Method for preparing bifunctional electrode, electrode and application

Abstract

The application discloses a preparation method of a bifunctional electrode, the electrode and application, wherein the preparation method comprises the following steps: (1) electroplating solution configuration: taking deionized water as a solvent, sequentially adding nickel sulfate, ammonium sulfate, ammonium chloride and sodium thiosulfate, uniformly stirring, and then adjusting the pH value to 4.5-5.5; (2) electrode pretreatment: taking a nickel wire mesh with double-sided sand blasting as a cathode, and then sequentially removing oil and an oxide layer; and (3) electrochemical deposition: placing the pretreated cathode and a nickel-based tensile mesh anode into the electroplating solution, connecting the cathode and the anode with a power supply negative pole and a positive pole respectively, depositing at a current density of 5-20 mA / cm 2 at room temperature for 30-90 min under constant current, and obtaining the bifunctional electrode. The NiS alloy is prepared by optimizing an electroplating co-deposition process, the dual anti-iron mechanism of a polysulfide protective layer is utilized, the unification of high electrochemical activity and anti-iron adsorption performance is realized, the energy consumption of an electrolytic cell is reduced, and the operation life is prolonged.

Description

[0001] Priority number: 2025120322699, Priority date: 2025 / 12 / 30 Technical Field

[0002] This invention belongs to the field of water electrolysis for hydrogen production technology, specifically relating to a method for preparing a bifunctional electrode, the electrode itself, and its applications. Background Technology

[0003] The technology of producing high-purity hydrogen through electrochemical water splitting without generating carbon dioxide emissions is one of the most promising methods for achieving a sustainable energy pattern. Compared with coal gasification and steam methane reforming, water electrolysis technology has advantages in hydrogen production. In particular, alkaline water electrolysis technology has attracted much attention due to its simple structure and low-cost electrode materials. In recent years, the alkaline water electrolysis industry has developed rapidly and has become particularly mature with decades of application experience, but many problems still need to be solved, such as the iron ion adsorption problem that has troubled researchers. Hydrogen production technology through water electrolysis has become a key technology for achieving a sustainable energy pattern due to its zero carbon dioxide emissions and high hydrogen purity. Among them, alkaline water electrolysis (ALK) technology has achieved large-scale application due to its advantages of simple structure and low cost of electrode materials. However, alkaline electrolyzers face serious iron ion adsorption problems during long-term operation. The sources of iron ions include: corrosion and dissolution of bipolar plates (carbon steel nickel-plated parts), wear and detachment of stainless steel pipelines, dissolution of Fe components in nickel-based electrode coatings, and trace impurities in the electrolyte (potassium hydroxide / nickel hydroxide).

[0004] Iron ions (Fe) 2+ / Fe 3+ After migrating to the cathode surface, iron nucleates and grows to form an iron capping layer, which poisons the cathode through three mechanisms: ① covering the hydrogen evolution active sites, reducing the effective reaction area; ② iron's hydrogen evolution activity in alkaline media is much lower than that of nickel-based catalysts; ③ altering the electronic structure of the cathode surface, deviating from the optimal value of the hydrogen intermediate adsorption free energy. Ultimately, this leads to an increase in the hydrogen evolution overpotential, increased energy consumption of the electrolyzer, and a shortened lifespan.

[0005] In existing technologies, solutions to iron ion poisoning mainly include adding chelating agents to the electrolyte (which increases operating costs and easily introduces new impurities) and using physical barrier coatings (sacrificing electrode electrochemical activity). However, research on nickel-based bifunctional electrodes only focuses on optimizing hydrogen and oxygen evolution performance and does not involve anti-iron adsorption design, which cannot simultaneously meet the industrialization requirements of "high activity + anti-iron poisoning".

[0006] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a method for preparing a bifunctional electrode, the electrode itself, and its applications. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a bifunctional electrode, the electrode itself, and its application. This bifunctional electrode is designed to resist iron adsorption in an alkaline electrolyzer. The catalyst exhibits excellent water-to-water electrolysis performance in alkaline water electrolysis, and features low chamber voltage, ease of preparation, and resistance to iron adsorption. The preparation method is simple, the catalyst cost is low, and it exhibits excellent stability in an alkaline electrolyzer.

[0008] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0009] A method for preparing a bifunctional electrode resistant to iron adsorption in an alkaline electrolytic cell includes the following steps:

[0010] (1) Preparation of electroplating solution: Using deionized water as solvent, add nickel sulfate, ammonium sulfate, ammonium chloride and sodium thiosulfate in sequence, stir evenly and adjust the pH value to 4.5-5.5;

[0011] (2) Electrode pretreatment: A double-sided sandblasted nickel wire mesh is used as the cathode, and then the oil and oxide layer are removed in sequence;

[0012] (3) Electrochemical deposition: The pretreated cathode and nickel-based stretched mesh anode are placed in the electroplating solution, and the cathode and anode are connected to the negative and positive terminals of the power supply, respectively. The electroplating is carried out at room temperature with an input current of 5-20 mA / cm. 2 A constant current deposition at a current density of 30-90 min is used to obtain a bifunctional electrode. Preferably, the bifunctional electrode is a NiS alloy bifunctional electrode.

[0013] In one or more embodiments of the present invention, the electroplating solution in step (1) includes deionized water as a solvent, wherein: the concentration of nickel sulfate is 50-150 g / L, the concentration of ammonium sulfate is 10-50 g / L, the concentration of ammonium chloride is 10-100 g / L, and the concentration of sodium thiosulfate is 100-200 g / L.

[0014] In one or more embodiments of the present invention, the pH value in step (1) is adjusted by hydrochloric acid or sodium hydroxide.

[0015] In one or more embodiments of the present invention, the wire diameter of the nickel-based stretched mesh anode in step (3) is 0.3-0.5 mm.

[0016] In one or more embodiments of the present invention, the electrode pretreatment in step (3) is as follows: a nickel wire mesh with a diameter of 0.25 mm and 46 meshes is used as the cathode and then the electrode is degreased by surfactant and soaked in 3M hydrochloric acid for 10 min to remove the oxide layer.

[0017] In one or more embodiments of the present invention, the electrochemical deposition in step (3) employs constant current deposition with a current density of 5-20 mA / cm². 2 The electroplating time is 30-90 minutes.

[0018] In one or more embodiments of the present invention, the bifunctional electrode resisting iron adsorption in the alkaline electrolytic cell is prepared by the aforementioned preparation method.

[0019] In one or more embodiments of the present invention, the electrode surface includes a polysulfide protective layer, wherein the polysulfide in the protective layer includes S2. 2- S3 2- S4 2- At least one of them.

[0020] At a current density of 5000 A / m², the electrode exhibits a hydrogen evolution overpotential ≤230 mV and an oxygen evolution overpotential ≤309 mV. The electrode is in an Fe-containing environment... 2+ / Fe 3+ After running in an alkaline electrolyte for 2000 hours, the iron adsorption amount is ≤0.5wt%.

[0021] In one or more embodiments of the present invention, the bifunctional electrode is used in the electrolysis of water in an alkaline electrolyzer to produce hydrogen.

[0022] Compared with the prior art, the preparation method, electrode and application of the bifunctional electrode of the present invention prepares NiS alloy by optimizing the electroplating co-deposition process, and utilizes the dual anti-iron mechanism of the polysulfide protective layer to achieve a balance between high electrochemical activity and anti-iron adsorption performance, thereby reducing the energy consumption of the electrolytic cell and extending its service life. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is an LSV curve of an electrode in one embodiment of the present invention;

[0025] Figure 2 This is a graph showing electrode stability data in one embodiment of the present invention;

[0026] Figure 3 In one embodiment of the present invention, the electrode is at 5000 A / m 2 SEM images after 2000 hours of operation under electrical pressure, with the left image showing the cathode and the right image showing the anode. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments disclosed herein. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0028] The bifunctional electrode of the present invention has the dual functions of "high electrochemical activity + anti-iron adsorption", and its mechanism is as follows: Hydrogen evolution and oxygen evolution activity: NiS alloy itself has excellent HER / OER catalytic activity. Through electroplating co-deposition process, the coating is firmly bonded to the nickel wire mesh substrate, and the electron transport efficiency is high, ensuring efficient water electrolysis reaction under low overpotential.

[0029] Anti-iron adsorption mechanism: Under strongly alkaline electrolyte and cathode potential, sulfur species (S2) on the NiS electrode surface... 2- S 2- A dynamic equilibrium is reached, forming soluble polysulfides (S2). 2- S3 2- S4 2- ⁻) Protective layer: ① Chemical shielding effect: Polysulfide ions (S x 2- It has strong coordination and reducing capabilities, and interacts with Fe that migrates to the electrode surface. 2+ / Fe 3+ ① The preferential reaction produces iron sulfide precipitate, preventing iron ions from depositing on the cathode surface; ② Electrostatic repulsion effect: The polysulfide layer gives the electrode interface a negative charge, which is conducive to the deposition of positively charged Fe... 2+ / Fe 3+ An electrostatic repulsive force is generated, which inhibits its migration to the electrode surface through the diffusion layer.

[0030] Electroplating solution preparation

[0031] The electroplating solution uses deionized water as a solvent and contains four core solutes: nickel sulfate (Ni... 2+ Source, 50-150 g / L), ammonium sulfate (buffer, 10-50 g / L), ammonium chloride (conductive salt, 10-100 g / L), sodium thiosulfate (S 2- Source (100-200 g / L). During preparation, first place 1 L of deionized water in a beaker, then add the above solutes sequentially and stir until completely dissolved. Adjust the pH to 4.5-5.5 using hydrochloric acid or sodium hydroxide to ensure the stable presence of each component and uniform coating during deposition.

[0032] Electrode pretreatment

[0033] A 46-mesh nickel wire mesh with a diameter of 0.25 mm and double-sided sandblasted finish was selected as the cathode substrate (to ensure electrode conductivity and mechanical strength), and a nickel-based stretched mesh (0.3-0.5 mm diameter) was used as the anode. Cathode pretreatment steps: ① Soak in a surfactant (such as sodium dodecyl sulfate solution) and ultrasonically clean for 15 minutes to remove surface oil; ② Immerse in 3M hydrochloric acid for 10 minutes to remove the surface oxide layer; ③ Rinse with deionized water until neutral, and set aside.

[0034] Electrochemical deposition

[0035] The pretreated cathode and anode were placed parallel to each other in an electrolytic cell filled with electroplating solution, with the distance between the cathode and anode controlled at 25 cm. They were then connected to the negative and positive terminals of a DC power supply, respectively. At room temperature (25±5℃), a constant current deposition mode was used, with the current density controlled at 5-20 mA / cm², and the electroplating time at 30-90 min. After deposition, the electrodes were removed, rinsed with deionized water, and allowed to air dry to obtain a NiS alloy bifunctional electrode.

[0036] To achieve the above objectives, the method for preparing the bifunctional electrode of the present invention may specifically include the following steps:

[0037] A 46-mesh nickel wire mesh with a diameter of 0.25 mm and double-sided sandblasting was used as the cathode, and a nickel-based stretched mesh was used as the anode. The cathode was cleaned and degreased in a surfactant.

[0038] The degreased cathode was immersed in 3 M hydrochloric acid for about 10 minutes to remove the surface oxide layer.

[0039] The pretreated cathode is then placed in an electrolytic cell filled with electroplating solution, with the anode and cathode connected to the negative and positive terminals of a power supply, respectively, and electrochemical deposition is performed at room temperature. Preferably, electrochemical deposition is performed using constant current deposition with a current density of 5-20 mA / cm². 2 The electroplating time is 30-90 minutes.

[0040] The specific steps for preparing the electroplating solution are as follows: Take 1 L of deionized water into a beaker, add appropriate amounts of nickel sulfate, ammonium sulfate, ammonium chloride and sodium thiosulfate in sequence and stir evenly. After the solution is evenly mixed, measure the pH value of the electroplating solution and adjust the pH value to between 4.5 and 5.5.

[0041] Example 1

[0042] In this embodiment:

[0043] Electroplating solution preparation: Take 1L of deionized water, add 100g of nickel sulfate, 30g of ammonium sulfate, 50g of ammonium chloride, and 150g of sodium thiosulfate. Stir to dissolve, and then adjust the pH value to 5.0 with hydrochloric acid.

[0044] Electrode pretreatment: Take a 46-mesh nickel wire mesh with a diameter of 0.25 mm as the cathode, put it into a 5 g / L sodium dodecyl sulfate solution and ultrasonically remove oil for 15 min. After taking it out, immerse it in 3M hydrochloric acid for 10 min, and rinse it with deionized water until neutral.

[0045] Electrochemical deposition: Using a nickel-based stretched mesh (0.4 mm diameter) as the anode and anode spacing of 3 cm, a constant current of 10 mA / cm² was applied at room temperature for 60 min. After deposition, the electrode was removed, rinsed and dried to obtain a bifunctional electrode.

[0046] Performance testing

[0047] Electrochemical performance: LSV curves were tested using a three-electrode system in 1M KOH electrolyte, achieving 5000 A / m 2 Under electrical pressure, the HER overpotential is 230mV, and the OER overpotential is 309mV (e.g. Figure 1 );

[0048] Stability testing: The electrodes were assembled in a commercial alkaline electrolytic cell and operated continuously for 2000 hours at an electrical density of 5000 A / m². The cell voltage stabilized at 1.75-1.78V (e.g., ...). Figure 2 );

[0049] Anti-iron adsorption performance: After operation, SEM observation of the electrode surface showed no shedding or impurity adsorption (e.g. Figure 3 EDS analysis showed that the iron content was only 0.5 wt% (as shown in Table 1).

[0050] Table 1. EDS data after cathode packing in Example 1

[0051]

[0052] Example 2

[0053] In this embodiment:

[0054] 1. Electroplating solution preparation: Take 1L of deionized water, add 50g of nickel sulfate, 10g of ammonium sulfate, 10g of ammonium chloride, and 100g of sodium thiosulfate. Stir to dissolve, and then adjust the pH value to 4.5 with sodium hydroxide.

[0055] 2. Electrode pretreatment: Take a 46-mesh nickel wire mesh with a diameter of 0.25 mm as the cathode, immerse it in a 5 g / L sodium dodecyl sulfate solution for ultrasonic degreasing for 15 min, remove it and immerse it in 3 M hydrochloric acid for 10 min, and rinse it with deionized water until neutral.

[0056] 3. Electrochemical deposition: Using a nickel-based stretched mesh (0.3 mm diameter) as the anode, with a cathode-cathode spacing of 2 cm, a constant current of 5 mA / cm² was applied at room temperature for 30 min of deposition. After removal, the electrode was rinsed and dried to obtain a bifunctional electrode.

[0057] Table 2 EDS data after cathode packing in Example 2

[0058]

[0059] Example 3

[0060] In this embodiment:

[0061] 1. Electroplating solution preparation: Take 1L of deionized water, add 150g of nickel sulfate, 50g of ammonium sulfate, 100g of ammonium chloride, and 200g of sodium thiosulfate. Stir to dissolve, and then adjust the pH value to 5.5 with hydrochloric acid.

[0062] 2. Electrode pretreatment: Take a 46-mesh nickel wire mesh with a diameter of 0.25 mm as the cathode, immerse it in a 5 g / L sodium dodecyl sulfate solution for ultrasonic degreasing for 15 min, remove it and immerse it in 3 M hydrochloric acid for 10 min, and rinse it with deionized water until neutral.

[0063] 3. Electrochemical deposition: Using a nickel-based stretched mesh (0.5 mm diameter) as the anode and anode spacing of 5 cm, a constant current of 20 mA / cm² was applied at room temperature for 90 min. After deposition, the electrode was removed, rinsed and dried to obtain a bifunctional electrode.

[0064] Table 3. EDS data after cathode packing in Example 3

[0065]

[0066] The beneficial effects of the present invention include, but are not limited to:

[0067] The bifunctional electrode for resisting iron adsorption in the alkaline electrolyzer of this invention, obtained through a simple one-step electrodeposition method, yields highly active hydrogen evolution and oxygen evolution electrodes, which can be used in commercial electrolyzers at 5000 A / m 2 Under electrical density conditions, the overpotential of HER is only 230 mV, and the overpotential of OER is only 309 mV. The electrochemical performance is as follows: Figure 1 Furthermore, the raw materials are readily available and inexpensive, making them suitable for commercial applications.

[0068] The Ni-S electrode of this invention utilizes the "chemical shielding" effect of surface polysulfides to inhibit the formation of sulfur species (such as S2) on the surface of the nickel-sulfur electrode under strongly alkaline electrolyte and cathode potential. 2- S 2- It is not stable and will be further reduced or dynamically balanced with sulfur species in the system to form a layer of soluble polysulfides (such as S2). 2- S3 2- S4 2- These polysulfides dissolve and adsorb near the electrode surface, forming a "protective layer." They preferentially react with iron ions, and the polysulfide ions (S...x 2- It has very strong coordination and reducing abilities. When iron ions (Fe) 2+ / Fe 3+ When attempting to approach the electrode surface, the positively charged iron ions preferentially react with the polysulfide protective layer, forming iron sulfide precipitate. Secondly, the polysulfide layer on and near the nickel-sulfur electrode surface may cause the interface to exhibit a more negative charge characteristic than pure nickel. Positively charged iron ions approaching this negatively charged surface experience stronger electrostatic repulsion, making it difficult for them to break through the diffusion layer, thus further inhibiting their migration and adsorption to the electrode surface. This unique self-protection mechanism gives it extremely high stability and long lifespan in industrial electrolysis environments containing impurity ions. Electrolytic cell stacking performance is as follows... Figure 2 At 5000A / m 2 Stable operation for 2000 hours under electrical density, with a cell voltage of only 1.75-1.78V and energy consumption of only 4.18-4.25 kWh / Nm³. 3 The microstructure of the electrode stack is as follows Figure 3 As can be seen, there are no defects such as shedding or adsorption of impurities on the electrode surface. The elemental composition of the Ni-S electrode after stacking is shown in Table 1, indicating that only 0.5 wt% of iron exists on the electrode surface, which shows that the electrode has excellent resistance to iron ion adsorption.

[0069] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0070] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a bifunctional electrode resistant to iron adsorption in an alkaline electrolytic cell, characterized in that, Includes the following steps: (1) Preparation of electroplating solution: Using deionized water as solvent, add nickel sulfate, ammonium sulfate, ammonium chloride and sodium thiosulfate in sequence, stir evenly and adjust the pH value to 4.5-5.5; (2) Electrode pretreatment: A double-sided sandblasted nickel wire mesh is used as the cathode, and then the oil and oxide layer are removed in sequence; (3) Electrochemical deposition: The pretreated cathode and nickel-based stretched mesh anode are placed in the electroplating solution, and the cathode and anode are connected to the negative and positive terminals of the power supply, respectively. The electroplating is carried out at room temperature with an input current of 5-20 mA / cm. 2 A bifunctional electrode is obtained by constant current deposition at a current density of 30-90 min.

2. The preparation method according to claim 1, characterized in that, The electroplating solution in step (1) includes deionized water as a solvent, wherein: the concentration of nickel sulfate is 50-150 g / L, the concentration of ammonium sulfate is 10-50 g / L, the concentration of ammonium chloride is 10-100 g / L, and the concentration of sodium thiosulfate is 100-200 g / L.

3. The preparation method according to claim 2, characterized in that, The pH value mentioned in step (1) is adjusted by hydrochloric acid or sodium hydroxide.

4. The preparation method according to claim 1, characterized in that, The wire diameter of the nickel-based stretched mesh anode in step (3) is 0.3-0.5 mm.

5. The preparation method according to claim 1, characterized in that, The electrode pretreatment in step (3) is as follows: a 46-mesh nickel wire mesh with a diameter of 0.25 mm and double-sided sandblasting is used as the cathode, and then the electrode is degreased by surfactant and soaked in 3M hydrochloric acid for 10 min to remove the oxide layer.

6. The preparation method according to claim 1, characterized in that, In step (3), electrochemical deposition is performed using constant current deposition with a current density of 5-20 mA / cm². 2 The electroplating time is 30-90 minutes.

7. A bifunctional electrode for resisting iron adsorption in an alkaline electrolytic cell, characterized in that, It is prepared by any one of the preparation methods described in claims 1-6.

8. The bifunctional electrode for resisting iron adsorption in an alkaline electrolytic cell according to claim 7, characterized in that, The electrode surface includes a polysulfide protective layer, wherein the polysulfides in the protective layer include S2. 2- S3 2- S4 2- At least one of them.

9. The application of the bifunctional electrode according to any one of claims 7-8 in the electrolysis of water to produce hydrogen in an alkaline electrolyzer.

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