Arginine composite FeNiOOH oxygen evolution electrocatalyst as well as preparation method and application thereof

Abstract

The invention provides an arginine composite FeNiOOH oxygen evolution electrocatalyst as well as a preparation method and application thereof, and belongs to the field of electrocatalytic materials. According to the arginine composite FeNiOOH oxygen evolution electrocatalyst provided by the invention, arginine molecules or derivatives thereof are introduced on the surface of FeNiOOH in situ to construct a Fe / Ni-N coordination structure, so that the Fe-Ni atom spacing is remarkably compressed, the d-d orbit coupling between metals is enhanced, the formation of O-O bonds is synergistically promoted, and an efficient OPM reaction path is preferentially activated; different from a traditional adsorption evolution mechanism or lattice oxygen mechanism, the reaction energy barrier is reduced, and the dynamic efficiency is improved. The arginine can further regulate and control the d-p orbital hybridization strength between metal and oxygen, optimize the adsorption free energy of other key OER intermediates, effectively inhibit the participation of lattice oxygen, significantly weaken the structural damage caused by LOM, and improve the stability of the catalyst.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials, specifically relating to an arginine-based FeNiOOH oxygen evolution electrocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy has attracted widespread attention as a clean and high-energy-density energy carrier. Alkaline water electrolysis is an important technology for achieving green hydrogen production, among which the anodic oxygen evolution reaction (OER) is a key step limiting its efficiency due to its slow kinetics. Currently, commonly used OER electrocatalysts are mostly noble metal oxides such as RuO2 and IrO2. Although they have high catalytic activity, their high cost and scarcity limit their large-scale application.

[0003] In recent years, iron-nickel oxyhydroxylates (FeNiOOH) have been considered potential alternatives to noble metal catalysts due to their abundant crustal reserves and excellent electrocatalytic activity. Traditional FeNiOOH electrocatalysts primarily drive oxidation-reduction (OER) through adsorption processes, following the adsorbate evolution mechanism (AEM). However, their catalytic activity is theoretically limited by the linear relationship between intermediate adsorption energies. Furthermore, some studies have attempted to activate the lattice oxygen-mediated mechanism (LOM) to improve performance, but this often leads to catalyst structural instability, affecting long-term durability. Therefore, developing an OER catalytic pathway that combines high activity and high stability is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide an arginine-based FeNiOOH oxygen evolution electrocatalyst, its preparation method, and its application. The arginine-based FeNiOOH oxygen evolution electrocatalyst provided by this invention has high activity and high stability.

[0005] To achieve the objectives of this invention, the following technical solutions are provided: An arginine-based FeNiOOH oxygen evolution electrocatalyst comprises a FeNiOOH nanoarray; the surface of the FeNiOOH nanoarray is anchored with arginine molecules and / or arginine derivative molecules via Fe-N and Ni-N coordination bonds.

[0006] Preferably, the FeNiOOH nanoarray is composed of flower-like spherical FeNiOOH nanostructures, which are formed by clusters of nanosheets; the average diameter of the flower-like spherical FeNiOOH is 300~800nm.

[0007] Preferably, the mass of the Arg molecule and / or Arg is 5-8% of the mass of the FeNiOOH nanoarray.

[0008] This invention also provides a method for preparing the arginine-based FeNiOOH oxygen evolution electrocatalyst described above, comprising the following steps: A conductive substrate is placed in a Fe-Ni precursor solution and subjected to a hydrothermal reaction to grow an in-situ FeNiOOH nanoarray on the surface of the conductive substrate, thereby obtaining the FeNiOOH precursor. The Fe-Ni precursor solution includes a soluble iron source, a soluble nickel source, an alkaline pH adjuster, a complexing agent, and a solvent. The FeNiOOH precursor was immersed in an arginine solution for impregnation treatment, and then annealed to obtain the arginine-composite FeNiOOH oxygen evolution electrocatalyst.

[0009] Preferably, the alkaline pH adjuster includes one of urea, hexamethylenetetramine, and ammonia water; The complexing agent includes one of fluoride ion complexing agents, sodium citrate, and ethylenediaminetetraacetic acid.

[0010] Preferably, based on the iron and nickel ions in the soluble iron source and the soluble nickel source, the molar ratio of the soluble iron source and the soluble nickel source is 1:1~3; The molar ratio of the alkaline pH adjuster to the total metal ions is 2:1, and the molar ratio of the complexing agent to the total metal ions is 1:1.

[0011] Preferably, the temperature of the hydrothermal reaction is 80~120℃, and the holding time is 6~12 h.

[0012] Preferably, the concentration of the arginine solution is 3-5 mmol / L.

[0013] Preferably, the impregnation treatment is performed at a temperature of 60-80°C for 3-5 hours. The annealing temperature is 200~250℃, and the time is 2~5h.

[0014] This invention also provides the application of the arginine composite FeNiOOH oxygen evolution electrocatalyst prepared by the above-mentioned technical solution or the arginine composite FeNiOOH oxygen evolution electrocatalyst prepared by the above-mentioned technical solution as an anode in water electrolysis for hydrogen production.

[0015] This invention provides an arginine-based FeNiOOH oxygen evolution electrocatalyst. The FeNiOOH nanoarray surface is anchored with arginine molecules and / or arginine derivatives via Fe-N and Ni-N coordination bonds. By in-situ introducing arginine molecules or their derivatives onto the FeNiOOH surface to construct a Fe / Ni-N coordination structure, this invention significantly compresses the Fe-Ni atomic spacing, enhances the dd orbital coupling between the metals, synergistically promotes O–O bond formation, and preferentially activates the efficient OPM reaction pathway. This differs from traditional adsorption evolution (AEM) or lattice oxygen (LOM) mechanisms, thereby lowering the reaction energy barrier, improving kinetic efficiency, and enhancing the activity of the oxygen evolution electrocatalyst. The introduction of arginine can further modulate the d–p orbital hybridization strength between the metal and oxygen, optimizing… The adsorption free energy of key OER intermediates is reduced, while the participation of lattice oxygen is effectively suppressed, significantly weakening the structural damage caused by LOM and improving the stability of oxygen evolution electrocatalysts.

[0016] The results of the embodiments of the present invention show that the catalyst at 100 mA·cm -2 It can operate stably for more than 200 hours at current density with an activity decay rate of less than 2%. This invention optimizes the oxygen evolution performance of FeNiOOH through molecular coordination engineering strategies, synergistically from two levels: electronic structure regulation and reaction pathway reconstruction. This provides a novel technical route and theoretical basis for constructing an efficient, stable, and low-cost alkaline OER catalytic system. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a comparison of the Fourier transform infrared (FTIR) spectra of the Arg catalyst of the present invention and the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 1; Figure 2 This is a comparison of high-resolution X-ray photoelectron spectroscopy (XPS) images of Arg@FeNiOOH and FeNiOOH oxygen evolution electrocatalysts obtained in Example 1 of this invention; Figure 3 This is a scanning electron microscope image of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 1 of the present invention; Figure 4 This is a transmission electron microscope image of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 1 of the present invention; Figure 5This is an elemental distribution mapping diagram of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 1 of the present invention; Figure 6 This is a scanning electron microscope image of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 2; Figure 7 This is a scanning electron microscope image of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 3; Figure 8 The graphs show a comparison of the oxygen evolution electrocatalytic performance of different catalysts in alkaline electrolytes, where (a) is the polarization curve, (b) is the electrochemical impedance spectroscopy, (c) is the Tafel slope graph, and (d) is the stability test graph. Figure 9 The following are the electrocatalytic performance test diagrams of the catalyst modified with different arginine concentrations in this invention, where (a) is the polarization curve, (b) is the comparison of overpotentials under different current densities, (c) is the Tafel slope diagram, and (d) is the electrochemical impedance spectroscopy. Figure 10 The images show the in-situ Raman spectra of FeNiOOH and Arg@FeNiOOH catalysts at different potentials; (a) shows the in-situ Raman spectrum of the FeNiOOH catalyst in the range from open circuit potential (OCP) to 1.6V (vs. RHE); (b) shows the in-situ Raman spectrum of the Arg@FeNiOOH catalyst in the same potential range. Figure 11 The images show the in-situ infrared spectra of FeNiOOH and Arg@FeNiOOH catalysts at different potentials; (a) is the in-situ infrared spectrum of FeNiOOH catalyst in the range from open circuit potential (OCP) to 1.6 V (vs. RHE); (b) is the in-situ infrared spectrum of Arg@FeNiOOH catalyst under the same potential conditions. Figure 12 Comparison of theoretical model structures of FeNiOOH and Arg@FeNiOOH catalysts; (a) model structure of unmodified FeNiOOH catalyst; (b) model structure of Arg@FeNiOOH catalyst after the introduction of arginine molecules; Figure 13 This is a comparison of the PDOS (projected density of states) at the metal-oxygen interface between FeNiOOH and Arg@FeNiOOH catalysts. Detailed Implementation

[0019] This invention provides an arginine-based FeNiOOH oxygen evolution electrocatalyst comprising a FeNiOOH nanoarray; the surface of the FeNiOOH nanoarray is anchored with arginine and / or arginine derivatives via Fe / Ni-N coordination bonds.

[0020] In this invention, the FeNiOOH nanoarray is composed of flower-like spherical FeNiOOH nanostructures, which are formed by clusters of nanosheets; the average diameter of the flower-like spherical FeNiOOH is 200-800 nm. The FeNiOOH nanoarray of this invention refers to an ordered array composed of unit structures with nanoscale characteristics. Specifically, the thickness of the nanosheets constituting the flower-like spherical structure is between 5 and 10 nm, and the length and width are 50-200 nm; while the diameter of the complete flower-like spherical structure is 200-800 nm. This type of nanoarray structure not only possesses abundant specific surface area and highly exposed active sites, but also provides excellent electron / ion channels and mechanical stability for the oxygen evolution reaction process, thereby significantly improving the electrochemical performance and lifespan of the catalyst.

[0021] In this invention, the mass of the Arg molecule and / or Arg derivative is 5-8% of the mass of the FeNiOOH nanoarray, and in specific embodiments it can be 5.3, 6, 6.8 or 7.5%; the arginine derivative is an arginine pyrolysis derivative.

[0022] This invention also provides a method for preparing the arginine-based FeNiOOH oxygen evolution electrocatalyst described above, comprising the following steps: A conductive substrate is placed in a Fe-Ni precursor solution and subjected to a hydrothermal reaction to grow an in-situ FeNiOOH nanoarray on the surface of the conductive substrate, thereby obtaining the FeNiOOH precursor. The Fe-Ni precursor solution includes a soluble iron source, a soluble nickel source, an alkaline pH adjuster, a complexing agent, and a solvent. The FeNiOOH precursor was immersed in an arginine solution for impregnation treatment, and then annealed to obtain the arginine-composite FeNiOOH oxygen evolution electrocatalyst.

[0023] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0024] In this invention, the conductive substrate can be nickel foam; the conductive substrate undergoes pretreatment before use; the pretreatment involves ultrasonic cleaning and drying sequentially in dilute hydrochloric acid, deionized water, and ethanol; the concentration of the dilute hydrochloric acid is 1 mol·L⁻¹. -1 .

[0025] In this invention, the soluble iron source includes iron nitrate, carbonate, or hydrochloride; the soluble nickel source includes nitrate, carbonate, or hydrochloride, and in specific embodiments, it can be Fe(NO3)3·9H2O and Ni(NO3)2·6H2O; the solvent is an ethanol / water solvent, and the volume ratio of ethanol to water is 1:1~3.

[0026] In this invention, the alkaline pH adjuster includes urea, hexamethylenetetramine (HMT), or ammonia; the complexing agent includes a fluoride ion complexing agent, sodium citrate, or ethylenediaminetetraacetic acid (EDTA). The fluoride ion complexing agent can be NH4F, NaF, or KF, and in a specific embodiment, it can be NH4F. In this invention, the alkaline pH adjuster is used to slowly release alkaline substances to adjust the pH and promote the precipitation of Fe / Ni hydroxide; the complexing agent is used to regulate the crystal growth rate, control morphology formation, and regulate the release of metal ions and the nucleation behavior of crystals, thereby meeting the needs for structural regulation and morphology control in different reaction systems.

[0027] In this invention, the pH value of the Fe-Ni precursor solution is 6.5.

[0028] In this invention, based on the iron and nickel ions in the soluble iron source and the soluble nickel source, the molar ratio of the soluble iron source and the soluble nickel source is 1:1 to 3; the total molar ratio of urea to metal ions is 2:1, and the total molar ratio of ammonium fluoride to metal ions is 1:1.

[0029] In this invention, the temperature of the hydrothermal reaction is 80~120℃, and in a specific embodiment it can be 90 or 100℃; the holding time is 6~12 h, and in a specific embodiment it can be 8 or 10 h; the hydrothermal reaction is carried out in a reaction vessel lined with polytetrafluoroethylene; after the hydrothermal reaction is completed, the obtained product is washed with water, washed with alcohol and dried in sequence; the drying temperature is 60~80℃.

[0030] In this invention, the FeNiOOH precursor is grown in situ on the surface of a conductive substrate via a hydrothermal reaction. Its formation process depends on the synergistic hydrolysis of metal ions and crystal self-assembly within the system. Specifically, the soluble iron source (e.g., Fe(NO3)3·9H2O) and the soluble nickel source (e.g., Ni(NO3)2·6H2O) are gradually hydrolyzed under hydrothermal conditions by the release of OH- ions from the thermal decomposition of a pH adjuster (e.g., urea), generating Fe(OH)3 and Ni(OH)2 precursor precipitates, respectively. With prolonged reaction time and increased temperature, these hydroxides undergo crystal rearrangement and partial oxidation, ultimately transforming into FeNiOOH complex hydroxylates with a layered structure, which then form a stable attachment on the conductive substrate surface. During this process, the complexing agent promotes the formation of nanosheets through selective adsorption and micro-etching effects, thereby inducing FeNiOOH to self-assemble at the nanoscale in layers, constructing a flower-like three-dimensional structural array.

[0031] The morphology of the FeNiOOH array of this invention is synergistically regulated by multiple synthesis parameters, including but not limited to the hydrothermal reaction temperature, holding time, metal ion molar ratio, additive dosage, and pH value of the precursor solution. Temperature controls reaction kinetics and crystal maturity; a suitable reaction temperature (e.g., 90–100 °C) is beneficial for the formation and ordered stacking of layered structures. pH value affects the hydrolysis and precipitation behavior of metal ions. The Fe / Ni ratio influences the electronic structure and crystallization tendency of FeNiOOH. The addition of ammonium fluoride promotes the formation of flower-like spherical structures.

[0032] In this invention, the concentration of the arginine solution is 3-5 mmol / L.

[0033] In this invention, the immersion treatment temperature is 60~80℃, and the heat preservation time is 3~5h.

[0034] In this invention, the annealing temperature is 200-250℃, and the time is 2-5 hours; the heating rate to the required annealing temperature is 5-10℃ / min. The annealing treatment is a key step in constructing the Fe / Ni-N coordination structure in the Arg@FeNiOOH electrocatalyst; controlling the annealing within the above range ensures a stable reaction environment and uniform structure. This process, without destroying the layered crystal structure of the FeNiOOH nanoarray, induces partial pyrolysis of the surface-impregnated arginine molecules, thereby generating nitrogen-containing derivatives with coordination capabilities. Specifically, during annealing, arginine undergoes thermally induced decarboxylation, deamination, or guanidine rearrangement reactions, forming short-chain nitrogen-containing pyrolysis products. The -NH2, =NH, or CN functional groups in these products can act as ligands to undergo in-situ coordination reactions with the Fe and Ni centers, forming stable metal-nitrogen coordination structures such as Fe-N and Ni-N, enhancing the electronic coupling and structural stability of the catalyst surface.

[0035] This invention also provides the application of the arginine composite FeNiOOH oxygen evolution electrocatalyst described in the above technical solution or the arginine composite FeNiOOH oxygen evolution electrocatalyst prepared by the preparation method described in the above technical solution as an anode in water electrolysis for hydrogen production.

[0036] To further illustrate the present invention, the arginine composite FeNiOOH oxygen evolution electrocatalyst, its preparation method, and its application provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0037] Example 1 Nickel foam pretreatment: Commercial nickel foam with dimensions of 2 cm × 3 cm was selected as the conductive substrate, and the substrate was successively subjected to 1 mol·L⁻¹ -1The nickel foam was ultrasonically cleaned in dilute hydrochloric acid, deionized water and anhydrous ethanol for 15 min to remove oxides and impurities, and then dried for later use.

[0038] In-situ growth of FeNiOOH nanoarrays: 2 mmol Fe(NO3)3·9H2O and 6 mmol Ni(NO3)2·6H2O were dissolved in 60 mL of a mixed solvent (deionized water and ethanol in a 2:1 volume ratio). 16 mmol urea and 8 mmol ammonium fluoride were added, and the mixture was magnetically stirred for 30 min to obtain a clear Fe-Ni precursor solution. The pretreated nickel foam was vertically immersed in the Fe-Ni precursor solution in a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally reacted at 120 °C for 10 h. After cooling, the nickel foam was removed, rinsed with water and ethanol, and dried at 60 °C to obtain the FeNiOOH precursor.

[0039] Arginine modification and annealing: The above FeNiOOH precursor was immersed in 5 mmol·L⁻¹ -1 The sample was immersed in an aqueous solution of L-arginine at 60°C for 3 hours. After immersion, it was removed, dried, and then subjected to nitrogen atmosphere at 5°C·min. -1 The temperature was raised to 250 °C, held for 2 hours, and then cooled to obtain the Arg@FeNiOOH catalyst.

[0040] Figure 1 This is a comparison of the Fourier transform infrared (FTIR) spectra of the arginine molecule and the Arg@FeNiOOH oxygen evolution electrocatalyst of this invention. Figure 1 The results show that the Arg@FeNiOOH sample is effective in the range of 400~4000 cm⁻¹. -1 The presence of most characteristic absorption peaks of arginine within the wavenumber range indicates that arginine molecules or their derivatives have been successfully loaded onto the FeNiOOH surface, and that their molecular framework was not completely destroyed after heat treatment, demonstrating good structural stability. Notably, the absorption peaks in the 1500–1650 cm⁻¹ range are also significant. -1The region exhibits significant peak position changes and intensity enhancements. This region primarily corresponds to bending vibration peaks of nitrogen-containing functional groups such as -NH2, -COOH, and guanidinium groups, or stretching vibration peaks of CN and C=N bonds. These changes indicate that some functional groups underwent chemical transformations during annealing, potentially involving decarboxylation, amino rearrangement, or electron redistribution, and coordinated with the Fe / Ni metal centers on the FeNiOOH surface. This further confirms that arginine or its pyrolysis derivatives form a Fe-N / Ni-N type coordination structure with the catalyst surface, providing the catalyst with additional active centers and electronic regulation capabilities. Therefore, these spectral results, through both functional group retention and peak position changes, jointly confirm the effective anchoring of arginine on the material surface and its participation in metal coordination.

[0041] Figure 2 This is a comparison of high-resolution X-ray photoelectron spectroscopy (XPS) spectra of Arg@FeNiOOH and FeNiOOH oxygen evolution electrocatalysts of this invention. Figures a and b show Arg@FeNiOOH, and figures c and d show the high-resolution spectra of FeNiOOH in the N 1s (Figure a), O 1s (Figure b), Fe 2p (Figure c), and Ni 2p (Figure d) regions, used to compare the changes in the electronic structure of the catalyst surface before and after arginine modification. In the N 1s spectrum shown in Figure a, the Arg@FeNiOOH sample clearly shows CN and MN (metal-nitrogen) coordination peaks, while FeNiOOH shows no obvious nitrogen signal. This indicates that arginine or its pyrolysis derivative has been successfully loaded and coordinated with the Fe / Ni metal center, forming a stable Fe-N / Ni-N structure. The O 1s region in Figure b can be decomposed into M-OH, MO, and H2O adsorption peaks. These components are present in both samples, but the M-OH signal is enhanced in Arg@FeNiOOH, indicating that the surface hydroxyl structure is regulated during the modification process, which may be related to the local environment regulation of arginine molecules. In the Fe 2p spectrum shown in Figure c, the main peak of the Arg@FeNiOOH sample shifts to the direction of higher binding energy by about 0.12 eV compared to FeNiOOH. 2+ with Fe 3+ The coexistence of states, accompanied by multiple satellite peaks (Sat.), indicates a decrease in the electron cloud density of Fe atoms, consistent with the electron traction effect of nitrogen ligands. The Ni 2p spectrum in Figure d also shows a positive shift of approximately 0.40 eV in the main peak, further supporting the formation of a Ni–N coordination bond between Ni and nitrogen ligands. In summary, Figure 2 XPS comparative analysis results demonstrate that by introducing arginine or its derivatives, the Arg@FeNiOOH electrocatalyst constructs a stable Fe-N / Ni-N coordination structure at the metal center and modulates its electronic structure, providing more active sites and an optimized electron transport environment for the subsequent oxygen evolution reaction.

[0042] Figure 3 This is a scanning electron microscope image of the arginine-composite FeNiOOH oxygen evolution electrocatalyst of the present invention; the results show that an array morphology of flower-like spherical nanostructures is grown on the surface of the conductive substrate. Figure 4 This is a transmission electron microscope (TEM) image of the arginine-composite FeNiOOH oxygen evolution electrocatalyst of this invention. The results show that it possesses a nanosheet-like layered structure. Specifically, a nanosheet refers to a structural unit with a two-dimensional layered structure, reaching the nanoscale in one dimension (usually thickness). Its characteristics include a thickness of several nanometers to tens of nanometers and a side length of tens to hundreds of nanometers, exhibiting a paper-like, thin-layered, or petal-like morphology. This structure possesses a high specific surface area, abundant exposed active sites, and excellent electron / ion transport performance, making it one of the important morphological features for improving electrocatalytic performance. Figure 4 The transmission electron microscope image shown reveals that the arginine-based FeNiOOH oxygen evolution electrocatalyst exhibits a distinct nanosheet-like layered structure, where multiple thin nanosheets are stacked and interleaved to form a three-dimensional flower-like array. This structure facilitates the full penetration of the electrolyte into the catalyst layer and increases the contact interface between the active species and the catalyst surface, thereby enhancing the reaction kinetics and stability during the oxygen evolution reaction. Figure 5 This is an elemental distribution mapping diagram of the arginine-composite FeNiOOH oxygen evolution electrocatalyst of the present invention. The figure shows the overall HAADF image (top left) and the energy dispersive spectroscopy (EDS) mapping results of C (carbon), N (nitrogen), O (oxygen), Fe (iron), and Ni (nickel). The results show that the elements are uniformly distributed on the material surface, confirming that arginine molecules are effectively anchored on the FeNiOOH nanostructure and form a Fe / Ni–N coordination structure.

[0043] Example 2 Nickel foam pretreatment Commercial nickel foam with dimensions of 2cm × 3cm was selected as the conductive substrate, and the substrate was successively subjected to 1 mol·L⁻¹ -1 The surface oxides and impurities were removed by ultrasonic cleaning in dilute hydrochloric acid, deionized water, and anhydrous ethanol for 15 minutes, and then dried for later use. The pretreatment method for the nickel foam was the same as in Example 1.

[0044] In-situ growth of FeNiOOH nanostructures: 2 mmol Fe(NO3)3·9H2O and 6 mmol Ni(NO3)2·6H2O were dissolved in 60 mL of a mixed solvent (deionized water to ethanol volume ratio of 2:1). 16 mmol urea and 8 mmol ammonium fluoride were added, and the mixture was magnetically stirred for 30 min to obtain a clear Fe-Ni precursor solution. Pretreated nickel foam was vertically immersed in the above solution and placed in a 100 mL polytetrafluoroethylene-lined reactor. The reaction was carried out hydrothermally at 100 °C for 6 h. After the reaction, the mixture was allowed to cool naturally, and the nickel foam was removed, thoroughly rinsed with deionized water and ethanol, and dried at 60 °C to obtain the FeNiOOH precursor.

[0045] Arginine modification and annealing: The obtained FeNiOOH precursor was immersed in 5 mmol·L⁻¹ -1 The sample was immersed in an aqueous solution of L-arginine at 60°C for 3 hours. The sample was then removed and dried, and then subjected to nitrogen atmosphere at 5°C / min. -1 The temperature was increased to 250℃ at a certain rate, held for 2 h, and then cooled to obtain the Arg@FeNiOOH oxygen evolution electrocatalyst.

[0046] Figure 6 The images show scanning electron microscope (SEM) images of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 2. The results indicate that under lower hydrothermal reaction temperatures and shorter reaction times, the nucleation and growth of FeNiOOH on the nickel foam substrate was insufficient. The resulting nanostructures were small in size and unevenly distributed, failing to form the regular, dense, flower-like spherical nanoarray morphology seen in Example 1. Scattered nanosheets or incomplete aggregates were still observed in some areas, indicating that crystal nucleation and growth were inhibited to some extent. Therefore, compared to lower hydrothermal reaction temperatures and shorter reaction times, the hydrothermal reaction parameters used in Example 1 are more conducive to the full growth and self-assembly of FeNiOOH nanostructures, resulting in a more regular, dense, and stable flower-like spherical nanoarray morphology, thus representing a preferred embodiment of the present invention.

[0047] Example 3 Nickel foam pretreatment: The pretreatment method for nickel foam is the same as in Example 1, and will not be repeated here.

[0048] In-situ growth of FeNiOOH nanoarrays: The preparation method of FeNiOOH precursor is completely consistent with that in Example 1. FeNiOOH nanoarrays are grown in situ on nickel foam substrate by hydrothermal reaction to obtain FeNiOOH precursor.

[0049] Arginine modification and annealing: The FeNiOOH precursor was immersed in 5 mmol·L⁻¹ -1 The sample was immersed in an aqueous solution of L-arginine at 60°C for 3 h. After immersion, the sample was placed in a nitrogen atmosphere at 5°C / min. -1 The temperature was increased to 500℃ at a certain rate, held for 2 h, and then cooled to obtain Arg@FeNiOOH oxygen evolution electrocatalysts under different heat treatment conditions.

[0050] Figure 7 The image shows a scanning electron microscope (SEM) image of the Arg@FeNiOOH oxygen evolution electrocatalyst obtained in Example 3. As can be seen from the image, the sample in Example 3 formed a continuously covered porous nanostructure on the conductive substrate surface. The overall structure consists of numerous wrinkled, randomly oriented nanosheets stacked together, exhibiting a loose three-dimensional network morphology. Although this structure still retains a certain number of pores, which is beneficial for electrolyte permeation, the nanosheets have uneven size distribution, obvious edge curling, and weak connectivity and order between the layers. Compared with the regular, dense flower-like spherical nanoarray structure in Example 1, the original array characteristics of the sample in Example 3 are significantly weakened, and local areas show loose structure and disordered stacking, indicating that under higher annealing temperatures, arginine modification has a certain degree of destructive effect on the FeNiOOH framework structure, leading to a decrease in structural integrity. Therefore, it can be seen that the porous network structure obtained in Example 3 is inferior to the flower-like spherical nanoarray structure in Example 1 in terms of morphological regularity and structural stability. This further illustrates that rationally controlling the arginine modification conditions and heat treatment parameters is of great significance for obtaining an oxygen evolution electrocatalyst with stable structure and excellent morphology.

[0051] Comparative Example 1 Nickel foam pretreatment: Commercial nickel foam with dimensions of 2 cm × 3 cm was selected as the conductive substrate, and the substrate was successively subjected to 1 mol·L⁻¹ -1 The nickel foam was ultrasonically cleaned in dilute hydrochloric acid, deionized water and anhydrous ethanol for 15 min to remove oxides and impurities, and then dried for later use.

[0052] In-situ growth of FeNiOOH nanoarrays: 2 mmol Fe(NO3)3·9H2O and 6 mmol Ni(NO3)2·6H2O were dissolved in 60 mL of a mixed solvent (deionized water and ethanol in a 2:1 volume ratio). 16 mmol urea and 8 mmol ammonium fluoride were added, and the mixture was magnetically stirred for 30 min to obtain a clear Fe-Ni precursor solution. The pretreated nickel foam was vertically immersed in the Fe-Ni precursor solution in a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally reacted at 120 °C for 10 h. After cooling, the nickel foam was removed, rinsed with water and ethanol, and dried at 60 °C to obtain the FeNiOOH catalyst.

[0053] Test case Electrocatalytic performance testing and mechanism verification 1) Electrochemical testing conditions This test example uses a three-electrode system for electrochemical testing, and the testing platform is a CHI 760E electrochemical workstation. The Arg@FeNiOOH obtained in Example 1 was used as the working electrode, and a platinum wire as the counter electrode. The Hg / HgO ratio was 1 mol·L⁻¹. -1 KOH electrode was used as the reference electrode. All electrochemical tests were performed at oxygen-saturated 1.0 mol·L⁻¹. -1 The experiment was conducted in an alkaline KOH electrolyte solution with a system pH of 14.

[0054] Before the test, the working electrode was activated by cyclic voltammetry (CV) at a scan rate of 5 mV·s. -1 To enhance electrode surface stability and activity, all test potentials were converted to the reversible hydrogen electrode (RHE) potential based on the Nernst equation: ERHE = EHg / HgO + 0.098 + 0.059 × pH. Catalytic performance was evaluated using linear sweep voltammetry (LSV). For the oxygen evolution reaction (OER), the scan voltage range was 0.8 V to 1.9 V (vs. RHE), and the scan rate was 5 mV·s. -1 For the hydrogen evolution reaction (HER), the voltage scan range was -0.5 V to 0 V (vs. RHE), and the scan rate was also 5 mV·s. -1 The charge transfer capability of the catalyst was evaluated using electrochemical impedance spectroscopy (EIS) at a frequency range of 100 kHz to 0.1 Hz, with frequency intervals of 1.5 mHz and an AC perturbation voltage amplitude of 5 mV. OER-related EIS tests were performed at a constant potential of 1.48 V (vs. RHE). Furthermore, to investigate the structural stability of the catalyst under strong oxidizing conditions, potentiostatic electrolysis was conducted at 1.48 V (vs. RHE), and its electrochemical stability was assessed by monitoring changes in steady-state current density.

[0055] 2) Performance test results The electrocatalytic performance of the Arg@FeNiOOH catalyst of this invention was evaluated by comparing it with that of the FeNiOOH sample obtained in Comparison 1 at 1.0 mol·L⁻¹. -1 OER performance was tested in KOH alkaline electrolyte. For example... Figure 8 As shown, Arg@FeNiOOH and FeNiOOH catalysts at 1.0 mol·L⁻¹ -1 The electrocatalytic oxygen evolution performance of KOH alkaline electrolyte was systematically compared and evaluated. Among them, the polarization curves ( Figure 8 a) indicates that Arg@FeNiOOH reaches 10 mA·cm⁻¹ -2 The overpotential required at the current density is only 225 mV, significantly better than the 256 mV of unmodified FeNiOOH, indicating higher intrinsic catalytic activity. Electrochemical impedance spectroscopy (EIS) Figure 8 b) shows that the Nyquist plot radius of Arg@FeNiOOH is smaller, and the interfacial charge transfer resistance is significantly reduced, reflecting its superior electron transport capability. Tafel slope comparison ( Figure 8 c) This further demonstrates that the Tafel slope of Arg@FeNiOOH is only 35.54 mV·dec -1 It is lower than the 64.96 mV·dec of FeNiOOH. -1 This indicates that its reaction kinetics are faster, which is beneficial for accelerating the formation and transformation of OER reaction intermediates. Constant current stability test ( Figure 8 d) shows that Arg@FeNiOOH at 100 mA·cm -2 It can operate stably for over 200 hours at high current densities with almost no significant current density decay and a performance retention rate exceeding 98%, fully demonstrating its excellent electrochemical stability and structural durability. In summary, Arg@FeNiOOH outperforms unmodified traditional FeNiOOH in terms of activity, conductivity, and stability, showcasing the significant advantages of this invention in the construction strategy of oxygen evolution electrocatalysts.

[0056] 3) Reaction pathway verification Figure 10 The images show the in-situ Raman spectra of FeNiOOH and Arg@FeNiOOH catalysts at different potentials. Figure 11 The images show the in-situ infrared spectra of FeNiOOH and Arg@FeNiOOH catalysts at different potentials. The in-situ Raman spectra are also shown. Figure 10 a) This shows that only Ni was observed in FeNiOOH over a potential range from OCP to 1.6 V (vs. RHE). 3+ -O and Fe 3+The characteristic vibrational peaks of -O indicate that it mainly retains the metal hydroxide structure, and no obvious intermediate signals appeared during the reaction. In contrast, the Raman spectrum of Arg@FeNiOOH under the same potential conditions ( Figure 10 b) In addition to having Ni 3+ -O and Fe 3+ In addition to the -O peak, a distinct CN vibration peak was also observed, indicating that the arginine molecule has been successfully anchored to the catalyst surface through Fe / Ni–N coordination; at the same time, the OO bond vibration signal was detected, indicating that the catalyst preferentially reacts along the OPM during the OER process.

[0057] in Figure 11 The FeNiOOH catalyst in catalyst a exhibited a significant OOH intermediate absorption peak during the increase of potential, which is a characteristic signal of AEM, indicating that its oxygen evolution reaction mainly relies on a stepwise adsorption-desorption pathway at metal sites. Figure 11 b, under the same conditions, Arg@FeNiOOH not only exhibits The OOH signal also revealed significant absorption peaks at the peroxy bond (OO) and CN, further confirming that arginine molecules regulate the electronic structure of the catalyst surface through Fe / Ni-N coordination, effectively inducing the OER pathway to transform from the traditional AEM to the more efficient OPM reaction pathway. In summary, the in-situ spectroscopic results clearly demonstrate that Arg@FeNiOOH preferentially triggers the OPM mechanism, which is a crucial source of its high activity and stability.

[0058] 4) Theoretical calculation and analysis To further elucidate the influence mechanism of the Fe / Ni-N coordination structure of this invention on the catalytic reaction performance, first-principles density functional theory (DFT) calculations were used to simulate and analyze the electronic structure and configuration of FeNiOOH and Arg@FeNiOOH.

[0059] Figure 12 The diagram shows a comparison of the theoretical model structures of FeNiOOH and Arg@FeNiOOH catalysts; for example... Figure 12 As shown, the optimized configurations of the two catalysts were compared. The results showed that in the unmodified FeNiOOH, the Fe-Ni interatomic distance was 3.04 Å, while after the introduction of L-arginine molecules and the formation of Fe / Ni-N coordination, the interatomic distance was effectively compressed to 2.94 Å. This indicates that the molecular coordination enhances the d–d orbital coupling between the bimetals, which is beneficial to the rapid transport and synergistic activation of electrons in the metal center.

[0060] Figure 13 This is a comparison of the PDOS (projected density of states) at the metal-oxygen interface between FeNiOOH and Arg@FeNiOOH catalysts; as shown. Figure 13As shown, the density of states (PDOS) between Fe and Ni metal d orbitals and O 2p orbitals in the two structures was compared. The results showed that the orbital hybridization intensity at the metal-oxygen interface was significantly enhanced in Arg@FeNiOOH, especially with greater overlap of the density of states near the Fermi level. This d-p orbital coupling effect is helpful for optimizing... The adsorption free energy of reaction intermediates such as OH, O, and OOH is reduced, thereby lowering the reaction barrier. Furthermore, hybridization enhancement effectively suppresses the non-selective participation of lattice oxygen, avoiding structural instability, weakening the dominance of LOM, and making the reaction pathway more inclined towards OPM. In summary, theoretical calculations confirm, from both the structural and electronic levels, the essential mechanism by which the molecular coordination regulation strategy in this invention improves catalyst performance.

[0061] Test Example 2 Effect of different arginine concentrations on catalytic performance The effect of different arginine concentrations on catalyst configuration regulation and oxygen evolution performance was investigated by impregnating the FeNiOOH precursor obtained in Example 1 with aqueous arginine solutions of different concentrations: 1, 5, 10, 15, and 20 mmol·L⁻¹. -1 The impregnation temperature was 60℃, and the holding time was 3h, with other treatment conditions remaining the same as in Example 1. Subsequently, the obtained samples were annealed under a nitrogen atmosphere at 250℃ for 2h. The resulting samples were named Arg@FeNiOOH-1, Arg@FeNiOOH-5, Arg@FeNiOOH-10, Arg@FeNiOOH-15, and Arg@FeNiOOH-20.

[0062] Figure 9 The graph shows the electrocatalytic performance of the catalyst modified with different arginine concentrations in this invention; wherein... Figure 9 a represents the comparison results of polarization curves, showing that Arg@FeNiOOH-5 at 10 mA·cm⁻¹ -2 It exhibits the lowest overpotential required at the current density, thus demonstrating optimal catalytic activity. Figure 9 b is at 10 mA·cm -2 With 50 mA·cm -2 The bar chart comparing overpotentials under the given conditions shows a trend of first decreasing and then increasing with increasing arginine concentration, further confirming the effect of 5 mmol·L⁻¹. -1 This is the optimal concentration. Figure 9 c represents the Tafel slope plot. Arg@FeNiOOH-5 has the smallest Tafel slope, indicating that its oxygen evolution reaction kinetics are the fastest. Figure 9Figure d shows the electrochemical impedance spectroscopy (EIS). In its Nyquist plot, Arg@FeNiOOH-5 exhibits the smallest arc radius, indicating the lowest interfacial charge transfer resistance and the highest interfacial reaction efficiency. In summary, these results demonstrate that a moderate concentration of L-arginine can significantly enhance the formation efficiency of Fe / Ni–N coordination active sites on the FeNiOOH surface, optimizing the metal electronic structure and interfacial electrochemical properties. Specifically, 5 mmol·L⁻¹ -1 The optimal concentration of arginine in this invention is determined by the concentration. If the concentration is too low, the number of coordination sites will be insufficient, making it difficult to effectively regulate the electronic structure. If the concentration is too high, the surface molecules will be too densely covered, hindering electron migration and exposure of active sites, which will result in a decrease in catalytic performance.

[0063] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An arginine-based FeNiOOH oxygen evolution electrocatalyst, characterized in that, It includes a FeNiOOH nanoarray; the surface of the FeNiOOH nanoarray is anchored with arginine molecules and / or arginine derivative molecules through Fe-N and Ni-N coordination bonds.

2. The arginine-composite FeNiOOH oxygen evolution electrocatalyst according to claim 1, characterized in that, The FeNiOOH nanoarray is composed of flower-like spherical FeNiOOH nanostructures, which are formed by clusters of nanosheets; the average diameter of the flower-like spherical FeNiOOH is 300~800nm.

3. The arginine-composite FeNiOOH oxygen evolution electrocatalyst according to claim 1, characterized in that, The mass of the Arg molecule and / or Arg is 5-8% of the mass of the FeNiOOH nanoarray.

4. The preparation method of the arginine composite FeNiOOH oxygen evolution electrocatalyst according to any one of claims 1 to 3, characterized in that, Includes the following steps: A conductive substrate is placed in a Fe-Ni precursor solution and subjected to a hydrothermal reaction to grow an in-situ FeNiOOH nanoarray on the surface of the conductive substrate, thereby obtaining the FeNiOOH precursor. The Fe-Ni precursor solution includes a soluble iron source, a soluble nickel source, an alkaline pH adjuster, a complexing agent, and a solvent. The FeNiOOH precursor was immersed in an arginine solution for impregnation treatment, and then annealed to obtain the arginine-composite FeNiOOH oxygen evolution electrocatalyst.

5. The preparation method according to claim 4, characterized in that, The alkaline pH adjuster includes one of urea, hexamethylenetetramine, and ammonia water; The complexing agent includes one of fluoride ion complexing agents, sodium citrate, and ethylenediaminetetraacetic acid.

6. The preparation method according to claim 4, characterized in that, Based on the iron and nickel ions in the soluble iron source and the soluble nickel source, the molar ratio of the soluble iron source and the soluble nickel source is 1:1~3; The molar ratio of the alkaline pH adjuster to the total metal ions is 2:1, and the molar ratio of the complexing agent to the total metal ions is 1:

1.

7. The preparation method according to claim 4 or 6, characterized in that, The hydrothermal reaction is carried out at a temperature of 80~120℃ and the holding time is 6~12 h.

8. The preparation method according to claim 4, characterized in that, The concentration of the arginine solution is 3-5 mmol / L.

9. The preparation method according to claim 4 or 8, characterized in that, The impregnation treatment is performed at a temperature of 60-80°C for 3-5 hours. The annealing temperature is 200~250℃, and the time is 2~5h.

10. The application of the arginine composite FeNiOOH oxygen evolution electrocatalyst according to any one of claims 1 to 3 or the arginine composite FeNiOOH oxygen evolution electrocatalyst prepared by the preparation method according to any one of claims 4 to 9 as an anode in water electrolysis for hydrogen production.

Images