A direct liquid fuel cell with an anode flow field

Abstract

The application discloses a direct liquid fuel cell of an anode flow field, which comprises an anode current collector plate, a cathode current collector plate, a membrane electrode assembly and an anode flow field plate. The membrane electrode assembly is clamped between the anode current collector plate and the cathode current collector plate, and the anode flow field plate is arranged between the anode current collector plate and the membrane electrode assembly. The anode flow field plate is made of a hydrophobic porous layer to capture and discharge bubbles generated by the anode in situ; the anode flow field plate is internally provided with an interdigital flow field to enable liquid fuel to enter the membrane electrode assembly in a forced convection mode and to carry and discharge dissolved oxygen in the membrane electrode assembly outward. The direct liquid fuel cell of the anode flow field can promote efficient discharge of bubbles, avoid anode oxygen permeation problems, and has no additional equipment and extra energy loss, so that the problems of mass transfer deterioration caused by bubbles, low conversion efficiency and difficult compatibility of output stability can be effectively solved, and the direct liquid fuel cell has important significance for promoting the commercialization process of high-performance direct liquid fuel cells.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a direct liquid fuel cell with an anode flow field. Background Technology

[0002] Direct liquid fuel cells (DLFCs) can directly convert the chemical energy of carbon-based liquid fuels such as methanol and formic acid, as well as nitrogen-based liquid fuels such as liquid ammonia and hydrazine, into clean electrical energy. They have advantages such as high energy density, environmental friendliness, and mild operating conditions. At the same time, they effectively solve the hydrogen storage and transportation problems faced by hydrogen fuel cells. They are one of the clean energy efficient utilization technologies that help achieve my country's "dual carbon" goals.

[0003] In actual operation, DLFCs inevitably face high-current operating conditions. Taking liquid ammonia / methanol fuel as an example, a large number of N2 / CO2 bubbles are generated at the battery anode. On the one hand, bubbles adhering to the electrode surface occupy the electrochemical active area, hindering reactant transport and leading to ohmic losses and increased anode overpotential; at the same time, they cause uneven fuel distribution, resulting in anode concentration polarization losses. On the other hand, the growth and detachment of bubbles cause fluctuations in battery performance, reduced voltage stability, and the drag force generated by voltage fluctuations and bubble detachment accelerates anode catalyst aging and shedding. In addition, bubbles accumulating in the anode channel significantly increase the pressure drop and fuel permeation risk within the channel, which severely restricts the commercialization of DLFCs.

[0004] Currently, common methods to promote bubble removal in DLFCs under high current density, such as altering operating conditions (e.g., increasing fuel flow rate or solution temperature) and applying external force fields (e.g., acoustic, magnetic, or electric fields), address issues like mass transfer degradation, low conversion efficiency, and poor output stability caused by bubbles within the cells. However, these active methods have the following drawbacks: 1) Increasing fuel flow rate reduces fuel utilization, while increasing solution temperature may lead to decreased membrane stability and fuel permeation problems; 2) Applying external acoustic / magnetic / electric fields increases overall system power consumption and complexity, reducing the battery's net output power. Summary of the Invention

[0005] Therefore, it is necessary to provide a direct liquid fuel cell with an anode flow field to address the above problems, thereby solving the issues of mass transfer degradation caused by bubbles, low conversion efficiency, and difficulty in achieving output stability.

[0006] A direct liquid fuel cell with an anode flow field, comprising: Anode collector; Cathode current collector; A membrane electrode assembly is sandwiched between the anode current collector and the cathode current collector; and An anode flow field plate is disposed between the anode current collector and the membrane electrode assembly; the anode flow field plate is made of a hydrophobic porous layer to capture and discharge bubbles generated by the anode in situ; the anode flow field plate is provided with an interdigitated flow field to allow liquid fuel to enter the membrane electrode assembly in a forced convection manner and carry dissolved oxygen in the membrane electrode assembly outward.

[0007] In one embodiment, the membrane electrode assembly includes a membrane electrode, an anode diffusion layer, and a cathode diffusion layer, wherein the anode diffusion layer and the cathode diffusion layer are respectively arranged on opposite sides of the membrane electrode, and the anode flow field plate is attached to the anode diffusion layer.

[0008] In one embodiment, the membrane electrode includes an anode catalyst layer, a cathode catalyst layer, and an ion exchange membrane. The anode catalyst layer and the cathode catalyst layer are respectively disposed on opposite sides of the ion exchange membrane. The anode diffusion layer is attached to the anode catalyst layer, and the cathode diffusion layer is attached to the cathode catalyst layer.

[0009] In one embodiment, slurries of the anode catalyst and the cathode catalyst are respectively sprayed and deposited on both sides of the ion exchange membrane, and then the membrane electrode is prepared by hot pressing, and the anode catalyst layer is hydrophilically treated.

[0010] In one embodiment, the cathode diffusion layer is a hydrophobic porous layer, and the anode diffusion layer is a hydrophilic porous layer.

[0011] In one embodiment, the anode flow field plate is composed of hydrophobic conductive fibers and is constructed into an interdigitated flow field using mechanical processing.

[0012] In one embodiment, the interdigitated flow field includes an inlet channel and an outlet channel, the inlet channel and the outlet channel at least partially overlapping and separated by a partition.

[0013] In one embodiment, a cathode flow field plate is also included, wherein the cathode flow field plate is provided with a baffle channel.

[0014] In one embodiment, the liquid fuel is a carbon-based liquid fuel or a nitrogen-based liquid fuel, and the cathode reactant is a gaseous oxidant or a liquid oxidant.

[0015] In one embodiment, the anolyte is a potassium hydroxide solution or a dilute sulfuric acid solution.

[0016] The direct liquid fuel cell with the above-mentioned anode flow field has at least the following advantages: 1. The use of an interdigitated anode flow field allows fuel to be transported via forced convection, which enhances mass transfer and improves battery performance; 2. The hydrophobic porous layer is directly connected to the outside atmosphere, which can achieve efficient capture of anode bubbles and in-situ discharge to the atmosphere, reducing the adverse effects of bubbles. At the same time, the hydrophobic material prevents leakage of anode liquid. 3. Forced convection can carry dissolved oxygen outwards, avoiding anodic oxygen permeation problems and improving battery output voltage and conversion efficiency; 4. Rapid in-situ discharge of bubbles can effectively reduce the inlet and outlet pressure drop caused by the interdigitated flow field, which is beneficial to reduce pump power loss and improve the net output power of the battery; 5. No complex additional equipment is required, achieving efficient passive bubble removal, and the battery combines conversion efficiency and output stability; 6. It can use different liquid fuels and oxidants, offering high flexibility and wide applicability. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly described below. In all the drawings, the elements or parts are not necessarily drawn to scale.

[0018] Figure 1 This is a schematic diagram of the structure of a direct liquid fuel cell with an anode flow field in one embodiment; Figure 2 for Figure 1 Front view of a direct liquid fuel cell with the anode flow field shown; Figure 3 for Figure 1 Schematic diagram of the structure of the anode flow field plate; Figure 4 for Figure 1 Schematic diagram of the structure of the central cathode flow field plate; Figure 5 A schematic diagram illustrating the principle of forced convection of fuel and in-situ discharge of bubbles.

[0019] Figure label: 10-Anode collector plate, 12-Anode inlet, 14-Anode outlet, 20-Cathode collector plate, 30-Membrane electrode assembly, 32-Membrane electrode, 34-Anode diffusion layer, 36-Cathode diffusion layer, 40-Anode flow field plate, 41-Inlet flow channel, 42-Outlet flow channel, 43-Baffle, 44-Flow channel inlet, 45-Flow channel outlet, 50-Cathode flow field plate, 52-Baffled flow channel. Detailed Implementation

[0020] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention; therefore, the invention is not limited to the specific embodiments disclosed below.

[0021] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] Please see Figure 1 A direct liquid fuel cell with an anode flow field in one embodiment includes an anode current collector 10, a cathode current collector 20, a membrane electrode assembly 30, and an anode flow field plate 40.

[0024] The anode current collector 10 and the cathode current collector 20 are arranged parallel to each other at intervals, and the membrane electrode assembly 30 is sandwiched between the anode current collector 10 and the cathode current collector 20. The anode current collector 10 has an anode inlet 12 and an anode outlet 14. Liquid fuel enters the battery through the anode inlet 12. After an electrochemical oxidation reaction occurs in the membrane electrode assembly 30, the waste liquid is discharged through the anode outlet 14. The cathode current collector 20 has a cathode inlet and a cathode outlet. Oxidant enters the battery through the cathode inlet, undergoes a reduction reaction in the membrane electrode assembly 30, and is discharged through the cathode outlet after the reaction.

[0025] In one embodiment, both the anode current collector 10 and the cathode current collector 20 are made of high-strength conductive materials resistant to acid and alkali corrosion, preventing damage to the anode current collector 10 and the cathode current collector 20 from acid and alkali corrosion and ensuring the lifespan of the fuel cell. Specifically, the anode current collector 10 and the cathode current collector 20 can be made of titanium plates.

[0026] Please refer to the following: Figure 2In one embodiment, the membrane electrode assembly 30 includes a membrane electrode 32, an anode diffusion layer 34, and a cathode diffusion layer 36, with the anode diffusion layer 34 and cathode diffusion layer 36 respectively arranged on opposite sides of the membrane electrode 32. The anode diffusion layer 34 faces the anode current collector 10, and the cathode diffusion layer 36 faces the cathode current collector 20. The anode diffusion layer 34 can uniformly distribute the liquid fuel, and the cathode diffusion layer 36 can uniformly distribute the oxidant. Both the anode diffusion layer 34 and the cathode diffusion layer 36 can support the membrane electrode 32.

[0027] In one embodiment, the anode diffusion layer 34 is a hydrophilic porous layer. Specifically, the anode diffusion layer 34 may be a hydrophilic porous carbon paper with oxygen-containing groups. The cathode diffusion layer 36 is a hydrophobic porous layer. Specifically, the cathode diffusion layer 36 may be a porous carbon paper with a PTFE (polytetrafluoroethylene) coating.

[0028] In one embodiment, the membrane electrode 32 includes an anode catalyst layer, a cathode catalyst layer, and an ion exchange membrane. The anode catalyst layer and the cathode catalyst layer are respectively disposed on opposite sides of the ion exchange membrane. The anode diffusion layer 34 is attached to the anode catalyst layer, and the cathode diffusion layer 36 is attached to the cathode catalyst layer. The anode catalyst layer is used to catalyze the oxidation of liquid fuels, and the cathode catalyst layer is used to catalyze the oxygen reduction reaction of the oxidant.

[0029] In one embodiment, the slurries for the anode and cathode catalysts are deposited on both sides of the ion exchange membrane using a spraying method, and then the membrane electrode 32 is fabricated by hot pressing. The anode catalyst layer is then subjected to a hydrophilic treatment. Specifically, the anode catalyst can be a Pt-based catalyst, such as a Pt / C catalyst or a PtM / C alloy catalyst. The cathode catalyst can be Pt or its alloy catalysts.

[0030] An anode flow field plate 40 is disposed between the anode flow field plate 40 and the membrane electrode assembly 30. The anode flow field plate 40 is made of a hydrophobic porous layer to capture and discharge bubbles generated at the anode in situ. The anode flow field plate 40 has an interdigitated flow field to force liquid fuel into the membrane electrode assembly 30 via convection and to carry dissolved oxygen within the membrane electrode assembly 30 outward.

[0031] Since the anode flow field plate 40 is made of a hydrophobic porous layer, which is directly connected to the outside atmosphere, the bubbles generated on the anode surface are transported to the hydrophobic porous layer / electrolyte interface through the anode diffusion layer 34. Under the action of surface tension, the bubbles burst. Since the anode flow field plate 40 is directly connected to the outside atmosphere, the bubbles are directly discharged from the anode flow field plate 40 to the atmosphere in situ, without having to be discharged through the anode outlet 14. At the same time, the hydrophobic porous layer can ensure that the liquid phase reactants do not leak.

[0032] Furthermore, since the hydrophobic porous layer is connected to the outside atmosphere, oxygen in the air will diffuse through the hydrophobic porous layer to the anode diffusion layer 34 to form dissolved oxygen. The anode flow field plate 40 is provided with an interdigitated flow field, and the forced convection in the anode diffusion layer 34 can carry the dissolved oxygen and discharge it through the anode outlet 14.

[0033] In one embodiment, the anode flow field plate 40 is composed of hydrophobic conductive fibers, and an interdigitated flow field is constructed using a machining method. Specifically, the hydrophobic conductive fibers can be titanium fibers with a hydrophobic SiO2 nanoparticle coating, and the machining method can be laser cutting, etc.

[0034] Please refer to the following: Figure 3 In one embodiment, the interdigitated flow field includes an inlet channel 41 and an outlet channel 42, which at least partially overlap and are separated by a partition 43. Specifically, both the inlet channel 41 and the outlet channel 42 are provided in multiple sets, which are interleaved and spaced apart. The multiple sets of inlet channels 41 are connected to the anode inlet 12 through channel inlets 44, and the multiple sets of outlet channels 42 are connected to the anode outlet 14 through channel outlets 45.

[0035] Please refer to the following: Figure 4 In one embodiment, a cathode flow field plate 50 is further included, which is disposed between the cathode current collector 20 and the membrane electrode assembly 30. Specifically, the cathode flow field plate 50 is located between the cathode diffusion layer 36 and the cathode current collector 20. The cathode flow field plate 50 has a baffle channel 52, which can increase the flow length of the oxidant and improve the diffusion effect of the oxidant within the cathode diffusion layer 36.

[0036] Please refer to it again. Figure 1 and Figure 2 In one embodiment, airtight gaskets are provided between the cathode current collector 20, the cathode flow field plate 50, the membrane electrode assembly 30, the anode flow field plate 40, and the anode current collector 10 to seal the gaps between them. Then, the entire battery is connected by bolts to achieve pressure sealing as a whole.

[0037] In one embodiment, the liquid fuel is either a carbon-based liquid fuel or a nitrogen-based liquid fuel. For example, the carbon-based liquid fuel can be methanol, formic acid, etc., and the nitrogen-based liquid fuel can be liquid ammonia, hydrazine, etc. The anolyte is a potassium hydroxide solution or a dilute sulfuric acid solution, which is delivered by a pump. The cathode reactant is a gaseous oxidant (such as oxygen) or a liquid oxidant (such as hydrogen peroxide), which is supplied by a gas flow meter or a pump.

[0038] Specifically, when the liquid fuel is methanol, the anodic oxidation reaction is as follows:

[0039] Cathode oxygen reduction reaction:

[0040] Overall response:

[0041] When the liquid fuel is ethanol, the anodic oxidation reaction is as follows:

[0042] Cathode oxygen reduction reaction:

[0043] Overall response:

[0044] When the liquid fuel is formic acid, the anodic oxidation reaction is as follows:

[0045] Cathode oxygen reduction reaction:

[0046] Overall response:

[0047] When the liquid fuel is hydrazine fuel, the anodic oxidation reaction is as follows:

[0048] Cathode oxygen reduction reaction:

[0049] Overall response:

[0050] When the liquid fuel is ammonia, the anodic oxidation reaction is as follows: Anodizing reaction

[0051] Cathode oxygen reduction reaction

[0052] Overall Response

[0053] Please refer to the following: Figure 5 The working principle of the direct liquid fuel cell with the above-mentioned anolyte flow field is as follows: When the battery is running, liquid fuel enters from the anode inlet 12 and flows along the interdigitated flow field. It is then transported within the anode diffusion layer 34 by forced convection and undergoes an electrochemical oxidation reaction on the surface of the anode catalyst layer. At this time, the bubbles generated on the anode surface are transported through the anode diffusion layer 34 to the anode flow field plate 40, where they are captured and discharged in situ to the outside atmosphere, ensuring that the liquid phase reactants do not leak.

[0054] Oxygen from the air diffuses through the anode flow field plate 40 to the anode diffusion layer 34, forming dissolved oxygen. Under forced convection, the dissolved oxygen in the anode diffusion layer 34 flows with the electrolyte to the flow channel outlet 45, preventing oxygen permeation. The waste liquid after the reaction is discharged through the flow channel outlet 45. Electrons are conducted to the cathode catalyst layer through the external circuit. On the cathode side, the oxidant is transported to the cathode catalyst layer through the cathode diffusion layer 36 via convection / diffusion, where it combines with electrons to undergo a reduction reaction. Ions within the membrane are transported across the membrane via electromigration or diffusion.

[0055] The direct liquid fuel cell with the above-mentioned anode flow field has at least the following advantages: 1. The use of an interdigitated anode flow field allows fuel to be transported via forced convection, which enhances mass transfer and improves battery performance; 2. The hydrophobic porous layer is directly connected to the outside atmosphere, which can achieve efficient capture of anode bubbles and in-situ discharge to the atmosphere, reducing the adverse effects of bubbles. At the same time, the hydrophobic material prevents leakage of anode liquid. 3. Forced convection can carry dissolved oxygen outwards, avoiding anodic oxygen permeation and improving battery output voltage and conversion efficiency; 4. Rapid in-situ discharge of bubbles can effectively reduce the inlet and outlet pressure drop caused by the interdigitated flow field, which is beneficial to reduce pump power loss and improve the net output power of the battery; 5. No complex additional equipment is required, achieving efficient passive bubble removal, and the battery combines conversion efficiency and output stability; 6. It can use different liquid fuels and oxidants, offering high flexibility and wide applicability.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A direct liquid fuel cell with an anode flow field, characterized in that, include: Anode collector; Cathode current collector; A membrane electrode assembly is sandwiched between the anode current collector and the cathode current collector; and An anode flow field plate is disposed between the anode current collector and the membrane electrode assembly; the anode flow field plate is made of a hydrophobic porous layer to capture and discharge bubbles generated by the anode in situ. The anode flow field plate is provided with an interdigitated flow field, so that liquid fuel enters the membrane electrode assembly in a forced convection manner and carries the dissolved oxygen in the membrane electrode assembly outward.

2. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, The membrane electrode assembly includes a membrane electrode, an anode diffusion layer, and a cathode diffusion layer. The anode diffusion layer and the cathode diffusion layer are respectively arranged on opposite sides of the membrane electrode, and the anode flow field plate is attached to the anode diffusion layer.

3. The direct liquid fuel cell with an anode flow field according to claim 2, characterized in that, The membrane electrode includes an anode catalyst layer, a cathode catalyst layer, and an ion exchange membrane. The anode catalyst layer and the cathode catalyst layer are respectively disposed on opposite sides of the ion exchange membrane. The anode diffusion layer is attached to the anode catalyst layer, and the cathode diffusion layer is attached to the cathode catalyst layer.

4. The direct liquid fuel cell with an anode flow field according to claim 3, characterized in that, The slurries of the anode catalyst and the cathode catalyst are respectively sprayed and deposited on both sides of the ion exchange membrane, and then the membrane electrode is prepared by hot pressing, and the anode catalyst layer is hydrophilically treated.

5. The direct liquid fuel cell with an anode flow field according to claim 2, characterized in that, The cathode diffusion layer is a hydrophobic porous layer, and the anode diffusion layer is a hydrophilic porous layer.

6. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, The anode flow field plate is composed of hydrophobic conductive fibers and is constructed into an interdigitated flow field using mechanical processing.

7. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, The interdigitated flow field includes an inlet channel and an outlet channel, which at least partially overlap and are separated by a partition.

8. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, It also includes a cathode flow field plate, which is provided with a baffle channel.

9. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, The liquid fuel is either carbon-based or nitrogen-based, and the cathode reactant is either a gaseous oxidant or a liquid oxidant.

10. The direct liquid fuel cell with an anode flow field according to claim 1, characterized in that, The anolyte is a potassium hydroxide solution or a dilute sulfuric acid solution.

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