Graded nickel / nickel sulfide-porous nickel foam electrode, its preparation method and application

Abstract

This application provides a hierarchical nickel / nickel sulfide-porous nickel foam electrode, its preparation method, and its application. The hierarchical nickel / nickel sulfide-porous nickel foam electrode has a hierarchical porous structure and includes a porous nickel foam substrate and a nickel / nickel sulfide heterostructure immobilized on the porous nickel foam substrate. The nickel / nickel sulfide heterostructure includes nickel nanoparticles and nickel sulfide nanosheets coated on the surface of the nickel nanoparticles. This application is the first to use an electrochemical synthesis method to grow a nickel / nickel sulfide heterostructure in situ on a porous nickel foam substrate. The preparation process is simple, and the prepared hierarchical nickel / nickel sulfide-porous nickel foam electrode exhibits excellent activity and stability in alkaline water electrolysis for hydrogen production, effectively reducing the overpotential of water electrolysis, reducing energy consumption, and lowering the cost of hydrogen production.

Description

Technical Field

[0001] This application belongs to the field of electrode preparation technology for water electrolysis to produce hydrogen, and more specifically, it relates to a graded nickel / nickel sulfide-porous foam nickel electrode, its preparation method and application. Background Technology

[0002] Green hydrogen is considered an ideal alternative to traditional fossil fuels. Electrolysis of water, driven by clean and sustainable energy sources, is an important method for producing green hydrogen. However, the large-scale application of water electrolysis technology is greatly hindered by the lack of efficient and stable hydrogen evolution reaction electrodes, especially in alkaline media. Currently commercially available nickel-based electrodes exhibit high reaction overpotentials and slow reaction kinetics, resulting in high energy consumption. While platinum-based electrocatalysts possess high activity, their high cost, limited reserves, and poor stability make them unsuitable for many applications. Therefore, developing efficient and stable alkaline water electrolysis electrodes is of great significance for the development of water electrolysis hydrogen production technology.

[0003] Unlike acidic electrolytes where a large number of hydrogen ions are present, the hydrogen evolution reaction (HEP) in alkaline electrolytes requires additional energy to dissociate water molecules into active hydrogen, known as the Volmer step. Therefore, its slow reaction kinetics are often two to three orders of magnitude slower than in acidic electrolytes. Heterostructures, due to their inherent anisotropy and highly controllable flexibility, have attracted significant attention from researchers. By controlling the components of heterostructures, various heterointerfaces with different properties can be obtained. Utilizing the synergistic effect of different components, the adsorption free energy of the heterointerface for reactants and intermediates can be optimized, thereby promoting water dissociation and hydrogen adsorption and desorption processes in the HEP reaction, significantly enhancing the HEP reaction activity of the electrode.

[0004] However, at present, electrode materials with heterostructures are generally prepared by high-temperature hydrothermal methods, which are complicated and energy-intensive. Moreover, the prepared electrode materials still have the drawbacks of high reaction overpotential and high energy consumption. Summary of the Invention

[0005] The purpose of this application is to provide a graded nickel / nickel sulfide-porous foam nickel electrode, its preparation method and application, to solve the technical problems of low activity and stability of hydrogen evolution reaction electrodes, high reaction overpotential and high power consumption in existing alkaline water electrolysis hydrogen production technology.

[0006] To achieve the above objectives, a first aspect of this application provides a graded nickel / nickel sulfide-porous nickel foam electrode, wherein the graded nickel / nickel sulfide-porous nickel foam electrode has a graded porous structure, the graded nickel / nickel sulfide-porous nickel foam electrode includes a porous nickel foam substrate and a nickel / nickel sulfide heterostructure fixed on the porous nickel foam substrate, the nickel / nickel sulfide heterostructure includes nickel nanoparticles and nickel sulfide nanosheets coated on the surface of the nickel nanoparticles.

[0007] Furthermore, the nickel sulfide nanosheets are amorphous, while the nickel nanoparticles are crystalline.

[0008] A second aspect of this application provides a method for preparing the above-mentioned graded nickel / nickel sulfide-porous nickel foam electrode, comprising the following steps:

[0009] Preparation of porous nickel foam substrate;

[0010] A first electrolyte containing a first nickel salt, thiourea, and ammonium chloride was prepared.

[0011] The porous nickel foam substrate is used as the cathode and placed in the first electrolyte to carry out an electrochemical synthesis reaction to grow a nickel / nickel sulfide heterostructure in situ on the surface of the porous nickel foam substrate.

[0012] Furthermore, the porous nickel foam substrate is prepared by the following method:

[0013] Preparation of a second electrolyte containing a second nickel salt and ammonium chloride;

[0014] Using the dynamic bubble template method, commercially available nickel foam was used as the cathode and placed in the second electrolyte for electrodeposition.

[0015] Further, the second nickel salt is at least one of nickel chloride, nickel sulfate, and nickel nitrate, and its concentration in the second electrolyte is 0.1 to 1 mol / L; and / or the concentration of ammonium chloride in the second electrolyte is 0.1 to 2 mol / L.

[0016] Furthermore, the cathode current density of the electrodeposition reaction is 0.1–1 A cm⁻¹. -2 .

[0017] Furthermore, the electrodeposition reaction time is 100–1000 s.

[0018] Further, the first nickel salt is at least one of nickel chloride, nickel sulfate, and nickel nitrate, and its concentration in the first electrolyte is 0.1 to 1 mol / L; and / or the concentration of ammonium chloride in the first electrolyte is 0.1 to 1 mol / L.

[0019] Furthermore, the concentration of thiourea in the first electrolyte is 0.1–1 mol / L.

[0020] Furthermore, the cathode voltage applied to the electrochemical synthesis reaction is -1.0 to -2.0V (relative to the silver / silver chloride reference electrode, the salt bridge solution is a saturated potassium chloride solution).

[0021] Furthermore, the electrochemical synthesis reaction takes 100–1000 s.

[0022] A third aspect of this application provides the application of a graded nickel / nickel sulfide-porous nickel foam electrode in hydrogen production by water electrolysis, wherein the graded nickel / nickel sulfide-porous nickel foam electrode is prepared by any of the preparation methods described above.

[0023] Compared with the prior art, this application has the following technical effects:

[0024] The hierarchical porous structure of the graded nickel / nickel sulfide-porous foam nickel electrode of this application is beneficial to the mass transfer and bubble diffusion process, further improving the performance under high current density. It has excellent activity and stability in alkaline hydrogen evolution reaction, effectively reducing the overpotential of water electrolysis, reducing power consumption, and lowering the cost of hydrogen production.

[0025] This application discloses a method for preparing a graded nickel / nickel sulfide-porous nickel foam electrode. For the first time, a nickel / nickel sulfide heterostructure is grown in situ on a porous nickel foam substrate using an electrochemical synthesis method. The preparation process is simple, and the prepared graded nickel / nickel sulfide-porous nickel foam electrode exhibits excellent activity and stability in alkaline water electrolysis for hydrogen production. It effectively reduces the overpotential of water electrolysis, reduces energy consumption, and lowers the cost of hydrogen production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 Scanning electron microscope (SEM) images of commercially available nickel foam (a, b) and porous nickel foam (c, d) provided in Example 1 of this application;

[0028] Figure 2 Contact angle test images of commercially available nickel foam and porous nickel foam provided in Embodiment 1 of this application;

[0029] Figure 3SEM images (a, b), transmission electron microscope (TEM) images (c), and elemental distribution images (d) of the nickel / nickel sulfide heterostructure provided in Example 1 of this application;

[0030] Figure 4 X-ray diffraction (XRD) pattern (a) and X-ray photoelectron spectroscopy (XPS) pattern (b) of nickel sulfide and nickel / nickel sulfide heterostructure provided in Example 1 of this application;

[0031] Figure 5 The polarization curve (a) of the hydrogen evolution reaction and the stability test diagram (b) of the nickel / nickel sulfide-porous nickel foam electrode provided in Example 1 of this application are shown. Detailed Implementation

[0032] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0033] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0035] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0036] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0037] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0038] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0039] The following examples illustrate a graded nickel / nickel sulfide-porous nickel foam electrode, its preparation method, and its application.

[0040] Example 1

[0041] (1) Commercial nickel foam is placed in dilute hydrochloric acid, ethanol and ultrapure water in sequence and ultrasonically treated for 15 minutes. Then it is rinsed with ultrapure water and dried for later use.

[0042] (2) Add 1.19 g of nickel chloride and 5.35 g of ammonium chloride to 50 mL of ultrapure water and stir for 15 minutes to obtain a solution as the electrolyte. Use the commercially available nickel foam treated in step (1) as the cathode and the graphite electrode as the anode, and apply -1 A cm using an electrochemical workstation. -2 The cathode current density was set at 600 s, and the reaction time was 600 s. After the reaction was complete, the electrode was removed, rinsed with ultrapure water, and dried to obtain a porous nickel foam substrate. Figure 1 For commercially available nickel foam ( Figure 1 a, b) and porous nickel foam ( Figure 1 SEM images c and d show that after processing commercial nickel foam using the bubble template method, the surface of the resulting porous nickel foam electrode is covered with nickel nanoparticles, resulting in a rougher surface and a porous structure. Figure 2 The images show contact angle test results for commercially available nickel foam and porous nickel foam, indicating that the surface of commercially available nickel foam is hydrophobic while the surface of porous nickel foam is superhydrophilic.

[0043] (3) Add 1.19 g of nickel chloride, 3.80 g of thiourea, and 0.30 g of ammonium chloride to 50 mL of ultrapure water and stir for 15 minutes to obtain a solution as the electrolyte. Use the porous nickel foam substrate obtained in step (2) as the working electrode, the graphite electrode as the counter electrode, and the silver / silver chloride (saturated potassium chloride) electrode as the reference electrode. Apply a working voltage of -1.8 V (relative to the reversible hydrogen electrode) using an electrochemical workstation, and the reaction time is 600 s. After the reaction is completed, remove the electrode, rinse it with ultrapure water, and dry it to obtain the graded nickel / nickel sulfide-porous nickel foam electrode.

[0044] Using a similar preparation method, without adding ammonium chloride in step (3) above, and with the other process steps being the same, a nickel sulfide-porous nickel foam electrode with only nickel sulfide fixed will be obtained.

[0045] Using a similar preparation method, without adding thiourea in step (3) above, and with the other process steps being the same, a nickel-porous foam nickel electrode with only nickel fixed will be obtained.

[0046] Figure 3 SEM, TEM, and elemental distribution images of the nickel / nickel sulfide heterostructure in the graded nickel / nickel sulfide-porous foam nickel electrode prepared for the embodiments of this application show that amorphous nickel sulfide nanosheets are coated on the surface of crystalline nickel nanoparticles to form a nickel / nickel sulfide heterostructure, in which nickel and sulfur elements are uniformly distributed.

[0047] Figure 4 The XRD and XPS spectra of nickel sulfide and nickel / nickel sulfide heterostructures are shown. XRD confirms the amorphous state of nickel sulfide and the crystalline state of nickel. XPS results show that there is electron transfer between nickel and nickel sulfide in the nickel / nickel sulfide heterostructure, indicating close contact at the heterostructure interface.

[0048] Electrochemical performance was characterized in 1M KOH solution using the graded nickel / nickel sulfide-porous nickel foam electrode prepared in the embodiments of this application as the working electrode, the graphite electrode as the counter electrode, and the mercury / mercury oxide (1M KOH) electrode as the reference electrode. Figure 5 For polarization curves and stability testing of the hydrogen evolution reaction, nickel-porous nickel foam, nickel sulfide-porous nickel foam, and nickel / nickel sulfide-porous nickel foam require overpotentials of 242 mV, 131 mV, and 61 mV, respectively, to reach 100 mA cm⁻¹. -2 The current density indicates that the nickel / nickel sulfide heterostructure possesses excellent catalytic activity for the hydrogen evolution reaction. Furthermore, the nickel / nickel sulfide-porous nickel foam electrode only requires overpotentials of 121 mV and 157 mV to achieve an industrial-grade 500 mA cm⁻¹ current density. -2 and 1000mA cm -2 Current density, and at 100 mA cm -2It can operate stably for 12 hours at current density.

[0049] Example 2

[0050] A porous nickel foam substrate was prepared according to the method in Example 1. Then, 1.19 g of nickel chloride, 3.80 g of thiourea, and 0.30 g of ammonium chloride were added to 50 mL of ultrapure water and stirred for 15 minutes to obtain a solution used as the electrolyte. The porous nickel foam substrate was used as the working electrode, a graphite electrode as the counter electrode, and a silver / silver chloride (saturated potassium chloride) electrode as the reference electrode. An electrochemical workstation was used to apply a working voltage of -2 V, and the reaction time was 600 s. After the reaction was completed, the electrodes were removed, rinsed with ultrapure water, and dried to obtain a graded nickel / nickel sulfide-porous nickel foam electrode. Hydrogen evolution reaction testing showed that this electrode required an overpotential of 65 mV to reach 100 mA cm⁻¹. -2 Current density.

[0051] Example 3

[0052] A porous nickel foam substrate was prepared according to the method in Example 1. Then, 1.19 g of nickel chloride, 3.80 g of thiourea, and 0.30 g of ammonium chloride were added to 50 mL of ultrapure water and stirred for 15 minutes to obtain a solution used as the electrolyte. The porous nickel foam substrate was used as the working electrode, a graphite electrode as the counter electrode, and a silver / silver chloride (saturated potassium chloride) electrode as the reference electrode. An electrochemical workstation was used to apply a working voltage of -1.8 V, and the reaction time was 900 s. After the reaction was completed, the electrodes were removed, rinsed with ultrapure water, and dried to obtain a graded nickel / nickel sulfide-porous nickel foam electrode. Hydrogen evolution reaction testing showed that this electrode required an overpotential of 68 mV to reach 100 mA cm⁻¹. -2 Current density.

[0053] Example 4

[0054] A porous nickel foam substrate was prepared according to the method in Example 1. Then, 1.19 g of nickel chloride, 3.80 g of thiourea, and 0.20 g of ammonium chloride were added to 50 mL of ultrapure water and stirred for 15 minutes to obtain a solution used as the electrolyte. The porous nickel foam substrate was used as the working electrode, a graphite electrode as the counter electrode, and a silver / silver chloride (saturated potassium chloride) electrode as the reference electrode. An electrochemical workstation was used to apply a working voltage of -2 V, and the reaction time was 600 s. After the reaction was completed, the electrodes were removed, rinsed with ultrapure water, and dried to obtain a graded nickel / nickel sulfide-porous nickel foam electrode. Hydrogen evolution reaction testing showed that this electrode required an overpotential of 71 mV to reach 100 mA cm⁻¹. -2 Current density.

[0055] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a hierarchical nickel / nickel sulfide- porous nickel foam electrode, characterized in that, The hierarchical nickel / nickel sulfide-porous nickel foam electrode comprises a porous nickel foam substrate and a nickel / nickel sulfide heterostructure fixed on the porous nickel foam substrate, wherein the nickel / nickel sulfide heterostructure comprises nickel nanoparticles and nickel sulfide nanosheets coated on the surface of the nickel nanoparticles, and the preparation method comprises the following steps: S1, preparing a porous nickel foam substrate a second electrolyte containing a second nickel salt and ammonium chloride is prepared; The commercial foamed nickel is used as the cathode and is placed in the second electrolyte to carry out the electrodeposition reaction; the second nickel salt is nickel chloride, the second electrolyte is obtained by adding 1.19 g of nickel chloride and 5.35 g of ammonium chloride into 50 mL of ultrapure water and stirring for 15 minutes; the cathode current density of the electrodeposition reaction is 0.1-1 A cm -2 ; the time of the electrodeposition reaction is 600 s; S2, preparing a hierarchical nickel / nickel sulfide-porous nickel foam electrode a first electrolyte containing a first nickel salt, thiourea and ammonium chloride is prepared; the porous nickel foam substrate is used as a cathode and is placed in the first electrolyte to perform an electrochemical synthesis reaction to in-situ grow a nickel / nickel sulfide heterostructure on the surface of the porous nickel foam substrate; the first nickel salt is nickel chloride, the first electrolyte is obtained by adding 1.19 g of nickel chloride, 3.80 g of thiourea and 0.30 g of ammonium chloride into 50 mL of ultrapure water and stirring for 15 minutes, the cathode voltage applied in the electrochemical synthesis reaction is-1.8~-2.0 V, and the electrochemical synthesis reaction time is 600 s.

2. A hierarchical nickel / nickel sulfide- porous nickel foam electrode, characterized in that, The hierarchical nickel / nickel sulfide-porous nickel foam electrode is prepared by the preparation method of claim 1.

3. Application of the hierarchical nickel / nickel sulfide-porous nickel foam electrode of claim 2 in electrolytic water hydrogen production.

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