Silicon-based transmission layer and application thereof

Abstract

The invention relates to the field of porous transmission layer manufacturing, and discloses a silicon-based transmission layer and application thereof.The silicon-based transmission layer comprises at least one silicon-based material, and the silicon-based material is made of a doped conductive crystalline silicon material; wherein the silicon-based material comprises a first surface and a second surface, and a plurality of through channels for transmission are arranged between the first surface and the second surface; the first surface or the second surface is used for being in contact with a pole plate stack provided with a transverse transmission flow field; the silicon-based material preferably adopts a silicon wafer; the problems that a titanium fiber diffusion layer and a carbon fiber gas diffusion layer are large in gas-liquid transmission resistance, poor in electric conduction and heat conduction performance and low in mechanical strength are solved; as the crystalline silicon material has very high chemical stability, the crystalline silicon material can stably work in a strongly acidic, high-potential and high-oxidability environment in a PEM fuel cell or a PEM electrolysis device.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing porous transport layers, and particularly relates to a silicon-based transport layer and its application. Background Art

[0002] Porous Transport Layers (PTL) can be widely applied in fields such as mass transfer, heat transfer, momentum transfer, and electron transport. When it is applied in fuel cells (stacks) and electrolysis devices (commonly also known as "electrolyzers"), the porous transport layer is usually referred to as the "Gas Diffusion Layer" (GDL), which plays multiple important roles such as supporting the proton exchange membrane, collecting current, conducting reactants and discharging reaction products, and transferring heat. The function of the gas diffusion layer not only lies in the fact that gas can diffuse therein, but also that it can transport all fluid substances in the stack under the drive of pressure drop to maintain the electrochemical reactions in the fuel cell stack and electrolyzer.

[0003] In existing fuel cells (mainly hydrogen fuel cells), the cathode gas diffusion layer (i.e., the gas diffusion layer stacked in contact with the cathode plate) or the anode gas diffusion layer (i.e., the gas diffusion layer stacked in contact with the anode plate) are usually made of randomly bonded carbon fibers; the cathode gas diffusion layer of the electrolysis device generally also uses carbon fibers. Since the anode of the electrolysis device needs to work in a strongly acidic, high-potential, and highly oxidizing environment, the electrochemical stability requirements for the gas diffusion layer are very high. Therefore, the anode gas diffusion layer of the electrolysis device generally uses a titanium fiber felt plated with precious metals (abbreviated as "titanium felt"); at the same time, in order to produce high-pressure hydrogen, the stacking pressure of the electrolysis device is relatively high, and the fluid pressure difference on both sides of the internal membrane structure (usually a PEM membrane, meaning proton exchange membrane in Chinese) is also very high, requiring the gas diffusion layer to have high mechanical strength. Finally, the gas diffusion layer also needs to play the roles of conducting electricity, conducting heat, and transporting gas and liquid in the electrolysis device, so the physical properties of the gas diffusion layer are also required to be very high.

[0004] The anode titanium fiber felt in a conventional electrolysis device is woven from titanium fibers with a diameter of 10 - 50 microns. The titanium felt has a certain mechanical strength and toughness, and can play a certain supporting role for the membrane electrode. At the same time, the titanium felt has the functions of electrical conductivity, heat conduction, and gas-liquid transmission, and can meet the basic requirements. However, since the titanium felt is woven from titanium fibers, the span gap between the fibers is relatively large, and the supporting effect on the membrane electrode at the gap is limited, and the resistance to providing charge to the membrane electrode is also relatively large. Therefore, the performance and even durability of the electrolysis device are limited. Moreover, titanium is easily oxidized and corroded in an environment of strong acidity, high potential, and high oxidizing property at the anode. The generated oxide layer not only increases the ohmic resistance and causes increased internal consumption, but the precipitated ions also reduce the catalyst activity. For this reason, the common practice in the PEM electrolyzed water industry is to coat a layer of precious metals (such as platinum and iridium) on the surface of the titanium felt, which is not only costly, but also difficult to ensure the density and uniformity of the coating technically.

[0005] The cathode gas diffusion layer, anode gas diffusion layer in a conventional fuel cell stack, and the cathode gas diffusion layer of an electrolysis device are usually woven from carbon fibers with a diameter of about 8 μm (microns). The carbon fiber gas diffusion layer has a certain mechanical strength and toughness, but under the stacking pressure, the carbon fiber gas diffusion layer deforms or even breaks in the plate channel, and the ability to support the pressure difference on both sides of the proton exchange membrane is also limited.

[0006] In addition, whether it is a titanium fiber gas diffusion layer or a carbon fiber gas diffusion layer, they are both woven from fibers. Gas-liquid transmission can only be carried out through the random gaps between the fibers. The mass transfer path is tortuous, the shape and size uniformity are poor, the mass transfer resistance is large, and there are defects such as large ohmic resistance and small thermal conductivity.

[0007] Therefore, the applicant hopes to seek a technical solution to solve some technical defects existing in the gas diffusion layers used in fuel cells and electrolysis devices in the prior art. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a silicon-based transport layer and its application, which solves the problems of large gas-liquid transport resistance, poor electrical and thermal conductivity, and low mechanical strength existing in the titanium felt and carbon fiber gas diffusion layer. Since the crystalline silicon material has high chemical stability, it can work stably in an environment of strong acidity, high potential, and high oxidizing property in a PEM fuel cell or a PEM electrolysis device.

[0009] A silicon-based transport layer includes at least one silicon-based material, and the silicon-based material is made of doped conductive crystalline silicon material. Wherein, the silicon-based material includes a first surface and a second surface, and a plurality of through channels for transporting fluid are provided between the first surface and the second surface. And the first surface or the second surface is used for stacking contact with a plate provided with a transverse transport flow field. The silicon-based material is preferably a silicon wafer.

[0010] Preferably, the silicon-based material is a silicon wafer, and the through-channel includes a perforation; wherein, the perforation refers to a hole structure formed through the silicon wafer on the silicon wafer.

[0011] Preferably, the hole structure is formed on the silicon wafer by physical and / or chemical methods; the hole structure is circular or non-circular on the first surface or the second surface; the hole structure is a straight through-hole or a non-straight through-hole; the porosity of the hole structure in the silicon wafer is 0.1-0.9; the pore diameter of the hole structure on the first surface or the second surface is 10-1000 microns; the pore diameter of the hole structure on the first surface is equal to or not equal to the pore diameter of the hole structure on the second surface.

[0012] Preferably, the pore diameter of the hole structure on the first surface is smaller than the pore diameter of the hole structure on the second surface, and the second surface is used for stacked contact with the plate provided with a transverse transport flow field.

[0013] Preferably, the through-channel includes a window lattice; wherein, by respectively arranging a cross-shaped first channel and a second channel on the first surface and the second surface of the silicon-based material, and a through-hole-shaped window lattice is formed at the intersection of the first channel and the second channel; the first channel is formed by physical and / or chemical methods; the second channel is formed by physical and / or chemical methods; wherein, the depth of the first channel is equal to or not equal to the depth of the second channel; the duty cycle of the first channel on the first surface is equal to or not equal to the duty cycle of the second channel on the second surface.

[0014] Preferably, the depth of the first channel is smaller than the depth of the second channel, and the duty cycle of the first channel on the first surface is smaller than the duty cycle of the second channel on the second surface, and the second surface is used for stacked contact with the plate provided with a transverse transport flow field.

[0015] Preferably, the channel provided on the first surface or the second surface in stacked contact with the plate simultaneously serves as a transverse transport flow field to realize the function of the plate.

[0016] Preferably, the bulk resistivity of the silicon-based material is not greater than 0.1 ohm-cm; the thickness range of the silicon-based material is 0.01-10 mm, more preferably 0.03-0.5 mm; the first surface is a smooth surface or a matte surface; the second surface is a smooth surface or a matte surface.

[0017] Preferably, the silicon-based material is formed by sintering granular crystalline silicon.

[0018] Preferably, an application of a silicon-based transport layer uses the silicon-based transport layer described above as a porous transport layer of a fuel cell or an electrolysis device; wherein, the first surface or the second surface of the silicon-based material is used for stacked contact with a plate provided with a transverse transport flow field.

[0019] Preferably, the fuel cell includes a plurality of stacked fuel cell units, wherein a single fuel cell unit includes a plate provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the plate is an anode plate, a cathode plate, or a bipolar plate; the silicon-based transport layer is located between the plate and the catalyst, and the first surface or the second surface is in stacked contact with the plate, and the other surface is in stacked contact with the catalyst; The electrolysis device includes a plurality of stacked electrolysis units, wherein a single electrolysis unit includes a plate provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the plate is an anode plate, a cathode plate, or a bipolar plate; the silicon-based transport layer is located between the plate and the catalyst, and the first surface or the second surface is in stacked contact with the plate, and the other surface is in stacked contact with the catalyst.

[0020] Preferably, the silicon-based transport layers in each fuel cell unit or each electrolysis unit are the same or different in material or structure.

[0021] The present invention breaks the thinking prejudice of the existing fiber felt structure obtained by fiber weaving as a porous transport layer (usually referred to as a "gas diffusion layer"), and proposes to use a doped conductive crystalline silicon material to make the main framework of the silicon-based transport layer. First of all, crystalline silicon materials have high chemical durability, high mechanical strength, high electrical conductivity, high thermal conductivity, good flatness, good thickness uniformity and consistency, a production process suitable for large-scale production, and a wide range of material supply sources without restrictions; more importantly, the present application provides a number of through channels in the silicon-based transport layer, so that gases and liquids can be transported from the first surface of the silicon-based transport layer to the second surface, or from the second surface of the silicon-based transport layer to the first surface, thereby achieving the expected gas and liquid transport effects. Further, the through channels of the present application are provided on the main framework of the porous transport layer and are formed by physical and / or chemical methods. In subsequent applications, the through channels provide an efficient transport path for the fluid substances in the fuel cell stack or the electrolysis device, and the transport distance of reactants and products can be shortened to the greatest extent by controlling the structure, shape and size of the through channels, and the hydrophilicity differences of different crystal planes are utilized to separate the gas and liquid paths. At the same time, in applications, the present application can also utilize the pressure distribution in the fuel cell stack or the electrolysis device to drive the transport of fluids in the silicon-based transport layer.

[0022] Compared with the prior art, the silicon-based transport layer provided by the present invention mainly has the following advantages: The problems of large gas-liquid transmission resistance, poor electrical and thermal conductivity, and low mechanical strength existing in the titanium fiber diffusion layer and the carbon fiber porous transport layer are solved; due to the high chemical stability of the crystalline silicon material, it can work stably in the strongly acidic, high-potential, and highly oxidative environment of a PEM fuel cell or a PEM electrolysis device. Especially when used as the anodic porous transport layer of an electrolysis device, the technical problems and high costs brought by the need to plate a dense noble metal layer on a titanium felt in the prior art are eliminated; while saving costs, the silicon-based transport layer essentially avoids the problem of poor corrosion resistance of metal materials in the acidic atmosphere of the electrolysis device, greatly improving the service life of the electrolysis device; The main framework of the porous transport layer is made of doped conductive crystalline silicon material, which has excellent pressure resistance and can form an effective support for the membrane electrode, enabling the membrane electrode to withstand a greater differential pressure on both the anode and cathode sides. Especially in an electrolysis device, it is beneficial for high-pressure hydrogen production; and it has excellent electrical and thermal conductivity, superior to the internal electrical and thermal conductivity of titanium fiber felt and carbon fiber felt in the vertical plane; at the same time, silicon wafers (more preferably single-crystal silicon wafers) are preferably used as the silicon-based transport layer. Due to the excellent flatness of the silicon wafers, the thickness uniformity of each silicon wafer can be controlled within 5 microns, and the thickness consistency between different silicon wafers can also be controlled within a few microns, which is much better than the thickness uniformity and consistency of the existing titanium felt; moreover, the mass transfer performance of the silicon wafers is not affected by the pressure of the fuel cell stack or electrolysis device in which they are applied, avoiding problems such as the correlation between mass transfer ability and stack pressure in a carbon fiber gas diffusion layer; This application also preferably proposes to use a silicon-based material (preferably a silicon wafer) to make a perforated or lattice-type through-channel. The simple internal gas-liquid transmission path can significantly improve the mass transfer efficiency between the flow field and the catalyst in a fuel cell or an electrolysis device, and by flexibly controlling the shape, size, and surface morphology of the through-channel, gas and liquid diversion can be achieved, greatly reducing the mass transfer distance and resistance during the transmission process, thereby greatly improving the performance of the fuel cell stack or electrolysis device in which it is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the three-dimensional effect diagram of the lattice-type silicon-based transport layer fabricated in Example 1 of this application; Figure 2 is the physical photograph of the lattice-type silicon-based transport layer fabricated in Example 1 of this application; Figure 3 is the three-dimensional effect diagram of the lattice-type silicon-based transport layer fabricated in Example 2 of this application; Figure 4 is the physical photograph of the perforated-type silicon-based transport layer fabricated in Example 3 of this application; Figure 5 is the physical photograph of the perforated-type silicon-based transport layer fabricated in Example 4 of this application; Figure 6 It is a three-dimensional effect diagram of the perforated silicon-based transport layer fabricated in Example 5 of the present application; Figure 7 It is a schematic structural diagram of the perforated silicon-based transport layer fabricated in Example 6 of the present application; Figure 8 It is a polarization curve test diagram of the perforated silicon-based transport layer fabricated in Example 1 of the present application applied to an electrolysis device; Figure 9 It is a polarization curve test diagram of the perforated silicon-based transport layer fabricated in Example 2 of the present application applied to an electrolysis device; Figure 10 It is a three-dimensional simulation effect diagram of a silicon-based transport layer under the specific implementation manner of the present application; Figure 11 It is a scanning electron microscope photo of the physical object of the lattice-type silicon-based transport layer fabricated in Example 1 of the present application. Specific implementation manner

[0024] An embodiment of the present invention discloses a silicon-based transport layer, including at least one silicon-based material, and the silicon-based material is made of a doped conductive crystalline silicon material; wherein, the silicon-based material includes a first surface and a second surface, and a plurality of through channels for fluid transmission are provided between the first surface and the second surface; and the first surface or the second surface is used for stacked contact with a plate provided with a transverse transport flow field; the transverse direction involved throughout the present application is a direction perpendicular to the thickness direction of the silicon-based material, and the longitudinal direction involved throughout the present application is a direction parallel to the thickness direction of the silicon-based mass transfer material.

[0025] Preferably, in this embodiment, the silicon-based material is a silicon wafer, and more preferably, the silicon-based material is a single-crystal silicon wafer.

[0026] Preferably, in this embodiment, the bulk resistivity of the silicon wafer (the detection standard for the bulk resistivity involved throughout the present application is: GB / T 1551—2021) is not greater than 0.1 ohm centimeter, more preferably 1-30 milliohm centimeters, further preferably 1-10 milliohm centimeters, and even more preferably 1-5 milliohm centimeters. During actual implementation, the bulk resistance near the surface of the silicon wafer can be reduced by known processes such as impurity diffusion, so as to reduce the contact resistance between the silicon wafer and the adjacent structure; preferably, in this embodiment, the thickness range of the silicon wafer is 0.01-10 millimeters, more preferably 0.05-1 millimeter, further preferably 0.1-0.5 millimeter or more preferably 0.03-0.5 millimeter.

[0027] Preferably, in the present embodiment, the first surface is a smooth surface or a suede surface; the second surface is a smooth surface or a suede surface. It should be noted that the texturing method adopted in this embodiment can adopt any well-known texturing process, and this embodiment has no special limitation on it; in particular, it should be noted that since the first surface or the second surface will be stacked and contacted with the electrode plate during subsequent implementation and application, while the other surface is stacked and contacted with the catalyst, different surface state requirements are thus required. The suede surface involved in this application includes setting the first surface or the second surface into a partial suede surface state. Specifically, a suitable crystal silicon direction can be selected, and the characteristics of selective etching of crystal silicon in an alkaline etching solution can be utilized to obtain a undulating suede surface in some areas of the surface, while no suede surface will be obtained in the remaining areas of the surface; Specifically, for example: when applied in a fuel cell (specifically, a hydrogen fuel cell as an example), the surface in contact with the catalyst is preferably set to a suede surface with thick serrations or pyramids, so as to have lower hydrophilicity and higher gas affinity, so that the gas participating in the reaction can easily reach the catalyst surface to participate in the reaction, while the surface in contact with the electrode plate is preferably set to a suede surface with a fine and smooth shape, so as to have good hydrophilicity, and the water generated by power generation flows out from this surface through the through-channel and is discharged from the flow field of the electrode plate from the fuel cell stack; When applied in an electrolysis device (specifically, an electrolytic water device as an example), the surface in contact with the catalyst is set to a suede surface with a fine and smooth shape to enhance its surface hydrophilicity, so that water can fully wrap the catalyst to increase the hydrogen production rate; the surface in contact with the electrode plate is set to a smooth surface in one direction and a suede surface in another direction. Among them, the smooth surface has poor hydrophilicity and good gas affinity, while the suede surface has good hydrophilicity and poor gas affinity, so as to form water channels and air channels respectively (please refer to Figure 10 shown, its light-colored surface represents the smooth surface, and its dark-colored surface is the suede surface, and the suede surface has good hydrophilicity and gas hydrophobicity), and they do not interfere with each other and go their own ways, forming the most efficient longitudinal mass transfer effect.

[0028] In this embodiment, the shape of the silicon wafer can be circular, quadrilateral, hexagonal, or other suitable shapes, and there is no particular limitation when implementing this application; preferably, in this embodiment, the crystalline silicon material includes single-crystalline silicon and polycrystalline silicon, and the doping types include N-type and P-type; when the applied electrode plate is a metal material electrode plate, a graphite material electrode plate, or a composite material electrode plate, the silicon wafer of this embodiment preferably uses a crystalline silicon material with a lower contact resistance with the electrode plate; and when the applied electrode plate is also a crystalline silicon material, the silicon wafer of this embodiment preferably selects a crystalline silicon material with the same conductivity type as the electrode plate. Therefore, using an electrode plate made of crystalline silicon material as the preferred embodiment of this application, the preferred solutions for the electrode plate made of crystalline silicon material can refer to a series of prior patent applications: CN201810577217.7, CN201810577211.X, CN201810577210.5, CN2025200419413, and this embodiment will not be specifically elaborated; it should be particularly noted that the crystal orientations involved throughout this application include all crystal orientations, and single-crystalline silicon with <100>, <110>, and <111> crystal orientations is preferably used as the crystalline silicon material of this embodiment.

[0029] Preferably, as an embodiment, the through-channel includes a perforation; wherein, the perforation refers to a hole structure formed through the silicon wafer on the silicon wafer; preferably, in this embodiment, the hole structure is formed on the silicon wafer by physical and / or chemical methods, wherein the physical method includes a laser drilling method; the chemical etching method includes well-known porous silicon manufacturing methods, and forming a through-hole from one surface of the silicon wafer to the other surface by laser or photolithography opening on the silicon wafer with a mask and then selective etching. The hole structures formed by different processes are circular or non-circular (such as polygonal) on the first surface or the second surface; the hole structure is a straight through-hole or a non-straight through-hole (indicating that the shape and size of the hole structure change along the thickness direction of the silicon wafer, for example, it can be a curved hole); the porosity of the hole structure in the silicon wafer is 0.1 - 0.9, more preferably 0.3 - 0.8; the aperture of the hole structure on the first surface or the second surface is 10 - 1000 microns, more preferably 30 - 100 microns, more preferably 30 - 50 microns, wherein the distance between adjacent hole structures is equal to or close to the aperture; the aperture of the hole structure on the first surface is equal to or not equal to the aperture of the hole structure on the second surface.

[0030] In this embodiment, there is no limitation on the distribution pattern of the pore structure on the silicon wafer. It can be a square distribution, a plum blossom-shaped dense arrangement, or other shape distributions. Preferably, in this embodiment, the pore diameter of the pore structure on the first surface is smaller than the pore diameter of the pore structure on the second surface. The second surface is used for stacked contact with the plate provided with a transverse flow field, and the first surface is used for stacked contact with the catalyst. The pore diameter on the first surface is preferably 10-100 microns, and the pore diameter on the second surface is preferably 50-200 microns.

[0031] Preferably, as another embodiment, the through-channel includes window grilles. Among them, by respectively arranging the first channel and the second channel in a cross shape on the first surface and the second surface of the silicon wafer, and forming a perforated window grille at the intersection of the first channel and the second channel. The first channel is formed by physical and / or chemical methods; the second channel is formed by physical and / or chemical methods. Among them, the depth of the first channel is equal to or not equal to the depth of the second channel; the duty cycle of the first channel on the first surface is equal to or not equal to the duty cycle of the second channel on the second surface. As an implementation example, during specific manufacturing, it is selected to selectively remove the mask layer on the silicon wafer with a corrosion mask by laser or photolithography, and the silicon wafer is etched from both sides in an alkaline solution to form channels. The etching on both sides can start simultaneously, so that the depth of the first channel is equal to the depth of the second channel; it can also be selected to first laser etch or photolithographically etch one side and etch for a period of time, then perform laser etching or photolithography on the other side, and then etch in an alkaline solution, so that the depth of the first channel is not equal to the depth of the second channel. Further, the first channel is composed of a connected first groove and a first ridge, and the second channel is composed of a connected second groove and a second ridge. The channel depth involved throughout the text of this application is the height of the ridge.

[0032] Preferably, in this embodiment, the depth of the first channel is smaller than the depth of the second channel, and the duty cycle of the first channel on the first surface is smaller than the duty cycle of the second channel on the second surface. The first surface is used for stacked contact with the catalyst. Further preferably, the width of the first ridge is set to 20-500 microns, more preferably 50-100 microns. And the second surface is used for stacked contact with the plate provided with a transverse flow field. The reactants in the plate contact the catalyst through the window grilles of the silicon-based diffusion layer to participate in the reaction, and the substances generated by the reaction enter the plate flow field through the silicon-based diffusion layer and are discharged from the fuel cell (stack) or electrolysis device. Preferably, the width of the second groove is 0.01-5 mm, preferably 0.05-0.1 mm; the width of the second ridge is 0.01-5 mm, preferably 0.02-0.4 mm; the height of the second ridge is 0.01-5 mm, preferably 0.02-0.5 mm.

[0033] It should be further noted that since the through-channel formed by the window lattice has a channel structure (located on the first surface or the second surface of the silicon wafer), preferably, in this embodiment, while serving as a gas diffusion layer, it can also directly serve as a transverse transport flow field to achieve the function of the electrode plate; during actual operation, the reactants entering the fuel cell (stack) or the electrolysis device are laterally transported to various parts of the reaction zone, and then longitudinally pass through the silicon-based transport layer to reach the catalyst surface to participate in the reaction. The products generated by the reaction then longitudinally pass through the silicon-based transport layer to the flow field side and laterally flow out of the fuel cell (stack) or the electrolysis device; when the hydraulic diameter of the flow channel of the electrode plate is sufficient, the channel of the silicon-based transport layer can be regarded as the flow channel surface and can directly form a bipolar plate with the electrode plate stacked in contact with it.

[0034] Preferably, this embodiment also proposes an application of the silicon-based transport layer, using the above application of the silicon-based transport layer as the porous transport layer of the fuel cell or the electrolysis device; wherein, the first surface or the second surface of the silicon wafer is used to be stacked in contact with the electrode plate provided with the transverse transport flow field.

[0035] Preferably, in this embodiment, the fuel cell includes a plurality of stacked fuel cell units, wherein a single fuel cell unit includes an electrode plate provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the electrode plate is an anode plate or a cathode plate or a bipolar plate; the silicon-based transport layer is located between the electrode plate and the catalyst, with the first surface or the second surface stacked in contact with the electrode plate and the other surface stacked in contact with the catalyst.

[0036] Preferably, in this embodiment, the electrolysis device includes a plurality of stacked electrolysis units, wherein a single electrolysis unit includes an electrode plate provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the electrode plate is an anode plate or a cathode plate or a bipolar plate; the silicon-based transport layer is located between the electrode plate and the catalyst, with the first surface or the second surface stacked in contact with the electrode plate and the other surface stacked in contact with the catalyst.

[0037] It should be noted that the electrode plates involved throughout this application can adopt any well-known electrode plates, preferably silicon-based electrode plates; the catalysts and membrane structures involved throughout this application can adopt any well-known catalysts and membrane structures. Among them, the membrane structure usually adopts a proton exchange membrane, and the catalyst is usually a coating structure provided on the membrane structure.

[0038] Since the silicon-based transport layer can use single-crystalline silicon wafers with different crystal orientations as raw materials, perforated or lattice-type through-channels can be formed in different directions by different methods, and its surface can be treated by different methods, so as to freely design the structure of the silicon-based transport layer in multiple dimensions and achieve the best mass transport effect. Whether in a fuel cell stack (hydrogen and oxygen are the reactants at the anode and cathode respectively, and water is the product and mainly concentrated at the cathode), or in an electrolysis device (water flows in from the anode as a reactant, and hydrogen and oxygen are generated as products at the cathode and anode respectively), a hydrophilic and gas-philic surface can be formed on the perforated or lattice-type through-channels, so that water and gas can automatically follow the traffic rules, each going its own way and not interfering with each other, to achieve the most efficient internal gas-liquid transport purpose; Therefore, preferably, the silicon-based transport layers in each fuel cell unit or each electrolysis unit are the same or different in material or structure.

[0039] It should be noted that in practical applications of this embodiment, the silicon-based transport layer can have a border or not; among them, the silicon-based transport layer with a border only makes a porous transport layer structure in the active area, and the border area is used for sealing, and can be stacked with the sealing areas of other components of the fuel cell (stack) or electrolysis device to form a fuel cell (stack) or electrolysis device. These are all conventional choices that those skilled in the art can make in combination with common knowledge. The silicon-based transport layer without a border can be made on the whole silicon wafer or made under the condition of having a border, and then the silicon-based transport layer is cut off with tools such as lasers. It can form an MEA membrane electrode with CCM (catalyst coated membrane) like a conventional gas diffusion layer, or directly form a plate diffusion layer composite with the plate. This application does not make special restrictions on its assembly method during implementation.

[0040] The perforated or lattice-type through-channels involved in this embodiment can be formed by physical and / or chemical methods. Those skilled in the art can make specific selections according to actual needs and in combination with common knowledge. The following are several optional manufacturing methods listed in this embodiment: A. Chemical method: etching

[0041] Using laser or lithography methods, selectively etch off the mask on the silicon wafer wrapped with the mask to expose the silicon material point by point, and use alkali etching and electrochemical etching to obtain independent holes passing through the silicon wafer, which are perforations; or use laser to etch lines on both sides of the silicon wafer on the silicon wafer wrapped with the mask, and the lines on both sides of the silicon wafer form a certain angle. Use alkali etching or electrochemical etching methods to etch channels from both sides until the bottoms of the channels on both sides penetrate each other to form a lattice.

[0042] B. Physical method combined with chemical method: laser drilling + selective etching (that is, etching can be carried out or not). Use a laser to punch through holes in the silicon wafer, and then use an alkali to corrode and clean the silicon slag in the holes and on the edges of the holes to obtain through-holes; or use the method of directly laser drilling, in which case it is not necessary to form a mask layer on the silicon wafer. However, laser drilling consumes a large amount of energy, and the silicon wafer is prone to cracking under thermal stress after absorbing laser energy. When using the method of laser opening, the thickness range of the selected silicon wafer is preferably 0.1 - 1 mm, more preferably 0.03 - 0.5 mm, and even more preferably 0.15 - 0.3 mm.

[0043] C. Chemical method: Wet preparation with noble metal catalysis Coat noble metal particles on the surface of the silicon wafer. In a solution of hydrofluoric acid and an oxidant, the noble metal particles catalyze the reaction between silicon and the solution to form holes with a certain direction and shape. Commonly used oxidants include HNO3 and H2O2. Noble metals include, but are not limited to, gold and silver. The noble metal can participate in the reaction in the form of ions in the solution, or can be deposited on the silicon surface in a certain way. The deposition methods include liquid phase deposition, vapor deposition, and evaporation, and the deposition amount is not limited.

[0044] It should also be noted that when implementing this application, the silicon-based material can also be sintered and formed from granular crystalline silicon. However, the applicant recommends using a silicon wafer as the silicon-based material as a more preferred solution for this application. The polarization curve performance of preparing a silicon-based transport layer by sintering and forming granular crystalline silicon is worse than that of preparing a silicon-based transport layer using a silicon wafer as the silicon-based material; The specific method of sintering and forming granular crystalline silicon can be referred to as follows:

[0045] Sintering method: Sintering and forming silicon particles (i.e., granular crystalline silicon) The granular crystalline silicon is placed in a mold of a certain shape or mixed with a pore-forming agent, and sintered at a high temperature under the protection of an inert gas or vacuum to form a silicon-based transport layer with pores of a certain shape and size; among them, the particle size of the silicon particles is 0.1 - 100 μm, preferably 5 - 20 μm.

[0046] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0047] Example 1: Please refer to Figure 1 、 Figure 2 and in combination with Figure 11 as shown, use a <110> silicon wafer to fabricate a lattice-type silicon-based transport layer. The specific operation process is as follows: After oxidation of the <110> silicon wafer, the oxide layer is etched away by laser along the <1-12> direction on one side and along the <-112> direction on the other side, and then channels are etched in an alkaline etching solution; when the channels etched on both sides penetrate each other, the etching is stopped, and the oxide layer on the surface is removed to obtain a silicon-based transport layer.

[0048] In practical applications, the widths and periods of laser etching on both sides of the silicon wafer can be different, and the side with narrower grooves and ridges of the channel contacts the catalyst (the first surface, also called the "catalyst surface"), and the other side contacts the flow field of the bipolar plate (the second surface, also called the "bipolar plate surface"); when the laser etching depths on the catalyst surface and the bipolar plate surface are the same, the depths of the channels on both sides are the same after alkaline etching.

[0049] One of the following two methods is used to fabricate the bipolar plate surface, where the channels are wider and deeper, while the channels on the catalyst surface are narrower and shallower, to facilitate sufficient mass transfer on the bipolar plate surface and more uniform reaction of the catalyst: a. Laser etching is used to create wider and deeper flow channels on the bipolar plate surface and narrower and shallower flow channels on the catalyst surface. After alkaline etching, the resulting silicon-based diffusion layer has wider and deeper flow channels on the bipolar plate surface and shallower and narrower flow channels on the catalyst surface.

[0050] b. Channels are first etched on the bipolar plate surface. After a period of alkaline etching, flow channels are then etched on the catalyst surface, and then alkaline etching is continued to obtain the same effect as in method a.

[0051] Each wall of the silicon-based transport layer obtained by the above method is a crystal plane of the <111> crystal orientation family, and it is impossible to fabricate a textured surface on it. However, the size selection of the flow channels on the catalyst surface and the bipolar plate surface is also conducive to the transport of gas and water, and no phenomena affecting mass transfer such as bubbles are found in the application in the electrolysis device.

[0052] Furthermore, during the implementation of this embodiment, the surface of the <110> silicon wafer is first etched to obtain a serrated textured surface, and the serrated textured surface is a crystal plane in the <111> and <11-1> directions; voids are formed during the contact between this textured surface and the catalyst. Since the catalyst is more hydrophilic relative to the silicon-based surface, water in the electrolysis device can be quickly and evenly distributed on the surface of the catalyst, and the oxygen or hydrogen generated by the reaction flows from the silicon wafer surface into the channels and is discharged. Therefore, the mass transfer performance of this type of silicon-based transport layer is excellent.

[0053] Example 2: Please refer to Figure 3 As shown, a lattice-type silicon-based transport layer is fabricated using a <100> silicon wafer, and the specific operation process is as follows: On the polar plate surface (i.e., the second surface) of the silicon wafer, use a laser to etch channels along the <010> crystal orientation on the surface with silicon oxide. Then, etch channels along the <001> crystal orientation on the first surface (i.e., the catalyst surface) of the silicon wafer. Next, perform alkaline etching to obtain channels perpendicular to each other on both sides. When the channels penetrate each other, a lattice-like silicon-based diffusion layer similar to that in Example 1 is formed. Different from Example 1, in this example, during alkaline etching, while the channels are etched in the <100> direction in the depth direction, they are also etched in the <001> and <010> directions, forming channels with a width approximately twice the depth. Since the channels are relatively wide, on the catalyst surface, the resistance of the silicon-based transport layer to transporting charges to the catalyst near the center of the channel is relatively large.

[0054] To reduce the channel width on the catalyst surface, first perform laser grooving and alkaline etching on the polar plate surface. Then, perform laser etching and alkaline etching on the catalyst surface. Similarly, when the flow channels on both sides penetrate each other, a lattice-like through-channel is formed. Since the etching time on the catalyst surface is short, the channel width caused by lateral etching is relatively small, and the charge transfer resistance between the channels of the silicon-based transport layer and the catalyst is relatively small, resulting in a higher energy conversion efficiency of the fuel cell stack or electrolysis device applied.

[0055] To further reduce the width of the channels and ridges on the catalyst surface and improve the process control ability of the silicon-based transport layer, a more preferred design is as follows: Use a laser to etch along the <010> crystal orientation on the polar plate surface, but etch along the <011> direction on the catalyst surface, and then perform alkaline etching of the channels. On the polar plate surface, while the channels are etched in the depth direction, they are also laterally etched to form rectangular channels, and the etching on the catalyst surface forms V-shaped channels with side walls of <111> and <-111> planes. The corrosion rate of this surface in the alkaline solution is very slow, so the width of the V-shaped groove is determined by the laser etching or photolithography etching width. During further corrosion, the depth and width of the V-shaped groove on the catalyst surface change very little. When the channels on the polar plate surface and the V-shaped grooves on the catalyst surface penetrate each other, a lattice-like porous transport layer is also formed. For this type of lattice-like porous transport layer, the channel width on the catalyst surface is small, and the hydraulic diameter of the channels on the polar plate surface is large, which is more conducive to the transport of reactants and products and also conducive to the charge transfer between the grid bars of the silicon-based diffusion layer and the catalyst. The performance of the fuel cell stack and electrolytic cell is good and the conversion efficiency is high.

[0056] Example 3: Please refer to Figure 4 As shown, fabricate a perforated silicon-based transport layer on a <111> silicon wafer: The specific operation process is as follows: On a silicon wafer with a crystal orientation of <111>, it is drilled through with a laser, and then the laser residues in the laser holes are etched away in an alkaline etching solution to form a perforated silicon-based transport layer. Among them, the pore structure is a triangular hole, distributed in the AA type of holes; due to its surface being the <111> crystal plane, the etching rate in the alkaline etching solution is very slow, so the thinning amount of the silicon wafer is small during the etching process, but the etching rate is relatively fast around the laser-etched holes, and a slope is formed after alkaline etching. When applied in an electrolytic cell (i.e., an electrolysis device), a wedge-shaped gap is formed between the silicon-based transport layer on the anode side and the catalyst, where water can enter and participate in the electrolysis of water reaction; the water generated by the reaction can be quickly squeezed out of the wedge-shaped gap and flow away through the perforations in the flow channels of the electrode plate.

[0057] Example 4: The rest of the technical solutions of this Example 4 are the same as those of Example 3, the difference is, please refer to Figure 5 as shown, the pore structure is circular holes with different aperture specifications.

[0058] Example 5: The rest of the technical solutions of this Example 5 are the same as those of Example 3, the difference is, please refer to Figure 6 as shown, a silicon wafer with a crystal orientation of <100> is used to make the perforated silicon-based transport layer; the pore structure is circular holes with the same aperture specification.

[0059] Example 6: The rest of the technical solutions of this Example 6 are the same as those of Example 5, the difference is, please refer to Figure 7 as shown, the pore structure is hexagonal holes, distributed in the AB type of holes.

[0060] To further prove the implementation effect of the embodiments of the present application, the applicant used the lattice-type silicon-based transport layer obtained in Example 1, the porosity of the pore structure in the silicon wafer is 0.5; the aperture of the pore structure on the first surface and the second surface is 145 microns, replacing the conventional anode titanium felt used in the electrolysis device, and assembling and applying it to the electrolysis device, and conducting a polarization curve test on it. Each current density runs for 30 s, and the stable value of the last 10 s is taken. The test results are shown in Figure 8 as shown, where the test temperature is 65 °C, the active area is 25 cm 2 , the circulating water flow rate is 2 ml / (cm 2 min); the electrolyte is a proton exchange membrane, the catalyst anode is iridium, and the cathode is platinum carbon; the polarization performance is: 1.947 V@1 A / cm 2 .

[0061] To further prove the implementation effect of the embodiments of the present application, the applicant adopted the window lattice type silicon-based transport layer obtained in Embodiment 2, wherein the porosity of the pore structure in the silicon wafer is 0.7; the pore diameter on the first surface of the pore structure is 110 microns, and the pore diameter on the second surface is 380 microns. It replaced the anodic titanium felt conventionally used in the electrolysis device, assembled and applied it to the electrolysis device, and carried out polarization curve tests. The test results can be seen in Figure 9 as shown; wherein, the test temperature is 65 °C, and the active area is 25 cm 2 , and the circulating water flow rate is 2 ml / (cm 2 min); the electrolyte is a proton exchange membrane, the catalyst anode is iridium, and the cathode is platinum-carbon; the polarization performance is: 1.83 V@2 A / cm 2 .

[0062] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0063] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A silicon-based transport layer, characterized in that, It includes at least one silicon-based material, which is made of doped conductive crystalline silicon material; wherein, the silicon-based material includes a first surface and a second surface, and a number of through-channels for fluid transmission are provided between the first surface and the second surface; and the first surface or the second surface is used for stacked contact with a plate provided with a transverse transmission flow field; the silicon-based material is preferably a silicon wafer.

2. The silicon-based transmission layer according to claim 1, characterized in that, The silicon-based material is a silicon wafer, and the through-channel includes a perforation; wherein, the perforation refers to a hole structure formed through the silicon wafer on the silicon wafer.

3. The silicon-based transmission layer according to claim 2, wherein The hole structure is formed on the silicon wafer by physical and / or chemical methods; the hole structure is circular or non-circular on the first surface or the second surface; the hole structure is a straight through-hole or a non-straight through-hole; the porosity of the hole structure in the silicon wafer is 0.1-0.9; the aperture of the hole structure on the first surface or the second surface is 10-1000 microns; the aperture of the hole structure on the first surface is equal to or not equal to the aperture of the hole structure on the second surface.

4. The silicon-based transmission layer according to claim 3, wherein, The aperture of the hole structure on the first surface is smaller than the aperture of the hole structure on the second surface, and the second surface is used for stacked contact with a plate provided with a transverse transmission flow field.

5. The silicon-based transfer layer according to claim 1 or 2, characterized in that, The through-channel includes a lattice; wherein, by respectively arranging a cross-shaped first channel and a second channel on the first surface and the second surface of the silicon-based material, and a through-shaped lattice is formed at the intersection of the first channel and the second channel; the first channel is formed by physical and / or chemical methods; the second channel is formed by physical and / or chemical methods; wherein, the depth of the first channel is equal to or not equal to the depth of the second channel; the duty cycle of the first channel on the first surface is equal to or not equal to the duty cycle of the second channel on the second surface.

6. The silicon-based transmission layer according to claim 5, wherein The depth of the first channel is smaller than the depth of the second channel, and the duty cycle of the first channel on the first surface is smaller than the duty cycle of the second channel on the second surface, and the second surface is used for stacked contact with a plate provided with a transverse transmission flow field.

7. The silicon-based transmission layer according to claim 5, wherein The channel provided on the first surface or the second surface in stacked contact with the plate simultaneously serves as a transverse transmission flow field to realize the function of the plate.

8. The silicon-based transmission layer according to claim 1, wherein The bulk resistivity of the silicon-based material is not greater than 0.1 ohm-cm; the thickness range of the silicon-based material is 0.01-10 mm, more preferably 0.03-0.5 mm; the first surface is a smooth surface or a textured surface; the second surface is a smooth surface or a textured surface.

9. The silicon-based transmission layer according to claim 1, characterized in that, The silicon-based material is formed by sintering granular crystalline silicon.

10. Application of a silicon-based transport layer, characterized in that, The silicon-based transmission layer according to any one of claims 1-9 is applied as a porous transmission layer of a fuel cell or an electrolysis device; wherein, the first surface or the second surface of the silicon-based material is used for stacked contact with a plate provided with a transverse transmission flow field.

11. The application of the silicon-based transmission layer according to claim 10, characterized in that, The fuel cell includes a number of stacked fuel cell units. Among them, a single fuel cell unit includes a plate electrode provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the plate electrode is an anode plate, a cathode plate, or a bipolar plate; the silicon-based transport layer is located between the plate electrode and the catalyst, and either the first surface or the second surface is in stacked contact with the plate electrode, and the other surface is in stacked contact with the catalyst. The electrolysis device includes a number of stacked electrolysis units. Among them, a single electrolysis unit includes a plate electrode provided with a transverse transport flow field, a silicon-based transport layer, a catalyst, and a membrane structure; the plate electrode is an anode plate, a cathode plate, or a bipolar plate; the silicon-based transport layer is located between the plate electrode and the catalyst, and either the first surface or the second surface is in stacked contact with the plate electrode, and the other surface is in stacked contact with the catalyst.

12. The application of the silicon-based transmission layer according to claim 11, wherein, The silicon-based transport layers in each fuel cell unit or each electrolysis unit are the same or different in terms of material or structure.

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