Alkaline water electrolytic bath end polar plate and electrolytic bath

Abstract

The utility model provides an alkaline water electrolyzer end polar plate and an electrolyzer, a transversely arranged elliptical polar plate frame is adopted, a planar polar plate and a spherical polar plate are integrated inside to form a cavity buffer structure, and a gas-liquid inlet and a gas-liquid outlet are respectively arranged at the left end and the right end of a cavity. The flow channel system comprises three stages of arc-shaped flow channels, a micro-channel array and spiral guide vanes, and gas-liquid uniform distribution is achieved through gradient type flow channels and turbulent flow induction. A nano-porous nickel layer is prepared on the surface of the polar plate by adopting a pulse electroplating process. The lead wire adopts a core layer-insulating layer-outer layer composite structure, and the tail end of a micro-channel is connected with a discharge port through a conical transition section, so that the fluid resistance is effectively reduced. Through the design, the electrolyte contact area is increased, the bubble separation speed is increased, the energy consumption is reduced, and the device is suitable for a large-scale alkaline electrolysis hydrogen production system.

Description

Technical Field

[0001] This utility model relates to the field of water electrolysis technology, specifically to an alkaline water electrolysis cell, and more particularly to the end plate structure of the water electrolysis cell. Background Technology

[0002] Hydrogen production through water electrolysis involves using direct current to decompose water molecules into hydrogen and oxygen through an electrochemical process, which are then released at the cathode and anode, respectively. Current methods for hydrogen production through water electrolysis include alkaline electrolysis (AWE), proton exchange (PEM), and solid oxide electrolysis (SOEC). Among these, alkaline water electrolysis is the most mature, has the lowest cost, and is the most economical.

[0003] Alkaline water electrolysis is typically carried out using electrolyzers. The end plates are key structural components of alkaline water electrolyzers, located at both ends of the stacked structure (anode and cathode sides). Pressure is applied via bolts or hydraulic devices to ensure tight contact between the internal components such as the plates, electrodes, and diaphragms, maintaining airtightness and electrical contact stability. However, traditional end plates, such as those in the utility model patent CN221275907U, often employ circular or square structures. During operation, these structures can lead to uneven electrolyte flow, excessive alkali pressure drop, and flow field imbalance, resulting in decreased hydrogen production efficiency and increased energy consumption. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an alkaline water electrolysis cell end plate structure, solving at least one of the multiple technical problems faced by end plates in the background art.

[0005] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0006] An alkaline water electrolyzer end plate includes an elliptical electrode frame with its major axis arranged laterally and its minor axis arranged vertically. A planar electrode plate is sealed inside the elliptical electrode frame. A spherical electrode plate is covered on one side of the planar electrode plate. A cavity is provided between the planar electrode plate and the spherical electrode plate. The cavity has a gas-liquid inlet and a gas-liquid outlet that are respectively provided through the elliptical electrode frame along its major axis. An internal flow channel is provided inside the cavity along its major axis. A nanoporous nickel layer is provided on the inner side of the planar electrode plate and / or the spherical electrode plate. At least one lead wire is provided through the planar electrode plate and the spherical electrode plate through the elliptical electrode frame.

[0007] The spherical electrode plate is connected to the edge of the planar electrode plate. An internal flow channel or a pre-set connecting groove can be directly opened on the side where the two are close to each other. After the internal flow channel is manufactured separately, it is assembled into the cavity between the two electrode plates by means of clamping, bonding, welding and other methods.

[0008] Furthermore, the nanoporous nickel layer is formed by a pulse electroplating process that alternately applies a positive voltage of 2V / reverse voltage of 1.2V, with a nickel layer thickness of 30-50μm and a surface roughness Ra≤0.8μm.

[0009] Specifically, a bipolar pulse electroplating power supply can be used here. The forward voltage is set to 2.0V during the deposition stage, and the reverse voltage is set to 1.2V during the dissolution control stage. The pulse frequency is 50-100Hz, and the duty cycle is 60% forward and 40% reverse. The current density is set to 2-5A / dm³. 2 .

[0010] The electrolyte formulation includes, but is not limited to, the following components: nickel sulfate hexahydrate 250-300 g / L, nickel chloride hexahydrate 40-60 g / L, succinate 30-40 g / L, sodium saccharin 0.5-1 g / L, surfactant, such as sodium dodecyl sulfate 0.05-0.1 g / L, and the balance being water. The electrolyte pH is adjusted to 3.5-4.5 with nitric acid. After heating the electrolyte to 50-60℃ and achieving a conductivity of 18-22 mS / cm, a forward pulse of 10-15 ms and a reverse pulse of 5-8 ms are applied, with the cycle period depending on the coating thickness.

[0011] Furthermore, a CoFe-LDH nanosheet catalytic layer is disposed on the surface of the nanoporous nickel layer, and the CoFe-LDH nanosheet catalytic layer is grown in situ on the surface of the nanoporous nickel layer by a hydrothermal method.

[0012] Specifically, LDH refers to layered double hydroxide compound. After the nanoporous nickel layer is generated, the tubular part of the internal flow channel of the electrode plate or ball is immersed in a 1 mol / L hydrochloric acid solution, and the oxide layer is removed by etching and ultrasonication. Then the electrode plate is transferred to a reaction vessel containing a precursor solution and heated to 100°C for 12 hours. During the heating process, the pressure of the reaction vessel is maintained at 1.5-2.0 MPa.

[0013] Specifically, the precursor solution contains 14.6-29.1 g / L cobalt nitrate hexahydrate, 10.1-20.2 g / L ferric nitrate nonahydrate, 18.0-30.0 g / L urea, 0.37-1.11 g / L ammonium fluoride, and the balance is water.

[0014] Furthermore, the internal flow channels are distributed in at least three levels of arcs radially from the long axis to both ends of the short axis. The width of the internal flow channels decreases from the center to the edge. The internal flow channels are radially provided with a microchannel array. The microchannel array is filled along the fractal structure onto the inner surface of the planar electrode plate and / or the spherical electrode plate. The filling area of ​​the fractal structure is ≥ 50% of the area of ​​the planar electrode plate and / or the spherical electrode plate.

[0015] Specifically, the microchannel array uses Koch curve fractals with an iteration level of n=3 layers.

[0016] Furthermore, the lead wire adopts a composite structure, including a core layer, an insulation layer, and an outer layer arranged sequentially from the inside out.

[0017] Furthermore, the width of the microchannel array is ≤5mm, and the depth of the microchannel array decreases from the center of the cavity towards both ends of the short axis.

[0018] Furthermore, the internal flow channel is also provided with spiral guide vanes, the pitch of which is 3-5mm.

[0019] Furthermore, the end of the microchannel array is connected to the gas-liquid outlet via a conical transition section along the inner side of the elliptical electrode frame.

[0020] Furthermore, the ratio of the length of the major axis to the length of the minor axis of the elliptical electrode frame is 3:2.

[0021] This utility model also protects an alkaline water electrolyzer, which includes an end plate having at least one of the above-mentioned technical features.

[0022] The advantages and beneficial effects of this utility model are as follows:

[0023] 1. The elliptical electrode frame with its long axis arranged laterally in this utility model is adapted to the internal spatial distribution requirements of the electrolytic cell, reducing mechanical stress concentration, and optimizing the gas-liquid flow path through its asymmetrical structure. The combined sealing design of the planar electrode plate and the spherical electrode plate ensures the flatness of the electrode surface and forms a gas-liquid buffer zone through the cavity, avoiding sudden changes in local pressure.

[0024] 2. The internal flow channels employ a graded diffusion system along the long axis towards both ends of the short axis, combined with a decreasing channel width, to optimize the uniformity of gas-liquid distribution and reduce uneven electrolysis caused by edge effects. Microchannels with a width ≤5mm cover ≥50% of the electrode surface with a fractal structure, greatly increasing the contact area between the electrolyte and the catalyst layer. The decreasing depth matches the fluid pressure gradient, improving mass transfer efficiency. The helical structure with a pitch of 3-5mm induces turbulence in the fluid, enhancing gas-liquid mixing and bubble decoupling, and reducing concentration polarization.

[0025] 3. A nanoporous nickel layer with a thickness of 50-100 μm and Ra≤0.5 μm is formed by alternating forward and reverse pulse electroplating, which combines high specific surface area and mechanical stability. CoFe bimetallic hydroxide nanosheets are directly generated on the surface of the nanoporous nickel, achieving atomic-level interfacial bonding, significantly reducing hydrogen / oxygen evolution overpotential, and improving electrolysis efficiency.

[0026] 4. The end of the microchannel smoothly transitions to the outlet through a tapered tapered section, reducing fluid resistance and energy loss, and avoiding local overheating or reaction stagnation caused by bubble retention.

[0027] 5. The major axis of the elliptical shape aligns with the mainstream direction of the electrolyte, reducing turbulence and backflow, resulting in a 10%–20% lower pressure drop compared to a circular shape. The symmetry of the elliptical shape also improves flow field uniformity, reducing local velocity differences and shortening the time bubbles spend adhering to the electrode surface by 10%–20%, thus lowering the polarization voltage by 0.1–0.2 V. Under 2 MPa pressure, the one-piece elliptical end plate exhibits 10%–20% less deflection than a circular shape, and a 25% improvement in the uniformity of contact pressure at the sealing surface. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of this utility model;

[0029] Figure 2 This is a schematic diagram of the internal structure of this utility model;

[0030] Figure 3 This is an enlarged structural schematic diagram of point A in this utility model;

[0031] Figure 4 This is a cross-sectional structural schematic diagram of the present invention;

[0032] Figure 5 This is an enlarged structural schematic diagram of point B in this utility model;

[0033] In the figure: 1. Elliptical electrode frame; 2. Planar electrode; 3. Spherical electrode; 4. Cavity; 5. Gas-liquid inlet; 6. Gas-liquid outlet; 7. Internal flow channel; 8. Nanoporous nickel layer; 9. Lead wire; 901 core layer; 902 insulating layer; 903 outer layer. Detailed Implementation

[0034] This invention provides an end plate for an alkaline water electrolyzer, employing an elliptical electrode frame arranged laterally along its long axis. This asymmetrical structure disperses mechanical stress during electrolyzer assembly, reducing the risk of seal failure due to stress concentration. The elliptical contour matches the internal spatial distribution of the electrolyzer, dominating the fluid transport path along the long axis and optimizing the pressure distribution at the electrode edges along the short axis, thus improving the flow dead zones caused by corner eddies in traditional circular / square structures. The combination of planar electrodes (flat electrode surfaces) and spherical electrodes (pressure-resistant curved surfaces) forms a cavity. This cavity volume buffers instantaneous flow fluctuations of the electrolyte and gas, reducing the pressure impact of local pressure gradients on the diaphragm between the two electrodes.

[0035] The end plate features a three-stage arc-shaped flow channel along its long axis. The decreasing cross-sectional area of ​​the channel matches the fluid velocity gradient, minimizing flow attenuation at the edges. The internal flow channel employs a Koch curve fractal structure, filling the plate surface with 50%-72% coverage. This fractal structure extends the effective flow channel length through self-similarity, increasing the specific surface area for higher electrolysis efficiency. Helical guide vanes within the internal flow channel induce swirling flow, increasing the Reynolds number and enhancing gas-liquid mixing efficiency. Turbulent shear forces promote the breakup of large bubbles, reducing the shielding effect on active sites caused by bubbles covering the electrode surface. The microchannel ends are connected to the gas-liquid outlet via a tapered transition section, with continuously decreasing cross-sectional area suppressing fluid separation.

[0036] This invention utilizes a pulsed electroplating process to prepare a nanoporous nickel layer on the electrode plate. Alternating pulsed electric fields of 2V (deposition) and 1.2V (dissolution) are applied to achieve a three-dimensional interconnected pore structure through periodic dissolution control. Sodium saccharin is added to the electrolyte as a grain refiner, which, combined with the reverse pulse dissolution of coarse grains, achieves a surface roughness Ra ≤ 0.5μm.

[0037] Nickel sulfate hexahydrate (NiSO4·6H2O) provides nickel ions (Ni) in the electrolyte. 2+ (This is used for electrochemical deposition. The concentration range is 250-300 g / L. High concentrations of nickel salt can increase the deposition rate to 5-8 μm / min, ensuring a coating thickness of 30-50 μm. Sulfate ions (SO4) 2- Nickel chloride (NiCl₂·6H₂O) acts as a charge carrier, maintaining the electroneutrality of the electrolyte, while its weak coordination allows for rapid reduction and deposition of nickel ions on the cathode surface. Nickel chloride hexahydrate (NiCl₂·6H₂O) serves as an auxiliary salt, with its chloride ions (Cl₂) acting as a charge carrier. - This significantly improves the electrolyte conductivity to 18-22 mS / cm and reduces ohmic losses. - It can also promote the anodic dissolution of nickel during the reverse pulse phase, preferentially etching coarse grains with a particle size of 500 nm or more. The addition of nickel chloride makes the deposition-dissolution dynamic balance easier to control, avoiding excessive densification of the coating.

[0038] Boric acid (H3BO3) acts as a pH buffer, stabilizing the electrolyte pH within the range of 3.5-4.5. Boric acid dissociates to produce H+ and B(OH)4. - Ions, neutralizing the hydrogen evolution reaction at the cathode during electroplating (2H) + +2e -→ The local pH increase caused by H2↑ prevents the formation of nickel hydroxide precipitation. Sodium dodecyl sulfate (SDS), as an anionic surfactant, adsorbs onto the electrode surface through hydrophobic chains, reducing the surface tension of the solution to 40-45 mN / m. This effectively reduces the adhesion of hydrogen bubbles to the electrode surface, avoiding plating porosity and uneven local current density caused by bubble retention.

[0039] The electrolyte pH is adjusted to 3.5-4.5 using nitric acid; within this range, nickel ions are distributed as [Ni(H₂O)₆]. 2+ It exists in a stable form, avoiding hydrolysis to form Ni(OH)2 precipitate. Temperature control at 50-60℃ can reduce solution viscosity (from 1.2 cP to 0.8 cP), improve nickel ion mobility, and simultaneously suppress side reaction rates, ensuring efficient ion transport under a pulsed electric field.

[0040] The fractal structure of the microchannel array can be selected from either the Cochrane curve or the Peano curve. In practical engineering, the fractal iteration only needs to be up to level three.

[0041] The fractal structure of the microchannel array can be selected from either the Kock curve or the Peano curve. In practical engineering, the fractal iteration can be completed up to level three.

[0042] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0043] Example 1

[0044] An alkaline water electrolyzer end plate includes an elliptical electrode frame 1, with the long axis of the elliptical electrode frame 1 arranged laterally. The edge of the electrode frame is provided with an annular sealing groove with a built-in fluororubber O-ring. A planar electrode plate 2 and a spherical electrode plate 3 are embedded and sealed together by a hydraulic clamping device, with a sealing pressure ≥3MPa.

[0045] After being embedded and connected, the edge of the planar electrode plate 2 is welded to the elliptical electrode plate frame 1. The spherical electrode plate is a stamped plate, and its circumference is laser-welded to the planar electrode plate. A cavity 4 is provided between the planar electrode plate 2 and the spherical electrode plate 3. A gas-liquid inlet 5 is provided at the left end of the major axis of the elliptical electrode plate frame 1, and a gas-liquid outlet 6 is provided at the right end of the major axis. The gas-liquid inlet 5 and the gas-liquid outlet 6 are connected by an internal flow channel 7 within the cavity 4. The internal flow channel includes three levels of arc-shaped flow channels radially distributed along the major axis, and the first-level flow channel, second-level flow channel, and third-level flow channel are located from the center to the end of the minor axis. The center width of the first-level flow channel is 15 mm and the depth is 8 mm, the width of the second-level flow channel is 10 mm and the depth is 6 mm, and the width of the third-level flow channel is 5 mm and the depth is 4 mm. The three-stage flow channels are connected in series via a circular arc transition. The flow channels are radially connected to the microchannel array. The microchannel array adopts a Koch curve fractal structure with an iteration level of 2. The channel width is 3mm, and the depth gradient is 3mm (center of the electrode) → 2mm (edge ​​of the electrode). The fractal filling area accounts for 72% of the inner surface area of ​​the electrode. The end of the microchannel array is connected to the gas-liquid outlet 6.

[0046] The internal channel surface is provided with a nanoporous nickel layer 8. The preparation method includes sandblasting the surface of the titanium plate followed by acid washing, applying a forward voltage of 2.0V every 12ms and a reverse voltage of 1.2V every 7ms in the electrolyte, with a current density of 3A / dm³. 2 Simultaneously, the electrolyte was heated to 55℃ and electroplated for 40 minutes to obtain a nanoporous nickel layer with a thickness of 45±3μm. After rinsing with deionized water, it was annealed with hydrogen reduction at 300℃ for 2 hours. The surface of the nanoporous nickel layer exhibited honeycomb-like nanopores with a pore size of 50-200nm, a roughness Ra=0.65μm, and a specific surface area ≥15m². 2 / g.

[0047] Specifically, the electrolyte consists of 280 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 35 g / L boric acid, 0.8 g / L sodium saccharin, and 0.08 g / L sodium dodecyl sulfate, with the pH adjusted to 4.0 using nitric acid.

[0048] To facilitate the application of current to the terminal plates, the terminal plates are also equipped with leads 9. The structure of the leads 9 includes a core layer 901, an insulating layer 902, and an outer layer 903 arranged sequentially from the inside out. The core layer 901 is made of copper-plated silver wire with a diameter of 6 mm and a silver layer with a thickness of 20 μm. The inner layer of the insulating layer 902 is an alumina ceramic tube, and the outer layer 903 is made of Hastelloy C276 tube with an anodized surface. The lead 9 is sealed with a PTFE bushing with an interference fit where it passes through the plate frame.

[0049] Example 2

[0050] An alkaline water electrolyzer end plate, based on Example 1, features a microchannel array with a central region width of 5 mm, linearly decreasing to 1.5 mm towards both ends of the short axis; the central region depth is 5 mm, decreasing in three stages to 5 mm, 3 mm, and 1 mm. A conical transition section is provided at the gas-liquid outlet 6. The conical transition section is 10 mm long, has a cone angle of 8°, and its inner diameter gradually decreases from φ3 mm to φ2 mm.

[0051] Example 3

[0052] An alkaline water electrolyzer end plate, based on Example 1, has an alumina ceramic tube insulation layer 902 for the lead wire 9 and a polyimide film between the outer layer 903. A spiral guide vane is embedded in the three-stage arc-shaped flow channel. It adopts a double-headed spiral design, with the vane pitch alternately set to 3mm and 5mm. The vane height gradually changes from 3mm at the inlet to 5mm at the outlet, and the guide angle increases from 30° to 60°.

[0053] An alkaline water electrolyzer comprising at least one end plate as described in Examples 1-3.

[0054] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. An alkaline water electrolysis cell end plate, characterized in that, The device includes an elliptical electrode frame (1) with its long axis arranged horizontally and its short axis arranged vertically. A planar electrode (2) is sealed inside the elliptical electrode frame. A spherical electrode (3) is covered on one side of the planar electrode. A cavity (4) is formed between the planar electrode and the spherical electrode. A gas-liquid inlet (5) and a gas-liquid outlet (6) are respectively provided through the elliptical electrode frame at both ends of the cavity along its long axis. An internal flow channel (7) is provided inside the cavity along its long axis. A nanoporous nickel layer (8) is provided on the inner side of the planar electrode and / or the spherical electrode. At least one lead wire (9) is provided through the planar electrode and the spherical electrode through the elliptical electrode frame.

2. The terminal plate according to claim 1, characterized in that, The nanoporous nickel layer (8) is formed by a pulse electroplating process with alternating positive 2V / reverse 1.2V voltages. The nickel layer thickness is 50-100μm and the surface roughness Ra≤0.5μm.

3. The terminal plate according to claim 1, characterized in that, The internal flow channel (7) is radially distributed in at least three levels of arcs along the long axis to both ends of the short axis, and the width of the flow channel decreases from the center to the edge; the internal flow channel is radially provided with a microchannel array, which fills the inner surface of the planar electrode plate and / or spherical electrode plate along the fractal structure, and the filling area is ≥ 50% of the electrode plate area.

4. The terminal plate according to claim 1, characterized in that, The lead wire (9) is a composite structure, including a core layer (901), an insulating layer (902) and an outer layer (903) arranged sequentially from the inside to the outside.

5. The terminal plate according to claim 3, characterized in that, The width of the microchannel array (11) is ≤5mm, and its depth decreases from the center of the cavity to both ends of the short axis.

6. The terminal plate according to claim 3, characterized in that, The internal flow channel (7) is provided with a spiral guide vane, and the pitch of the spiral guide vane is 3-5mm.

7. The terminal plate according to claim 3, characterized in that, The end of the microchannel array (11) is connected to the gas-liquid outlet (6) through a conical transition section that extends along the inner side of the elliptical electrode frame.

8. The terminal plate according to claim 3, characterized in that, The ratio of the length of the major axis to the length of the minor axis of the elliptical pole plate frame (1) is 3:

2.

9. An alkaline water electrolysis cell, characterized in that, Includes the terminal plate structure as described in any one of claims 1-8.

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