Integrated electrode for alkaline electrolytic cell, method for preparing electrode, and electrolytic cell

Abstract

The present invention relates to an integrated electrode for an alkaline electrolytic cell, a method for preparing the electrode, and the electrolytic cell. The preparation method comprises the following steps: A) sequentially arranging a nickel felt, a nickel mesh electrode, and a nickel mesh flow field, and integrating them using laser welding technology; B) in a two-electrode system, using an aqueous solution of a nickel-iron metal salt as an electroplating solution, the integrated electrode welded in step A) as a working electrode, and a platinum sheet as a counter electrode, and electrodepositing a layer of nickel-iron hydroxide on the surface of the welded integrated electrode to obtain an integrated electrode for an alkaline electrolytic cell. Compared with existing technologies, the integrated process of the present invention, including laser welding and catalyst-based electrodeposition, has good industrialization prospects and can be manufactured through automated processing. The use of this electrode can optimize the electrolytic cell assembly structure, reduce its size while maintaining high electrode reaction activity, and achieve good economic benefits and high practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic hydrogen production, and in particular to an integrated electrode for an alkaline electrolytic cell, a method for preparing the electrode, and the electrolytic cell. Background Art

[0002] As an excellent energy carrier, hydrogen will play a vital role in the future world energy system. The advantage of hydrogen lies in its theoretical combustion product, which is only water. This means that it does not produce environmentally harmful substances such as carbon monoxide and carbon dioxide, nor does it produce acid rain, ozone depletion, or harmful emissions. Therefore, hydrogen is a clean fuel. Furthermore, hydrogen energy can be produced using renewable energy sources (such as wind, solar, and hydropower), making it a key focus in the current energy sector.

[0003] Large-scale promotion of hydrogen requires large-scale hydrogen production, and the production of clean hydrogen is generally achieved through water electrolysis. Alkaline electrolysis is the most widely used water electrolysis technology. It is also called alkaline aqueous solution electrolysis hydrogen production technology. It uses strong base as electrolyte and porous diaphragm as characteristic. This technology is the earliest discovered and applied water electrolysis technology, and it has been industrially applied for more than 100 years. However, in traditional alkaline water electrolyzers, there is a distance between the electrode and the diaphragm. During the electrolysis process, the hydrogen and oxygen generated on the electrode will exist in the form of bubbles and accumulate in this distance. The accumulation of bubbles may cause the active sites on the electrode surface to be covered and the actual resistance of the electrolyte to increase, which in turn manifests as a decrease in the performance of the electrolyzer.

[0004] Therefore, the concept of a "zero-gap electrolyzer" has been proposed. In this electrolyzer, due to the compression of the elastic element, the cathode and anode are assembled tightly against the diaphragm. This design can reduce the resistance of the electrolyzer and significantly improve efficiency. However, the electrode structure of the current industrial electrolyzer is rough, the mechanical properties of the diaphragm are poor, and mutual contact and extrusion can easily cause the diaphragm to rupture and lead to a short circuit, which is a high risk. At present, the relevant patents for zero-gap electrolyzers are mainly concentrated in chlor-alkali electrolyzers. Chinese invention CN201980038703.4 discloses a zero-gap electrolyzer with an elastic retaining element, in which the anode, ion exchange membrane and cathode are in direct contact, and a flexible elastic retaining element is arranged on the other side of the anode and / or cathode. This patent is mainly aimed at chlor-alkali electrolysis or hydrochloric acid electrolysis. The device uses a retaining element to press the electrode and the ion exchange membrane together. The annular retaining element prevents lateral displacement of the diaphragm by controlling the direction of the compression force. However, current research has not yet paid attention to the risk of diaphragm damage caused by internal extrusion between the diaphragm and the electrode.

[0005] Therefore, in order to solve the problems existing in the assembly of electrodes and diaphragms in existing electrolytic cells, it is urgent to design a new zero-gap main plate-electrode-diaphragm design that can optimize the assembly structure of the electrolytic cell while maintaining high electrode reaction activity. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide an integrated electrode for an alkaline electrolytic cell. By using this electrode, the electrolytic cell assembly structure can be optimized, the size can be reduced while maintaining high electrode reaction activity, the economic benefits are good, and the practical value is high.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A first aspect of the present invention provides a method for preparing an integrated electrode for an alkaline electrolytic cell, comprising the following steps:

[0009] A) Arranging the nickel felt, nickel mesh electrode, and nickel mesh flow field in sequence and integrating them into one piece using laser welding technology;

[0010] B) In a two-electrode system, an aqueous solution of nickel-iron metal salt is used as the electroplating solution, the integrated electrode welded in step A) is used as the working electrode, and the platinum sheet is used as the counter electrode. A nickel-iron hydroxide deposition layer is electrodeposited on the surface of the welded integrated electrode to obtain an integrated electrode for an alkaline electrolytic cell.

[0011] Furthermore, the thickness of the nickel felt is 0.5-2 mm;

[0012] The nickel wire diameter of the nickel mesh electrode is 20-2000 μm, and the mesh number of the nickel mesh electrode is 50-600 meshes.

[0013] Furthermore, the nickel wire diameter of the nickel mesh flow field is 20-2000um, and the mesh number of the nickel mesh flow field is 50-600 mesh.

[0014] Furthermore, the nickel felt, nickel mesh electrode, and nickel mesh flow field are all pretreated materials, and the pretreatment process is: ultrasonic treatment in dilute hydrochloric acid to remove surface oxides, then ultrasonic treatment in anhydrous ethanol to remove surface hydrochloric acid and organic matter, and finally ultrasonic treatment in deionized water to remove other residual impurities on the surface.

[0015] Furthermore, the concentration of the dilute hydrochloric acid is 0.5-1.2 mol / L, and the ultrasonic treatment time is 15 minutes.

[0016] Furthermore, in the electroplating solution in step B), the concentration of nickel chloride is 0.8-1.2 mol / L, and the concentration of ferrous chloride is 0.4-0.6 mol / L.

[0017] Furthermore, in step B), the electrodeposition is carried out in a deposition tank, the electrodeposition time is 10 minutes, and the current density is uniformly increased from 1A / cm 2 Increased to 3A / cm 2 , the temperature is 20-30℃.

[0018] Furthermore, in step B), after the electrodeposition, the process further comprises: washing and drying, specifically comprising: rinsing the electrodeposited composite material with deionized water, then with anhydrous ethanol, and then naturally drying.

[0019] A second aspect of the present invention provides an integrated electrode prepared by the above method, comprising:

[0020] Nickel felt: It is placed between the electrode and the diaphragm, acting as a buffer on the material to prevent the diaphragm from being damaged by impact or friction, and promoting electrolysis efficiency through the high specific surface area of ​​nickel felt;

[0021] Nickel mesh electrode: electrolyzes water and produces oxygen or hydrogen on the electrode surface;

[0022] Nickel mesh flow field: promotes the electrolytic reaction and forms the flow field area of ​​the electrolytic chamber with the main electrode plate on the other side.

[0023] It also includes a nickel-iron hydroxide deposition layer composited on the surface of the integrated electrode.

[0024] A third aspect of the present invention provides an electrolytic cell comprising the integrated electrode as described above.

[0025] Compared with the prior art, the present invention has the following technical advantages:

[0026] (1) Compact structure. The present invention uses laser welding technology to integrate nickel felt, nickel mesh electrode, and nickel mesh flow field to obtain an integrated electrode of "nickel felt-nickel mesh electrode-nickel mesh flow field" with a zero-gap structure, which greatly reduces the ohmic impedance of the electrode. In addition, this zero-gap electrode also provides a basis for the subsequent manufacture of a zero-gap alkaline water hydrogen production electrolyzer.

[0027] (2) High catalytic activity. In the integrated electrode of the present invention, the nickel felt, nickel mesh electrode, nickel mesh flow field and other structures all have a large reaction surface area. The nickel iron hydroxide deposition layer uniformly covering the surface of the integrated electrode has good alkaline water electrolysis catalytic activity, thereby enabling the entire electrode to achieve high water electrolysis catalytic performance.

[0028] (3) Overall, the integrated electrode for alkaline electrolysis cell proposed in the present invention is very suitable for industrial water electrolysis. Whether in terms of ease of preparation, economy, catalytic performance, or structural characteristics, it is far superior to the existing alkaline electrolysis cell electrode preparation technology for use in industrial water electrolysis, greatly improving the economic benefits of industrial water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the integrated electrode in the present invention;

[0030] Figure 2 Schematic diagram of the overall structure of the electrolytic cell equipment in an embodiment of the present invention.

[0031] In the figure, 1 is nickel felt, 2 is electrode, 3 is nickel mesh flow field, 4 is diaphragm, 5 is anode terminal, 6 is oxygen outlet, 7 is anode side nickel felt, 8 is anode electrode, 9 is anode side nickel mesh plate, 10 is elastic element, 11 is liquid outlet, 12 is liquid inlet, 13 is tank body, 14 is cathode side nickel mesh plate, 15 is cathode electrode, 16 is cathode side nickel felt, 17 is hydrogen outlet, and 18 is cathode terminal. DETAILED DESCRIPTION

[0032] The present invention is characterized by combining nickel felt, electrodes, and a nickel mesh flow field into an integrated electrode. The invention aims to overcome the problem of excessive distance between the electrode and the diaphragm in conventional alkaline water electrolyzers, which leads to accumulation of bubbles and consequently reduced electrolytic cell performance. Furthermore, due to the rough electrode structure and poor mechanical properties of the diaphragm in industrial electrolyzers, the electrodes and diaphragm contact and squeeze each other during zero-gap assembly, leading to diaphragm rupture and short circuits.

[0033] In the present invention, in the laser-welded integrated electrode of "nickel felt-nickel mesh electrode-nickel mesh flow field" obtained by laser welding, when subjected to external forces such as the compression force of an elastic element, the soft structure of the internal nickel felt can evenly distribute the force to the diaphragm, thereby avoiding strong impacts on the diaphragm and preventing damage to the diaphragm. At the same time, the nickel felt also avoids direct contact between the electrode and the diaphragm, prevents friction between the rough electrode surface and the diaphragm, and reduces the possibility of diaphragm tearing. In addition, in actual work, the thinner thickness of the nickel felt itself does not destroy the zero-gap configuration, and the high specific surface area of ​​the nickel felt itself will further promote the electrolysis reaction, thereby achieving zero-gap assembly without causing diaphragm rupture. Therefore, it can effectively alleviate the problem of the accumulation of bubbles caused by the distance between the electrode and the diaphragm in traditional alkaline water electrolytic cells, which in turn leads to a decrease in the performance of the electrolytic cell. In addition, integrated welding reduces the ohmic internal resistance of the electrode.

[0034] Electroplating uniformly deposits an ultrathin nickel-iron hydroxide layer on the surface of the integrated electrode. This ultrathin layer not only does not affect electron transport and electrode assembly, but also exhibits excellent catalytic activity for water electrolysis. Therefore, the present invention provides an integrated electrode for an alkaline electrolytic cell, which has an integrated structure, low ohmic impedance, and good catalytic activity.

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0036] In order to further illustrate the present invention, the integrated electrode for alkaline electrolytic cell provided by the present invention, its preparation method and application are described in detail below with reference to the examples, but it should not be understood as limiting the scope of protection of the present invention.

[0037] The method for preparing an integrated electrode for an alkaline electrolytic cell in this embodiment comprises the following steps:

[0038] A) Arranging the nickel felt, nickel mesh electrode, and nickel mesh flow field in sequence and integrating them into one piece using laser welding technology;

[0039] B) In a two-electrode system, a nickel-iron metal salt electroplating solution is used, the integrated electrode welded in step A) is used as a working electrode, and the platinum sheet is used as a counter electrode, and a nickel-iron hydroxide deposition layer is electrodeposited on the surface of the welded integrated electrode, thereby obtaining an integrated electrode for an alkaline electrolytic cell.

[0040] In this embodiment, the nickel felt in step A) is pretreated nickel felt, and the thickness of the nickel felt is 0.5 mm.

[0041] In this embodiment, the nickel mesh electrode in step A) is a pretreated nickel mesh electrode; the nickel wire diameter of the nickel mesh electrode is 200 μm, and the mesh size of the nickel mesh electrode is 100 meshes.

[0042] The above specific parameters can be adjusted appropriately based on the specific implementation process.

[0043] In certain embodiments of the present invention, the nickel mesh is a pretreated nickel mesh. The pretreated nickel mesh is prepared according to the following method:

[0044] The nickel mesh was ultrasonically treated in dilute hydrochloric acid to remove surface oxides, then ultrasonically treated in anhydrous ethanol to remove surface hydrochloric acid and organic matter, and finally ultrasonically treated in deionized water to remove other residual impurities on the surface.

[0045] In certain embodiments of the present invention, the concentration of the dilute hydrochloric acid is 0.5 to 1.2 mol / L, specifically 1 mol / L. The optimal temperature and duration of the ultrasonic treatment are 15 minutes. The nickel felt, nickel mesh electrode, and nickel mesh flow field are ultrasonically treated in dilute hydrochloric acid, then in anhydrous ethanol, and finally in deionized water, followed by natural drying.

[0046] In this embodiment, in the nickel-iron metal salt electroplating solution in step B), the concentration of nickel chloride is 0.8-1.2 mol / L, and the concentration of ferrous chloride is 0.4-0.6 mol / L.

[0047] In this embodiment, the electrodeposition in step B) is carried out in a deposition tank. The electrodeposition time is 10 minutes, and the current density is uniformly increased from 1A / cm 2 Increased to 3A / cm 2 , the temperature is 20-30°C; specifically, the optimal temperature during implementation can be 25°C.

[0048] In this embodiment, after the electrodeposition in step B), washing and drying are further performed. Specifically, the electrodeposited composite material is rinsed with deionized water, then rinsed with anhydrous ethanol, and then naturally dried. The number of rinses may be 3 to 5, specifically 3. Each rinse lasts 10 to 30 seconds, specifically 20 seconds. The rinse flow rate should be gentle so as not to damage the electrodeposited structure.

[0049] The functions of the main components in the integrated electrode of the present invention are as follows:

[0050] Nickel felt: It is placed between the electrode and the diaphragm to act as a buffer to prevent the diaphragm from being damaged by impact or friction. At the same time, the high specific surface area of ​​nickel felt promotes electrolysis efficiency.

[0051] Electrode: The electrode where redox reactions occur in electrolysis, electrolyzing water and producing oxygen or hydrogen on the electrode surface.

[0052] Nickel mesh flow field: a part of the main electrode plate. Its high specific surface area can promote the electrolysis reaction. At the same time, it forms the flow field area of ​​the electrolysis chamber with the main electrode plate on the other side.

[0053] Figure 2This is an illustrative schematic diagram for the first embodiment of the present invention, showing a cross-sectional view of an alkaline water electrolysis cell using an integrated electrode. When using the electrolytic cell for electrolysis, potassium hydroxide or sodium hydroxide with a mass fraction of 25%-35% is used as the electrolyte. The electrolyte enters the electrolytic cell body 13 through the liquid inlet 12 and leaves the cell body 13 through the liquid outlet 11. The external power supply inputs current to the anode electrode 8 through the anode terminal 5, and then passes through the electrolyte, the anode side nickel felt 7, the diaphragm 3, the cathode side nickel felt 16 and the cathode electrode 15, and then outputs through the cathode terminal 18 to carry out the electrolysis process. The hydrogen generated during the electrolysis process is discharged through the hydrogen channel 17, and the oxygen generated is discharged through the oxygen channel 6.

[0054] like Figure 2 As shown, the electrolytic cell device designed in the present invention includes an end shell plate, an anode-side nickel mesh 9, a cathode-side nickel mesh 14, an anode electrode 8, a cathode electrode 15, a nickel felt 1, and a diaphragm 4. The diaphragm 4 is disposed between the anode electrode 8 and the cathode electrode 15. The nickel felt 1 is disposed between the anode electrode 8 / cathode electrode 15 and the diaphragm 4, forming an integrated electrode with the anode electrode 8 / cathode electrode 15 and the anode-side nickel mesh 9 / cathode-side nickel mesh 15, respectively. The end shell plate includes an anode end shell plate and a cathode end shell plate, which are integrated at both ends of the cell body 13. Elastic retaining elements 10 are disposed between the cathode end shell plate and the cathode electrode, and between the anode end shell plate and the anode electrode. The elastic retaining element 10 acts as a coil spring. On the one hand, it is fixed to the end shell plate and tightened to the cell body 13. On the other hand, it applies axial pressure to the anode electrode 2 / cathode electrode 4 in the direction toward the anode electrode 2 / cathode electrode 4, that is, it extends in a direction perpendicular to the electrodes. During the specific installation, the nickel felt 1 is preferentially welded with the anode electrode 8 / cathode electrode 15 and the anode side nickel mesh 9 / cathode side nickel mesh 15 to form an integrated anode / cathode electrode, and then assembled in sequence according to the cathode end shell plate, integrated cathode electrode, diaphragm 4, integrated anode electrode and anode end shell plate, and finally integrated on the tank body 13.

[0055] The above-mentioned electrolytic cell is characterized in that, during specific implementation, the elastic element 10 fixed to the cell body 13 presses the integrated anode electrode, the diaphragm 3, and the integrated cathode electrode together to form a zero-gap configuration. In the integrated electrode, a layer of smooth nickel felt is provided near one side of the diaphragm, and the electrolytic cell can effectively accommodate the diaphragm between the nickel felts on both sides to improve the working stability of the diaphragm. During actual installation, the nickel felt is provided with a size slightly larger than the size of the diaphragm to ensure the ease of installation of the diaphragm and the complete accommodation of the diaphragm by the nickel felt. Therefore, the diaphragm is accommodated in the nickel felt without being exposed and is not subject to local impact and friction. When subjected to external force such as the compression force of the elastic element, the soft structure inside the nickel felt can evenly distribute the force to the diaphragm, thereby avoiding strong impact on the diaphragm and preventing damage to the diaphragm. Due to the use of a nickel felt that is slightly larger than the size of the diaphragm, the electrode will not be able to directly contact the surface of the diaphragm, and the rough electrode surface will only contact the buffer structure. In practice, by setting the nickel felt thickness to ≤ 0.5mm, the thinner thickness does not disrupt the zero-gap configuration of the electrolyzer. The high specific surface area of ​​the nickel felt further promotes the electrolysis reaction. Furthermore, the nickel-iron hydroxide deposit on the surface of the integrated electrode effectively catalyzes the reaction, improving hydrogen production efficiency.

[0056] In the alkaline water electrolyzer used in the second embodiment, the tank body 13 is a square sheet metal structure. A hydrogen channel 17 and an oxygen channel 6 are provided on the left and right sides of the upper portion of the tank body 13, respectively. A cathode terminal 18 and an anode terminal 5 are mounted on the left and right sides of the center portion of the tank body exterior. Insulating sleeves are provided on the outside of the terminal 5. Both sets of terminal 5s extend through the tank body 13 and are connected to a pulse voltage generator at their tops via wires. A liquid inlet 12 is provided at the lower portion of the outer left side of the tank body, and a liquid outlet 11 is provided at the lower portion of the outer right side of the tank body. The tops of the cathode terminal 18 and the anode terminal 5 can be connected to the pulse voltage generator via wires. The liquid inlet 12 can be connected to a water pump and an electrolyte storage tank, with potassium hydroxide or sodium hydroxide solution being the input electrolyte. The liquid outlet 11 can be connected to a waste liquid collection tank. The hydrogen channel 17 and the oxygen channel 6 can be further connected to devices such as gas purification and drying.

[0057] In the alkaline water electrolysis cell used in the second embodiment, the cathode 15 / anode 8 is composed of a conductive electrode material, and a nickel composite electrode such as nickel-plated iron plate and nickel alloy is used; the diaphragm 4 can be a variety of diaphragm types such as polysulfone, polyether, PTFE, PPS and composite inorganic diaphragm; the elastic retaining element 10 is an elastic corrugated mesh woven from fine-woven nickel wire; the nickel felt is paved with nickel wire fibers, with a thickness of ≤0.5mm, the wire diameter is related to the specific selected pore size, the overall porosity is between 50%-90%, and the surface is smooth and burr-free. At the same time, any existing commercially available model of nickel felt that meets the above requirements can be used in this embodiment; the nickel mesh flow field can be existing commercially available nickel mesh such as nickel wire woven mesh, nickel plate (or nickel foil) stretched mesh, nickel foil punched mesh and nickel wire knitted mesh.

[0058] In specific implementation, the integrated electrode designed in the present invention can also be used in a pressurized system.

[0059] In specific implementation, the integrated electrode designed in the present invention can be used not only in a single-stage electrolytic cell, but also in a multi-stage electrolytic cell.

[0060] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. 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 preparing an integrated electrode for an alkaline electrolytic cell, characterized in that: The following steps are involved: A) Arrange the nickel felt, nickel mesh electrode, and nickel mesh flow field in sequence and integrate them into one piece using laser welding technology; B) In a two-electrode system, an aqueous solution of a nickel-iron metal salt is used as an electroplating solution, the integrated electrode welded in step A) is used as a working electrode, and a platinum sheet is used as a counter electrode, and a nickel-iron hydroxide deposition layer is electrodeposited on the surface of the welded integrated electrode to obtain an integrated electrode for an alkaline electrolytic cell; In the electroplating solution in step B), the concentration of nickel chloride is 0.8-1.2 mol / L, and the concentration of ferrous chloride is 0.4-0.6 mol / L; In step B), the electrodeposition is carried out in a deposition tank for 10 minutes, and the current density is uniformly increased from 1A / cm 2 Increased to 3A / cm 2 , the temperature is 20~30℃.

2. The method for preparing an integrated electrode for an alkaline electrolytic cell according to claim 1, wherein: The thickness of the nickel felt is 0.5-2 mm; The nickel wire diameter of the nickel mesh electrode is 20-2000 μm, and the mesh number of the nickel mesh electrode is 50-600 meshes.

3. The method for preparing an integrated electrode for an alkaline electrolytic cell according to claim 1, wherein: The nickel wire diameter of the nickel mesh flow field is 20-2000 μm, and the mesh number of the nickel mesh flow field is 50-600 mesh.

4. The method for preparing an integrated electrode for an alkaline electrolytic cell according to claim 1, wherein: The nickel felt, nickel mesh electrode, and nickel mesh flow field are all pretreated materials. The pretreatment process is: ultrasonic treatment in dilute hydrochloric acid to remove surface oxides, then ultrasonic treatment in anhydrous ethanol to remove surface hydrochloric acid and organic matter, and finally ultrasonic treatment in deionized water to remove other residual impurities on the surface.

5. The method for preparing an integrated electrode for an alkaline electrolytic cell according to claim 4, wherein: The concentration of the dilute hydrochloric acid is 0.5-1.2 mol / L, and the ultrasonic treatment time is 15 min.

6. The method for preparing an integrated electrode for an alkaline electrolytic cell according to claim 1, wherein: In step B), after the electrodeposition, the process further comprises: washing and drying, specifically, rinsing the electrodeposited composite material with deionized water, then with anhydrous ethanol, and then drying naturally.

7. An integrated electrode prepared by the method according to any one of claims 1 to 6, characterized in that: Including sequential laser welding of: Nickel felt: It is placed between the electrode and the diaphragm, acting as a buffer on the material to prevent the diaphragm from being damaged by impact or friction, and promoting electrolysis efficiency through the high specific surface area of ​​nickel felt; Nickel mesh electrode: electrolyzes water and produces oxygen or hydrogen on the electrode surface; Nickel mesh flow field: promotes electrolytic reaction and forms the flow field area of ​​the electrolytic chamber with the main electrode plate on the other side; It also includes a nickel-iron hydroxide deposition layer composited on the surface of the integrated electrode.

8. An electrolytic cell, characterized in that: Comprising an integrated electrode as claimed in claim 7.

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