Cathode water inlet lunar surface water electrolysis device and cathode catalyst and catalyst layer preparation method

Abstract

The invention discloses a cathode water inlet lunar surface water electrolysis device and a preparation method of a cathode catalyst and a catalyst layer, and relates to the technical field of preparation of hydrogen and oxygen from lunar surface water electrolysis. The bipolar plate comprises a lower end face clamping plate, a lower insulating plate is detachably and fixedly installed above the lower end face clamping plate, a lower single-face polar plate is detachably and fixedly installed above the lower insulating plate, and a plurality of bipolar plate units are detachably and fixedly installed above the lower single-face polar plate. According to the proton exchange membrane water electrolysis reaction principle, the low gravity acceleration of the lunar surface and the vacuum environment characteristics, the cathode water inlet lunar surface water electrolysis device is designed, the flow field structure, the liquid-gas diffusion layer structure and the preparation of the cathode catalyst can be provided, and the water electrolysis device can adapt to the low gravity environment of the lunar surface and can be used for water electrolysis of the lunar surface. The dynamic polarization, ohmic polarization and mass transfer polarization of an electrolyzed water structure are effectively reduced, the technical thought of producing high-purity oxygen and hydrogen on the surface of the moon is suitable, and basic conditions are created for vital movement and energy requirements of terrestrial organisms on the moon.

Description

Technical Field

[0001] The present invention relates to the technical field of lunar surface electrolysis of water to produce hydrogen and oxygen, and in particular to a lunar surface cathode water inlet type water electrolysis device and a method for preparing a cathode catalyst and a catalytic layer thereof. Background Art

[0002] Hydrogen has attracted widespread attention as a clean energy source. As an energy carrier, hydrogen is one of the most promising solutions to the intermittent nature of renewable energy. When hydrogen is converted into electricity, it emits only water, no carbon.

[0003] Among traditional hydrogen production methods, reforming fossil fuels (such as methane and coal) is widely used, but the manufacturing process generates significant carbon emissions. Water electrolysis can significantly reduce greenhouse gas emissions and is a promising approach for producing green hydrogen. Mature technical routes for water electrolysis include alkaline water electrolysis and acidic water electrolysis (proton exchange membrane electrolysis). Proton exchange membrane electrolysis is valued for its small size, high energy density, and inherent safety.

[0004] Oxygen is a substance necessary for maintaining life. In the process of human exploration of space, cheap, safe and efficient production of oxygen has always been an important issue. In the 1970s, NASA developed a proton exchange membrane electrolysis water oxygen production technology for spacecraft life systems. This is a set of anode water electrolysis water oxygen production technology ( Figure 4 In a), the oxygen produced contains a large amount of water vapor and needs to go through a complex steam-water separation system to obtain high-purity oxygen. The cathode water electrolysis oxygen production system solves the problem of producing oxygen purity ( Figure 4 b), however, the anode often lacks water, resulting in the inability of the cathode water-inlet lunar surface electrolysis device to work stably and continuously. Moreover, under low gravity (or zero microgravity) conditions, due to the difficulty in desorption of cathode bubbles, the active sites of the cathode catalyst are covered, and the electrolysis efficiency is only about 50% of the anode water-inlet electrolysis technology. For this reason, the present invention proposes a cathode water-inlet lunar surface electrolysis device and a cathode catalyst and a method for preparing a catalytic layer. Summary of the Invention

[0005] The purpose of the present invention is to provide a cathode water inlet lunar surface electrolysis device and a cathode catalyst and catalytic layer preparation method, which can improve the overall electrolysis efficiency of the cathode water inlet electrolysis scheme in the low gravity environment of the lunar surface.

[0006] According to a first aspect of the present invention, in order to achieve the above-mentioned object, the present invention provides the following technical solution: a cathode water inlet lunar surface electrolysis device, comprising a lower end surface clamping plate, a lower insulating plate is detachably fixedly installed above the lower end surface clamping plate, a lower single-sided electrode plate is detachably fixedly installed above the lower insulating plate, a plurality of groups of bipolar plate units are detachably fixedly installed above the lower single-sided electrode plate, and an LGDL layer, a membrane electrode assembly and a PTL layer are detachably fixedly installed in sequence from bottom to top between each two groups of bipolar plate units;

[0007] An upper single-sided plate is detachably fixedly mounted above the bipolar plate unit, an upper insulating plate is detachably fixedly mounted above the upper single-sided plate, an upper end surface clamping plate is detachably fixedly mounted above the upper insulating plate, and a water inlet, an oxygen outlet, a nitrogen inlet, and a hydrogen outlet are respectively mounted on the top of the upper end surface clamping plate;

[0008] One side of the lower single-sided plate is provided with a positive electrode connection terminal, and one side of the upper single-sided plate is provided with a negative electrode connection terminal;

[0009] The membrane electrode assembly includes a three-layer structure of anode catalyst, proton exchange membrane and cathode catalyst from bottom to top. The anode catalyst layer is connected to the PTL layer for the transmission of electrolyte and gas and the conduction of electrons and heat. The cathode catalyst layer is connected to the LGDL layer for providing a water transmission channel and a gas diffusion channel.

[0010] The bipolar plate unit includes a cathode plate and an anode plate. A cathode flow field structure is provided on the side wall of the cathode plate, and an anode flow field structure is provided on the side wall of the cathode plate, which is used to promote gas-liquid transmission convection under low microgravity conditions on the lunar surface.

[0011] Furthermore, fixing feet are installed on both sides of the lower end splint by bolts, and a fixing rod is provided between the lower end splint and the upper end splint. The two ends of the fixing rod are tightened with nuts to install and fix the lower end splint and the upper end splint.

[0012] Furthermore, the lower single-sided plate is set as an anode plate, and the upper single-sided plate is set as a cathode plate.

[0013] Furthermore, sealing rings are provided between the lower insulating plate, the lower single-sided electrode plate, the two groups of bipolar plate units, the upper single-sided electrode plate and the upper insulating plate.

[0014] Furthermore, in the two groups of bipolar plate units, the side facing the upper end surface clamping plate is set as the cathode plate, and the side facing the lower end surface clamping plate is set as the anode plate.

[0015] Furthermore, the cathode flow field structure includes a cathode inlet and a cathode outlet provided at the diagonal position of the cathode plate, and two groups of flow channels are connected at a quarter arc position between the cathode inlet and the cathode outlet, each group having two flow channels, and the two groups of flow channels are arranged in a mirror-symmetrical manner as a whole;

[0016] Each flow channel at the cathode inlet is arranged in a serpentine spiral manner. The planar arrangement area of ​​each flow channel constitutes a serpentine flow field partition. The four flow channels constitute four serpentine flow field partitions, and the four serpentine flow field partitions are arranged in sequence along the horizontal direction. The areas of the four serpentine flow field partitions are the same, the number of bends in the four serpentine flow field partitions remains consistent, and the four flow channels have the same length. Therefore, the inlets of the four flow channels have the same inlet velocity and pressure, and the pressure, velocity bending loss and path loss of each flow channel are the same.

[0017] Furthermore, the anode flow field structure includes two oxygen outlets opened at the diagonal position of the anode plate, and multiple rows of parallel arrays of pins are arranged between the two oxygen outlets to form a square pin-shaped flow field, and four direct current channels are arranged between the square pin-shaped flow field and the two oxygen outlets, and the layout direction of the four direct current channels is perpendicular to the arrangement direction of the pins.

[0018] According to a second aspect of the present invention, the present invention provides a method for preparing a hydrophilic Pt / Cg cathode catalyst, which is used to prepare the cathode catalyst in the cathode water inlet lunar surface water electrolysis device described in the first aspect, comprising the following steps:

[0019] S1. Preparation of hydrophilic Pt / Cg support:

[0020] S11. Impregnation

[0021] (S11.1) At room temperature, impregnate high-porosity Ketjen Black ECP-600JD with 15% polyimide (PI) resin for 5 minutes to ensure that the polyimide (PI) resin is fully impregnated into the carbon black surface and pore structure, providing a nitrogen source and a graphitized carbon source for the carbon black;

[0022] (S11.2) Place the impregnated solid in a 60°C oven and dry for 180 minutes to remove the solvent.

[0023] S12. Curing

[0024] (S12.1) Place the dried impregnated solid in a vacuum oven. Maintain the vacuum level within 5 ps. Raise the oven temperature to 100°C at a rate of 2°C / min and hold for 30 min.

[0025] (S12.2) Continue to increase the oven temperature to 380°C at a rate of 2°C / min and hold for 40 min.

[0026] (S12.3) Place the impregnated solid dried in step (S12.2) in a low-temperature vacuum drying oven at -60°C, maintaining a vacuum level within 5 ps, and continue drying for 60 minutes.

[0027] S13. Carbonization and Graphitization

[0028] The solid dried in step (S12.3) was placed in a carbonization furnace for carbonization treatment. The temperature of the carbonization furnace was raised to 900°C at a rate of 3°C / min and kept at this temperature for 20 minutes. Then, the temperature of the carbonization furnace was further raised to 1100°C at a rate of 3°C / min and kept at this temperature for 30 minutes to carry out graphitization treatment, finally obtaining a carbonized and graphitized solid.

[0029] S14. Particle size control and contact angle measurement

[0030] (S14.1) The solid obtained from the carbonization and graphitization in step S13 is ground into a particle size of 0.1 mm to 0.2 mm using a mechanical grinder. The solid is then passed through an airflow mill, utilizing the autogenous grinding action of the solid and the impact of a high-speed airflow generated by compressed air, to grind into particles of 0.2 to 1 μm.

[0031] (S14.2) Weighing 10 mass fractions of a 20% PTFE emulsion and 1 mass fraction of carbonized and graphitized solid abrasive particles, immersing the solid abrasive particles in the PTFE emulsion, and dispersing them using a high shear disperser and ultrasonic waves for 10 minutes to form a slurry. The slurry is then applied to the surface of TORAY T-90 carbon paper by doctor blade coating to a coating thickness of not less than 50 μm. The TORAY T-90 carbon paper is then placed in an oven and heated at 350°C for 30 minutes. After cooling to room temperature, the contact angle of deionized water on the carbon paper coating is measured, and the contact angle is determined to be 33.015 degrees, thereby obtaining a hydrophilic carrier.

[0032] S15.Pt active metal support

[0033] Pt nanoparticles were loaded on a hydrophilic support using an impregnation reduction method, with a Pt loading of 20%. The Pt source was chloroplatinic acid and the reducing agent was ethylene glycol.

[0034] A certain proportion of sodium citrate surfactant is added to ensure that the particle size of platinum is within the range of 3-5nm;

[0035] Add a certain amount of NaOH solution to create an alkaline environment with a pH value between 8 and 10 during the impregnation process to ensure that the platinum particle size is concentrated and the Pt active metal is loaded;

[0036] The loaded hydrophilic Pt / Cg support was placed in a tube furnace and introduced with argon containing 2% hydrogen at a flow rate of no more than 20 SCCM. The temperature of the tube furnace was controlled between 700-800°C for 10 minutes to enhance the bonding strength between the Pt particles and the carbonized graphitized support.

[0037] S2. Preparation of coating slurry for cathode catalyst layer:

[0038] S21. Weigh 1 mass fraction of XC-72R carbon black, add 12 mass fractions of isopropanol and 12 mass fractions of deionized water, disperse using a high shear disperser for 8 minutes, and then cool at a low temperature of 5 ° C for 10 minutes;

[0039] S22. Then take 5% perfluorosulfonic acid resin aqueous solution 8 mass fraction, added to the carbon black / isopropyl alcohol / water dispersion system, high shear for 8 minutes, so that the slurry forms a uniform and fine paste, and then cooled at a low temperature of 5 ° C for 10 minutes;

[0040] S23. Add 8.5 mass fraction of Pt / Cg catalyst to the paste slurry of step S22, high shear dispersion for 5 minutes, ultrasonic dispersion for 5 minutes to form a viscous paste liquid, and then cool at a low temperature of 5 ° C for 10 minutes to obtain a coating slurry for the cathode catalyst layer;

[0041] S3. Preparation of cathode catalyst layer:

[0042] The coating slurry in step S23 is evenly coated on the surface of the proton exchange membrane using a slit coating method, with a coating thickness of 20 μm-25 μm, and then dried with hot air at 120° C.

[0043] According to a third aspect of the present invention, the present invention provides a method for preparing an anode PTL layer and a cathode LGDL layer, which is used to prepare the PTL layer in the cathode water inlet lunar surface electrolysis device described in the first aspect, comprising the following steps:

[0044] S01. A titanium foil having a thickness of 15-25 microns is used as a raw material, and the surface of the titanium foil is polished to a surface roughness of 1 μm;

[0045] S02. Evenly distribute circular holes or through holes in a combination of regular hexagons and circles on the titanium foil by etching or laser processing;

[0046] S03. A 100nm--150nm platinum layer is plated on the surface of the processed anode PTL layer and the cathode LGDL layer to reduce the bulk resistance of the anode PTL layer and the cathode LGDL layer and the contact resistance between the anode PTL layer, the cathode LGDL layer and the catalyst layer and the bipolar plate;

[0047] S04. Place the titanium foil processed in step S03 into a hot air heating box at 400-420°C, keep the temperature constant for 30 minutes, and then cool naturally to form a hydrophilic surface.

[0048] Furthermore, the specific dimensions of the processed circular holes are as follows:

[0049] The diameter of the circular hole is 100μm--300μm, the porosity is 0.3-0.37, the center distance between the circular holes is 100--300μm, and the diameter of the circular hole is equal to the center distance;

[0050] Processing through holes that are a combination of regular hexagons and circles is as follows:

[0051] The anode PTL layer and the cathode LGDL layer are distributed adjacent to each other by multiple hexagons. Each side of the central hexagon is connected to a similar hexagon. A circular ring is nested in the middle of a single hexagon. The circular ring is connected to the three sides of the hexagon. The inner radius of the circular ring is r = 0.1-0.3mm; the width of the circular ring is b = 0.3r-0.4r; the distance between the circular ring and the hexagon side is d = 0.3r-0.5r; the width of the hexagon side is h = 0.1-0.2mm; and the porosity is 0.3-0.5.

[0052] The present invention has at least the following beneficial effects:

[0053] 1. Cathode catalyst innovation: This invention uses a Pt / C catalyst with a hydrophilic graphitized carrier to improve the hydrophilicity and conductivity of the catalyst, solve the problem of bubbles covering the active sites of the catalyst in the low gravity environment on the lunar surface, and enhance the efficiency and stability of water electrolysis.

[0054] 2. Flow field structure optimization: The present invention uses CFD simulation to design the cathode four-partition serpentine flow field and the anode four-square pin-shaped flow field to promote gas-liquid convection, accelerate the separation of bubbles from the catalyst layer, and effectively improve the electrolysis efficiency.

[0055] 3. Efficient connection between the bipolar plates and the membrane electrode assembly: The anode plate of the bipolar plate unit of the present invention is connected to the upper single-sided plate (cathode plate), which is then connected to the anode catalyst layer of the membrane electrode assembly, achieving an alternating stack of anodes and cathodes. This design optimizes electric field distribution, reduces ohmic resistance, improves electrolysis efficiency, and enhances structural stability.

[0056] 4. Optimization of anode PTL and cathode LGDL: The present invention uses ultra-thin titanium foil to make the PTL layer and LGDL layer, and the titanium foil anode PTL and cathode LGDL have a smooth surface, and the interface contact area with the catalyst layer and the bipolar plate is large, which significantly reduces the interface contact resistance between the catalyst layer and the bipolar plate, thereby greatly reducing the total ohmic resistance of the electrolysis device and improving the performance and durability of the water electrolysis device.

[0057] 4. Overall structural stability and maintainability: The fixing rod, nut, and sealing ring work together to achieve overall fixation and sealing of the device, ensuring structural stability and preventing electrolyte and gas leakage. This also facilitates maintenance and component replacement, improving the reliability and maintainability of the device.

[0058] 5. This invention uses cathode water inlet technology to ensure that the oxygen produced by the anode has low water content and high purity. It is also specially designed for the low gravity, high vacuum, extreme temperature and other environmental conditions on the lunar surface, ensuring that the device can operate stably on the lunar surface and providing technical support for lunar base construction and deep space exploration.

[0059] 6. Modularity and scalability: The overall design of the cathode water inlet lunar surface water electrolysis device of the present invention has good modularity and scalability, and the scale and production capacity of the water electrolysis device can be flexibly adjusted according to actual needs.

[0060] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of the overall structure of the cathode water inlet lunar surface water electrolysis device of the present invention, wherein a is a schematic diagram of the unfolded state, and b is a schematic diagram of the assembled state;

[0062] Figure 2 Schematic diagram of the structure of the bipolar plate in Example 1 of the present invention, wherein a is a schematic diagram of the structure of the anode plate, b is a schematic diagram of the structure of the cathode plate, and c is a three-dimensional schematic diagram of the assembled bipolar plate;

[0063] Figure 3 Schematic diagram of the structure of the gas-liquid diffusion layer of the present invention;

[0064] Figure 4 Schematic diagram of the principle of an anode water inlet electrolytic cell and a cathode water inlet electrolytic cell in the prior art, wherein a is a schematic diagram of the anode water inlet and b is a schematic diagram of the cathode water inlet;

[0065] Figure 5 Schematic diagram of the cathode water inlet and cathode bubble generation process in the prior art of the present invention;

[0066] Figure 6 Schematic diagram of HRTEM at different graphitization process temperatures (500° C., 700° C., 900° C., 1100° C., 1300° C., and 1500° C.) in Example 2 of the present invention;

[0067] Figure 7 Schematic diagram of the hydrophobic surface of XC72R in the prior art (left) and the hydrophilic surface structure of Cg in the present invention (right);

[0068] Figure 8Schematic diagram comparing the mass activity and specific activity of four catalysts: TKK20%, HS9000, Pt / C, and Pt / Cg;

[0069] Figure 9 Schematic diagram of the Pt / Cg durability test results of the present invention;

[0070] Figure 10 Schematic diagram of hydrogen concentration distribution in parallel flow field in the prior art;

[0071] Figure 11 Schematic diagram of water flow velocity distribution in parallel flow field in the prior art;

[0072] Figure 12 Schematic diagram of hydrogen concentration distribution of the cathode serpentine flow field structure of the present invention;

[0073] Figure 13 Schematic diagram of water flow velocity distribution of the cathode serpentine flow field structure of the present invention;

[0074] Figure 14 Schematic diagram of the structure of the cathode serpentine flow field of the present invention;

[0075] Figure 15 It is a structural diagram of the pin flow field in the prior art;

[0076] Figure 16 This is a schematic diagram of the structure of the anode square pin-shaped flow field of the present invention;

[0077] Figure 17 Schematic diagram of bubble volume growth on different hydrophilic and hydrophobic surfaces;

[0078] Figure 18 It is a structural diagram of titanium felt PTL in the prior art;

[0079] Figure 19 Schematic diagram of the structure of the titanium foil PTL in the present invention;

[0080] Figure 20 Schematic diagram of the circular hole structure of the anode PTL layer and the cathode LGDL layer in Example 3 of the present invention;

[0081] Figure 21 Schematic diagram of the circular hole structure of the anode PTL layer and the cathode LGDL layer in the fourth embodiment of the present invention.

[0082] Reference numerals:

[0083] 1. Upper end face splint; 2. Upper insulating plate; 3. Upper single-sided electrode plate; 4. Sealing ring; 5. Bipolar plate unit; 6. PTL layer; 7. Membrane electrode assembly; 8. LGDL layer; 10. Lower single-sided electrode plate; 11. Lower insulating plate; 12. Lower end face splint; 13. Nitrogen inlet; 14. Water inlet; 15. Hydrogen outlet; 16. Oxygen outlet; 17. Nut; 18. Negative electrode terminal; 19. Fixing rod; 20. Positive electrode terminal; 21. Fixing foot. DETAILED DESCRIPTION

[0084] The following will be combined with the accompanying drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present disclosure.

[0085] Example 1:

[0086] See also Figures 1-21 The present invention provides a technical solution: a cathode water inlet lunar surface water electrolysis device, comprising a lower end surface clamping plate 12, a lower insulating plate 11 is detachably fixedly mounted above the lower end surface clamping plate 12, a lower single-sided electrode plate 10 is detachably fixedly mounted above the lower insulating plate 11, a plurality of groups of bipolar plate units 5 are detachably fixedly mounted above the lower single-sided electrode plate 10 (the bipolar plate units 5 can be increased or decreased according to the electrolysis power requirements), and an LGDL layer 8, a membrane electrode assembly 7, and a PTL layer 6 are detachably fixedly mounted between each two groups of bipolar plate units 5 from bottom to top;

[0087] An upper single-sided plate 3 is detachably fixedly mounted above the bipolar plate unit 5, an upper insulating plate 2 is detachably fixedly mounted above the upper single-sided plate 3, an upper end surface clamping plate 1 is detachably fixedly mounted above the upper insulating plate 2, and a water inlet 14, an oxygen outlet 16, a nitrogen inlet 13, and a hydrogen outlet 15 are respectively mounted on the top of the upper end surface clamping plate 1;

[0088] It should be noted that the nitrogen inlet 13 also serves as the oxygen outlet 16 during the oxygen production stage, and the hydrogen outlet 15 also serves as the water outlet for mixed discharge;

[0089] A positive terminal 20 is provided on one side of the lower single-sided plate 10, and a negative terminal 18 is provided on one side of the upper single-sided plate 3;

[0090] The membrane electrode assembly 7 includes a three-layer structure of an anode catalyst, a proton exchange membrane, and a cathode catalyst from bottom to top. The anode catalyst layer is connected to the PTL layer 6 for the transmission of electrolytes and gases and the conduction of electrons and heat. The cathode catalyst layer is connected to the LGDL layer 8 for providing a water transmission channel and a gas diffusion channel.

[0091] The bipolar plate unit 5 includes a cathode plate and an anode plate. A cathode flow field structure is provided on the side wall of the cathode plate, and an anode flow field structure is provided on the side wall of the cathode plate to promote gas-liquid convection under low microgravity conditions on the lunar surface.

[0092] According to the technical solution of this embodiment, fixing feet 21 are fixed on both sides of the lower end splint 12 by bolts, and a fixing rod 19 is provided between the lower end splint 12 and the upper end splint 1. The two ends of the fixing rod 19 are tightened by nuts 17 to install and fix the lower end splint 12 and the upper end splint 1. It should be noted that since the remaining structures are all located between the lower end splint 12 and the upper end splint 1, the fixing rod 19 and the nut 17 can be used to install and fix the overall structure of the cathode water inlet lunar surface electrolysis device, and when part of the structure needs to be maintained or replaced, it is also convenient for quick disassembly. At the same time, the fixing feet 21 are installed on both sides of the lower end splint 12 by bolts, and the lower end splint 12 is tightly connected to the upper end splint 1 by fixing rods 19 and nuts 17 to form an overall frame structure, which provides a stable support for the cathode water inlet lunar surface electrolysis device, ensures that the device can operate stably in the complex environment of the lunar surface, and reduces the loosening or displacement of components caused by vibration, impact and other factors.

[0093] According to the technical solution of this embodiment, the lower single-sided plate 10 is set as the anode plate, the upper single-sided plate 3 is set as the cathode plate, and a sealing ring 4 is provided between the lower insulating plate 11, the lower single-sided plate 10, the two sets of bipolar plate units 5, the upper single-sided plate 3 and the upper insulating plate 2. During the electrolysis of water, the electrolyte flows between the electrode and the membrane electrode assembly 7. The sealing ring 4 can effectively prevent the electrolyte from leaking from the gaps between the components, ensuring the smooth progress of the electrolysis process, avoiding electrolyte loss and corrosion to surrounding components, and the electrolysis of water will also produce hydrogen and oxygen. The sealing ring 4 can prevent the gas from leaking from the inside of the device, thereby improving the gas collection efficiency.

[0094] According to the technical solution of this embodiment, the side of the two groups of bipolar plate units 5 facing the upper end surface splint 1 is set as the cathode plate, and the side facing the lower end surface splint 12 is set as the anode plate. Since the upper single-sided plate 3 is the cathode plate, the upper single-sided plate 3 is located above the bipolar plate unit 5. Therefore, the anode plate in the bipolar plate unit 5 is connected to the upper single-sided plate 3, and the cathode plate in the bipolar plate unit 5 is connected to the anode PTL layer 6 below it. In this way, the cathode and anode are alternately stacked with each other. The alternating stacking design enables the electrolyte to be evenly distributed between the electrodes, ensuring that each anode and cathode can fully participate in the electrochemical reaction, thereby improving the overall efficiency of water electrolysis.

[0095] In accordance with the technical solution of this embodiment, the cathode flow field structure includes a cathode inlet and a cathode outlet located at the diagonal position of the cathode plate. Two groups of flow channels are connected at a quarter arc position between the cathode inlet and the cathode outlet. Each group contains two flow channels, and the two groups of flow channels are arranged in a mirror-symmetrical manner.

[0096] Each flow channel at the cathode inlet is arranged in a serpentine spiral manner. The planar arrangement area of ​​each flow channel constitutes a serpentine flow field partition. The four flow channels constitute four serpentine flow field partitions, and the four serpentine flow field partitions are arranged in sequence along the horizontal direction. The areas of the four serpentine flow field partitions are the same, the number of bends in the four serpentine flow field partitions remains consistent, and the four flow channels have the same length. Therefore, the inlets of the four flow channels have the same inlet velocity and pressure, and the pressure, velocity bending loss and path loss of each flow channel are the same.

[0097] Specifically, the design method of the cathode and anode flow fields of the cathode water inlet lunar surface electrolysis device is as follows:

[0098] The bipolar plate unit 5 and the monopolar plate of the cathode water inlet lunar surface electrolysis device are important components of the PEM electrolyzer. The bipolar plate unit 5 is processed with a specially designed fluid manifold and flow field. The flow field is made by machining or etching. The bipolar plate unit 5 in the electrolysis core has the functions of evenly flowing water to the reaction surface of the membrane electrode, conducting reactants, conducting electricity, and supporting the structure.

[0099] Under the low microgravity conditions on the lunar surface, the buoyancy of the bubbles is not enough to separate them from the surface of the catalyst active sites. A bubble layer will form in the catalyst layer, blocking the transmission of water and seriously affecting the reverse diffusion of water from the cathode to the anode.

[0100] This embodiment intends to establish a mathematical model of the flow of water and gas under low gravity conditions on the lunar surface, simulate the flow characteristics (velocity, concentration, pressure, etc.) of water and the generated hydrogen and oxygen in the designed flow field, and design a flow field of a cathode water inlet lunar electrolysis device suitable for the lunar surface. By reducing turbulence in the flow process and appropriately increasing the water flow pressure loss in the flow field, gas-liquid convection under low gravity conditions on the lunar surface is promoted, a pressure gradient between the flow channel-diffusion layer-catalyst layer is formed, the bubbles are accelerated to detach from the catalyst layer surface, and the electrolysis efficiency of the cathode water inlet core is improved.

[0101] The bipolar plate unit 5 is made of corrosion-resistant titanium metal plates. The surface of the bipolar plate unit 5 is plated with platinum, with a thickness of between 100 and 150 microns. The flow field on the bipolar plate unit 5 is simulated and designed using CFD software. In this embodiment, ANSYS FLUENT 2020 R2 software is used for design.

[0102] The flow characteristics of each flow field geometry design were evaluated through ANSYS simulation results, as well as their consistency with the flow field characteristics of the lunar cathode water electrolysis core. The dominant flow field under lunar surface conditions was selected. According to the cross-experimental principle, the fluid inlet pipe diameter, the number of flow channel bends, the fluid Reynolds number, the average fluid velocity (m / s) and other parameters were changed respectively to determine the final key parameters such as the flow field inlet and outlet, flow channel, and flow field geometry distribution:

[0103] Basic conditions for CFD simulation design:

[0104] The water electrolysis process is a stable and continuous process;

[0105] Cathode water inlet working condition, cathode water metering ratio is 200-400;

[0106] Gravitational acceleration on the moon g 月 =1.63m / s 2 ;

[0107] The operating environment is the lunar environment simulating the Earth's human habitation: T = 298K, P = 1 barg;

[0108] The specific design parameters are shown in the following table:

[0109] Table 1 ANSYS FLUENT 2020R2 design parameters

[0110] System parameters Input value unit Flow field geometry square / Ambient temperature 278---318 K Operating temperature 333---338 K Cathode stoichiometric ratio 200—400 times Gas pressure 1.01---3.03 105Pa Water inlet pressure 1.01---3.03 105Pa

[0111] According to the parameters in Table 1, a two-dimensional / three-dimensional flow field geometric model is established in CATIA software. The geometric flow field includes two types: straight channel flow field and partitioned serpentine flow field. The flow channel geometric parameters are selected according to the empirical parameter table. Then the models are imported into ANSYSFLUENT2020R2 software respectively, and the flow state of the gas-liquid two-phase flow in each model flow field is simulated. When the model is imported into ANSYSFLUENT2020R2, the flow direction of the cathode water inlet is determined, and the flow field area is set as needed.

[0112] Calculation model for the design of cathode flow field of lunar surface electrolysis device with cathode water inlet:

[0113] In order to simulate the flow morphology of fluid in different flow fields, the Navier-Stokes equation is used to determine the fluid mechanics design calculation model of the flow field:

[0114] Continuity equation:

[0115]

[0116] Momentum equation:

[0117]

[0118] Energy equation:

[0119]

[0120] Wherein, the mixing speed is defined as follows:

[0121]

[0122] Diffusion phase transport equation:

[0123]

[0124] Two-phase flow thermophysics equations

[0125]

[0126] Where T, k, and Cp are temperature, thermal conductivity, and specific heat capacity, respectively;

[0127] Two-phase thermal control boundary conditions:

[0128]

[0129] T=353K

[0130] C ps =12010.1471-80.4072T+0.30986T 2 -5.38186×10 -4 T 3 +3.62536×10 -7 T 4 273.15≤T

[0131] T=383K

[0132] k c =-0.86908+0.008948T-1.5836×10 -5 T 2 +7.9754×10 -9 T 3 273.15≤T

[0133] T=383K

[0134] The Reynolds number of the local area of ​​the flow field, D is the hydraulic diameter of the flow channel

[0135]

[0136] The above-mentioned fluid mechanics expressions are basic contents that those skilled in the art should know, and will not be explained in detail here.

[0137] The velocity and pressure of the raw water entering the cathode flow channel are used as dynamic variables. The calculation model includes the buoyancy effect caused by the lunar gravity, with the gravity vector pointing downward in the z direction.

[0138] Under the conditions of 300K, 0.2MPa, water density (p) = 997.7kg / m3, dynamic viscosity (u) = 9.61x104kg / ms, specific heat (Cp) = 4181.2J / kg°C, and thermal conductivity (k) = 0.603W / m°C, thermophysical properties were calculated as constants. Using the continuity and momentum equations, the ANSYS FLUENT software package enables the continuous calculation of velocity and pressure at a specific point in the flow field, and the intuitive display of the results in graphical form. These calculation results help evaluate the flow characteristics of each flow field geometry design and their conformity to the desired fluid flow characteristics of this embodiment.

[0139] Because the electrolysis core utilizes a cathode water inlet technology, the hydrodynamic characteristics of the flow field on the cathode side of the electrolyzer significantly impact the efficiency of the electrolyzer. Uniform water pressure distribution on the cathode reaction surface of the membrane electrode assembly (MEA) helps reduce the cell's internal resistance, thereby lowering the power required for electrolysis. Furthermore, uniform water flow across the MEA's reaction surface contributes to improved water electrolysis efficiency and prevents power erosion losses of the precious metal catalyst.

[0140] Select the typical serpentine flow field and parallel flow field forms, input the lunar surface electrolysis water limit and boundary conditions, and simulate the water velocity distribution of the typical flow field under a uniform pressure value of 0.2MPa ( Figure 11 、 Figure 13 ), and hydrogen concentration distribution ( Figure 10 、 Figure 12 ), these two simulated distributions can be used as criteria for selecting the optimal flow field. Fluid simulations show that the cathode utilizes a serpentine flow channel, the flow field has uniform water velocity, and the hydrogen concentration difference distribution range is within one order of magnitude, meeting the basic design requirements for the lunar cathode water inlet flow field. The flow field inlet and outlet, flow channel distribution, and flow field geometric parameters are the subject of protection in this embodiment.

[0141] Furthermore, the selection of cathode flow field - pressure distribution factors explain

[0142] Under the low gravity conditions on the lunar surface, the design of the flow field should try to increase the turbulence in the flow and promote the transmission of liquid and bubbles between the LGDL layer 8 and the catalyst layer. The pressure distribution in the cathode serpentine flow field gradually decreases along the diagonal line of the flow field from the inlet to the outlet. The reason for the pressure drop can be attributed to two factors: one is the loss caused by resistance, and the other is the loss caused by flow turbulence. The pressure drop of the parallel straight channel flow field is the most gentle, while the pressure drop of the serpentine flow channel is the largest. The parallel straight channel flow field exhibits better uniform pressure distribution characteristics. However, in order to form convection between the fluid diffusion layer and the catalyst layer, sufficient flow field pressure gradient must be guaranteed, and the fluid pressure should be kept above the threshold for optimizing performance. Although the pressure loss of the serpentine flow field is higher than that of the parallel flow field, it helps to generate turbulence and accelerate the overflow of bubbles from the core.

[0143] Cathode flow field selection-velocity distribution factors

[0144] The velocity distribution of the cathode flow field of the water electrolysis device is closely related to the flow field shape and geometric parameters. In all flow fields, the initial flow velocity and final flow velocity at the inlet and outlet are the same, thus maintaining the same total flow rate. However, due to the different flow channel geometry structures in local areas within the flow field, there is a problem of fluid distribution uniformity in the local flow. In a parallel flow field, the fluid velocity in the middle is relatively low, while the flow channels close to the two sides have a higher flow velocity, so the flow rate is larger (such as Figure 10 In the serpentine flow field, a relatively constant fluid velocity is generated along the length of the flow channel, and the velocity decreases only at the bends of the flow channel. Obviously, the serpentine flow field has a better fluid velocity distribution (such as Figure 12 ), which has practical significance for the uniformity of cathode water flow distribution in the cathode water inlet lunar surface electrolysis device.

[0145] Cathode flow field selection-hydrogen concentration distribution factors explained

[0146] Under different flow fields, the velocity distribution of the fluid determines the flow uniformity of the local area of ​​the flow field. The fluid velocity in the parallel channel flow field is lower than that in other flow fields. The migration speed of water-carrying bubbles from the catalyst layer to the flow field is slow, the hydrogen overflow efficiency is low, the hydrogen concentration in the catalyst layer and LGDL is too high, covering the catalyst active sites, and the performance of the electrolytic core is reduced. Through fluid simulation, the flow field pattern has a certain influence on the hydrogen molar concentration distribution. Figure 9 and Figure 11 As shown, the serpentine flow field clearly has a higher molar hydrogen concentration, while the parallel flow field has a lower molar hydrogen concentration. The water content in the LGDL layer 8 (gas-liquid diffusion layer) under the serpentine flow field is higher than that in the parallel flow field. In the turning sections of the serpentine flow field, the shear stress generated by the recirculating flow allows more water to reach the reaction layer, which helps improve mass transfer efficiency. The molar hydrogen concentration in the serpentine flow field is significantly greater than that in the parallel flow field.

[0147] The serpentine flow field design exhibits convection effects, enhancing water transport from the channel to the catalyst layer. The velocity at the catalyst layer in the serpentine design is an order of magnitude greater than that in the two parallel designs. This is evident in the water velocity contours in the figure above. The higher velocity at the serpentine bends creates more intense turbulence.

[0148] Description of cathode flow field structure characteristics:

[0149] In this embodiment, the upper single-sided plate 3 of the cathode and the bipolar plate unit 5 adopt a four-partition serpentine flow field form, such as Figure 14 The black box marks the cathode inlet and the cathode flow channel inlet. The cathode inlet adopts a circular inlet. There are two groups of four flow channels connected within the 1 / 4 arc range of the circular inlet. The depth, width, and ridge width of the flow channels are determined by Table 2. The angle between the two groups of flow channels is less than 90 degrees. The two groups of flow channels are symmetrically designed, and the axis of symmetry is the angle bisector of the two groups of flow channels. Each flow channel of the cathode inlet constitutes an independent serpentine flow field partition. The four serpentine partition flow fields have the same total flow channel length ( Figure 14 ), so that the cathode flow field is divided into 4 serpentine flow field partitions, and the flow field partitions have the same area. The number of bends in each partition remains consistent, and the flow channels have the same surface roughness. According to Bernoulli's principle, it is approximately considered that the pressure and velocity bending losses and path losses of each flow channel are the same, and the water source of each serpentine flow field partition is directly output from the cathode inlet. Therefore, the inlet water of the four partitions has approximately the same inlet velocity and pressure, which not only reduces the flow field water pressure drop loss, but also improves the uniformity of the water flow velocity distribution, meeting the design conditions of the lunar cathode water inlet flow field. At the outlet of the cathode flow field, two groups of four flow channels pass through their respective serpentine flow field areas and converge into the cathode outlet. The cathode outlet adopts a circular outlet with the same diameter as the cathode inlet, and is located on a set of diagonals of the cathode flow field. At the same time, the two groups of flow channels connected to the outlet are arranged symmetrically.

[0150] By designing a partitioned flow field, the cathode flow field's inlet and outlet fluxes are effectively utilized. Simulations are used to determine flow channel design parameters, minimizing pressure losses caused by channel turns and, consequently, reducing the overall pressure loss of the serpentine flow field. The inlet water achieves a favorable velocity distribution in the quartered serpentine flow field, facilitating the discharge of hydrogen bubbles from the electrolytic core under the low gravity conditions of the lunar surface.

[0151] According to the technical solution of this embodiment, the anode flow field structure includes two oxygen outlets 16 opened at the diagonal position of the anode plate, and multiple rows of parallel arrays of pins are arranged between the two oxygen outlets 16 to form a square pin-shaped flow field, and four direct current channels are arranged between the square pin-shaped flow field and the two oxygen outlets 16, and the layout direction of the four direct current channels is perpendicular to the arrangement direction of the pins.

[0152] Specifically, the OER (Oxidation Reaction) water oxidation reaction occurs at the anode of the water electrolysis device. Due to the cathode water inlet technology, only oxygen is generated at the anode, and the anode is in a single-phase airflow state. In this single-phase airflow state, the water required for the anode reaction comes from diffusion from the cathode. Therefore, the anode does not consider liquid water discharge, and the anode water supply is insufficient. The uniform distribution of oxygen on the anode surface depends on the reaction rate of the catalyst active sites and the uniform electron conductivity of the PTL / anode flow channel.

[0153] In order to make the generated oxygen uniformly distributed on the anode surface, the anode flow channel adopts a pin-type flow field design (such as Figure 15 The traditional anode feed pin flow field uses wide cross-channels, with the pin side length equal to the cross-channel width. This helps evenly distribute water across the MEA anode surface. In the lunar cathode feed electrolysis core anode, where water flow does not occur, the cross-channel width can be reduced, increasing the contact area between the anode plate pin-shaped flow channel and the PTL.

[0154] Description of the structural characteristics of the anode flow field:

[0155] In this embodiment, the anode water inlet electrolysis core anode monopolar plate and bipolar plate unit 5 adopts a pin-type flow field form. The anode flow field has two oxygen outlets 16 of the same diameter, the outlets are circular, and the circular area is 30-50% of the cathode flow field inlet. Figure 16 As shown, they are arranged symmetrically. There are four direct current channels connecting each anode flow field outlet. The direct current channel depth, width, and ridge width refer to the application example parameters in Table 2. The pin dimensions of the pin flow field area connected to the direct current channel meet B = (1.5-2)S, B = (1.5-2)H, the unit is mm. Each row of pins forms a parallel array, and the pins are arranged perpendicular to the direct current channel, as shown in Figure 2. Figure 16 shown.

[0156] This embodiment determines that the cathode flow field of the cathode water inlet lunar surface electrolysis device adopts a serpentine four-partition flow field ( Figure 14 ), the anode adopts a square pin-shaped flow field ( Figure 16 ), the application examples of cathode and anode flow field design parameters are shown in Table 4.

[0157] Table 2 Application example of cathode flow field parameters of the lunar surface electrolysis device with cathode water inlet Unit: mm Cathode flow field: channel depth H, channel width B, ridge width S; Anode flow field: square side B, square height H, spacing S;

[0158]

[0159] In summary, the water electrolysis device provided by the present invention is suitable for producing hydrogen and oxygen by electrolysis of water under the environmental conditions of the lunar surface. The principle of the cathode water inlet lunar surface electrolysis water device follows the basic principle of proton exchange membrane water electrolysis, and is based on the lunar surface environment. The design requirements adopt a cathode water inlet working condition that is different from the anode water inlet of the ground proton exchange membrane electrolysis water. In order to ensure the continuous and effective operation of the cathode water inlet lunar surface electrolysis water device, it is necessary to carry out design innovations in the cathode catalyst, bipolar plate flow field structure and core structure, liquid-gas diffusion layer, etc. At the same time, the anode catalyst, membrane electrode anode, etc. that are not specifically described in this embodiment still use the traditional ground proton exchange membrane water electrolysis basic technology, which will not be explained further below.

[0160] Example 2:

[0161] Cathode catalyst and catalytic layer preparation method:

[0162] At the beginning of electrolysis, hydrogen bubbles can be observed at the edge of the electrode. The average size of the bubbles is small and the distribution range is large. As the electrolysis progresses, the small bubbles move toward the adjacent large bubbles. The large bubbles begin to grow and the small bubbles repeatedly merge. Figure 5 ).

[0163] Maintaining the normal and efficient operation of the cathode-water-inlet lunar electrolysis core requires special design and improvements in catalysts, flow fields, and vapor-water diffusion layers. The cathode of the cathode-water-inlet lunar electrolysis core is a water-rich environment, and good wettability of the cathode catalyst is a basic condition for the diffusion of cathode water to the anode, ensuring the supply of anode water. The Pt / C catalyst on the ground has a hydrophobic structure and is suitable for high-gravity environments with strong convection activity. It cannot meet the requirements of cathode catalysts in low-gravity lunar electrolysis cores.

[0164] Furthermore, the low gravity of the moon makes the desorption of bubbles more difficult, leading to the formation of a stable gas film on the electrode surface. Hydrogen accumulation, in particular, in the cathode region inhibits the diffusion of water from the cathode to the anode, leading to a lack of water at the anode and affecting the continued progress of the reaction. Furthermore, the increased hydrogen generation rate at high current density exacerbates the bubble accumulation phenomenon, further exacerbating the anode water shortage.

[0165] In PEM water electrolysis devices on the ground, water is usually fed through the anode because water molecules are consumed by oxidation reactions on the anode side (H2O→2H++1 / 2O2+2e). The cathode uses a Pt / C catalyst, and the porous catalyst carrier is generally carbon black, which is a hydrophobic carrier. In the low gravity environment on the lunar surface, hydrogen bubbles cover the catalyst surface, thereby affecting the contact between water and the electrode and causing severe mass transfer polarization. Experiments have shown that enhancing the gas-repellent and hydrophilic properties of the cathode is an effective way to promote the rapid desorption of hydrogen bubbles. The key innovation in the cathode catalyst of the lunar electrolysis device with cathode water is the preparation of a hydrophilic graphitized carrier.

[0166] The cathode of the cathode water inlet lunar surface electrolysis water device described in this embodiment uses a hydrophilic structure catalyst. The carrier of this cathode catalyst has been modified through a special process and has high conductivity and a hydrophilic structure, which solves the problem of continuous operation of the lunar surface cathode water inlet electrolysis water core.

[0167] The cathodic hydrophilic structure Pt / Cg catalyst hydrophilic support in this embodiment has the following characteristics:

[0168] A. The carrier is modified by N doping to improve the hydrophilicity and conductivity of the carrier structure;

[0169] B. The carbon black matrix is ​​coated with a graphitized carbon source, and the surface of the carrier is graphitized at a graphitization process temperature below 1500°C;

[0170] In carbon support materials, nitrogen-containing atomic groups can act as carbon substituents, becoming functional groups attached to the outer layer of the carbon material. Nitrogen-containing atomic groups change the electronic structure of the carbon support material, forming an electron-rich outer layer structure of the support, thereby improving the conductivity and surface hydrophilicity of the support.

[0171] The reaction of ammonia with carbon materials under closed conditions can produce nitrogen-containing carbon-modified materials, but the nitrogen doping rate of this method is very low, generally not exceeding 2%. This embodiment combines a high-surface-area carbon black substrate with a low-temperature graphitized nitrogen-containing carbon source for surface coating, followed by curing and pre-oxidation processes. This results in a high nitrogen doping rate and a high degree of graphitization, significantly improving the material's durability compared to current commercial catalysts. Furthermore, the hydrophilic surface structure forms, making it suitable as a cathode-feed platinum catalyst support for a lunar electrolysis device.

[0172] This embodiment provides a method for preparing a hydrophilic Pt / Cg cathode catalyst, which is used to prepare the cathode catalyst in the cathode water inlet lunar surface water electrolysis device described in Example 1, comprising the following steps:

[0173] S1. Preparation of hydrophilic Pt / Cg support:

[0174] S11. Impregnation

[0175] (S11.1) At room temperature, impregnate high-porosity Ketjen Black ECP-600JD with 15% polyimide (PI) resin for 5 minutes to ensure that the polyimide (PI) resin is fully impregnated into the carbon black surface and pore structure, providing a nitrogen source and a graphitized carbon source for the carbon black;

[0176] (S11.2) Place the impregnated solid in a 60°C oven and dry for 180 minutes to remove the solvent.

[0177] S12. Curing

[0178] (S12.1) Place the dried impregnated solid in a vacuum oven. Maintain the vacuum level within 5 ps. Raise the oven temperature to 100°C at a rate of 2°C / min and hold for 30 min.

[0179] (S12.2) Continue to increase the oven temperature to 380°C at a rate of 2°C / min and hold for 40 min.

[0180] (S12.3) Place the impregnated solid dried in step (S12.2) in a low-temperature vacuum drying oven at -60°C, maintaining a vacuum level within 5 ps, and continue drying for 60 minutes.

[0181] S13. Carbonization and Graphitization

[0182] The solid after drying in step (S12.3) was divided into 5 equal parts, and the degree of graphitization under different process temperature conditions of 700°C, 900°C, 1100°C, 1300°C, and 1500°C was investigated, as shown in Table 3;

[0183] Table 3 Carbonization and graphitization process

[0184]

[0185] Under different carbonization and graphitization process conditions, the degree of graphitization of the carrier material is significantly different. Figure 6 These are HRTEM photos of the carrier at different temperatures. As the temperature increases, the degree of graphitization also increases. Sample 3 has a well-developed graphite crystal structure and the highest degree of graphitization. This shows that the factor that determines the degree of graphitization of the carrier is not only the temperature, but also related to the temperature zone distribution.

[0186] According to the technical solution of this embodiment, the solid dried in step (S12.3) is placed in a carbonization furnace for carbonization treatment. The temperature of the carbonization furnace is raised to 900°C at a carbonization furnace speed of 3°C / min and kept warm for 20 minutes. Then, the temperature of the carbonization furnace is further raised to 1100°C at a speed of 3°C / min and kept warm for 30 minutes for graphitization treatment, thereby finally obtaining a carbonized and graphitized solid.

[0187] S14. Particle size control and contact angle measurement

[0188] (S14.1) The solid obtained from the carbonization and graphitization in step S13 is ground into a particle size of 0.1 mm to 0.2 mm using a mechanical grinder. The solid is then passed through an airflow mill, utilizing the autogenous grinding action of the solid and the impact of a high-speed airflow generated by compressed air, to grind into particles of 0.2 to 1 μm.

[0189] (S14.2) Weigh 10 mass fractions of a 20% PTFE emulsion and 1 mass fraction of carbonized and graphitized solid abrasive particles, immerse the solid abrasive particles in the PTFE emulsion, and disperse them using a high shear disperser and ultrasonic waves for 10 minutes to form a slurry. The slurry is then applied to the surface of TORAY T-90 carbon paper by doctor blade coating to a coating thickness of not less than 50 μm. The TORAY T-90 carbon paper is then placed in an oven and kept at 350° C. for 30 minutes. After cooling to room temperature, the contact angle of deionized water on the carbon paper coating layer is measured, and the contact angle is determined to be 33.015 degrees, thereby obtaining a hydrophilic carrier ( Figure 7 );

[0190] S15.Pt active metal support

[0191] Pt nanoparticles were loaded on a hydrophilic support using an impregnation reduction method, with a Pt loading of 20%. The Pt source was chloroplatinic acid and the reducing agent was ethylene glycol.

[0192] A certain proportion of sodium citrate surfactant is added to ensure that the particle size of platinum is within the range of 3-5nm;

[0193] Add a certain amount of NaOH solution to create an alkaline environment with a pH value between 8 and 10 during the impregnation process to ensure that the platinum particle size is concentrated and the Pt active metal is loaded;

[0194] The loaded hydrophilic Pt / Cg support was placed in a tube furnace and introduced with argon containing 2% hydrogen at a flow rate of no more than 20 SCCM. The temperature of the tube furnace was controlled between 700-800°C for 10 minutes to enhance the bonding strength between the Pt particles and the carbonized graphitized support, thereby improving the durability of the catalyst.

[0195] S2. Preparation of coating slurry for cathode catalyst layer:

[0196] The membrane electrode is the core component of the cathode-inlet lunar surface water electrolysis device. The membrane electrode is usually composed of a three-layer structure of cathode catalyst layer-proton exchange membrane-anode catalyst layer. The cathode reaction and anode reaction of water electrolysis are carried out on the cathode catalyst layer and the anode catalyst layer respectively. The proton exchange membrane is responsible for the transmission function of protons and water. Under the working conditions of cathode water inlet, water diffuses from the cathode to the anode through the proton exchange membrane, providing raw materials for the anode water decomposition reaction. When the anode reaction lacks water, the anode reaction efficiency is low and it will lead to adverse electrochemical reactions at high potential that affect the durability of the water electrolysis core. Therefore, ensuring the diffusion of water from the cathode to the anode is the key core technology of the cathode water inlet electrolysis core.

[0197] Cathode or anode slurries can be applied to the surface of the proton exchange membrane through processes such as spraying and coating. The cathode slurry formulation determines the composition of the cathode catalyst layer, which in turn determines the performance of the catalyst layer. Under the cathode water inlet conditions of a lunar surface water electrolysis device, the structure and composition of the cathode catalyst layer determine the performance of the membrane electrode. The cathode catalyst layer slurry is generally composed of alcohols, perfluorosulfonic acid solution, water and cathode catalyst in a certain composition. The cathode catalyst with a certain component ratio is fully in contact with the perfluorosulfonic acid solution, so that the perfluorosulfonic acid solution is coated on the surface of the cathode catalyst. The purpose is to enhance the proton transfer between the active site of the cathode catalyst and the perfluorosulfonic acid. Perfluorosulfonic acid is a polymer structure composed of hydrophobic polytetrafluoroethylene long chains and hydrophilic ether sulfonic acid side chains. The protons generated at the anode reach the active site through the perfluorosulfonic acid cover, and the oxygen generated by electrolysis needs to be discharged through the perfluorosulfonic acid cover. Due to the hydrophobic long main chain structure of perfluorosulfonic acid, the catalyst surface can be regarded as a relatively hydrophobic surface. This surface not only hinders the infiltration and transmission of water to the anode, but also prevents the hydrogen generated at the cathode from being smoothly desorbed from the catalyst active site. In addition, the sulfonic acid group SO32- in direct contact with Pt will also poison the Pt catalyst, thereby reducing the catalyst activity.

[0198] This embodiment solves the water transmission and bubble desorption problems at the cathode of the membrane electrode of the cathode water electrolysis device through the following process:

[0199] S21. Weigh 1 mass fraction of XC-72R carbon black, add 12 mass fractions of isopropanol and 12 mass fractions of deionized water, disperse using a high shear disperser for 8 minutes, and then cool at a low temperature of 5 ° C for 10 minutes;

[0200] S22. Then take 5% perfluorosulfonic acid resin aqueous solution 8 mass fraction, added to the carbon black / isopropyl alcohol / water dispersion system, high shear for 8 minutes, so that the slurry forms a uniform and fine paste, and then cooled at a low temperature of 5 ° C for 10 minutes;

[0201] S23. Add 8.5 mass fraction of Pt / Cg catalyst to the paste slurry of step S22, high shear dispersion for 5 minutes, ultrasonic dispersion for 5 minutes to form a viscous paste liquid, and then cool at a low temperature of 5 ° C for 10 minutes to obtain a coating slurry for the cathode catalyst layer;

[0202] S3. Preparation of cathode catalyst layer:

[0203] The coating slurry in step S23 is evenly coated on the surface of the proton exchange membrane using a slit coating method, with a coating thickness of 20 μm-25 μm, and then dried with hot air at 120° C.

[0204] Performance test of Pt / Cg catalyst in the cathode water inlet lunar electrolysis core:

[0205] 1. Statistics of hydrogen bubbles in hydrophobic Pt / C cathode and hydrophilic Pt / Cg cathode

[0206] Table 4 Electrolysis test cell operating conditions: cathode water inlet, inlet water temperature T = 60 ° C; 1.8V @ 0.5A / cm2

[0207] Time S Pt / C cathode Pt / Cg cathode Remark T＝15 About 3.2◇102 About 78 / T＝30 About 4.8◇102 About 131 / T＝45 About 4.3◇102 About 95 / Average diameter μm About 1,000 About 650

[0208] Table 4 above shows that the number of bubbles in the hydrophilic Pt / Cg cathode catalyst layer is approximately 20%-30% of that in the ordinary hydrophobic Pt / C cathode catalyst layer, and the average diameter of the bubbles is reduced by 50%. The hydrophilic Pt / Cg cathode is conducive to the desorption of bubbles and improves the mass transfer efficiency of the cathode water inlet.

[0209] 2. Comparison of mass activity and specific activity of four catalysts: TKK20%, HS9000, Pt / C, and Pt / Cg. Figure 8 It can be seen that under the cathode water inlet conditions of the water electrolysis device, Pt / Cg has the highest mass activity and specific activity.

[0210] 3. Pt / Cg durability test

[0211] like Figure 9 As shown in the figure, under the RDE test conditions, the voltage loss of the Pt / Cg catalyst was 13.5 mV at 10K cycles, which was better than that of the carbon black catalyst, indicating that the graphitized structure of the carrier effectively avoided the oxidative collapse of the carrier.

[0212] Example 3:

[0213] In the water electrolysis device, the anode PTL and the cathode LGDL are key components, whose main functions are to conduct electrons, guide bubbles, and conduct heat. In the ground water electrolysis core, the anode PTL is titanium felt, which is made of titanium fiber. The contact between PTL and the catalyst layer and bipolar plate (BP) is the titanium fiber curved surface. The contact surface is discontinuous and the interface contact resistance is relatively large.

[0214] Under the cathode water inlet scheme of the lunar electrolysis device, the cathode bubble diameter is affected by the combined force of surface tension and buoyancy. The bubble profile is determined by the water flow parameters and the wettability of the bubble formation surface. According to the empirical formula for bubble diameter in the lunar environment (the following formula) obtained from our multiple experiments, the diameter of the bubble desorbed from the electrode surface is d0, the bubble contact angle is θ (in degrees), the surface tension is γ, the gravity is g, and the density of the surrounding liquid and the corresponding gas are ρ respectively. L and ρ G In the low gravity environment of the lunar surface, highly hydrophilic surfaces are crucial for enhancing bubble desorption. Hydrophilic surfaces produce smaller bubbles, and the air-liquid interface is small, resulting in weak friction. Bubbles easily slide off the surface and avoid clinging to it. The moving bubbles induce small-scale convection, enhancing product transport.

[0215]

[0216] The total pressure difference at the gas / liquid interface is equivalent to the gas / liquid interfacial energy γgl. The most relevant parameters related to bubble formation are the advancing contact angle and the receding contact angle (OR). Under the conditions of lunar gravitational acceleration, the buoyancy of the bubble increases linearly with the size of the bubble ( Figure 17 ), when the advancing contact angle is equal to the receding contact angle, the bubble stops growing. Under the action of water flow, the receding contact angle increases and exceeds the advancing contact angle when the bubble bursts.

[0217] Based on the above low gravity environment on the lunar surface, the buoyancy of the bubbles in the cathode of the electrolyzed water is insufficient to promote the discharge of the bubbles, which in turn leads to large mass transfer polarization. The design of the anode PTL and cathode LGDL must meet the following requirements:

[0218] (1) Suitable pore structure and pore shape design promote water vapor convection, allowing H2 / O2 to separate on the surface; H2 / O2 bubbles generated at the reaction site of the catalyst layer are diverted into the flow channel, reducing the H2 / O2 concentration in the catalytic electrode layer;

[0219] (2) Good electrical conductivity, efficient heat conduction and uniform heat distribution capabilities;

[0220] (3) Since bubbles adhere more strongly to hydrophobic surfaces, in order to accelerate the separation of bubbles from the anode PTL and cathode LGDL surfaces, the anode PTL and cathode LGDL surfaces are hydrophilic surfaces;

[0221] (4) Anode PTL can withstand high-potential corrosion environment of the anode;

[0222] (5) The surface roughness of the anode PTL and cathode LGDL is low, which reduces the contact resistance with the bipolar plate unit 5 and the catalyst layer.

[0223] In the oxygen-rich and high working potential environment of the anode, carbon will undergo electrochemical corrosion, which will degrade the PTL, resulting in poor conductivity and poor interface contact of the PTL, thereby reducing the performance of the electrolytic core. Therefore, carbon-based materials are not suitable for anode PTL. Titanium materials have good corrosion resistance, so titanium felt (see Figure 18 ) is often used in PTL on the anode side of water electrolysis devices, but titanium felt affects the efficiency of water electrolysis devices due to its large thickness (generally greater than 300um), large fluid resistance, and random distribution of pore size.

[0224] Designed for lunar surface cathode water-inlet electrolysis cores, the titanium foil anode (PTL) and cathode (LGDL) are manufactured with titanium foil that is one-twentieth the thickness of a typical LGDL, significantly reducing the electrolysis core's ohmic resistance. Furthermore, the titanium foil anode (PTL) and cathode (LGDL) have smooth surfaces, providing a large interface contact area with the catalyst layer and bipolar plate unit 5. This significantly reduces the interfacial contact resistance between the CL / PTL / BP, thereby lowering the overall ohmic resistance of the electrolysis core.

[0225] This embodiment provides a method for preparing an anode PTL layer and a cathode LGDL layer, which is used to prepare the PTL layer in the cathode water inlet lunar surface electrolysis device described in Example 1, comprising the following steps:

[0226] S01. A titanium foil having a thickness of 15-25 microns is used as a raw material, and the surface of the titanium foil is polished to a surface roughness of 1 μm;

[0227] S02.Use etching or laser processing to evenly distribute circular holes on the titanium foil. The diameter of the circular holes is 100μm--300μm, the porosity is 0.3-0.37, the center distance between the circular holes is 100--300μm, and the diameter of the circular holes is equal to the center distance (see Figure 19 , Figure 20 );

[0228] S03. A 100nm-150nm platinum layer is plated on the surface of the processed anode PTL layer 6 and the cathode LGDL layer 8 to reduce the bulk resistance of the anode PTL layer 6 and the cathode LGDL layer 8 and the contact resistance between the anode PTL layer 6, the cathode LGDL layer 8 and the catalyst layer and the bipolar plate unit 5;

[0229] S04. Place the titanium foil processed in step S03 into a hot air heating box at 400-420°C, keep the temperature constant for 30 minutes, and then cool naturally to form a hydrophilic surface. The actual measured contact angle is 0 degrees.

[0230] Example 4:

[0231] The fundamental difference between the fourth embodiment and the third embodiment is that:

[0232] In step S02, regular hexagonal and circular holes are evenly distributed on the titanium foil by etching or laser processing (see Figure 21 ), PTL and GDL are distributed adjacently by hexagons, and each side of the central hexagon is connected to a similar hexagon; there is a ring in the middle of a single hexagon, and the radius of the inner hole of the ring is r = 0.1-0.3mm; the width of the ring is b = 0.3r-0.4r; the distance between the ring and the hexagon side is d = 0.3r-0.5r; the width of the hexagon side is h = 0.1-0.2mm; the porosity is 0.3-0.5.

[0233] By distributing a combination of regular hexagons and circles, a low resistance network is formed that is conducive to electron conduction (such as Figure 21 ); at the same time, the size of the bubbles is controlled to facilitate their discharge in the low gravity environment of the lunar surface.

[0234] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

Claims

1. A cathode water inlet lunar surface electrolysis device, characterized in that: It includes a lower end face clamping plate, a lower insulating plate is detachably fixedly mounted on the upper side of the lower end face clamping plate, a lower single-sided electrode plate is detachably fixedly mounted on the upper side of the lower insulating plate, and multiple groups of bipolar plate units are detachably fixedly mounted on the upper side of the lower single-sided electrode plate, and an LGDL layer, a membrane electrode assembly and a PTL layer are detachably fixedly mounted in sequence from bottom to top between every two groups of bipolar plate units; An upper single-sided plate is detachably fixedly mounted above the bipolar plate unit, an upper insulating plate is detachably fixedly mounted above the upper single-sided plate, an upper end surface clamping plate is detachably fixedly mounted above the upper insulating plate, and a water inlet, an oxygen outlet, a nitrogen inlet, and a hydrogen outlet are respectively mounted on the top of the upper end surface clamping plate; One side of the lower single-sided plate is provided with a positive electrode connection terminal, and one side of the upper single-sided plate is provided with a negative electrode connection terminal; The membrane electrode assembly includes a three-layer structure of anode catalyst, proton exchange membrane and cathode catalyst from bottom to top. The anode catalyst layer is connected to the PTL layer for the transmission of electrolyte and gas and the conduction of electrons and heat. The cathode catalyst layer is connected to the LGDL layer for providing a water transmission channel and a gas diffusion channel. The bipolar plate unit includes a cathode plate and an anode plate. A cathode flow field structure is provided on the side wall of the cathode plate, and an anode flow field structure is provided on the side wall of the cathode plate, which is used to promote gas-liquid transmission convection under low microgravity conditions on the lunar surface.

2. The cathode water inlet lunar surface water electrolysis device according to claim 1, characterized in that: Both sides of the lower end face splint are fixed with fixing feet by bolts, and a fixing rod is provided between the lower end face splint and the upper end face splint. The two ends of the fixing rod are tightened with nuts to install and fix the lower end face splint and the upper end face splint.

3. The cathode water inlet lunar surface water electrolysis device according to claim 2, characterized in that: The lower single-sided plate is configured as an anode plate, and the upper single-sided plate is configured as a cathode plate.

4. The cathode water inlet lunar surface water electrolysis device according to claim 3, characterized in that: Sealing rings are provided between the lower insulating plate, the lower single-sided polar plate, the two groups of bipolar plate units, the upper single-sided polar plate and the upper insulating plate.

5. The cathode water inlet lunar surface water electrolysis device according to claim 4, characterized in that: The side of the two groups of bipolar plate units facing the upper end surface clamping plate is set as the cathode plate, and the side facing the lower end surface clamping plate is set as the anode plate.

6. The cathode water inlet lunar surface electrolysis water device according to claim 5, characterized in that: The cathode flow field structure includes a cathode inlet and a cathode outlet provided at a diagonal position of the cathode plate, and two groups of flow channels are connected at a quarter arc position between the cathode inlet and the cathode outlet, each group having two flow channels, and the two groups of flow channels are arranged in a mirror-symmetrical manner as a whole; Each flow channel at the cathode inlet is arranged in a serpentine spiral manner. The planar arrangement area of ​​each flow channel constitutes a serpentine flow field partition. The four flow channels constitute four serpentine flow field partitions, and the four serpentine flow field partitions are arranged in sequence along the horizontal direction. The areas of the four serpentine flow field partitions are the same, the number of bends in the four serpentine flow field partitions remains consistent, and the four flow channels have the same length. Therefore, the inlets of the four flow channels have the same inlet velocity and pressure, and the pressure, velocity bending loss and path loss of each flow channel are the same.

7. The cathode water inlet lunar surface electrolysis water device according to claim 6, characterized in that: The anode flow field structure includes two oxygen outlets opened at the diagonal position of the anode plate, and multiple rows of parallel arrays of pins are arranged between the two oxygen outlets to form a square pin-shaped flow field. Four direct current channels are arranged between the square pin-shaped flow field and the two oxygen outlets, and the layout direction of the four direct current channels is perpendicular to the arrangement direction of the pins.

8. A method for preparing a hydrophilic Pt / Cg cathode catalyst, for preparing the cathode catalyst in the cathode water inlet lunar surface water electrolysis device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Preparation of hydrophilic Pt / Cg support: S11. Impregnation (S11.1) At room temperature, impregnate high-porosity Ketjen Black ECP-600JD with 15% polyimide (PI) resin for 5 minutes to ensure that the polyimide (PI) resin is fully impregnated into the carbon black surface and pore structure, providing a nitrogen source and a graphitized carbon source for the carbon black; (S11.2) Place the impregnated solid in a 60°C oven and dry for 180 minutes to remove the solvent. S12. Curing (S12.1) Place the dried impregnated solid in a vacuum oven. Maintain the vacuum level within 5 ps. Raise the oven temperature to 100°C at a rate of 2°C / min and hold for 30 min. (S12.2) Continue to increase the oven temperature to 380°C at a rate of 2°C / min and hold for 40 min. (S12.3) Place the impregnated solid dried in step (S12.2) in a low-temperature vacuum drying oven at -60°C, maintaining a vacuum level within 5 ps, and continue drying for 60 minutes. S13. Carbonization and Graphitization The solid dried in step (S12.3) was placed in a carbonization furnace for carbonization treatment. The temperature of the carbonization furnace was raised to 900°C at a rate of 3°C / min and kept at this temperature for 20 minutes. Then, the temperature of the carbonization furnace was further raised to 1100°C at a rate of 3°C / min and kept at this temperature for 30 minutes to carry out graphitization treatment, finally obtaining a carbonized and graphitized solid. S14. Particle size control and contact angle measurement (S14.1) The solid obtained from the carbonization and graphitization in step S13 is ground into a particle size of 0.1 mm to 0.2 mm using a mechanical grinder. The solid is then passed through an airflow mill, utilizing the autogenous grinding action of the solid and the impact of a high-speed airflow generated by compressed air, to grind into particles of 0.2 to 1 μm. (S14.2) Weighing 10 mass fractions of a 20% PTFE emulsion and 1 mass fraction of carbonized and graphitized solid abrasive particles, immersing the solid abrasive particles in the PTFE emulsion, and dispersing them using a high shear disperser and ultrasonic waves for 10 minutes to form a slurry. The slurry is then applied to the surface of TORAY T-90 carbon paper by doctor blade coating to a coating thickness of not less than 50 μm. The TORAY T-90 carbon paper is then placed in an oven and heated at 350°C for 30 minutes. After cooling to room temperature, the contact angle of deionized water on the carbon paper coating is measured, and the contact angle is determined to be 33.015 degrees, thereby obtaining a hydrophilic carrier. S15.Pt active metal support Pt nanoparticles were loaded on a hydrophilic support using an impregnation reduction method, with a Pt loading of 20%. The Pt source was chloroplatinic acid and the reducing agent was ethylene glycol. A certain proportion of sodium citrate surfactant is added to ensure that the particle size of platinum is within the range of 3-5nm; Add a certain amount of NaOH solution to create an alkaline environment with a pH value between 8 and 10 during the impregnation process to ensure that the platinum particle size is concentrated and the Pt active metal is loaded; The loaded hydrophilic Pt / Cg support was placed in a tube furnace and introduced with argon containing 2% hydrogen at a flow rate of no more than 20 SCCM. The temperature of the tube furnace was controlled between 700-800°C for 10 minutes to enhance the bonding strength between the Pt particles and the carbonized graphitized support. S2. Preparation of coating slurry for cathode catalyst layer: S21. Weigh 1 mass fraction of XC-72R carbon black, add 12 mass fractions of isopropanol and 12 mass fractions of deionized water, disperse using a high shear disperser for 8 minutes, and then cool at a low temperature of 5 ° C for 10 minutes; S22. Then take 5% perfluorosulfonic acid resin aqueous solution 8 mass fraction, added to the carbon black / isopropyl alcohol / water dispersion system, high shear for 8 minutes, so that the slurry forms a uniform and fine paste, and then cooled at a low temperature of 5 ° C for 10 minutes; S23. Add 8.5 mass fraction of Pt / Cg catalyst to the paste slurry of step S22, high shear dispersion for 5 minutes, ultrasonic dispersion for 5 minutes to form a viscous paste liquid, and then cool at a low temperature of 5 ° C for 10 minutes to obtain a coating slurry for the cathode catalyst layer; S3. Preparation of cathode catalyst layer: The coating slurry in step S23 is evenly coated on the surface of the proton exchange membrane using a slit coating method, with a coating thickness of 20 μm-25 μm, and then dried with hot air at 120° C.

9. A method for preparing an anode PTL layer and a cathode LGDL layer, for preparing the PTL layer in the cathode water inlet lunar surface water electrolysis device according to any one of claims 1 to 7, characterized in that: The following steps are involved: S01. A titanium foil having a thickness of 15-25 microns is used as a raw material, and the surface of the titanium foil is polished to a surface roughness of 1 μm; S02. By etching or laser processing, evenly distributed circular holes or through holes in a combination of regular hexagons and circles are processed on the titanium foil; S03. A 100nm--150nm platinum layer is plated on the surface of the processed anode PTL layer and the cathode LGDL layer to reduce the bulk resistance of the anode PTL layer and the cathode LGDL layer and the contact resistance between the anode PTL layer, the cathode LGDL layer and the catalyst layer and the bipolar plate; S04. Place the titanium foil processed in step S03 into a hot air heating box at 400-420°C, keep the temperature constant for 30 minutes, and then cool naturally to form a hydrophilic surface.

10. The method for preparing the anode PTL layer and the cathode LGDL layer according to claim 9, characterized in that: The specific dimensions of the processed circular holes are as follows: The diameter of the circular hole is 100μm--300μm, the porosity is 0.3-0.37, the center distance between the circular holes is 100--300μm, and the diameter of the circular hole is equal to the center distance; Processing through holes that are a combination of regular hexagons and circles is as follows: The anode PTL layer and the cathode LGDL layer are distributed adjacent to each other by multiple hexagons. Each side of the central hexagon is connected to a similar hexagon. A circular ring is nested in the middle of a single hexagon. The circular ring is connected to the three sides of the hexagon. The inner radius of the circular ring is r = 0.1-0.3mm; the width of the circular ring is b = 0.3r-0.4r; the distance between the circular ring and the hexagon side is d = 0.3r-0.5r; the width of the hexagon side is h = 0.1-0.2mm; and the porosity is 0.3-0.5.

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