A nickel-based electrode with a phosphate armor layer and a method of making and using the same

Abstract

The application relates to a nickel-based electrode with a phosphate armor layer and a preparation method and application thereof, and belongs to the technical field of electrochemical energy conversion. The nickel-based electrode with the phosphate armor layer comprises a nickel conductive base body, the surface of the nickel conductive base body has an armor layer and a catalytic layer from inside to outside in sequence, and the catalytic layer is a NiFe layered double hydroxide; the armor layer comprises at least one of a nickel phosphate layer, a nickel borate layer and a nickel silicate layer. The nickel-based electrode not only maintains good conductivity, but also improves the problems of easy peeling of the catalytic layer and easy corrosion of the nickel conductive base body.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy conversion technology, and in particular to a nickel-based electrode with a phosphate armor layer, its preparation method and application. Background Technology

[0002] When electrolyzing water or seawater in alkaline or chlorine-containing electrolytes, the oxygen evolution reaction (OER) process occurring on nickel-based electrodes with phosphate armor layers presents serious structural stability problems. While the NiFe layered double hydroxide (NiFe-LDH) catalyst layer used on nickel-based electrodes with phosphate armor layers generally exhibits high catalytic activity, it is prone to catalyst layer stripping and corrosion of the nickel conductive substrate under prolonged operation or high current densities. The fundamental reason is that under alkaline or saline-alkali conditions, nickel (Ni) in the nickel conductive substrate is easily converted to OH- by hydroxyl groups. - or Cl - Erosion leads to Ni loss and structural collapse.

[0003] Existing protective measures typically involve directly coating a protective layer or dense coating onto the outer surface of the nickel conductive substrate. While this can temporarily prevent the nickel conductive substrate from being corroded, it hinders the electrochemical coupling and growth continuity between the catalyst and the nickel conductive substrate, thereby reducing conductivity and adhesion. Furthermore, this directly coated protective layer or dense coating is prone to peeling off during long-term operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the objectives of this application include providing a nickel-based electrode with a phosphate-coated layer, its preparation method, and its application. This maintains good conductivity while mitigating the problems of easy peeling of the catalyst layer and easy corrosion of the nickel conductive substrate.

[0005] In a first aspect, embodiments of this application provide a nickel-based electrode with a phosphate protective layer, comprising a nickel conductive substrate, wherein the surface of the nickel conductive substrate has a protective layer and a catalyst layer sequentially from the inside to the outside, the catalyst layer being a NiFe layered double hydroxide; the protective layer comprising at least one of a nickel phosphate layer, a nickel borate layer, and a nickel silicate layer.

[0006] The nickel-based electrode with a phosphate protective layer provided in this application has at least one protective layer selected from nickel phosphate, nickel borate, and nickel silicate on the surface of the nickel conductive substrate, which can protect the nickel conductive substrate and reduce nickel deposition by OH groups. - or Cl - The process avoids corrosion and establishes a bonding interface between the nickel conductive substrate, the protective layer, and the catalyst layer, thereby improving the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate. This improves the problem of easy peeling of the catalyst layer and maintains good conductivity.

[0007] In some embodiments of this application, the protective layer is a nickel phosphate layer.

[0008] The nickel-based electrode with a phosphate armor layer provided in this application has a nickel phosphate armor layer on the surface of a nickel conductive substrate. The nickel phosphate layer contains PO4³⁺. - Anionic groups can effectively repel or shield OH groups. - or Cl - Protect the nickel conductive substrate and reduce nickel from being absorbed by OH groups. - or Cl - The process involves corrosion, and the presence of MOP (M=Ni or Fe) bonding interfaces between the nickel conductive substrate and the nickel phosphate layer and catalyst layer improves the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby improving the problem of easy peeling of the catalyst layer and maintaining good conductivity.

[0009] In some embodiments of this application, the nickel conductive substrate includes nickel foam, nickel felt, or nickel foil.

[0010] The nickel-based electrode with phosphate armor provided in this application can use a suitable nickel conductive substrate. Its surface has the aforementioned armor layer and catalyst layer from the inside to the outside. Both can improve the problems of easy peeling of the catalyst layer and easy corrosion of the nickel conductive substrate while maintaining good conductivity.

[0011] Secondly, embodiments of this application provide a method for preparing a nickel-based electrode with a phosphate armor layer as provided in the first aspect, comprising: S1, using an acid solution to form an in-situ protective layer on the surface of a nickel conductive substrate by acid etching; the acid solution includes at least one of phosphoric acid, boric acid, and silicic acid. S2, a catalytic layer is formed on the surface of a nickel conductive substrate with a protective layer to obtain a nickel-based electrode with a phosphate protective layer.

[0012] This application employs a suitable acid solution to directly etch the surface of a nickel conductive substrate, thereby forming a protective layer in situ of at least one of the following: a nickel phosphate layer, a nickel borate layer, and a nickel silicate layer. This protects the nickel conductive substrate and reduces the amount of nickel coated with OH groups. - or Cl - The etching process, which forms ionic covalent bonds between the nickel conductive substrate and the nickel phosphate layer, can improve the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby improving the problem of easy peeling of the catalyst layer and maintaining good conductivity.

[0013] In some embodiments of this application, the concentration of the acid solution is 0.5~5 M.

[0014] This application uses an acid solution of appropriate concentration to acid etch the surface of a nickel conductive substrate, which facilitates the formation of a continuous and stable protective layer in situ on the surface of the nickel conductive substrate.

[0015] In some embodiments of this application, the concentration of the acid solution is 1~3 M.

[0016] This application further employs an acid solution of a more suitable concentration to acid etch the surface of the nickel conductive substrate, which facilitates the formation of a continuous and stable protective layer in situ on the surface of the nickel conductive substrate and reduces excessive acid etching of the nickel conductive substrate by the acid solution.

[0017] In some embodiments of this application, the acid etching time for the nickel conductive substrate surface is 1 to 30 minutes.

[0018] This application employs acid etching treatment on the surface of a nickel conductive substrate for an appropriate time, which facilitates the formation of a continuous and stable protective layer in situ on the surface of the nickel conductive substrate.

[0019] In some embodiments of this application, the acid etching time for the nickel conductive substrate surface is 5 to 10 minutes.

[0020] This application further employs acid etching treatment of the nickel conductive substrate surface for a more suitable time, which is conducive to the formation of a continuous and stable protective layer in situ on the nickel conductive substrate surface and reduces the excessive acid etching of the nickel conductive substrate by the acid solution.

[0021] In some embodiments of this application, forming a catalytic layer on the surface of a nickel conductive substrate with a protective layer includes: immersing the nickel conductive substrate with a protective layer in a 0.2-1 M ferric ion solution for 10-30 seconds, removing it, and placing it in air for 1-10 hours to form a NiFe layered double hydroxide on the surface of the nickel conductive substrate with a protective layer.

[0022] This application employs an etching method to form a catalyst layer in situ on the surface of a nickel conductive substrate with a protective layer. This allows for further bonding of ionic covalent bonds on the basis of the ionic covalent bonds formed between the nickel conductive substrate and the nickel phosphate layer, creating a bonding interface. This effectively improves the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby mitigating the problem of easy peeling of the catalyst layer and maintaining good conductivity.

[0023] In some embodiments of this application, the ferric ion solution includes at least one of Fe(NO3)3, Fe2(SO4)3, and FeCl3.

[0024] This application uses a suitable ferric ion solution, which facilitates the in-situ corrosion formation of stable NiFe layered double hydroxides on the surface of a nickel conductive substrate with a protective layer.

[0025] Thirdly, embodiments of this application provide an application of a nickel-based electrode with a phosphate armor layer, as provided in the first aspect, in the electrolytic oxygen removal reaction in water or seawater.

[0026] The nickel-based electrode with a phosphate armor layer provided in this application has a stable electrochemical coupling and mechanical bond between the catalyst layer and the nickel conductive substrate, exhibiting good conductivity. The catalyst layer is not easily peeled off, and when applied to the electrolytic oxygen desorption reaction in water or seawater, the nickel conductive substrate is not easily corroded. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The scanning electron microscope (SEM) results are shown in Experimental Example 1 of this application; where (a1)-PNF; (b1)-BNF; (c1)-SiNF; (a2)-NiFe LDH / PNF; (b2)-NiFe LDH / BNF; (c2)-NiFe LDH / SiNF.

[0029] Figure 2 The XPS results are shown in Experiment Example 2 of this application.

[0030] Figure 3 The scanning electron microscope (SEM) results provided for Test Example 5 of this application are shown below; (a) - 50 μm view of Example 7; (b) - 10 μm view of Example 7; (c) - 50 μm view of Comparative Example 2; (d) - 10 μm view of Comparative Example 2.

[0031] Figure 4 The scanning electron microscope results provided for Experimental Example 6 of this application are shown in the image; where (a) - Comparative Example 1; (b) - Example 1. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] Currently, the nickel conductive matrix in nickel-based electrodes with phosphate armor is easily affected by OH groups. - or Cl -Erosion causes Ni loss and structural collapse, making the catalyst layer prone to peeling. A common approach is to directly coat the outer surface of the nickel conductive substrate with a protective layer or a dense coating. However, this hinders the electrochemical coupling and mechanical bonding between the catalyst and the nickel conductive substrate, thereby reducing conductivity and the adhesion of the catalyst layer to the outer surface of the nickel conductive substrate, making the catalyst layer prone to peeling. Furthermore, under prolonged operation, this directly coated protective layer or dense coating is also prone to detachment.

[0034] To address the issues of easy peeling of the catalyst layer and easy corrosion of the nickel conductive substrate in current nickel-based electrodes with phosphate armor layers, as well as the reduction of conductivity when coating, this application provides a nickel-based electrode with a phosphate armor layer, comprising a nickel conductive substrate. The surface of the nickel conductive substrate has an armor layer and a catalyst layer sequentially from the inside to the outside. The catalyst layer is a NiFe layered double hydroxide. The armor layer includes at least one of nickel phosphate layer (Ni3(PO4)2), nickel borate layer (Ni3(BO3)2), and nickel silicate layer (Ni2SiO4).

[0035] The nickel-based electrode with a phosphate protective layer provided in this application has at least one protective layer selected from nickel phosphate, nickel borate, and nickel silicate on the surface of the nickel conductive substrate, which can protect the nickel conductive substrate and reduce nickel deposition by OH groups. - or Cl - The etching process, along with the bonding interface between the nickel conductive substrate and the protective layer and catalyst layer, improves the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby mitigating the problem of easy peeling of the catalyst layer and maintaining good conductivity. In some embodiments of this application, the protective layer is a nickel phosphate layer. The nickel-based electrode with the phosphate protective layer has a relatively continuous and dense nickel phosphate protective layer on the surface of the nickel conductive substrate. The continuous and dense nickel phosphate layer is rich in PO4³⁺. - Anionic groups can effectively repel or shield OH groups. - or Cl - Protects the nickel conductive substrate and reduces nickel absorption by OH groups. - or Cl - The process avoids corrosion and establishes a stable MOP (M=Ni or Fe) bonding interface between the nickel conductive substrate and the nickel phosphate layer and catalyst layer, thereby improving the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate. This improves the problem of easy peeling of the catalyst layer and maintains good conductivity.

[0036] In some embodiments of this application, the nickel conductive substrate includes nickel foam, nickel felt, or nickel foil. The nickel-based electrode with a phosphate armor layer uses a suitable nickel conductive substrate, and its surface has the aforementioned armor layer and catalyst layer sequentially from the inside out. Both can maintain good conductivity while simultaneously improving the problems of easy peeling of the catalyst layer and easy corrosion of the nickel conductive substrate.

[0037] Secondly, embodiments of this application provide a method for preparing a nickel-based electrode with a phosphate armor layer as described above, comprising: S1, using an acid solution to form an in-situ protective layer on the surface of a nickel conductive substrate by acid etching; the acid solution includes at least one of phosphoric acid, boric acid, and silicic acid. S2, a catalytic layer is formed on the surface of a nickel conductive substrate with a protective layer to obtain a nickel-based electrode with a phosphate protective layer.

[0038] This application employs a suitable acid solution to directly etch the surface of a nickel conductive substrate, thereby forming a protective layer in situ of at least one of the following: a nickel phosphate layer, a nickel borate layer, and a nickel silicate layer. This protects the nickel conductive substrate and reduces the amount of nickel coated with OH groups. - or Cl - The etching process, which forms ionic covalent bonds between the nickel conductive substrate and the nickel phosphate layer, can improve the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby improving the problem of easy peeling of the catalyst layer and maintaining good conductivity.

[0039] Among them, boric acid, due to its weak acidity and its presence in solution mainly in the form of B(OH)3, usually contains both external and internal coordination, tending to form a borate-rich layer on the surface of the nickel conductive substrate; silicic acid, in addition to forming MO-Si (M=Ni or Fe) bonds with metal sites on the surface of the nickel conductive substrate and the catalyst layer, is also prone to Si-O-Si condensation, resulting in a nickel silicate layer with network and polymerization characteristics; phosphoric acid, through strong internal coordination and metal phosphate formation, forms stable MOP (M=Ni or Fe) bonds and a relatively dense and continuous interface layer with metal sites on the surface of the nickel conductive substrate and the catalyst layer.

[0040] In some embodiments of this application, the concentration of the acid solution is 0.5~5 M. As an example, the concentration of the acid solution can be, but is not limited to, 0.5 M, 1 M, 2 M, 3 M, 4 M, or 5 M. Using an acid solution of suitable concentration for acid etching of the nickel conductive substrate surface facilitates the formation of a continuous and stable protective layer in situ on the nickel conductive substrate surface.

[0041] In some embodiments of this application, the concentration of the acid solution is 1-3 M. For example, the concentration of the acid solution can be, but is not limited to, 1 M, 1.5 M, 2 M, 2.5 M, or 3 M. Further using an acid solution of a more suitable concentration for acid etching the nickel conductive substrate surface facilitates the formation of a continuous and stable protective layer in situ on the nickel conductive substrate surface and reduces excessive acid etching of the nickel conductive substrate.

[0042] In some embodiments of this application, the acid etching time for the nickel conductive substrate surface is 1 to 30 minutes. As an example, the acid etching time for the nickel conductive substrate surface can be, but is not limited to, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes. Using an appropriate acid etching time for the nickel conductive substrate surface facilitates the formation of a continuous and stable protective layer in situ on the nickel conductive substrate surface.

[0043] In some embodiments of this application, the etching time for the nickel conductive substrate surface is 5-10 minutes. As an example, the etching time for the nickel conductive substrate surface can be, but is not limited to, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. Further employing an acid etching treatment of a more suitable time for the nickel conductive substrate surface facilitates the formation of a continuous and stable protective layer in situ on the nickel conductive substrate surface and reduces excessive acid etching of the nickel conductive substrate by the acid solution.

[0044] In some embodiments of this application, forming a catalyst layer on the surface of a nickel conductive substrate with a protective layer includes: immersing the nickel conductive substrate with the protective layer in a 0.2-1 M ferric ion solution for 10-30 seconds, then removing it and placing it in air for 1-10 hours, thereby forming a NiFe layered double hydroxide on the surface of the nickel conductive substrate with the protective layer. Using an etching method to form a catalyst layer in situ on the surface of the nickel conductive substrate with the protective layer allows for further bonding of ionic covalent bonds based on the ionic covalent bonds formed between the nickel conductive substrate and the nickel phosphate layer, forming a bonding interface. This effectively improves the stability of the electrochemical coupling and mechanical bonding between the catalyst layer and the nickel conductive substrate, thereby improving the problem of easy peeling of the catalyst layer and maintaining good conductivity.

[0045] As an example, the concentration of the ferric ion solution can be, but is not limited to, 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, or 1 M. The immersion time of the ferric ion solution in the nickel conductive substrate with the protective layer can be, but is not limited to, 10 s, 15 s, 20 s, 25 s, or 30 s.

[0046] In some embodiments of this application, the ferric ion solution includes at least one of Fe(NO3)3, Fe2(SO4)3, and FeCl3. Using a suitable ferric ion solution facilitates the in-situ corrosion formation of stable NiFe layered double hydroxides on the surface of a nickel-conductive substrate with a protective layer.

[0047] In some embodiments of this application, the nickel conductive substrate can be pretreated, including ultrasonic cleaning of the nickel conductive substrate in 1 M dilute hydrochloric acid for 10-60 s to remove oxide impurities on the surface, followed by cleaning the substrate with deionized water and ethanol in sequence, and then drying it at room temperature.

[0048] Thirdly, embodiments of this application provide an application of a nickel-based electrode with a phosphate armor layer as described above in the electrolytic oxygen removal reaction in water or seawater.

[0049] The nickel-based electrode with a phosphate armor layer provided in this application has a stable electrochemical coupling and mechanical bond between the catalyst layer and the nickel conductive substrate, exhibiting good conductivity. The catalyst layer is not easily peeled off, and when applied to the electrolytic oxygen desorption reaction in water or seawater, the nickel conductive substrate is not easily corroded.

[0050] It should be noted that the general formula for NiFe layered double hydroxide (NiFe-LDH) is [ Ni 1 x 2+ Fe x 3+ ( OH )2] + [ A n ] x / n mH 2 O ,in A n Interlayer anions (such as...) CO 3 2 , NO 3 , Cl wait), x for Fe 3+ / ( Ni 2+ + Fe 3+ The molar ratio of ) m This represents the number of water molecules in the interlayer.

[0051] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0052] The nickel foam used in this application is a commercially available material with a thickness of 1 mm.

[0053] Example 1 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1. The nickel foam is immersed in 1 M phosphoric acid solution for 5 min to form a Ni3(PO4)2 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, nickel foam with a Ni3(PO4)2 protective layer is obtained and defined as PNF. S2, PNF was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on PNF in situ, thus obtaining a nickel-based electrode NiFe LDH / PNF with phosphate armor layer.

[0054] Example 2 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1, immerse the nickel foam in 0.5 M phosphoric acid solution for 5 min to form a Ni3(PO4)2 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, obtain nickel foam with a Ni3(PO4)2 protective layer, which is defined as PNF. S2, PNF was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on PNF in situ, thus obtaining a nickel-based electrode NiFe LDH / PNF with phosphate armor layer.

[0055] Example 3 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1. The nickel foam is immersed in a 5 M phosphoric acid solution for 5 min to form a Ni3(PO4)2 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, nickel foam with a Ni3(PO4)2 protective layer is obtained and defined as PNF. S2, PNF was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on PNF in situ, thus obtaining a nickel-based electrode NiFe LDH / PNF with phosphate armor layer.

[0056] Example 4 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1. The nickel foam is immersed in 1 M phosphoric acid solution for 30 min to form a Ni3(PO4)2 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, nickel foam with a Ni3(PO4)2 protective layer is obtained and defined as PNF. S2, PNF was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on PNF in situ, thus obtaining a nickel-based electrode NiFe LDH / PNF with phosphate armor layer.

[0057] Example 5 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1. The nickel foam is immersed in 1 M boric acid solution for 5 min to form a Ni3(BO3)2 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, nickel foam with a Ni3(BO3)2 protective layer is obtained and defined as BNF. S2, BNF was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on BNF in situ, thus obtaining a nickel-based electrode NiFe LDH / BNF with a phosphate armor layer.

[0058] Example 6 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1, immerse the nickel foam in a 1 M silica solution for 5 min to form a Ni2SiO4 protective layer in situ by acid etching on the surface of the nickel foam. After washing and drying, obtain nickel foam with a Ni2SiO4 protective layer, which is defined as SiNF. S2, SNF is immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on SNF in situ, thus obtaining a nickel-based electrode NiFe LDH / SiNF with phosphate armor layer.

[0059] Example 7 This embodiment provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: S1. The nickel foil is immersed in a 1 M phosphoric acid solution for 5 min to form a Ni3(PO4)2 protective layer in situ by acid etching on the surface of the nickel foil. After washing and drying, the nickel foil with the Ni3(PO4)2 protective layer is obtained and defined as PN. S2, PN is immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on PN in situ, thus obtaining a nickel-based electrode NiFe LDH / PN with phosphate armor layer.

[0060] Comparative Example 1 This comparative example provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: Nickel foam (NF) was immersed in 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on NF in situ, thus obtaining a nickel-based electrode NiFe LDH / NF with a phosphate armor layer.

[0061] Comparative Example 2 This comparative example provides a nickel-based electrode with a phosphate armor layer, the preparation method of which includes: Nickel foil (N) was immersed in a 0.2 M Fe(NO3)3 solution for 30 s, and then placed in air for 1 h to form NiFe layered double hydroxide nanosheets on N in situ, thus obtaining a nickel-based electrode NiFe LDH / N with a phosphate armor layer.

[0062] The methods for preparing nickel-based electrodes with phosphate armor layers provided in Examples 1-7 and Comparative Examples 1-2 are shown in Table 1.

[0063] Table 1. Methods for preparing nickel-based electrodes with phosphate armor layers provided in Examples 1-7 and Comparative Examples 1-2

[0064] Note: In Table 1, " / " indicates that this step is not included.

[0065] Experimental Example 1 This experimental example demonstrates the scanning electron microscopy (SEM) examination of the nickel-based electrodes with phosphate-coated layers provided in Examples 1, 5, 6, and Comparative Example 1. Details are as follows: Each sample was cut to a suitable size and fixed on the sample stage (for samples with insufficient conductivity, pre-sputtering with gold was performed); during testing, imaging was performed under high vacuum conditions, and a field emission scanning electron microscope (JEOL JSM-7800F) was used to observe and record the microstructure, structural uniformity, and surface coverage of the sample surface at different magnifications. The results are as follows: Figure 1 As shown.

[0066] Depend on Figure 1The results show that (a1) is PNF, (b1) is BNF, and (c1) is SiNF; (a2) is NiFe LDH / PNF, (b2) is NiFe LDH / BNF, and (c2) is NiFe LDH / SiNF. Comparing the surface microstructure images of PNF, BNF, and SiNF, it can be seen that the surface of PNF obtained by phosphate etching of NF is an amorphous layer without obvious particles, while the surfaces of BNF and SiNF obtained by boric acid and silicate etching of NF have particles of varying degrees. Comparing the surface microstructure images of NiFe LDH / PNF, NiFe LDH / BNF, and NiFe LDH / SiNF, it can be seen that there is no significant difference between the three nickel-based electrodes with phosphate armor layers. All three have grown NiFe LDH catalytic layers, and the bonding degree with the nickel conductive substrate is relatively good. The catalytic layers are firmly fixed on NF. This application demonstrates that the nickel-based electrodes with phosphate armor layers provided in this application all form stable armor layers and catalytic layers on the surface of a nickel conductive substrate, wherein the formed nickel phosphate armor layer is more continuous and dense.

[0067] Experimental Example 2 This experimental example demonstrates X-ray photoelectron spectroscopy (XPS) detection of the nickel-based electrodes with phosphate-coated layers provided in Examples 1, 5, and 6. Details are as follows: X-ray photoelectron spectroscopy (Thermo Scientific ESCALAB Xi) was used. + Using Al Kα monochromatic X-rays as the excitation source with a photon energy of 1486.6 eV under high vacuum conditions, the full spectrum of each sample was first acquired to determine the types of elements contained on the sample surface. Subsequently, high-resolution fine spectral scanning was performed on the relevant elements to analyze their chemical states. The obtained binding energies were typically calibrated using C 1s = 284.8 eV as the charge correction benchmark. Software was used to perform background subtraction and peak separation fitting on the spectral peaks to obtain the O 1s signal spectrum of XPS, thereby obtaining the chemical bond information and corresponding binding energy positions in each sample. The results are as follows: Figure 2 As shown.

[0068] Depend on Figure 2 The results show that the NiFe LDH / PNF provided in Example 1 has MOP bonds; the NiFe LDH / BNF provided in Example 5 has MOB bonds; and the NiFe LDH / SiNF provided in Example 6 has MO-Si bonds.

[0069] Experimental Example 3 This test example demonstrates resistance testing of the nickel-based electrodes with phosphate armor provided in Examples 1-6 and Comparative Example 1.

[0070] The conductivity of each sample was measured using a four-probe tester (ST2253A from Suzhou Jinglü Electronics Co., Ltd.). Each sample was placed flat on the test platform, ensuring good contact between the four probes and the sample surface. A constant current was applied to the sample through the two outer probes, while the voltage drop was measured through the two inner probes. The resistance value of the sample was calculated using Ohm's law and further converted to sheet resistance. The measured data were then corrected based on the sample thickness, size, and test configuration to obtain the resistivity of each sample. The results are shown in Table 2.

[0071] Table 2 Interface Resistance

[0072] As shown in Table 2, comparing Examples 1-6 and Comparative Example 1, compared with the NiFeLDH / NF without a protective layer in Comparative Example 1, the resistivity of the nickel-based electrodes with phosphate protective layers provided in Examples 1-6 is significantly reduced. This indicates that the nickel-based electrodes with phosphate protective layers provided in this application have lower resistance and enhanced conductivity, which is beneficial to electrocatalytic reactions.

[0073] Comparing Examples 1 and 5-6, the NiFe LDH / PNF provided in Example 1 exhibits the lowest resistance, followed by the NiFe LDH / BNF provided in Example 5, and the NiFe LDH / SiNF provided in Example 6 exhibits the highest resistance. This is because the three oxyacids have different bonding modes and interface layer structures on the surface of nickel foam. Phosphoric acid more easily forms stable MOP internal coordination bonds with the surface of the nickel conductive substrate and the catalyst layer, and constructs a more continuous and dense phosphate-type interface layer, which is beneficial for reducing charge transfer resistance. The interface layer formed by boric acid is mainly composed of BO or MOB related structures, and its bonding mode is greatly affected by surface hydroxyl groups and local pH. The degree of interfacial electronic coupling is usually weaker than that of the phosphoric acid system. In addition to forming MO-Si bonds, silicic acid is also prone to Si-O-Si condensation, forming a networked silicon oxide layer, which increases the interfacial electronic transport resistance.

[0074] Test Example 4 This experimental example demonstrates electrochemical testing of the nickel-based electrodes with phosphate-coated layers provided in Examples 1, 5-6, and Comparative Example 1. Details are as follows: Electrochemical performance tests were performed on each sample using an electrochemical workstation. A three-electrode system was employed: the working electrode was the electrode of each sample under test, the counter electrode was a graphite rod, and the reference electrode was a Hg / HgO electrode. The electrolytes were: alkaline water (1 M KOH + deionized water solution) and alkaline seawater (1 M KOH + real seawater solution). In the electrolyte, the working electrode was activated by cyclic voltammetry (CV) at a potential of 1.0 V and a scan rate of 50 mV / s for 30 cycles. Then, a linear scan voltammetry test was performed at a scan rate of 5 mV / s, and the polarization curve of current density versus potential was recorded. The obtained potential was converted to a potential relative to the reversible hydrogen electrode (RHE). Finally, at 1 A·cm⁻¹... -2 Long-term constant current testing was conducted at a current density of 500 mA·cm⁻¹, and the changes in operating potential and running time were recorded to evaluate the OER stability of the sample; the results are shown in Table 3. -2 and 1000 mA·cm -2 Long-term constant current testing was conducted at current density to extract point values, calculate overpotentials, and evaluate electrode activity; the results are shown in Table 4.

[0075] Table 3 Electrochemical Tests

[0076] Note: In Table 3, " / " indicates that no detection was performed.

[0077] As shown in Table 3, comparing Examples 1, 5-6, and Comparative Example 1, the nickel-based electrodes with phosphate-coated layers provided in Examples 1 and 5-6 exhibit significantly improved stability in electrolytic oxygen removal in alkaline water and alkaline seawater compared to the NiFe LDH / NF electrode without a protective layer in Comparative Example 1. This indicates that the nickel-based electrodes with phosphate-coated layers provided in this application have better stability and conductivity. Among them, the NiFe LDH / PNF electrode provided in Example 1 exhibits the best stability in electrolytic oxygen removal in alkaline seawater.

[0078] Table 4 Electrode Activity

[0079] As shown in Table 4, compared with Example 1, Example 5 and Comparative Example 1, at 500 mA·cm -2 At current density, compared to the NiFe LDH / NF without a protective layer in Comparative Example 1, the nickel-based electrodes with phosphate protective layers provided in Examples 1 and 5 exhibit higher activity, indicating that the nickel-based electrodes with phosphate protective layers provided in this application have higher activity and better performance. Among them, the NiFe LDH / PNF provided in Example 1 has the highest activity and best performance.

[0080] Experimental Example 5 This experiment tested the stability of the nickel-based electrodes with phosphate-coated layers provided in Example 7 and Comparative Example 2, as follows: The nickel-based electrodes with phosphate-coated layers provided in Example 7 and Comparative Example 2 were used as anodes, and the stability was tested at 100 mA·cm⁻¹. -2 The alkaline seawater underwent an electrolytic oxygen reaction for 1 min. After the reaction was complete, the nickel-based electrodes with phosphate-coated layers provided in Example 7 and Comparative Example 2 were subjected to electron microscopy scanning detection. The results are as follows: Figure 3 As shown.

[0081] Depend on Figure 3 The results show that the nickel-based electrode with a phosphate-coated protective layer provided in Example 7, after undergoing an electrolytic oxygen removal reaction in alkaline seawater, maintained a smooth surface on its nickel foil substrate without significant corrosion. In contrast, the nickel-based electrode with a phosphate-coated protective layer provided in Comparative Example 2, after undergoing the same reaction, showed obvious pitting on its nickel foil substrate surface and was severely corroded. This demonstrates that the nickel-based electrode with a phosphate-coated protective layer provided in this application has a protective layer on the surface of the nickel conductive substrate, which can protect the nickel conductive substrate and reduce the corrosion of nickel by OH groups. - or Cl - erosion.

[0082] Experimental Example 6 This experiment tested the stability of the nickel-based electrodes with phosphate-coated layers provided in Example 1 and Comparative Example 1, as follows: The nickel-based electrodes with phosphate-coated layers provided in Example 1 and Comparative Example 1 were used as anodes, and the stability was tested at 1000 mA·cm⁻¹. -2 The alkaline water electrolysis oxygen removal reaction was carried out for 1000 h. After the reaction was completed, the nickel-based electrodes with phosphate armor provided in Example 1 and Comparative Example 1 were subjected to electron microscopy scanning detection. The results are as follows: Figure 4 As shown.

[0083] Depend on Figure 4 The results show that the nickel-based electrode with a phosphate-coated protective layer provided in Example 1 maintained its catalytic layer intact after the alkaline water electrolysis oxygen removal reaction, without significant peeling. In contrast, the nickel-based electrode with a phosphate-coated protective layer provided in Comparative Example 1 showed large-area peeling of its catalytic layer after the alkaline water electrolysis oxygen removal reaction. This indicates that the nickel-based electrode with a phosphate-coated protective layer provided in this application has a protective layer on the surface of the nickel conductive substrate, which can improve the stability of the electrochemical coupling and mechanical bonding between the catalytic layer and the nickel conductive substrate, thereby improving the problem of easy peeling of the catalytic layer.

[0084] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A nickel-based electrode with a phosphate armor layer, characterized in that, The invention includes a nickel conductive substrate, the surface of which has a protective layer and a catalyst layer from the inside out, the catalyst layer being a NiFe layered double hydroxide; the protective layer includes at least one of a nickel phosphate layer, a nickel borate layer, and a nickel silicate layer.

2. The nickel-based electrode with a phosphate armor layer according to claim 1, characterized in that, The protective layer is a nickel phosphate layer.

3. The nickel-based electrode with a phosphate armor layer according to claim 1, characterized in that, The nickel conductive substrate includes nickel foam, nickel felt, or nickel foil.

4. A method for preparing a nickel-based electrode with a phosphate armor layer as described in any one of claims 1 to 3, characterized in that, include: S1, using an acid solution to acid-etch the surface of the nickel conductive substrate to form a protective layer in situ; the acid solution includes at least one of phosphoric acid, boric acid, and silicic acid. S2, a catalytic layer is formed on the surface of the nickel conductive substrate with a protective layer to obtain a nickel-based electrode with a phosphate protective layer.

5. The preparation method according to claim 4, characterized in that, The concentration of the acid solution is 0.5~5 M.

6. The preparation method according to claim 5, characterized in that, The concentration of the acid solution is 1~3 M.

7. The preparation method according to claim 4, characterized in that, The acid etching time for the nickel conductive substrate surface is 1~30 min; preferably 5~10 min.

8. The preparation method according to claim 4, characterized in that, Forming a catalytic layer on the surface of the nickel conductive substrate with a protective layer includes: immersing the nickel conductive substrate with a protective layer in a 0.2-1 M ferric ion solution for 10-30 seconds, removing it, and placing it in air for 1-10 hours to form a NiFe layered double hydroxide on the surface of the nickel conductive substrate with a protective layer.

9. The preparation method according to claim 8, characterized in that, The ferric ion solution includes at least one of Fe(NO3)3, Fe2(SO4)3, and FeCl3.

10. The application of a nickel-based electrode with a phosphate armor layer as described in any one of claims 1 to 3 in the electrolytic oxygen removal reaction in water or seawater.

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