A nickel-cobalt double metal sulfide catalyst, a preparation method and application thereof

Abstract

The present application relates to a kind of nickel-cobalt bimetallic sulfide catalyst and its preparation method and application.Preparation method includes the following steps: using three electrode system, with foam nickel substrate as working electrode, in the electrolyte containing cobalt source and sulfur source electrochemical deposition, precursor is obtained;The precursor is calcined, and nickel-cobalt bimetallic sulfide catalyst is obtained.The preparation method provided by the present application, by introducing sulfur source and cobalt source electrochemical deposition and calcination, successfully realized the nickel-cobalt bimetallic sulfide is supported on the surface of foam nickel substrate, and in the alkaline environment electrocatalytic oxygen evolution reaction shows excellent catalytic activity and catalytic stability, the overpotential under high current density can be reduced to 620mV below, and the length of time that can be stably operated is as high as 2100h.Electrochemical deposition can also omit binder, realize the good combination of nickel-cobalt bimetallic sulfide and foam nickel substrate, avoid binder to shield active site, it is favorable to further improve the catalytic activity of catalyst.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen production by water electrolysis, and relates to a catalyst for the electrocatalytic oxygen evolution reaction, particularly a nickel-cobalt bimetallic sulfide catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen production via water electrolysis powered by renewable energy can achieve "zero carbon emissions and zero pollution" throughout its entire lifecycle, making it a core technological pathway for reducing industrial emissions and improving air quality at the source. However, the widespread application of this technology currently faces significant bottlenecks: the sluggish kinetics of the electrocatalytic oxygen evolution reaction at the anode and the lack of low-cost electrode materials capable of long-term stable operation under high industrial current density conditions.

[0003] In the electrocatalytic oxygen evolution reaction, noble metal oxides such as ruthenium and iridium exhibit excellent catalytic activity. However, ruthenium is prone to over-oxidation and dissolution under high voltage conditions; although iridium has better stability, all noble metal nanocatalysts will experience particle sintering and agglomeration under high current density and strong oxidizing environment, resulting in a reduction of active sites and a decrease in catalytic efficiency. Wang et al. (Angewandte Chemie International Edition, 2025 Jun 2; 64(23):e202503608) used Ru-RuO2 / C 60-x As a catalyst, although at 10 mA / cm 2 The overpotential at current density is only 194mV, but at 65mA / cm 2 At relatively low current densities, it can only operate stably for 200 hours, which is insufficient to meet the stringent requirements of large-scale water electrolysis. Therefore, improving catalyst reactivity and reducing costs have become the primary issues to be addressed.

[0004] CN121407124A discloses a method for preparing a composite electrode for hydrogen production by water electrolysis based on a zwitterionic polymer binder. This method uses the zwitterionic polymer PSBMA to replace the traditional ionic binder Nafion, and coats the electrode substrate surface with NiFe LDH. Its unique electrically neutral hydration layer structure optimizes the electrode / electrolyte interface, enhances bubble desorption behavior, and promotes the transport of reactive ions. However, because the active components are still bound to the electrode substrate through the binder, some active sites are physically shielded, making it difficult for the generated gas to be released in a timely manner. This causes the gas to accumulate and merge on the surface, eventually forming a gas film covering layer that completely blocks the contact between the active sites and the electrolyte, thus affecting its catalytic activity.

[0005] Therefore, how to develop catalysts for the electrocatalytic oxygen evolution reaction that combine high activity, high stability, and cost-effectiveness is an urgent problem to be solved in the field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a nickel-cobalt bimetallic sulfide catalyst, its preparation method, and its applications. The preparation method provided by this invention enables the direct loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate, achieving excellent bonding between the nickel-cobalt bimetallic sulfides and the nickel foam substrate. This avoids the physical obscuring of active sites by the addition of binders during powder material preparation, and exhibits excellent catalytic activity and stability in the electrocatalytic oxygen evolution reaction under alkaline conditions.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, comprising the following steps: using a three-electrode system, with a first foamed nickel as the working electrode, electrochemical deposition is performed in an electrolyte containing a cobalt source and a sulfur source to obtain a precursor; the precursor is calcined to obtain the nickel-cobalt bimetallic sulfide catalyst.

[0009] The preparation method provided by this invention, through electrochemical deposition and calcination using sulfur and cobalt sources, achieves the loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate. This results in excellent catalytic activity and stability for the electrocatalytic oxygen evolution reaction in an alkaline environment. The overpotential at high current density can be reduced to below 620 mV, with a minimum of 450 mV, and stable operation can last up to 2100 hours. Furthermore, the electrochemical deposition method allows for good bonding between the nickel-cobalt bimetallic sulfides and the nickel foam substrate without the need for a binder, avoiding physical obscuring of active sites by the binder and thus further enhancing the catalyst's catalytic activity.

[0010] This invention achieves the loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate by introducing a sulfur source during the electrochemical deposition process. On the one hand, nickel-cobalt bimetallic sulfides possess excellent conductivity, providing an ideal channel for rapid electron transfer and quickly transporting charge to the surface, thereby enhancing the catalytic activity of the catalyst. On the other hand, nickel-cobalt bimetallic sulfides undergo surface electrochemical oxidation and reconstruction in an alkaline environment, forming a thin, defect-rich active layer of nickel-cobalt bimetallic hydroxide in situ on their surface. The heterogeneous structure of hydroxide and sulfide further enhances the catalytic activity of the catalyst.

[0011] The slow dissolution kinetics of nickel foam limit the local Ni concentration in the electrolyte. 2+The high concentration of nickel sulfides and the high energy barrier for uniform nucleation further hinder the formation of their crystalline products. This invention addresses these two limitations through a dual kinetic and thermodynamic mechanism by introducing a cobalt source with redox capabilities during electrochemical deposition. On the one hand, it contains Co during electrochemical deposition. 2+ / Co 3+ The redox cycle, while Co 3+ Nickel (2Co) can be chemically etched. 3+ +Ni→2Co 2+ +Ni 2 + Bypassing the slow dissolution kinetics, thus ensuring rapid, localized Ni 2+ On the one hand, the initially formed cobalt sulfide can act as a heterogeneous nucleation site, greatly reducing the critical nucleation barrier of nickel sulfides, thereby promoting the epitaxial growth of crystalline nickel sulfides. Based on this, the foamed nickel substrate in this invention can simultaneously serve as a conductive substrate and a nickel source, while omitting the addition of a nickel source in the electrolyte can reduce production costs.

[0012] This invention, by calcining the precursor, can not only strengthen the nanosheet structure of nickel-cobalt bimetallic sulfide to form a uniformly stacked nanosheet array, but also enhance the adhesion between the nickel-cobalt bimetallic sulfide and the foamed nickel substrate, thereby enhancing the structural stability of the catalyst and further improving its catalytic stability.

[0013] Preferably, the cobalt source includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride. Typical but non-limiting combinations include combinations of cobalt sulfate and cobalt nitrate, cobalt nitrate and cobalt chloride, cobalt sulfate and cobalt chloride, and combinations of cobalt sulfate, cobalt nitrate, and cobalt chloride, with cobalt sulfate being the most preferred.

[0014] Preferably, the concentration of the cobalt source in the electrolyte is 0.025 mol / L to 0.075 mol / L, for example, it can be 0.025 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L or 0.075 mol / L, etc.

[0015] Preferably, the sulfur source includes any one or a combination of at least two of thiourea, thioacetamide, or dithiooxazone. Typical but non-limiting combinations include combinations of thiourea and thioacetamide, combinations of thioacetamide and dithiooxazone, combinations of thiourea and dithiooxazone, and combinations of thiourea, thioacetamide, and dithiooxazone, with thiourea being the most preferred.

[0016] Preferably, the concentration of the sulfur source in the electrolyte is 0.25 mol / L to 0.75 mol / L, for example, it can be 0.25 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L or 0.75 mol / L, etc.

[0017] Preferably, the electrochemical deposition method is cyclic voltammetry.

[0018] Preferably, the voltage range of the electrochemical deposition is -2.0V to 1.0V (vs. SCE).

[0019] It should be noted that the voltage range for electrochemical deposition is -2.0V to 1.0V (vs. SCE), which means that the negative potential does not exceed -2.0V and the positive potential does not exceed 1.0V. For example, it can be -2.0V to 1.0V, -1.0V to 0.5V, -2.0V to 0.8V, -1.2V to 0.2V, etc.

[0020] In this invention, the preferred voltage range for electrochemical deposition is -2.0V to 1.0V. If the negative potential is too high, such as selecting a voltage range of -3.0V to 0V for deposition, the hydrogen evolution reaction on the electrode surface will be significantly aggravated, and a large number of hydrogen bubbles will destroy the compactness of the deposition layer, resulting in a loose or even pulverized structure of the catalyst, reducing the bonding force with the substrate, thereby reducing the catalytic activity. If the positive potential is too high, such as selecting a voltage range of 0V to 3.0V for deposition, the working electrode substrate itself may undergo irreversible oxidation and dissolution, resulting in a decrease in loading and compositional deviation, thereby weakening the catalytic activity.

[0021] Preferably, the scan rate of the electrochemical deposition is 0.1 mV / s to 120 mV / s, for example, it can be 0.1 mV / s, 0.5 mV / s, 1 mV / s, 5 mV / s, 10 mV / s, 20 mV / s, 50 mV / s, 100 mV / s or 120 mV / s, etc.

[0022] In this invention, the scanning rate of electrochemical deposition is preferably 0.1 mV / s to 120 mV / s. If the scanning rate is too high and the deposition time is too short, the catalyst loading will be low, thereby reducing the catalytic performance. If the scanning rate is too low and the deposition time is too long, the catalyst will agglomerate and cannot form a nanoarray structure, thereby reducing the catalytic performance.

[0023] Preferably, the number of scans for the electrochemical deposition is 20 to 50, for example, 20, 25, 30, 35, 40, 45, or 50 scans.

[0024] In this invention, the number of scans for electrochemical deposition is preferably 20 to 50. If the number of scans is too small, the catalyst loading will be low; if the number of scans is too large, the catalyst will agglomerate, reduce the catalyst mass transfer rate, and reduce the catalytic performance.

[0025] Preferably, the calcination is carried out under a protective atmosphere.

[0026] Preferably, the protective atmosphere includes nitrogen and / or argon.

[0027] Preferably, the calcination temperature is 200℃~300℃, for example, it can be 200℃, 220℃, 240℃, 250℃, 260℃, 280℃ or 300℃, etc.

[0028] In this invention, the preferred calcination temperature is 200℃~300℃. At this temperature, the nickel foam substrate can be uniformly covered by the nanosheet array of nickel-cobalt bimetallic sulfide without obvious cracks. The adhesion between the nickel-cobalt bimetallic sulfide and the nickel foam substrate is strong, which can greatly enhance mechanical stability and anti-peeling performance. If the calcination temperature is too low, although the nickel-cobalt bimetallic sulfide can form a stacked nanosheet array, the nickel foam substrate will develop grooves and cracks, making it prone to peeling under high current density and bubble impact. If the calcination temperature is too high, the nanosheet array of nickel-cobalt bimetallic sulfide will undergo severe sintering and agglomeration, forming a granular interconnected morphology. At the same time, the mechanical strength of the nickel foam substrate will also decrease, making it brittle and prone to fracture.

[0029] Preferably, the calcination holding time is 2h to 10h, for example, it can be 2h, 4h, 5h, 6h, 8h, 10h or 12h.

[0030] Preferably, the heating rate of the calcination is 1℃ / min to 10℃ / min, for example, it can be 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min or 10℃ / min, etc.

[0031] Preferably, the preparation method further includes pretreatment of the first nickel foam before electrochemical deposition: placing the first nickel foam in an acid solution for ultrasonic cleaning.

[0032] This invention uses an acid solution to ultrasonically clean a nickel foam substrate, which removes the oxide layer and impurities on the surface of the nickel foam substrate, ensuring the cleanliness and conductivity of the nickel foam substrate, and laying the foundation for subsequent electrochemical deposition of nickel-cobalt bimetallic sulfides.

[0033] Preferably, the acid solution includes any one or a combination of at least two of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution. Typical but non-limiting combinations include a combination of hydrochloric acid solution and sulfuric acid solution, a combination of sulfuric acid solution and nitric acid solution, a combination of hydrochloric acid solution and nitric acid solution, or a combination of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution.

[0034] Preferably, the concentration of the acid solution is 2 mol / L to 4 mol / L, for example, it can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L, etc.

[0035] Preferably, the ultrasonic cleaning time is 10 min to 30 min, for example, it can be 10 min, 15 min, 20 min, 25 min or 30 min.

[0036] Preferably, the three-electrode system further includes a counter electrode and a reference electrode.

[0037] It should be noted that electrochemical deposition was performed using a Gamry electrochemical workstation and its three-electrode system. The working electrode, connected to the workstation's WE interface, is the primary object of study and operation, serving as the main site for chemical reactions such as metal corrosion, battery charging and discharging, or catalytic reactions. The working electrode material must be chemically inert (not reacting with the electrolyte), have a uniform and smooth surface, a wide potential window, and be easy to clean. The counter electrode, connected to the workstation's CE interface, forms a current loop with the working electrode, carrying the polarization current to ensure continuous reaction. The counter electrode material is typically made of inert materials (such as platinum or carbon rods) and should have a large surface area to reduce polarization. The reference electrode, connected to the workstation's RE interface, provides a stable potential reference (such as a Hg / HgO electrode, silver / silver chloride electrode, or saturated calomel electrode). The reference electrode itself carries almost no current, avoiding polarization interference; its core function is to provide a stable and repeatable reference potential, ensuring accurate measurement of the working electrode potential.

[0038] Preferably, the counter electrode comprises a second nickel foam and / or a platinum sheet, with the second nickel foam being more preferred.

[0039] Preferably, the reference electrode comprises a saturated calomel electrode and / or a silver / silver chloride electrode.

[0040] Preferably, the preparation method includes the following steps:

[0041] S1. Pretreatment of the first foamed nickel: The first foamed nickel is placed in an acid solution for ultrasonic cleaning; wherein, the acid solution includes any one or a combination of at least two of hydrochloric acid solution, sulfuric acid solution or nitric acid solution; the concentration of the acid solution is 2 mol / L to 4 mol / L; the ultrasonic cleaning time is 10 min to 30 min.

[0042] S2. A three-electrode system is used, with the pretreated first foamed nickel as the working electrode, to perform electrochemical deposition in an electrolyte containing a cobalt source and a sulfur source to obtain the precursor; wherein, the cobalt source includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride, and the concentration of the cobalt source is 0.025 mol / L to 0.075 mol / L; the sulfur source includes any one or a combination of at least two of thiourea, thioacetamide, or dithiooxazone, and the concentration of the sulfur source is 0.25 mol / L to 0.75 mol / L; the electrochemical deposition method is cyclic voltammetry, the voltage range of the electrochemical deposition is -2.0V to 1.0V, the scan rate of the electrochemical deposition is 0.1 mV / s to 120 mV / s, and the number of scan cycles of the electrochemical deposition is 20 to 50 cycles.

[0043] S3. The precursor is calcined to obtain the nickel-cobalt bimetallic sulfide catalyst; wherein the calcination is carried out under a nitrogen and / or argon atmosphere, the calcination temperature is 200℃~300℃, the calcination holding time is 0.5h~12h, and the calcination heating rate is 1℃ / min~10℃ / min.

[0044] In a second aspect, the present invention provides a nickel-cobalt bimetallic sulfide catalyst, which is prepared by the preparation method described in the first aspect; the nickel-cobalt bimetallic sulfide catalyst comprises a nickel foam substrate and nickel-cobalt bimetallic sulfides supported on the surface of the nickel foam substrate.

[0045] This invention loads nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate. On one hand, nickel-cobalt bimetallic sulfides possess excellent conductivity, providing an ideal channel for rapid electron transfer and facilitating rapid charge transport to the surface, thereby enhancing the catalytic activity of the catalyst. On the other hand, nickel-cobalt bimetallic sulfides undergo surface electrochemical oxidation and reconstruction in an alkaline environment, forming a thin, defect-rich active layer of nickel-cobalt bimetallic hydroxide in situ. The heterogeneous structure of hydroxide and sulfide further enhances the catalytic activity. Furthermore, the nanosheet structure of nickel-cobalt bimetallic sulfides can form a uniformly stacked nanosheet array, and the strong adhesion between the nickel-cobalt bimetallic sulfides and the nickel foam substrate enhances the structural stability and catalytic stability of the catalyst.

[0046] Thirdly, the present invention provides an application of the nickel-cobalt bimetallic sulfide catalyst as described in the second aspect, wherein the nickel-cobalt bimetallic sulfide catalyst is applied to the electrocatalytic oxygen evolution reaction in an alkaline environment.

[0047] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The preparation method provided by this invention, through electrochemical deposition and calcination using sulfur and cobalt sources, achieves the loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate. This results in excellent catalytic activity and stability for the electrocatalytic oxygen evolution reaction in an alkaline environment. The overpotential at high current density can be reduced to below 620 mV, with a minimum of 450 mV, and stable operation can last up to 2100 hours. Furthermore, the electrochemical deposition method allows for good bonding between the nickel-cobalt bimetallic sulfides and the nickel foam substrate without the need for a binder, avoiding physical obscuring of active sites by the binder and thus further enhancing the catalyst's catalytic activity.

[0050] This invention achieves the loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate by introducing a sulfur source during the electrochemical deposition process. On the one hand, nickel-cobalt bimetallic sulfides possess excellent conductivity, providing an ideal channel for rapid electron transfer and quickly transporting charge to the surface, thereby enhancing the catalytic activity of the catalyst. On the other hand, nickel-cobalt bimetallic sulfides undergo surface electrochemical oxidation and reconstruction in an alkaline environment, forming a thin, defect-rich active layer of nickel-cobalt bimetallic hydroxide in situ on the surface. The heterogeneous structure of hydroxide and sulfide further enhances the catalytic activity of the catalyst.

[0051] The slow dissolution kinetics of nickel foam limit the local Ni concentration in the electrolyte. 2+ The high concentration of nickel sulfides and the high energy barrier for uniform nucleation further hinder the formation of their crystalline products. This invention addresses these two limitations through a dual kinetic and thermodynamic mechanism by introducing a cobalt source with redox capabilities during electrochemical deposition. On the one hand, it contains Co during electrochemical deposition. 2+ / Co 3+ The redox cycle, while Co 3+ Nickel (2Co) can be chemically etched. 3+ +Ni→2Co 2+ +Ni 2 + Bypassing the slow dissolution kinetics, thus ensuring rapid, localized Ni 2+On the one hand, the initially formed cobalt sulfide can act as a heterogeneous nucleation site, greatly reducing the critical nucleation barrier of nickel sulfides, thereby promoting the epitaxial growth of crystalline nickel sulfides. Based on this, the foamed nickel substrate in this invention can simultaneously serve as a conductive substrate and a nickel source, while omitting the addition of a nickel source in the electrolyte can reduce production costs.

[0052] This invention, by calcining the precursor, can not only strengthen the nanosheet structure of nickel-cobalt bimetallic sulfide to form a uniformly stacked nanosheet array, but also enhance the adhesion between the nickel-cobalt bimetallic sulfide and the foamed nickel substrate, thereby enhancing the structural stability of the catalyst and further improving its catalytic stability. Attached Figure Description

[0053] Figure 1 These are the cyclic voltammetry curves of the electrochemical deposition process in Example 1 of this invention.

[0054] Figure 2 These are SEM images of the nickel-cobalt bimetallic sulfide catalysts in Examples 1, 10, and 11 of this invention and the catalyst in Comparative Example 4.

[0055] Figure 3 The nickel-cobalt bimetallic sulfide catalyst in Example 1 of this invention is at 1 A / cm 2 Catalytic stability test curves of electrocatalytic oxygen evolution reaction in alkaline environment under high current density. Detailed Implementation

[0056] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0057] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0058] Unless otherwise specified, the term "at least two combinations" in this invention refers to a quantity greater than or equal to 2. For example, "any one or at least two combinations" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention.

[0059] In this invention, unless otherwise specified, the feature or solution corresponding to "and / or" covers any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a set consisting of A, B, and combinations of A and B. "Including A and / or B" can be understood, depending on the context of the statement, as including A, including B, or simultaneously including both A and B. In this invention, "optional" means that the corresponding feature, component, step, or solution is not essential, i.e., selected from either "present" or "absent" parallel solutions. If multiple "optional" limitations appear in a technical solution, unless otherwise specified and without technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0060] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A may consist only of a1, a2, and a3, or it may include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements."

[0061] All embodiments and optional embodiments of the present invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of the present invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment or implementation of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described in this invention can be combined with other embodiments without technical conflict.

[0062] In this invention, the ordinal numbers “first,” “second,” “third,” and “fourth” used in expressions such as “first aspect,” “second aspect,” “third aspect,” and “fourth aspect” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0063] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0064] Example 1

[0065] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, including the following steps:

[0066] (1) Cut two pieces of nickel foam into standard sizes of 1cm×1.2cm, place them in 2.4mol / L hydrochloric acid solution and ultrasonically clean for 10min, then rinse with deionized water and anhydrous ethanol alternately and dry for later use.

[0067] (2) A three-electrode system (pretreated first foam nickel as working electrode, pretreated second foam nickel as counter electrode, and saturated calomel electrode as reference electrode) was used to perform electrochemical deposition in the electrolyte. After electrochemical deposition, the precursor was rinsed with deionized water and dried at 50°C for 2 hours to obtain the precursor. The electrolyte was a mixed aqueous solution containing cobalt sulfate and thiourea, with a cobalt sulfate concentration of 0.05 mol / L and a thiourea concentration of 0.5 mol / L. The electrochemical deposition method was cyclic voltammetry, with a voltage range of -2.0 to 1.0 V (vs. SCE), a scan rate of 10 mV / s, and 20 scan cycles.

[0068] (3) The precursor was placed in a tube furnace and heated to 300°C at a heating rate of 5°C / min under a nitrogen atmosphere and held for 2 hours to obtain a nickel-cobalt bimetallic sulfide catalyst.

[0069] Figure 1 This is the cyclic voltammetry curve of the electrochemical deposition process in this embodiment. It can be seen that the cyclic voltammetry curve has obvious redox peaks, indicating that cobalt ions are present in the Co during the electrochemical deposition process. 2+ / Co 3+ The redox cycle. And the Co produced by this redox cycle... 3+ Nickel (2Co) can be chemically etched. 3+ +Ni→2Co 2+ +Ni 2+ Bypassing the slow dissolution kinetics, thus ensuring rapid, localized Ni 2+ The supply allows the foamed nickel substrate to serve as both a conductive substrate and a nickel source, thus eliminating the need for adding a nickel source to the electrolyte and reducing production costs.

[0070] Example 2

[0071] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, including the following steps:

[0072] (1) After cutting the first foam nickel into a standard size of 1cm×1.2cm, place it in a 2mol / L sulfuric acid solution for ultrasonic cleaning for 30min, then rinse it alternately with deionized water and anhydrous ethanol and dry it for later use.

[0073] (2) A three-electrode system (pretreated first foam nickel as the working electrode, platinum sheet as the counter electrode, and silver-silver chloride electrode as the reference electrode) was used to perform electrochemical deposition in the electrolyte. After electrochemical deposition, the precursor was rinsed with deionized water and dried at 50°C for 2 hours to obtain the precursor. The electrolyte was a mixed aqueous solution containing cobalt nitrate and thioacetamide, with a cobalt nitrate concentration of 0.025 mol / L and a thioacetamide concentration of 0.75 mol / L. The electrochemical deposition method was cyclic voltammetry, with a voltage range of -2.0~1.0V (vs. SCE), a scan rate of 0.1 mV / s, and 30 scan cycles.

[0074] (3) The precursor was placed in a tube furnace and heated to 200°C at a heating rate of 1°C / min under an argon atmosphere and held for 10 h to obtain a nickel-cobalt bimetallic sulfide catalyst.

[0075] Example 3

[0076] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, including the following steps:

[0077] (1) Cut two pieces of nickel foam into standard sizes of 1cm×1.2cm, place them in 4mol / L nitric acid solution for ultrasonic cleaning for 20min, then rinse them alternately with deionized water and anhydrous ethanol and dry them for later use.

[0078] (2) A three-electrode system (the first foamed nickel after pretreatment is the working electrode, the second foamed nickel after pretreatment is the counter electrode, and the saturated calomel electrode is the reference electrode) was used to perform electrochemical deposition in the electrolyte. After the electrochemical deposition was completed, the precursor was rinsed with deionized water and dried at 50°C for 2 hours to obtain the precursor. The electrolyte was a mixed aqueous solution containing cobalt chloride and dithiooxazone, with a cobalt chloride concentration of 0.075 mol / L and a dithiooxazone concentration of 0.25 mol / L. The electrochemical deposition method was cyclic voltammetry, with a voltage range of -2.0~1.0V (vs. SCE), a scan rate of 120 mV / s, and 50 scan cycles.

[0079] (3) The precursor was placed in a tube furnace and heated to 250°C at a rate of 10°C / min under a nitrogen atmosphere and held for 5 hours to obtain a nickel-cobalt bimetallic sulfide catalyst.

[0080] Example 4

[0081] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the voltage range for electrochemical deposition is -3.0V to 0V (vs. SCE).

[0082] Example 5

[0083] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the voltage range for electrochemical deposition is 0V~3.0V (vs. SCE).

[0084] Example 6

[0085] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the scan rate for electrochemical deposition is 0.05 mV / s.

[0086] Example 7

[0087] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the scan rate for electrochemical deposition is 200 mV / s.

[0088] Example 8

[0089] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the number of scans for electrochemical deposition is 10.

[0090] Example 9

[0091] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the number of scans for electrochemical deposition is 60.

[0092] Example 10

[0093] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the calcination temperature is 100°C.

[0094] Example 11

[0095] This embodiment provides a method for preparing a nickel-cobalt bimetallic sulfide catalyst, which is the same as in Example 1 except that the calcination temperature is 400°C.

[0096] Comparative Example 1

[0097] This comparative example provides a method for preparing a catalyst, which is the same as in Example 1 except that steps (2) and (3) are omitted.

[0098] Comparative Example 2

[0099] This comparative example provides a method for preparing a catalyst, which is the same as in Example 1 except that cobalt sulfate is not added to the electrolyte in step (2).

[0100] Comparative Example 3

[0101] This comparative example provides a method for preparing a catalyst, except that thiourea is not added to the electrolyte in step (2), and equal masses of thiourea are mixed with the precursor and calcined in step (3). Otherwise, it is the same as in Example 1.

[0102] Comparative Example 4

[0103] This comparative example provides a method for preparing a catalyst, which is the same as in Example 1 except that step (3) is omitted.

[0104] Figure 2 These are SEM images of the nickel-cobalt bimetallic sulfide catalysts from Examples 1, 10, and 11, and the catalyst from Comparative Example 4. From... Figure 2 As can be seen, in Example 1, calcining the precursor at 300°C strengthens the nanosheet structure of nickel-cobalt bimetallic sulfide, forming a uniformly stacked nanosheet array that uniformly covers the nickel foam substrate, and the nickel foam substrate has no obvious cracks, which is beneficial to increasing the specific surface area and exposing more active sites. In Example 10, due to the excessively low calcination temperature, although the nickel-cobalt bimetallic sulfide can form a stacked nanosheet array, the nickel foam substrate will produce grooves and cracks. In Example 11, due to the excessively high calcination temperature, the nanosheet array of nickel-cobalt bimetallic sulfide will undergo severe sintering and agglomeration, forming a granular interconnected morphology, which will reduce the specific surface area and reduce the number of active sites. In Comparative Example 4, since the precursor is not calcined, although the nickel-cobalt bimetallic sulfide has a nanosheet structure, it does not form a uniformly stacked nanosheet array, which will reduce the specific surface area and reduce the number of active sites.

[0105] Using the nickel-cobalt bimetallic sulfide catalysts provided in Examples 1-11 and the catalysts provided in Comparative Examples 1-4 as working electrodes, a carbon rod as the counter electrode, and an Hg / HgO electrode as the reference electrode, a three-electrode system was constructed. The system was tested in a 1 mol / L potassium hydroxide electrolyte at a constant scan rate of 5 mV / s at an A / cm² depth. 2 The catalytic activity of the electrocatalytic oxygen evolution reaction in an alkaline environment at current density is expressed as overpotential.

[0106] The test results are shown in Table 1.

[0107]

[0108] As can be seen from Table 1, the nickel-cobalt bimetallic sulfide catalysts provided in Examples 1 to 3 achieve a performance of 1 A / cm². 2 The low overpotential at high current densities indicates that it has excellent catalytic activity for the electrocatalytic oxygen evolution reaction in alkaline environments.

[0109] Compared to Example 1, Examples 4 through 9 adjusted the voltage range, scan rate, and number of scan cycles for electrochemical deposition, respectively, at 1 A / cm. 2 The overpotential increased under high current density. This is because: when the voltage range window remains constant, excessively high negative voltages lead to intensified hydrogen evolution reaction, resulting in loose dendrite formation of the deposited layer; excessively high positive voltages cause partial dissolution of the deposited material due to substrate oxidation. When the scan rate is too slow, the deposition time is too long, easily leading to side reactions or the formation of dense, thick layers, reducing the specific surface area; when the scan rate is too fast, ion diffusion is restricted, resulting in uneven deposition and poor bonding. When the number of scan cycles is too small, the catalyst loading is insufficient, and active sites are scarce; when the number of scan cycles is too large, the deposited layer becomes too thick, easily cracking and detaching, internal diffusion is hindered, and activity decreases.

[0110] Compared with Example 1, Examples 10 and 11 adjusted the calcination temperature to 1 A / cm. 2 The overpotential also increased under high current density. This is because: if the calcination temperature is too low, although nickel-cobalt bimetallic sulfides can form stacked nanosheet arrays, the foamed nickel substrate will produce grooves and cracks, making it easy to peel off under high current density and bubble impact, thus affecting its catalytic activity; if the calcination temperature is too high, the nanosheet array of nickel-cobalt bimetallic sulfides will undergo severe sintering and agglomeration, forming a particulate interconnected morphology, reducing the specific surface area and reducing active sites, thus affecting its catalytic activity.

[0111] A comparison of the results from Example 1 and Comparative Example 1 shows that loading nickel-cobalt bimetallic sulfides onto the surface of the nickel foam substrate is beneficial for reducing its performance at 1 A / cm². 2 The overpotential at high current density enhances its catalytic activity for the electrocatalytic oxygen evolution reaction in alkaline environments.

[0112] Compared to Example 1, Comparative Example 2 did not add a cobalt source to the electrolyte during the electrochemical deposition process. This not only prevented the loading of cobalt sulfides onto the nickel foam substrate, but also hindered the promotion of Ni formation on the nickel foam substrate through both kinetic and thermodynamic mechanisms. 2+ Crystalline nickel sulfides were loaded onto a nickel foam substrate.

[0113] Compared to Example 1, Comparative Example 3 adjusted the timing of sulfur source addition. By directly adding the sulfur source during electrodeposition followed by calcination, uniform co-deposition of metal and sulfur at the atomic or nanoscale can be achieved, forming a precursor with uniform composition. After calcination, the sulfide distribution is more uniform and the structure is controllable. Furthermore, no additional high-temperature gas-solid sulfidation step is required, avoiding the problems of low sulfur source utilization and surface over-sulfidation. Conversely, if pure metal is electrodeposited first, and then the sulfur source is introduced during calcination, gas-solid sulfidation may easily lead to uneven sulfur distribution (sulfur-rich surface, sulfur-poor interior), and severe agglomeration of metal particles, significantly reducing their catalytic activity for the electrocatalytic oxygen evolution reaction in an alkaline environment.

[0114] Compared to Example 1, Comparative Example 4, due to the lack of calcination, failed to strengthen the nanosheet structure of the nickel-cobalt bimetallic sulfide and form a uniformly stacked nanosheet array. This resulted in a reduced specific surface area and obscured some active sites, significantly decreasing its catalytic activity for the electrocatalytic oxygen evolution reaction in an alkaline environment. Furthermore, the absence of calcination prevented further enhancement of the adhesion between the nickel-cobalt bimetallic sulfide and the nickel foam substrate, also affecting the catalyst's structural and catalytic stability.

[0115] Furthermore, a three-electrode system was constructed using the nickel-cobalt bimetallic sulfide catalyst provided in Example 1 as the working electrode, a carbon rod as the counter electrode, and an Hg / HgO electrode as the reference electrode. This system was used in a 1 mol / L potassium hydroxide electrolyte at 1 A / cm². 2 Its catalytic stability for the electrocatalytic oxygen evolution reaction in an alkaline environment was tested at high current densities. Figure 3 It can be seen that the nickel-cobalt bimetallic sulfide catalyst provided in Example 1 has a performance of 1 A / cm 2 After continuous operation at high current density for 2100 hours, the potential did not show a significant increase, demonstrating excellent electrochemical durability and superior catalytic stability.

[0116] In summary, the preparation method provided by this invention, through electrochemical deposition and calcination using sulfur and cobalt sources, achieves the loading of nickel-cobalt bimetallic sulfides onto the surface of a nickel foam substrate. This method exhibits excellent catalytic activity and stability for the electrocatalytic oxygen evolution reaction in an alkaline environment, with the overpotential reduced to below 620 mV at high current densities, reaching a minimum of 450 mV, and maintaining stable operation for up to 2100 hours. Furthermore, the electrochemical deposition method allows for good bonding between the nickel-cobalt bimetallic sulfides and the nickel foam substrate without the need for a binder, avoiding physical obscuring of active sites by the binder and thus further enhancing the catalyst's catalytic activity.

[0117] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a nickel-cobalt bimetallic sulfide catalyst, characterized in that, Includes the following steps: A three-electrode system was used, with the first foamed nickel as the working electrode, and electrochemical deposition was carried out in an electrolyte containing cobalt and sulfur sources to obtain the precursor; The precursor was calcined to obtain the nickel-cobalt bimetallic sulfide catalyst.

2. The preparation method according to claim 1, characterized in that, The cobalt source includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride, preferably cobalt sulfate; Preferably, the concentration of the cobalt source in the electrolyte is 0.025 mol / L to 0.075 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, The sulfur source includes any one or a combination of at least two of thiourea, thioacetamide or dithiooxazone, preferably thiourea; Preferably, the concentration of the sulfur source in the electrolyte is 0.25 mol / L to 0.75 mol / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The electrochemical deposition method is cyclic voltammetry. Preferably, the voltage range for the electrochemical deposition is -2.0V to 1.0V; Preferably, the scan rate of the electrochemical deposition is 0.1 mV / s to 120 mV / s; Preferably, the number of scans for the electrochemical deposition is 20 to 50.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The calcination is carried out under a protective atmosphere; Preferably, the protective atmosphere includes nitrogen and / or argon; Preferably, the calcination temperature is 200℃~300℃; Preferably, the calcination holding time is 2h to 10h; Preferably, the heating rate of the calcination is 1℃ / min to 10℃ / min.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method further includes pretreatment of the first nickel foam before electrochemical deposition: placing the first nickel foam in an acid solution for ultrasonic cleaning; Preferably, the acid solution includes any one or a combination of at least two of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution; Preferably, the concentration of the acid solution is 2 mol / L to 4 mol / L; Preferably, the ultrasonic cleaning time is 10 min to 30 min.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The three-electrode system also includes a counter electrode and a reference electrode; Preferably, the counter electrode comprises a second nickel foam and / or a platinum sheet, with the second nickel foam being more preferred; Preferably, the reference electrode comprises a saturated calomel electrode and / or a silver / silver chloride electrode.

8. The preparation method according to claim 1, characterized in that, Includes the following steps: S1. Pretreatment of the first foamed nickel: The first foamed nickel is placed in an acid solution for ultrasonic cleaning; The acid solution includes any one or a combination of at least two of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution; the concentration of the acid solution is 2 mol / L to 4 mol / L; and the ultrasonic cleaning time is 10 min to 30 min. S2. Using a three-electrode system, the pretreated first foamed nickel is used as the working electrode, and electrochemical deposition is carried out in an electrolyte containing cobalt source and sulfur source to obtain the precursor. The cobalt source comprises any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride, and the concentration of the cobalt source is 0.025 mol / L to 0.075 mol / L; the sulfur source comprises any one or a combination of at least two of thiourea, thioacetamide, or dithiooxazone, and the concentration of the sulfur source is 0.25 mol / L to 0.75 mol / L; the electrochemical deposition method is cyclic voltammetry, the voltage range of the electrochemical deposition is -2.0 V to 1.0 V, the scan rate of the electrochemical deposition is 0.1 mV / s to 120 mV / s, and the number of scan cycles of the electrochemical deposition is 20 to 50. S3. The precursor is calcined to obtain the nickel-cobalt bimetallic sulfide catalyst. The calcination is carried out under a nitrogen and / or argon atmosphere, the calcination temperature is 200℃~300℃, the calcination holding time is 0.5h~12h, and the calcination heating rate is 1℃ / min~10℃ / min.

9. A nickel-cobalt bimetallic sulfide catalyst, characterized in that, The nickel-cobalt bimetallic sulfide catalyst is prepared by the preparation method according to any one of claims 1 to 8; The nickel-cobalt bimetallic sulfide catalyst comprises a nickel foam substrate and a nickel-cobalt bimetallic sulfide supported on the surface of the nickel foam substrate.

10. The application of the nickel-cobalt bimetallic sulfide catalyst as described in claim 9, characterized in that, The nickel-cobalt bimetallic sulfide catalyst is used in the electrocatalytic oxygen evolution reaction in an alkaline environment.

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