A device and system for low temperature all-gaseous water vapor electrolysis of hydrogen

Abstract

The utility model relates to water electrolysis technical field, specifically disclose a kind of low-temperature full gaseous water vapor electrolytic hydrogen production device and system. The utility model aims at overcoming the limitations of existing water electrolysis technology in energy efficiency, cost, system complexity, operation flexibility and environmental adaptability etc. The utility model is core at, under the mild condition lower than 90 DEG C, water is supplied to cathode and anode of electrolytic cell in the form of pure gaseous water vapor simultaneously, using specially designed membrane electrode assembly and internal water management structure, under the action of direct current, water vapor is decomposed efficiently to generate high-purity hydrogen and oxygen. The entire electrolysis process avoids the direct input and circulation of liquid water, realizes gas-solid two-phase interface reaction, significantly simplifies water balance system, reduces equipment volume and weight, solves the bubble coverage of traditional liquid phase electrolysis, mass transfer resistance. The utility model device has the characteristics of modularization and miniaturization, and significantly reduces the net power consumption per unit hydrogen production.

Description

Technical Field

[0001] This utility model relates to the field of water electrolysis technology, specifically to a device and system for producing hydrogen by low-temperature all-gas steam electrolysis. Background Technology

[0002] Existing low-temperature water electrolysis technologies, whether alkaline or based on proton exchange membranes (PEM) or anion exchange membranes (AEM), generally use liquid water as the reactant or conductive medium. The core drawback of this approach lies in the three-phase interface between the electrode, the bubbles, and the liquid electrolyte. At this interface, the electrolyzed hydrogen and oxygen form bubbles that tend to cover the active sites of the electrode and hinder ion transport channels in the electrolyte. This "bubble covering effect" introduces a significant additional impedance (typically 50–200 mΩ cm⁻¹). 2 Even higher temperatures (such as bubbling) directly lead to an increase in electrolysis voltage, which is estimated to cause a 5-15% loss in voltage efficiency. To alleviate the bubble problem, traditional designs often require complex flow field structures or high-velocity liquid circulation systems, which undoubtedly increases the system's energy consumption, size, weight, and potential maintenance costs and failure rates.

[0003] On the other hand, while high-temperature solid oxide electrolysis (SOEC) technology avoids liquid-phase bubble problems by reacting at the gas-solid interface and can utilize thermal energy to improve efficiency, its operating temperature typically exceeds 700°C. Such high temperatures place extremely stringent requirements on the materials of the electrolytic cell (such as electrolytes, electrodes, sealing materials, and connectors), necessitating the use of expensive special ceramics and high-temperature alloys. Furthermore, the material stability, thermal shock resistance, and thermal cycling performance under long-term operation remain significant challenges. Simultaneously, heating water to high-temperature steam and maintaining the high-temperature operation of the entire system requires substantial heat input and complex thermal insulation designs, significantly increasing the system's energy consumption and cost. More importantly, high-temperature systems typically have high thermal inertia, resulting in slow start-up and shutdown processes, making them unsuitable for applications requiring rapid response and flexible start-stop capabilities, such as coupling with fluctuating renewable energy sources or portable applications.

[0004] Therefore, existing technologies face a dilemma: low-temperature liquid-phase electrolysis is hampered by bubble coverage and system complexity, while high-temperature gas-phase electrolysis is limited by materials, energy consumption, and response speed. This invention aims to provide a device and system for low-temperature, all-gaseous water vapor electrolysis to produce hydrogen, thereby resolving this core technological contradiction: how to completely eliminate dependence on liquid water under mild conditions not exceeding 90℃, innovatively using pure gaseous water vapor to simultaneously supply both the cathode and anode for water electrolysis, thus eliminating the bubble coverage effect and its resulting efficiency loss at the source. Ultimately, this results in a novel water electrolysis hydrogen production device with a minimalist structure, rapid response, ease of miniaturization and modularization, and excellent energy efficiency. Utility Model Content

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a device and system for low-temperature all-gaseous water vapor electrolysis to produce hydrogen, thereby solving this core technical contradiction: how to completely get rid of dependence on liquid water under mild conditions not exceeding 90°C, and innovatively use pure gaseous water vapor to simultaneously supply the cathode and anode for water electrolysis, thereby eliminating the bubble covering effect and the efficiency loss it causes at the source, and finally constructing a new type of water electrolysis hydrogen production device with a simple structure, fast response, easy miniaturization and modularization, and excellent energy efficiency.

[0006] The first aspect of this invention provides an apparatus for producing hydrogen by low-temperature all-gas steam electrolysis.

[0007] Specifically, including: At least one electrolysis unit, each electrolysis unit comprising a membrane electrode assembly and its support structure consisting of an ion-conducting membrane, a cathode catalyst layer, an anode catalyst layer, a gas diffusion layer, and a bipolar plate or end plate with a gas flow channel, wherein the cathode and anode catalyst layers face the spaces forming the cathode chamber and the anode chamber, respectively. A steam supply system is used to generate gaseous steam and precisely control the flow rate and humidity, delivering it to the cathode chamber inlet and anode chamber inlet of the electrolysis unit; The product export and processing system is connected to the cathode chamber outlet and the anode chamber outlet, respectively, and includes components for cooling, separating, drying and recovering unreacted water vapor, and for exporting hydrogen product gas streams and oxygen product gas streams; The power supply and control system includes a power module that provides DC power to the electrolysis unit, and a control unit for monitoring and controlling the device's operating temperature, pressure, gas flow rate, humidity, current, and voltage, and executing start-up and shutdown procedures, safety protection, and mode switching. The housing and thermal management system are used to house components, provide structural support, sealing and insulation, and include heating and / or cooling elements for maintaining the electrolysis unit within a predetermined low-temperature operating range.

[0008] Preferably, the ion-conducting membrane includes at least one of perfluorosulfonic acid type proton exchange membrane, non-perfluorosulfonic acid type proton exchange membrane, piperidinyl anion exchange membrane, and imidazole anion exchange membrane.

[0009] Preferably, the thickness of the ion-conducting membrane is 20~200 μm.

[0010] For proton exchange membrane (PEM) systems: thin perfluorosulfonic acid (PFSA) membranes, including Nafion 211 (25–30 µm thick) and Nafion® 212 (45–50 µm thick), or composite membranes reinforced with ePTFE, including Nafion N117-ePTFE (45–50 µm thick), can be used. These membranes typically achieve a thickness of 0.12 Scm at 80°C and 95% RH. -1 The above conductivity.

[0011] For anion exchange membrane (AEM) systems: novel, high-performance AEMs are required, such as modified piperidinium-based polybenzimidazole (PBI) or AEMs based on polyethersulfone or similar frameworks. These advanced AEMs need to achieve >0.1 S cm⁻¹ at 60–80 °C. -1 It has high electrical conductivity and excellent chemical stability.

[0012] Preferably, the cathode catalyst layer comprises one hydrogen evolution catalytic active material selected from platinum, palladium, ruthenium, nickel, molybdenum, and cobalt.

[0013] Preferably, the anode catalyst layer comprises one oxygen evolution catalytic active material selected from oxides, hydroxides, sulfides, and phosphides of iridium, ruthenium, platinum, nickel, iron, cobalt, and manganese.

[0014] Preferably, the hydrogen evolution catalytic active material is loaded on a conductive support or grown directly on a gas diffusion layer.

[0015] Preferably, the oxygen evolution catalytic active material is loaded on a conductive support or grown directly on a gas diffusion layer.

[0016] Preferably, the conductive carrier includes at least one of carbon materials and conductive ceramics.

[0017] Catalyst selection: Highly active Pt / C is preferred for the cathode HER side (platinum loading as low as 0.1 mg Pt cm⁻¹). -2 Alternatively, lower-cost non-precious metal catalysts (NiMo alloys) can be used.

[0018] Highly active and stable IrO2 (iridium loading 0.3 mg metal cm⁻¹) can be selected for the anode OER side. -2 (or non-precious metal-based catalysts (NiFe LDH, etc., especially in the AEM system).

[0019] Structural design: A suitable amount of binder (Nafion) needs to be uniformly dispersed in the catalyst layer. ®The solution or AEM ionomer (approximately 10–30 wt%) is used to construct a continuous ion transport network. Simultaneously, an optimized porous structure (porosity approximately 50–70 vol%) is required, preferably with hierarchical channels (cascaded pore structure) to facilitate rapid diffusion of water vapor to the catalytically active sites and to allow the generated hydrogen and oxygen to be smoothly extracted.

[0020] Preferably, the gas diffusion layer (GDL) includes a cathode-side gas diffusion layer and an anode-side gas diffusion layer. The cathode-side gas diffusion layer is made of carbon paper with good conductivity and excellent pore structure (thickness of 180~200 µm); the anode-side gas diffusion layer, due to the oxidizing environment, is made of more corrosion-resistant titanium felt or specially treated carbon material. The GDL must not only provide electronic conduction and mechanical support, but also have good gas permeability.

[0021] GDL Surface Treatment: To facilitate gas-phase operation and internal water management, the GDL surface may require special wetting treatment. The side closer to the catalyst layer can be hydrophilic to facilitate vapor adsorption and utilization of moisture from the capillary layer; while the side closer to the flow field plate can remain hydrophobic or be designed with a hydrophilic / hydrophobic gradient structure to prevent the accumulation of trace amounts of condensate that may clog the pores.

[0022] Preferably, the material of the bipolar plate (BPP) includes at least one of graphite and coated metal.

[0023] Material selection: Select materials with good electrical conductivity, corrosion resistance, and high gas tightness.

[0024] The graphite includes modified graphite or graphite-polymer composite materials; The metal coating includes 316L stainless steel or titanium alloy with a TiN or Pt corrosion-resistant conductive coating.

[0025] Flow field design: Design a flow channel structure suitable for uniform gas phase distribution and low pressure drop. A staggered comb-shaped flow field is adopted, and its channel size needs to be optimized to ensure uniform gas distribution, extremely low pressure drop (<100 Pa), and laminar flow (Reynolds number <200) at the target steam flow rate, avoiding local overheating or uneven mass transfer that may be caused by turbulence.

[0026] The second aspect of this invention provides a system for producing hydrogen by low-temperature all-gas steam electrolysis.

[0027] Specifically, including: At least one of the low-temperature all-gaseous steam electrolysis hydrogen production devices provided in the first aspect of this utility model is used as the core hydrogen production unit; An energy supply unit is used to provide the low-temperature all-gaseous steam electrolysis hydrogen production device with the electrical energy and / or thermal energy required for operation. The energy supply unit may include a grid interface, renewable energy power generation equipment, energy storage battery, and low-grade heat source interface. The hydrogen processing and storage unit is used to separate, compress, and store the hydrogen produced by the hydrogen production unit in high-pressure cylinders, cryogenic liquid hydrogen tanks, or metal hydride storage tanks. The system integration and management platform is used to coordinate the work of various units, realize intelligent energy scheduling, on-demand hydrogen production and supply, and remote monitoring and diagnosis of the system.

[0028] Preferably, the renewable energy power generation equipment includes at least one of a photovoltaic array and a wind turbine.

[0029] Preferably, the low-grade heat source interface includes at least one of a solar collector and an industrial waste heat recovery heat exchanger.

[0030] Preferably, the system is closely coupled with a renewable energy power generation device, using the fluctuating power of renewable energy to directly drive the electrolysis to produce hydrogen, and storing or utilizing the produced hydrogen as an energy carrier to improve the absorption rate of renewable energy and smooth the output.

[0031] Steam supply subsystem: Steam generator: A small, efficient unit capable of precisely controlling steam output. Preferably, a miniature stainless steel boiler (500 mL capacity) equipped with a high-efficiency heating element (such as a 1 kW spiral tube heater).

[0032] Integrated heat source: The heat source of the steam generator can be flexibly selected. In addition to conventional resistance heating, an important advantage is that it can directly utilize external low-grade heat sources. For example, through the internal heat exchange coil, industrial waste heat (hot water, low-pressure steam) at <90°C or heat energy generated by solar collectors can be used for heating and evaporation, thereby significantly reducing the net power consumption of the system.

[0033] Precision Control: To accurately control the steam flow and humidity entering both the anode and cathode, the system needs to be equipped with a high-precision mass flow controller (MFC, such as MEMS type, range 0~5 SLM, accuracy ±1%FS) and a dew point sensor (such as thin-film type, accuracy ±1℃). Through a PID closed-loop control algorithm, the heating power and / or the needle valve opening at the steam outlet are adjusted in real time to ensure that the steam parameters are stable at the set values.

[0034] Water recovery condenser: High-efficiency design: To achieve closed-loop water circulation and reduce water consumption, a high-efficiency condenser is required. A compact microchannel aluminum alloy heat exchanger can be used to efficiently condense and recover unreacted water vapor in the outlet product gas stream using ambient temperature cooling water or air.

[0035] Water circulation loop: The recovered condensate, after simple filtration, can be pumped back to the steam generator to form a closed pure water circulation loop, which greatly reduces the need for external water supply.

[0036] Thermal management and intelligent control system: Temperature maintenance: To ensure the electrolysis operates precisely within the target low-temperature range (60~85℃), auxiliary heating elements (PTC flexible heating film, power ≤150 W) need to be embedded in the end plates and other locations for cold start and temperature compensation, and temperature sensors (K-type thermocouples) need to be equipped for real-time monitoring. Simultaneously, cooling measures (cooling fans, cooling channels) also need to be integrated to cope with heat generation during high-load operation.

[0037] Integrated Control Unit: Employing a microcontroller (STM32 series) as its core, this unit integrates all sensor signals and actuator control. It runs an advanced multivariable process control (PID) algorithm to perform precise and stable closed-loop control of key parameters such as temperature, humidity (indirectly controlled via dew point), flow rate, pressure, and voltage / current, ensuring system temperature fluctuations <±2℃ and humidity fluctuations <±3%RH. The control system also integrates comprehensive safety protection logic and automatic start / stop procedures.

[0038] The method for producing hydrogen by low-temperature all-gaseous steam electrolysis specifically includes the following steps: (1) An electrolytic cell device comprising at least one electrolytic unit, wherein the electrolytic unit has a cathode chamber and an anode chamber separated by an ion-conducting membrane, wherein a cathode catalyst layer for catalyzing hydrogen evolution reaction and an anode catalyst layer for catalyzing oxygen evolution reaction are respectively disposed on both sides of the ion-conducting membrane (including a PEM membrane and an AEM membrane) to form a membrane electrode assembly; wherein the cathode chamber and the anode chamber are respectively provided with channels for introducing gaseous reactants and discharging gaseous products; (2) Gaseous water vapor is introduced into the cathode chamber and the anode chamber separately and simultaneously; (3) Maintain the operating temperature of the electrolytic cell device at 40~90℃; (4) Apply a DC potential to the membrane electrode assembly to reduce water vapor or hydrogen ions on the surface of the cathode catalyst layer to generate hydrogen gas, and to oxidize water vapor or hydroxide ions on the surface of the anode catalyst layer to generate oxygen gas. (5) A product gas stream rich in hydrogen is discharged from the cathode chamber and a product gas stream rich in oxygen is discharged from the anode chamber respectively; wherein, during the entire steady-state electrolysis process, there is no macroscopically free-flowing liquid water phase inside the cathode chamber and the anode chamber, and the supply and consumption of water are completed at the gas phase or gas-solid interface.

[0039] Preferably, in step (2), the gaseous water vapor includes saturated water vapor or slightly superheated water vapor with a superheat of less than 20°C; The relative humidity of the gaseous water vapor entering the electrolysis unit is 50-100%.

[0040] More preferably, the relative humidity of the gaseous water vapor entering the electrolysis unit is 80-100%. This ensures that the ion-conducting membrane maintains sufficient hydration and high ionic conductivity at the operating temperature.

[0041] Preferably, in step (2), the generation of gaseous water vapor includes at least one of the following methods: (a) Produced by heating liquid water to a predetermined temperature using an external heater and evaporating it under normal or reduced pressure conditions; (b) Steam generated from waste heat below 90°C produced by industrial processes; (c) Low-temperature steam generated using solar collectors or other renewable heat sources; (d) In-situ heating and evaporation of internal stored water or circulating water using heating elements integrated inside the electrolytic cell; (e) Produced by capturing moisture from the environment and heating it to evaporate.

[0042] Preferably, in step (2), gaseous water vapor is introduced into the cathode chamber and the anode chamber separately and simultaneously, and the reactant form and supply basis are as follows: Pure gaseous water vapor: Saturated or slightly superheated (superheat <20°C) water vapor is used as the sole aqueous reactant. To ensure that the membrane remains fully hydrated at the operating temperature to maintain high ionic conductivity, the relative humidity (RH) of the vapor entering the electrolysis unit must be maintained at a high level, for example, ≥80%.

[0043] Dual-sided synchronous steam supply: Unlike traditional single-sided water or moisture supply designs, this invention emphasizes injecting steam into the cathode and anode chambers of the electrolysis unit separately and simultaneously through independent flow and temperature control pipelines. This symmetrical supply method helps maintain a balance of moisture and electrochemical reaction environment on both sides of the membrane, avoiding performance degradation or local overheating / drying caused by uneven water transmission.

[0044] Preferably, in generation method (e), the environment includes air humidity.

[0045] Preferably, in step (3), the operating temperature is 60~85℃. This operating temperature is based on the following: Thermodynamic and kinetic optimization: Compared to room temperature, moderately increasing the temperature helps to lower the theoretical decomposition voltage of water and significantly accelerates electrode reaction kinetics and improves the conductivity of ion exchange membranes. For example, within this temperature range, high-performance proton exchange membranes (PEMs) or advanced anion exchange membranes (AEMs) can achieve high levels of ionic conductivity in a fully hydrated state.

[0046] Material compatibility and cost control: This temperature is below the boiling point of water at normal pressure, avoiding the complexity and cost of high-pressure systems. At the same time, this temperature range has good compatibility with existing mature high-performance polymer membranes, catalysts, gas diffusion layers, and bipolar plate materials, facilitating the use of existing supply chains and reducing costs.

[0047] Avoid high temperatures: The temperature is far below the operating temperature of high-temperature solid oxide electrolysis (SOEC), avoiding problems such as rapid material aging, thermal stress cycle damage, and slow start-up caused by high temperatures.

[0048] Preferably, in step (5), the supply and consumption of water are carried out in the gas phase or at the gas-solid interface, which is the core reaction mechanism: Gas-solid interface reaction: Under the action of an applied DC electric field, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occur directly in the gas-solid interface region formed by the catalyst layer and water vapor. Since there is no macroscopically free-flowing liquid water in the reaction chamber, the problems of bubble generation, adhesion, and coverage in liquid phase electrolysis are fundamentally eliminated.

[0049] Mass transfer advantages: The diffusion of gaseous reactants (water vapor) and products (hydrogen, oxygen) is smoother, especially at high current densities. The mass transfer resistance is much smaller than that of liquid phase electrolysis, which is conducive to achieving higher limiting current density and energy efficiency.

[0050] Preferably, the method further includes water management; The water management includes the following steps: (1) Monitor the dew point or relative humidity of the outlet gas of the cathode and anode in real time, and adjust the supply rate of water vapor or heating power through feedback control to dynamically maintain the water content in the membrane; (2) Cool the output product gas stream, condense and recover unreacted water vapor, and send the recovered condensate back to the water vapor generation unit or water storage unit to realize the closed-loop recycling of water.

[0051] Preferably, the water management is used to precisely control the flow rate and humidity of water vapor entering the cathode and anode chambers, and to maintain the moisture balance inside the membrane electrode assembly.

[0052] Water recovery and closed-loop circulation: The output product gas stream (at least on the anode side, or on both sides as needed) is cooled by a downstream condenser, causing unreacted water vapor to condense into liquid water. The recovered condensate can be sent back to the steam generation unit, achieving closed-loop water recycling and reducing the system's total water consumption.

[0053] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) Significantly improved performance and energy efficiency: By eliminating bubble coverage, optimizing gas-phase mass transfer, and utilizing the advantages of low-temperature thermodynamics / kinetics, the electrolysis voltage is significantly reduced, and the limiting current density is increased. Combined with the direct utilization of low-grade heat energy (<90℃), extremely low net power consumption (≤3.8 kWh / Nm³) can be achieved. 3 It has significant energy-saving effects (saving more than 13% of electricity compared to conventional PEM).

[0054] (2) High efficiency dynamic response and operational flexibility: The low heat capacity of the all-gas state brings extremely fast start-up and shutdown speed (minute-level cold start), which can efficiently adapt to fluctuating renewable energy.

[0055] (3) Compactness, portability and environmental adaptability: High power density and lightweight design make it highly compact and portable. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the overall structure of the low-temperature all-gas steam electrolysis hydrogen production device (single module) in Example 1; Figure 2 This is a graph showing the relationship between unit hydrogen energy consumption (electricity consumption) and current density of the device in Example 1 under typical operating conditions; Figure 3 This is a graph showing the relationship between unit hydrogen energy consumption (electricity consumption) and current density of the device in Example 2 under typical operating conditions. Detailed Implementation

[0057] To enable those skilled in the art to more clearly understand the technical solution described in this utility model, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this utility model.

[0058] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods. Figure 1 The purpose is to demonstrate the main components of the device (such as the electrolysis unit, steam supply system, product extraction and processing system, control system, thermal management system, etc.) and its overall structure. Figure 2The purpose is to visually evaluate the performance and potential advantages of the device in terms of electrochemical properties (such as overpotential and ohmic resistance) by comparing the energy consumption of the device under similar conditions with that of a conventional PEM. Figure 3 The purpose is to visually evaluate the performance and potential advantages of the device in terms of electrochemical performance (overpotential, ohmic resistance) by comparing the energy consumption of the device with that of a traditional AEM under similar conditions.

[0059] Example 1 Low-temperature all-gas steam electrolysis hydrogen production device based on proton exchange membrane (PEM) and its testing.

[0060] This embodiment aims to describe in detail the specific structure, manufacturing method, operating parameters, and performance of a low-temperature all-gas steam electrolysis hydrogen production device that uses a proton exchange membrane (PEM) as an ion conductor.

[0061] Membrane electrode assembly (MEA) fabrication: Nafion manufactured by DuPont was selected. ® Type 212 proton exchange membrane (50 μm thick) was used as the base membrane material. The membrane was first pretreated by immersing it in 3% H2O2 solution at 80℃, deionized water at 80℃, 0.5 M H2SO4 solution at 80℃ and deionized water at 80℃ for 1 hour each to remove impurities and to fully protonate and hydrate it.

[0062] Preparation of catalyst slurry: Cathode (HER) catalyst slurry: A commercially available high specific surface area carbon-supported platinum catalyst (Johnson MattheyHispec® 4000, 40 wt% Pt / C) is combined with an appropriate amount of Nafion. ® An ionomer solution (DE2020, EW 1100, 20 wt% solids content) and a certain proportion of isopropanol / water mixed solvent were uniformly dispersed in an ultrasonic bath to form a Nafion product with a solids content of approximately 15 wt%. ® A stable slurry with an ionomer to carbon carrier mass ratio (I / C ratio) of 0.8.

[0063] Anode (OER) catalyst slurry: Combining commercially available iridium oxide catalyst (Alfa Aesar, IrO2, 99.9%) with Nafion ® Ink was prepared using ionomer solutions and mixed solvents in a similar manner, with a solid content of approximately 20 wt% and an I / C ratio of 0.6.

[0064] Catalyst Coating: Using automated ultrasonic spraying technology, the prepared anion and anolyte catalyst inks are uniformly sprayed onto the pretreated Nafion catalyst. ®Both sides of the 212 film. Spraying parameters (such as spray count, spray rate, substrate temperature, etc.) were controlled to achieve a cathode platinum loading of 0.4 mg Pt / cm². 2 The iridium loading at the anode reached 1.5 mg Ir / cm³. 2 After spraying, dry in an 80°C vacuum oven for 2 hours to form a catalyst coating film (CCM).

[0065] MEA Assembly: The prepared CCM is placed between two gas diffusion layers (GDLs). The cathode GDL is carbon paper (TGP-H-060, hydrophobically treated with PTFE, approximately 190 μm thick) from Toray Industries, Japan; the anode GDL is carbon paper (Sigracet) from SGL Industries, Germany. ® 29 BC (with a microporous MPL layer, approximately 235 μm thick). After aligning the GDL and CCM, the catalyst layer was hot-pressed at 135°C and 1.5 MPa for 3 minutes to ensure good bonding between the catalyst layer and the GDL, forming a complete MEA. The effective active area of ​​the MEA prepared in this example is 10 cm². 2 .

[0066] Electrolytic reactor assembly: Five MEA units prepared above were stacked in series via graphite and titanium bipolar plates (BPPs). The flow channels were designed to uniformly distribute water vapor and exhaust product gases.

[0067] Place a sealing gasket (silicone rubber or polytetrafluoroethylene ePTFE) between the MEA and the bipolar plate to ensure a gas seal.

[0068] Five cells and bipolar plates are held together by two thickened graphite end plates (with current collector and gas inlet / outlet interfaces), and a uniform compressive force (approximately 1.0 MPa) is applied through an insulated tie rod and spring loading system to assemble a 5-cell fuel cell stack. Temperature sensors (K-type thermocouples) and voltage measurement leads are integrated on the end plates to monitor the stack temperature and the voltage of each individual cell.

[0069] Steam supply: Water storage tank: A 1-liter 316L stainless steel pressure vessel equipped with a level sensor, safety valve, and water inlet. High-purity deionized water (resistivity > 18.2 MΩ·cm) is used as the water source.

[0070] Heating and vaporization unit: A 500W flexible electric heating strip is wound around the outer wall of the bottom of the water tank, and the water temperature is precisely controlled by a PID controller. A steam outlet is located at the top of the tank, connected to a small steam-water separator, and then the steam is split into two streams through stainless steel pipelines to the cathode and anode inlets of the fuel cell stack. Needle valves and mass flow controllers (MFCs) are installed on the pipelines to precisely regulate the steam flow into both sides. The entire water tank and steam pipelines are covered with insulation to reduce heat loss.

[0071] Carrier gas unit: Provides nitrogen and compressed air as carrier gases. Nitrogen is used as the cathode carrier gas, while either nitrogen or compressed air can be used as the anode carrier gas. Under stable steam supply conditions, the carrier gas ensures that the hydrogen or oxygen concentration in the system does not become too high, maintaining the system's safety and stability. This unit works in conjunction with the steam supply system during operation to ensure precise flow regulation of both, preventing system instability.

[0072] Product export and processing: Hydrogen and oxygen outlets: These are drawn from the cathode and anode outlets of the fuel cell stack, respectively.

[0073] Condensation and Recovery Unit: After oxygen flows out, it passes through a small shell-and-tube heat exchanger (cooling medium is ambient air or circulating cooling water) to reduce the gas temperature to approximately 25°C. Most of the water vapor condenses into liquid water here, which is collected through a steam trap and then pumped back to the storage tank by a peristaltic pump, forming a closed-loop water circulation. Hydrogen flows out without cooling and directly enters the gas separation unit.

[0074] Gas separation unit: The outflowing hydrogen gas (mixed with nitrogen and water vapor) passes through the gas separation unit. After the hydrogen is enriched, the nitrogen and water vapor are returned to the water vapor supply system, realizing the recovery and utilization of raw materials and energy.

[0075] Drying Unit: The enriched hydrogen gas undergoes deep drying in a drying unit equipped with molecular sieves, outputting high-purity dry hydrogen gas that meets the requirements for fuel cell use. The oxygen side does not require deep drying and can be directly discharged after condensation.

[0076] Gas analysis and metering: Gas flow meters and online purity analyzers are installed at the final hydrogen and oxygen outlets to monitor gas production rate and purity.

[0077] Power supply and control: Power supply module: It adopts a programmable DC power supply with a maximum output voltage of 20 V and a maximum current of 200 A. It has multiple working modes such as constant current, constant voltage, and constant power, and can record real-time voltage and current data.

[0078] Control Unit: Using a PLC or embedded microcontroller, it connects to all sensors (temperature, pressure, liquid level, flow rate, humidity, gas concentration, etc.) and actuators (heating belt, MFC, valves, pumps, power supply, etc.). It runs a preset control program to achieve automatic system start / stop, temperature control (PID adjustment of heating power), steam flow control (adjusting MFC opening based on current feedback), humidity management, safety interlock protection (such as single battery voltage over-limit, temperature over-limit, hydrogen leak alarms, etc.), and data recording and display.

[0079] Operation and performance testing: Startup program: 1. Check the water level in the storage tank to ensure sufficient water supply.

[0080] 2. Start the control system and set the target operating temperature (80℃) and initial steam flow rate (e.g., 0.5 slpm for both anode and cathode, standard liters / minute).

[0081] 3. Turn on the water tank heater and fuel cell auxiliary heater to heat the water and fuel cell to the target temperature. At the same time, turn on the condenser for cooling.

[0082] 4. Once the temperature reaches the set value, open the steam supply valve to introduce steam into the anode and cathode of the fuel cell stack for preheating and humidification. Monitor the outlet gas humidity and the open-circuit voltage (OCV) of the fuel cell stack. Wait until the OCV stabilizes (indicating that the membrane is fully hydrated) and the outlet humidity is close to saturation. This process takes approximately 5-10 minutes.

[0083] 5. Turn on the DC power supply with a small current (0.1 A / cm). 2 Electrolysis begins. The voltage of each individual cell is monitored to ensure it is normal.

[0084] 6. Gradually increase the current to the target operating point (1.0 A / cm). 2 At the same time, adjust the steam flow rate according to the current (calculate the theoretical water consumption according to Faraday's law, and maintain a slightly excessive steam supply, which is 1.2 to 1.5 times the stoichiometric ratio).

[0085] 7. The system enters a stable operating state and continuously monitors various parameters.

[0086] Example 2 Low-temperature all-gas steam electrolysis hydrogen production device and testing based on anion exchange membrane (AEM).

[0087] This embodiment provides a low-temperature all-gas-state water vapor electrolysis device based on anion exchange membrane (AEM), aiming to verify the applicability of this invention to AEM systems and non-precious metal catalysts.

[0088] The main differences from Example 1: Ion exchange membrane: Replace the Nafion 212 proton exchange membrane with a Sustainion X37-50 anion exchange membrane. Before use, this membrane was prepared at 1 mol / L... -1 Activation is achieved by treating with KOH solution for 24 hours.

[0089] catalyst: Cathode (HER) catalyst: replaced with 2.0 mg cm⁻¹ -2 Nickel-molybdenum (Ni-Mo) alloy powder.

[0090] Anode (OER) catalyst: replaced with 3.0 mg cm⁻¹ -2 Nickel-iron layered double hydroxide (NiFe-LDH).

[0091] Anode-side components: Considering the alkaline environment of the AEM system, the anode bipolar plate and gas diffusion layer are replaced with materials with better alkali resistance, such as nickel-plated stainless steel plates and nickel mesh.

[0092] Other conditions: Except for the above modifications, the other components of the device (such as steam supply, product processing, power control, thermal management system) and MEA preparation, stack assembly, operation and testing methods are the same as in Example 1.

[0093] Comparative Example 1 Traditional liquid-phase PEM electrolysis.

[0094] To compare the advantages of this utility model, a PEM electrolysis comparative example using a traditional liquid water supply method was set up.

[0095] The difference from Example 1 is as follows: Liquid water supply is used, and a gas-liquid separation device is subsequently installed. Other conditions are the same as in Example 1.

[0096] Comparative Example 2 Traditional liquid-phase AEM electrolysis.

[0097] A comparison was set up using traditional liquid water or low-concentration alkali solution supply methods for AEM electrolysis.

[0098] The difference from Example 2 is as follows: Liquid water supply is used, and a gas-liquid separation device is subsequently installed. Other conditions are the same as in Example 2.

[0099] Performance comparison: This section aims to demonstrate more intuitively the advantages of the "low-temperature all-gas steam electrolysis" technology of this utility model in terms of key performance indicators by comparing Example 1 (PEM of this utility model), Example 2 (AEM of this utility model) with the corresponding traditional liquid phase electrolysis technologies (Comparative Example 1 and Comparative Example 2).

[0100] Table 1 Performance comparison results of Examples 1-2 and Comparative Examples 1-2

[0101] The preferred embodiments of this utility model have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this utility model without creative effort. Therefore, any technical solutions obtained by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concept of this utility model and on the existing technology, including modifications, equivalent substitutions, and improvements, should be within the scope of protection defined by the claims.

Claims

1. A device for producing hydrogen by low-temperature all-gaseous steam electrolysis, characterized in that, include: At least one electrolysis unit, each electrolysis unit comprising a membrane electrode assembly and its support structure consisting of an ion-conducting membrane, a cathode catalyst layer, an anode catalyst layer, a gas diffusion layer, and a bipolar plate or end plate with a gas flow channel, wherein the cathode and anode catalyst layers face the spaces forming the cathode chamber and the anode chamber, respectively. A steam supply system is used to generate gaseous steam and precisely control the flow rate and humidity, delivering it to the cathode chamber inlet and anode chamber inlet of the electrolysis unit; The product export and processing system is connected to the cathode chamber outlet and the anode chamber outlet, respectively, and includes components for cooling, separating, drying and recovering unreacted water vapor, and for exporting hydrogen product gas streams and oxygen product gas streams; The power supply and control system includes a power module that provides DC power to the electrolysis unit, and a control unit for monitoring and controlling the device's operating temperature, pressure, gas flow rate, humidity, current, and voltage, and executing start-up and shutdown procedures, safety protection, and mode switching. The housing and thermal management system are used to house components, provide structural support, sealing and insulation, and include heating and / or cooling elements for maintaining the electrolysis unit within a predetermined low-temperature operating range.

2. The apparatus according to claim 1, characterized in that, The ion-conducting membrane includes at least one of perfluorosulfonic acid type proton exchange membrane, non-perfluorosulfonic acid type proton exchange membrane, piperidinyl anion exchange membrane, and imidazole type anion exchange membrane.

3. A system for producing hydrogen by low-temperature all-gaseous steam electrolysis, characterized in that, include: At least one of the devices for low-temperature all-gaseous steam electrolysis hydrogen production according to any one of claims 1 to 2 is used as the core hydrogen production unit; An energy supply unit is used to provide the low-temperature all-gaseous steam electrolysis hydrogen production device with the electrical energy and / or thermal energy required for operation. The energy supply unit may include a grid interface, renewable energy power generation equipment, energy storage battery, and low-grade heat source interface. The hydrogen processing and storage unit is used to separate, compress, and store the hydrogen produced by the hydrogen production unit in high-pressure cylinders, cryogenic liquid hydrogen tanks, or metal hydride storage tanks. The system integration and management platform is used to coordinate the work of various units, realize intelligent energy scheduling, on-demand hydrogen production and supply, and remote monitoring and diagnosis of the system.

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