Preparation method of backflow electrolyzed water microchannel capable of resisting gas-liquid fluctuation

Abstract

The invention discloses a preparation method of a gas-liquid fluctuation resistant backflow electrolyzed water microchannel, and relates to the technical field of preparation of hydrogen by electrolyzed water, the preparation method comprises the following steps: S1, selecting a polar plate of an unprocessed flow channel, and designing and processing a Tesla valve array structure comprising a Tesla island; s2, selecting a processed polar plate, and processing a micro-column array at a position close to the side wall of the Tesla structure channel; s3, respectively coating the anode side and the cathode side of the proton exchange membrane with iridium oxide and platinum carbon to prepare a catalyst layer of the membrane electrode; s4, preparing a diffusion layer, and hot-pressing the proton exchange membrane loaded with the catalyst layer and the diffusion layer together to form a membrane electrode with catalytic activity; and S5, assembling the polar plate and the membrane electrode to form the proton exchange membrane water electrolysis device with the Tesla structure and the local wettability channel. According to the invention, the phenomenon of gas-liquid backflow of the electrolytic water flow channel under large current can be effectively inhibited, and the loss of active sites caused by blockage of the flow channel by the backflow electrolytic gas is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of preparing hydrogen by electrolysis of water, and in particular to a method for preparing a microchannel for electrolysis of water that resists gas-liquid fluctuation and reflux. Background Art

[0002] The electrolytic hydrogen production process in the electrolyzer is a typical two-phase flow process in a closed space. When there is a high current and high power input, the gaseous products of water electrolysis will accumulate at the outlet and reflux will occur. This gas reflux phenomenon will increase the flow resistance of the electrolyzer, resulting in large fluctuations in current density, flow rate and electrolyzer temperature, so that the catalytic active sites in the water electrolysis process are covered by gas, resulting in the catalytic center being unable to contact the water working medium, resulting in increased ohmic resistance, decreased current density, and increased gas pressure in the electrolyzer. At the same time, the development of high current density electrolyzers will have the problem that the supply rate of local electrolytes cannot meet the gas evolution needs of the electrodes, bubbles will be blocked, resulting in uneven current density on the electrode surface and the entire electrolyzer, making the local electrolytic catalyst more susceptible to fatigue failure, thereby affecting the long-term operation stability of the entire electrolyzer and its adaptability to high current and high power.

[0003] Generally speaking, existing electrolytic cell flow optimization technologies are still limited to simple electrolysis flow channels without reflux inhibition and rewetting, or optimization of electrolysis parameters, such as replacing flow-guiding structures such as serpentines, grids, and mastoid plates, or increasing the power of pumping the electrolyte and other forced convection methods. These methods only focus on the contact process between the electrolyte and the electrode, and there is no orderly control over the bubble aggregation and discharge process in the flow channel and on the electrode surface. The electrolyte will still dry up locally on the electrode surface, and it cannot solve the long-standing two-phase flow reflux problem. Summary of the invention

[0004] The present invention solves the problems faced by miniaturized water electrolysis equipment, such as bubbles covering active sites resulting in high electrode overpotential and difficulty in increasing current density, and irregular gas-liquid two-phase reflux resulting in large gas-liquid transfer resistance in the flow channel and increased ohmic resistance. A method for preparing a water electrolysis microchannel that is resistant to gas-liquid fluctuation reflux is proposed, which effectively suppresses the phenomenon of gas-liquid reflux in the water electrolysis flow channel under high current, and avoids the loss of active sites caused by the refluxed electrolytic gas blocking the flow channel; at the same time, a stable supply of electrolyte to the active sites on the electrode surface and stability of the two-phase flow are achieved.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing a microchannel for electrolyzing water with resistance to gas-liquid fluctuation reflux, characterized in that it comprises the following steps: S1, select the plate without processed flow channel, design and process the Tesla valve array structure including Tesla island; S2, selecting the processed electrode plate and processing the micro-pillar array near the side wall of the Tesla structure channel; S3, coating iridium oxide and platinum carbon on the anode side and cathode side of the proton exchange membrane respectively to prepare a catalyst layer of the membrane electrode; S4, preparing a diffusion layer, hot pressing the proton exchange membrane carrying the catalytic layer and the diffusion layer together to form a catalytically active membrane electrode; S5, assembling the electrode plate and the membrane electrode to form a proton exchange membrane water electrolysis device with a Tesla structure and localized wettability channels.

[0006] This technical solution mainly includes the processing of the electrode plate, the preparation of the membrane electrode, and the assembly of the electrode plate and the membrane electrode. During the processing of the electrode plate, the main design is the processing of the Tesla valve array structure and the processing of the microcolumn array. The preparation of the membrane electrode mainly includes the preparation of the catalytic layer and the preparation of the diffusion layer. After the assembly of the electrode plate and the membrane electrode is completed, the final water electrolysis microchannel is obtained.

[0007] The present invention is further configured as follows: the electrode plates without processed flow channels are specifically two water electrolysis titanium electrode plates which only have inlet and outlet channels but without processed flow channels.

[0008] In the technical solution, after selecting the above-mentioned titanium electrode for water electrolysis, conventional Tesla valve array structures including Tesla islands with different array numbers are designed according to the prepared membrane electrode area.

[0009] The present invention is further configured as follows: the controller manages the device, the data area corresponding to the command and the configuration of the HART_IP module, and the HART_IP module manages the address of the access device of the HART_IP device, the number of commands, the command response parsing method and the data storage address.

[0010] The present invention is further configured as follows: Step S1 comprises: S11, processing Tesla microchannel by micro-milling; S12, processing the Tesla island where each Tesla bend exists; S13, the inlets of the Tesla valves converge into the same channel and the electrolyte is introduced through the same inlet; S14, the outlets of the Tesla valve converge in the same channel and the electrolyte is led out from the same outlet.

[0011] In this technical solution, the Tesla microchannel is first processed, and then the Tesla island where each Tesla bend exists is processed, and then the two sides of all Tesla one-way channels are respectively gathered in the same groove, the electrolyte enters from a unified inlet, the electrolyte is led out from a unified outlet, and the electrolyte circulation is completed after the gas-liquid separation is completed at the outlet.

[0012] The present invention is further configured as follows: Step S2 specifically comprises: The electrode plate processed in step S1 is selected, and a truncated cone-shaped micro-pillar array is processed by femtosecond laser near the side wall of the Tesla structure channel.

[0013] In this technical solution, the bottom diameter of the column is 35um, the top diameter is 20um, the height is 1mm, the distance between two adjacent columns is 20um, and the gap between the channel and the truncated cone column is 15um.

[0014] The present invention is further configured as follows: Step S3 comprises: S31, applying iridium oxide with a loading amount of 2 mg / cm2 and an active surface area of ​​1 cm2 to 4 cm2 as a catalyst coating on the anode side of the proton exchange membrane; S32, platinum carbon with a loading amount of 0.8 mg / cm2 is applied as a catalyst coating on the cathode side of the proton exchange membrane.

[0015] In the present technical solution, the catalyst layer of the membrane electrode is prepared through the above steps.

[0016] The present invention is further configured as follows: after step S2, the following steps are further included: The processed plates were immersed in a 5wt% potassium hydroxide solution and soaked for two hours.

[0017] In the technical solution, the processed electrode plate is immersed in a potassium hydroxide solution to provide a stronger wettability of the micro-column array on which it is located to water.

[0018] The present invention is further configured as follows: Step S4 comprises: Titanium felt is used as the diffusion layer of the anode, and hydrophobic carbon paper is used as the diffusion layer, and the proton exchange membrane supporting the catalytic layer and the diffusion layer are hot pressed together.

[0019] In the technical solution, the proton exchange membrane and the diffusion layer are formed into a compact whole by a hot pressing process.

[0020] The present invention is further configured as follows: Step S5 comprises: The torque applied to each bolt on the electrolyzer is 8N / m so that the micro-column structure of the Tesla channel is micro-embedded in the membrane electrode surface.

[0021] The present invention is further configured as follows: the width and length of the Tesla island are 0.3 mm and 0.7 mm respectively.

[0022] In this technical solution, the width and length of each Tesla island are the same.

[0023] The present invention is further configured as follows: the hot pressing parameters are 135° C., 2 Mpa, and the hot pressing time is 3 minutes.

[0024] The present invention can bring the following beneficial effects: 1. The Tesla valve structure adopted in the present invention can achieve unidirectional flow of gas and liquid, and the wall surface generates a reflux phenomenon at the outlet, which reduces the pressure drop caused by the flow and saves energy. At the same time, it reduces the resistance of unidirectional flow of bubbles, promotes the flow separation of bubbles in the electrolytic cell, speeds up the discharge of bubbles, and prevents the active sites from being covered by bubbles; 2. Compared with the traditional electrolytic cell, the present invention can achieve long-term stability of a higher current density. The Tesla valve accelerates the rate at which bubbles leave the electrode surface and avoids the accumulation of bubbles in the electrolytic cell, thereby reducing the ohmic resistance formed on the electrode surface, reducing the thermal expansion and thermal stress of the surface catalyst, and improving the long-term stability of the catalyst under high current operation; 3. The present invention uses a laser processing method to construct an array of micro-columns along the surface of the Tesla channel. By adjusting the roughness and relative spacing of the micro-column surface, the capillary force of the surface can be enhanced, thereby ensuring that the electrolytic water electrode interface still maintains sufficient liquid supply under the condition of high gas content, which can further enhance the unidirectional conductivity of the Tesla valve, while also ensuring that the electrolyte will not dry up locally, keeping the electrode surface always wetted by the electrolyte, and improving the utilization of active sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of a Tesla valve structure in a method for preparing a microchannel for electrolyzing water with resistance to gas-liquid fluctuation and reflux in the present application.

[0026] Figure 2 This is an enlarged view of the Tesla valve structure of the present application's method for preparing a microchannel for electrolyzing water that resists gas-liquid fluctuation reflux.

[0027] Reference numerals 1. Tesla valve array structure 2. Liquid inlet 3. Microcolumn infiltration structure 4. Liquid outlet 5. Liquid collecting tank 6. Tesla island. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] In the past few decades, the booming development of hydropower, wind power, solar power and tidal power has shown its great potential as a clean alternative to fossil energy. However, due to the geographical dislocation between energy production areas and energy consumption areas, as well as the intermittent nature of renewable electricity production, it is difficult for renewable energy such as wind and solar power to be directly integrated into the power grid. Therefore, there is an urgent need for an efficient energy carrier to achieve cross-regional scheduling and use of energy. Hydrogen has been regarded as an ideal energy carrier for the future energy society due to its advantages such as zero emissions and high energy density. The International Renewable Energy Agency predicts that by 2050, hydrogen and its derivatives will account for 12% of the world's energy consumption. For the source of hydrogen, the decline in the price of renewable electricity provides an opportunity for rapid development of hydrogen production by electrolysis of water, which reduces the storage and transportation costs of renewable energy in remote areas and makes cross-regional scheduling possible. Electrocatalytic hydrogen evolution is a key technology that can be coupled with renewable energy such as photovoltaics and wind power. However, the high cost of its precious metal catalysts and the rapid decline in electrolysis performance at actual high current densities hinder the further industrial application of electrocatalytic hydrogen evolution technology. Currently, most research focuses on reducing the manufacturing and use costs of electrolyzers by developing new catalysts and electrode materials. However, in actual operation, the effects of electrolysis products and bubbles on electrolyzer performance are often ignored.

[0030] The electrolytic hydrogen production process in the electrolyzer is a typical two-phase flow process in a closed space. When high current and high power input electricity exist, the gaseous products of water electrolysis will accumulate at the outlet and reflux will occur. This gas reflux phenomenon will increase the flow resistance of the electrolyzer, resulting in large fluctuations in current density, flow rate and electrolyzer temperature, so that the catalytic active sites in the water electrolysis process are covered by gas, resulting in the catalytic center being unable to contact the water working fluid, resulting in increased ohmic resistance, decreased current density, and increased gas pressure in the electrolyzer. At the same time, the development of high current density electrolyzers will cause the supply rate of local electrolytes to fail to meet the gas evolution needs of the electrodes, and bubbles will be blocked, resulting in uneven current density on the electrode surface and the entire electrolyzer, making the local electrolytic catalyst more susceptible to fatigue and failure, thereby affecting the long-term operation stability of the entire electrolyzer and its adaptability to high current and high power.

[0031] Generally speaking, existing electrolytic cell flow optimization technologies are still limited to simple electrolysis flow channels without reflux inhibition and rewetting, or optimization of electrolysis parameters, such as replacing flow-guiding structures such as serpentines, grids, and mastoid plates, or increasing the power of pumping the electrolyte and other forced convection methods. These methods only focus on the contact process between the electrolyte and the electrode, and there is no orderly control over the bubble aggregation and discharge process in the flow channel and on the electrode surface. The electrolyte will still dry up locally on the electrode surface, and it cannot solve the long-standing two-phase flow reflux problem.

[0032] In ordinary electrochemical testing, bubble separation on the electrode surface is often in an open space, which can achieve bubble emptying and effective management. However, the actual compact proton exchange membrane electrolyzer has a small internal space (especially the oxygen evolution anode chamber where there is gas-liquid two-phase flow), and the two-phase flow of bubbles and flow is transferred from the open space to the closed channel, which will face more challenges in achieving directional two-phase flow management. First, the two-phase flow in the confined space becomes more chaotic, random and uncontrollable. Although orderly single annular flow can be achieved by decorating the side walls of the channel with micro-pin-fin fences, it is still affected by uncontrolled gas backflow and localized drying of the electrolyte under high current.

[0033] In order to adjust the stability of two-phase flow, various geometries of electrolysis flow channels have been proposed in the prior art, such as interconnected microchannels, bidirectional microchannels, micro pin fins, microchannels with expanded flow channels, staggered microchannels, zigzag microchannels and tree-shaped microchannels.

[0034] Generally, the gradually enlarged microchannels can promote the removal of bubbles in the confined space of the electrolyzer flow channel by reducing the flow resistance in the flow direction. Interconnected microchannels can effectively suppress hydrogen reflux and bubble blockage by balancing the pressure between adjacent channels. The removal of bubbles is promoted by accelerating the growth-dissipation of bubbles using high-frequency oscillation. In comparison, the inlet channel structure has been proven to be one of the most effective designs for suppressing two-phase reflux and improving the stability of two-phase flow. However, the pressure drop at the inlet and outlet of the electrolyzer caused by its complex flow channel structure is too large, the problem of increased energy consumption of the electrolyzer still exists, and the problem of local electrolyte drying up cannot be solved, resulting in poor adaptability and flow stability of the electrolyzer at high current density. It is crucial to achieve stable management and directional flow of bubbles and two-phase flow on the electrode surface and in the overall channel, which is crucial to improve the electrolysis performance without increasing additional energy consumption, and is also the key to further improve the power density of the electrolyzer. Therefore, it is urgent to design a water electrolysis microchannel current collector with unidirectional electrolyte flow, bubble reflux, and rapid rewetting characteristics of the electrode interface.

[0035] The origin of the Tesla valve structure is that due to its unique unidirectional flow properties, it has become a key feature for suppressing reverse gas reflux. The stronger the unidirectional flow, the more effective the reflux suppression of the gas generated by electrolysis. At present, Tesla valves are only widely used in the field of heat transfer, suppressing the two-phase flow in boiling heat transfer, and adjusting some key parameters of the Tesla valve can control the gas-liquid two-phase flow process. However, the application of serrated and Tesla-type microchannel configurations in series in boiling heat transfer has been studied before. Although the flowing working fluid can flow smoothly in one direction, the unique Tesla valve structure will produce gas-liquid separation, but lock part of the generated gas, resulting in local interface drying and gas transmission obstruction. In addition, in the flow channel of the electrolytic cell, the reaction involves more violent electrochemical reactions and electrode polarization processes, and often faces more severe gas-liquid separation and gas reflux, resulting in a decrease in the rewetting performance of the electrode, leading to the bottleneck problem of loss of electrolytic active sites under high current.

[0036] Therefore, the purpose of the present invention is to propose an anode electrolyte flow channel of a proton exchange membrane electrolyzer based on a Tesla valve and a local rewetting micro-nano structure, strengthen the separation of bubbles in the flow channel, reduce the coverage of active sites, and improve the stability of the electrolyzer under high current. The unidirectional characteristics of the Tesla valve channel are utilized to effectively suppress the phenomenon of gas-liquid reflux in the electrolytic water flow channel under high current, and avoid the refluxed electrolytic gas blocking the flow channel and causing the loss of active sites. At the same time, the micro-columns with geometric gradients arranged along the wall use capillary forces to drive the redistribution of the electrolyte, re-wet the gas-blocked part of the Tesla valve, and form a stable wetted liquid film along the wall and Tesla island, thereby providing electrolyte to the electrode surface, avoiding complete coverage of active sites under high current and large bubbles, and achieving stable supply of electrolyte to active sites on the electrode surface, as well as stability of two-phase flow.

[0037] Example 1 This embodiment proposes a method for preparing a microchannel for electrolyzing water with resistance to gas-liquid fluctuation reflux, referring to Figure 1 and Figure 2 , which mainly includes the following steps.

[0038] Step S1, select the electrode plate without processed flow channels, design and process the Tesla valve array structure including Tesla islands; more specifically, for the electrode plate without processed flow channels, this embodiment specifically uses two water electrolysis titanium electrode plates with only inlet and outlet channels but no processed flow channels.

[0039] Step S1 mainly includes the following sub-steps.

[0040] First, the Tesla microchannel was processed by micro-milling; the width and height of the processed Tesla channel were 0.45 mm and 1 mm, and the width of the Tesla bend was 0.2 mm.

[0041] Subsequently, a Tesla island 6 is processed where each Tesla bend exists; the width and length of the Tesla island are 0.3 mm and 0.7 mm, respectively.

[0042] Next, all Tesla one-way channels are gathered in the same channel and the electrolyte is introduced from the same inlet. Figure 1 The Tesla valve outlets converge in the same channel and the electrolyte is led out from the same outlet. Figure 1 The liquid outlet 4 is formed in the electrolyte. After the gas-liquid separation is completed at the outlet, the electrolyte circulation is completed. This process is carried out in the liquid collecting tank 5.

[0043] Step S2, select the processed electrode plate, and process a micro-column array (including a plurality of micro-column infiltration structures 3) near the side wall of the Tesla structure channel; more specifically, after the electrode plate is processed according to step S1, a truncated cone-shaped micro-column array is processed by a femtosecond laser near the side wall of the Tesla structure channel. In this embodiment, the bottom diameter of the micro-column is 35um, the top diameter is 20um, the height is 1mm, the distance between two adjacent micro-columns is 20um, and the gap between the channel and the truncated cone column is 15um.

[0044] After step S2 is completed, the processed electrode plate is immersed in a 5 wt % potassium hydroxide solution for two hours to provide stronger water wettability to the micro-pillar array on which it is located.

[0045] Step S3, coating iridium oxide and platinum carbon on the anode side and cathode side of the proton exchange membrane respectively to prepare a catalytic layer of the membrane electrode; it specifically includes the following sub-steps.

[0046] Step S31, the active surface area is 1cm 2 ~4cm 2 The loading amount is 2mg / cm 2 Iridium oxide is used as a catalyst coating on the anode side of the proton exchange membrane.

[0047] Step S32: adding a loading amount of 0.8 mg / cm 2 Platinum carbon is used as a catalyst coating and applied to the cathode side of the proton exchange membrane to complete the catalytic layer preparation of the membrane electrode.

[0048] Step S4, prepare a diffusion layer, and hot press the proton exchange membrane carrying the catalytic layer and the diffusion layer together to form a catalytically active membrane electrode; specifically, titanium felt is used as the diffusion layer of the anode, and hydrophobic carbon paper is used as the diffusion layer, and the proton exchange membrane carrying the catalytic layer and the diffusion layer are hot pressed together by a hot pressing method, and the hot pressing parameters are 135°C, 2Mpa, and hot pressing for 3 minutes to form a tight whole to form a catalytically active membrane electrode.

[0049] Step S5, assembling the electrode plate and the membrane electrode to form a proton exchange membrane water electrolysis device with a Tesla structure and localized wettability channels. Specifically, the electrode plate processed in the above steps is assembled with the membrane electrode, and the torque applied to each bolt on the electrolyzer is 8N / m, ensuring that the micro-column structure of the Tesla channel is micro-embedded in the membrane electrode surface, forming a proton exchange membrane water electrolysis device with a Tesla structure and localized wettability channels.

[0050] After the preparation is completed, in the above-mentioned electrolytic cell, the cathode plate and the anode plate are assembled with the membrane electrode. The cathode plate and the anode plate use pure water as the flowing working fluid, which is pumped into the cathode and anode chambers respectively at a flow rate of 20 ml / min. The anode and anode electrolytes both use pure water with a resistivity of 18 megohms. The temperature of the electrolytic cell is controlled by a heat conductive rod to ensure that the cell body reacts at 80 degrees Celsius under a given voltage.

[0051] In this embodiment, pure titanium plate is used as the electrode material, and an electrolyte flow channel with a Tesla valve structure is machined on the surface of the electrode plate through micro-milling to achieve directional transport of electrolyte and bubbles, thereby inhibiting gas-liquid reflux; a truncated cone-shaped micro-column array with capillary force is machined on the side of the flow channel through laser processing to achieve re-infiltration of the electrode surface, thereby ensuring the supply of electrolyte to the electrode surface.

[0052] The unidirectional flow mechanism of gas and water in the Tesla structure channel is as follows: When the water electrolysis process occurs, the gas-liquid two-phase flow flows forward along the flow direction driven by the pump. The flow resistance of the liquid and the generated gas is low, and the flow path of each branch is the same. When the gas and liquid converge, since there is only one outlet for the electrolyte, the two-phase flow gathers in the confluence channel at the outlet, resulting in reverse flow. At this time, when the reflux passes through the Tesla valve in the opposite direction, it will form a branch in the opposite direction of the main flow through the branch, and the flow resistance will increase, thereby suppressing the backflow phenomenon of the flow, preventing the gas from accumulating inside the flow pipe, and affecting the utilization of the active sites of the catalytic interface.

[0053] The rewetting mechanism of water on the microcolumns on the wall of the flow channel along the flow direction is as follows: Due to laser etching in the air, the originally smooth titanium surface has a roughness of about 350nm. After soaking in potassium hydroxide, the surface of the microcolumns is loaded with a large number of hydroxyl hydrophilic groups, making the laser-processed surface highly hydrophilic, with a water contact angle of about 0°. In contrast, the contact angle of the titanium electrode surface is about 45°. Therefore, the capillary pressure between the wall and the titanium electrode can be obtained by the following calculation, where d is the gap between the microcolumns, r is the surface tension, and seta is the contact angle of the liquid. Therefore, two adjacent microcolumns can form a capillary structure to induce electrolyte seepage from the main channel to the wall of the branch, ensuring rewetting of the wall and the bottom electrode under high current, and providing electrolyte to the bottom electrode surface to prevent drying.

[0054] The mechanism of water migration along the surface of the microcolumn in the gap formed by the truncated cone microcolumn and the wall is as follows: Due to the geometric gradient of the cylindrical shape and the hydrophilic interface, when the proton exchange membrane water electrolysis is operated at high power, the gas content of the entire flow channel is high. The geometric gradient of the truncated cone will cause the liquid to migrate along the large radius of curvature of the truncated cone, thereby enhancing the fluid convection on the electrode surface, generating an upward driving force for the bubbles generated by the electrode, accelerating the detachment of the bubbles, and thus accelerating the liquid re-infiltration process on the electrode surface.

[0055] The plate material in this embodiment may also be other materials, which are not limited here.

[0056] The micro-column material structure in this embodiment is not unique, and any method with a certain geometric gradient or directional liquid transport is applicable.

[0057] This embodiment can also bring the following technical effects, which mainly include three points.

[0058] First, the prior art commonly uses serpentine flow channels or parallel flow channels, neither of which contains any microstructures that prevent bubble reflux or enhance bubble shedding. There is a gas-liquid reflux phenomenon under high current, or there is bubble blockage, resulting in low utilization efficiency of active sites. If the intensity of forced convection is increased, the pressure drop of the reactor will increase, the power consumption will be significantly increased, and the energy efficiency of bubble detachment will be relatively reduced. The Tesla valve structure used in this embodiment can enable gas and liquid to flow in one direction, and the wall surface will produce a reflux phenomenon at the outlet, reducing the pressure drop caused by the flow and saving energy. At the same time, it reduces the resistance to unidirectional flow of bubbles, promotes the flow separation of bubbles in the electrolytic cell, accelerates the discharge of bubbles, and prevents active sites from being covered by bubbles. Experiments have shown that the comprehensive energy consumption of the electrolytic cell with a Tesla structure valve structure (including the energy consumption of the electrolytic cell pump) of the assembled system is less than 4.5kw·h / Nm 3 Compared with the energy consumption of 4.9kw·h / Nm2 of the traditional serpentine electrolyzer, 3 Significantly reduced.

[0059] Secondly, this embodiment can achieve long-term stability of a larger current density than the traditional electrolyzer. Because of the accumulation of bubbles during the electrolysis process and the reflux of the electrolytic gas, the bubbles in the traditional electrolysis channel cannot be discharged in time, the ohmic resistance increases significantly, the heat generated by the electrode surface increases sharply under the action of the current, and the local catalyst undergoes thermal expansion, shedding and deactivation, and falls off from the membrane electrode surface. The Tesla valve accelerates the rate at which bubbles leave the electrode surface and avoids the accumulation of bubbles in the electrolyzer, thereby reducing the ohmic resistance formed on the electrode surface, reducing the thermal expansion and thermal stress of the surface catalyst, and improving the long-term stability of the catalyst under high current. During the 100h test of the proton exchange membrane electrolyzer of the 500mA / cm2 chronovoltammetry method, the voltage rise did not exceed 20uV / h, and the voltage rise rate was one tenth of the 100uV / h of the serpentine channel.

[0060] Thirdly, this embodiment uses a laser processing method to construct an array of micro-pillars along the surface of the Tesla channel. By adjusting the roughness and relative spacing of the micro-pillar surface, the capillary force on the surface can be enhanced, thereby ensuring that the electrolytic water electrode interface still maintains sufficient liquid supply under the condition of high gas content, which can further enhance the unidirectional conductivity of the Tesla valve, and also ensure that the electrolyte will not dry up locally, keep the electrode surface always wetted by the electrolyte, and improve the utilization of active sites. Compared with the existing flow channel structure without micro-pillars, it can also further reduce the blockage of bubbles, accelerate the detachment of bubbles from the electrode surface, reduce ohmic resistance, and reduce energy consumption and catalyst resistance. Experiments have shown that under the operating current condition of 1A / cm2, the temperature rise is less than 10°C compared with the electrolytic cell with a flow channel without a Tesla valve structure.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a microchannel for electrolyzed water with resistance to gas-liquid fluctuation reflux, characterized in that: The following steps are involved: S1, select the plate without processed flow channel, design and process the Tesla valve array structure including Tesla island; S2, selecting the processed electrode plate and processing the micro-pillar array near the side wall of the Tesla structure channel; S3, coating iridium oxide and platinum carbon on the anode side and cathode side of the proton exchange membrane respectively to prepare a catalyst layer of the membrane electrode; S4, preparing a diffusion layer, hot pressing the proton exchange membrane carrying the catalytic layer and the diffusion layer together to form a catalytically active membrane electrode; S5, assembling the electrode plate and the membrane electrode to form a proton exchange membrane water electrolysis device with a Tesla structure and localized wettability channels.

2. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 1, characterized in that: The electrode plates without processed flow channels are specifically two titanium electrode plates for water electrolysis that only have inlet and outlet channels but without processed flow channels.

3. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 1 or 2, characterized in that: The step S1 comprises: S11, processing Tesla microchannel by micro-milling; S12, processing the Tesla island where each Tesla bend exists; S13, the inlets of the Tesla valves converge into the same channel and the electrolyte is introduced through the same inlet; S14, the outlets of the Tesla valve converge in the same channel and the electrolyte is led out from the same outlet.

4. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 3, characterized in that: The step S2 is specifically as follows: The electrode plate processed in step S1 is selected, and a truncated cone-shaped micro-pillar array is processed by femtosecond laser near the side wall of the Tesla structure channel.

5. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 1, 2 or 4, characterized in that: The step S3 comprises: S31, the active surface area is 1cm 2 ~4cm 2 The loading amount is 2mg / cm 2 Iridium oxide is used as a catalyst coating on the anode side of the proton exchange membrane; S32, the loading amount is 0.8 mg / cm 2 Platinum-carbon is used as a catalyst coating on the cathode side of the proton exchange membrane.

6. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 4, characterized in that: The step S2 further includes: The processed plates were immersed in a 5wt% potassium hydroxide solution and soaked for two hours.

7. A method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 1, 2 or 4, characterized in that: The step S4 comprises: Titanium felt is used as the diffusion layer of the anode, and hydrophobic carbon paper is used as the diffusion layer, and the proton exchange membrane supporting the catalytic layer and the diffusion layer are hot pressed together.

8. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 1, 2 or 4, characterized in that: The step S5 comprises: The torque applied to each bolt on the electrolyzer is 8N / m so that the micro-column structure of the Tesla channel is micro-embedded in the membrane electrode surface.

9. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 3, characterized in that: The width and length of the Tesla island are 0.3 mm and 0.7 mm, respectively.

10. The method for preparing a gas-liquid fluctuation reflux electrolytic water microchannel according to claim 7, characterized in that: The hot pressing parameters are 135° C., 2 MPa, and the hot pressing time is 3 minutes.

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