Matrix pretreatment process applied to integrated electrode material

Abstract

The invention discloses a substrate pretreatment process applied to an integrated electrode material, and belongs to the technical field of electrode material preparation. The process sequentially comprises the steps of substrate pretreatment, micro-etching, rough nickel deposition and embroidered ball array skeleton electrodeposition, and a micron-sized rough structure is constructed on the surface of a nickel-based porous substrate through micro-etching so as to provide more nucleation sites; on the basis that rough nickel is deposited on the rough surface of a base body, a compact amorphous metal nickel transition layer is formed, strong mechanical interlocking with the base body is achieved, and high corrosion resistance and high conductivity are achieved; and finally, growing a vertically-oriented nanowire array framework on the metal nickel transition layer by utilizing electro-deposition. Through the synergistic effect of micro-etching, rough nickel deposition and electro-deposition, a complete, stable and efficient three-dimensional conductive carrier from a macroscopic matrix to a microcosmic active skeleton is finally constructed, and the binding force between the integrated electrode material and the matrix, the interface stability and the mass transfer capacity are fundamentally improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode material preparation, and particularly relates to a substrate pretreatment process applied to integrated electrode material. BACKGROUND

[0002] In the field of alkaline water electrolysis hydrogen production, the oxygen evolution reaction (OER) occurring at the anode is one of the key steps that restrict the overall electrolysis efficiency. Currently, the alkaline electrolyzer widely used in industry usually takes nickel mesh as the electrode substrate. However, this traditional structure has several inherent defects, which limit the further improvement of the performance of the electrolyzer.

[0003] Firstly, the nickel mesh substrate is essentially a two-dimensional planar structure, and its inherent specific surface area is limited, resulting in insufficient number of active sites available for reaction. This makes the intrinsic catalytic activity of the electrode at low overpotential not high enough to meet the needs of efficient and high current density operation.

[0004] Secondly, in order to improve activity, the existing technology generally deposits or coats a catalyst layer directly on the surface of the nickel mesh substrate. However, there is often a lack of strong chemical bonding and mechanical interlocking between the catalyst layer and the metal substrate, and the bonding force is weak. Under the condition of continuous severe oxygen evolution at the anode, the generation and escape of a large amount of oxygen will continuously impact and stress the coating, which can easily lead to the pulverization, peeling and even falling off of the catalyst layer. This problem seriously damages the long-term operation stability and service life of the electrode, and is one of the main bottlenecks in industrial application.

[0005] Thirdly, even if the electrode is loaded with a catalyst, its structure is often relatively simple. The dense or disordered catalyst layer will hinder the effective diffusion of the electrolyte to the active sites (mass transfer is limited), and is also not conducive to the rapid detachment of the oxygen bubbles generated by the reaction. The attachment and accumulation of the bubbles will cover part of the active sites, increasing the reaction impedance. In addition, the electronic conduction path inside the catalyst layer may not be smooth enough. These bottlenecks in mass transfer and charge transfer jointly restrict the performance of the electrode at high current density, leading to a significant increase in polarization voltage and an increase in energy consumption.

[0006] In order to overcome the problem of insufficient specific surface area, some studies attempt to construct a three-dimensional porous structure through complex template methods, high-temperature sintering or hydrothermal synthesis processes. Although these methods can increase the surface area to some extent, they usually involve complicated steps, harsh process conditions or expensive equipment, resulting in a complex preparation process and high cost. SUMMARY

[0007] To address the aforementioned technical problems, this invention provides a substrate pretreatment process for integrated electrode materials. This process aims to enhance the adhesion between the integrated electrode material and the substrate through a three-step synergistic treatment involving micro-etching, metal interlayer deposition, and nano-conductive framework construction, while also exhibiting excellent interfacial stability and mass transfer capabilities.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: To address the aforementioned technical problems, this invention provides a substrate pretreatment process for integrated electrode materials. This process is a coherent and functionally synergistic system, comprising the following steps in sequence: Substrate pretreatment: Nickel-based porous substrates such as nickel foam or woven nickel mesh are subjected to alkaline washing and acid washing to thoroughly remove surface oil, oxides, and other impurities, obtaining a clean and activated initial surface. The nickel foam substrate has a PPI of 30-130, an areal density of 180-1000 g / m², and a thickness of 0.5-5.0 mm; the woven nickel mesh has a mesh count of 1-600 and a wire diameter of 0.03-10.00 mm. Alkaline washing uses a 60-80 g / L sodium hydroxide solution at room temperature for 1-3 minutes; acid washing uses a 10-15% (v / v) dilute hydrochloric acid solution at room temperature for 20-60 seconds. Micro-etching: A specific chemical etching solution system (such as dilute sulfuric acid followed by sodium thiosulfate solution) is used to gently and controllably etch a clean substrate. This step forms a uniform micron-scale rough structure on the substrate surface (including the inner wall of the pores), significantly increasing the actual specific surface area and generating a large number of steps, edges, and defects on the surface. These locations have high surface energy and can serve as ideal "nucleation sites" in subsequent deposition processes, thus providing the physical basis for building a strong bonding interface for subsequent processes. Specifically, micro-etching involves immersing the substrate in a sulfuric acid solution with a volume concentration of 8-12% for 3-5 minutes at room temperature; then immersing the substrate in a sodium thiosulfate solution with a concentration of 5-10 g / L for 30-180 seconds at room temperature. Rough Nickel Deposition (Preparation of Amorphous Nickel Intermediate Layer): First, the etching solution on the substrate surface is removed by washing with water. Then, the micro-etched substrate is immersed in a chemical nickel plating solution. Through an autocatalytic reduction reaction, a layer of metallic nickel is deposited on the substrate surface. By controlling the complexing agent, stabilizer, and process parameters, the nickel deposition layer exhibits an amorphous structure. This amorphous nickel layer can fully wet and densely encapsulate the rough contours created by micro-etching, forming a strong mechanical interlocking structure similar to "mortise and tenon," with a bonding force far superior to planar adhesion. Moreover, since the amorphous structure lacks grain boundaries, it eliminates the channels for preferential corrosion at grain boundaries, giving this intermediate layer excellent corrosion resistance in strongly alkaline, high-potential anodic environments. Simultaneously, this intermediate layer can also serve as a metallic continuum homogeneous with the substrate, providing excellent electronic conductivity. The composition of the chemical nickel plating solution is: NiSO4. The chemical nickel plating solution contains 80-90 g / L H₂O, 0.001-0.01 g / L thiourea, 30-40 g / L EDTA, 1-3 mL / L lactic acid, 30-40 g / L sodium hypophosphite, and 40-50 g / L sodium citrate. The pH of the solution is 8-9, the deposition temperature is 70-80℃, and the deposition time is 20-60 minutes. Electrodeposition of a "Hydrangea Ball" Array Framework (Construction of a Three-Dimensional Nanoconductive Framework): Using a substrate coated with an amorphous nickel intermediate layer as the cathode, electrodeposition is performed in an electrodeposition nickel solution. Due to the highly uniform chemical properties and lack of specific crystallographic orientation (isotropy) on the surface of the amorphous nickel layer, uniform nucleation sites are provided for nickel / nickel hydroxide deposition. This allows nanowires to grow vertically, uniformly, and densely, forming a three-dimensional interconnected porous "Hydrangea Ball" array framework. This framework forms a strong metallurgical bond with the amorphous nickel layer through an electrocrystallization process and inherits its excellent conductivity. The composition of the electrodeposition nickel solution is: nickel sulfate 130-180 g / L, nickel chloride 80-100 g / L, boric acid 30-40 g / L, and thiocarbamate 0.1-1.5 g / L. The pH value of the electrodeposition nickel solution is 4.0-5.0, the deposition temperature is 50-65℃, the cathode current density is 2-6 A / dm², and the deposition time is 180-600 seconds.

[0009] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) The mechanical interlocking achieved by the present invention through “micro-etching morphology + amorphous nickel filling”, the rough surface and high-density nucleation sites created by micro-etching provide the prerequisite for the dense coverage and strong mechanical interlocking of the rough nickel layer; at the same time, the metallurgical combination of electrodeposited nanowires and intermediate amorphous nickel layer causes a qualitative change in the bonding force between the active material and the substrate, effectively preventing detachment under harsh working conditions. (2) The present invention forms an amorphous nickel layer by rough nickel deposition. Based on the amorphous nickel layer as an intermediate barrier, it blocks the electrolyte from penetrating into the substrate and corroding the interface, which significantly improves the corrosion resistance of the electrode material. This allows the electrode to maintain structural integrity under long-term high-potential working conditions, thus extending its service life in strong oxidizing environments (such as OER). At the same time, the amorphous nickel layer ensures low interfacial resistance. Combined with the huge electrochemical active area and open mass transfer channels provided by the three-dimensional nanowire array, it synergistically improves the mass transfer performance of the electrode. (3) The entire process of this invention is completed in the liquid phase at medium and low temperatures. The conditions are mild and the parameters are controllable. It is applicable to nickel-based porous materials of different specifications and has good repeatability and potential for large-scale production. Attached Figure Description

[0010] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0011] Figure 1 This is a flowchart of a matrix pretreatment process applied to an integrated electrode material in some embodiments of this application; Figure 2 This is a SEM image of the substrate after micro-etching in Embodiment 1 of this application under 1000x magnification. Figure 3 This is a SEM image of the substrate after rough nickel deposition in Example 1 of this application under 1000x magnification. Figure 4 This is a SEM image of the substrate after electrodeposition on the embroidered ball array skeleton in Embodiment 1 of this application at 400x magnification. Detailed Implementation

[0012] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way.

[0013] Example 1 Nickel foam was selected as the nickel-based porous matrix, based on the matrix pretreatment process for application in integrated electrode materials. 1) Matrix pretreatment: Take a piece of nickel foam with a PPI of 60, a surface density of 400 g / m², and a thickness of 1.5 mm, and immerse it in 70 g / L NaOH solution (room temperature, 2 minutes) and 12% dilute hydrochloric acid solution (room temperature, 40 seconds) for cleaning, and then rinse with deionized water. 2) Micro-etching: Immerse the cleaned nickel foam in a 10% (v / v) sulfuric acid solution at room temperature for 4 minutes; then transfer it to an 8 g / L sodium thiosulfate solution and immerse it at room temperature for 90 seconds, followed by rinsing with deionized water. Figure 2 As shown, Figure 2 This example shows a SEM image of the substrate after micro-etching at 1000x magnification. Figure 2 As can be seen, after micro-etching, the pretreated substrate forms a uniform micron-scale rough structure on its surface, which significantly increases the specific surface area; at the same time, a large number of steps, edges and defects are generated on the surface, which can serve as ideal nucleation sites in the subsequent deposition process. 3) Rough nickel deposition: Preparation of electroless nickel plating solution: NiSO4 6H₂O 85 g / L, thiourea 0.005 g / L, EDTA 35 g / L, lactic acid 2 mL / L, sodium hypophosphite 35 g / L, sodium citrate 45 g / L; adjust pH to 8.5 with ammonia; immerse the micro-etched nickel foam in the electroless nickel plating solution and plate at 75℃ for 40 minutes, then remove and rinse with deionized water. Figure 3 As shown, Figure 3 This example shows a SEM image of the substrate after rough nickel deposition at 1000x magnification. Figure 3 As can be seen, after rough nickel deposition, a dense and uniform amorphous nickel layer is formed on the substrate surface. Since the amorphous structure has no grain boundaries, the grain boundary corrosion channels are fundamentally eliminated, giving it extremely high corrosion resistance and making it suitable for harsh oxygen evolution environments. At the same time, the amorphous nickel layer and the substrate foam nickel are of the same type of metal, and their conductivity is far superior to that of dissimilar metals, further ensuring the rapid transfer of electrons from the substrate to the surface and providing a perfect "foundation" for the next step of growing nanowire arrays. In addition, based on the corrosion barrier provided by the amorphous nickel layer, combined with the mechanical anchoring provided by the amorphous nickel layer and micro-etching, the bonding force between the amorphous nickel layer and the substrate foam nickel undergoes a qualitative change, which can effectively prevent detachment under harsh working conditions. 4) Electrodeposition of the embroidered ball array skeleton: Prepare the electrodeposition nickel solution: nickel sulfate 150 g / L, nickel chloride 90 g / L, boric acid 35 g / L, thiocarbamate 0.8 g / L, and adjust the pH to 4.5 with dilute sulfuric acid. Use rough nickel-deposited foam nickel as the cathode and a pure nickel plate as the anode. Electrodeposition is performed for 300 seconds at 60℃ and a cathode current density of 4 A / dm². After removal, wash with deionized water and dry. Figure 4 As shown, Figure 4 This example shows a SEM image of the electrodeposited substrate at 400x magnification. Figure 4 As can be seen, after electrodeposition on the embroidered ball array framework, a vertically oriented embroidered ball composite nanowire array grows on the surface of the collective nickel foam. Due to the surface energy and isotropy of the amorphous nickel layer, the embroidered ball composite nanowire array is not only more uniform and denser, but also has a stronger bond with the substrate nickel foam.

[0014] Example 2 1) Matrix pretreatment: Take a piece of nickel foam with a PPI of 130, a surface density of 1000 g / m², and a thickness of 5.0 mm, and immerse it in 80 g / L NaOH solution (room temperature, 1 minute) and 15% dilute hydrochloric acid solution (room temperature, 20 seconds) for cleaning, and then rinse with deionized water. 2) Micro-etching: Immerse the cleaned nickel foam in a 12% (v / v) sulfuric acid solution at room temperature for 3 minutes; then transfer it to a 10 g / L sodium thiosulfate solution at room temperature for 30 seconds, and rinse with deionized water. 3) Rough nickel deposition: Preparation of electroless nickel plating solution: NiSO4 6H2O 90 g / L, thiourea 0.01 g / L, EDTA 40 g / L, lactic acid 3 mL / L, sodium hypophosphite 40 g / L, sodium citrate 50 g / L, adjust pH to 9 with ammonia; immerse the micro-etched nickel foam in the electroless nickel plating solution and plate at 80℃ for 20 minutes, then remove and rinse with deionized water; 4) Electrodeposition of the embroidered ball array skeleton: Prepare the electrodeposition nickel solution: nickel sulfate 180 g / L, nickel chloride 100 g / L, boric acid 40 g / L, thiocarbamate 1.5 g / L, and adjust the pH to 5.0 with dilute sulfuric acid. Use the rough nickel-deposited foam nickel as the cathode and the pure nickel plate as the anode. Electrodeposition is performed for 600 seconds at 65℃ and a cathode current density of 2 A / dm². After removal, wash with deionized water and dry.

[0015] Example 3 1) Matrix pretreatment: Take a piece of nickel foam with a PPI of 30, a surface density of 180 g / m², and a thickness of 0.5 mm, and immerse it in 60 g / L NaOH solution (room temperature, 3 minutes) and 10% dilute hydrochloric acid solution (room temperature, 60 seconds) for cleaning, and then rinse with deionized water. 2) Micro-etching: Immerse the cleaned nickel foam in an 8% (v / v) sulfuric acid solution at room temperature for 5 minutes; then transfer it to a 5 g / L sodium thiosulfate solution at room temperature for 180 seconds, and rinse with deionized water. 3) Rough nickel deposition: Preparation of electroless nickel plating solution: NiSO4 6H2O 80 g / L, thiourea 0.001 g / L, EDTA 30 g / L, lactic acid 1 mL / L, sodium hypophosphite 30 g / L, sodium citrate 40 g / L, adjust pH to 8 with ammonia; immerse the micro-etched nickel foam in the electroless nickel plating solution and plate at 70℃ for 60 minutes, then remove and rinse with deionized water; 4) Electrodeposition of the embroidered ball array skeleton: Prepare the electrodeposition nickel solution: nickel sulfate 130 g / L, nickel chloride 80 g / L, boric acid 30 g / L, thiocarbamate 0.1 g / L, and adjust the pH to 4.0 with dilute sulfuric acid. Use the rough nickel-deposited foam nickel as the cathode and the pure nickel plate as the anode. Electrodeposition is performed for 180 seconds at 50℃ and a cathode current density of 6 A / dm². After removal, wash with deionized water and dry.

[0016] Comparative Example 1 Using the same substrate as in Example 1, but omitting steps 2) and 3), the pretreated nickel foam was directly electrodeposited in step 4) in an attempt to grow a nanowire array.

[0017] The bonding strength and electrochemical active area properties of the matrices treated in Examples 1-3 and Comparative Example 1 were tested. The test results are shown in Table 1. The specific test process is as follows: Adhesion test: The substrate sample was peeled off multiple times using the tape peeling method to observe whether the nanowire array deposited on the substrate sample was detached.

[0018] Tests showed that the substrate samples obtained in Examples 1-3 remained intact after 10 exfoliation tests without any detachment; however, the substrate sample obtained in Comparative Example 1 showed significant detachment of the catalyst layer deposited on its surface after the first exfoliation test. This indicates that the substrate pretreatment process provided in Examples 1-3 effectively enhanced the interfacial adhesion.

[0019] Electrochemical active area (ECSA) assessment: Measure and estimate the double-layer capacitance of the substrate sample.

[0020] The ECSA of the matrix samples obtained in Examples 1-3 was measured to be 8-10 times that of the matrix sample obtained in Comparative Example 1. This indicates that the matrix pretreatment process provided in Examples 1-3 significantly increased the actual active area of ​​the matrix compared to Comparative Example 1.

[0021] In summary, the substrate pretreatment process provided by this invention, through the synergistic effect of micro-etching, rough nickel deposition, and electrodeposition, successfully prepared an ideal electrode substrate with strong adhesion, high stability, and large active area, and the effect is significant.

[0022] The foregoing has provided a detailed description of a substrate pretreatment process for integrated electrode materials. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A substrate pretreatment process for integrated electrode materials, characterized in that, The pretreatment process includes the following steps: Substrate pretreatment: The nickel-based porous substrate is cleaned to remove surface impurities; Micro-etching: The pretreated substrate is chemically etched to roughen the substrate surface, increase its actual specific surface area, and form more nucleation sites; Rough Nickel Deposition: The micro-etched substrate is placed in a chemical nickel plating solution for autocatalytic deposition to form a dense, continuous amorphous metallic nickel intermediate layer on the roughened substrate surface; this intermediate layer forms a strong mechanical interlocking structure with the substrate by filling and encapsulating the surface contours formed by micro-etching. Electrodeposition of embroidered ball array framework: Using a substrate with an amorphous metallic nickel interlayer as the cathode, electrochemical deposition is performed in an electrodeposition nickel solution to grow a vertically oriented nanowire array framework on the interlayer.

2. The substrate pretreatment process according to claim 1, characterized in that, The nickel-based porous matrix is ​​a foamed nickel matrix or a woven nickel mesh matrix.

3. The substrate pretreatment process according to claim 2, characterized in that, The foamed nickel matrix has a PPI of 30-130, an areal density of 180-1000 g / m², and a thickness of 0.5-5.0 mm; the woven nickel mesh has a mesh count of 1-600 and a wire diameter of 0.03-10.00 mm.

4. The substrate pretreatment process according to claim 3, characterized in that, The surface cleaning includes alkaline cleaning and acid cleaning. The alkaline cleaning uses a sodium hydroxide solution with a concentration of 60-80 g / L and cleans for 1-3 minutes at room temperature. The acid cleaning uses a dilute hydrochloric acid solution with a volume concentration of 10-15% and cleans for 20-60 seconds at room temperature.

5. The substrate pretreatment process according to claim 4, characterized in that, The micro-etching process specifically involves: first immersing the substrate in a sulfuric acid solution with a volume concentration of 8-12% for 3-5 minutes at room temperature; then immersing the substrate in a sodium thiosulfate solution with a concentration of 5-10 g / L for 30-180 seconds at room temperature.

6. The substrate pretreatment process according to claim 5, characterized in that, The composition of the electroless nickel plating solution is: NiSO4 The chemical nickel plating solution contains 80-90 g / L 6H2O, 0.001-0.01 g / L thiourea, 30-40 g / L EDTA, 1-3 mL / L lactic acid, 30-40 g / L sodium hypophosphite, and 40-50 g / L sodium citrate. The pH value of the solution is 8-9.

7. The substrate pretreatment process according to claim 6, characterized in that, The temperature for rough nickel deposition is 70-80℃, and the deposition time is 20-60 minutes.

8. The matrix pretreatment process according to claim 1, characterized in that, The composition of the electrodeposition nickel solution for the embroidered ball array skeleton is as follows: nickel sulfate 130-180 g / L, nickel chloride 80-100 g / L, boric acid 30-40 g / L, and thiocarbamate 0.1-1.5 g / L, wherein the pH value of the electrodeposition nickel solution is 4.0-5.

0.

9. The substrate pretreatment process according to claim 8, characterized in that, The electrodeposition temperature of the embroidered ball array skeleton is 50-65℃, the cathode current density is 2-6A / dm², and the deposition time is 180-600 seconds.

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