Ni3Cu-Ni (OH) 2 heterogeneous catalyst for high-current hydrogen evolution and preparation method of Ni3Cu-Ni (OH) 2 heterogeneous catalyst

Abstract

The invention discloses a Ni3Cu-Ni (OH) 2 heterogeneous catalyst for high-current hydrogen evolution and a preparation method of the Ni3Cu-Ni (OH) 2 heterogeneous catalyst. The preparation method comprises the following steps: firstly, pretreating a foamed nickel substrate; then, under the optimized plating solution formula, current density and deposition time, a Ni3Cu alloy plating layer is formed on the foamed nickel substrate through a constant-current electro-deposition method; and finally, synthesizing the Ni3Cu-Ni (OH) 2 heterostructure catalyst in a 1M KOH electrolyte through in-situ electrochemical oxidation. The heterogeneous interface of the alloy and the hydroxide is constructed through an electro-deposition-in-situ oxidation method, and mass transfer is optimized in combination with a multistage dendritic structure, so that the catalyst has excellent performance in alkaline high-current hydrogen evolution, and a feasible scheme is provided for a low-cost and efficient industrial-grade catalyst for hydrogen production by water electrolysis.

Description

Technical Field

[0001] This invention relates to the field of electrochemical catalytic materials and hydrogen production technology, specifically to a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution and its preparation method, which is applicable to new energy fields such as water electrolysis for hydrogen production and fuel cells. Background Technology

[0002] In the global transition to clean energy, hydrogen energy, as a highly efficient and clean secondary energy source, is considered a key alternative to traditional fossil fuels. Electrolysis of water is currently the most promising green hydrogen production technology, with alkaline electrolyzers becoming the mainstream industrial application due to their lower cost and safer operation. Commercial alkaline electrolyzers typically require 500-1000 mA / cm² operating conditions. -2 Stable operation at high current densities places stringent requirements on catalyst performance: it must not only possess excellent hydrogen evolution activity to reduce energy consumption, but also have long-term stability to meet the needs of continuous industrial production.

[0003] Currently, although platinum (Pt)-based noble metal catalysts exhibit extremely high catalytic activity in the hydrogen evolution reaction (HER), their reserves are scarce (their abundance in the Earth's crust is only 5 × 10⁻⁶). -9 Alkaline electrolyzers are expensive (approximately 300 RMB / gram) and their activity easily decreases due to the adsorption of intermediate products in alkaline environments, severely restricting the large-scale commercial application of water electrolysis for hydrogen production. Therefore, developing low-cost, highly active, and long-life non-precious metal catalysts has become a core issue in overcoming the industrialization bottleneck of alkaline electrolyzers.

[0004] Among non-precious metals, nickel (Ni)-based materials have become a research hotspot due to their good hydrogen evolution reaction (HER) activity and conductivity. NiCu alloys, in particular, can optimize the adsorption energy barrier of hydrogen intermediates (H*) through alloying effects, further enhancing catalytic activity. However, they suffer from significant drawbacks: the lack of effective water adsorption sites on the surface leads to low water dissociation efficiency at high current densities, and the obstruction of charge and mass transport causes the hydrogen evolution overpotential to increase sharply with increasing current density. Furthermore, single NiCu alloys are prone to having their active sites covered by bubble adhesion during long-term high-current operation, making their stability unsatisfactory for industrial applications.

[0005] The development of traditional alkaline hydrogen evolution catalysts has mainly focused on single metal, alloy, or metal oxide systems, but these solutions have significant limitations. Regarding single metal catalysts, while pure Ni catalysts are relatively inexpensive, their HER activity is limited under alkaline conditions, especially at high current densities (e.g., 500 mA / cm²). -2 At the above levels, the overpotential typically exceeds 500mV, and long-term operation is prone to activity decay due to oxidation. For example, commercially available pure Ni electrodes at 1000mA / cm²... -2The overpotential is as high as 600mV or more, and the stability is less than 100 hours, which cannot meet the requirements of industrial applications.

[0006] Regarding alloy catalysts, early studies on binary alloys such as NiFe and NiCo, while improving H* adsorption performance through electronic effects, still failed to solve the mass transfer problem under high current. Taking NiFe alloy as an example, its mass transfer performance at 100 mA / cm²... -2 The overpotential is approximately 150 mV, but the current density rises to 1000 mA / cm². -2 When the overpotential suddenly increases to over 400mV, and the dense surface structure makes it difficult for bubbles to detach, the activity decreases by more than 30% after 100 hours of operation.

[0007] In the field of metal oxide / hydroxide catalysts, Ni(OH)₂ has a strong water adsorption capacity, which can promote the water dissociation step (Volmer step), but its own conductivity is poor (approximately 10). -5 The high overpotential (S / cm) of a pure Ni(OH)₂ electrode at 1000 mA / cm⁻¹ results in impaired charge transport and exhibits extremely high overpotentials under high currents. For example, the overpotential of a pure Ni(OH)₂ electrode at 1000 mA / cm⁻¹ is significantly reduced. -2 The overpotential exceeds 550mV, and due to its loose structure, it is easy to detach, resulting in a stability of only tens of hours.

[0008] Meanwhile, traditional preparation methods (such as chemical reduction and high-temperature calcination) struggle to precisely control the microstructure of catalysts, leading to insufficient exposure of active sites and impaired mass transfer channels. For example, NiCu alloys prepared by chemical reduction often exhibit a particle agglomeration structure with a small specific surface area (typically below 50 m²). 2 / g), which cannot provide a sufficient reaction interface under high current, further limits its performance improvement.

[0009] In recent years, research on alkaline high-current hydrogen evolution catalysts has made some progress, mainly focusing on two major directions: heterostructure design and optimization of preparation methods. However, key technological bottlenecks still exist. In terms of heterostructure design, researchers have attempted to construct metal-hydroxide composite systems, utilizing the high conductivity of the metal phase and the strong water adsorption capacity of the hydroxide phase to achieve synergistic effects. For example, the Ni-Ni(OH)₂ heterostructure catalyst reported in the literature provides an electron transport channel through the Ni substrate, while Ni(OH)₂ promotes water adsorption and dissociation, achieving a high efficiency at 100 mA / cm⁻¹. -2The overpotential drops to around 120 mV, but these catalysts are mostly prepared using physical mixing methods, resulting in weak heterogeneous interface bonding and easy phase separation under high current, leading to stability of less than 500 hours. Regarding preparation methods, electrodeposition is widely used due to its simplicity and high controllability, but traditional electrodeposition processes have limitations: for example, constant potential electrodeposition makes it difficult to control the morphology of the coating, easily forming a dense layer that hinders mass transfer; and high-temperature calcination-assisted preparation methods can damage the catalyst's nanostructure, leading to a reduction in active sites. For example, a NiCu-NiO heterostructure prepared using an existing "electrodeposition-calcination" method showed a stability of less than 500 hours under 500 mA / cm². -2 The overpotential is 300mV, and the calcination process causes Cu to be lost, resulting in a stability of only 300 hours.

[0010] Current technologies still lack sufficient control over interfacial water chemistry. In alkaline HER, the adsorption orientation of interfacial water molecules and the strength of the hydrogen bond network directly affect the kinetics of the Volmer step, but most studies have not linked the interfacial water structure to catalyst performance. For example, water molecules on the surface of traditional NiCu alloys are adsorbed with strong hydrogen bonds, resulting in a high desorption barrier for the OH* intermediate and a slow water dissociation rate, which limits the reaction kinetics under high current. Summary of the Invention

[0011] Based on the above-mentioned technical problems, this application discloses a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution and its preparation method. Specifically, the Ni3Cu-Ni(OH)2 heterocatalyst is as follows: it uses nickel foam as a substrate, and the whole exhibits a multi-level dendritic structure at the edge of the framework nanoclusters. Small clusters are formed by the stacking of small particles, and the framework edge is a three-dimensional dendritic hierarchical structure. A composite phase of Ni3Cu alloy and Ni(OH)2 is formed on the surface, wherein Ni(OH)2 grows at the edge of Ni3Cu alloy. The high-resolution transmission electron microscopy image shows that its internal lattice stripes correspond to the Ni3Cu(111) crystal plane, and the external lattice stripes correspond to the Ni(OH)2(111) crystal plane. The Ni, Cu, and O elements are uniformly distributed on the surface of the material, and the surface is enriched with interfacial water molecules that are directionally adsorbed by weak hydrogen bond configuration.

[0012] Preferably, the molar ratio of Ni:Cu in the Ni3Cu alloy is 3:1, which is achieved by adjusting the concentrations of NiSO4·6H2O and CuSO4 in the plating solution during the electrodeposition process.

[0013] Preferably, the Ni(OH)2 in the composite phase is generated by in-situ electrochemical CV oxidation etching of Ni3Cu / NF, with an oxidation range of 0.9-1.6V vs. RHE, performed under isothermal conditions in a 30°C water bath; the coverage of Ni(OH)2 is 30-50%, achieved by controlling the number of electrochemical oxidation cycles, with an optimized number of 10 cycles.

[0014] A method for preparing a catalyst, specifically comprising:

[0015] S1. Pre-treat the nickel foam substrate, including ultrasonically removing surface oil stains in acetone and cleaning, ultrasonically treating it in HCl solution, cleaning it after treatment, and ultrasonically cleaning it in anhydrous ethanol to obtain the pre-treated nickel foam.

[0016] S2. Preparation of Ni3Cu / NF catalyst: The prepared electroplating buffer and metal source were added to a beaker and magnetically stirred to form an electroplating solution. A three-electrode system was used, with pretreated nickel foam as the working electrode, polished nickel sheet as the counter electrode, and Ag / AgCl dual salt bridge electrode as the reference electrode. Constant current electrodeposition was performed on an Autolab electrochemical workstation. After electroplating, the catalyst was cleaned with ethanol and deionized water and dried in a vacuum drying oven to obtain Ni3Cu / NF.

[0017] S3. Preparation of Ni3Cu-Ni(OH)2 / NF heterostructure catalyst: Using Ni3Cu / NF as a precursor, in-situ electrochemical oxidation etching was performed in KOH electrolyte using a three-electrode system. The working electrode was Ni3Cu / NF, the counter electrode was a graphite sheet, and the reference electrode was a Hg / HgO electrode. CV oxidation was carried out in an Autolab electrochemical workstation under water bath conditions. After oxidation, the catalyst was cleaned with ethanol and deionized water and dried in a vacuum drying oven to obtain the Ni3Cu-Ni(OH)2 / NF heterostructure catalyst.

[0018] Preferably, in the plating solution prepared in S2, the electroplating buffer is selected from one or more of K4P2O7, C2H5NO2, CH4N2O, and C6H5N3; and the metal source is selected from one or more of NiSO4·6H2O and CuSO4.

[0019] Preferably, during the constant current electrodeposition in S2, the spacing between the three electrodes is controlled to be 2-3 cm, and the immersion area of ​​the working electrode is 1-2 cm². 2 One side of the nickel foam participates in the reaction. Before electrodeposition, the electroplating solution needs to be deoxygenated with nitrogen. During the electrodeposition process, the potential change of the working electrode is recorded every preset time period to keep the potential fluctuation not exceeding ±5mV.

[0020] Preferably, the deposition current density of the constant current electrodeposition is 250-280 mA / cm². -2 The deposition time is 600-750s, and the deposition temperature is controlled at 30±1℃. During the electrodeposition process, the current output accuracy of the Autolab electrochemical workstation is ±1mA, and the plating solution is continuously stirred at a stirring rate of 300-400rpm to ensure uniform concentration of the plating solution.

[0021] Preferably, the 1M KOH electrolyte used for in-situ electrochemical oxidation etching in S3 is prepared by dissolving pure KOH in ultrapure water and removing air bubbles. The volume of the KOH electrolyte is 10-15 times the volume of the working electrode. Meanwhile, the Hg / HgO reference electrode needs to be activated in 1M KOH before use.

[0022] Preferably, in step S3, CV oxidation is performed on an Autolab electrochemical workstation using a water bath at a constant temperature. The oxidation control method is as follows: the start potential and end potential of the CV scan are set, the scan rate is set, and after reaching the set end potential, one scan cycle is completed, and the scan is paused for a preset time before the next scan cycle is performed, until the preset number of scan cycles is completed and the oxidation is completed.

[0023] Preferably, the cleaning is performed by centrifugation at a speed of 3000-4000 rpm for 3-5 minutes each time. After centrifugation, the waste liquid is poured out and new solvent is added for the next cleaning.

[0024] Compared with the prior art, the technical solution of this application has the following technical effects:

[0025] This invention constructs a heterogeneous structure of Ni3Cu alloy phase and Ni(OH)2 hydroxide phase, and forms a multi-level dendritic structure at the edge of the framework nanocluster through electrodeposition process. It has an ultra-large specific surface area, can construct efficient mass transfer channels, and solve the problem of bubble adhesion under high current. In contrast, the catalysts of the prior art are mostly dense particles or disordered stacking structures with large mass transfer resistance.

[0026] This invention activates Ni3Cu alloy by in-situ electro-oxidation to generate Ni(OH)2 on the surface, forming a strongly interacting heterogeneous interface. This promotes electron transfer from Ni to Cu, reduces the d-band center of Ni, optimizes H* adsorption energy, and the heterogeneous interface can enrich water molecules with weak hydrogen bond configuration, effectively reducing the OH* desorption energy barrier and accelerating the Volmer step kinetics.

[0027] This invention determines 250mAcm using a single-factor controlled variable method. -2 Key parameters such as current density, 600s deposition time, and 10 cycles of oxidation etching are used to ensure that the ratio of Ni3Cu to Ni(OH)2 is precisely controllable.

[0028] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0029] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0031] Based on the description of the figures and their corresponding technical content in the document, the titles of the figures are as follows:

[0032] Figure 1 Flowchart for the preparation of Ni3Cu-Ni(OH)2 / NF heterocatalyst;

[0033] Figure 2 The X-ray diffraction (XRD) pattern of the Ni3Cu-Ni(OH)2 / NF heterocatalyst is shown.

[0034] Figure 3 The Raman spectrum of the Ni3Cu-Ni(OH)2 / NF heterocatalyst is shown.

[0035] Figure 4 This is a field emission scanning electron microscope (FESEM) image of the Ni3Cu-Ni(OH)2 / NF heterocatalyst.

[0036] Figure 5 The images show transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray spectroscopy (EDS) images of the Ni3Cu-Ni(OH)2 / NF heterocatalyst.

[0037] Figure 6 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the Ni3Cu-Ni(OH)2 / NF heterocatalyst.

[0038] Figure 7 Figure 1 shows the gas-repellency measurement of catalysts with different structures in HER.

[0039] Figure 8 The graph shows the HER performance of different catalysts tested in 1M KOH at 30℃.

[0040] Figure 9 500mAcm -2HER stability diagram of Ni3Cu-Ni(OH)2 / NF catalyst at current density;

[0041] Figure 10 SEM images of the Ni3Cu-Ni(OH)2 / NF catalyst before (ab) and after (cd) stability test after 1600 h;

[0042] Figure 11 XPS comparison graphs before and after 1600h stability test of Ni3Cu-Ni(OH)2 / NF catalyst. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0044] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0045] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0046] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0047] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0048] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0049] Example 1

[0050] This embodiment mainly describes a method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution, such as... Figure 1 As shown, it specifically includes:

[0051] S1. Pre-treat the nickel foam substrate by cutting 10*10mm pieces of nickel foam, first sonicating it in acetone for 20 minutes to remove surface oil, then rinsing it with deionized water; then sonicating it in a 3M HCl solution at 40℃ for 20 minutes to remove the surface oxide layer and increase hydrophilicity, then rinsing it with deionized water; finally sonicating it in anhydrous ethanol for 15 minutes, and rinsing it with anhydrous ethanol. Place the pre-treated nickel foam in anhydrous ethanol for later use.

[0052] S2. Preparation of Ni3Cu / NF catalyst: Weigh 19.82g K4P2O7, 2.252g C2H5NO2, 6.06g CH4N2O, and 0.05g C6H5N3 as electroplating buffer, and 1.183g NiSO4·6H2O and 0.2394g CuSO4 as metal sources. Add these to a 150mL beaker containing 100mL ultrapure water and stir magnetically for 30min to form a clear, bluish-green plating solution. Use a three-electrode system with pretreated nickel foam as the working electrode, polished nickel sheet as the counter electrode, and Ag / AgCl dual salt bridge electrode as the reference electrode. Perform constant current electrodeposition at 30℃ on an Autolab electrochemical workstation with a current density of 250mAcm. -2 The deposition time was 600s to ensure that the metal ratio of Ni to Cu was 3:1. After electroplating, the sample was washed three times each with ethanol and deionized water, and then dried in a vacuum drying oven at 40℃ to obtain black Ni3Cu / NF.

[0053] S3. Preparation of Ni3Cu-Ni(OH)2 / NF heterostructure catalyst: Using Ni3Cu / NF as a precursor, in-situ electrochemical oxidation etching was performed in 1 M KOH electrolyte using a three-electrode system. The working electrode was a Ni3Cu / NF electrode, the counter electrode was a graphite sheet, and the reference electrode was a Hg / HgO electrode. CV oxidation was performed on an Autolab electrochemical workstation under a 30℃ water bath constant temperature condition. The oxidation range was 0.9-1.6 V vs. RHE, and the number of oxidation cycles was 10. After oxidation, the catalyst was washed three times each with ethanol and deionized water, and dried in a vacuum drying oven at 40℃ to obtain a black Ni3Cu-Ni(OH)2 / NF heterostructure catalyst.

[0054] Furthermore, the pretreatment of the nickel foam substrate in S1 specifically includes: cutting nickel foam to a size of 10mm×10mm, placing it in acetone, treating it under ultrasonic conditions for 20 minutes, then removing it and rinsing the surface with deionized water; placing the acetone-treated nickel foam in a 3M HCl solution at 40℃, treating it under ultrasonic conditions for 20 minutes, and rinsing it with deionized water after treatment; then transferring the nickel foam to anhydrous ethanol, ultrasonically cleaning it for 15 minutes, and then rinsing the surface with anhydrous ethanol; finally, storing the pretreated nickel foam in anhydrous ethanol for later use, and the pretreatment operations for other foam metal substrates are the same as the above pretreatment operations for nickel foam.

[0055] Furthermore, the preparation process of the plating solution for preparing the Ni3Cu / NF catalyst in S2 is as follows: 100mL of ultrapure water is added to a 150mL beaker, and then 19.82g K4P2O7, 2.252g C2H5NO2, 6.06g CH4N2O, and 0.05g C6H5N3 are added sequentially as electroplating buffer, and 1.183g NiSO4·6H2O and 0.2394g CuSO4 are added as metal sources; the beaker is placed on a magnetic stirrer and stirred for 30min until a clear blue-green plating solution is formed.

[0056] Furthermore, the specific operating parameters for the constant current electrodeposition in S2 are as follows: a three-electrode system is used, wherein the working electrode is the pretreated nickel foam from step S1, the counter electrode is a polished nickel sheet, and the reference electrode is an Ag / AgCl dual salt bridge electrode; the electrodeposition process is performed on an Autolab electrochemical workstation, the deposition temperature is controlled at 30℃, and the current density is set to 250 mA / cm². -2 The deposition time was set to 600s. After electrodeposition, the obtained catalyst was washed three times with ethanol and then three times with deionized water. After that, it was dried in a vacuum drying oven at 40℃ to obtain a black Ni3Cu / NF catalyst.

[0057] Furthermore, the Ni to Cu metal ratio in S2 is controlled at 3:1. This ratio is achieved by adjusting the amount of NiSO4·6H2O and CuSO4 in the plating solution, with NiSO4·6H2O accounting for 1.183g and CuSO4 accounting for 0.2394g. During the electrodeposition process, the Ni to Cu metal ratio in the final Ni3Cu alloy is kept stable at 3:1 by controlling the current density and deposition time.

[0058] Furthermore, the electrolyte for in-situ electrochemical oxidation etching in S3 was a 1M KOH solution, using a three-electrode system. The working electrode was the Ni3Cu / NF catalytic electrode prepared in step S2, the counter electrode was a graphite sheet, and the reference electrode was a Hg / HgO electrode. The oxidation etching process was carried out on an Autolab electrochemical workstation, with the oxidation potential range set at 0.9-1.6V vs. RHE, and the reaction environment was a 30℃ water bath. After the oxidation etching was completed, the catalyst was cleaned three times with ethanol, then three times with deionized water, and then dried in a vacuum drying oven at 40℃ to obtain a black Ni3Cu-Ni(OH)2 / NF heterostructure catalyst.

[0059] Furthermore, the number of oxidation cycles in the in-situ electrochemical oxidation etching in S3 is 10 cycles. The number of cycles is controlled by the program of the Autolab electrochemical workstation. The potential scan range of each cycle is 0.9-1.6V vs. RHE. The scan rate is set according to the instrument's default parameters to ensure that an appropriate amount of Ni(OH)2 species can be generated on the surface of the Ni3Cu / NF catalytic electrode after 10 cycles of oxidation etching.

[0060] Furthermore, the cleaning operation was carried out in sequence with ethanol and deionized water, and each solvent was used to clean the catalyst three times. During cleaning, the catalyst was placed in a container filled with ethanol or deionized water and the cleaning was carried out by immersion and shaking. Each cleaning time was 1-2 minutes to ensure that the residual plating solution components, reaction by-products and other impurities on the catalyst surface were removed.

[0061] Furthermore, all drying operations were carried out in a vacuum drying oven at a temperature of 40°C for 8 hours. The vacuum level of the drying oven was controlled between -0.08 MPa and -0.1 MPa to ensure that the moisture and ethanol on the catalyst surface could be fully evaporated during the drying process and to prevent external impurities from contaminating the catalyst. Afterward, the catalyst was transferred to a clean sample box with tweezers and sealed for preservation to prevent the catalyst surface from adsorbing moisture and impurities from the air, thus ensuring the accuracy of subsequent performance tests.

[0062] This embodiment details the efficient preparation of a stable Ni3Cu-Ni(OH)2 / NF heterocatalyst. Through precise pretreatment, electrodeposition, and oxidative etching, the catalyst composition is ensured to be uniform and the structure is intact. The cleaning and drying steps ensure surface cleanliness. The prepared catalyst has high consistency and small batch quality deviation, and can be stably used in alkaline hydrogen evolution reaction, providing a reliable sample for subsequent performance verification.

[0063] Based on Example 1, this example details the phase characterization and structural analysis of the Ni3Cu-Ni(OH)2 / NF heterocatalyst, specifically as follows:

[0064] The crystal structure and composition of the Ni3Cu-Ni(OH)2 / NF heterocatalyst were characterized by X-ray diffraction (XRD) and Raman spectroscopy. XRD results showed that the pure Ni coating exhibited three characteristic diffraction peaks at 44.5°, 51.8°, and 76.3°. Figure 2 As shown, these correspond to the (111), (200), and (220) crystal planes of Ni, respectively. Due to lattice expansion, the diffraction peaks of the electrodeposited Ni3Cu alloy shifted to lower angles at 44.2°, 51.5°, and 75.8°, matching the standard Ni3Cu card, indicating the successful formation of the Ni3Cu alloy phase. After in-situ CV oxidation etching, the characteristic peaks of the Ni3Cu alloy in the XRD pattern of Ni3Cu-Ni(OH)2 / NF were broadened and the symmetry was reduced. At the same time, weak diffraction peaks appeared at 19.2°, 33.2°, and 59.1°, corresponding to the (001), (100), and (110) crystal planes of Ni(OH)2, confirming that the oxidation process generated the Ni(OH)2 phase on the alloy surface.

[0065] like Figure 3 As shown, Raman spectroscopy further confirmed the formation of the heterostructure. Unoxidized Ni3Cu / NF showed high concentrations at 445 cm⁻¹ and 520 cm⁻¹. -1 Characteristic vibrational peaks of the Ni-Cu alloy were observed at 540 cm⁻¹, while a new, significant peak was added at 540 cm⁻¹ in the oxidized Ni₃Cu-Ni(OH)₂ / NF, corresponding to the stretching vibration of the Ni-O bond in Ni(OH)₂. The peak intensity of the original alloy was slightly weakened, indicating that Ni(OH)₂ and the Ni₃Cu alloy formed a composite structure. Both XRD and Raman results demonstrate that a heterostructure with coexisting Ni₃Cu alloy and Ni(OH)₂ phases was successfully constructed via an "electrodeposition-in-situ oxidation" process, laying the structural foundation for the synergistic improvement of subsequent catalytic performance.

[0066] Furthermore, the microstructure and surface structure of the Ni3Cu-Ni(OH)2 / NF catalyst were analyzed using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM images revealed that the catalyst exhibits a three-dimensional network framework structure, with the surface composed of clusters of approximately 60 nm nanoparticles stacked to form 200 nm clusters. The edges show a multi-level dendritic distribution, such as... Figure 4 As shown in (ab). This structure not only increases the specific surface area of ​​the catalyst but also creates abundant pore channels, which is beneficial for electrolyte permeation and gas diffusion. High-magnification SEM images are shown below. Figure 4 (c) Further observation shows that the cluster particles have smooth surfaces and no obvious agglomeration, indicating that the in-situ oxidation process did not destroy the framework structure of the Ni3Cu alloy, but only formed a uniform modification layer on the surface.

[0067] TEM analysis further revealed details of the heterostructure: low-magnification TEM images showed that the tertiary dendritic structure was composed of nanoparticle clusters, with a passivation film of approximately 5-10 nm thickness on the outermost layer, such as... Figure 5 As shown in (a); in the high-resolution TEM image, the lattice fringe spacing in the inner region is 0.203 nm, corresponding to the (111) crystal plane of the Ni3Cu alloy, while the fringe spacing in the outer layer is 0.241 nm, corresponding to the (111) crystal plane of Ni(OH)2, as shown in (a). Figure 5 As shown in (b), Ni(OH)₂ is confirmed to grow in situ on the surface of the Ni₃Cu alloy, forming a tightly bonded heterogeneous interface. The elemental mapping diagram of X-ray energy dispersive spectroscopy (EDS) shows that Ni, Cu, and O elements are uniformly distributed throughout the catalyst surface, as shown in [the diagram]. Figure 5 As shown in (c), there is no obvious segregation, indicating that the distribution of each phase in the heterostructure has good homogeneity.

[0068] Furthermore, the surface chemical states and elemental valence states of the Ni3Cu-Ni(OH)2 / NF heterocatalyst were characterized by X-ray photoelectron spectroscopy (XPS), and the bulk composition was analyzed by plasma sputtering etching (etching depth 10 nm). Full-spectrum scanning showed that the catalyst surface mainly contained Ni, Cu, and O elements. Figure 6 As shown in (a), in the high-resolution Ni 2p spectrum, the peaks at 855.78 eV and 873.98 eV correspond to Ni 2+ (2p 3 / 2 and 2p 1 / 2 The presence of a strong satellite peak at 861.58 eV indicates that surface Ni mainly exists in the form of Ni(OH)2; in the Cu 2p spectrum, the peak at 935.18 eV corresponds to Cu 2+ This indicates that some Cu was oxidized to Cu(OH)2, such as Figure 6As shown in (b); in the O 1s spectrum, the peaks at 531.38 eV and 532.78 eV correspond to M-OH (metallic hydroxyl group) and HOH (adsorbed water), respectively. The hydroxyl oxygen content reaches 90%, indicating that the surface is enriched with a large number of hydroxyl groups, which can enhance the adsorption capacity for water molecules. Figure 6 As shown in (c).

[0069] XPS analysis after 10 nm plasma sputtering etching revealed Ni at 852.48 eV in the bulk Ni 2p spectrum. 0 Peak, like Figure 6 As shown in (d), Cu at 932.38 eV in the Cu 2p spectrum 0 Peak intensity increases, such as Figure 6 As shown in (e), the bulk phase remains a Ni3Cu alloy, ensuring good conductivity of the catalytic electrode; however, the proportion of hydroxyl oxygen in the O1s spectrum decreases slightly, as... Figure 6 As shown in (f), this further confirms that the surface Ni(OH)2 is an in-situ generated thin layer structure that does not penetrate into the bulk phase. The above results indicate that the catalyst surface is a highly active hydroxide phase, and the bulk phase is a highly conductive alloy phase, forming a synergistic structure of "surface active layer-bulk conductive framework".

[0070] Furthermore, the gas-repellency of the Ni3Cu-Ni(OH)2 / NF catalyst was evaluated using bubble contact angle (CA) testing to investigate its interfacial mass transfer capability during high-current hydrogen evolution. The experiment used 1M KOH solution as the liquid phase and hydrogen as the gas phase. The CA of different catalyst surfaces was measured: the CA of the nickel foam (NF) substrate was 114°, the CA of the commercial PtC / NF electrode was 120°, the CAs of single Ni(OH)2 / NF and Cu(OH)2 / NF were 125° and 137°, respectively, the CA of the unoxidized Ni3Cu / NF catalyst was 138°, while the CA of the Ni3Cu-Ni(OH)2 / NF catalyst reached 147°, approaching the superhydrophobic threshold (150°), exhibiting excellent gas-repellent properties. Figure 7 As shown.

[0071] The enhanced gas-repellency stems from the hierarchical dendritic structure and surface chemical properties of the Ni3Cu-Ni(OH)2 / NF heterocatalyst: on the one hand, the rough surface formed by the framework nanoclusters reduces the contact area between bubbles and the electrode, lowering the gas-solid interface energy; on the other hand, the surface-enriched hydroxyl groups interact with water molecules through hydrogen bonds, enhancing hydrophilicity and promoting rapid bubble detachment from the surface. This superhydrophobic property effectively alleviates the adhesion and aggregation of bubbles on the electrode surface under high current, preventing the active sites from being covered and ensuring continuous contact between the electrolyte and the active centers, thereby improving mass transfer efficiency. Combined with the pore structure observed by SEM, the catalytic electrode can achieve a dynamic balance of "rapid bubble detachment - rapid electrolyte replenishment" under high current density, providing a favorable interfacial environment for efficient hydrogen evolution reaction.

[0072] This embodiment confirms through various characterization methods that the Ni3Cu-Ni(OH)2 / NF heterocatalyst was successfully formed with a well-defined crystal structure. Ni(OH)2 is generated on the surface and tightly bonded to the Ni3Cu alloy. Its hierarchical dendritic structure increases the specific surface area, provides uniform elemental distribution, abundant surface hydroxyl groups, maintains the alloy's conductivity in the bulk phase, and its superhydrophobicity facilitates bubble detachment, providing favorable structural and interfacial conditions for efficient hydrogen evolution.

[0073] Based on Example 1, this example details the study of the alkaline hydrogen evolution electrochemical performance of the Ni3Cu-Ni(OH)2 / NF heterocatalyst, specifically as follows:

[0074] The HER performance of different catalysts (Ni3Cu-Ni(OH)2, Ni3Cu, Ni(OH)2, Cu(OH)2, NF, PtC) was tested, such as... Figure 8 As shown, the Ni3Cu-Ni(OH)2 catalyst at 10 mA / cm²... -2 It exhibits high HER activity and a low hydrogen evolution overpotential of 24 mV, such as Figure 8 As shown in (a), it is lower than Ni3Cu (197mV), Ni(OH)2 (230mV), Cu(OH)2 (231mV) and NF (273mV), and close to commercial PtC (21mV). Simultaneously, it achieves a high current density of 1Acm⁻¹. -2 The lower HER activity is outstanding, with a hydrogen evolution overpotential of only 248 mV, far lower than the 420 mV of commercial PtC catalysts; Figure 8 (b) shows its electrochemical impedance spectroscopy Nyquist plot. The minimum semicircle of Ni3Cu-Ni(OH)2 in the plot reveals that Ni3Cu-Ni(OH)2 has a small charge transfer resistance (R0). ct =0.15Ω), indicating that it has a faster electron transfer rate and higher reaction kinetics; such as Figure 8 (c) shows the double-layer capacitor C dlTests show that the C of Ni3Cu-Ni(OH)2 dl 36.69mF cm -2 It is significantly higher than that of Ni(OH)2 (5.28 mF cm⁻¹). -2 Cu(OH)2 (8.77mF cm) -2 ) and Ni3Cu(32.04mF cm -2 This indicates that the Ni3Cu-Ni(OH)2 catalyst has a larger electrochemical active surface area (ECSA; the calculated ECSA of Ni3Cu-Ni(OH)2 is 917 cm²). 2 This can provide more active sites for the HER reaction; such as Figure 8 The performance comparison bar chart shown in (d) visually illustrates different current densities (10, 100, 500, 1000 mA / cm²). -2 The overpotential of each catalyst under different conditions was excellent for Ni3Cu-Ni(OH)2 / NF.

[0075] To further investigate HER dynamics, Tafel analysis was performed in the low current density region, such as... Figure 8 As shown in (e), the Ni3Cu-Ni(OH)2 catalyst exhibits a decimation efficiency of approximately 97 mV. -1 The Tafel slope is significantly lower than that of Ni3Cu (134mV dec). -1 Cu(OH)2 (105mV dec) -1 ), Ni(OH)2 (178mV dec -1 The Ni3Cu-Ni(OH)2 catalyst exhibits a Tafel slope of 97 mV dec at low current densities. -1 This indicates that the Tafel mechanism is still functioning, although its Tafel slope is slightly higher than that of PtC(41mV dec). -1 While the current density is relatively low, it still exhibits good responsiveness at low current densities. More significantly, in the high current region, such as... Figure 8 As shown in (f), the Tafel slope of PtC increases significantly by 273 mV dec. -1 This indicates that the hydrogen evolution efficiency of conventional commercial catalysts at high currents is significantly limited by the Volmer step. For Ni3Cu-Ni(OH)2, the increase in the Tafel slope at high current densities is very small (only 5 mV dec). -1This indicates that under high current density, the Ni3Cu-Ni(OH)2 catalyst can effectively transform into a reaction mechanism dominated by the Volmer step, and the adsorption and dissociation of water is no longer a limiting factor. Therefore, the performance advantage of Ni3Cu-Ni(OH)2 under high current density is very obvious, indicating that it has better stability and durability under practical application conditions.

[0076] In industrial current applications, catalyst durability is a key factor in evaluating its performance. For catalysts designed to adapt to industrial currents, stable and sustained catalytic performance is crucial. This study employed a chronopotentiometric method to continuously monitor the potential changes of the catalyst in a three-electrode test system, with Hg / HgO as the reference electrode. The test environment was set at 30°C in a 1M KOH solution, with a potential of up to 500 mA cm⁻¹. -2 Durability tests were conducted on the Ni3Cu-Ni(OH)2 / NF catalyst at industrial-grade high current densities, such as... Figure 9 As shown;

[0077] Experimental results show that the hydrogen evolution overpotential did not fluctuate significantly during the 1600-hour test period. After 1600 hours of testing, the overpotential only showed a slight increase of 25 mV. This result fully demonstrates that the Ni3Cu-Ni(OH)2 / NF catalyst can maintain stable activity and possess good durability even under the harsh conditions of high current density in industrial applications. Compared with reported advanced alkaline high-current hydrogen evolution catalysts, as shown in Table 1, the Ni3Cu-Ni(OH)2 / NF catalyst exhibits excellent performance, providing strong support for its industrial current applications.

[0078] Table 1. Performance comparison of Ni3Cu-Ni(OH)2 / NF with reported advanced alkaline high-current hydrogen evolution catalysts.

[0079]

[0080] like Figure 10 As shown in Table 2, the microstructure of the catalyst before and after aging was observed. The framework morphology remained the same, the size of the nanoparticles on the surface did not change much, and nanosheets grew uniformly on the surface. The changes in elemental content before and after the stability test were tested by EDS. As shown in Table 2, the O element content increased, indicating that the bulk alloy partially reconstructed to form hydroxides.

[0081] Table 2. Changes in elemental content before and after stability testing of Ni3Cu-Ni(OH)2 / NF

[0082]

[0083] XPS tests were performed on the Ni3Cu-Ni(OH)2 / NF heterocatalyst before and after aging to determine the changes in surface valence states, such as... Figure 11 As shown, the comparison revealed that the valence state of Ni 2p and the corresponding oxidation peak content remained unchanged, while the valence state of Cu 2p remained unchanged, but the corresponding peak intensity showed a slight decrease. The content of O 1s hydroxyl oxygen increased slightly. XPS tests showed that the surface chemical state of the Ni3Cu-Ni(OH)2 / NF catalyst was stable.

[0084] This embodiment details the excellent performance of the Ni3Cu-Ni(OH)2 / NF heterocatalyst in alkaline hydrogen evolution. It has a large electrochemical active surface area, providing abundant active sites, low charge transfer resistance, rapid electron transfer, good reaction kinetics under high current, unrestricted water dissociation, stable structure and chemical state after long-term operation, good gas-repellent properties, easy bubble removal, ensuring mass transfer efficiency, and its comprehensive performance meets the requirements of high-current industrial applications.

[0085] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter changes made to these embodiments within the spirit and principles of the present invention, without departing from the principles and spirit of the present invention, through conventional substitutions or to achieve the same function, fall within the scope of protection of the present invention.

Claims

1. A Ni3Cu-Ni(OH)2 heterogeneous catalyst for high-current hydrogen evolution, comprising a nickel foam substrate, exhibiting an overall framework nanocluster edge multi-level dendritic structure, formed by the stacking of nanoparticles to form small clusters, with the framework edge being a three-dimensional dendritic hierarchical structure; the surface forms a heterogeneous structure of Ni3Cu alloy and Ni(OH)2, wherein Ni(OH)2 grows on the edge of Ni3Cu alloy, and the microstructure shows that its internal lattice stripes correspond to Ni3Cu crystal planes, and the external stripes correspond to Ni(OH)2 crystal planes; the Ni, Cu, and O elements are uniformly distributed on the surface of the catalyst material; and the surface is induced to enrich interfacial water molecules for directional adsorption with weak hydrogen bond configuration.

2. The Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 1, characterized in that, The molar ratio of Ni:Cu in the Ni3Cu alloy is 3:1, which is achieved by adjusting the concentrations of NiSO4·6H2O and CuSO4 in the plating solution during the electrodeposition process.

3. The Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 1, characterized in that, The Ni(OH)2 in the composite phase is generated by in-situ electrochemical CV oxidation etching of Ni3Cu / NF, with an oxidation range of 0.9-1.6 V vs. RHE, and is carried out under 30°C water bath conditions; the coverage of Ni(OH)2 is 30-50%, which is achieved by controlling the number of electrochemical oxidation cycles, with the optimized number of oxidation cycles being 10 cycles.

4. A method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution, applicable to the Ni3Cu-Ni(OH)2 heterocatalyst described in claims 1-3, specifically comprising: S1. Pre-treat the nickel foam substrate, including ultrasonically removing oil stains from the surface of the nickel foam in acetone, cleaning it, ultrasonically treating it in HCl solution, cleaning it after treatment, and then ultrasonically cleaning it in anhydrous ethanol to obtain the pre-treated nickel foam. S2. Preparation of Ni3Cu / NF catalyst: The prepared electroplating buffer and metal source were added to a beaker and magnetically stirred to form an electroplating solution. A three-electrode system was used, with pretreated nickel foam as the working electrode, polished nickel sheet as the counter electrode, and Ag / AgCl dual salt bridge electrode as the reference electrode. Constant current electrodeposition was performed on an Autolab electrochemical workstation. After electroplating, the catalyst was cleaned with ethanol and deionized water and dried in a vacuum drying oven to obtain Ni3Cu / NF. S3. Preparation of Ni3Cu-Ni(OH)2 / NF heterostructure catalyst: Using Ni3Cu / NF as a precursor, in-situ electrochemical oxidation etching was performed in KOH electrolyte using a three-electrode system. The working electrode was a Ni3Cu / NF electrode, the counter electrode was a graphite sheet, and the reference electrode was a Hg / HgO electrode. CV oxidation was performed on an Autolab electrochemical workstation under constant temperature in a water bath. After oxidation, the catalyst was cleaned with ethanol and deionized water and dried in a vacuum drying oven to obtain the Ni3Cu-Ni(OH)2 / NF heterostructure catalyst.

5. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 4, characterized in that, In the plating solution prepared in S2, the electroplating buffer is selected from one or more of K4P2O7, C2H5NO2, CH4N2O, and C6H5N3; the metal source is selected from one or more of NiSO4·6H2O and CuSO4.

6. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 4, characterized in that, During constant current electrodeposition in S2, the spacing between the three electrodes is controlled to be 2-3 cm, and the immersion area of ​​the working electrode is 1-2 cm². 2 One side of the nickel foam participates in the reaction. Before electrodeposition, the plating solution needs to be deoxygenated with nitrogen. During the electrodeposition process, the potential change of the working electrode is recorded every preset time period to keep the potential fluctuation not exceeding ±5mV.

7. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 4, characterized in that, The deposition current density of the constant current electrodeposition is 250-280 mA / cm². -2 The deposition time is 600-750s, and the deposition temperature is controlled at 30±1℃. During the electrodeposition process, the current output accuracy of the Autolab electrochemical workstation is ±1mA, and the plating solution is continuously stirred at a stirring rate of 300-400rpm to ensure uniform concentration of the plating solution.

8. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 1, characterized in that, The 1M KOH electrolyte used in the in-situ electrochemical oxidation etching in S3 is prepared by dissolving pure KOH in ultrapure water and removing air bubbles. The volume of the KOH electrolyte is 10-15 times the volume of the working electrode. Meanwhile, the Hg / HgO reference electrode needs to be activated in 1M KOH before use.

9. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 1, characterized in that, In S3, CV oxidation is performed on an Autolab electrochemical workstation using a water bath at a constant temperature. The oxidation control method is as follows: the start potential and end potential of the CV scan are set, the scan rate is set, and after reaching the set end potential, one scan is completed, and the scan is paused for a preset time before the next scan is performed, until the preset number of scans is completed and the oxidation is completed.

10. The method for preparing a Ni3Cu-Ni(OH)2 heterocatalyst for high-current hydrogen evolution according to claim 1, characterized in that, The cleaning process employs centrifugal cleaning at a speed of 3000-4000 rpm for 3-5 minutes each time. After centrifugation, the waste liquid is poured out, and new solvent is added for the next cleaning cycle.

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