Improved structure of bipolar plate for electrocatalytic carbon dioxide to form formic acid

Abstract

This invention discloses an improved bipolar plate structure for the electrocatalytic production of formic acid from carbon dioxide, belonging to the field of electrocatalytic carbon dioxide reduction technology. It includes a substrate layer, a bottom protective layer, a gradient functional composite layer, a surface functional layer, and a catalyst layer. The gradient functional composite layer consists of a conductive enhanced microporous layer, a gas-liquid separation transition layer, and a porous elastic support layer. The surface functional layer consists of an amorphous carbon-based barrier layer and a MOF functional layer. The surface of the catalyst layer is provided with a fractal dendritic flow field, which consists of multiple sets of main channels, secondary channels, and tertiary channels. This improved bipolar plate structure for the electrocatalytic production of formic acid from carbon dioxide overcomes the limitations of traditional bipolar plates in terms of single performance optimization, achieving a systematic improvement in the efficiency and stability of the electrocatalytic reaction. It is suitable for industrial electrolysis devices that efficiently convert carbon dioxide into formic acid.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic carbon dioxide reduction technology, specifically relating to an improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production. Background Technology

[0002] Electrocatalytic reduction of carbon dioxide to formic acid, as a green technology that combines carbon fixation and the synthesis of high-value-added chemicals, has become a research hotspot in the field of energy conversion. As a core component of the electrolyzer, the bipolar plate undertakes multiple functions, including reactant transport, electron conduction, mechanical support, and gas-liquid separation. Its structural design and material properties directly determine the efficiency and stability of the CO2 electrocatalytic reaction.

[0003] Currently, the flow fields of bipolar plates used in industrial applications are mainly parallel flow fields and serpentine flow fields. Their linear or broken channel design leads to high flow velocities at the inlet, resulting in concentrated pressure drop. At the outlet, a local "gas-deficient zone" appears due to reaction consumption. The standard deviation of CO2 concentration on the catalyst layer surface is large, resulting in insufficient utilization of active sites. Utility Model Content

[0004] The purpose of this invention is to provide an improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production, in order to solve the problems mentioned in the background art, such as high flow rate at the inlet leading to concentrated pressure drop, local "gas-deficient zone" at the outlet due to reaction consumption, large standard deviation of CO2 concentration on the catalyst layer surface, and insufficient utilization of active sites.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production, comprising a substrate layer, a bottom protective layer, a gradient functional composite layer, a surface functional layer, and a catalyst layer. The gradient functional composite layer is composed of a conductive enhanced microporous layer, a gas-liquid separation transition layer, and a porous elastic support layer. The surface functional layer is composed of an amorphous carbon-based barrier layer and a MOF functional layer. The surface of the catalyst layer is provided with a fractal dendritic flow field, which is composed of multiple sets of main channels, secondary channels, and tertiary channels.

[0006] In a further embodiment, nickel-titanium shape memory alloy microbeams are embedded in the ridge of the fractal tree-like flow field, which can dynamically adjust the width of the flow channel according to the gas pressure.

[0007] In a further embodiment, the gas-liquid separation transition layer comprises an alternating array of superhydrophobic and hydrophilic fibers for actively separating the water generated by the reaction and guiding gas permeation.

[0008] In a further embodiment, the porous elastic support layer is made of a 3D-printed graphene polymer composite framework, with porosity decreasing exponentially along the thickness direction.

[0009] In a further embodiment, the surface of the MOF functional layer has unsaturated metal coordination centers, which serve as catalyst anchoring sites and CO2 adsorption activation sites.

[0010] In a further embodiment, the conductive enhanced microporous layer is a composite film of a carbon-based conductive network and a metal oxide.

[0011] The technical effects and advantages of this utility model are as follows:

[0012] The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production features a fractal dendritic flow field structure that significantly enhances the uniformity of CO2 gas distribution on the catalyst layer surface, effectively eliminating the "gas-deficient zone" and concentration gradient differences in traditional flow fields, and greatly improving the utilization rate of active sites.

[0013] The flow channel width is dynamically adjusted by using shape memory alloy microbeams. At low loads, the flow channel contracts to increase gas concentration, and at high loads, the flow channel expands to reduce pressure drop, ensuring stable mass transfer efficiency across the entire current density range and significantly reducing system energy consumption.

[0014] The superhydrophobic and hydrophilic fiber array enables real-time active separation of water generated in the reaction, effectively stabilizing the water content of the catalyst layer within the optimal reaction range, significantly reducing the risk of catalyst deactivation caused by flooding and drying. At the same time, the gradient porosity design of the porous elastic support layer forms a gas diffusion buffer zone, rapidly dispersing high-speed gas flow at the inlet end and homogenizing gas pressure at the outlet end, avoiding liquid film instability caused by sudden changes in flow rate.

[0015] The three-dimensional carbon nanotube network of the conductive enhanced microporous layer provides efficient electron channels and strong binding sites for the catalyst, significantly improving the catalyst adhesion stability. This improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production breaks through the limitations of single performance optimization of traditional bipolar plates, achieving a systematic improvement in electrocatalytic reaction efficiency and stability. It is suitable for industrial electrolysis devices that efficiently convert carbon dioxide into formic acid. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of this utility model;

[0018] Figure 2 This is a cross-sectional view of the gradient functional composite layer of this utility model;

[0019] Figure 3 This is a cross-sectional view of the surface functional layer of this utility model;

[0020] Figure 4 For the present utility model Figure 1 Enlarged view of point A in the middle.

[0021] In the figure: 1. Substrate layer; 2. Bottom protective layer; 3. Gradient functional composite layer; 4. Surface functional layer; 5. Catalyst layer; 6. Conductivity-enhanced microporous layer; 7. Gas-liquid separation transition layer; 8. Porous elastic support layer; 9. Amorphous carbon-based barrier layer; 10. MOF functional layer; 11. Main channel; 12. Secondary channel; 13. Tertiary channel; 14. Nickel-titanium shape memory alloy microbeam. Detailed Implementation

[0022] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid confusion with the present invention.

[0023] Unless otherwise defined, the directions mentioned herein, such as up, down, left, right, front, back, inside, and outside, are based on the directions shown in the figures of this utility model, and are explained here together.

[0024] This utility model provides, for example Figure 1-4 The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production shown includes a substrate layer 1, a bottom protective layer 2, a gradient functional composite layer 3, a surface functional layer 4, and a catalyst layer 5. The substrate layer 1 can be made of lightweight aluminum alloy plate with a thickness of 1-2 mm, providing mechanical support and an electronic conduction substrate. Its surface is pretreated to form a rough surface, which enhances the adhesion of subsequent coatings and forms a gradient functional structure. The bottom protective layer 2 is in direct contact with the substrate layer 1. Through candle ash pyrolysis technology, an 8-10 μm thick composite carbon film containing nanocrystalline diamond cores is formed on its surface. At the same time, diamond nanocrystals with a diameter of 5-20 nm are embedded in the disordered carbon matrix to form a "hard-soft" composite structure, while retaining 1-5 μm micron-level pores (porosity 15%-20%) to allow electrons to penetrate and block electrolyte ion penetration.

[0025] The gradient functional composite layer 3 consists of a conductive reinforced microporous layer 6, a gas-liquid separation transition layer 7, and a porous elastic support layer 8. The conductive reinforced microporous layer 6 is a composite film of a carbon-based conductive network and a metal oxide. The surface of the conductive reinforced microporous layer 6 is hydrophilic (contact angle <30°) to promote the adhesion of the catalyst precursor. The gas-liquid separation transition layer 7 contains an alternating array of superhydrophobic and hydrophilic fibers for actively separating the water generated in the reaction and guiding gas permeation. The superhydrophobic fibers are polyvinylidene fluoride nanofibers (diameter 5-10 μm, contact angle >140°) with fluorosilane grafted on the surface. Water-based fibers: Polyvinyl alcohol nanofibers (diameter 1-3μm, contact angle <20°), surface hydroxylated, the reaction generates water that forms a liquid bridge on the surface of the superhydrophobic fiber and is discharged along the fiber axis. The pores of the hydrophilic fiber allow CO2 molecules to diffuse to the catalyst layer, effectively improving the permeability. The porous elastic support layer 8 uses a 3D-printed graphene polymer composite skeleton with porosity decreasing exponentially along the thickness direction. The outer side (airflow inlet side) has high porosity, while the inner side (catalyst layer side) has low porosity. The large pores on the outer side quickly disperse the CO2 gas flow, while the small pores on the inner side homogenize the gas pressure.

[0026] The surface functional layer 4 consists of an amorphous carbon-based barrier layer 9 and a MOF functional layer 10. The surface of the catalyst layer 5 is provided with a fractal tree-like flow field, which consists of multiple main channels 11, secondary channels 12 and tertiary channels 13. The ridges of the flow channels of the fractal tree-like flow field are embedded with nickel-titanium shape memory alloy microbeams 14, which can dynamically adjust the width of the flow channel according to the gas pressure. The surface of the flow channel is etched with 50μm deep microgrooves and 200nm diameter hydrophilic bumps to form a surface energy gradient (hydrophobic at the edges and hydrophilic at the center), which guides the gas to gather towards the center of the catalyst layer. The surface of the MOF functional layer 10 has unsaturated metal coordination centers, which serve as catalyst anchoring points and CO2 adsorption activation sites. The catalyst layer 5 is directly grown on the surface of the MOF functional layer 10 by electrodeposition.

[0027] All standard parts used in this utility model can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here. The control method of this utility model is through a controller. The control circuit of the controller can be implemented by those skilled in the art through simple programming. The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0028] In the description of this utility model, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0029] Working principle:

[0030] The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production features a multi-level branching structure that first evenly disperses the gas onto the surface of the catalyst layer 5 when CO2 gas enters the fractal tree-like flow field on the surface of the bipolar plate from the inlet of the electrolyzer. The nickel-titanium shape memory alloy microbeams 14 at the ridge of the flow channel dynamically adjust the width of the flow channel according to the gas pressure. Under low load, the flow channel contracts to increase the local gas concentration, while under high load, the flow channel expands to reduce the pressure drop. Combined with the micro-nano composite grooves on the surface of the flow channel, the gas is guided to diffuse in a directional manner through the surface energy gradient, effectively avoiding the problems of uneven distribution and flow resistance in traditional flow fields.

[0031] After the gas is uniformly distributed through the flow field, it passes through the outer porous elastic support layer 8, whose gradient pore structure forms a gas diffusion buffer zone, achieving uniform pressure of the gas flow, and enters the middle gas-liquid separation transition layer 7. The superhydrophobic and hydrophilic fiber array in this layer actively separates the liquid water and gas generated by the reaction using capillary effect. The superhydrophobic fibers repel liquid water and guide it out, while the hydrophilic fibers allow CO2 molecules to permeate to the inner conductive enhanced microporous layer 6. The latter, through the three-dimensional conductive network of the carbon-based conductive network and the composite film of metal oxide, efficiently conducts electrons from the electrode substrate layer 1 to the catalytic reaction interface, while providing strong anchoring points for the catalyst.

[0032] At the catalytic reaction interface, the dual-layer integrated coating plays a crucial role: the bottom amorphous carbon-based barrier layer 9 blocks the electrolyte from eroding the metal substrate layer 1 while retaining micron-sized pores to maintain electron transport; the surface MOF functional layer 10 pre-adsorbs CO2 molecules through its porous structure and lowers their activation energy; and the unsaturated metal coordination centers on the surface fix the bismuth oxychloride catalyst through chemical bonds, forming an integrated interface of "electron conduction-gas adsorption-catalytic reaction." The adsorbed and activated CO2 molecules gain electrons at the catalyst's active sites and react with H+ in the electrolyte. + The product is collected by combining to form formate ions (HCOO-), which eventually flow out with the electrolyte.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. Bipolar plate improved structure for electrocatalytic carbon dioxide to formic acid, comprising a substrate layer (1), a bottom protective layer (2), a gradient functional composite layer (3), a surface functional layer (4) and a catalyst layer (5), characterized in that: The gradient functional composite layer (3) is composed of a conductive enhanced microporous layer (6), a gas-liquid separation transition layer (7) and a porous elastic support layer (8). The surface functional layer (4) is composed of an amorphous carbon-based barrier layer (9) and a MOF functional layer (10). The surface of the catalyst layer (5) is provided with a fractal tree flow field, which is composed of multiple sets of main channels (11), secondary channels (12) and tertiary channels (13).

2. The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production according to claim 1, characterized in that: The flow channel ridge of the fractal tree-like flow field is embedded with nickel-titanium shape memory alloy microbeams (14), which can dynamically adjust the flow channel width according to the gas pressure.

3. The improved bipolar plate structure for electrocatalytic production of formic acid from carbon dioxide according to claim 1, characterized in that: The gas-liquid separation transition layer (7) comprises an alternating array of superhydrophobic and hydrophilic fibers for actively separating water generated by the reaction and guiding gas permeation.

4. The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production according to claim 1, characterized in that: The porous elastic support layer (8) is made of 3D-printed graphene polymer composite skeleton, and the porosity decreases exponentially along the thickness direction.

5. The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production according to claim 1, characterized in that: The surface of the MOF functional layer (10) has unsaturated metal coordination centers, which serve as catalyst anchoring sites and CO2 adsorption activation sites.

6. The improved bipolar plate structure for electrocatalytic carbon dioxide to formic acid production according to claim 1, characterized in that: The conductive enhanced microporous layer (6) is a composite film of carbon-based conductive network and metal oxide.

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