A composite wetting pyroelectric film high-frequency cold-heat cycle in-situ catalytic hydrogen production system and method

Abstract

This invention provides a high-frequency cold-heat cycle in-situ catalytic hydrogen production system and method using a composite wettable pyroelectric membrane, comprising a first cold water pump, a second cold water pump, a pressure chamber, an oscillating jet array, an impact chamber, a pyroelectric membrane, a pyroelectric micropillar array, and a gas outlet. A hot fluid exchanges heat with the pyroelectric membrane. Cold water, driven by the first cold water pump, flows through a first three-way valve into the pressure chamber, passes through the oscillating jet array to form an oscillating jet, enters the impact chamber, and impacts the pyroelectric membrane. A pyroelectric micropillar array with composite wettability is constructed on the surface of the pyroelectric membrane, forming a pyroelectric reaction interface. Under the alternating action of the oscillating jet and the heat exchanger, a pyroelectric effect occurs at the pyroelectric reaction interface to produce hydrogen gas, which is collected through the gas outlet. This invention efficiently and controllably converts low-grade waste heat into transient temperature changes in the pyroelectric material, thereby improving the efficiency of the interfacial hydrogen production reaction.

Description

Technical Field

[0001] This invention relates to the field of low-grade thermal energy utilization, specifically to a high-frequency cold and hot cycle in-situ catalytic hydrogen production system and method using composite wettable pyroelectric membranes. Background Technology

[0002] Industrial organic wastewater is widely generated in production processes such as printing and dyeing, papermaking, and coking. Its discharge temperature typically reaches 60-90°C, representing a low-grade waste heat resource that is currently not effectively recovered in industrial production. Currently, using heat pump technology to upgrade the heat energy grade of wastewater for heating is the main method of wastewater waste heat utilization. However, this method suffers from limitations in heat energy absorption and water quality incompatibility, resulting in a wastewater heat energy utilization rate of less than 40%.

[0003] Pyroelectric catalysis can convert the waste heat of low-grade wastewater into the chemical energy of polarized charges for water splitting to produce hydrogen, thus deeply converting the waste heat of low-grade wastewater into high-quality hydrogen energy. However, the "thermal energy-hydrogen energy" conversion efficiency and hydrogen production rate of pyroelectric hydrogen production are still relatively low. Furthermore, the presence of a high-heat-capacity liquid film on the pyroelectric surface severely weakens the dT / dτ of the pyroelectric film. The low wetting contact between the liquid film and the pyroelectric interface, along with the trapped hydrogen, significantly increases the thermal resistance and reduces the effective pyroelectric hydrogen production reaction area, severely reducing the hydrogen production rate and becoming a key bottleneck restricting its engineering application. Existing research mostly uses pyroelectric nanoparticle suspension reactors, achieving particle temperature fluctuations and driving hydrogen production through overall heating / cooling. Although this system verifies the feasibility of pyroelectric hydrogen production, because the reaction medium is mainly a high-heat-capacity liquid phase, the input heat is mainly consumed in the bulk liquid temperature rise, and the energy truly acting on the transient temperature change of the pyroelectric material is extremely low. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-frequency thermal cycling in-situ catalytic hydrogen production system and method using composite wettable pyroelectric membranes, which efficiently and controllably converts low-grade waste heat into transient temperature changes in pyroelectric materials to improve the efficiency of interfacial hydrogen production reactions.

[0005] The present invention achieves its objective through the following means:

[0006] A high-frequency cold and hot cycle in-situ catalytic hydrogen production system with a composite wettable pyroelectric membrane includes a first cold water pump, a second cold water pump, a pressure chamber, an oscillating jet array, an impact chamber, a pyroelectric membrane, a pyroelectric micropillar array, and a gas outlet.

[0007] The hot fluid exchanges heat with the pyroelectric membrane;

[0008] Driven by the first cold water pump, cold water flows into the pressure chamber after passing through the first three-way valve. After passing through the oscillating jet array, it forms an oscillating jet that enters the impact chamber and impacts the pyroelectric diaphragm.

[0009] The surface of the pyroelectric membrane is constructed with a pyroelectric micropillar array having composite wettability. The pyroelectric micropillar array forms a pyroelectric reaction interface. Under the alternating action of the oscillating jet and the heat exchanger, a pyroelectric effect occurs at the pyroelectric reaction interface to generate hydrogen gas. The hydrogen gas is collected through the gas outlet.

[0010] After the reaction is complete, the cold water is driven by the second cold water pump, flows through the second three-way valve and can circulate to participate in the reaction, or flow out from the cold water outlet.

[0011] In the above scheme, the oscillating jet array includes multiple jet oscillator units; the multiple jet oscillator units are disposed on the wall surface of the pressure chamber;

[0012] The single jet oscillator unit is provided with a connected oscillator inlet, a guide section, a mixing chamber, and an oscillator outlet in sequence; the oscillator inlet and the oscillator outlet are both conical, the wide opening of the oscillator inlet faces outward, the narrow opening is connected to one end of the guide section, the other end of the guide section is connected to one end of the mixing chamber, the diameter of the guide section is smaller than that of the mixing chamber, the wide opening of the oscillator outlet faces outward, and the narrow opening is connected to the other end of the mixing chamber; a signal water intake nozzle is provided on one side of the mixing chamber, and a signal water inlet nozzle is provided on the other side.

[0013] Furthermore, the width of the oscillator inlet of the single jet oscillator unit is 20mm, the lateral length of the guide section is 10mm, the longitudinal length is 10mm, the lateral length of the mixing chamber is 55mm, the longitudinal length of the mixing chamber is 35mm, the height is 5mm, the diameter of the signal water intake nozzle and the signal water inlet nozzle is 5mm, and the offset rate is 0.35.

[0014] Furthermore, the ratio of the impact spacing Zn to the flow characteristic length d of the jet oscillator unit is defined as the impact spacing ratio. The flow characteristic length d is the lateral length of the mixing chamber of the jet oscillator unit, and the impact spacing Zn is the distance from the outlet of the jet oscillator unit to the impact target surface, i.e., the pyroelectric film. When the impact spacing ratio is 3, the impact spacing Zn is 165 mm and the flow characteristic length d is 55 mm.

[0015] Furthermore, the jet oscillator unit is a frequency-adjustable oscillating jet element, with a signal water inlet embedded in one side of the mixing chamber, used to intermittently introduce signal water from the main jet and periodically induce jet deflection or back-cutting.

[0016] The oscillation frequency of the adjustable frequency oscillating jet element is inversely proportional to the length of the signal water pipe. The jet sweeping period is set to be greater than the unsteady thermal response time constant τ of the pyroelectric film, so that the inside of the pyroelectric film always maintains an unsteady temperature change, i.e., dT / dt≠0.

[0017] In the above scheme, the pyroelectric reaction interface is formed by an array of pyroelectric micropillars constructed on a substrate;

[0018] The pyroelectric micropillar array has a hybrid wettable micro-nano composite surface, wherein the top of the micropillar is a pyroelectric hydrophilic surface, which is used to enhance the cooling reaction; the sides and bottom of the micropillar are superhydrophobic surfaces, which are used to form a gas film thermal resistance for heat preservation.

[0019] Furthermore, the substrate is stainless steel, and the pyroelectric membrane is made of lithium tantalate;

[0020] The pyroelectric micropillar array is constructed using the following method:

[0021] First, a micro-pillar array is ablated on the stainless steel surface using femtosecond laser processing technology. During the laser processing, a nanoscale laser-induced periodic surface structure is simultaneously induced to form on the surface.

[0022] Then, the top of the micropillar is protected by a mask method, and the sides and bottom of the micropillar are modified with fluorosilane self-assembled molecular films to reduce the surface energy and construct superhydrophobic properties.

[0023] Finally, after removing the mask, a lithium tantalate film was deposited on the top of the micropillars using magnetron sputtering to form a pyroelectric hydrophilic surface.

[0024] In the above scheme, the micropillar cross-sectional size of the pyroelectric micropillar array is 10-100μm, the pillar height is 20-200μm, the pillar spacing is 20-200μm, and the area fraction is 0.2-0.8.

[0025] In the above scheme, the second cold water pump is used to control the thickness and lateral flow velocity of the liquid in the impact chamber, so as to adjust the heat exchange efficiency and the pressure inside the chamber.

[0026] A method for producing hydrogen using the aforementioned composite wettable pyroelectric membrane high-frequency thermal cycling in-situ catalytic hydrogen production system includes the following steps:

[0027] Step S1: When the source of the heat fluid is industrial low-temperature wastewater, the heat fluid is driven by a heat fluid pump and flows through a heat exchanger to exchange heat with the pyroelectric membrane. When the source of the heat fluid is the heat collected by the photothermal coating or the heat generated by electronic components, the photothermal coating or electronic components are attached to the bottom of the pressure chamber so that they exchange heat with the pyroelectric membrane and the pyroelectric membrane is heated.

[0028] Step S2: Cold water is driven by the first cold water pump and flows into the pressure chamber to be pressurized. Then, it is transformed into a periodic oscillating jet with a certain frequency by the oscillating jet array and sprayed into the impact chamber to perform high-frequency periodic cooling on the pyroelectric diaphragm.

[0029] Step S3: At the interface between the pyroelectric micropillar array and the liquid, a pyroelectric effect occurs, generating polarized charges that react with H⁺ to produce hydrogen gas. The hydrogen gas is collected through the gas outlet, and the liquid after the reaction is pumped out by the second cold water pump.

[0030] Step S4: Depending on the source of the cold water, control the second three-way valve to allow the cold water after the reaction to be recycled or discharged through the cold water outlet.

[0031] Step S5: Evaluate the hydrogen production rate by controlling the thickness and lateral flow velocity of the liquid in the impact chamber through controlling the impact spacing Zn and the second cold water pump to optimize the reaction conditions.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] This invention drives a spatiotemporally non-uniform temperature change rate distribution on a pyroelectric surface through high-frequency periodic sweeping of cooling water, thereby increasing the surface pyroelectric charge generation rate and enhancing the interfacial hydrogen production reaction. Compared with overall temperature control methods, this method concentrates heat on the heating and cooling of the pyroelectric catalytic interface. This invention constructs a pyroelectric micropillar array with composite wettability on the surface of the pyroelectric film. Specifically, the top of the micropillars is designed as a pyroelectric hydrophilic surface to enhance cooling and reaction, while the nanowire structures on the sides and bottom of the micropillars are designed as superhydrophobic surfaces to form a gas film thermal resistance for insulation. This concentrates heat on the pyroelectric active region and creates a larger local dT / dt, improving the energy conversion efficiency of the pyroelectric interfacial hydrogen production system. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a high-frequency cold and hot cycle in-situ catalytic hydrogen production system based on a composite wettable pyroelectric membrane according to an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of another embodiment of the pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system of the present invention;

[0036] Figure 3 This is a schematic diagram of the structure of a frequency-tunable oscillating jet element according to an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of a hybrid wettability micro / nano composite surface of a pyroelectric micropillar array according to an embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram of a pyroelectric micropillar array according to an embodiment of the present invention.

[0039] In the diagram: 1. Cold water; 2. First three-way valve; 3. First cold water pump; 4. Second cold water pump; 5. Second three-way valve; 6. Cold water outlet; 7. Hot fluid; 8. Pressure chamber; 9. Oscillating jet array; 10. Oscillating jet; 11. Impact chamber; 12. Pyroelectric diaphragm; 13. Pyroelectric micropillar array; 14. Hydrogen; 15. Gas outlet; 16. Hot fluid pump; 17. Heat exchanger; 18. Hot flow outlet; 901. Oscillator inlet; 902. Guide section; 903. Mixing chamber; 904. Signal water inlet; 905. Oscillator outlet; 906. Attachment point; 907. Signal water inlet; 1301. Cylindrical microstructure array; 1302. Hydrophilic pyroelectric material; 1303. Hydrophobic nanowires; 1304. Hydrophobic groove channel; 1305. Cylindrical microstructure. Detailed Implementation

[0040] The embodiments of the present invention are described in detail below.

[0041] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0042] Figure 1The diagram illustrates a preferred embodiment of the composite wettable pyroelectric membrane high-frequency cold-heat cycle in-situ catalytic hydrogen production system of the present invention. The system includes a first cold water pump 3, a second cold water pump 4, a pressure chamber 8, an oscillating jet array 9, an impact chamber 11, a pyroelectric membrane 12, a pyroelectric micro-pillar array 13, and a gas outlet 15. The source of the heat fluid 7 is industrial low-temperature waste heat wastewater, heat collected by a photothermal coating, or heat generated by electronic components. When the source of the heat fluid 7 is industrial low-temperature waste heat wastewater, the heat fluid 7 is driven by the heat fluid pump 16, flows through the heat exchanger 17 to exchange heat with the pyroelectric membrane 12, and then flows out from the heat outlet 18. The cold water 1 is cooled by the first cold water pump 3, a second cold water pump 4, a pressure chamber 8, an oscillating jet array 9, an impact chamber 11, a pyroelectric membrane 12, a pyroelectric micro-pillar array 13, and a gas outlet 15. Driven by pump 3, the water flows into the pressure chamber 8 after passing through the first three-way valve 2. After passing through the oscillating jet array 9, it forms an oscillating jet 10 that enters the impact chamber 11 and impacts the pyroelectric diaphragm 12. The surface of the pyroelectric diaphragm 12 is constructed with a pyroelectric micropillar array 13 having composite wettability. The pyroelectric micropillar array 13 forms a pyroelectric reaction interface, and under the alternating action of the oscillating jet 10 and the heat exchanger 17, a high-frequency hot and cold cycle is formed on the surface. A pyroelectric effect occurs at the pyroelectric reaction interface to generate hydrogen gas 14, which is collected through the gas outlet 15. After the reaction is completed, the cold water is driven by the second cold water pump 4 and flows through the second three-way valve 5. It can either participate in the reaction again or flow out through the cold water outlet 6. The oscillating jet array 9 includes multiple jet oscillator units, which are disposed on the wall of the pressure chamber 8.

[0043] like Figure 3 As shown, the single jet oscillator unit is sequentially provided with an oscillator inlet 901, a guide section 902, a mixing chamber 903, and an oscillator outlet 905. Both the oscillator inlet 901 and the oscillator outlet 905 are conical. The wide opening of the oscillator inlet 901 faces outward, and the narrow opening is connected to one end of the guide section 902. The other end of the guide section 902 is connected to one end of the mixing chamber 903. The diameter of the guide section 902 is smaller than that of the mixing chamber 903. The wide opening of the oscillator outlet 905 faces outward, and the narrow opening is connected to the other end of the mixing chamber 903. A signal water intake nozzle 904 is provided on one side of the mixing chamber 903, and a signal water inlet nozzle 907 is provided on the other side.

[0044] Driven by the first cold water pump, the water flows through the first three-way valve 2 and into the pressure chamber 8 for pressurization. Then, through the action of the oscillating jet array 9, the stable inflow is transformed into a periodically oscillating jet with a specific frequency, which is ejected from the oscillator outlet 905 into the impact chamber 11. The bottom of the impact chamber 11 is coated with a pyroelectric film 12. After being heated by the heat exchanger 17, the surface temperature of the pyroelectric film 12 increases. Upon being subjected to the high-frequency periodically oscillating jet formed by the cold water 1, a high-frequency hot-cold cycle occurs on its surface. The pyroelectric film 12 generates polarized charges and H+ at the liquid interface due to the pyroelectric effect.+ The reaction produces hydrogen gas, which is collected and stored for reuse through the gas outlet. The liquid is pumped out by the second cold water pump after the reaction. If the cold water source is river water or lake water, it is discharged directly through the cold water outlet 6. If the source is cooling tower cooling water, it can be recycled through the second three-way valve and the first three-way valve.

[0045] In one specific embodiment of the present invention, the oscillating jet array is made of stainless steel or acrylic material, the number of jet oscillator units is 3×4, and the arrangement is horizontal. The width of the oscillator inlet 901 of a single jet oscillator unit is 20mm, the lateral length of the guide section 902 is 10mm, the longitudinal length is 10mm, the lateral length of the mixing chamber 903 is 55mm, the longitudinal length of the mixing chamber 903 is 35mm, and the height is 5mm. The diameter of the signal water intake nozzle 904 and the signal water inlet nozzle 907 is 5mm, and the offset rate is 0.35. A single jet oscillating unit can generate an effective oscillating jet within a range of 5*50mm. Multiple oscillating jets are combined to form an oscillating jet array according to the actual required range.

[0046] The ratio of the impact spacing Zn to the flow characteristic length d of the jet oscillator unit is defined as the impact spacing ratio. The flow characteristic length d is the lateral length of the mixing chamber of the jet oscillator unit, and the impact spacing Zn is the distance from the outlet of the jet oscillator unit to the impact target surface, i.e., the pyroelectric film 12.

[0047] Preferably, the impact spacing ratio is 3, where the impact spacing Zn is 165 mm and the flow characteristic length d is 55 mm. CFD simulations were performed for Zn / d ratios of 1, 2, and 3. The results show that when the impact spacing ratio is 3, the overall temperature non-uniformity of the pyroelectric membrane is the greatest, and the lateral flow velocity of the liquid is not very high near the outlet. This avoids the downstream oscillating jet obtaining more mass flow at the inlet, causing its surface temperature to tend to a steady state. This allows for high-frequency thermal cycling across the surface of the pyroelectric membrane, resulting in the highest hydrogen production efficiency. In this case, Zn is 165 mm and d is 55 mm.

[0048] The jet oscillator unit is a frequency-tunable oscillating jet element, enabling active control of the sweeping frequency and jet flow rate. A signal water inlet 904 is embedded on one side of the mixing chamber 903, used to intermittently introduce signal water from the main jet and periodically induce jet deflection or backflow. The oscillation frequency of the frequency-tunable oscillating jet element is inversely proportional to the length of the signal water pipe and is unaffected by the jet flow rate. Based on the equivalent heat capacity and thermal resistance of the "liquid film-pyroelectric thin film-substrate" structure, a Fourier number quantitative analysis is performed. The jet sweeping period is set to be greater than the unsteady-state thermal response time constant τ of the pyroelectric thin film, ensuring that the pyroelectric thin film maintains an unsteady temperature change (dT / dt≠0), thereby continuously generating pyroelectric charges to drive interfacial reactions.

[0049] The heat source is a continuous heat flow, such as industrial low-temperature waste heat water. Driven by a heat fluid pump, it exchanges heat with a pyroelectric diaphragm through a heat exchanger, ensuring the pyroelectric diaphragm is at a high temperature before heat exchange with the oscillating jet. Cold water, driven by a first cold water pump, flows through a three-way valve into the pressure chamber, ensuring all jet oscillator units have the same inlet pressure. After passing through the oscillating jet array, the fluid's viscosity causes a wall adhesion effect, forming an oscillating jet that enters the impact chamber and impacts the pyroelectric diaphragm. The higher-temperature pyroelectric diaphragm experiences a surface temperature change upon encountering the cold flow. Since heat exchange occurs at the surface, during the oscillating jet cycle, the portion not impacted by the oscillating jet quickly returns to its previous temperature. During this process, the pyroelectric diaphragm with the pyroelectric coefficient responds to the rate of temperature change dT / dt, generating a pyroelectric current on its surface. In a neutral liquid, the polarization charge q- generated by the pyroelectric particles interacts with H-. + The reaction produces H2. Hydrogen gas is collected through the gas outlet. The water from the completed reaction is pumped out by a second cooling water pump. This second cooling water pump can control the thickness and lateral flow velocity of the liquid in the impact chamber, thereby controlling the heat exchange efficiency and the pressure inside the chamber to achieve optimal hydrogen production efficiency.

[0050] like Figure 4 and 5 As shown, the pyroelectric reaction interface is formed by a pyroelectric micropillar array 13 constructed on a substrate; the pyroelectric micropillar array 13 has a mixed wettability micro-nano composite surface, wherein the top of the micropillar is a pyroelectric hydrophilic surface, used to enhance cooling and carry out the reaction; the sides and bottom of the micropillar are superhydrophobic surfaces, used to form a gas film thermal resistance for heat preservation.

[0051] The substrate is made of 304 stainless steel, and the pyroelectric membrane 12 is made of lithium tantalate.

[0052] The pyroelectric micropillar array 13 is constructed by the following method:

[0053] First, a micropillar array is ablated on a stainless steel surface using femtosecond laser processing technology. During the laser processing, a nanoscale laser-induced periodic surface structure (LIPSS) is simultaneously induced on the surface. The column height and cross-sectional dimensions are controlled by calibrating the laser parameters, adjusting the laser power, scanning speed, pulse repetition frequency, and number of scans. The scanning path of the micropillar array is generated using CAD software, and the scanning spacing is set to control the micropillar spacing, thus realizing the construction of a micro-nano composite rough surface.

[0054] Then, the top of the micropillar is protected by a mask method, and the sides and bottom of the micropillar are modified with fluorosilane self-assembled molecular films to reduce the surface energy and construct superhydrophobic properties.

[0055] Finally, after removing the mask, a lithium tantalate (LiTaO3) thin film was deposited on the top of the micropillar using magnetron sputtering to form a pyroelectric hydrophilic surface.

[0056] Preferably, the pyroelectric micropillar array 13 has micropillar cross-sectional dimensions of 10-100 μm, pillar height of 20-200 μm, and area fraction of 0.2-0.8; the pillar spacing is 20-200 μm, forming voids filled with air, whose thermal conductivity is much lower than that of solid materials. This structure effectively suppresses the lateral diffusion of heat in the horizontal direction, and controlling the area fraction between 0.2-0.8 ensures that the voids between the pillars are filled with air while maintaining a high proportion of pyroelectric material.

[0057] The second cold water pump 4 is used to control the thickness and lateral flow velocity of the liquid in the impact chamber 11, so as to adjust the heat exchange efficiency and the pressure inside the chamber.

[0058] A method for producing hydrogen using the aforementioned composite wettable pyroelectric membrane high-frequency thermal cycling in-situ catalytic hydrogen production system includes the following steps:

[0059] Step S1: The hot fluid 7 is driven by the hot fluid pump 16 and flows through the heat exchanger 17 to exchange heat with the pyroelectric membrane 12.

[0060] Step S2: Cold water 1 is driven by the first cold water pump 3 and flows into the pressure chamber 8 to be pressurized. Then, it is transformed into a periodic oscillating jet 10 with a certain frequency by the oscillating jet array 9 and sprayed into the impact chamber 11 to perform high-frequency periodic cooling on the pyroelectric diaphragm 12.

[0061] Step S3: At the interface between the pyroelectric micropillar array 13 and the liquid, a pyroelectric effect occurs, generating polarized charges that react with H⁺ to generate hydrogen gas 14. The hydrogen gas 14 is collected through the gas outlet 15, and the liquid after the reaction is extracted by the second cold water pump 4.

[0062] Step S4: Depending on the source of the cold water, the cold water after the reaction is recycled or discharged through the cold water outlet 6 by controlling the second three-way valve 5. If the source of the cold water is river water or lake water, it is discharged directly through the cold water outlet 6. If the source is cooling tower cooling water, it can be recycled through the second three-way valve 5 and the first three-way valve 2.

[0063] Step S5: Evaluate the hydrogen production rate by controlling the impact spacing Zn and the thickness and lateral flow velocity of the liquid in the impact chamber 11 through the second cold water pump 4 to optimize the reaction conditions.

[0064] The hydrogen production rate was evaluated. If it was not ideal, the effect was improved by controlling the impact spacing Zn, the thickness of the liquid, and the lateral flow velocity, and the reaction conditions were optimized.

[0065] The source of the cold water 1 is river water, lake water, or cooling tower cooling water. The source of the heat fluid 7 is industrial low-temperature wastewater, heat collected by photothermal coating, or heat generated by electronic components.

[0066] Example 2

[0067] The difference between this embodiment and Embodiment 1 is that the low-grade heat energy source utilized by the pyroelectric membrane 12 is no longer waste heat from industrial wastewater, but rather heat generated by photothermal or electronic components such as chips.

[0068] like Figure 2 As shown, the specific hydrogen production method includes the following steps:

[0069] Step S1: Attach the photothermal coating or electronic components to the bottom of the pressure chamber 8 so that they can exchange heat with the pyroelectric membrane 12 and raise the temperature of the pyroelectric membrane 12.

[0070] Step S2: Cold water 1 is driven by the first cold water pump 3, flows through the first three-way valve 2 and then into the pressure chamber 8 to be pressurized. After being acted upon by the oscillating jet array 9, it is transformed from a stable inflow into a periodic oscillating jet 10 with a certain frequency, and is sprayed from the jet outlet into the impact chamber 11 to perform high-frequency periodic cooling on the pyroelectric diaphragm 12.

[0071] Step S3: The pyroelectric membrane 12 and the liquid interface undergo pyroelectric effect, generating polarized charges that react with H⁺ to generate hydrogen gas 14. The hydrogen gas 14 is collected through the gas outlet 15 and stored for use. The liquid after the reaction is extracted by the second cold water pump 4.

[0072] Step S4: If the source of cold water is river water or lake water, it is discharged directly through cold water outlet 6; if the source is cooling tower cooling water, it is recycled through the second three-way valve 5 and the first three-way valve 2.

[0073] Step S5: Evaluate the hydrogen production rate. If it is not ideal, improve the effect by controlling the impact spacing Zn, the thickness of the liquid in the impact chamber 11, and the transverse flow velocity, and optimize the reaction conditions.

[0074] The remaining structure and method steps are the same as in Example 1.

[0075] This invention employs an oscillating jet array 9 to transform a stable incoming flow into a high-frequency, periodic oscillating jet, achieving high-frequency alternating hot and cold impacts on the pyroelectric diaphragm 12, effectively stimulating the pyroelectric effect. The pyroelectric diaphragm 12 is made of lithium tantalate material, exhibiting excellent pyroelectric responsiveness and stability. This invention can utilize continuous heat flow such as industrial low-temperature wastewater as a heat source to achieve the recovery and utilization of low-grade waste heat. The cold water source is widely available, including river water, lake water, or cooling tower cooling water, and can be recycled, reducing operating costs.

[0076] The present invention constructs a pyroelectric micropillar array 13 with composite wettability on the surface of the pyroelectric membrane 12. Specifically, the top of the micropillar is designed as a pyroelectric hydrophilic surface to enhance the cooling reaction, and the nanowire structure on the side and bottom of the micropillar is designed as a superhydrophobic surface to form a gas film thermal resistance for heat preservation. This allows heat to be concentrated on the pyroelectric active region and form a large local dT / dt, thereby improving the energy conversion efficiency of the pyroelectric interface hydrogen production system.

[0077] This invention supports both cold water source circulation and discharge modes to adapt to different scenario requirements. Hydrogen production efficiency can be improved by optimizing reaction conditions, such as adjusting the impact spacing.

[0078] This invention utilizes a frequency-tunable oscillating jet element to generate a high-frequency thermal cycle that excites the pyroelectric effect. This creates a frequency-tunable oscillating jet element, which maintains a high dT / dt ratio of the pyroelectric film by increasing the characteristic time. A signal water inlet is embedded on one side of the frequency-tunable oscillating jet element, intermittently introducing signal water from the main jet and periodically inducing jet deflection / backflow. The jet oscillation frequency is inversely proportional to the length of the signal water pipe and is unaffected by the jet flow rate, providing an active control method for "designable and adjustable frequency." This achieves hydrogen production without an external electric field or precious metal catalyst, offering significant advantages such as wide energy sources, high system integration, flexible operation, and environmental friendliness. It is particularly suitable for industrial waste heat recovery and hydrogen production scenarios, possessing excellent industrialization prospects and technological promotion value.

[0079] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0080] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-frequency cold and hot cycle in-situ catalytic hydrogen production system using a composite wettable pyroelectric membrane, characterized in that, It includes a first cold water pump (3), a second cold water pump (4), a pressure chamber (8), an oscillating jet array (9), an impact chamber (11), a pyroelectric diaphragm (12), a pyroelectric micropillar array (13), and a gas outlet (15). The hot fluid (7) exchanges heat with the pyroelectric membrane (12); Cold water (1) is driven by the first cold water pump (3), flows through the first three-way valve (2) and into the pressure chamber (8), and after passing through the oscillating jet array (9), it forms an oscillating jet (10) and enters the impact chamber (11), and impacts the pyroelectric membrane (12). The surface of the pyroelectric membrane (12) is constructed with a pyroelectric micropillar array (13) having composite wettability. The pyroelectric micropillar array (13) forms a pyroelectric reaction interface. Under the alternating action of the oscillating jet (10) and the heat exchanger (17), a pyroelectric effect occurs at the pyroelectric reaction interface to generate hydrogen gas (14). The hydrogen gas (14) is collected through the gas outlet (15). After the reaction is completed, the cold water is driven by the second cold water pump (4), flows through the second three-way valve (5) and can be circulated to participate in the reaction, or flows out from the cold water outlet (6).

2. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 1, characterized in that, The oscillating jet array (9) includes multiple jet oscillator units; the multiple jet oscillator units are disposed on the wall surface of the pressure chamber (8); The single jet oscillator unit is provided with an oscillator inlet (901), a guide section (902), a mixing chamber (903), and an oscillator outlet (905) connected in sequence. The oscillator inlet (901) and the oscillator outlet (905) are both conical. The wide opening of the oscillator inlet (901) faces outward, and the narrow opening is connected to one end of the guide section (902). The other end of the guide section (902) is connected to one end of the mixing chamber (903). The diameter of the guide section (902) is smaller than that of the mixing chamber (903). The wide opening of the oscillator outlet (905) faces outward, and the narrow opening is connected to the other end of the mixing chamber (903). A signal water intake nozzle (904) is provided on one side of the mixing chamber (903), and a signal water inlet nozzle (907) is provided on the other side.

3. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 2, characterized in that, The width of the oscillator inlet (901) of the single jet oscillator unit is 20 mm, the lateral length of the guide section (902) is 10 mm, the longitudinal length is 10 mm, the lateral length of the mixing chamber (903) is 55 mm, the longitudinal length of the mixing chamber (903) is 35 mm, the height is 5 mm, the diameter of the signal water intake nozzle (904) and the signal water inlet nozzle (907) is 5 mm, and the offset rate is 0.

35.

4. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 2, characterized in that, The ratio of the impact spacing Zn to the flow characteristic length d of the jet oscillator unit is defined as the impact spacing ratio. The flow characteristic length d is the lateral length of the mixing chamber of the jet oscillator unit. The impact spacing Zn is the distance from the outlet of the jet oscillator unit to the impact target surface, i.e., the pyroelectric film (12). The impact spacing ratio is 3, at which time the impact spacing Zn is 165 mm and the flow characteristic length d is 55 mm.

5. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 2, characterized in that, The jet oscillator unit is a frequency-adjustable oscillating jet element. A signal water inlet (904) is embedded in one side of the mixing chamber (903) to intermittently introduce signal water from the main jet and periodically induce jet deflection or back-cutting. The oscillation frequency of the adjustable frequency oscillating jet element is inversely proportional to the length of the signal water pipe. The jet sweeping period is set to be greater than the unsteady thermal response time constant τ of the pyroelectric film, so that the inside of the pyroelectric film always maintains an unsteady temperature change, i.e., dT / dt≠0.

6. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 1, characterized in that, The pyroelectric reaction interface is formed by a pyroelectric micropillar array (13) constructed on a substrate; The pyroelectric micropillar array (13) has a mixed wettability micro-nano composite surface, wherein the top of the micropillar is a pyroelectric hydrophilic surface, which is used to enhance the cooling reaction; the sides and bottom of the micropillar are superhydrophobic surfaces, which are used to form a gas film thermal resistance for heat preservation.

7. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 5, characterized in that, The substrate is stainless steel, and the pyroelectric membrane (12) is made of lithium tantalate; The pyroelectric micropillar array (13) is constructed by the following method: First, a micro-pillar array is ablated on the stainless steel surface using femtosecond laser processing technology. During the laser processing, a nanoscale laser-induced periodic surface structure is simultaneously induced to form on the surface. Then, the top of the micropillar is protected by a mask method, and the sides and bottom of the micropillar are modified with fluorosilane self-assembled molecular films to reduce the surface energy and construct superhydrophobic properties. Finally, after removing the mask, a lithium tantalate film was deposited on the top of the micropillars using magnetron sputtering to form a pyroelectric hydrophilic surface.

8. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 1, characterized in that, The pyroelectric micropillar array (13) has a micropillar cross-sectional size of 10-100μm, a pillar height of 20-200μm, a pillar spacing of 20-200μm, and an area fraction of 0.2-0.

8.

9. The composite wettable pyroelectric membrane high-frequency cold and hot cycle in-situ catalytic hydrogen production system according to claim 1, characterized in that, The source of the heat fluid (7) is industrial low-temperature wastewater, heat collected by photothermal coating, or heat generated by electronic components. When the source of the hot fluid (7) is industrial low-temperature waste heat water, the hot fluid (7) is driven by the hot fluid pump (16), flows through the heat exchanger (17) and exchanges heat with the pyroelectric membrane (12) before flowing out from the hot fluid outlet (18); When the source of the heat fluid (7) is the heat collected by the photothermal coating or the heat generated by the electronic components, the photothermal coating or electronic components are attached to the bottom of the pressure chamber (8).

10. A method for producing hydrogen using the high-frequency cold and hot cycle in-situ catalytic hydrogen production system with composite wettable pyroelectric membranes as described in any one of claims 1-9, characterized in that, Includes the following steps: Step S1: When the source of the hot fluid (7) is industrial low-temperature waste heat water, the hot fluid (7) is driven by the hot fluid pump (16) and flows through the heat exchanger (17) to exchange heat with the pyroelectric membrane (12); when the source of the hot fluid (7) is the heat collected by the photothermal coating or the heat generated by the electronic components, the photothermal coating or electronic components are attached to the bottom of the pressure chamber (8) so that they exchange heat with the pyroelectric membrane (12) and the pyroelectric membrane (12) heats up. Step S2: Cold water (1) is driven by the first cold water pump (3) and flows into the pressure chamber (8) to be pressurized. Then, it is transformed into a periodic oscillating jet (10) with a certain frequency by the oscillating jet array (9) and sprayed into the impact chamber (11) to perform high-frequency periodic cooling on the pyroelectric membrane (12). Step S3: At the interface between the pyroelectric micropillar array (13) and the liquid, a pyroelectric effect occurs, generating polarized charges that react with H⁺ to generate hydrogen gas (14). The hydrogen gas (14) is collected through the gas outlet (15), and the liquid after the reaction is extracted by the second cold water pump (4). Step S4: Based on the source of cold water, control the reaction by using the second three-way valve (5) to recycle the cold water or discharge it through the cold water outlet (6); Step S5: Evaluate the hydrogen production rate and optimize the reaction conditions by controlling the thickness of the liquid in the impact chamber (11) and the transverse flow rate by controlling the impact spacing Zn and the second cold water pump (4).

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