Ultra-thin membrane electrode assembly proton exchange membrane fuel cell and method of making same

Abstract

The application discloses an ultra-thin membrane electrode proton exchange membrane fuel cell and a preparation method thereof. The structure of the ultra-thin membrane electrode cell is that porous media flow fields of cathode and anode are arranged on two sides of the ultra-thin membrane electrode, the proton exchange membrane is covered with cathode and anode catalytic layers on the upper and lower sides respectively to form a catalytic layer coated proton exchange membrane assembly, and the cathode and anode catalytic layers are respectively covered with an ultra-thin porous carbon fiber layer with a thickness of less than 15 micrometers, so that the ultra-thin membrane electrode cell is finally formed, and the total thickness of the electrode is less than 50 micrometers. The preparation method is that a 14% dimethylacetamide solution is prepared, electrostatic spinning is carried out, then sintering and solidification are carried out, and high-temperature sintering is carried out. The application can reduce the thickness of the membrane electrode by about 90%, reduce the thickness of the single cell by about 41%, improve the volume power density of the fuel cell by more than 100%, and effectively reduce the concentration difference loss of the fuel cell due to the shortened reaction gas transmission path, so that the absolute power density of the single cell is improved by about 47%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemical fuel cells, and particularly relates to an ultra-thin membrane electrode proton exchange membrane fuel cell and a preparation method thereof. BACKGROUND

[0002] Proton exchange membrane fuel cell (PEMFC) is a green and pollution-free energy conversion device for converting hydrogen energy into electric energy. The advantage of the device lies in high energy conversion efficiency and no pollution. China is developing clean energy, and hydrogen energy is considered as a clean energy in the future. Under the promotion of the government and major automobile enterprises, proton exchange membrane fuel cells are developing rapidly. Proton exchange membrane fuel cells applied to automobile engines have very high requirements for volume power density. Major automobile enterprises at home and abroad aim to make the volume power density of fuel cells larger. There are two routes to achieve this goal: one is to make the volume of fuel cells smaller; and the other is to make the power density of fuel cells larger. For fuel cells, the components with a large volume ratio are membrane electrodes and bipolar plates, and the proportion of the gas diffusion layer in the membrane electrode is more than 90%. So far, the substrate of the gas diffusion layer used in the fuel cell is still carbon paper, and the bottleneck problem of the carbon paper manufacturing process technology makes it impossible to further reduce the thickness, which leads to the fact that the membrane electrode of the fuel cell has always maintained a thickness of 250 μm or even 300 μm or more. The present application can solve this problem. SUMMARY

[0003] The purpose of the present application is to provide an ultra-thin membrane electrode proton exchange membrane fuel cell and a preparation method thereof, to shorten the transmission of reaction gas to the catalytic layer channel and reduce the thickness of the cell, so as to improve the volume power density of the fuel cell.

[0004] The technical principles and structural schemes of the present application are described as follows:

[0005] The structure of the ultra-thin membrane electrode proton exchange membrane fuel cell is that cathode porous medium flow fields and anode porous medium flow fields are arranged on both sides of the ultra-thin membrane electrode. The composition structure of the ultra-thin membrane electrode is that a proton exchange membrane is used as a center layer, a cathode catalytic layer and an anode catalytic layer are respectively covered on the upper and lower sides of the center layer to form a proton exchange membrane assembly (CCM) coated with a catalytic layer, and an ultra-thin porous carbon fiber layer with a thickness of 15 μm or less is respectively covered on the cathode and anode catalytic layers. The ultra-thin membrane electrode together with the cathode and anode porous medium flow fields finally forms an ultra-thin membrane electrode of the proton exchange membrane fuel cell, and the total thickness of the ultra-thin membrane electrode is less than 50 μm.

[0006] The preparation method of the ultra-thin membrane electrode proton exchange membrane fuel cell is described as follows:

[0007] (1) Prepare a solution of dimethylacetamide with a mass fraction of 14%, place the solution in an electrospinning instrument, and spin at a voltage of 10 kV to 18 kV and a pushing speed of 1 mL per hour, and set the rotating speed of the drum to 20 to 200 revolutions per minute.

[0008] (2) After the spinning with a total time length of 30 min, place the sample in a muffle furnace to sinter the sample at a temperature of 240 to 260 °C for 2 hours.

[0009] (3) After the sintering, place the sample in a tube furnace to sinter at a temperature of 1000 to 1400 °C for 1 hour, and keep the heating rate below 1 °C per minute, and the width of the receiver in the electrospinning process is 10 cm, and the thickness of the ultra-thin porous carbon fiber layer is below 15 μm.

[0010] The ultra-thin membrane electrode of the proton exchange membrane fuel cell is prepared by using an electrospinning method to prepare an ultra-thin porous carbon fiber film, combining the prepared CCM to complete the ultra-thin membrane electrode, and assembling the ultra-thin membrane electrode into a proton exchange membrane fuel cell or a stack by combining a metal foam or a carbon foam porous flow field.

[0011] The features and beneficial effects of the present application are that the ultra-thin membrane electrode can reduce the thickness of the proton exchange membrane fuel cell membrane electrode by about 90%, and effectively improve the volume power density of the single cell by more than 100%. In addition, since the path of the reaction gas to the catalyst layer is shortened, the mass transfer loss of the PEMFC is reduced, and the absolute performance is greatly improved by about 47%. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a schematic diagram of the ultra-thin membrane electrode proton exchange membrane fuel cell single cell.

[0013] Figure 2 It is a schematic diagram of the ultra-thin membrane electrode.

[0014] Figure 3 It is a comparison diagram of the battery performance effect of the embodiment of the present application.

[0015] Figure 4 It is a comparison diagram of the volume power density of the battery of the embodiment of the present application. DETAILED DESCRIPTION

[0016] The technical solutions of the present application will be described in detail below in combination with the drawings and specific embodiments. It should be noted that the present embodiment is descriptive rather than limiting, and does not limit the protection scope of the present application.

[0017] The ultra-thin membrane electrode proton exchange membrane fuel cell comprises: a cathode porous medium flow field 1 and an anode porous medium flow field 3 arranged on both sides of the ultra-thin membrane electrode 2 (such as Figure 1The ultrathin film electrode is composed of a proton exchange membrane 2-3 as the central layer, with a cathode catalyst layer 2-2 and an anode catalyst layer 2-4 covering the upper and lower sides of the central layer, respectively, forming a CCM assembly; an ultrathin porous carbon fiber layer 2-1 with a thickness of less than 15 μm is used to cover the cathode and anode catalyst layers (e.g., ...). Figure 2 The ultrathin film electrode, together with the porous media flow fields of the cathode and anode, ultimately forms the ultrathin film electrode for the proton exchange membrane fuel cell, with a total thickness of less than 50 μm.

[0018] The porous media flow field is a graphene-coated nickel metal foam (or carbon foam). The graphene layer is grown on the surface of the nickel metal foam by chemical vapor deposition (CVD). The porosity of the nickel metal foam before compression is more than 90%, the thickness before compression is 1.2 mm to 2 mm, the thickness after compression is 250 μm to 350 μm, and the pore size characteristics are 80 ppi to 110 ppi.

[0019] The specific steps of the preparation method for ultrathin film electrode proton exchange membrane fuel cells are as follows:

[0020] (1) Prepare a 14% dimethylacetamide solution, place the solution in an electrospinning apparatus, use a voltage of 10kV to 18kV and a feed rate of 1mL per hour for spinning, and set the rotation speed of the roller to 20 to 200 revolutions per minute.

[0021] (2) After the spinning process, which lasts for a total of 30 minutes, the sample is placed in a muffle furnace and sintered at a temperature of 240°C to 260°C for 2 hours to solidify the sample.

[0022] (3) After curing, the sample is placed in a tube furnace and sintered at a temperature of 1000°C to 1400°C for 1 hour. The heating rate is kept below 1°C per minute. The receiver width during the electrospinning process is 10cm. The thickness of the ultrathin porous carbon fiber layer is below 15μm.

[0023] The ultrathin film electrode of a proton exchange membrane fuel cell is composed of a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, an ultrathin porous carbon fiber layer for the cathode, and an ultrathin porous carbon fiber layer for the anode.

[0024] The ultrathin film electrode of the proton exchange membrane fuel cell has a cathode catalyst layer and an anode catalyst layer on both sides of the proton exchange membrane, and an ultrathin porous carbon fiber layer for both the anode and cathode on the outermost side.

[0025] As an example, a 14% dimethylacetamide solution was placed in an electrospinning apparatus, and spinning was performed using a voltage of 14kV and a feed rate of 1mL per hour, with the roller speed set to 50 revolutions per minute.

[0026] The spinning process lasted 30 minutes. The sample was then placed in a muffle furnace and sintered at 245°C for 2 hours. The purpose of this step was to solidify the sample.

[0027] After curing, the sample is placed in a tube furnace and sintered at 1000℃ for 1 hour, with the heating rate maintained at 1℃ per minute. This step is for carbonizing the sample. After the above steps are completed, an ultrathin porous carbon fiber layer is obtained.

[0028] In ultrathin-film electrode proton exchange membrane fuel cells, traditional groove-ridge structures are unsuitable due to the extremely thin nature of the ultrathin electrodes, which prevents them from providing support under the grooves, and also due to diffusion problems under the ridges. Therefore, porous media flow fields are required for ultrathin-film electrode proton exchange membrane fuel cells.

[0029] The porous medium used in this embodiment is a graphene-coated nickel foam with a porosity of 98% and a thickness of 1.6 mm before compression, and a thickness of 0.3 mm after compression, with a pore size characteristic of 110 PPi. The graphene coating method is chemical vapor deposition.

[0030] The catalyst layer consists of a carbon-supported platinum catalyst and an electrolyte (nafion), with a cathode catalyst loading of 0.4 mg / cm³. -2 The anolyte catalyst loading is 0.1 mg cm⁻¹. -2 The proton exchange membrane has a thickness of 15 μm.

[0031] Figure 3 A comparison of polarization curves between ultrathin-film electrode proton exchange membrane fuel cells and conventional proton exchange membrane fuel cells is presented. The figures show that, under identical operating conditions and other external factors, the highest power density of the ultrathin-film electrode proton exchange membrane fuel cell exceeds 1.8 W / cm². -2 The limiting current density reaches 5.4 A cm⁻¹. -2 The highest power density of conventional proton exchange membrane fuel cells is only 1.2 W / cm². -2 The limiting current density is only 3.2 A cm⁻¹. -2 The output power of the ultrathin film electrode fuel cell is nearly 50% higher than that of a conventional membrane electrode proton exchange membrane fuel cell. This indicates that the output performance of the ultrathin film electrode is significantly superior to that of the conventional membrane electrode fuel cell, mainly due to the shorter gas and electron transport paths of the ultrathin film electrode, which gives the fuel cell superior oxygen transport and electron conduction capabilities.

[0032] Appendix Figure 4The polarization curves and power output comparisons of two batteries are presented, namely a conventional membrane electrode proton exchange membrane fuel cell and an ultrathin membrane electrode proton exchange membrane fuel cell. As can be seen from the figures, the volumetric power density of the ultrathin membrane electrode proton exchange membrane fuel cell proposed in this invention can reach 20 kW L. -1 In contrast, the volumetric power density of conventional membrane electrode proton exchange membrane fuel cells is only 9 kW L. -1 This indicates that, within the same volume, an ultrathin-film electrode proton exchange membrane fuel cell can output twice the power of a conventional membrane electrode fuel cell, or in other words, an ultrathin-film electrode fuel cell requires only half the volume of a conventional battery to output the same power. This is mainly due to the reduction in volume and the increase in power density. Therefore, this type of ultrathin-film electrode proton exchange membrane fuel cell is more suitable for space-constrained applications such as passenger vehicles, releasing greater power within a limited space.

Claims

1. An ultrathin film electrode proton exchange membrane fuel cell, characterized in that: The ultrathin film electrode (2) is provided with a cathode porous medium flow field (1) and an anode porous medium flow field (3) on both sides. The composition structure of the ultrathin film electrode is as follows: a proton exchange membrane (2-3) is used as the central layer, and a cathode catalyst layer (2-2) and an anode catalyst layer (2-4) are respectively covered on the upper and lower sides of the central layer to form a proton exchange membrane assembly coated with catalyst layers. An ultrathin porous carbon fiber layer (2-1) with a thickness of less than 10 μm is covered on the cathode and anode catalyst layers respectively. The ultrathin film electrode together with the cathode and anode porous medium flow fields finally forms the ultrathin film electrode of the proton exchange membrane fuel cell. The total thickness of the ultrathin film electrode is less than 50 μm.

2. The ultrathin film electrode proton exchange membrane fuel cell according to claim 1, characterized in that: The porous medium flow field is a graphene-coated nickel metal foam. The graphene layer is grown on the surface of the nickel metal foam by chemical vapor deposition. The porosity of the nickel metal foam before compression is more than 90%, the thickness before compression is 1.2 mm to 2 mm, the thickness after compression is 250 μm to 350 μm, and the pore size characteristics are 80 ppi to 110 ppi.

3. A method for preparing an ultrathin film electrode proton exchange membrane fuel cell according to claim 1 or 2, characterized in that, The specific steps are as follows: (1) Prepare a 14% dimethylacetamide solution, place the solution in an electrospinning apparatus, use a voltage of 10kV to 18kV and a feeding speed of 1mL per hour for spinning, and set the rotation speed of the roller to 20 to 200 revolutions per minute. (2) After spinning for a total of 30 minutes, the sample was placed in a muffle furnace and sintered at 240°C to 260°C for 2 hours to solidify the sample. (3) After curing, the sample is placed in a tube furnace and sintered at a temperature of 1000°C to 1400°C for 1 hour. The heating rate is kept below 1°C per minute. The receiver width during the electrospinning process is 10cm. The thickness of the ultrathin porous carbon fiber layer is below 10μm.

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