WO2023151016A1

WO2023151016A1 - Proton exchange membrane fuel cell, membrane electrode assembly and preparation method therefor

Info

Publication number: WO2023151016A1
Application number: PCT/CN2022/075997
Authority: WO
Inventors: 张旭; 张敬君; 谢旭
Original assignee: 罗伯特·博世有限公司; 张旭; 张敬君; 谢旭
Priority date: 2022-02-11
Filing date: 2022-02-11
Publication date: 2023-08-17
Also published as: CN118743071A; DE112022005120T5

Abstract

The present invention provides a membrane electrode assembly of a proton exchange membrane fuel cell. The membrane electrode assembly comprises: an anode catalyst layer, a proton exchange membrane and a cathode catalyst layer, wherein the proton exchange membrane is a mica membrane, which has been pretreated by means of proton exchange, and the anode catalyst layer and the cathode catalyst layer each independently comprise a catalyst powder and a mica powder. The present invention also provides a preparation method for the membrane electrode assembly, and a proton exchange membrane fuel cell comprising the membrane electrode assembly.

Description

Proton exchange membrane fuel cell, membrane electrode assembly and preparation method thereof

technical field

The invention relates to a membrane electrode assembly of a proton exchange membrane fuel cell. The invention also provides a preparation method of the membrane electrode assembly and a proton exchange membrane fuel cell comprising the membrane electrode assembly.

Background technique

Due to the use of solid polymer membranes as electrolytes, proton exchange membrane fuel cells have many advantages, such as low-temperature rapid start-up, no electrolyte loss, non-corrosion, long life, high specific energy, high specific power, simple design and convenient manufacture, etc. . Therefore, proton exchange membrane fuel cells have received extensive attention in recent years.

As shown in Figure 1, a proton exchange membrane fuel cell unit usually includes an anode plate 23, an anode gas diffusion layer 22, a membrane electrode assembly (including an anode catalyst layer 21, a proton exchange membrane 10 and a cathode catalyst layer 31), a cathode gas Diffusion layer 32 and cathode plate 33.

The hydrogen gas is input from the anode plate 23, and the hydrogen gas passes through the anode gas diffusion layer 22 to reach the anode catalyst layer 21, where the reaction of the following formula ① occurs and is decomposed into protons and electrons. The protons pass through the proton exchange membrane to the cathode catalyst layer 31 . The electrons pass through the anode plate 23 , from the peripheral circuit connected with the external load 40 to the cathode plate 33 , and then pass through the cathode gas diffusion layer 32 to the cathode catalyst layer 31 . Oxygen is supplied from the cathode plate 33 and passes through the cathode gas diffusion layer 32 to the cathode catalyst layer 31 . At the cathode catalyst layer 31, oxygen, protons, and electrons react according to the following formula ② to generate water. Water exits the cathode plate 33 along with excess oxygen.

At the anode H ₂ →2H ⁺ +2e ^- ①

at the cathode

overall

The membrane electrode assembly, especially the proton exchange membrane, as the core component of the proton exchange membrane fuel cell, provides a channel for proton transfer, and at the same time acts as a diaphragm to isolate the reaction gas of the cathode and the anode. Therefore, membrane electrode assemblies, especially proton exchange membranes, must have good electrical conductivity, good thermal and chemical stability, low gas permeability, and sufficient mechanical strength.

The most commonly used proton exchange membrane is the Nafion electrolyte membrane produced by DuPont of the United States. The Nafion membrane is a perfluorosulfonic acid membrane that has absorbed moisture. The perfluorosulfonic acid membrane is not resistant to high temperature and must be operated at a temperature lower than 100°C, otherwise significant thermal decomposition will occur, and dehydration of the perfluorosulfonic acid membrane will occur, resulting in a decrease in battery performance. However, PEMFC generates heat with the reaction, and the temperature at the downstream outlet is often much higher than the control operating temperature. In addition, in order to further improve the efficiency and heat removal of fuel cell systems, high temperature operation has also become a development trend. Therefore, the above defects of perfluorosulfonic acid membranes seriously hinder the use of cell stacks with large active areas and the continuous improvement of the performance of proton exchange membrane fuel cells.

Therefore, need to improve the membrane electrode assembly of proton exchange membrane fuel cell, especially improve the proton conductivity, high temperature resistance and mechanical strength of proton exchange membrane, and then improve the cell performance (for example, electrochemical performance and discharge of proton exchange membrane fuel cell) of proton exchange membrane fuel cell stability).

Contents of the invention

To this end, on the one hand, the present disclosure provides a membrane electrode assembly for a proton exchange membrane fuel cell, which includes: an anode catalyst layer, a proton exchange membrane, and a cathode catalyst layer, wherein the proton exchange membrane is A treated mica film, and the anode catalyst layer and the cathode catalyst layer each independently contain catalyst powder and mica powder.

The present invention adopts mica, which is rich in reserves in the earth's crust and is cheap, as the material of the proton exchange membrane, reduces the cost of the proton exchange membrane fuel cell, and extends the service temperature of the proton exchange membrane fuel cell from below 100°C to about 200°C. It even extends to about 500°C. The mica membrane, especially the mica membrane pretreated by proton exchange to activate the proton exchange capacity, has a proton conductivity more than twice the current commercial requirement, greatly improving the energy conversion efficiency of the proton exchange membrane fuel cell. The membrane electrode assembly according to the present invention, especially the proton exchange membrane, has higher fuel efficiency, and the resulting fuel cell stack achieves good heat management and water management. Also, the proton exchange membrane according to the present invention has low hydrogen gas permeability, which can reduce performance loss due to mixed potential. In addition, by employing the mica membrane, the mechanical strength (for example, compressive strength and flexural modulus) of the proton exchange membrane according to the present invention is superior to that of polymer-based membranes, such as perfluorosulfonic acid membranes, contributing to better Mechanical durability.

Moreover, the present invention uses mica powder in the catalyst ink, thereby improving the proton conductivity of the anode catalyst layer and the cathode catalyst layer, and further improving the battery performance of the entire proton exchange membrane fuel cell.

In another aspect, the invention provides a proton exchange membrane fuel cell comprising an anode plate, an anode gas diffusion layer, a membrane electrode assembly according to the invention, a cathode gas diffusion layer and a cathode plate.

In another aspect, the present disclosure provides a method for preparing a membrane electrode assembly, which includes the following steps:

a) providing a mica film,

b) carrying out proton exchange pretreatment to the mica membrane,

c) applying catalyst ink comprising mica powder and catalyst powder to both sides of the mica membrane pretreated by proton exchange, thereby obtaining a membrane electrode assembly.

The main body of mica is a sheet composed of hexagonal aluminosilicate units, and there are a lot of potassium ions between the sheets. In the process of proton exchange pretreatment, by replacing the larger potassium ions between mica layers with extremely small protons (one hundred thousandth of the volume of potassium ions), a tubular channel is built for protons in the proton exchange membrane material. These tubular channels are filled with a large number of hydroxyl groups, and protons can hop along the hydroxyl chains. Therefore, the mica membrane pretreated by proton exchange has excellent proton conductivity.

Various other features, aspects and advantages of the present invention will become more apparent with reference to the following drawings. These drawings are not drawn to scale, are intended to schematically explain various structures and positional relationships, and should not be construed as limiting. In the drawings, like reference numerals generally refer to like parts throughout the different views.

Description of drawings

Fig. 1 is a schematic structural diagram of a conventional proton exchange membrane fuel cell.

Detailed ways

Unless defined otherwise, 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 belongs. If there is any inconsistency, the definitions provided in this application shall prevail.

Unless otherwise indicated, the numerical ranges recited herein are intended to include the endpoints of the range, and all values and all subranges within that range.

The materials, contents, methods, equipment, figures and examples herein are illustrative and should not be construed as limiting unless otherwise specified.

As used herein, "comprising", "including" and "having" all mean that other components or other steps that do not affect the final effect may be included. These terms encompass the meanings of "consisting of" and "consisting essentially of". Products and methods according to the present invention may comprise or comprise the essential technical features described in this disclosure, as well as additional and/or optional components, ingredients, steps or other limiting features described herein; The essential technical features described, as well as additional and/or optional components, ingredients, steps or other restrictive features described herein; or essentially consist of the essential technical features described in this disclosure, and additional and/or Optionally present components, ingredients, steps or other limiting features described herein.

All materials and reagents used in this disclosure are commercially available unless expressly stated otherwise.

Unless otherwise indicated or clearly contradicted, operations performed herein can be performed at room temperature and pressure.

The method steps in the present disclosure can be performed in any suitable order unless otherwise indicated or otherwise clearly contradicted.

Examples of the present disclosure will be described in detail below.

In some examples, the catalyst powders in the cathode catalyst layer and the anode catalyst layer are the same or different, and each is independently selected from one or more of carbon-supported metal catalysts and non-noble metal catalysts.

There is no particular limitation on the carbon-supported metal catalysts, and those commonly used in proton exchange membrane fuel cells are applicable to the present invention. In some examples, the carbon-supported metal catalyst is selected from one or more of carbon-supported platinum (Pt/C) catalysts and carbon-supported platinum alloy (Pt-alloy/C) catalysts.

In some examples, the non-noble metal in the non-noble metal catalyst is selected from transition metals, such as one or more selected from Group IB to VIIB elements, Group VIII elements, lanthanides, and actinides.

In some examples, the platinum alloy in the carbon-supported platinum alloy catalyst is an alloy of platinum and one or more non-platinum elements. Non-platinum elements may be selected from non-platinum metals, non-metals, or metalloid elements. In some examples, the non-platinum metal is selected from transition metals, such as one or more of Group IB to VIIB elements, Group VIII elements, lanthanides, and actinides. Non-platinum metals are selected from non-precious metals for cost considerations. Platinum alloys include, but are not limited to, alloys of platinum with one or more of the following elements: palladium, rhodium, yttrium, ruthenium, cobalt, osmium, copper, nickel, iron, and carbon.

In some examples, the catalyst powder in the cathode catalyst layer and the anode catalyst layer are the same.

In some examples, the catalyst powder in both the cathode catalyst layer and the anode catalyst layer comprises or consists of platinum on carbon (Pt/C). Commercially available platinum on carbon (Pt/C) can be used in the present invention.

In some examples, the mass ratio of metal to carbon in the anode catalyst layer and the carbon-supported metal catalyst in the cathode catalyst layer each independently ranges from about 0.4:1 to about 0.6:1. For example, in a platinum-on-carbon (Pt/C) catalyst, the mass ratio of platinum to carbon is about 0.4:1 to about 0.6:1.

In some examples, in the carbon-supported metal catalysts in the anode catalyst layer and the cathode catalyst layer, the mass ratio of metal to carbon is the same or different, preferably the same.

In some examples, in the carbon-supported metal catalyst powder of the cathode catalyst layer and the anode catalyst layer, the carbon powder is each independently an agglomerate of about 10 to about 500 nanometers, and the particle size of the metal powder is each independently about 2 to 500 nanometers. about 8 nm. The metal powder is anchored to the carbon powder, and the carbon-supported metal catalyst powder as a whole has a particle size each independently of about 10 to about 500 nanometers.

In some examples, both the cathode catalyst layer and the anode catalyst layer comprise carbon-supported platinum (Pt/C) powder having a particle size of about 10 to about 500 nanometers, wherein the carbon powder is an aggregate structure of about 10 to about 500 nanometers , the particle size of the platinum powder is from about 2 to about 8 nanometers.

Commercially available mica films can be used in the present invention. In some instances, mica films can be obtained by pressing mica powder into flakes and pre-treating them with an electrolyte. Conventional polymer-based proton exchange membranes have almost no flexural strength. On the contrary, the mica membrane used in the present invention has good compressive strength and flexural modulus, which greatly improves the stability of proton exchange membranes and membrane electrode assemblies. Mechanical behavior.

In some examples, the mica film has a thickness of about 5 to about 20 microns.

In some examples, the mica film has a proton conductivity of about 0.05 S·cm ⁻¹ at about 150° C. Generally, the proton conductivity of the mica film increases with increasing temperature.

In some examples, the hydrogen permeability of the mica film is less than 0.014 mL·min ^-1 ·cm ^-2 , preferably about 0.01 mL·min ^-1 ·cm ^-2 . The hydrogen permeability is measured according to the DOE test standard of the US Department of Energy, and the measurement conditions are 80° C., 1 atmosphere pressure, and a saturated hydrogen pressure difference. The hydrogen permeability of conventional polymer-based proton exchange membranes is much higher than 0.014 mL·min ⁻¹ ·cm ⁻² .

In some examples, the mica in the mica film is selected from one or more of muscovite, phlogopite, biotite, and lepidolite.

In some examples, the mica powder in the anode catalyst layer and the cathode catalyst layer are each independently selected from one or more of muscovite, phlogopite, biotite, and lepidolite.

In some examples, the mica powders in the anode catalyst layer and the cathode catalyst layer are the same or different, preferably the same.

In some examples, the mica powder in the anode catalyst layer and the cathode catalyst layer is the same or different from the mica in the mica film, preferably one of the mica powder in the anode catalyst layer and the cathode catalyst layer, Or both are the same as the mica in the mica film.

In some examples, the mica powder in the anode catalyst layer and the cathode catalyst layer each independently have a particle size of about 10 to about 500 nanometers.

In some examples, the particle diameters of the mica powder in the anode catalyst layer and the cathode catalyst layer are the same or different, preferably the same.

In some examples, both the anode catalyst layer and the cathode catalyst layer include catalyst powder with a size of 10-500 nm and mica powder with a size of 10-500 nm. When the particle size of the catalyst powder and the mica powder are similar, it is beneficial to form a uniform catalyst layer.

In some examples, the mass ratio of mica powder to catalyst powder in the anode catalyst layer and the cathode catalyst layer is each independently from about 0.4:1 to about 1:1.

In some examples, the mass ratio of mica powder to catalyst powder in the anode catalyst layer and the cathode catalyst layer is the same or different, preferably the same.

The anode gas diffusion layer is located between the anode catalyst layer and the anode plate, and the cathode gas diffusion layer is located between the cathode catalyst layer and the cathode plate, which are used to support the anode catalyst layer and the cathode catalyst layer respectively, and provide electron channels, gas channels and drainage channels.

In some examples, the anode gas diffusion layer and the cathode gas diffusion layer are carbon fiber based porous substrates.

In some examples, the anode gas diffusion layer and the cathode gas diffusion layer are independently selected from carbon fiber paper, carbon fiber woven fabric, carbon fiber nonwoven fabric and any combination thereof.

In some instances, the anode gas diffusion layer and the cathode gas diffusion layer are the same or different, preferably the same.

The cathode and anode plates are collectively referred to as bipolar plates. Bipolar plates are used to collect and conduct electric current, block and transport fuels (for example, hydrogen and oxygen), and conduct heat, among other things.

In some examples, the anode and cathode plates are independently made of graphite or metals such as stainless steel, titanium alloys, aluminum alloys, or nickel alloys, among others.

In some instances, the anode and cathode plates are the same or different, preferably the same.

a) providing a mica film,

b) carrying out proton exchange pretreatment to the mica membrane,

Activation of the proton exchange capacity can be achieved by performing step b) pretreatment of the proton exchange membrane on the mica membrane.

In some examples, in step b), the proton exchange pretreatment is performed by: soaking the mica film in an acid solution and heating; and

Optionally, after soaking the mica film in the acid solution and heating, the mica film is soaked in water and heated.

The acid in the acid solution is not particularly limited, and any protonic acid that can release hydrogen ions can be used in the present invention.

In some examples, the acid can be sulfuric acid.

In some examples, the acid solution is an aqueous solution of a protic acid, such as an aqueous solution of sulfuric acid.

There is no particular limitation on the heating time of the mica film soaked in the acid solution or water, for example, the heating time of the mica film soaked in the acid solution or water can be independently from about 10 minutes to about 1 hour, for example, about 10 minutes, About 20 minutes, about 30 minutes, about 40 minutes, about 50 minutes, or about 1 hour.

In some examples, proton exchange pretreatment was achieved by boiling in 1M aqueous sulfuric acid for half an hour, followed by boiling in deionized water for half an hour.

In some examples, step c) further includes step c-1) grinding mica into powder.

In some examples, step c) further includes step c-2) mixing mica powder, catalyst powder, dispersion solvent and water to obtain catalyst ink.

In some examples, the preparation method of membrane electrode assembly comprises the following steps:

a) providing a mica film,

b) subjecting said mica membrane to a proton exchange pretreatment, and

c) applying the catalyst ink comprising mica powder and catalyst powder to both sides of the mica membrane pretreated by proton exchange, thereby obtaining a membrane electrode assembly, wherein step c) comprises the following steps:

c-1) grinding mica into powder, and/or

c-2) Mix mica powder, catalyst powder, dispersion solvent and water to obtain a catalyst ink.

In some examples, the catalyst inks used for the anode catalyst layer and the cathode catalyst layer are the same or different, preferably the same.

In some examples, the water is deionized water.

In some examples, the dispersing solvent is or alcohols. The alcohol is preferably a water-miscible alcohol, such as ethylene glycol or isopropanol.

In some examples, in the catalyst ink used for the anode catalyst layer and the cathode catalyst layer, the mass ratio of mica powder to catalyst powder is about 0.4:1 to about 1:1. The type of dispersing solvent and the ratio of it to water can be selected according to the requirements of different coating methods on the viscosity of the catalyst ink.

In some instances, the catalyst ink can be directly coated on the mica film, which greatly simplifies the coating process and reduces the coating cost. Alternatively, catalyst inks can also be applied by the decal transfer method. For example, the catalyst ink is first coated on an inert ionotropic membrane and then transferred to a mica membrane.

The above-mentioned various limitations on the membrane electrode assembly are applicable to the preparation method of the membrane electrode assembly.

The proton exchange membrane fuel cell according to the present invention can be used in electric vehicles (such as automobiles), regional power stations and portable equipment.

Claims

A membrane electrode assembly for a proton exchange membrane fuel cell, the membrane electrode assembly comprising: an anode catalyst layer, a proton exchange membrane and a cathode catalyst layer, wherein the proton exchange membrane is a mica membrane pretreated by proton exchange, and the anode The catalyst layer and the cathode catalyst layer each independently contain catalyst powder and mica powder.
The membrane electrode assembly according to claim 1, wherein the catalyst powder is selected from one or more of carbon-supported metal catalysts and non-noble metal catalysts;

The carbon-supported metal catalyst is preferably selected from one or more of carbon-supported platinum (Pt/C) catalysts and carbon-supported platinum alloy (Pt-alloy/C) catalysts.
The membrane electrode assembly according to claim 1 or 2, wherein the mica film has a thickness of about 5 to about 20 microns.
The membrane electrode assembly according to claims 1-3, wherein the mica in the mica film is selected from one or more of muscovite, phlogopite, biotite and lepidolite.
The membrane electrode assembly according to any one of claims 1-4, wherein the mica powders in the anode catalyst layer and the cathode catalyst layer are each independently selected from muscovite, phlogopite, biotite, lepidolite one or more of.
The membrane electrode assembly according to any one of claims 1-5, wherein the mass ratio of mica powder to catalyst powder in the anode catalyst layer and the cathode catalyst layer is each independently about 0.4:1- About 1:1.
A proton exchange membrane fuel cell comprising an anode plate, an anode gas diffusion layer, a membrane electrode assembly according to any one of claims 1-6, a cathode gas diffusion layer and a cathode plate.
A method for preparing a membrane electrode assembly, comprising the following steps:

a) providing a mica film,

b) subjecting said mica membrane to a proton exchange pretreatment, and

c) applying catalyst ink comprising mica powder and catalyst powder to both sides of the mica membrane pretreated by proton exchange, thereby obtaining a membrane electrode assembly.
The method according to claim 8, wherein, step c) also includes step c-1) grinding mica into powder, and/or step c-2) mixing mica powder, catalyst powder, dispersion solvent and water to obtain a catalyst ink.
A method according to claim 8 or 9, wherein the catalyst ink is applied by decal transfer.
The method according to any one of claims 8-10, wherein, in step b), the proton exchange pretreatment is carried out by: soaking the mica film in an acid solution and heating; and

Optionally, after soaking the mica film in the acid solution and heating, the mica film is soaked in water and heated.