Alkaline water electrolytic bath based on flow-engineered three-dimensional electrode

Abstract

The invention relates to the field of electrochemistry, in particular to the technical field of water electrolysis, in particular to an alkaline water electrolyzer based on a flow-engineered three-dimensional electrode, which can effectively improve the electrolysis efficiency while keeping low cost, comprises an electrode and a diaphragm, and is characterized in that the electrode is a Ni-based foam electrode and is directly contacted with the diaphragm; an upstream electrolyte inlet and a downstream electrolyte outlet are formed in the two ends of the electrode, and the downstream electrolyte outlet is an oxygen or hydrogen outlet at the same time.

Description

Technical Field

[0001] The invention relates to the field of electrochemistry, in particular to the field of water electrolysis technology, and in particular to an alkaline water electrolysis cell based on flow-engineered three-dimensional electrodes. Background Art

[0002] Currently, water electrolysis is mainly divided into alkaline water electrolysis (AWE) and proton exchange membrane water electrolysis (PEMWE). Alkaline water electrolysis is mainly based on low cost, but its efficiency and gas management capabilities are insufficient and it is susceptible to bubble accumulation. In contrast, PEM water electrolysis has higher electrolysis efficiency and hydrogen purity, but its cost is higher, mainly due to the use of rare precious metals as catalysts.

[0003] Therefore, how to achieve high efficiency close to PEM electrolysis in an alkaline electrolysis system while maintaining low cost has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an alkaline water electrolyzer based on flow-engineered three-dimensional electrodes, which effectively improves the electrolysis efficiency while maintaining low costs.

[0005] The technical solution is as follows: an alkaline water electrolyzer based on flow-engineered three-dimensional electrodes, comprising electrodes and diaphragms, characterized in that the electrodes are Ni-based foam electrodes and are directly in contact with the diaphragms, and upstream electrolyte inlets and downstream electrolyte outlets are provided at both ends of the electrodes, and the downstream electrolyte outlet is also an oxygen or hydrogen outlet.

[0006] It is further characterized in that the electrode is a three-dimensional porous structure based on nickel foam and is a double-layer structure, the layer close to the diaphragm is a fine-pore layer, and the layer far from the diaphragm is a coarse-pore layer; The surface of the electrode is coated with a Raney Ni coating and activated.

[0007] After adopting the present invention, a zero-gap design is adopted, the electrode is in direct contact with the diaphragm, the resistance of the electrolyte is reduced, the electrolyte flows in from the upstream inlet and is discharged from the downstream outlet, a uniform fluid environment is formed, the mass transfer of the electrolyte is improved, and the gas escape efficiency is enhanced, the energy loss caused by the bubble shielding effect is reduced, thereby improving the electrolysis efficiency, and the Ni-based foam electrode has a low cost of use; further, the design of the three-dimensional electrode can better improve the electrolysis efficiency of alkaline water electrolysis, so that it can achieve high current density at a lower voltage, reaching the performance level of a proton exchange membrane water electrolyzer. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic structural diagram of the electrolytic cell of the present invention; Figure 2It is a double-layer structure of electrodes; Figure 3 : CFD simulation results showing the fluid dynamics inside the electrolyzer. DETAILED DESCRIPTION

[0009] See Figure 1 , Figure 2 As shown, an alkaline water electrolyzer based on flow-engineered three-dimensional electrodes includes electrodes and diaphragms. The electrodes include an anode 2 and a cathode 6. The electrodes are Ni-based foam electrodes with a three-dimensional porous structure, which is beneficial to optimizing electrolyte penetration and bubble discharge. The electrode surface is coated with a Raney Ni coating and activated to obtain an electrode with high catalytic activity, thereby increasing the electrochemical reaction rate. This design can reduce ohmic resistance and improve electrolysis efficiency.

[0010] The electrode has a double-layer structure. The fine-pore layer (pore size 450 µm) close to the diaphragm 4 is used for efficient catalytic reaction, while the coarse-pore layer (pore size 3000 µm) away from the diaphragm is used to promote gas escape and liquid flow, thereby reducing the bubble shielding effect.

[0011] The anode 2 and the cathode 6 are in direct contact with the diaphragm 4 to reduce the resistance of the electrolyte. At the same time, the flow path of the electrolyte inside the chamber is optimized and a distributed liquid inlet is designed to ensure that the electrolyte is evenly distributed on the electrode surface to avoid local overreaction or depletion of reactants.

[0012] The specific method is as follows: the alkali solution coming in from the anode 2 and the cathode 6 first passes through a conical expansion section, the angle of which can be optimized so that the alkali solution can be evenly spread outward, or a porous distribution plate is set when the alkali solution passes through this area to distribute the alkali solution, and finally the alkali solution is evenly distributed when it enters the electrode area.

[0013] Both the anode 2 and the cathode 6 are provided with an upstream electrolyte inlet and a downstream electrolyte outlet, wherein the upstream electrolyte inlet of the anode 2 is a positive alkaline solution inlet 1, and the downstream electrolyte outlet is an anode alkaline solution and oxygen outlet 3, and the upstream electrolyte inlet of the cathode 6 is a negative alkaline solution inlet 7, and the downstream electrolyte outlet is a cathode alkaline solution and hydrogen outlet 5. The electrolyte flows in from the upstream inlet and is discharged from the downstream outlet to form a uniform fluid environment. This design helps to improve the mass transfer of the electrolyte and enhance the gas escape efficiency.

[0014] The steps of electrolysis process 1. Electrolyte configuration A 30wt% KOH solution was used as the alkaline electrolyte solution and was fully stirred to ensure uniformity. The pH value and temperature of the electrolyte were controlled at around 10-12 and 30°C to maintain a stable electrolysis environment.

[0015] 2. Start-up of electrolyzer The electrolyte was pumped into the electrolytic cell from the upstream inlet, with the flow rate controlled between 0.1 and 0.5 L / min to form a uniform flow field. The power supply was turned on and the voltage was applied gradually, with the initial voltage set to 1.8 V and gradually increased to the required 2 V until the current density reached 2 A / cm².

[0016] 3. Electrolysis process monitoring Monitor the current density and voltage changes of the electrolytic cell through the voltage and current detector on the electrolytic cell to ensure stable operation. Observe the generation and escape of bubbles to ensure that bubbles are not retained on the electrode surface, thereby reducing the polarization effect. Regularly check the electrolyte temperature and pH value. If there is a change, adjust it by cooling or adding KOH solution to maintain the stability of the electrolytic conditions.

[0017] 4. Gas collection Hydrogen and oxygen are collected separately through the gas outlet pipes set at both ends of the electrolyzer to ensure the integrity of the diaphragm and no cross contamination. The generation rate of hydrogen and oxygen is measured by gas flow meters downstream to verify the electrolysis efficiency, and the purity of the gas is analyzed by gas chromatography.

[0018] 5. Electrolyzer performance evaluation The parameters of the electrolyzer, such as current density, voltage, gas purity, etc., are recorded and analyzed to evaluate the performance of the electrolyzer at different current densities.

[0019] Compare energy consumption and gas production under different operating conditions, ensure high-purity hydrogen and oxygen with low energy consumption, and analyze and optimize the efficiency of the electrolyzer.

[0020] In addition, computational fluid dynamics (CFD) software is used to simulate the flow field in the electrolytic cell and optimize the electrode and flow distribution structure. Through CFD simulation, it is ensured that the upstream electrolyte can be evenly distributed on the entire electrode surface after entering the electrolytic cell, while generating lateral flow above the electrode surface.

[0021] This lateral flow design allows gas to escape quickly, reducing the interference of bubble retention on electrode reactions and ensuring continuous operation with high electrolysis efficiency.

[0022] The experimental process is as follows: 1. Experimental Setup Use CFD simulation tools to verify the fluid flow in the electrolytic cell and optimize the electrolyte flow rate and electrode structure design. Set multiple flow rate conditions (0.05 L / min, 0.1 L / min, 0.2 L / min) to test the electrolyte distribution in the electrolytic cell, and observe and record the bubble escape, current density and electrolysis efficiency under different flow rate conditions.

[0023] 2. Data Recording and Analysis A high-resolution camera is used to record the distribution and escape path of bubbles on the electrode surface during electrolysis, and the flow rate of the electrolyte is optimized by analyzing the formation and detachment of bubbles.

[0024] The electrolysis efficiency and current density under different flow rate conditions were compared to find the optimal flow rate condition to ensure uniform distribution of the electrolyte and maximize the electrolysis efficiency.

[0025] 3. Experimental Results It was found that when the electrolyte flow rate was 0.1 L / min, the bubbles on the electrode surface could be quickly detached, and the current density and electrolysis efficiency reached the optimal state. This flow rate not only ensured the uniform distribution of the electrolyte, but also avoided the increase in energy consumption caused by high flow rate. The simulation results are shown in Figure 2. Figure 3 shown.

Claims

1. An alkaline water electrolyzer based on flow-engineered three-dimensional electrodes, comprising electrodes and a diaphragm, characterized in that: The electrode is a Ni-based foam electrode and is in direct contact with the diaphragm. An upstream electrolyte inlet and a downstream electrolyte outlet are provided at both ends of the electrode, and the downstream electrolyte outlet is also an oxygen or hydrogen outlet.

2. The alkaline water electrolyzer based on flow-engineered three-dimensional electrodes according to claim 1, characterized in that: The electrode is a three-dimensional porous structure based on nickel foam and has a double-layer structure, wherein the layer close to the diaphragm is a fine-pore layer, and the layer far from the diaphragm is a coarse-pore layer.

3. The alkaline water electrolyzer based on flow-engineered three-dimensional electrodes according to claim 1, characterized in that: The surface of the electrode is coated with a Raney Ni coating and activated.

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