A nickel-based self-supporting electrode for electrolysis of water to evolve oxygen and a preparation method and applications thereof

Abstract

The application discloses a nickel-based self-supporting electrode for water electrolysis oxygen evolution, a preparation method and application thereof, and belongs to the technical field of electrocatalytic materials. A three-dimensional porous nickel fiber felt is used as a conductive substrate, and a nickel-doped hydroxyl iron oxide (Ni-FeOOH) is in-situ grown on the surface of the three-dimensional porous nickel fiber felt through a low-temperature co-deposition method, so that a three-dimensional hierarchical porous structure is formed. The application innovatively uses an oxidizing gas to oxidize ferrous ions into ferric ions, etches the nickel felt substrate to make nickel ions dissolve out and participate in co-deposition, and realizes strong combination between the catalyst and the substrate. The preparation method is simple in process, low in cost and easy for large-scale production. The obtained electrode exhibits excellent oxygen evolution activity and durability in an alkaline electrolyte, and can be stably operated for more than 1000 hours under a current density of 5000 A m ‑2 at 95 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy materials technology, specifically relating to a highly efficient, stable and low-cost self-supporting anode material for alkaline water electrolysis oxygen evolution reaction (OER), and in particular an electrode with a nickel-doped iron hydroxyl oxide (Ni-FeOOH) catalytic layer grown in situ on a three-dimensional porous nickel fiber felt substrate, its preparation method and application. Background Technology

[0002] Hydrogen energy is a clean and efficient secondary energy source, and using renewable energy to produce hydrogen through water electrolysis is currently the most promising green hydrogen production technology. However, the slow kinetics and high overpotential of the oxygen evolution reaction (OER) at the anode during water electrolysis have become a key bottleneck restricting the overall energy efficiency improvement of water electrolysis.

[0003] Currently, commercial OER catalysts mainly use nickel-based conductive materials such as nickel felt and nickel mesh. While these materials offer cost advantages, their OER catalytic activity is generally low. For example, at a current density of 5000 A / m², the overpotential is typically higher than 300 mV, leading to a significant increase in energy consumption during the water electrolysis hydrogen production process. Therefore, developing efficient, stable, and non-precious metal-based OER catalysts is particularly crucial.

[0004] Nickel-doped iron hydroxyl oxide (Ni-FeOOH), as a modified material with FeOOH as the main structural component, has become a highly promising and efficient non-noble metal OER catalyst under alkaline conditions due to the effective modulation of the electronic structure of the iron active center by nickel doping and the synergistic catalytic effect between the two. However, traditional powdered Ni-FeOOH catalysts require polymer binders (such as Nafion) to be fixed on the surface of the current collector in practical applications, which has the following inherent drawbacks:

[0005] (1) Poor conductivity: The binder is mostly an insulating material, which will increase the electrode interface resistance;

[0006] (2) Active sites are masked: Binders can easily cover part of the catalytic active sites, reducing catalyst utilization;

[0007] (3) Insufficient stability: During the violent oxygen evolution process, the impact of bubbles can easily cause the catalyst powder to fall off from the current collector, resulting in performance degradation.

[0008] Although there are reports of growing Ni-FeOOH on nickel foam (a three-dimensional porous material) in existing technologies, nickel foam is usually quite thick (1-10 mm), making it difficult to directly match with existing commercial electrolyzers. Furthermore, it is costly and has poor mechanical stability, and currently, most studies remain limited to laboratory research. While nickel mesh is inexpensive, its limited specific surface area severely restricts further improvements in electrode performance. Nickel felt, as a three-dimensional porous network material formed by the disordered stacking of metallic nickel fibers, possesses higher porosity, larger specific surface area, and better mechanical toughness; however, research and practical applications of using it as a substrate to construct FeOOH-based oxygen evolution electrodes are still insufficient. In addition, current literature reports on electrode catalyst performance evaluations are mostly conducted under 1 M KOH and 25 °C conditions, which differ significantly from actual industrial operating conditions (such as 30% KOH and 95 °C), making it difficult to directly guide the structural design and optimization of electrodes in industrial electrolyzers. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention aims to provide a self-supporting electrode for the oxygen evolution reaction in water electrolysis, its preparation method, and its application. This method features a simple process, and the prepared self-supporting electrode exhibits advantages such as high catalytic activity, excellent stability, and low cost.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a self-supporting electrode for the oxygen evolution reaction of water electrolysis, comprising: a three-dimensional porous nickel fiber felt conductive substrate; a nickel-doped iron hydroxyl oxide catalytic layer grown in situ on the surface of the nickel fiber felt; the catalytic layer is assembled into a cluster structure by nanorods, which together with the nickel fiber felt substrate constitute a three-dimensional hierarchical porous conductive network.

[0012] Furthermore, the three-dimensional hierarchical porous conductive network comprises: macroscopic pores formed by a nickel fiber felt skeleton, micrometer-scale pores formed between nanorod clusters, and nanoscale pores formed between nanorods. The macroscopic pores have a size of tens to hundreds of micrometers, provided by the three-dimensional network structure of the nickel fiber felt itself; the micrometer-scale pores have a size of hundreds to several micrometers, formed by gaps between adjacent nanorod clusters; and the nanoscale pores have a size of tens of nanometers, formed by gaps between nanorods within a single cluster. This multi-scale hierarchical porous structure facilitates electrolyte permeation and bubble escape, thereby improving the mass transfer efficiency and catalytic performance of the electrode.

[0013] Furthermore, the clustered structure is hill-shaped.

[0014] Furthermore, the molar ratio of nickel to iron in the nickel-doped iron hydroxyoxide is 1:2 to 2:1.

[0015] Secondly, the present invention provides a method for preparing the above-mentioned self-supporting electrode, comprising the following steps:

[0016] (a) Provide a nickel fiber felt substrate and pretreat it to clean its surface;

[0017] (b) Dissolve nickel salt, ferrous salt and urea in deionized water and stir to form a homogeneous solution; wherein the nickel salt is nickel chloride and the ferrous salt is ferrous chloride; the nickel chloride and ferrous chloride include their hydrated forms;

[0018] (c) Immerse the substrate treated in step (a) into the solution in step (b) and react at 30-50°C for 12-48 hours under continuous oxidizing gas; the oxidizing gas is used to oxidize ferrous ions to ferric ions, and the ferric ions etch the surface of the nickel fiber felt to dissolve nickel ions and participate in the co-deposition of nickel-doped iron hydroxyl oxide.

[0019] (d) After the reaction is complete, the product is removed, washed and dried to obtain the self-supporting electrode.

[0020] Further, in step (b), the concentration of nickel ions in the solution is 0.05-0.2 mol / L, the concentration of ferrous ions is 0.05-0.1 mol / L, and the concentration of urea is 0.1-0.5 mol / L.

[0021] Further, in step (c), the oxidizing gas is air or oxygen.

[0022] Further, the pretreatment in step (a) includes: ultrasonically cleaning the nickel fiber felt sequentially with an organic solvent, an acid solution, and deionized water. The organic solvent can be ethanol or an industrial cleaning agent, used to remove surface oil; the acid solution can be dilute hydrochloric acid, used to remove surface oxides.

[0023] Further, in step (d), the washing is repeated rinsing with deionized water or ultrasonic cleaning to remove impurity ions physically adsorbed on the surface; the drying temperature is 60-80℃ and the time is 6-12 hours.

[0024] Thirdly, the present invention provides an electrolytic water anode, which is composed of the above-mentioned self-supporting electrode.

[0025] Fourthly, the present invention provides a water electrolysis hydrogen production device, comprising an electrolytic cell, an anode and a cathode, wherein the anode is the aforementioned water electrolysis anode, the electrolyte in the electrolytic cell is a KOH solution with a concentration of 20-35 wt%, and the operating temperature is 60-95℃.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) Innovative substrate selection: The present invention uses nickel fiber felt as substrate, which has a larger specific surface area than the commonly used nickel mesh in industry, providing more catalyst loading sites and improving electrochemical activity; compared with the commonly seen nickel foam in the literature, nickel felt has higher mechanical strength and is easier to integrate with existing electrolytic cells.

[0028] (2) Unique preparation process: An "in-situ growth" strategy is adopted, using ferrous salt (ferrous chloride) as a precursor. Oxidizing gas is continuously introduced to slowly oxidize it to ferric iron, achieving controllable etching of the nickel felt substrate. This process promotes nickel ion dissolution, providing growth sites for Ni-FeOOH nanorods and enhancing the bonding force between the catalyst layer and the substrate. The introduction of urea can adjust the pH, stabilize the FeOOH structure, and promote chloride ion removal, facilitating subsequent cleaning. This method achieves in-situ growth of the catalyst on the surface of the nickel felt fiber, forming strong chemical bonds, avoiding the use of insulating binders, and ensuring efficient electron transport. Compared with common hydrothermal methods, this low-temperature liquid phase deposition method has milder conditions, lower energy consumption, and is easier to scale up to industrial scale.

[0029] (3) Unique three-dimensional hierarchical porous structure: The obtained electrode has a three-level pore structure, including macroscopic pores provided by the nickel felt skeleton, micron-level pores between nanorod clusters, and nano-level pores between nanorods, which is conducive to electrolyte penetration and bubble escape, and improves mass transfer efficiency.

[0030] (4) Integrated self-supporting structure: The prepared electrode can be used directly as a working electrode without coating, which simplifies the preparation process, reduces costs, and ensures the stability of the overall structure.

[0031] (5) High catalytic activity: The three-dimensional hierarchical porous structure provides a huge electrochemical active area; the highly conductive nickel felt substrate ensures rapid electron transport; the electronic synergistic effect between Ni and Fe optimizes the adsorption energy of OER intermediates and significantly reduces the oxygen evolution overpotential. The overpotential can be lower than 220 mV at 5000 A·m⁻².

[0032] (6) Excellent stability: The catalyst layer is firmly bonded to the substrate and is not easy to fall off. Under industrial conditions (95℃, 30% KOH) and high current density (5000 A·m⁻²) for a long time, the overpotential decay rate is <20 mV / 1000 h, and the stability is far superior to that of traditional coated electrodes.

[0033] (7) Low cost and easy to scale up: The raw materials (nickel chloride, ferrous chloride, urea) are inexpensive and readily available, and have a high utilization rate; the low-temperature co-deposition process is simple, easy to scale up production, and has good commercial application prospects. Attached Figure Description

[0034] Figure 1The X-ray diffraction (XRD) pattern of the nickel felt@Ni-FeOOH material prepared in Example 1 shows that the catalyst is mainly composed of FeOOH.

[0035] Figure 2 The image is a scanning electron microscope (SEM) image (low magnification) of the nickel felt@Ni-FeOOH material prepared in Example 1.

[0036] Figure 3 This is a scanning electron microscope (SEM) image (high magnification) of the nickel felt@Ni-FeOOH material prepared in Example 1.

[0037] Figure 4 The energy dispersive X-ray (EDS) spectrum of the nickel felt@Ni-FeOOH material prepared in Example 1 shows that Ni, Fe and O elements are uniformly distributed on the catalyst surface, indicating that Ni element exists on the catalyst surface.

[0038] Figure 5 The images show the high-resolution X-ray photoelectron (XPS) spectra of Fe 2p, Ni 2p, and O 1s in the nickel felt@Ni-FeOOH material prepared in Example 1. Ni is mainly represented by Ni2p. 2+ and Ni 3+ The presence of Ni in FeOOH and the absence of obvious nickel-based phases in the XRD pattern indicate that Ni was doped with FeOOH, and Ni-FeOOH was successfully synthesized.

[0039] Figure 6 The OER polarization curve of the electrode prepared in Example 1, measured in 1 M KOH solution at 25°C according to the national standard method, is compared with that of blank nickel felt and commercial nickel mesh anode, indicating that it has excellent catalytic activity.

[0040] Figure 7 The OER polarization curve of the electrode prepared in Example 1 was measured under industrial application conditions of 30% KOH solution and 95°C. Compared with blank nickel felt and commercial nickel mesh anode, it further proves its excellent catalytic activity.

[0041] Figure 8 The chronopotential curve, measured at a constant current density, demonstrates the electrode's excellent long-term stability.

[0042] Figure 9 The image shows a scanning electron microscope (SEM) image of the sample prepared in Comparative Example 4, revealing the three-dimensional porous structure of the nickel felt caused by the agglomeration of the catalyst due to the high concentration of the deposited liquid. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. All modifications and improvements made based on the concept of the present invention should fall within the scope of protection of the present invention.

[0044] The self-supporting electrode of this invention consists of a three-dimensional porous nickel fiber felt conductive substrate and a nickel-doped iron hydroxide (Ni-FeOOH) catalytic layer grown in situ on its surface. The nickel fiber felt is a three-dimensional porous network material formed by the disordered stacking of metallic nickel fibers. Unlike the skeleton-cavity structure of nickel foam, the nickel fiber felt has a higher specific surface area and better mechanical toughness.

[0045] The catalyst layer consists of strip-shaped nanorods assembled into a hill-like cluster structure, uniformly distributed on the surface of nickel fibers. Together with the nickel fiber felt substrate, the catalyst layer forms a three-dimensional hierarchical porous conductive network containing three levels of pores: the first level is the macroscopic pores (tens to hundreds of micrometers) formed by the nickel fiber felt skeleton; the second level is the micrometer-scale pores (hundreds of nanometers to several micrometers) formed between the nanorod clusters; and the third level is the nanometer-scale pores (tens of nanometers) formed between the nanorods.

[0046] The fabrication process of the self-supporting electrode described in this invention includes the following steps:

[0047] (1) Substrate pretreatment: The nickel fiber felt is ultrasonically cleaned in sequence with organic solvent, acid solution and deionized water to remove surface oil, oxides and other impurities, and then dried for later use.

[0048] (2) Preparation of reaction solution: Dissolve nickel chloride, ferrous chloride and urea in deionized water and stir until completely dissolved to form a homogeneous solution. The concentration of nickel ions is 0.05-0.2 mol / L, the concentration of ferrous ions is 0.05-0.1 mol / L, and the concentration of urea is 0.1-0.5 mol / L.

[0049] (3) Low-temperature co-deposition reaction: The pretreated nickel fiber felt is immersed in the above solution, and an oxidizing gas (air or oxygen) is continuously introduced at 30-50℃ for 12-48 hours. During this process, the oxidizing gas oxidizes the ferrous ions (Fe²⁺) in the solution to ferric ions (Fe³⁺). Fe³⁺ etches the surface of the nickel fiber felt, causing the nickel ions to dissolve. The dissolved nickel ions co-deposit with the nickel ions and iron ions in the solution in a weakly alkaline environment controlled by urea, forming a Ni-FeOOH catalyst layer that grows in situ on the surface of the nickel fiber.

[0050] (4) Post-processing: After the reaction is completed, the product is taken out, washed with deionized water to remove the impurity ions adsorbed on the surface, and dried at 60-80℃ for 6-12 hours to obtain the self-supporting electrode.

[0051] Example 1: Preparation and performance testing of nickel felt@Ni-FeOOH electrode

[0052] Material pretreatment:

[0053] Take a 90 cm × 90 cm three-dimensional porous nickel fiber felt and ultrasonically clean it for 30 min each in industrial cleaning agent, dilute hydrochloric acid (0.1 M), and deionized water to thoroughly remove surface oil, oxides, and other impurities. After cleaning, dry it in a 60℃ oven for 8 hours for later use.

[0054] Preparation of reaction solution:

[0055] Weigh out 2000 g (Provides Ni²⁺ concentration of approximately 0.035 mol / L), 2000 g (supply A solution of approximately 0.042 mol / L Fe and 500 g of urea (0.14 mol / L) was dissolved in 240 L of deionized water and stirred for 30 minutes using a circulating pump until completely dissolved, yielding a clear green reaction solution. This green color is characteristic of Fe²⁺.

[0056] Deposition reaction:

[0057] The pretreated nickel felt was immersed in the above reaction solution and placed in a 40°C constant temperature water bath for 24 hours. The reaction tank was equipped with a circulation pump to continuously introduce air into the solution to ensure sufficient dissolved oxygen. The introduced air, as an oxidizing gas, oxidizes the ferrous ions in the solution (…). ) is oxidized to ferric ions ( The generated It has oxidizing properties and can etch the surface of nickel fiber felt, causing nickel ions to dissolve. The dissolved nickel ions, together with the original nickel and iron ions in the solution, co-deposit in a weakly alkaline environment regulated by urea to form a Ni-FeOOH catalytic layer, which grows in situ on the surface of the nickel felt fiber.

[0058] Post-processing:

[0059] After the reaction, the sample was removed and ultrasonically cleaned with deionized water for 30 min to remove adsorbed ions from the surface. It was then dried in a vacuum oven at 70℃ for 8 hours, finally yielding an orange-red nickel felt@Ni-FeOOH composite electrode. Due to its high content of... The resulting electrode exhibits an orange-red color. This is significantly different in appearance from the common greenish Ni-Fe LDH material.

[0060] Structural characterization and performance testing:

[0061] Phase analysis ( Figure 1XRD patterns showed that the diffraction peaks at 2θ = 21.24°, 35.49°, 40.17°, 61.51°, and 77.94° could be attributed to FeOOH (PDF# 81-0464); similarly, the diffraction peaks at 27.08°, 36.94°, and 64.94° also belonged to FeOOH (PDF# 70-0714). These results indicate that the main phase of the catalyst synthesized in Example 1 is FeOOH.

[0062] Morphological analysis ( Figure 2 and Figure 3 ):from Figure 2 and Figure 3 The electrode exhibits a uniform, hill-like FeOOH cluster covering the surface of the nickel felt fibers, formed by the stacking of strip-shaped nanorods. These clusters form micrometer-scale pores, while the nanorods themselves form nanometer-scale pores. Together with the macroscopic pores of the nickel felt framework, these pores constitute a three-dimensional hierarchical porous structure. The electrode possesses this three-dimensional hierarchical porous structure: the first level consists of macroscopic pores (tens to hundreds of micrometers) formed by the nickel fiber felt framework; the second level consists of micrometer-scale pores (hundreds of nanometers to several micrometers) formed between the hill-shaped nanorod clusters; and the third level consists of nanometer-scale pores (tens of nanometers) formed between the nanorods within individual clusters. This hierarchical porous structure significantly increases the electrochemical active area and facilitates electrolyte penetration and bubble escape.

[0063] Surface elemental analysis ( Figure 4 and Figure 5 ) Figure 4 The presence of Ni, Fe, and O elements on the surface of the catalyst synthesized in Example 1 indicates that the catalyst contains Ni. Furthermore... Figure 5 The XPS spectra further confirmed the presence of Ni, and valence state analysis showed that almost no metallic (0 valence) nickel was detected, with Ni mainly present as... and The above results indicate that the Ni in the mapping does not entirely belong to the Ni felt substrate, but exists as a dopant in iron hydroxyl oxide (Ni-FeOOH).

[0064] Electrocatalytic activity ( Figure 6 This electrode exhibits excellent OER activity at 25°C and in 1 M KOH. At current density, its overpotential is only 274 mV, which is far superior to blank nickel felt (371 mV) and commercial nickel mesh anode (375 mV).

[0065] Industrial performance ( Figure 7 The performance advantages of this electrode are further amplified under harsh conditions of 95℃ and 30% KOH. The overpotential at current density is 217 mV, which is far superior to that of blank nickel felt (389 mV) and commercial nickel mesh anode (442 mV). This demonstrates its strong potential for industrial applications.

[0066] Stability test ( Figure 8 After operating continuously for 1000 hours at a high current density of 5000 A·m⁻², the electrode exhibits an overpotential decay of less than 18 mV (attenuation rate < 20 mV / 1000 h), demonstrating excellent long-term operational stability.

[0067] Example 2: Effect of different reaction times on electrode performance

[0068] This embodiment aims to investigate the effect of deposition reaction time on the microstructure and performance of the electrode. Except for extending the deposition reaction time from 24 hours to 48 hours, all other preparation parameters (including substrate pretreatment method, reaction solution composition, reaction temperature, etc.) are exactly the same as in Example 1.

[0069] After the reaction, the resulting electrode still exhibited a uniform orange-red color. Scanning electron microscopy (SEM) revealed that, compared to Example 1, extending the reaction time resulted in denser FeOOH nanorod clusters on the nickel felt surface, with a slight increase in nanorod size, leading to an overall increase in the thickness of the catalyst layer. This electrode also possesses a three-dimensional hierarchical porous structure, including macroscopic pores, micrometer-scale pores, and nanometer-scale pores. This thicker catalyst layer provides more active sites.

[0070] Electrochemical performance tests show that this electrode... The oxygen evolution overpotential at the current density was approximately 212 mV, comparable to that of Example 1 (217 mV), demonstrating excellent and stable high current density catalytic activity. More importantly, thanks to the thicker and more robustly bonded catalyst layer, the electrode exhibited superior mechanical stability and erosion resistance. In a test environment simulating the violent agitation of an industrial electrolyzer, the catalyst layer shedding rate was significantly lower than that of the sample after 24 hours of reaction, indicating its greater suitability for harsh industrial applications.

[0071] Example 3: Effect of different reaction temperatures on electrode performance

[0072] This embodiment aims to investigate the effect of reaction temperature on the deposition process. Except for increasing the deposition reaction temperature from 40°C to 50°C, the other steps are exactly the same as in Example 1.

[0073] At higher temperatures, the deposition reaction rate increases. The resulting electrode's catalytic layer nanorods exhibit better crystallinity, but the uniformity of the hill-like clusters decreases slightly. Electrochemical tests show that it... The overpotential was 225 mV, slightly higher than that of the electrode prepared at 40 °C, but still far superior to the comparative sample. This result indicates that 40 °C may be a better choice for balancing reaction rate, crystal quality, and catalytic performance, but the 50 °C process window remains effective, providing flexibility for different production conditions.

[0074] Example 4: Effect of different Ni / Fe molar ratios on electrode performance

[0075] This embodiment aims to investigate the effect of the Ni / Fe molar ratio in the reaction solution on electrode performance. The amounts of nickel chloride and ferrous chloride in the reaction solution were adjusted to achieve Ni / Fe molar ratios of 1:2, 1:1, and 2:1, respectively, while the remaining steps were exactly the same as in Example 1.

[0076] The results showed that Ni-Fe LDH catalyst layers could be successfully prepared under all three ratios, and the molar ratio of nickel to iron in the obtained catalyst layers was basically consistent with the feed ratio. Electrochemical tests showed that the electrodes exhibited good OER catalytic activity in the range of Ni / Fe molar ratio from 1:2 to 2:1, with the best performance observed when the Ni / Fe molar ratio was approximately 1:1.

[0077] Comparative Example 1: Nickel mesh as a substrate (instead of nickel felt)

[0078] Except for replacing the substrate material from three-dimensional porous nickel fiber felt with a commercially available nickel mesh of the same size, the preparation steps and reaction conditions were exactly the same as in Example 1. The resulting electrode exhibited poor uniformity in the distribution of the catalyst layer. Electrochemical testing showed that its oxygen evolution overpotential at a current density of 5000 A·m⁻² was 262 mV, significantly higher than that of the sample prepared with nickel felt as the substrate (217 mV). This result demonstrates that nickel felt, due to its larger specific surface area and superior three-dimensional structure, can support more active sites and provide more efficient mass transfer channels, thereby significantly improving OER performance.

[0079] Comparative Example 2: No urea added

[0080] Except for the absence of urea in the preparation of the reaction solution, the preparation steps were identical to those in Example 1. After the reaction, the surface of the obtained sample showed obvious residual nickel chloride crystals, and elemental analysis indicated a significantly high Cl content. SEM observation showed only a small amount of loose amorphous deposits, without the formation of hill-like clusters, and XRD patterns did not detect obvious FeOOH crystal phase characteristic peaks. Its OER catalytic performance was similar to that of the blank nickel felt, with an extremely high overpotential, indicating that urea plays a crucial role in adjusting the pH of the reaction system, promoting FeOOH nucleation and growth, and removing impurity ions.

[0081] Comparative Example 3: No air intake (oxygen-deficient environment)

[0082] Except for the use of nitrogen protection to remove oxygen during the deposition reaction and the sealing of the reaction apparatus, all other conditions were the same as in Example 1. After the reaction, the solution remained light green. The characteristic color indicates that ferrous ions were not oxidized to ferric ions. Only a small amount of deposits were observed on the nickel felt surface, and the typical hill-like nanorod cluster structure did not form. This sample... The overpotential was 246 mV, indicating that the catalytic performance was far inferior to that of the sample in Example 1. This result demonstrates that oxidizing gases (oxygen in the air) are the driving force for catalysis. Oxidized to The key factor is oxidation, which is essential for etching the nickel felt substrate, dissolving nickel ions, and participating in the in-situ co-deposition of Ni-FeOOH.

[0083] Comparative Example 4: High-concentration sediment

[0084] Except for adjusting the concentrations of nickel and iron salts in the reaction solution to five times that of Example 1, all other preparation conditions were the same as in Example 1. Figure 9 The SEM images show that the Ni-FeOOH catalyst supported on the nickel felt surface exhibits significant agglomeration due to excessive deposition, blocking the inherent three-dimensional porous structure of the nickel felt and severely impacting the mass transfer efficiency of the electrolyte and gas. The original three-dimensional hierarchical porous structure is destroyed, with both macroscopic and micron-sized pores filled by the catalyst. Despite the significant increase in catalyst loading, its OER performance did not improve accordingly; instead, it decreased due to limited mass transfer, demonstrating the advantage of low-concentration deposition strategies in constructing efficient three-dimensional hierarchical porous electrode structures.

[0085] Application Example 1: Hydrogen Production Unit via Water Electrolysis

[0086] Using the self-supporting electrode prepared in Example 1 as the anode and a commercial hydrogen evolution electrode as the cathode, an electrolytic water electrolysis hydrogen production device was assembled. The electrolyte in the electrolyzer was a 30 wt% KOH solution, and the operating temperature was 95°C. Under these industrial conditions, the electrolysis device exhibited excellent electrolysis performance and long-term stability, verifying the feasibility of the self-supporting electrode described in this invention in practical industrial applications.

Claims

1. A self-supporting electrode for the oxygen evolution reaction in water electrolysis, characterized in that, include: Three-dimensional porous nickel fiber felt conductive substrate; Nickel-doped iron hydroxide catalyst layer grown in situ on the surface of the nickel fiber felt; The catalyst layer is assembled from nanorods into a cluster structure, which together with the nickel fiber felt substrate forms a three-dimensional hierarchical porous conductive network.

2. The self-supporting electrode according to claim 1, characterized in that, The three-dimensional hierarchical porous conductive network includes: macroscopic pores formed by a nickel fiber felt skeleton, micron-sized pores formed between nanorod clusters, and nanoscale pores formed between nanorods.

3. The self-supporting electrode according to claim 1, characterized in that, The cluster-like structure is hill-shaped.

4. The self-supporting electrode according to any one of claims 1-3, characterized in that, The molar ratio of nickel to iron in the nickel-doped hydroxyl iron oxide is 1:2 to 2:

1.

5. A method for preparing a self-supporting electrode as described in any one of claims 1-4, characterized in that, Includes the following steps: (a) Provide a nickel fiber felt substrate and pretreat it to clean its surface; (b) Dissolve nickel salt, ferrous salt and urea in deionized water and stir to form a homogeneous solution; wherein the nickel salt is nickel chloride and the ferrous salt is ferrous chloride; (c) Immerse the substrate treated in step (a) into the solution in step (b) and react at 30-50 °C for 12-48 hours under continuous oxidizing gas; the oxidizing gas is used to oxidize ferrous ions to ferric ions, and the ferric ions etch the surface of the nickel fiber felt to dissolve nickel ions and participate in the co-deposition of nickel-doped iron hydroxyl oxide. (d) After the reaction is complete, the product is removed, washed and dried to obtain the self-supporting electrode.

6. The method according to claim 5, characterized in that, In step (b), the concentration of nickel ions in the solution is 0.05-0.2 mol / L, the concentration of ferrous ions is 0.05-0.1 mol / L, and the concentration of urea is 0.1-0.5 mol / L.

7. The method according to claim 5, characterized in that, In step (c), the oxidizing gas is air or oxygen.

8. The method according to claim 5, characterized in that, The pretreatment described in step (a) includes ultrasonic cleaning of the nickel fiber felt in sequence using an organic solvent, an acid solution, and deionized water.

9. An electrolytic water anode, characterized in that, It is composed of the self-supporting electrode as described in any one of claims 1-4.

10. A water electrolysis hydrogen production apparatus, comprising an electrolyzer, an anode, and a cathode, characterized in that, The anode is the water electrolysis anode as described in claim 9, and the electrolyte in the electrolytic cell is a KOH solution with a concentration of 20-35 wt%, and the operating temperature is 60-95℃.

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