Nickel-based catalyst electrode and preparation method and application thereof

Abstract

The invention discloses a nickel-based catalyst electrode and a preparation method and application thereof, and relates to the technical field of catalyst electrode preparation. The method comprises the following steps: adding basic salt obtained by grinding cationic hydroxide and a nickel source matrix into a crucible, and heating until the basic salt is in a molten state; and the nickel source matrix is subjected to soaking reaction in the alkaline molten salt so as to form nickel hydroxide containing corresponding cations on the surface of the nickel source matrix. The cation-doped nickel-based catalyst is prepared in one step by adopting an alkaline molten salt method, the cation-doped nickel-based catalyst is of a vertical ultrathin and agglomeration-free nano-sheet structure, exposure of active sites can be increased, effective discharge of bubbles in the large-current reaction process is promoted, meanwhile, cations are inserted into layered nickel hydroxide, the interlayer spacing is effectively adjusted, and the catalytic activity of the catalyst is improved. According to the present invention, the catalyst is prepared, the binding force of the catalyst to OH <-> under the alkaline condition is optimized, and the binding strength of nickel ions and. OH can be effectively reduced, such that the performance of the catalyst in the oxygen evolution reaction is excellent, and the oxygen evolution reaction activity of the catalyst is substantially improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst electrode preparation, and in particular to a nickel-based catalyst electrode with an ultra-thin non-aggregated nanosheet structure and a preparation method and application thereof. Background Art

[0002] Layered hydroxides (LDHs) are highly tunable catalysts, especially suitable for the oxygen evolution reaction (OER). 2 ) catalyst is an important layered hydroxide catalyst, and with its two-dimensional layered structure, it is considered to be a potential catalyst for oxygen evolution reaction; nickel hydroxide catalyst is also called nickel-based catalyst.

[0003] The oxygen evolution reaction mainly occurs in the near-surface region of the catalyst. However, nickel-based catalysts tend to accumulate when stored or loaded onto electrodes, making the thickness difficult to control, thereby blocking the surface active sites required for the catalytic reaction.

[0004] At present, hydrothermal method is a common method for synthesizing nickel-based catalysts, but this method is also prone to cause the aggregation and restacking of the nickel-based catalyst sheet structure, thereby blocking the surface active sites required for the catalytic reaction; in addition, since Ni-based catalysts have strong OH radical binding force under alkaline conditions and the rate-limiting step (RDS) is accompanied by a high energy barrier, their OER activity is greatly limited. The above-mentioned shortcomings of the preparation and treatment methods limit the huge application potential of Ni-based LDH catalysts in low-cost and large-scale preparation. Summary of the invention

[0005] In view of this, the present invention provides a nickel-based catalyst electrode and a preparation method and application thereof, which at least partially solve the problems existing in the prior art.

[0006] One of the objects of the present invention is to provide a nickel-based catalyst electrode.

[0007] A second object of the present invention is to provide a method for preparing the above-mentioned nickel-based catalyst electrode.

[0008] A third object of the present invention is to provide an application of the above-mentioned nickel-based catalyst electrode in oxygen evolution reaction.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: In a first aspect, the present invention provides a nickel-based catalyst electrode, comprising a nickel source substrate and cation-doped nickel hydroxide nanosheets, wherein the cation-doped nickel hydroxide nanosheets grow vertically and cross each other on the nickel source substrate to form a mesh nanosheet array.

[0010] The cation can be K + 、Na+ , Cs + , Li + , Sr 2+ , Ca 2+ A cation whose hydroxide can melt at high temperature, preferably K + , K + The doped nickel hydroxide is named K-Ni(OH) 2 .

[0011] The nickel source matrix may be nickel foam, and the pore size of the nickel foam (the mesh size of the network structure) is 80-300 μm, preferably 100-250 μm.

[0012] Preferably, the average thickness of the cation-doped nickel hydroxide nanosheets is 0.04±0.018 μm; Average thickness test method of nanosheets: The nanosheets are photographed using a scanning electron microscope, and the thickness of the nanosheets at different locations is extracted using software (such as image processing software such as Image J). A frequency distribution histogram is plotted to statistically analyze the thickness range distribution and obtain the average thickness.

[0013] In a second aspect, the present invention provides a method for preparing the above-mentioned nickel-based catalyst electrode, comprising the following steps: The alkaline salt obtained by grinding the cationic hydroxide and the nickel source matrix are added into a crucible and heated until the alkaline salt is molten; the nickel source matrix is ​​immersed in the molten alkaline salt to react so as to grow nickel hydroxide containing corresponding cations on the surface of the nickel source matrix; the product obtained by the reaction is washed and dried to obtain a nickel-based catalyst electrode.

[0014] In some embodiments, the cationic hydroxide is selected from KOH, NaOH, CsOH, LiOH, Sr(OH) 2 , Ca(OH) 2 One or more of the foregoing, preferably KOH.

[0015] In some embodiments, the grinding time is 0.5-8 h, preferably 2-4 h.

[0016] In some embodiments, the nickel source substrate is nickel foam, and the pore size of the nickel foam is 80-300 μm, preferably 100-250 μm.

[0017] In some embodiments, each piece is 1×1 cm 2 The amount of cationic hydroxide added is 4-10 g. The amount of hydroxide can fully immerse the nickel source after the hydroxide is melted.

[0018] In some embodiments, the heating and melting temperature is 200-600°C.

[0019] In some embodiments, the soaking reaction time is 0.5-10 h, preferably 4-8 h.

[0020] In some embodiments, the drying temperature is 45-100° C., and the drying time is 6-12 h.

[0021] The present invention uses nickel foam as a nickel source to in-situ grow nickel-based hydroxide in an alkaline molten salt environment. The molten salt environment has a high mass transfer rate and a high concentration of OH. - It grows by etching on the surface of nickel foam and is closely connected to the nickel foam substrate. The grown nanosheet structure is vertically oriented, and each nanosheet forms a nanosheet network array. There is no aggregation and stacking structure between the nanosheets, which is beneficial to increase the exposure of active sites. At the same time, cations are inserted into the layered nickel hydroxide, which effectively adjusts the interlayer spacing and optimizes the binding force of the catalyst to ·OH under alkaline conditions. The inserted cations can competitively bind to ·OH, which can effectively reduce the binding strength of nickel ions and ·OH, and then release nickel ions to participate in the oxygen evolution reaction. This mechanism helps to improve the electrocatalytic performance, making the performance of nickel-based catalysts in the oxygen evolution reaction even better, greatly improving their oxygen evolution reaction activity.

[0022] In a third aspect, the present invention provides an application of the above-mentioned nickel-based catalyst electrode in oxygen evolution reaction.

[0023] The present invention has the following beneficial effects: 1. The present invention adopts an alkaline molten salt method to prepare a nickel-based catalyst in one step. Since the molten salt environment has an excellent mass transfer rate, the synthesized nickel-based catalyst presents an upright ultra-thin nanosheet structure without agglomeration; the upright structure of the nickel-based catalyst is conducive to increasing the exposure of active sites and promoting the effective discharge of bubbles during high current reactions, which provides a new idea for the design of oxygen evolution catalysts in industrial environments; 2. In addition, K + The insertion of isocyanate cations into layered nickel hydroxide effectively regulates the interlayer distance of layered nickel hydroxide, optimizes the binding force of the catalyst to ·OH under alkaline conditions, thereby improving its oxygen evolution activity and achieving the purpose of optimizing the electrocatalytic performance; nickel ions have strong electrophilicity, resulting in a strong binding force between them and ·OH. By introducing cations, their competitive binding can effectively reduce the binding strength between nickel ions and ·OH, thereby releasing nickel ions to participate in the oxygen evolution reaction. This mechanism helps to improve the electrocatalytic performance, making the nickel-based catalyst perform better in the oxygen evolution reaction; 3. At the same time, the preparation method of the present invention expands the preparation route of nickel-based catalysts, and has the characteristics of being green, mild and environmentally friendly. The nickel hydroxide catalyst synthesized by this method not only has high purity, but also has a controllable structure, and can synthesize ultra-thin and non-agglomerated nickel-based catalysts in situ in a strong alkaline environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The K-Ni(OH) prepared in Example 1 is shown 2 XRD pattern of the catalyst; Figure 2 The K-Ni(OH) prepared in Example 1 is shown 2 SEM images of the catalyst; Figure 3 The K-Ni(OH) prepared in Example 1 is shown 2 SEM-mapping of the catalyst; Figure 4 The K-Ni(OH) prepared in Comparative Example 1 is shown. 2 SEM images of the catalyst; Figure 5 The K-Ni(OH) prepared in Comparative Example 2 is shown. 2 SEM images of the catalyst; Figure 6 The K-Ni(OH) prepared in Example 1 is shown 2 Nanosheet thickness distribution of the catalyst. DETAILED DESCRIPTION

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] It should be noted that the following embodiments and features in the embodiments may be combined with each other in the absence of conflict; and, based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work are within the scope of protection of the present disclosure.

[0028] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0029] Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0030] raw material: Nickel foam comes from Kunshan Green Creation Electronic Technology Co., Ltd.

[0031] Example 1 The method for preparing a nickel-based catalyst electrode in this embodiment comprises the following steps: Take 6 g of potassium hydroxide and grind it in a mortar for 3 h; add the ground alkali salt to the crucible and add a 1×1 cm 2 The nickel foam (pore size is 230 μm) is prepared; the mixture is heated to 400 ℃ to reach a molten state; the mixture is immersed and reacted at 400 ℃ for 6 h, and the reaction product is washed with deionized water and dried to obtain potassium ion-doped nickel hydroxide.

[0032] The samples were characterized by XRD. Figure 1 As shown, Ni(OH) appeared in the product 2 Characteristic diffraction peaks of. Characterized by SEM, such as Figure 2 As shown, the surface of the nickel mesh is evenly covered with upright nanosheet catalysts, and the upright nanosheet structure has no agglomeration structure. Figure 3 Shows K-Ni(OH) 2 The SEM-mapping results clearly show the uniform distribution of elements K, Ni and O, indicating that K is successfully doped into Ni(OH) 2 In catalyst.

[0033] It should be noted that after potassium hydroxide is ground in a mortar for 3 hours, especially in a humid environment, potassium hydroxide will undergo a chemical reaction to produce other alkaline salts such as potassium carbonate, resulting in the final product after grinding no longer being pure potassium hydroxide, but existing in the form of an alkaline salt.

[0034] Example 2 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the molten salt environment is CsOH.

[0035] Example 3 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the molten salt environment is NaOH.

[0036] Example 4 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the molten salt environment is LiOH.

[0037] Example 5 The method for preparing the nickel-based catalyst electrode in this example is similar to that in Example 1, except that the grinding time is 0.5 h.

[0038] Example 6 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the grinding time is 8 hours.

[0039] Example 7 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the molten salt temperature is 200°C.

[0040] Example 8 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the molten salt temperature is 600°C.

[0041] Example 9 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the immersion time is 0.5 h.

[0042] Example 10 The method for preparing the nickel-based catalyst electrode in this embodiment refers to that in Embodiment 1, except that the immersion time is 10 hours.

[0043] Embodiment 11 The method for preparing the nickel-based catalyst electrode in this embodiment is similar to that in embodiment 1, except that: the molten salt environment is Sr(OH) 2 .

[0044] Example 12 The method for preparing the nickel-based catalyst electrode in this embodiment is similar to that in embodiment 1, except that: the molten salt environment is Ca(OH) 2 .

[0045] Performance Testing At room temperature, a three-electrode system was used to measure the -1The OER performance of the prepared catalyst samples was tested in a KOH solution. The Pt electrode was used as the counter electrode, the Hg / HgO electrode was used as the reference electrode, and the prepared nickel-based catalyst electrode was used as the working electrode. -1 The linear sweep voltammetry (LSV) curve was obtained by scanning at a scan rate of 100 mA cm -2 The results obtained when the current density is 2.5 2.5 2.5 and 2.5 2.5 are shown in Table 1.

[0046] Table 1

[0047] From Table 1 above, it can be seen that the oxygen evolution catalyst (K-Ni(OH) 2 ) electrode sample has the best performance at 100 mA cm -2 The overpotential is minimum when the current density is .

[0048] The present invention prepares cation-doped nanosheet structure K-Ni(OH) in one step by alkaline molten salt method 2 Oxygen evolution material. X-ray diffraction analysis confirmed that the synthesized material was nickel hydroxide, scanning electron microscopy characterized its nanosheet morphology, and SEM mapping further verified the uniform distribution of K, Ni and O elements.

[0049] Cation insertion induced Ni(OH) 2 The interlayer spacing is K + >Na + >Cs + >Li + >Sr 2+ >Ca 2+ The preparation process is simple and efficient, and cation doping and morphology modification can be achieved in one step, which provides a useful reference for the industrial design of nickel-based oxygen evolution catalysts. It also provides ideas for the development of renewable energy and related conversion and storage technologies.

[0050] Comparative Example 1 This comparative example adopts conventional hydrothermal method to prepare Ni(OH) 2 The electrode includes the following steps: 120 mg NiCl 2 6H 2 O and 168 mg hexamethylenetetramine were dissolved in a mixed solution of 27 mL water and 3 mL ethanol, stirred vigorously for 20 min, and then the solution was transferred to a 40 mL Teflon stainless steel high-pressure reactor. A 1×1 cm 2The nickel foam (pore size 230 μm) was heated at 120℃ for 12 h. After cooling naturally to room temperature, the reaction sample was taken out, washed with deionized water and dried.

[0051] Comparative Example 2 This comparative example adopts alkaline hydrothermal method to prepare K-Ni(OH) 2 The electrode includes the following steps: A piece of 1×1 cm 2 The nickel foam (pore size of 230 μm) was placed in 30 mL of KOH aqueous solution with pH = 14, and then the above solution and nickel foam were transferred to a 40 mL Teflon stainless steel high-pressure reactor and heated at 120°C for 12 h. After cooling naturally to room temperature, the reaction sample was taken out, washed with deionized water and dried.

[0052] Performance Testing The test conditions were the same as above, with a voltage of 10 mV s -1 The linear sweep voltammetry (LSV) curve was obtained by scanning at a scan rate of 100 mA cm -2 The results obtained when the current density is 200 ℃ and 800 ℃ are shown in Table 2.

[0053] Table 2 According to the experimental results, the oxygen evolution catalyst (K-Ni(OH) 2 ) samples have the best performance at 100 mA cm -2 Compared with the conventional Ni(OH) synthesized by hydrothermal addition of nickel source, the overpotential is the smallest when the current density is . 2 , still showing excellent performance. And the oxygen evolution catalyst synthesized by alkaline molten salt (K-Ni(OH) 2 ) is more active than K-Ni(OH) synthesized in alkaline aqueous solution 2 .

[0054] Further provide the SEM pictures of Comparative Example 1 and Comparative Example 2, such as Figure 4 and Figure 5 As shown. It can be found that the comparative example 1 (Ni(OH) synthesized by conventional external nickel source hydrothermal synthesis) 2 ) presents an aggregated nanoflower morphology, and comparative example 2 (K-Ni(OH) synthesized in alkaline aqueous solution) 2 ) show wrinkled nanosheets. The nanosheets synthesized by these two methods have different degrees of agglomeration, which is not conducive to the removal of bubbles.

[0055] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A nickel-based catalyst electrode, comprising: A nickel source substrate and cation-doped nickel hydroxide nanosheets, wherein the cation-doped nickel hydroxide nanosheets grow vertically and cross each other on the nickel source substrate to form a mesh nanosheet array.

2. The nickel-based catalyst electrode according to claim 1, characterized in that The cation is selected from K + 、Na + , Cs + , Li + , Sr 2+ , Ca 2+ One or more of, preferably K + ; The nickel source matrix is ​​nickel foam, and the pore size of the nickel foam is 80-300 μm, preferably 100-250 μm.

3. The nickel-based catalyst electrode according to claim 1, characterized in that The average thickness of the cation-doped nickel hydroxide nanosheets is 0.04 ± 0.018 μm.

4. A method for preparing a nickel-based catalyst electrode according to any one of claims 1 to 3, characterized in that: The following steps are involved: The alkaline salt obtained by grinding the cationic hydroxide and the nickel source matrix are added into a crucible and heated until the alkaline salt is molten; the nickel source matrix is ​​immersed in the molten alkaline salt to react so as to grow nickel hydroxide containing corresponding cations on the surface of the nickel source matrix; the product obtained by the reaction is washed and dried to obtain a nickel-based catalyst electrode.

5. The preparation method according to claim 4, characterized in that: The grinding time is 0.5-8 h, preferably 2-4 h.

6. The preparation method according to claim 4, characterized in that: Each piece 1×1cm 2 The nickel source matrix is ​​prepared by adding 4-10 g of cationic hydroxide.

7. The preparation method according to claim 4, characterized in that: The heating and melting temperature is 200-600°C.

8. The preparation method according to claim 4, characterized in that: The soaking reaction time is 0.5-10 h, preferably 4-8 h.

9. The preparation method according to claim 4, characterized in that: The drying temperature is 45-100℃ and the drying time is 6-12 h.

10. Use of the nickel-based catalyst electrode according to any one of claims 1 to 3 or the nickel-based catalyst electrode prepared by the preparation method according to any one of claims 4 to 9 in oxygen evolution reaction.

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