Raney nickel electrode activation method and Raney nickel electrode

Abstract

The invention relates to an activation method of a Raney nickel electrode and the Raney nickel electrode. The activation method comprises the steps of electrode preparation, high-temperature hot alkali treatment, electrochemical anode activation and cleaning and post-treatment. Wherein in the high-temperature hot alkali treatment, a nickel-aluminum alloy sheet is placed in a sodium hydroxide solution with specific concentration and temperature to dissolve surface aluminum to form a primary porous structure; electrochemical anode activation is carried out by taking the treated electrode as an anode and an inert material electrode as a cathode, and deep aluminum is further removed under specific potential and time; and finally cleaning and drying to obtain the activated electrode. Compared with the prior art, the method utilizes the synergistic effect of high-temperature hot alkali and electrochemistry, overcomes the problem that deep aluminum is not dissolved thoroughly in traditional hot alkali treatment, can greatly shorten the activation time, reduce aluminum residues and protect the electrode structure, has the advantages of simplicity in operation, environmental protection, high efficiency and the like, improves the catalytic performance and stability of the Raney nickel electrode, and is suitable for industrial production. The method is suitable for industrial production application.

Description

Technical Field

[0001] The invention relates to an electrode activation method, in particular to an activation method of a Raney nickel electrode and the Raney nickel electrode. Background Art

[0002] Raney nickel is an important catalytic material. Due to its excellent catalytic performance and high specific surface area, it is widely used in chemical synthesis, petroleum processing, alkaline water electrolysis and other fields. In the process of alkaline water electrolysis, Raney nickel electrode can effectively reduce the overpotential of hydrogen evolution reaction and improve the reaction efficiency. However, there are some key technical bottlenecks in its preparation and activation process, which limits the further optimization of its industrial application.

[0003] The preparation of Raney nickel is usually completed through a nickel-aluminum alloy melting process. The specific method is to mix nickel and aluminum in a certain proportion, heat them to a molten state, and then cast them into shape. The alloy is treated with high-temperature hot alkali to dissolve aluminum to form a porous structure, which greatly increases the surface area, thereby obtaining excellent catalytic performance. However, nickel and aluminum are fully mixed during the melting process to form a dense solid solution structure. The characteristics of this structure make it possible for aluminum to only gradually dissolve from the surface to the inside during the hot alkali dissolution process, while the deep aluminum is difficult to completely dissolve due to the nickel coating and structural barriers, resulting in an incomplete activation effect.

[0004] In industrial applications, deep aluminum that has not been completely dissolved becomes a potential problem. With the long-term use of the electrode, this residual aluminum may gradually dissolve from the Raney nickel matrix and react with the electrolyte, which not only causes corrosion to the equipment, but also may form impurity deposits and reduce the purity of the electrolyte. In addition, the dissolution of residual aluminum will also reduce the mechanical strength and conductivity of the Raney nickel electrode, significantly affecting the service life and operating efficiency of the equipment.

[0005] To address this problem, the traditional solution is to promote the dissolution of aluminum by extending the hot alkali treatment time or increasing the hot alkali concentration. However, these methods have obvious limitations. On the one hand, long-term hot alkali treatment can easily lead to excessive corrosion of the Raney nickel structure, thereby reducing the stability and service life of the electrode; on the other hand, increasing the hot alkali concentration will increase the danger of operation and environmental risks, and the effect on the dissolution of deep aluminum is still limited.

[0006] Based on the above background, researchers have begun to explore new activation methods in recent years. For example, pretreatment with chemical reagents or the auxiliary use of ultrasound to enhance the dissolution rate of aluminum. However, these methods still have many shortcomings, such as complex operation, high cost and high equipment requirements. Chemical reagent treatment may introduce new impurities or produce waste liquid pollution, and the application of ultrasound requires high-energy consumption equipment, which is difficult to promote on an industrial scale. Summary of the invention

[0007] The purpose of the present invention is to provide a method for activating a Raney nickel electrode and a Raney nickel electrode in order to overcome the defects of the above-mentioned prior art, aiming to efficiently and thoroughly remove deep aluminum in the nickel-aluminum alloy, thereby significantly improving the catalytic performance and stability of the Raney nickel electrode.

[0008] The process of the present invention includes:

[0009] The electrochemical method provides a new idea for solving the problem of Raney nickel activation. The standard electrode potential of aluminum is -1.66V (relative to the standard hydrogen electrode), which is significantly lower than the electrode potential of nickel. Therefore, by applying an anode potential between the potentials of aluminum and nickel, aluminum can be selectively oxidized and dissolved without affecting the structure of nickel. This method can not only effectively remove deep aluminum, but also avoid excessive corrosion of the main structure of Raney nickel during hot alkali treatment. In addition, electrochemical treatment has the advantages of strong controllability, simple operation, and environmental protection, which is very suitable for industrial applications. By introducing electrochemical activation means in high-temperature hot alkali solution, the activation efficiency of Raney nickel electrode can be significantly improved. Specifically, high-temperature hot alkali solution can accelerate the chemical dissolution of surface aluminum, while electrochemical action further increases the dissolution rate of deep aluminum. The two form a synergistic effect and greatly shorten the processing time. At the same time, this method can be modified in conventional electrolytic cells, does not require complex special equipment, has strong adaptability, and has great application potential.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] A first aspect of the present invention provides a method for activating a Raney nickel electrode, comprising the following steps:

[0012] S1. Electrode preparation: Cut the nickel-aluminum alloy sheet into a predetermined size and then clean and dry it;

[0013] S2, high temperature hot alkali treatment: soak the nickel aluminum alloy sheet treated in S1 in a sodium hydroxide solution with a concentration of 10wt%-30wt%, and keep the solution temperature at 80℃-100℃ for 0.5-2 hours to dissolve the surface aluminum and initially form a porous structure;

[0014] S3, electrochemical anode activation: the electrode material treated by S2 is used as the anode, the electrode made of inert material is used as the cathode, the electrolyte is 10wt%-30wt% sodium hydroxide solution, the anode potential is controlled at 0.5V-1.0V, and the electrochemical treatment time is 1-3 hours;

[0015] S4, cleaning and post-treatment: The electrode material treated in S3 is rinsed with deionized water to remove residual alkali solution and dissolved products on the electrode surface, and dried to obtain an activated Raney nickel electrode.

[0016] Furthermore, in S1, the cleaning method is a combination of ultrasonic cleaning and chemical reagent cleaning, and the chemical reagent includes one or more of ethanol, acetone, and hydrochloric acid solution. After cleaning, it is dried by blowing with nitrogen.

[0017] Furthermore, in S2, the concentration of the sodium hydroxide solution is adjusted according to the aluminum content in the nickel-aluminum alloy. When the aluminum content is higher than 20wt%, a 20wt%-30wt% sodium hydroxide solution is used, and when the aluminum content is lower than 20wt%, a 10wt%-20wt% sodium hydroxide solution is used.

[0018] Further, in S2, the processing temperature is controlled within the range of ±2°C of the set temperature by a PID temperature controller.

[0019] Furthermore, in S2, the processing time is linearly adjusted within 0.5-2 hours according to the thickness of the nickel-aluminum alloy sheet, and the processing time is increased by 0.1 hour for every 0.1 cm increase in thickness.

[0020] Furthermore, in S3, the cathode made of the inert material is selected from one of a platinum electrode, a titanium-based ruthenium dioxide coated electrode, and a graphite electrode.

[0021] Furthermore, in S3, the anode potential is controlled by a constant potentiostat with a control accuracy of ±0.05V, and the electrochemical treatment time is determined according to the initial aluminum content of the anode electrode and the target aluminum residue. When the initial aluminum content is higher than 15wt%, the treatment time is 2-3 hours, and when the initial aluminum content is lower than 15wt%, the treatment time is 1-2 hours.

[0022] Further, in S4, the number of times of rinsing with deionized water is no less than 5 times, and each rinsing time is 5-10 minutes;

[0023] In S4, the drying process adopts vacuum drying, the drying temperature is 120° C.-180° C., the drying time is 1-3 hours, and the dried electrode is stored in an environment with a humidity lower than 30%.

[0024] Furthermore, in S2 and S3, in the synergistic process of high-temperature hot alkali treatment and electrochemical anode activation, the high temperature intensifies the movement of hydroxide ions in the sodium hydroxide solution, and the frequency of their collision with aluminum atoms on the electrode surface increases, accelerating the chemical dissolution of surface aluminum. At the same time, during electrochemical anode activation, the anode potential causes the outer electrons of aluminum atoms to move in a directed manner and detach, forming more active sites. These active sites further promote the chemical reaction between hydroxide ions and aluminum atoms, thereby significantly improving the dissolution rate of deep aluminum.

[0025] A second aspect of the present invention provides a Raney nickel electrode prepared by the above activation method.

[0026] Compared with the prior art, the present invention has the following advantages.

[0027] First, the present invention overcomes the problem that traditional hot alkali treatment is difficult to completely dissolve deep aluminum by electrochemical selective oxidation, and significantly improves the activation efficiency of Raney nickel electrode. Compared with relying solely on hot alkali treatment, the present invention can greatly shorten the activation time and reduce the subsequent equipment corrosion and catalytic performance degradation caused by aluminum residues.

[0028] Secondly, the method accurately controls the anode potential and utilizes the oxidation potential difference between aluminum and nickel to ensure that only aluminum is oxidized without affecting the integrity of the porous structure of nickel, effectively avoiding the decrease in electrode strength and loss of catalytic activity caused by excessive corrosion. At the same time, the present invention does not require the introduction of additional chemical reagents during operation, and the main byproduct produced during the activation process is aluminum oxide, which has good environmental protection characteristics and can meet the needs of green production.

[0029] In addition, this method has simple process and strong controllability, can be seamlessly connected with existing industrial electrolysis equipment, and can be applied on a large scale through appropriate modification. It has significant economy and scalability.

[0030] Finally, the Raney nickel electrode prepared by the present invention has a higher specific surface area and better catalytic performance, and exhibits a lower hydrogen evolution overpotential and a longer service life in applications such as alkaline water electrolysis to produce hydrogen, thereby significantly improving the operating efficiency of industrial equipment.

[0031] Therefore, the present invention shows obvious advantages in terms of process efficiency, environmental protection, industrial feasibility and performance improvement, and is an important innovative breakthrough in the preparation technology of Raney nickel electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the porous structure of activated Raney nickel in the example. DETAILED DESCRIPTION

[0033] In general, the present invention proposes a method for activating a Raney nickel electrode based on the synergistic effect of electrochemistry and hot alkali, which aims to efficiently and thoroughly remove deep aluminum in nickel-aluminum alloys, thereby significantly improving the catalytic performance and stability of the Raney nickel electrode. The technical solution of the present invention mainly includes the following steps:

[0034] 1. Preparation of Raney Nickel Electrode

[0035] Cut the prepared nickel-aluminum alloy sheet into the required size of the electrode (e.g., 5×5 cm);

[0036] Wash and dry for later use.

[0037] 2. High temperature hot alkali treatment

[0038] Immerse the electrode in a high-temperature hot alkaline solution to dissolve the aluminum on the surface of the nickel-aluminum alloy and initially form a porous structure:

[0039] Solution selection: Use 10wt%-30wt% sodium hydroxide (NaOH) solution, and the concentration is adjusted according to the aluminum content;

[0040] Temperature control: The solution temperature is maintained at 80°C to 100°C. High temperature helps accelerate the dissolution of aluminum.

[0041] Time setting: The hot alkali treatment time is 0.5-2 hours, depending on the thickness and aluminum content of the nickel-aluminum alloy;

[0042] Initial results: This step mainly dissolves surface aluminum, but the removal efficiency of deep-layer aluminum is limited and requires further electrochemical treatment.

[0043] 3. Electrochemical Anodic Activation

[0044] The Raney nickel electrode treated with high temperature hot alkali is used as the anode and placed in an electrochemical device for activation treatment:

[0045] (1) Device Setup

[0046] Anode: Raney nickel electrode;

[0047] Cathode: Made of inert material (such as titanium-based coating electrode or platinum electrode);

[0048] Electrolyte: Continue with high temperature hot alkaline solution (10wt%-30wt% NaOH) to ensure high conductivity and continuous aluminum dissolution.

[0049] (2) Potential control

[0050] The anode potential is controlled at 0.5 V to 1.0 V (relative to the standard electrode potential of aluminum);

[0051] Within this potential range, aluminum will selectively oxidize and dissolve, while nickel will remain stable, preventing the nickel surface from being corroded or damaged.

[0052] (3) Processing time

[0053] The electrochemical treatment time is 1-3 hours, which is determined by the electrode thickness and the residual amount of deep aluminum;

[0054] After the treatment, the aluminum was almost completely removed, and the porous structure of the electrode was formed and stabilized.

[0055] 4. Cleaning and post-processing

[0056] After the electrochemical activation is completed, the electrode is removed from the electrolytic cell and the following treatments are performed:

[0057] Cleaning: Use deionized water to thoroughly rinse the residual alkali and dissolved products (such as aluminum oxide) on the electrode surface;

[0058] Drying: Place the cleaned electrode in a drying oven at 100°C to 200°C to ensure complete dehydration;

[0059] Storage: Store the dried electrode in a sealed container to prevent the performance from being affected by environmental humidity.

[0060] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Any features such as preparation means, materials, structures or composition ratios not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0061] Example 1

[0062] Activation Treatment of Raney Nickel Electrode

[0063] (1) Material preparation

[0064] The electrode sheet is made of nickel-aluminum alloy, with a size of 5cm×5cm×0.5cm, in which nickel accounts for 80wt% and aluminum accounts for 20wt%.

[0065] Clean the electrode surface to remove oxides and impurities, rinse with deionized water, and dry for later use.

[0066] (2) High temperature hot alkali pretreatment

[0067] A sodium hydroxide solution with a mass fraction of 20 wt% and a volume of 500 mL was prepared and added into an alkali corrosion-resistant electrolytic cell.

[0068] The solution was heated to 100°C and kept at a constant temperature, and the nickel-aluminum alloy electrode was completely immersed in the hot alkaline solution for 60 minutes to dissolve the surface aluminum and form a preliminary porous structure.

[0069] (3) Electrochemical anode activation

[0070] a. Device Setup

[0071] The hot alkaline solution continues to be used as the electrolyte.

[0072] The Raney nickel electrode was used as the anode, and the titanium-based coated electrode was used as the cathode, with a distance of 2 cm between the two electrodes.

[0073] Use a controllable power supply to provide a constant current or potential.

[0074] b. Parameter setting

[0075] The electrolysis current density was set to 10 mA / cm 2 ;

[0076] The anode potential was controlled at 0.6 V (relative to the standard electrode potential of aluminum);

[0077] The electrochemical treatment time was 120 minutes.

[0078] c. Process monitoring

[0079] During the treatment process, the progress of aluminum dissolution is judged by the solution color change and gas generation;

[0080] After the test, remove the electrode and rinse it several times with deionized water to ensure that the dissolved products in the solution are completely removed.

[0081] (4) Drying and post-processing

[0082] The cleaned Raney nickel electrode was placed in an oven and dried at 120°C for 2 hours to ensure that the moisture inside and on the surface of the electrode was completely evaporated.

[0083] (5) Electrode detection

[0084] Scanning electron microscopy (SEM) was used to observe the porous structure of activated Raney nickel. Figure 1 The porous structure of Raney nickel after activation shows that the activated electrode forms a rich porous structure. The residual components of nickel and aluminum in the electrode were measured using an inductively coupled plasma optical emission spectrometer (ICP-OES). It can be found that the aluminum content of the electrode after electro-activation is significantly reduced compared to the common alkali solution activation method.

[0085] See Table 1, which is a comparison of the nickel and aluminum content after simple alkali activation and electrochemical activation. It can be found that the aluminum removal effect is significantly improved after adding electrochemical activation.

[0086] Table 1

[0087]

[0088] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for activating a Raney nickel electrode, characterized in that: The following steps are involved: S1. Electrode preparation: Cut the nickel-aluminum alloy sheet into a predetermined size and then clean and dry it; S2, high temperature hot alkali treatment: soak the nickel aluminum alloy sheet treated in S1 in a sodium hydroxide solution with a concentration of 10wt%-30wt%, and keep the solution temperature at 80℃-100℃ for 0.5-2 hours to dissolve the surface aluminum and initially form a porous structure; S3, electrochemical anode activation: the electrode material treated by S2 is used as the anode, the electrode made of inert material is used as the cathode, the electrolyte is 10wt%-30wt% sodium hydroxide solution, the anode potential is controlled at 0.5V-1.0V, and the electrochemical treatment time is 1-3 hours; S4, cleaning and post-treatment: The electrode material treated in S3 is rinsed with deionized water to remove residual alkali solution and dissolved products on the electrode surface, and dried to obtain an activated Raney nickel electrode.

2. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S1, the cleaning method is a combination of ultrasonic cleaning and chemical reagent cleaning, wherein the chemical reagent includes one or more of ethanol, acetone, and hydrochloric acid solution, and after cleaning, the surface is dried by blowing with nitrogen.

3. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S2, the concentration of the sodium hydroxide solution is adjusted according to the aluminum content in the nickel-aluminum alloy. When the aluminum content is higher than 20wt%, a 20wt%-30wt% sodium hydroxide solution is used, and when the aluminum content is lower than 20wt%, a 10wt%-20wt% sodium hydroxide solution is used.

4. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S2, the processing temperature is controlled within the range of ±2°C of the set temperature by a PID temperature controller.

5. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S2, the processing time is linearly adjusted within 0.5-2 hours according to the thickness of the nickel-aluminum alloy sheet, and the processing time increases by 0.1 hour for every 0.1 cm increase in thickness.

6. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S3, the cathode made of inert material is selected from one of a platinum electrode, a titanium-based ruthenium dioxide coated electrode, and a graphite electrode.

7. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S3, the anode potential is controlled by a constant potential meter with a control accuracy of ±0.05V. The electrochemical treatment time is determined according to the initial aluminum content of the anode electrode and the target aluminum residue. When the initial aluminum content is higher than 15wt%, the treatment time is 2-3 hours, and when the initial aluminum content is lower than 15wt%, the treatment time is 1-2 hours.

8. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S4, the number of rinses with deionized water is no less than 5 times, and each rinse time is 5-10 minutes; In S4, the drying process adopts vacuum drying, the drying temperature is 120° C.-180° C., the drying time is 1-3 hours, and the dried electrode is stored in an environment with a humidity lower than 30%.

9. The method for activating a Raney nickel electrode according to claim 1, characterized in that: In S2 and S3, in the synergistic process of high-temperature hot alkali treatment and electrochemical anode activation, the high temperature intensifies the movement of hydroxide ions in the sodium hydroxide solution, and the frequency of their collision with aluminum atoms on the electrode surface increases, accelerating the chemical dissolution of surface aluminum. At the same time, during electrochemical anode activation, the anode potential prompts the outer electrons of aluminum atoms to move in a directed manner and detach, forming more active sites. These active sites further promote the chemical reaction between hydroxide ions and aluminum atoms, significantly improving the dissolution rate of deep aluminum.

10. A Raney nickel electrode prepared by the activation method according to any one of claims 1 to 9.

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