Self-heat balance high-temperature proton exchange membrane fuel cell stack

Abstract

The invention provides a self-heat balance high-temperature proton exchange membrane fuel cell stack which comprises an anode plate, a membrane electrode and a cathode plate, and the anode plate, the membrane electrode and the cathode plate are repeatedly stacked to form a stack cell; the membrane electrode comprises a double-catalyst-layer anode gas diffusion electrode, an electrolyte membrane and a cathode gas diffusion electrode which are arranged in sequence; the double-catalyst-layer anode gas diffusion electrode comprises an anode gas diffusion layer, an anode outer catalyst layer and an anode inner catalyst layer which are arranged in sequence, and the anode inner catalyst layer is close to the electrolyte membrane; the cathode gas diffusion electrode comprises a cathode gas diffusion layer and a cathode catalyst layer which are arranged in sequence, and the cathode catalyst layer is close to the electrolyte membrane; wherein the anode outer catalyst layer is used for carrying out methanol reforming hydrogen production reaction by taking methanol steam as a reactant to generate hydrogen-rich gas; and the anode inner catalyst layer takes the hydrogen-rich gas as a raw material to generate a hydrogen oxidation reaction to generate protons.

Description

Technical Field

[0001] This invention relates to the field of high-temperature proton exchange membrane fuel cells, and more specifically, to a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack. Background Technology

[0002] High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have broad application prospects in portable power sources, mobile power stations, combined heat and power, and vehicle and ship power due to their high operating temperature (typically 120℃-200℃), strong tolerance to carbon monoxide (CO) in fuel gas (up to 3%), and the ability to directly use methanol reformed gas as fuel.

[0003] Currently, mainstream high-temperature proton exchange membrane fuel cell technology is mainly based on phosphate-doped polybenzimidazole (PBI) membrane systems. In actual operation, the voltage efficiency of the fuel cell stack is typically between 45% and 50%, meaning that a large amount of chemical energy is converted into heat energy during power generation. To maintain the fuel cell stack at a suitable operating temperature and prevent overheating, effective heat dissipation management is essential. Traditional thermal management solutions integrate cooling plates into key components of the fuel cell stack (such as bipolar plates) and set cooling channels within the cooling plates. The cooling medium is usually air or liquid (such as triethylene glycol). In addition, to achieve cooling circulation, the system also needs to be equipped with corresponding cooling subsystems, such as air-cooled systems and liquid-cooled systems. For air-cooled systems, components such as cooling fans, air pumps, and piping are required; for liquid-cooled systems, components such as liquid storage tanks, liquid pumps, heaters, radiators, and complex piping are required.

[0004] However, the aforementioned traditional thermal management solutions have significant drawbacks: First, the cooling plates integrated inside the fuel cell stack significantly increase the stack's mass and volume, thereby reducing its mass power density and volumetric power density. Second, the additional air-cooled or liquid-cooled subsystems added to achieve cooling introduce a large number of auxiliary components (BOPs), which not only increases the system's complexity and cost, but also generates considerable parasitic power consumption during operation (such as the power consumption of pumps and fans), ultimately leading to a decrease in the mass power density, volumetric power density, and overall system efficiency of the entire fuel cell system. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of low power density and low efficiency in existing high-temperature proton exchange membrane fuel cell stacks and systems with cooling structures.

[0006] Based on the above, the present invention provides a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack, including an anode plate, a membrane electrode assembly (MEA) and a cathode plate, wherein the anode plate, MEA and cathode plate are repeatedly stacked to form a stack cell; the MEA comprises a double-catalytic layer anode gas diffusion electrode, an electrolyte membrane and a cathode gas diffusion electrode arranged sequentially. The dual-catalytic-layer anode gas diffusion electrode comprises an anode gas diffusion layer, an outer anode catalyst layer, and an inner anode catalyst layer arranged sequentially, with the inner anode catalyst layer close to the electrolyte membrane; the cathode gas diffusion electrode comprises a cathode gas diffusion layer and a cathode catalyst layer arranged sequentially, with the cathode catalyst layer close to the electrolyte membrane. The outer catalytic layer of the anode is used to produce hydrogen-rich gas through methanol reforming with methanol and water vapor as reactants; the inner catalytic layer of the anode uses the hydrogen-rich gas as raw material to produce protons through a hydrogenation reaction.

[0007] Optionally, the outer catalytic layer of the anode comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises palladium copper.

[0008] Optionally, the loading of noble metals in the outer catalyst layer of the anode is 10 mg / cm³. 2 -50 mg / cm 2 The content of ionomers is 5%-15%.

[0009] Optionally, the inner catalyst layer of the anode comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises any one of platinum-ruthenium or platinum-palladium.

[0010] Optionally, the noble metal loading in the inner catalyst layer of the anode is 0.05 mg / cm³. 2 -1.0 mg / cm 2 The content of ionomers is 10%-30%.

[0011] Optionally, the cathode catalyst layer comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises platinum or platinum-cobalt, wherein the mass fraction of the noble metal is 20%-80%, and the loading of the noble metal is 0.05 mg / cm³. 2 -2.0 mg / cm 2 The content of ionomers is 5%-30%.

[0012] Optionally, the electrolyte membrane includes a sol-gel type PBI membrane or a solid acid-coupled ultra-high temperature proton exchange membrane, wherein the phosphoric acid doping amount is 500wt%-1000wt%.

[0013] Optionally, the thickness of the electrolyte membrane is 100 μm-400 μm.

[0014] Optionally, the operating temperature of the fuel cell stack is 210°C, and the current density is 0.3 A / cm². 2 The fuel cell stack is in a state of self-heating equilibrium.

[0015] Optionally, the heat generated by the fuel cell stack is equivalent to the heat required for the following applications: methanol steam preheating, methanol reforming for hydrogen production endothermic, radiative heat dissipation, and natural convection heat dissipation.

[0016] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention proposes a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack based on low-temperature methanol reforming hydrogen production technology and ultra-high temperature proton exchange membrane fuel cell technology. The stack mainly consists of uncooled bipolar plate components and in-situ coupled high-temperature membrane electrodes for methanol hydrogen production and power generation. The stack can be started up by electric heating, air preheating, etc. At the rated point, the heat generated by the stack is mainly used for the methanol reforming hydrogen production reaction, without the need for auxiliary heat dissipation. The stack itself is in a self-heating equilibrium state, which can solve the problems of low power density and low efficiency of existing high-temperature fuel cell stacks with cooling structures. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack structure provided in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the membrane electrode structure in one embodiment of the present invention.

[0019] Figure 3 This is a temperature distribution diagram of a single cell during startup of a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack using PI membrane heating, as provided in an embodiment of the present invention.

[0020] Figure 4 The temperature and voltage distribution of a single cell in a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack provided in this embodiment of the invention.

[0021] Figure 5 The graph shows the temperature and voltage of a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack over time, as provided in an embodiment of the present invention.

[0022] Attached image labels: End plate 10, anode plate 20, membrane electrode 30, cathode plate 40, double catalytic layer anode gas diffusion electrode 31, electrolyte membrane 32, cathode gas diffusion electrode 33, anode gas diffusion layer 311, anode outer catalytic layer 312, anode inner catalytic layer 313, cathode gas diffusion layer 331, cathode catalytic layer 332. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] As described in the background section, the current mainstream high-temperature proton exchange membrane fuel cell technology is based on the phosphoric acid-doped (PBI) system. In actual operation, the voltage efficiency of the fuel cell stack is between 45% and 50%. Heat generation during power generation necessitates heat dissipation to prevent overheating. Existing solutions integrate cooling plates into key components (such as bipolar plates) and equip the stack with corresponding cooling subsystems. The former significantly increases the stack's mass and volume, thus reducing its mass power density and volumetric power density. The latter introduces numerous auxiliary components (BOP), ultimately leading to a decrease in the overall mass power density, volumetric power density, and system efficiency of the fuel cell system.

[0025] Therefore, there is an urgent need in this field to develop a novel battery stack structure or thermal management scheme that can simplify the system structure, reduce parasitic energy consumption, and ultimately improve the power density and energy utilization efficiency of the stack and the entire system, while ensuring the efficient and stable operation of high-temperature proton exchange membrane fuel cells.

[0026] To solve the above technical problems, such as Figure 1 As shown, the present invention proposes a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack (hereinafter referred to as "fuel cell"), comprising: two end plates 10, and a stack cell located between the two end plates 10, wherein the stack cell is formed by repeatedly stacking an anode plate 20, a membrane electrode 30, and a cathode plate 40. Figure 1 Only one repeating unit is shown; where: The end plate 10 is made of stainless steel or titanium alloy and is used to provide mechanical support for the fuel cell and to collect and export the electrons generated by the fuel cell to an external circuit. The end plate 10 is provided with an end plate inlet and an end plate outlet for introducing reactants and discharging products, respectively. The reactants include methanol vapor and air, and the products include water.

[0027] The anode plate 20 and cathode plate 40 are made of graphite resin composite material, or stainless steel, aluminum alloy, or other materials plated with gold or platinum. A multi-channel flow field is etched onto the anode plate 20 and cathode plate 40, including at least one of point flow field, parallel flow field, and serpentine flow field. The inlet and outlet of the multi-channel flow field of the anode plate 20 are connected to the end plate inlet and outlet of the anode-side end plate, respectively, for the introduction of methanol water vapor and the outflow of anode-side products; the inlet and outlet of the multi-channel flow field of the cathode plate 40 are connected to the end plate inlet and outlet of the cathode-side end plate, respectively, for the introduction of air and the outflow of cathode-side products.

[0028] like Figure 2 As shown, the membrane electrode 30 comprises a double-catalytic-layer anode gas diffusion electrode 31, an electrolyte membrane 32, and a cathode gas diffusion electrode 33 arranged sequentially. Wherein: The dual-catalytic-layer anode gas diffusion electrode 31 comprises an anode gas diffusion layer 311, an outer anode catalyst layer 312, and an inner anode catalyst layer 313 arranged sequentially, with the inner anode catalyst layer 313 located close to the electrolyte membrane 32. Under process conditions, methanol and water vapor from the anode gas diffusion layer 311 first contact the catalyst in the outer anode catalyst layer 312, resulting in a methanol reforming reaction to produce hydrogen-rich gas. This hydrogen-rich gas then diffuses into the inner anode catalyst layer 313, where, under the action of the catalyst, a hydrogen-rich gas-fuel reaction occurs, producing protons.

[0029] In some embodiments, the anode gas diffusion layer is carbon paper or carbon cloth; the outer anode catalyst layer 312 comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises palladium copper, and the noble metal loading is 10 mg / cm³. 2 -50 mg / cm 2 The content of the ionomer is 5%-15%; the inner catalyst layer of the anode comprises: a carbon-supported noble metal catalyst and the ionomer, wherein the noble metal comprises any one of platinum-ruthenium or platinum-palladium, and the loading of the noble metal is 0.05 mg / cm³. 2 -1.0 mg / cm 2 The content of ionomers is 10%-30%.

[0030] The electrolyte membrane 32 serves two purposes: firstly, it transfers the protons generated by the catalyst layer 313 inside the anode to the cathode gas diffusion electrode 33 to undergo an electrochemical reaction and produce water; secondly, it blocks methanol water vapor and air from both sides of the electrolyte membrane 32.

[0031] In some embodiments, the electrolyte membrane 32 comprises a sol-gel type PBI membrane or a solid acid-coupled ultra-high temperature proton exchange membrane, wherein the phosphoric acid doping amount is 500wt%-1000wt%. The electrolyte membrane 32 has a thermal stability above 300℃, and at 0%RH, the proton conductivity of the electrolyte membrane 32 is between 0.1 S / cm and 0.2 S / cm.

[0032] In some embodiments, the thickness of the electrolyte membrane 32 is 100 μm-400 μm.

[0033] The cathode gas diffusion electrode 33 includes a cathode gas diffusion layer 331 and a cathode catalyst layer 332 arranged sequentially, with the cathode catalyst layer 332 adjacent to the electrolyte membrane 32. Under process conditions, protons generated in the anolyte catalyst layer 313 pass through the electrolyte membrane 32 into the cathode catalyst layer 332, where an electrochemical reduction reaction (cathode reaction) occurs under the action of the catalyst: O2 + 4H₂O + +4e - →2H2O, producing water.

[0034] In some embodiments, the cathode catalyst layer 332 comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises platinum or platinum-cobalt, wherein the mass fraction of the noble metal is 20%-80%, and the loading of the noble metal is 0.05 mg / cm³. 2 -2.0mg / cm 2 The content of ionomers is 5%-30%.

[0035] The operation process of the self-heating equilibrium high-temperature proton exchange membrane fuel cell stack is as follows: First, the fuel cell is started by heating the stack with electric heating elements or by preheating the air. Methanol vapor, formed by the evaporation of a methanol-water solution, enters the inlet of the multi-channel flow field on the surface of the anode plate 20 through the endplate inlet of the anode side endplate. It flows along the multi-channel flow field and further enters the outer catalyst layer 312 of the anode through the anode gas diffusion layer 311 to undergo methanol reforming to produce hydrogen gas. The hydrogen-rich gas then flows to the inner catalyst layer 313 of the anode to undergo a hydrogen oxidation reaction, producing protons. Simultaneously, air enters the inlet of the multi-channel flow field on the surface of the cathode plate 40 through the endplate inlet of the cathode side endplate. It flows along the multi-channel flow field and further enters the cathode catalyst layer 332 through the air cathode gas diffusion layer 331, where it reacts with H2O entering from the electrolyte membrane 32. + Electrons entering the external circuit undergo a cathode reaction, converting chemical energy into electrical energy. The fuel cell stack typically operates at 180℃-210℃, while the methanol-water solution evaporates at around 100℃. The heat generated by the fuel cell stack can be used for the evaporation of the methanol-water solution.

[0036] During the above operation, the heat generated by the cathode reaction at the rated point is used for methanol steam preheating, methanol reforming to produce hydrogen endothermic, radiative heat dissipation, and natural convection heat dissipation. The fuel cell stack does not require additional cooling systems (such as air cooling systems or liquid cooling systems) or components (such as cooling plates). The fuel cell stack itself is in a state of self-thermal equilibrium, which effectively reduces the overall system volume and the overall system start-up time, thereby effectively improving the specific power and efficiency of the fuel cell system.

[0037] Example This embodiment provides a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack, including: a front end plate, a front insulating plate, a front current collector, a cathode monopole plate, one dummy electrode, 20 repeating units, one dummy electrode, an anode monopole plate, a rear current collector, a rear insulating plate, and a rear end plate. The repeating unit includes: an anode plate, a membrane electrode assembly, and a cathode plate.

[0038] The anode plate and cathode plate are graphite resin composite plates, with 3-channel serpentine flow fields and 5-channel serpentine flow fields respectively. The edges of the anode plate and cathode plate are engraved with sealing grooves, and high-temperature resistant fluororubber sealing gaskets are attached to the grooves.

[0039] The membrane electrode is a high-temperature membrane electrode for an in-situ coupled phosphate-doped PBI system used in methanol-to-hydrogen and power generation. It mainly consists of an electrolyte membrane, a dual-catalytic-layer anode gas diffusion electrode, and a cathode gas diffusion electrode. The electrolyte membrane is a sol-gel type PBI membrane with a thickness of 200 μm and a phosphate doping concentration of 500 wt%. At 0% RH, the proton conductivity of the electrolyte membrane is 0.15 S / cm at 200℃. The dual-catalytic-layer anode gas diffusion electrode comprises a sequentially arranged anode gas diffusion layer, an outer anode catalyst layer, and an inner anode catalyst layer. The outer anode catalyst layer is composed of PdCu / C and an ionomer, with a noble metal loading of 20 mg / cm³. 2 The content of ionomers is 10%; the inner catalyst layer of the anode is composed of PtRu / C and ionomers, and the loading of noble metals in the inner catalyst layer is 0.5 mg / cm³. 2 The content of the ionomer is 10%; the cathode gas diffusion electrode comprises a cathode gas diffusion layer and a cathode catalyst layer arranged sequentially. The cathode catalyst layer is composed of PtCo / C and the ionomer, with the mass fraction of noble metal in PtCo / C being 50% and the noble metal loading being 1.0 mg / cm³. 2 The content of ionomers is 20%.

[0040] The front and rear end plates are made of aluminum alloy, and the front and rear insulating plates are made of PEEK material; the cathode and anode monopolar plates are high-temperature resistant graphite plates, and air and methanol water vapor flow through the flow channels of the cathode and anode monopolar plates, respectively; the dummy electrode is a graphite sheet.

[0041] See Figure 3 In this embodiment, the fuel cell stack startup method is as follows: PI thin-film heating pads are attached to the top and bottom surfaces of the fuel cell stack core. These heating pads are parallel to the stacking direction and contact each anode and cathode plate to uniformly heat the stack. After 25 minutes of startup, all individual cells in the stack reach 120°C. The individual cells at the two ends of the stack have the lowest temperature, while the individual cell corresponding to the middle position of the PI thin-film heating pad has the highest temperature. The temperature difference between the highest and lowest individual cells is approximately 10°C.

[0042] See Figure 4 The fuel cell stack is at 0.3 A / cm 2Once the stack reaches self-thermal equilibrium, the PI film heating element ceases operation. The heat generated by the stack is primarily used for methanol reforming to produce hydrogen, radiative cooling, and natural convection cooling. The temperature and voltage of individual cells are highest on the middle side of the stack, and lowest on the sides. The highest temperature of a single cell reaches 210℃, and the lowest reaches 182℃. The highest voltage of a single cell is 0.626V, and the lowest is 0.572V.

[0043] See Figure 5 It can be seen that the fuel cell stack provided in this embodiment can operate continuously and stably for 24 hours at 210°C, with the stack voltage maintained between 12.22V and 12.32V.

[0044] In summary, this invention provides a self-heating equilibrium high-temperature proton exchange membrane fuel cell stack. At rated point, the heat generated by this stack is mainly used for the methanol reforming hydrogen production reaction without the need for auxiliary heat dissipation. The stack itself is in a self-heating equilibrium state, and no additional cooling system (such as air cooling system or liquid cooling system) or components are required. This can solve the problems of existing high-temperature fuel cell stacks with cooling structures, low system power density, and low efficiency.

[0045] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A self-heating equilibrium high-temperature proton exchange membrane fuel cell stack, characterized in that, It includes an anode plate, a membrane electrode, and a cathode plate, which are repeatedly stacked to form a battery cell; the membrane electrode comprises a double-catalytic-layer anode gas diffusion electrode, an electrolyte membrane, and a cathode gas diffusion electrode arranged sequentially. The dual-catalytic-layer anode gas diffusion electrode comprises an anode gas diffusion layer, an outer anode catalyst layer, and an inner anode catalyst layer arranged sequentially, with the inner anode catalyst layer close to the electrolyte membrane; the cathode gas diffusion electrode comprises a cathode gas diffusion layer and a cathode catalyst layer arranged sequentially, with the cathode catalyst layer close to the electrolyte membrane. The outer catalytic layer of the anode is used to produce hydrogen-rich gas through methanol reforming with methanol and water vapor as reactants; the inner catalytic layer of the anode uses the hydrogen-rich gas as raw material to produce protons through a hydrogenation reaction.

2. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The outer catalytic layer of the anode comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises palladium copper.

3. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 2, characterized in that, The noble metal loading in the outer catalyst layer of the anode is 10 mg / cm³. 2 -50 mg / cm 2 The content of ionomers is 5%-15%.

4. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The inner catalyst layer of the anode comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises any one of platinum and ruthenium, or platinum and palladium.

5. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 4, characterized in that, The noble metal loading in the inner catalyst layer of the anode is 0.05 mg / cm³. 2 -1.0 mg / cm 2 The content of ionomers is 10%-30%.

6. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The cathode catalyst layer comprises: a carbon-supported noble metal catalyst and an ionomer, wherein the noble metal comprises platinum and platinum-cobalt, wherein the mass fraction of the noble metal is 20%-80%, and the loading of the noble metal is 0.05 mg / cm³. 2 -2.0 mg / cm 2 The content of ionomers is 5%-30%.

7. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The electrolyte membrane includes a sol-gel type PBI membrane or a solid acid-coupled ultra-high temperature proton exchange membrane, wherein the phosphoric acid doping amount is 500wt%-1000wt%.

8. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The thickness of the electrolyte membrane is 100 μm-400 μm.

9. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 1, characterized in that, The fuel cell stack operates at a temperature of 210°C and a current density of 0.3 A / cm². 2 The fuel cell stack is in a state of self-heating equilibrium.

10. The self-heating equilibrium high-temperature proton exchange membrane fuel cell stack as described in claim 9, characterized in that, The heat generated by the fuel cell stack is equivalent to the heat required for the following applications: methanol steam preheating, methanol reforming for hydrogen production endothermic, radiative heat dissipation, and natural convection heat dissipation.

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