 0.01 mol / L to 0.5 mol / L; (4) The concentration of the polytetrafluoroethylene is 5 g / L to 50 g / L.

4. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 1, characterized in that, In the first electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the Ag / AgCl reference electrode.

5. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 1, characterized in that, It meets at least one of the following characteristics (1) to (2): (1) The deposition time of the first electrodeposition treatment is 300s~1800s; (2) The thickness of the first catalyst layer is 0.2μm~2μm.

6. The method for preparing the NiFe-LDH oxygen evolution electrode according to any one of claims 1 to 5, characterized in that, Prior to the first electrodeposition process, the preparation method further includes the following steps: The conductive substrate is placed in a second electroplating solution for a second electrodeposition treatment. The second electroplating solution contains a second ferrous salt and a second nickel salt, but does not contain polytetrafluoroethylene. A second catalytic layer is deposited on the conductive substrate, and the second catalytic layer is located between the conductive substrate and the first catalytic layer.

7. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 6, characterized in that, It meets at least one of the following characteristics (1) to (2): (1) The second ferrous salt includes at least one of FeCl2, FeSO4, and Fe(NO3)2; (2) The second nickel salt includes at least one of NiCl2, NiSO4, and Ni(NO3)2.

8. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 6, characterized in that, It meets at least one of the following characteristics (1) to (3): (1) In the second electroplating solution, the concentration of ferrous ions is 0.005 mol / L to 0.1 mol / L, and the concentration of nickel ions is 0.005 mol / L to 0.4 mol / L; (2) The second electroplating solution also contains a second conductive salt, which includes at least one of KCl, NaCl, Na2SO4, and K2SO4; (3) The concentration of total metal ions in the second electroplating solution is 0.01 mol / L to 0.5 mol / L.

9. The method for preparing the NiFe-LDH oxygen evolution electrode as described in claim 6, characterized in that, It meets at least one of the following characteristics (1) to (3): (1) In the second electrodeposition process, the potential of the working electrode is -0.8V to -1.1V relative to the reference electrode; (2) The deposition time for the second electrodeposition treatment is 20s~60s; (3) The thickness of the second catalyst layer is 20nm~100nm.

10. A NiFe-LDH oxygen evolution electrode, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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