A stepwise drying line for the production of fuel cell catalyst layers and a method of using the same

Abstract

The present application relates to a kind of for the preparation of fuel cell catalyst layer step drying pipeline and its use method, comprising: conveying unit, low-pressure heat conduction drying unit, vacuum microwave drying unit and vacuum unit;The low-pressure heat conduction drying unit includes bottom heating device, low-pressure bin, first manifold branch, and the first manifold branch is connected with vacuum unit;The vacuum microwave drying unit includes vacuum bin, microwave heating device and second manifold branch, and the second manifold branch is connected with vacuum unit;Catalyst ink is under the action of conveying unit, respectively, in low-pressure bin in low-pressure state and in vacuum bin in vacuum state, bottom heating device carries out low-pressure heating, and microwave heating device carries out vacuum microwave drying.Compared with prior art, the present application improves the production efficiency of catalyst layer, reduces product defect, improves the degree of automation of catalyst layer, and realizes process flow programmable and wide range of application.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell catalyst layer preparation technology, and in particular relates to a stepwise drying production line for fuel cell catalyst layer preparation and its usage method. Background Technology

[0002] A proton exchange membrane fuel cell (PEMFC) is an energy conversion device that directly converts the chemical energy of hydrogen into electrical energy. The fuel cell stack consists of individual cells stacked in series. The membrane electrode assembly (MEA) inside each cell is the core component for converting chemical energy into electrical energy, and the catalyst layer (CL) is the main site of electrochemical reactions. Its composition and structure greatly determine the efficiency of these reactions. Specifically, the mass transfer capacity, electrochemical active surface area, proton conductivity, and contact resistance of the catalyst layer have a significant impact on the performance and lifespan of the fuel cell. One method for preparing the catalyst layer is the blade coating transfer method, which involves a drying process from catalyst ink to the catalyst layer. The drying process largely determines the morphology of the catalyst layer, as well as the efficiency and cost of industrial production.

[0003] Currently, commonly used drying processes employ heat conduction to directionally heat the ink layer, raising the solvent temperature to its evaporation temperature, thus causing the solvent to vaporize and diffuse into the atmosphere. Once the ink reaches its gel point, catalyst particles gradually deform, deposit, and close the pores, constructing a three-dimensional porous catalyst network that provides a porous medium for the electrochemical reaction. However, this drying technology has several drawbacks: 1. Evaporation drying in an atmospheric environment means that when the saturated vapor pressure is atmospheric (101.32 kPa), a high drying temperature is required. This is especially true for water in the dispersing solvent component, where a very high temperature is needed to prevent water from remaining in the pores for too long, leading to uneven dispersion and stress concentration within the network structure. For industrial production equipment, higher temperatures mean higher resistance and lower efficiency of the heating wire, requiring higher voltage and more demanding heating equipment, ultimately increasing production costs. 2. Evaporation efficiency under atmospheric conditions is not high because atmospheric pressure hinders the diffusion of solvent vapor. Especially after the catalyst ink has passed its gel point, its internal solvent removal methods can only diffuse into the atmosphere through the pore network. If a sufficient pressure gradient cannot be generated above the two-phase interface, the efficiency of the later stages of evaporation drying will be extremely low. 3. A longer drying duration means that the duration of internal capillary forces during catalyst particle consolidation will be prolonged. From the perspective of the drying mechanism, this is more conducive to the formation of defects such as cracks and secondary pores. Too many structural defects can lead to a reduction in the electrochemically active surface area, localized gas permeation, and catalyst layer delamination. 4. Gradient control of the drying temperature can effectively reduce the stress caused by local temperature differences within the catalyst layer, which is more conducive to the preparation of a uniform and smooth catalyst layer. Traditional in-situ drying equipment (such as ovens and plate heaters) can only achieve gradient or staged temperature control by setting a variable temperature program. The disadvantage is that the temperature change process takes a certain amount of time, affecting the efficiency of industrial production and increasing the duration of capillary force action, indirectly increasing the possibility of catalyst layer defects. Secondly, stationary equipment must restore the temperature to the initial temperature of the drying process before performing the same drying process on the next batch of products. This not only creates an interval between production batches but also consumes a significant amount of energy. 5. Traditional bottom heating devices (such as flatbed heaters) cannot fully customize heating conditions; they can only control the drying process from two dimensions: heating temperature and heating time. Changes in the composition of the catalyst ink will alter the rheological properties of the ink and the stress distribution within the catalyst film in its gel state. When drying conditions are demanding, such as requiring shorter heating times and lower temperatures, simple heat conduction drying cannot meet these requirements because it contradicts the principle that heat conduction promotes solvent vaporization and evaporation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a stepwise drying production line for fuel cell catalyst layer preparation, which has higher production efficiency, fewer product defects, higher automation, programmable process flow, and wider applicability, as well as its method of use.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] This invention provides a stepwise drying production line for the preparation of catalyst layers in fuel cells, comprising:

[0007] A conveying unit for controlling the movement of catalyst ink, and a low-pressure heat conduction drying unit and a vacuum microwave drying unit arranged sequentially along the direction of catalyst ink movement and located below and above the conveying unit, respectively, and a vacuum unit located above the low-pressure heat conduction drying unit and the vacuum microwave drying unit for controlling the pressure inside the low-pressure heat conduction drying unit and the vacuum microwave drying unit.

[0008] The low-pressure heat conduction drying unit includes a bottom heating device, a low-pressure chamber located above the bottom heating device, and a first manifold branch connected to the low-pressure chamber, the first manifold branch being connected to a vacuum unit;

[0009] The vacuum microwave drying unit includes a vacuum chamber connected to a low-pressure chamber, a microwave heating device located above the vacuum chamber for vacuum microwave drying of the catalyst ink, and a second manifold branch connected to the vacuum chamber, the second manifold branch being connected to the vacuum unit.

[0010] During operation, the catalyst ink passes through a low-pressure chamber and a vacuum chamber under the action of the conveying unit. The bottom heating device heats the catalyst ink in the low-pressure chamber at low pressure, and the microwave heating device dries the catalyst ink in the vacuum chamber in a vacuum microwave.

[0011] To separately control the pressure of the low-pressure chamber and the vacuum chamber, a vacuum pump is installed to evacuate them. A three-way electronic valve is connected to the vacuum chamber, the low-pressure chamber, and the outside air. The three-way electronic valve controls the opening and closing of the gas pipeline and works with the vacuum pump to control the pressure of the low-pressure chamber and the vacuum chamber. The specific settings are as follows:

[0012] Furthermore, the vacuum unit includes a vacuum pump, a three-way electronic valve connected to the vacuum pump, and a manifold located on the three-way electronic valve;

[0013] The manifold includes a first manifold branch, a second manifold branch, a third manifold branch connected to the outlet of the vacuum pump, and a fourth manifold branch connected to air.

[0014] The vacuum pump controls the pressure of the low-pressure chamber and the vacuum chamber through the first manifold branch and the second manifold branch, respectively.

[0015] The three-way electronic valve controls the opening and closing of the first manifold branch, the second manifold branch, the third manifold branch, and the fourth manifold branch.

[0016] When the fourth manifold branch is closed and the first, second, and third manifold branches are connected, the pressure of the drying chamber can be controlled.

[0017] When the fourth manifold branch, the first manifold branch, and the second manifold branch are open, and the third manifold branch is closed, the drying chamber can be depressurized.

[0018] To achieve precise control of the low-pressure heat conduction drying unit, a temperature controller is installed to allow several groups of graphite heating plates to operate at different heating temperatures. The specific settings are as follows:

[0019] Furthermore, the bottom heating device includes several graphite heating plates and a temperature controller connected to the graphite heating plates, and the graphite heating plates can be set to different temperatures.

[0020] In a preferred embodiment of the present invention, three sets of graphite heating plates are provided, each set connected to a temperature controller. The temperatures of the three sets of graphite heating plates should be set to a low-high-low or low-medium-high state to achieve a gradual change from room temperature to high temperature during the bottom heating and drying process, which is beneficial to the conversion of catalyst ink to catalyst gel. Furthermore, in the low-pressure heat conduction drying unit, two gradual temperature changes are achieved: an in-situ temperature change from room temperature to high temperature within any region of the catalyst ink, and a gradual temperature difference change between any two adjacent regions of the catalyst ink. This ensures that at any time and at any location, there will be no uneven movement of particles due to local temperature differences, thereby preventing defects such as tearing, breakage, and pores in the catalyst particle network structure.

[0021] To achieve precise control of the vacuum microwave drying unit, a magnetron is configured to generate a microwave field within the vacuum chamber to ensure uniform vacuum microwave drying of the catalyst gel. The specific configuration is as follows:

[0022] Furthermore, the microwave heating device includes a magnetron located on the inner wall of the vacuum chamber for generating high-frequency microwaves, a waveguide connected to the magnetron for transmitting high-frequency microwaves to the vacuum chamber, and a microwave stirrer located next to the waveguide for averaging high-frequency microwaves.

[0023] The microwave stirrer is equipped with rotatable metal refractive blades.

[0024] The magnetron can continuously generate high-frequency microwaves and couple them to the vacuum chamber via a waveguide, guiding the microwaves to the microwave stirrer with extremely low loss. The rotation of the metal refractive blades of the microwave stirrer enables periodic changes in the magnetron load, resulting in a large frequency pull. At the same time, the periodic changes in the refraction of the blades can continuously change the excitation state of the coupling port. The combination of these two effects improves the uniformity of the microwave field distribution inside the vacuum drying chamber, causing the residual polar solvent molecules (mainly non-volatile water molecules) in the catalyst particle network to oscillate rapidly at extremely high frequencies.

[0025] In the microwave field, residual polar solvent molecules gain enormous energy and heat up, diffusing out of the pores through molecular thermal motion, rapidly removing residual moisture from the particle network. The microwave drying stage should not last too long to avoid water molecules with high kinetic energy damaging the catalyst particle network.

[0026] At this point, it is preferable that the vacuum chamber body, sealed chamber door, and movable partition are made of stainless steel, which can effectively reflect microwaves.

[0027] Considering the varying lengths of different catalyst inks, the movable partition is designed to be repositionable. This allows catalyst inks of different lengths to be dried in this step-by-step drying line. The specific settings are as follows:

[0028] Furthermore, a movable partition is provided between the low-pressure chamber and the vacuum chamber. The low-pressure chamber, the movable partition, and the vacuum chamber are connected in sequence to form a drying chamber. The movable partition is movable, can be opened and closed, and is arranged in the drying chamber perpendicular to the direction of travel of the catalyst ink.

[0029] To ensure that the catalyst gel in the vacuum microwave drying unit is completely inside the vacuum chamber, the following setup is adopted:

[0030] Furthermore, the length of the vacuum chamber is at least longer than the length of the catalyst ink.

[0031] Considering the issue of transporting the catalyst ink to the final catalyst layer, the following settings are adopted:

[0032] Furthermore, a sealed chamber door for discharging catalyst ink is provided at one end of the vacuum chamber away from the movable partition.

[0033] Considering the precise control of the fine catalyst ink's journey through the low-pressure drying unit and the vacuum microwave drying unit, the following settings are adopted:

[0034] Furthermore, the conveying unit includes a conveyor belt for placing catalyst ink, a support structure located below the conveyor belt for supporting the conveyor belt, a plurality of pulleys located at both ends of the conveyor belt, a plurality of tensioning pulleys located below the conveyor belt for tensioning the conveyor belt, and a plurality of servo motors for controlling the operation of the pulleys.

[0035] The servo motor is equipped with a control panel for programmable start / stop and speed control.

[0036] In a preferred embodiment of the present invention, two pulleys and two tensioning pulleys are provided.

[0037] Considering the issues related to the feeding and discharging of catalyst ink, the following settings are adopted:

[0038] Furthermore, the two ends of the conveying unit are also provided with a feed inlet ramp for facilitating the conveying of catalyst ink, and a discharge inlet ramp for conveying the dried catalyst layer.

[0039] The present invention also provides a method for using a stepwise drying production line for the preparation of catalyst layers for fuel cells, comprising the following steps:

[0040] S1: The catalyst ink is coated onto the polymer substrate and placed on the feed inlet ramp. The control panel controls the servo motor to drive the conveyor belt to start running. At this time, the movable partition is in the open state, the vacuum pump is turned on, the three-way electronic valve controls the fourth manifold branch to close and the first manifold branch and the third manifold branch to connect. At this time, the low-pressure chamber is in a low-pressure state.

[0041] S2: The catalyst ink runs in the low-pressure chamber, and the graphite heating plate is set to different temperatures to heat the catalyst ink and transform it into catalyst gel.

[0042] S3: The catalyst gel arrives at the vacuum chamber. At this time, the movable partition is closed, and the second manifold branch and the third manifold branch are connected. The vacuum pump draws the vacuum chamber to a vacuum state. The magnetron and microwave stirrer work together to vacuum microwave dry the catalyst gel in the vacuum chamber. Then the catalyst gel is converted into a dried and shaped catalyst layer. After drying, the sealed chamber door is opened, and the conveyor belt sends the substrate out.

[0043] S4: Then the servo motor shuts off, the conveyor belt stops, the vacuum pump shuts off, the three-way electronic valve controls the third manifold branch to close, the fourth manifold branch to open, the movable partition opens, and both the low-pressure chamber and the vacuum chamber return to normal atmospheric pressure.

[0044] This application designs a step-by-step production line for the drying process, which effectively improves the efficiency of industrial production, while reducing structural defects in the catalyst layer such as cracks and delamination, and increasing the porosity and electrochemically active surface area of ​​the catalyst layer, thereby comprehensively improving the performance and lifespan of the catalyst layer.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] (1) By introducing a production line, this invention enables sample movement while keeping the heating device fixed, thereby indirectly achieving gradient control of the heating temperature. This eliminates the reliance on the temperature-changing function of ovens or heating plates. Furthermore, the configuration of three graphite heating plates allows the metal support structure above to generate a gradual temperature range, which helps avoid stress concentration caused by local temperature differences. Obviously, compared to variable temperature heating systems, the structure used in this invention is simpler, saving production costs and reducing equipment complexity. Continuous production line operation also eliminates the need to reset temperature parameters, shortening the time interval between two production cycles and improving production efficiency.

[0047] (2) The low-pressure environment of this invention can not only improve the evaporation efficiency of the solvent and reduce the temperature requirements during the production process, but also continuously maintain the pressure gradient at the interface between the liquid and gas phases above the catalyst layer, providing a continuous driving force for the diffusion of solvent vapor. In summary, low-pressure and vacuum conditions can greatly improve production efficiency.

[0048] (3) The heat conduction heating technology in this invention can rapidly heat up the catalyst ink, causing the solvent on the surface to evaporate and diffuse quickly; the microwave technology can enable polar molecules (water molecules) to acquire a large amount of energy in a short time, assisting them to diffuse out of the pores in the particle network. The combination of the two drying technologies significantly reduces the duration of the entire drying process, improves production efficiency, and allows for flexible control of process parameters, enabling the creation of suitable drying processes for different catalyst inks.

[0049] (4) Secondary pores and micropores are easily generated in the catalyst particle network during the later stages of drying. These morphological defects may lead to larger defects, such as cracks, fractures, or delamination, due to the conflict between the stress inside the catalyst layer (tensile stress generated by capillary force concentration) and the adhesion provided by the substrate. The present invention uses microwave heating instead of heat conduction heating in the later stages of drying, which enables the residual water molecules inside the entire catalyst layer to gain kinetic energy at a near-synchronous rate, allowing them to quickly diffuse and escape from the pores. This weakens the adverse effects of the capillary force generated by water in the catalyst particle network during the later stages of drying and can effectively improve the quality of the finished product. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the overall structure of the step-by-step drying production line of the present invention in Example 1.

[0051] Figure 2 This is a schematic diagram of the vacuum unit structure of the step-by-step drying production line of the present invention in Example 1.

[0052] Figure 3 This is a schematic diagram of the low-pressure heat conduction drying unit in the first half of the step-by-step production line of the present invention in Example 1.

[0053] Figure 4 This is a schematic diagram of the vacuum microwave drying unit in the second half of the step-by-step production line of the present invention in Example 1.

[0054] Numbering on the map:

[0055] 1-Conveying unit, 101-Pulley, 102-Tensioning wheel, 103-Conveyor belt, 104-Servo motor, 105-Control panel, 106-Support structure, 107-Feeding inlet ramp, 108-Discharge inlet ramp, 2-Bottom heating device, 201-Graphite heating plate, 202-Temperature controller, 3-Microwave heating device, 301-Magnetron, 302-Waveguide, 303-Microwave stirrer, 4-Drying chamber, 401-Low-pressure chamber, 402-Vacuum chamber, 403-Modible partition, 404-Sealed chamber door, 5-Vacuum unit, 501-Vacuum pump, 502-Three-way solenoid valve, 503-Manifold, 5031-First manifold branch, 5032-Second manifold branch, 5033-Third manifold branch, 5034-Fourth manifold branch. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0057] Unless otherwise specified in this technical solution, the component model, material name, connection structure, control method, and other features are considered to be common technical features disclosed in the prior art.

[0058] In the description of this invention, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0059] In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integrated connection; they can refer to a bolted connection or a welded connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0060] To improve the production efficiency of catalyst layers, reduce product defects, enhance the automation level of catalyst layer production, and achieve a programmable and widely applicable process, this invention provides a stepwise drying production line for fuel cell catalyst layer preparation. The structure of this line is described in [reference needed]. Figures 1 to 4 As shown, it includes:

[0061] The conveying unit 1 controls the movement of the catalyst ink, and the low-pressure heat conduction drying unit and the vacuum microwave drying unit are arranged sequentially along the direction of the catalyst ink movement and are respectively located below and above the conveying unit 1, and the vacuum unit 5 is located above the low-pressure heat conduction drying unit and the vacuum microwave drying unit and is used to control the pressure inside the low-pressure heat conduction drying unit and the vacuum microwave drying unit.

[0062] The low-pressure heat conduction drying unit includes a bottom heating device 2, a low-pressure chamber 401 located above the bottom heating device 2, and a first manifold branch 5031 connected to the low-pressure chamber 401. The first manifold branch 5031 is connected to the vacuum unit 5.

[0063] The vacuum microwave drying unit includes a vacuum chamber 402 connected to a low-pressure chamber 401, a microwave heating device 3 located above the vacuum chamber 402 and used for vacuum microwave drying of catalyst ink, and a second manifold branch 5032 connected to the vacuum chamber 402, the second manifold branch 5032 being connected to the vacuum unit 5.

[0064] During operation, the catalyst ink passes through the low-pressure chamber 401 and the vacuum chamber 402 under the action of the conveying unit 1. The bottom heating device 2 heats the catalyst ink in the low-pressure chamber 401 under low pressure, and the microwave heating device 3 dries the catalyst ink in the vacuum chamber 402 under vacuum microwave.

[0065] To separately control the pressure of the low-pressure chamber 401 and the vacuum chamber 402, a vacuum pump 501 is installed to evacuate them. A three-way solenoid valve 502 is connected to the vacuum chamber 402, the low-pressure chamber 401, and the outside air. The three-way solenoid valve 502 controls the opening and closing of the gas pipeline and works in conjunction with the vacuum pump 501 to control the pressure of the low-pressure chamber 401 and the vacuum chamber 402. The specific settings are as follows:

[0066] For some specific implementation methods, please refer to [link / reference]. Figure 1 and Figure 2 As shown, the vacuum unit 5 includes a vacuum pump 501, a three-way electronic valve 502 connected to the vacuum pump 501, and a manifold 503 located on the three-way electronic valve 502.

[0067] The manifold 503 includes a first manifold branch 5031, a second manifold branch 5032, a third manifold branch 5033 connected to the outlet of the vacuum pump 501, and a fourth manifold branch 5034 connected to air.

[0068] The vacuum pump 501 controls the pressure of the low-pressure chamber 401 and the vacuum chamber 402 through the first manifold branch 5031 and the second manifold branch 5032 respectively.

[0069] The three-way electronic valve 502 controls the opening and closing of the first manifold branch 5031, the second manifold branch 5032, the third manifold branch 5033, and the fourth manifold branch 5034.

[0070] The three-way electronic valve controls the opening and closing of the first manifold branch, the second manifold branch, the third manifold branch, and the fourth manifold branch.

[0071] When the fourth manifold branch 5034 is closed and the first manifold branch 5031, the second manifold branch 5032, and the third manifold branch 5033 are connected, the pressure of the drying chamber can be controlled.

[0072] When the fourth manifold branch 5034, the first manifold branch 5031, and the second manifold branch 5032 are opened, and the third manifold branch 5033 is closed, the drying chamber can be depressurized.

[0073] To achieve precise control of the low-pressure heat conduction drying unit, a temperature controller 202 is provided to allow several groups of graphite heating plates 201 to operate at different heating temperatures. The specific settings are as follows:

[0074] For some specific implementation methods, please refer to [link / reference]. Figure 1 and Figure 3As shown, the bottom heating device 2 includes several graphite heating plates 201 and a temperature controller 202 connected to the graphite heating plates 201. The graphite heating plates 201 can be set to different temperatures.

[0075] In a preferred embodiment of the present invention, three sets of graphite heating plates 201 are provided, each set being wire-connected to a temperature controller 202. The temperatures of the three sets of graphite heating plates 201 should be set to a low-high-low or low-medium-high state to achieve a gradual change from room temperature to high temperature during the bottom heating and drying process, which is beneficial to the conversion of catalyst ink to catalyst gel. Furthermore, in the low-pressure heat conduction drying unit, two temperature gradients are achieved: an in-situ temperature gradient from room temperature to high temperature within any region of the catalyst ink, and a temperature difference gradient between any two adjacent regions of the catalyst ink. This ensures that at any time and at any location, there will be no uneven movement of particles due to local temperature differences, thereby preventing defects such as tearing, breakage, and pores in the catalyst particle network structure.

[0076] To achieve precise control of the vacuum microwave drying unit, magnetron 301 is configured to generate a microwave field within the vacuum chamber 402 to achieve uniform vacuum microwave drying of the catalyst gel. The specific settings are as follows:

[0077] For some specific implementation methods, please refer to [link / reference]. Figure 1 and Figure 4 As shown, the microwave heating device 3 includes a magnetron 301 located on the inner wall of the vacuum chamber 402 for generating high-frequency microwaves, a waveguide 302 connected to the magnetron for transmitting high-frequency microwaves to the vacuum chamber 402, and a microwave stirrer 303 located next to the waveguide 302 for averaging high-frequency microwaves.

[0078] The microwave stirrer 303 is equipped with rotatable metal refractive blades.

[0079] The magnetron 301 can continuously generate high-frequency microwaves and couple them to the vacuum chamber 402 through the waveguide 302, guiding the microwaves to the microwave stirrer 303 with extremely low loss. The rotation of the metal refractive blades of the microwave stirrer 303 enables the periodic change of the load on the magnetron 301, resulting in a large frequency pull. At the same time, the periodic change of the refractive effect of the blades can continuously change the excitation state of the coupling port. The combination of these two effects improves the uniformity of the microwave field distribution inside the vacuum chamber 402, causing the residual polar solvent molecules in the catalyst particle network, mainly non-volatile water molecules, to oscillate rapidly at extremely high frequencies.

[0080] In the microwave field, residual polar solvent molecules gain enormous energy and heat up, diffusing out of the pores through molecular thermal motion, rapidly removing residual moisture from the particle network. The microwave drying stage should not last too long to avoid water molecules with high kinetic energy damaging the catalyst particle network.

[0081] At this point, the body of the preferred vacuum chamber 402, the sealed chamber door 404, and the movable partition 403 are made of stainless steel, which can effectively reflect microwaves.

[0082] Considering the varying lengths of different catalyst inks, the movable partition 403 is designed to be mobile. This allows catalyst inks of different lengths to be dried in this step-by-step drying line. The specific settings are as follows:

[0083] For some specific implementation methods, please refer to [link / reference]. Figure 1 As shown, a movable partition 403 is provided between the low-pressure chamber 401 and the vacuum chamber 402. The low-pressure chamber 401, the movable partition 403, and the vacuum chamber 402 are connected in sequence to form a drying chamber 4. The movable partition 403 is movable, can be opened and closed, and is arranged in the drying chamber 4 perpendicular to the direction of travel of the catalyst ink.

[0084] To ensure that the catalyst gel in the vacuum microwave drying unit is completely inside the vacuum chamber 402, the following settings are adopted:

[0085] For more detailed implementation methods, please refer to [link / reference]. Figure 1 As shown, the length of the vacuum chamber 402 is at least longer than the length of the catalyst ink.

[0086] Considering the issue of transporting the catalyst ink to the final catalyst layer, the following settings are adopted:

[0087] For more detailed implementation methods, please refer to [link / reference]. Figure 1 As shown, a sealed chamber door 404 for discharging catalyst ink is provided at one end of the vacuum chamber 402 away from the movable partition 403.

[0088] Considering the precise control of the fine catalyst ink's journey through the low-pressure drying unit and the vacuum microwave drying unit, the following settings are adopted:

[0089] For some specific implementation methods, please refer to [link / reference]. Figure 1 As shown, the conveying unit 1 includes a conveyor belt 103 for placing catalyst ink, a support structure 106 located below the conveyor belt 103 and for supporting the conveyor belt, a plurality of pulleys 101 located at both ends of the conveyor belt, a plurality of tensioning pulleys 102 located below the conveyor belt 103 and for tensioning the conveyor belt 103, and a plurality of servo motors 104 for controlling the operation of the pulleys 101.

[0090] The servo motor 104 is equipped with a control panel 105 for programmable control of start / stop and speed.

[0091] In a preferred embodiment of the present invention, two pulleys and two tensioning pulleys are provided.

[0092] Considering the feeding of the catalyst ink and the escape of the catalyst layer, the following settings are adopted:

[0093] For more detailed implementation methods, please refer to [link / reference]. Figure 1 As shown, the two ends of the conveying unit 1 are also provided with a feed port ramp 107 for facilitating the conveying of catalyst ink and a discharge port ramp 108 for preventing the catalyst ink from escaping.

[0094] The present invention also provides a method for using a stepwise drying production line for the preparation of catalyst layers for fuel cells, comprising the following steps:

[0095] S1: Place the catalyst ink on the feed inlet ramp 107. The control panel 105 controls the servo motor 104 to drive the conveyor belt 103 to start running. At this time, the movable partition 403 is in the open state, the vacuum pump 501 is turned on, the three-way electronic valve 502 controls the fourth manifold branch 5034 to close and the first manifold branch 5031 and the third manifold branch 5033 to connect. At this time, the low-pressure chamber 401 is in a low-pressure state.

[0096] S2: The catalyst ink runs in the low-pressure chamber 401, and the graphite heating plate 201 is set to different temperatures to heat the catalyst ink and transform it into catalyst gel.

[0097] S3: The catalyst gel arrives at the vacuum chamber 402. At this time, the movable partition 403 is closed, and the second manifold branch and the third manifold branch remain connected. The vacuum pump 501 evacuates the vacuum chamber 402 to a vacuum state. The magnetron 301, together with the microwave stirrer 303, performs vacuum microwave drying on the catalyst gel in the vacuum chamber 402. Then the catalyst gel is converted into a dried and shaped catalyst layer. After drying is completed, the sealed chamber door 404 is opened, and the conveyor belt 103 sends out the substrate.

[0098] S4: Then the servo motor 104 is turned off, the conveyor belt 103 stops, the vacuum pump 501 is turned off, the three-way electronic valve 502 controls the third manifold branch 5033 to close, the fourth manifold branch 5034 to open, the movable partition opens, and both the low-pressure chamber 401 and the vacuum chamber 402 return to normal atmospheric pressure.

[0099] Each of the above implementation methods can be implemented individually, or in any combination of two or more.

[0100] The above implementation methods will be described in more detail below with reference to specific embodiments.

[0101] Example 1

[0102] To improve the production efficiency of catalyst layers, reduce product defects, enhance the automation level of catalyst layer production, and achieve a programmable and widely applicable process, this invention provides a stepwise drying production line for fuel cell catalyst layer preparation. The structure of this line is described in [reference needed]. Figures 1 to 4 As shown, it includes:

[0103] The conveying unit 1 controls the movement of the catalyst ink, and the low-pressure heat conduction drying unit and the vacuum microwave drying unit are arranged sequentially along the direction of the catalyst ink movement and are respectively located below and above the conveying unit 1, and the vacuum unit 5 is located above the low-pressure heat conduction drying unit and the vacuum microwave drying unit and is used to control the pressure inside the low-pressure heat conduction drying unit and the vacuum microwave drying unit.

[0104] The low-pressure heat conduction drying unit includes a bottom heating device 2, a low-pressure chamber 401 located above the bottom heating device 2, and a first manifold branch 5031 connected to the low-pressure chamber 401. The first manifold branch 5031 is connected to the vacuum unit 5.

[0105] The vacuum microwave drying unit includes a vacuum chamber 402 connected to a low-pressure chamber 401, a microwave heating device 3 located above the vacuum chamber 402 for vacuum microwave drying of catalyst ink, and a second manifold branch 5032 connected to the vacuum chamber 402 and connected to the vacuum unit 5.

[0106] During operation, the catalyst ink passes through the low-pressure chamber 401 and the vacuum chamber 402 under the action of the conveying unit 1. The bottom heating device 1 heats the catalyst ink in the low-pressure chamber 401 under low pressure, and the microwave heating device 3 dries the catalyst ink in the vacuum chamber 402 under vacuum microwave.

[0107] To separately control the pressure of the low-pressure chamber 401 and the vacuum chamber 402, a vacuum pump 501 is installed to evacuate them. A three-way electronic valve 502 is connected to the vacuum chamber 402, the low-pressure chamber 401, and the outside air. The three-way electronic valve 502 controls the opening and closing of the gas pipeline and works in conjunction with the vacuum pump 501 to control the pressure of the low-pressure chamber 401 and the vacuum chamber 402. The specific settings are as follows:

[0108] Please see again. Figure 1 and Figure 2 As shown, the vacuum unit 5 includes a vacuum pump 501, a three-way electronic valve 502 connected to the vacuum pump 501, and a manifold 503 located on the three-way electronic valve 502.

[0109] Manifold 503 includes a first manifold branch 5031, a second manifold branch 5032, a third manifold branch 5033 connected to the outlet of vacuum pump 501, and a fourth manifold branch 5034 connected to air.

[0110] Vacuum pump 501 controls the pressure of low-pressure chamber 401 and vacuum chamber 402 through first manifold branch 5031 and second manifold branch 5032 respectively.

[0111] The three-way electronic valve 502 controls the opening and closing of the first manifold branch 5031, the second manifold branch 5032, the third manifold branch 5033, and the fourth manifold branch 5034.

[0112] The three-way electronic valve controls the opening and closing of the first manifold branch, the second manifold branch, the third manifold branch, and the fourth manifold branch.

[0113] When the fourth manifold branch 5034 is closed and the first manifold branch 5031, the second manifold branch 5032, and the third manifold branch 5033 are connected, the pressure of the drying chamber can be controlled.

[0114] When the fourth manifold branch 5034, the first manifold branch 5031, and the second manifold branch 5032 are opened, and the third manifold branch 5033 is closed, the drying chamber can be depressurized.

[0115] To achieve precise control of the low-pressure heat conduction drying unit, a temperature controller 202 is provided to allow several groups of graphite heating plates 201 to operate at different heating temperatures. The specific settings are as follows:

[0116] Please see again. Figure 1 and Figure 3 As shown, the bottom heating device 2 includes several graphite heating plates 201 and a temperature controller 202 connected to the graphite heating plates 201. The graphite heating plates 201 can be set to different temperatures.

[0117] In a preferred embodiment of the present invention, three sets of graphite heating plates 201 are provided, each set being wire-connected to a temperature controller 202. The temperatures of the three sets of graphite heating plates 201 should be set to a low-high-low or low-medium-high state to achieve a gradual change from room temperature to high temperature during the bottom heating and drying process, which is beneficial to the conversion of catalyst ink to catalyst gel. Furthermore, in the low-pressure heat conduction drying unit, two temperature gradients are achieved: an in-situ temperature gradient from room temperature to high temperature within any region of the catalyst ink, and a temperature difference gradient between any two adjacent regions of the catalyst ink. This ensures that at any time and at any location, there will be no uneven movement of particles due to local temperature differences, thereby preventing defects such as tearing, breakage, and pores in the catalyst particle network structure.

[0118] To achieve precise control of the vacuum microwave drying unit, magnetron 301 is configured to generate a microwave field within the vacuum chamber 402 to achieve uniform vacuum microwave drying of the catalyst gel. The specific settings are as follows:

[0119] Please see again. Figure 1 and Figure 4 As shown, the microwave heating device 3 includes a magnetron 301 located on the inner wall of the vacuum chamber 402 for generating high-frequency microwaves, a waveguide 302 connected to the magnetron for transmitting high-frequency microwaves to the vacuum chamber 402, and a microwave stirrer 303 located next to the waveguide 302 for averaging high-frequency microwaves.

[0120] The microwave stirrer 303 is equipped with rotatable metal refractive blades.

[0121] The magnetron 301 can continuously generate high-frequency microwaves and couple them to the vacuum chamber 402 through the waveguide 302, guiding the microwaves to the microwave stirrer 303 with extremely low loss. The rotation of the metal refractive blades of the microwave stirrer 303 enables the periodic change of the load on the magnetron 301, resulting in a large frequency pull. At the same time, the periodic change of the refractive effect of the blades can continuously change the excitation state of the coupling port. The combination of these two effects improves the uniformity of the microwave field distribution inside the vacuum chamber 402, causing the residual polar solvent molecules in the catalyst particle network, mainly non-volatile water molecules, to oscillate rapidly at extremely high frequencies.

[0122] In the microwave field, residual polar solvent molecules gain enormous energy and heat up, diffusing out of the pores through molecular thermal motion, rapidly removing residual moisture from the particle network. The microwave drying stage should not last too long to avoid water molecules with high kinetic energy damaging the catalyst particle network.

[0123] At this point, the body of the preferred vacuum chamber 402, the sealed chamber door 404, and the movable partition 403 are made of stainless steel, which can effectively reflect microwaves.

[0124] Considering the varying lengths of different catalyst inks, the movable partition 403 is designed to be mobile. This allows catalyst inks of different lengths to be dried in this step-by-step drying line. The specific settings are as follows:

[0125] Please see again. Figure 1 As shown, a movable partition 403 is provided between the low-pressure chamber 401 and the vacuum chamber 402. The low-pressure chamber 401, the movable partition 403, and the vacuum chamber 402 are connected in sequence to form a drying chamber 4. The movable partition 403 is movable, can be opened and closed, and is arranged in the drying chamber 4 perpendicular to the direction of travel of the catalyst ink.

[0126] To ensure that the catalyst gel in the vacuum microwave drying unit is completely inside the vacuum chamber 402, the following settings are adopted:

[0127] Please see again. Figure 1 As shown, the length of the vacuum chamber 402 is at least longer than the length of the catalyst ink.

[0128] Considering the issue of transporting the catalyst ink to the final catalyst layer, the following settings are adopted:

[0129] For more detailed implementation methods, please refer to [link / reference]. Figure 1 As shown, a sealed chamber door 404 for discharging catalyst ink is provided at one end of the vacuum chamber 402 away from the movable partition 403.

[0130] Considering the precise control of the fine catalyst ink's journey through the low-pressure drying unit and the vacuum microwave drying unit, the following settings are adopted:

[0131] Please see again. Figure 1 As shown, the conveying unit 1 includes a conveyor belt 103 for placing catalyst ink, a support structure 106 located below the conveyor belt 103 for supporting the conveyor belt, a plurality of pulleys 101 located at both ends of the conveyor belt, a plurality of tensioning pulleys 102 located below the conveyor belt 103 for tensioning the conveyor belt 103, and a plurality of servo motors 104 for controlling the operation of the pulleys 101.

[0132] The servo motor 104 is equipped with a control panel 105 for programmable control of start / stop and speed.

[0133] The system includes two pulleys and two tensioning pulleys.

[0134] Considering the feeding of the catalyst ink and the escape of the catalyst layer, the following settings are adopted:

[0135] Please see again. Figure 1 As shown, the two ends of the conveying unit 1 are also provided with a feed port ramp 107 for facilitating the conveying of catalyst ink and a discharge port ramp 108 for preventing the catalyst ink from escaping.

[0136] The present invention also provides a method for using a stepwise drying production line for the preparation of catalyst layers for fuel cells, comprising the following steps:

[0137] S1: Place the catalyst ink on the feed inlet ramp 107. The control panel 105 controls the servo motor 104 to drive the conveyor belt 103 to start running. At this time, the movable partition 403 is in the open state, the vacuum pump 501 is turned on, the three-way electronic valve 502 controls the fourth manifold branch 5034 to close and the first manifold branch 5031 and the third manifold branch 5033 to connect. At this time, the low-pressure chamber 401 is in a low-pressure state.

[0138] S2: The catalyst ink runs in the low-pressure chamber 401, and the graphite heating plate 201 is set to different temperatures to heat the catalyst ink and transform it into catalyst gel.

[0139] S3: The catalyst gel arrives at the vacuum chamber 402. At this time, the movable partition 403 is closed, and the second manifold branch 5032 and the third manifold 5033 branch remain connected. The vacuum pump 501 evacuates the vacuum chamber 402 to a vacuum state. The magnetron 301, together with the microwave stirrer 303, performs vacuum microwave drying on the catalyst gel in the vacuum chamber 402. Then, the catalyst gel is converted into a dried and shaped catalyst layer. After drying, the sealed chamber door 404 is opened, and the conveyor belt 103 sends out the substrate.

[0140] S4: Then the servo motor 104 is turned off, the conveyor belt 103 stops, the vacuum pump 501 is turned off, the three-way electronic valve 502 controls the third manifold branch 5033 to close, the fourth manifold branch 5034 to open, the movable partition 403 opens, and both the low-pressure chamber 401 and the vacuum chamber 402 return to normal atmospheric pressure.

[0141] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A stepwise drying apparatus for the preparation of a catalytic layer of a fuel cell, characterized in that, The application relates to a catalyst ink drying device. The device comprises a conveying unit (1) for controlling catalyst ink movement, a low-pressure heat conduction drying unit and a vacuum microwave drying unit arranged in sequence along the catalyst ink movement direction and located below and above the conveying unit (1) respectively, and a vacuum unit (5) located above the low-pressure heat conduction drying unit and the vacuum microwave drying unit and used for controlling the pressure in the low-pressure heat conduction drying unit and the vacuum microwave drying unit. The low-pressure heat conduction drying unit comprises a bottom heating device (2), a low-pressure bin (401) located above the bottom heating device (2), and a first manifold branch (5031) connected with the low-pressure bin (401), wherein the first manifold branch (5031) is connected with the vacuum unit (5). The vacuum microwave drying unit comprises a vacuum bin (402) located behind the low-pressure bin (401), a microwave heating device (3) located above the vacuum bin (402) and used for vacuum microwave drying of catalyst ink, and a second manifold branch (5032) connected with the vacuum bin (402), wherein the second manifold branch (5032) is connected with the vacuum unit (5). The catalyst ink passes through the low-pressure bin (401) in a low-pressure state and the vacuum bin (402) in a vacuum state under the action of the conveying unit (1), the bottom heating device (2) performs low-pressure heating on the catalyst ink in the low-pressure bin (401), and the microwave heating device (3) performs vacuum microwave drying on the catalyst ink in the vacuum bin (402). The vacuum unit (5) comprises a vacuum pump (501), a three-way electronic valve (502) connected with the vacuum pump (501), and a manifold (503) located on the three-way electronic valve (502). The manifold (503) comprises a first manifold branch (5031), a second manifold branch (5032), a third manifold branch (5033) connected with the outlet of the vacuum pump (501), and a fourth manifold branch (5034) connected with air. The vacuum pump (501) controls the pressure of the low-pressure bin (401) and the vacuum bin (402) through the first manifold branch (5031) and the second manifold branch (5032) respectively. The three-way electronic valve (502) controls the opening and closing of the first manifold branch (5031), the second manifold branch (5032), the third manifold branch (5033) and the fourth manifold branch (5034). An activity partition (403) is further arranged between the low-pressure bin (401) and the vacuum bin (402), the low-pressure bin (401), the activity partition (403) and the vacuum bin (402) are sequentially connected to form a drying bin (4), the activity partition (403) is movable, openable and closable, and is arranged in the drying bin (4) perpendicular to the catalyst ink movement direction.

2. The apparatus according to claim 1, wherein The bottom heating device (2) comprises a plurality of graphite heating plates (201) and a temperature controller (202) connected with the graphite heating plates (201), and the graphite heating plates (201) can be set to different temperatures.

3. The apparatus according to claim 1, wherein The microwave heating device (3) includes a magnetron (301) located on the inner wall of the vacuum chamber (402) for generating high-frequency microwaves, a waveguide (302) connected to the magnetron for transmitting high-frequency microwaves to the vacuum chamber (402), and a microwave stirrer (303) located next to the waveguide (302) for averaging high-frequency microwaves. The microwave stirrer (303) is equipped with rotatable metal refractive blades.

4. The apparatus according to claim 1, wherein The length of the vacuum chamber (402) is at least longer than the length of the catalyst ink.

5. The apparatus for the stepwise drying of a catalytic layer for a fuel cell according to claim 1, wherein A sealed chamber door (404) for discharging catalyst ink is provided at one end of the vacuum chamber (402) away from the movable partition (403).

6. The apparatus for the stepwise drying of a catalytic layer for a fuel cell according to claim 1, wherein The conveying unit (1) includes a conveyor belt (103) for placing catalyst ink, a support structure (106) located below the conveyor belt (103) and for supporting the conveyor belt, a plurality of pulleys (101) located at both ends of the conveyor belt, a plurality of tensioning pulleys (102) located below the conveyor belt (103) and for tensioning the conveyor belt (103), and a plurality of servo motors (104) for controlling the operation of the pulleys (101).

7. The apparatus for the stepwise drying of a catalytic layer for a fuel cell according to claim 6, characterized in that The two ends of the conveying unit (1) are also provided with a feed inlet ramp (107) for facilitating the conveying of catalyst ink, and a discharge inlet ramp (108) for conveying the dried catalyst layer.

8. A method of using a stepwise drying apparatus for the preparation of a catalytic layer for a fuel cell according to any one of claims 1 to 7, characterized in that Includes the following steps: S1: The catalyst ink is coated on the substrate and placed into the feed inlet ramp (107). The conveyor belt (103) starts running. At this time, the movable partition (403) is in the open state, the vacuum pump (501) is turned on, the three-way electronic valve (502) controls the fourth manifold branch (5034) to close and the first manifold branch (5031) and the third manifold branch (5033) to connect. At this time, the low pressure chamber (401) is in a low pressure state. S2: The catalyst ink runs in the low-pressure chamber (401), and the graphite heating plate (201) is set to different temperatures to heat the catalyst ink and transform it into catalyst gel; S3: The catalyst gel arrives at the vacuum chamber (402). At this time, the movable partition (403) is closed, and the second manifold branch (5032) and the third manifold branch (5033) remain connected. The vacuum pump (501) evacuates the vacuum chamber (402) to a vacuum state. The magnetron (301) works with the microwave stirrer (303) to perform vacuum microwave drying on the catalyst gel in the vacuum chamber (402). Then the catalyst gel is converted into a dried and shaped catalyst layer. After drying, the sealed chamber door (404) is opened, and the conveyor belt (103) sends out the substrate. S4: Then the servo motor (104) is turned off, the conveyor belt (103) stops, the vacuum pump (501) is turned off, the three-way electronic valve (502) controls the third manifold branch (5033) to close, the fourth manifold branch (5034) is turned on, the movable partition (403) is opened, and the low-pressure chamber (401) and the vacuum chamber (402) are both restored to normal atmospheric pressure.

Images