A membrane electrode for high temperature proton exchange membrane fuel cells and a method of making the same

Abstract

The application discloses a membrane electrode for high-temperature proton exchange membrane fuel cells and a preparation method thereof, and the membrane electrode has a ionomer layer and is a multilayer structure sequentially composed of a conductive substrate, a catalytic layer, the ionomer layer, a high-temperature proton exchange membrane, the ionomer layer, the catalytic layer and the conductive substrate, wherein the ionomer layer takes one or more polymers of polybenzimidazole or derivatives thereof as a main component, is doped with one or more conductive agents of carbon powder or derivatives thereof to form a composite material, and forms the ionomer layer on the surface of the catalytic layer. In the application, the structure control of the ionomer layer is introduced to control the distribution of electrolytes represented by phosphoric acid, more three-phase interface sites are constructed, the membrane electrode has high peak power density and high current density, the preparation process is simple and low in cost, the membrane electrode is applied to various high-temperature proton exchange membrane fuel cells, and has large-scale production and application potential.

Description

Technical Field

[0001] This invention belongs to the field of electrode materials, specifically relating to a membrane electrode for high-temperature proton exchange membrane fuel cells and its preparation method. Background Technology

[0002] High-temperature proton exchange membrane fuel cells (PEMFCs) utilize compounds such as hydrogen, methanol, ethanol, and hydrocarbons as fuels. Operating at 120-200°C, they can perform redox reactions within the membrane cell, effectively converting the chemical energy of the fuel into electrical and thermal energy. Compared to low-temperature PEMFCs, they exhibit higher tolerance to impurity fuels such as CO, faster reaction kinetics, and simpler water management systems. Therefore, they are easier to integrate into systems, promoting large-scale applications and demonstrating significant advantages and promising prospects as power generation devices.

[0003] Although high-temperature proton exchange membrane fuel cells (HTEMs) show great promise, the technology still has unresolved drawbacks, such as low power density and short battery life. In HTEMs, the conductivity of the proton exchange membrane does not originate from water but from phosphoric acid. Therefore, before battery assembly, the HTEM is typically soaked in phosphoric acid to improve its conductivity. However, during assembly and long-term operation, a significant amount of phosphoric acid is lost, leading to catalyst poisoning and a decrease in the conductivity of the HTEM, consequently resulting in a decrease in power density. The literature (International Journal of Hydrogen Energy, 2020, 45, 1008-1017) reports a HTEM with a three-layer polybenzimidazole structure for controlling the electrolyte distribution in HTEMs, achieving a power density of 0.2 A cm⁻¹ after activation. -2 After single-cell testing with current loading, the voltage remained at 0.65V, with a peak power of 359mW / cm². -2 The literature (Nano Energy, 2021, 93, 106829) reports a membrane electrode structure with monolayer graphene for controlling the electrolyte distribution in high-temperature proton exchange membrane fuel cells. After activation, it operates at 0.49 A cm⁻¹. -2 After single-cell testing with current loading, the voltage remained at 0.60V, with a peak power of 470mW / cm². -2 Chinese patent (publication number CN105742649B) discloses a high-temperature proton exchange membrane fuel cell membrane electrode and its preparation method. By pre-treating the gas diffusion electrode with acid before press-fitting it into a membrane electrode, the distribution of the electrolyte can be better controlled. Under this method, the current density at 0.6V is 0.3A cm⁻¹. -2 Peak power is 302mW cm -2 .

[0004] In summary, current literature and disclosed patents indicate that membrane electrode assemblies (MEAs) for high-temperature fuel cells primarily control electrolyte distribution through structural design, but they still exhibit relatively low current density and peak power density, requiring further improvement. Summary of the Invention

[0005] The main objective of this invention is to provide a membrane electrode for a high-temperature proton exchange membrane fuel cell, wherein an ionomer layer is added between the catalyst layer and the high-temperature proton exchange membrane.

[0006] Another object of the present invention is to provide a method for preparing the membrane electrode for a high-temperature proton exchange membrane fuel cell.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The present invention provides a membrane electrode for a high-temperature proton exchange membrane fuel cell, which is a multilayer structure consisting of a conductive substrate, a catalyst layer, an ionomer layer, a high-temperature proton exchange membrane, an ionomer layer, a catalyst layer, and a conductive substrate in sequence. The ionomer layer is composed of one or more polymers of polybenzimidazole or its derivatives as the main component, and is doped with one or more conductive agents of carbon powder or its derivatives to form a composite material. The ionomer layer is formed on the surface of the catalyst layer.

[0009] Preferably, the loading of one or more polymers of polybenzimidazole or its derivatives in the ionomer layer is 0.1–0.5 mg / cm³. -2 .

[0010] Preferably, the conductive substrate is carbon paper or carbon cloth having a gas diffusion layer and / or a microporous layer.

[0011] Preferably, the catalyst layer is a composite material formed by a Pt-based catalyst and a hydrophobic binder through a deposition process, wherein the mass ratio of the hydrophobic binder to the Pt-based catalyst is 1:5-20, and the hydrophobic binder is selected from polytetrafluoroethylene and / or polyvinylidene fluoride.

[0012] Preferably, the high-temperature proton exchange membrane is one or more polymers of acid-treated polybenzimidazole or its derivatives.

[0013] The present invention also provides a method for preparing the membrane electrode for a high-temperature proton exchange membrane fuel cell, comprising the following steps:

[0014] (1) Using water, ethanol, or isopropanol in any proportion as a dispersant, add Pt-based catalyst powder as an active ingredient, and a suspension of polytetrafluoroethylene and / or polyvinylidene fluoride as a binder, and sonicate the resulting slurry for 5-120 min to obtain a catalyst slurry.

[0015] (2) The catalyst slurry obtained in step (1) is coated onto the conductive substrate by air spraying, electrostatic spraying, ultrasonic spraying, scraping, screen printing, or roller pressing, and dried at 60-80℃ for 0.5-4h to obtain a conductive substrate with a catalyst layer.

[0016] (3) The conductive substrate with the catalyst layer obtained in step (2) is placed at 200-400℃ for 1-5 hours and then removed to obtain a gas diffusion electrode;

[0017] (4) Using one or more of dimethylformamide, or dimethylacetamide, or dimethyl sulfoxide, or N-methyl-2-pyrrolidone in any proportion as a dispersant, add one or more polymers of polybenzimidazole or its derivatives, with a solid-to-liquid mass ratio of 1:20 to 500, and heat the mixed solution at 100-250°C until the polymer is completely dissolved to obtain an organic solution;

[0018] (5) The organic solution obtained in step (4) is coated onto the surface of the catalyst layer by air spraying, electrostatic spraying, ultrasonic spraying, scraping, screen printing, or rolling, and dried at 80-160℃ for 0.5-3h to obtain the ionomer layer.

[0019] (6) A high-temperature proton exchange membrane is obtained by immersing one or more polymer films of polybenzimidazole or its derivatives with a thickness of 10-35 micrometers in a mixture of one or more of phosphoric acid, hydrochloric acid or sulfuric acid in any proportion at 80-120°C for 0.5-10 hours.

[0020] (7) The gas diffusion electrode, the high-temperature proton exchange membrane and the gas diffusion electrode are placed in sequence to form a sandwich structure, and hot-pressed for 1-8 minutes at 100-150℃ and 0.1-0.4MPa to obtain the membrane electrode.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. This invention proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, which has an ionomer layer. Compared with existing similar products, it has significant advantages in high peak power density and high current density. The preparation process is simple and low cost. It can be applied to membrane electrodes of various high-temperature proton exchange membrane fuel cells and has the potential for large-scale production and application.

[0023] 2. The basic materials of the ionomer layer are basically similar to or the same as those of high-temperature proton exchange membrane materials, so there is no need to introduce new materials, resulting in lower costs.

[0024] 3. To address the issue of low current and power density in membrane electrodes currently used in high-temperature proton exchange membrane fuel cells, this paper proposes to improve the power density and current density of a single cell in a high-temperature proton exchange membrane fuel cell by introducing an ionomer layer to control the distribution of electrolytes, such as phosphoric acid, and constructing more three-phase interface sites. This prevents excessive intrusion of electrolytes like phosphoric acid into the catalyst layer, thus preventing poisoning and maintaining the content of electrolytes like phosphoric acid within the high-temperature proton exchange membrane. Attached Figure Description

[0025] Figure 1 The polarization curves and power density curves of the membrane electrodes obtained in Examples 1, 2 and 3 are shown as single cells.

[0026] Figure 2 The polarization curves and power density curves of the membrane electrodes obtained in Examples 4 and 5 are shown as single cells.

[0027] Figure 3 This is a schematic diagram of the membrane electrode used in a high-temperature proton exchange membrane fuel cell according to the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, and its preparation steps are as follows:

[0031] 1) 0.85mg pt / cm 2 Pt / C and 20 wt.% polytetrafluoroethylene were mixed and ultrasonically dispersed for 90 min to obtain a mixed slurry.

[0032] 2) The mixed slurry was ultrasonically sprayed onto carbon paper, dried at 60°C for 1 hour, and then sintered at 350°C for 2 hours.

[0033] 3) Polybenzimidazole / dimethyl sulfoxide solutions were mixed at a mass ratio of 1:200 and dissolved by heating at 180°C to obtain an organic solution.

[0034] 4) The organic solvent is evenly sprayed onto the sintered carbon paper, with a polybenzimidazole loading of 0.15 mg / cm³. 2 Dry at 120℃ for 1 hour.

[0035] 5) Take a 25-micron thick polybenzimidazole film and immerse it in phosphoric acid at 120°C for 3 hours, then wipe off the excess phosphoric acid.

[0036] 6) Press the carbon paper obtained in 4) and the polybenzimidazole film obtained in 5) together to obtain a membrane electrode.

[0037] In single-cell testing, a supply of 0.3L min was used. -1 Hydrogen and 0.5L min -1 Air was used to provide a back pressure of 2 Bar, the test temperature was 180°C, and the carbon paper used was 39BB type carbon paper manufactured by SGL Carbon. Figure 1 The polarization curve and power density curve of the membrane electrode prepared in this embodiment as a single cell are shown. Figure 1 It is known that the peak power density of the membrane electrode with an ionomer layer used in high-temperature proton exchange membrane fuel cells is 638 mW / cm². -2 The current density at 0.6V is 502 mA cm⁻¹. -2 .

[0038] Example 2

[0039] This embodiment proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, and its preparation steps are as follows:

[0040] 1) 0.85mg pt / cm 2 Pt / C and 20 wt.% polytetrafluoroethylene were mixed and ultrasonically dispersed for 90 min to obtain a mixed slurry.

[0041] 2) The mixed slurry was ultrasonically sprayed onto carbon paper, dried at 60°C for 1 hour, and then sintered at 350°C for 2 hours.

[0042] 3) Polybenzimidazole / dimethyl sulfoxide solutions were mixed at a mass ratio of 1:200 and dissolved by heating at 180°C to obtain an organic solution.

[0043] 4) The organic solvent is evenly sprayed onto the sintered carbon paper, with a polybenzimidazole loading of 0.3 mg / cm³. 2 Dry at 120℃ for 1 hour.

[0044] 5) Take a 25-micron thick polybenzimidazole film and immerse it in phosphoric acid at 120°C for 3 hours, then wipe off the excess phosphoric acid.

[0045] 6) Press the carbon paper obtained in 4) and the polybenzimidazole film obtained in 5) together to obtain a membrane electrode.

[0046] In single-cell testing, a supply of 0.3L min was used. -1 Hydrogen and 0.5L min -1Air was used to provide a back pressure of 2 Bar, the test temperature was 180°C, and the carbon paper used was 39BB type carbon paper manufactured by SGL Carbon. Figure 1 The polarization curve and power density curve of the membrane electrode prepared in this embodiment as a single cell are shown. Figure 1 It is known that the peak power density of the membrane electrode with an ionomer layer used in high-temperature proton exchange membrane fuel cells is 702 mW / cm². -2 The current density at 0.6V is 401 mA cm⁻¹. -2 .

[0047] Example 3

[0048] This embodiment proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, and its preparation steps are as follows:

[0049] 1) 0.85mg pt / cm 2 Pt / C and 20 wt.% polytetrafluoroethylene were mixed and ultrasonically dispersed for 90 min to obtain a mixed slurry.

[0050] 2) The mixed slurry was ultrasonically sprayed onto carbon paper, dried at 60°C for 1 hour, and then sintered at 350°C for 2 hours.

[0051] 3) Polybenzimidazole / dimethyl sulfoxide solutions were mixed at a mass ratio of 1:200 and dissolved by heating at 180°C to obtain an organic solution.

[0052] 4) The organic solvent is evenly sprayed onto the sintered carbon paper, with a polybenzimidazole loading of 0.45 mg / cm³. 2 Dry at 120℃ for 1 hour.

[0053] 5) Take a 25-micron thick polybenzimidazole film and immerse it in phosphoric acid at 120°C for 3 hours, then wipe off the excess phosphoric acid.

[0054] 6) Press the carbon paper obtained in 4) and the polybenzimidazole film obtained in 5) together to obtain a membrane electrode.

[0055] In single-cell testing, a supply of 0.3L min was used. -1 Hydrogen and 0.5L min -1 Air was used to provide a back pressure of 2 Bar, the test temperature was 180°C, and the carbon paper used was 39BB type carbon paper manufactured by SGL Carbon. Figure 1 The polarization curve and power density curve of the membrane electrode prepared in this embodiment as a single cell are shown. Figure 1 It is known that the peak power density of the membrane electrode with an ionomer layer used in high-temperature proton exchange membrane fuel cells is 626 mW / cm². -2 The current density at 0.6V is 390 mA cm⁻¹.-2 .

[0056] Example 4

[0057] This embodiment proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, and its preparation steps are as follows:

[0058] 1) 0.85mg pt / cm 2 Pt / C and 20 wt.% polytetrafluoroethylene were mixed and ultrasonically dispersed for 90 min to obtain a mixed slurry.

[0059] 2) The mixed slurry was ultrasonically sprayed onto carbon paper, dried at 60°C for 1 hour, and then sintered at 350°C for 2 hours.

[0060] 3) Polybenzimidazole / dimethyl sulfoxide solutions were mixed at a mass ratio of 1:200 and dissolved by heating at 180°C to obtain an organic solution.

[0061] 4) The organic solvent is evenly sprayed onto the sintered carbon paper, with a polybenzimidazole loading of 0.3 mg / cm³. 2 Dry at 120℃ for 1 hour.

[0062] 5) Take a 20-micron thick polybenzimidazole film and immerse it in phosphoric acid at 120°C for 3 hours, then wipe off the excess phosphoric acid.

[0063] 6) Press the carbon paper obtained in 4) and the polybenzimidazole film obtained in 5) together to obtain a membrane electrode.

[0064] Supply 0.3L min -1 Hydrogen and 0.5L min -1 Air was used to provide a back pressure of 2 Bar, the test temperature was 180°C, and the carbon paper used was 39BB type carbon paper manufactured by SGL Carbon. Figure 2 The polarization curve and power density curve of the membrane electrode prepared in this embodiment as a single cell are shown. Figure 2 It is known that the peak power density of the membrane electrode with an ionomer layer used in high-temperature proton exchange membrane fuel cells is 713 mW / cm². -2 The current density at 0.6V is 475 mA cm⁻¹. -2 .

[0065] Example 5

[0066] This embodiment proposes a membrane electrode for high-temperature proton exchange membrane fuel cells, and its preparation steps are as follows:

[0067] 1) 0.85mg pt / cm 2 Pt / C and 20 wt.% polytetrafluoroethylene were mixed and ultrasonically dispersed for 90 min to obtain a mixed slurry.

[0068] 2) The mixed slurry was ultrasonically sprayed onto carbon paper, dried at 60°C for 1 hour, and then sintered at 350°C for 2 hours.

[0069] 3) Polybenzimidazole / dimethyl sulfoxide solutions were mixed at a mass ratio of 1:200 and dissolved by heating at 180°C to obtain an organic solution.

[0070] 4) The organic solvent is evenly sprayed onto the sintered carbon paper, with a polybenzimidazole loading of 0.3 mg / cm³. 2 Dry at 120℃ for 1 hour.

[0071] 5) Take a 15-micron thick polybenzimidazole film and immerse it in phosphoric acid at 120°C for 3 hours, then wipe off the excess phosphoric acid.

[0072] 6) Press the carbon paper obtained in 4) and the polybenzimidazole film obtained in 5) together to obtain a membrane electrode.

[0073] In single-cell testing, a supply of 0.3L min was used. -1 Hydrogen and 0.5L min -1 Air was used to provide a back pressure of 2 Bar, the test temperature was 180°C, and the carbon paper used was 39BB type carbon paper manufactured by SGL Carbon. Figure 2 The polarization curve and power density curve of the membrane electrode prepared in this embodiment as a single cell are shown. Figure 2 It is known that the peak power density of the membrane electrode with an ionomer layer used in high-temperature proton exchange membrane fuel cells is 721 mW / cm². -2 The current density at 0.6V is 460mA / cm². -2 .

[0074] The above description of the embodiments is provided to facilitate understanding and use of the invention by those skilled in the art. It will be apparent to those skilled in the art that various modifications can be easily made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A membrane electrode assembly for a high-temperature proton exchange membrane fuel cell, characterized in that, The membrane electrode has an ionomer layer, which is a multilayer structure consisting of a conductive substrate, a catalyst layer, an ionomer layer, a high-temperature proton exchange membrane, an ionomer layer, a catalyst layer, and a conductive substrate in sequence. The ionomer layer is composed of one or more polymers of polybenzimidazole or its derivatives as the main component, and is doped with one or more conductive agents of carbon powder or its derivatives to form a composite material. The ionomer layer is formed on the surface of the catalyst layer. The loading of one or more polymers of polybenzimidazole or its derivatives in the ionomer layer is 0.1~0.5 mg / cm³. -2 ; The conductive substrate is carbon paper or carbon cloth with a gas diffusion layer and / or a microporous layer; The catalyst layer is a composite material formed by a Pt-based catalyst and a hydrophobic binder through a deposition process, wherein the mass ratio of the hydrophobic binder to the Pt-based catalyst is 1:5-20, and the hydrophobic binder is selected from polytetrafluoroethylene and / or polyvinylidene fluoride. The high-temperature proton exchange membrane is one or more polymers of acid-treated polybenzimidazole or its derivatives.

2. The method for preparing the membrane electrode for a high-temperature proton exchange membrane fuel cell according to claim 1, characterized in that, Includes the following steps: (1) Using water, ethanol or isopropanol in any proportion as a dispersant, add Pt-based catalyst powder as an active ingredient, and a suspension of polytetrafluoroethylene and / or polyvinylidene fluoride as a hydrophobic binder. The resulting slurry is sonicated for 5-120 min to obtain a catalyst slurry. (2) The catalyst slurry obtained in step (1) is coated onto a conductive substrate by air spraying, electrostatic spraying, ultrasonic spraying, scraping, screen printing or rolling, and dried at 60-80℃ for 0.5-4h to obtain a conductive substrate with a catalyst layer. (3) The conductive substrate with the catalyst layer obtained in step (2) is placed at 200-400℃ for 1-5h and then taken out to obtain a gas diffusion electrode; (4) Using one or more of dimethylformamide, dimethylacetamide, dimethyl sulfoxide or N-methyl-2-pyrrolidone in any proportion as a dispersant, add one or more polymers of polybenzimidazole or its derivatives, with a solid-to-liquid mass ratio of 1:20~500, and heat the mixed solution at 100-250°C until the polymer is completely dissolved to obtain an organic solution; (5) The organic solution obtained in step (4) is coated onto the surface of the catalyst layer by air spraying, electrostatic spraying, ultrasonic spraying, scraping, screen printing or rolling, and dried at 80-160℃ for 0.5-3h to obtain the ionomer layer; (6) A high-temperature proton exchange membrane is obtained by immersing one or more polymer films of polybenzimidazole or its derivatives with a thickness of 10-35 micrometers in a mixture of one or more of phosphoric acid, hydrochloric acid or sulfuric acid in any proportion at 80-120°C for 0.5-10h. (7) The gas diffusion electrode, the high-temperature proton exchange membrane and the gas diffusion electrode are placed in sequence to form a sandwich structure, and hot-pressed for 1-8 minutes at 100-150℃ and 0.1-0.4MPa to obtain the membrane electrode.

3. The application of the membrane electrode assembly of claim 1 for a high-temperature proton exchange membrane fuel cell in a high-temperature proton exchange membrane fuel cell.

Images