KR102348550B1 - fuel cell for graphitized carbon nanofiber and method of manufacturing the same - Google Patents

Abstract

The present invention relates to an electrode for a fuel cell and a method for manufacturing the same, and more particularly, it includes an electrode support and a catalyst layer applied to the electrode support, wherein the catalyst layer includes graphitized carbon nanomaterials and a catalyst material .

Description

Electrode for a fuel cell comprising graphitized carbon nanofibers and a method for manufacturing the same

The present invention relates to an electrode for a fuel cell comprising graphitized carbon nanofibers and a method for manufacturing the same.

Hydrogen fuel cells, which are currently being studied, show promise in various industries due to their advantages such as high current density and low operating temperature. One of the problems to be improved for the commercialization and dissemination of hydrogen fuel cells is water management of electrodes.

In a hydrogen fuel cell, water generated from the cathode reaction and water injected through the humidified fuel gas are continuously introduced and discharged, so efficient water management at the electrode is essential. In electrodes where water management is not performed, a flooding phenomenon occurs in which water accumulates and clogs pores. This flooding phenomenon has an adverse effect of reducing performance in a high current density region and accelerating durability degradation due to carbon corrosion in the long term.

Various electrode manufacturing technologies have been proposed for efficient water management of hydrogen fuel cells. Among them, the technology for coating the surface of an electrode with a hydrophobic polymer such as polytetrafluoroethylene (PTFE) and polydimethylsiloxane (PDMS) and the technology for manufacturing the electrode using the same are mostly used. Therefore, even if the electrode is coated with a hydrophobic polymer on the surface, the water management effect may be weak in the pores inside the catalyst layer. In addition, since the hydrophobic polymer has a weak property in terms of electrical conductivity compared to other electrode components such as platinum and carbon, there is a possibility that performance may be deteriorated on the contrary. Therefore, when introducing the hydrophobic polymer, a coating method with a limited amount of use and at the same time a very uniform coating method is required.

In addition, in the case of fuel cell electrodes using graphitized carbon nanofibers, most carbon nanofibers were used as a gas diffusion layer or a catalyst carrier. When graphitized carbon nanofibers in the form of mats are used as the gas diffusion layer, the electrode water management effect cannot be maximized because the pores inside the catalyst layer are not affected.

In addition, when graphitized carbon nanofibers are used as a catalyst carrier, there are fewer oxygen functional groups or other defects on the fiber surface, so there are fewer sites on which the platinum catalyst can be supported, resulting in particle aggregation.

SUMMARY OF THE INVENTION The present invention aims to solve the above and other problems.

Another object of the present invention is to provide an electrode for a fuel cell including graphitized carbon nanofibers and a method for manufacturing the same.

Another object of the present invention is to improve high fuel delivery and durability of a fuel cell through efficient water management.

However, these problems are exemplary, and the scope of the present invention is not limited thereto.

According to one aspect of the present invention, there is provided an electrode for a fuel cell, comprising an electrode support and a catalyst layer applied to the electrode support, wherein the catalyst layer includes graphitized carbon nanomaterials and a catalyst material.

According to an embodiment of the present invention, the electrode support may include a carbon material as a porous support.

According to an embodiment of the present invention, the porous support may be one selected from carbon paper, carbon cloth, and carbon felt.

According to an embodiment of the present invention, the graphitized carbon nanomaterial includes at least one selected from carbon nanofibers, carbon nanotubes, and carbon nanowires. may be doing

According to an embodiment of the present invention, the graphitized carbon nanomaterial may include one or more selected from cylindrical fibers or tube-shaped materials having an aspect ratio of 5:1 to 10:1.

According to an embodiment of the present invention, the catalyst material is a noble metal black catalyst, a noble metal/carbon supported catalyst, a noble metal alloy catalyst, a transition metal black catalyst, a noble metal-transition metal alloy catalyst, and a noble metal-transition metal alloy/carbon supported catalyst. It may include one or more selected from the group consisting of.

According to an embodiment of the present invention, the noble metal and the transition metal are platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd) , osmium (Os), iridium (Ir), copper (Cu), silver (Ag), gold (Au), tin (Sn), titanium (Ti), chromium (Cr), and alloys thereof selected from the group consisting of It may be one containing more than one type.

According to another aspect of the present invention, there is provided a method for manufacturing an electrode for a fuel cell, comprising the steps of preparing an electrode support, preparing a catalyst ink, and applying the catalyst ink to the electrode support to form a catalyst layer To provide a method for manufacturing an electrode for a fuel cell.

According to an embodiment of the present invention, in the step of preparing the catalyst ink, the ink is prepared by mixing graphitized carbon nanomaterials, a catalyst material, an ionomer and a solvent, and the ink is ultrasonically dispersed. may be distributed.

According to an embodiment of the present invention, the graphitized carbon nanomaterial may be manufactured by heat-treating the carbon nanomaterial at 1800° C. to 3000° C. in an inert atmosphere.

According to an embodiment of the present invention, the graphitized carbon nanomaterial may be included in an amount of 10 wt% to 50 wt% compared to the catalyst material.

The effects of the electrode for a fuel cell and a method for manufacturing the same according to the present invention will be described as follows.

According to at least one of the embodiments of the present invention, self-management of water inside the catalyst layer is possible, thereby maximizing the mass transfer effect.

In addition, there is an effect of obtaining surface hydrophobicity through graphitization of the carbon nanofibers without a separate water-repellent treatment on the surface of the carbon nanofibers.

In addition, since there is no need for a separate supporting process, there is convenience in the process, and there is an effect that carbon nanofibers can be introduced without affecting the platinum particle size.

In addition, the gas fuel is smoothly supplied through a space (water free region) that is empty without water in the catalyst layer, thereby improving output performance.

In addition, there is an effect of improving the durability of the fuel cell through efficient water management.

Further scope of applicability of the present invention will become apparent from the following detailed description. However, it should be understood that the detailed description and specific embodiments such as the preferred embodiments of the present invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention may be clearly understood by those skilled in the art.

1 is a schematic view showing an electrode of a fuel cell including graphitized carbon nanofibers of the present invention.
2 is a flowchart illustrating a method of manufacturing an electrode according to the present invention.
3 is a schematic diagram showing a catalyst ink according to the present invention.
4 is an SEM image of observing a catalyst layer coated with graphitized carbon nanofibers according to the present invention.
5 is an image of observing the contact angle of carbon nanofibers and graphitized carbon nanofibers according to the present invention.
6 shows the performance evaluation results of the fuel cell according to the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and drawings of the present invention. These examples are merely illustrative to explain the present invention in more detail, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples. will be.

In addition, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in case of conflict, this specification, including definitions will take precedence.

In order to clearly explain the invention proposed in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification. And, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated. In addition, as described in the specification, “subordinate” refers to one unit or block that performs a specific function.

In each step, identification numbers (first, second, etc.) are used for convenience of description, and identification numbers do not describe the order of each step, and each step does not clearly describe a specific order in context. It may be performed differently from the order specified above.

That is, each step may be performed in the same order as the specified order, may be performed substantially simultaneously, or may be performed in the reverse order.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art to which the present invention pertains can easily practice the present invention.

The electrode for a fuel cell containing graphitized carbon nanofibers of the present invention and a method for manufacturing the same include a catalyst layer capable of self-water management. It has the distinction of maximizing the mass transfer effect by enabling efficient water management.

In addition, unlike the existing invention using graphitized carbon nanofibers as a support, there is no need for a separate support process, so there is convenience in the process, and carbon nanofibers can be introduced without affecting the platinum particle size. can have advantages.

1 is a schematic view showing an electrode for a fuel cell including graphitized carbon nanofibers according to the present invention.

Referring to FIG. 1 , an electrode 200 for a fuel cell includes an electrode support 130 and a catalyst layer applied to the electrode support 130 , and the catalyst layer is a graphitized carbon nano material 110 and a catalyst material 120 . ), characterized in that it contains.

The electrode support 130 is characterized in that it includes a carbon material as a porous support. In detail, the carbon material is preferably one selected from carbon paper, carbon cloth, and carbon felt, but is not limited thereto.

The graphitized carbon nanomaterial 110 is characterized in that it includes a carbon nanomaterial having a cylindrical structure. In detail, the graphitized carbon nanomaterial 110 is characterized in that it includes at least one selected from carbon nanofibers, tano nanotubes, and carbon nanowires. However, the present invention is not limited thereto, and it is preferable to select and use carbon nanomaterials having a cylindrical structure or a tubular structure.

By using the graphitized carbon nanomaterial 110 having the cylindrical or tubular structure, the fuel passing therethrough is quickly and linearly delivered along the carbon nanomaterial, thereby improving the performance of the fuel cell.

In this case, the graphitized carbon nanomaterial preferably has an aspect ratio (length: width ratio) of 5:1 to 10:1. If the aspect ratio is less than 5:1, it may not be easy to deliver the fuel in a straight line, and if it is greater than 10:1, the graphitized carbon nanomaterial is produced in a fuel cell reaction because the amount of input is small even if the same amount is added. Water may not drain smoothly.

The catalyst material 120 participates in the reaction of the fuel cell, and includes a noble metal black catalyst, a noble metal/carbon supported catalyst, a noble metal alloy catalyst, a transition metal black catalyst, a noble metal-transition metal alloy catalyst, and a noble metal-transition metal alloy/carbon supported catalyst. catalysts and the like.

In this case, the noble metal and the transition metal are platinum (Pt), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), copper (Cu), silver (Ag), gold (Au), tin (Sn), titanium (Ti), chromium (Cr), and containing at least one selected from the group consisting of alloys thereof desirable.

Furthermore, the catalyst material is preferably a platinum/carbon supported catalyst. Specifically, the platinum/carbon supported catalyst is formed by dispersing a platinum ion precursor and a carbon support in a solvent to adsorb platinum ions on the surface of the carbon support, and a platinum/carbon supported catalyst with a maximized platinum loading is used. it is preferable

The platinum ion precursor may include at least one _{of H 2} PtCl ₆ , Na ₂ PtCl ₆ , K ₂ PtCl ₆ and PtCl _{4 .} In addition, the carbon support may be conductive carbon, and micropores may be present on the surface to provide a site for the gold ions to be adsorbed. Specifically, the carbon support is Vulcan, Ketjenblack, Super P At least one of , Timcal, and Activated carbon may be used.

That is, by using a platinum/carbon-supported catalyst in which platinum ions are adsorbed on the surface of the carbon support, the activity of the fuel cell can be improved.

2 is a flowchart illustrating a method of manufacturing an electrode according to the present invention.

Referring to FIG. 2 , the electrode manufacturing method ( S100 ) includes a support preparation step ( S110 ), a catalyst ink preparation step ( S120 ), and a catalyst layer forming step ( S130 ).

The catalyst ink preparation step (S120) is characterized in that the catalyst ink comprising the graphitized carbon nanomaterial 110 and the catalyst material 120 is prepared.

3 is a schematic diagram showing a catalyst ink according to the present invention.

Referring to FIG. 3 , the catalyst ink 100 includes graphitized carbon nanomaterials 110 , catalyst materials 120 , ionomers, and a solvent.

The graphitized carbon nanomaterial 110 is manufactured by graphitizing the carbon nanomaterial, in detail, it is characterized in that it is manufactured by heat-treating the carbon nanomaterial at 1800° C. to 3000° C. in an inert atmosphere. At this time, in order to create an inert atmosphere during the heat treatment, it is preferable to inject a high-purity inert gas having a purity of 99.999% or more, such as high-purity nitrogen or high-purity argon.

In addition, the heat treatment is preferably performed for 30 to 90 minutes. If the heat treatment is shorter than 30 minutes, the carbon nanomaterial may not be graphitized, and if the heat treatment is performed for more than 90 minutes, the fuel cell performance may be reduced due to the reduction of pores of the carbon nanomaterial and the effect on the dispersion degree during ink manufacturing. have.

In addition, the graphitized carbon nanomaterial 110 is preferably included in an amount of 10 wt% to 50 wt% compared to the catalyst material 120 . At this time, when the graphitized carbon nanomaterial 110 is included in an amount of 10 wt% or less compared to the catalyst material 120, the effect of improving the performance is insignificant, and the graphitized carbon nanomaterial 110 is the catalyst material 120 ) compared to 50wt%, it may reduce performance by preventing water discharge due to excessive hydrophobic pores.

The ionomer may include one selected from polytetrafluoroethylene, polyvinylidene fluoride, and polyhexafluoropropylene. The ionomer is a material for increasing the reactivity with the catalyst by favorable conduction of hydrogen ions. If the ionomer is not included, the performance of the fuel cell is reduced, the dispersion of the catalyst is reduced, and the electrode cracking phenomenon may also occur.

The solvent may include at least one selected from pure water, ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, and dimethylacetamide.

In addition, the catalytic ink 100 may perform an ultrasonic dispersion method in order to uniformly disperse the graphitized carbon nanomaterial 110 and the catalytic material 120 in the solvent. In this case, the ultrasonic dispersion method may be processed by dispersing for 60 minutes using a bath sonicator.

The catalyst layer forming step (S130) is to form a catalyst layer by applying the catalyst ink 100 prepared in the catalyst ink production step (S120) to the electrode support 130, in detail, a spray method, a decal method, and The catalyst ink 100 may be coated on the electrode support 130 using a spin coating method or the like.

In addition, after the catalyst ink is applied on the electrode support, the solvent in the ink must be evaporated through a drying process. Specifically, the electrode may be dried in an oven at 60° C. for 3 to 5 hours to form a catalyst layer on the electrode support.

In addition, the catalyst layer is preferably formed to a thickness of 5 μm to 15 μm. When the catalyst layer is formed to a thickness of 5 μm or less, the amount of catalyst is not sufficient, thereby reducing fuel cell performance and may be weak in terms of long-term durability. When formed to a thickness of 15 μm or more, the ohmic resistance of the entire electrode and the resistance of mass transfer may also increase, thereby reducing the performance of the fuel cell.

Hereinafter, the present invention will be described in detail through Examples and Experimental Examples. However, the following Examples and Experimental Examples only illustrate the present invention, and the present invention is not limited by the following Examples and Experimental Examples.

manufacturing example. Preparation of catalyst inks.

A catalyst ink containing a platinum catalyst, graphitized carbon nanofibers, an ionomer, and a solvent (ultra-pure water and IPA) was prepared. The composition is shown in Table 1 below.

Catalyst ink composition Composition ratio (by mass) Platinum Catalyst (46.5 wt % Pt/C) One Graphitized Carbon Nanofibers 0.1 to 0.5 Deionized water 20 to 30 IPA 200 to 300 Ionomer (Nafion ionomer_10wt%) 4 to 5

Example 1.

A catalyst ink containing 45 wt% of graphitized carbon nanofibers (GCF) compared to a platinum catalyst was prepared and applied on an electrode support having a size of ^{5 x 5 cm 2 to prepare a cathode for a fuel cell.}

Example 2.

A catalyst ink containing 75 wt% of graphitized carbon nanofibers (GCF) compared to a platinum catalyst was prepared and applied on an electrode support having a size of ^{5 x 5 cm 2 to prepare a cathode for a fuel cell.}

Comparative Example 1.

Catalyst ink not containing graphitized carbon nanofibers (GCF) was prepared and applied on an electrode support having a size of ^{5 x 5 cm 2 to prepare a cathode for a fuel cell.}

Experimental example

The cell performance of the specimens prepared in Examples 1, 2 and Comparative Example 1 was measured under the conditions of a cell temperature of 80° C. and a relative humidity of 80%. At this time, hydrogen supplied to the anode was introduced with a stoichiometry flow of 1.5, and air supplied to the cathode was introduced with a stoichiometry flow of 1.5, 2.0, and 2.5. Back pressure values were fixed at 1.5 bar for the anode and 2.0 bar for the cathode.

4 is an SEM image of observing a catalyst layer coated with graphitized carbon nanofibers according to the present invention.

Referring to FIG. 4 , it can be confirmed that the graphitized carbon nanofibers and the platinum catalyst are evenly dispersed to form a catalyst layer.

5 is an image of observing the contact angle of carbon nanofibers and graphitized carbon nanofibers according to the present invention.

Referring to FIG. 5, FIG. 5(a) confirms the contact angle of carbon nanofibers that have not undergone graphitization, and it can be confirmed that the contact angle is about 10 degrees. Figure 5 (b) confirms the contact angle of the graphitized carbon nanofibers, it can be confirmed that the contact angle is increased by about 85 degrees. That is, through this, it can be confirmed that the hydrophobicity of the carbon nanofiber surface is increased through graphitization of the carbon nanofiber without a separate water-repellent coating treatment of the carbon nanofiber.

6 shows the performance evaluation results of the fuel cell according to the present invention.

Referring to FIG. 6 , it can be seen that the electrode of Example 1 exhibits higher power compared to Comparative Example 1. In particular, when the stoichionetry value of air is 1.5, it can be confirmed that the improved power is the highest at 18.5% compared to Comparative Example 1.

That is, it can be confirmed that the mass transfer restriction is very serious at a low air flow rate, and thus, it can be confirmed that the mass transfer improvement effect of the graphitized carbon nanofibers is remarkably displayed at a low air flow rate.

In addition, it can be confirmed that the electrode of Example 2 shows a lower power than the electrode of Comparative Example 1. That is, it is considered that when the graphitized carbon nanofibers in the catalyst layer are applied in excess, it is difficult to discharge water by the graphitized carbon nanofibers, and fuel delivery is rather deteriorated.

The electrode for a fuel cell according to the present invention includes a catalyst layer coated with graphitized carbon nanomaterial, and by heat-treating the carbon nanomaterial at a high temperature to produce a graphitized carbon nanomaterial, the graphitized carbon nanomaterial The surface is characterized as having hydrophobic properties.

At this time, when the surface of the graphitized carbon nanomaterial is introduced into the catalyst layer, the water generated is discharged through the pores having a relatively hydrophilicity, and there is no water along the surface of the graphitized carbon nanomaterial that jumps in the hydrophobicity. A water free region is created. In this case, gas fuel (hydrogen or oxygen) is more smoothly supplied through this space, so that the output is improved, and there is an effect of efficiently managing water.

In addition, by efficiently managing the water, there is an effect of improving durability by preventing corrosion of the carbon carrier in the electrode.

In this specification, only a few examples among various embodiments performed by the present inventors will be described, but the technical spirit of the present invention is not limited or limited thereto, and it is of course that it may be modified and variously implemented by those skilled in the art.

100: catalyst ink
110: graphitized carbon nanomaterial
120: catalyst material
130: electrode support
200: electrode for fuel cell

Claims (11)

electrode support;
To include; a catalyst layer applied to the electrode support,
The catalyst layer includes graphitized carbon nanomaterials and catalyst materials,
The catalyst material includes a catalyst formed by adsorbing platinum ions on the surface of a conductive carbon support including micropores,
The graphitized carbon nanomaterial and the catalyst material are uniformly dispersed and applied to the catalyst layer,
Electrodes for fuel cells. delete delete According to claim 1,
The graphitized carbon nanomaterial comprises at least one selected from carbon nanofibers, carbon nanotubes and carbon nanowires,
Electrodes for fuel cells. 5. The method of claim 4,
The graphitized carbon nanomaterial includes at least one selected from a cylindrical fiber or tube-shaped material having an aspect ratio of 5:1 to 10:1,
Electrodes for fuel cells. delete delete preparing an electrode support;
preparing a catalyst ink comprising graphitized carbon nanomaterials and a catalyst material;
forming a catalyst layer by applying a catalyst ink to the electrode support; including,
The catalyst material is formed by adsorbing platinum ions on the surface of a conductive carbon support including micropores,
In the step of forming the catalyst layer, the graphitized carbon nano material and the catalyst material are uniformly dispersed and applied,
A method of manufacturing an electrode for a fuel cell. 9. The method of claim 8,
The step of preparing the catalyst ink,
An ink is prepared by mixing graphitized carbon nanomaterials, catalyst materials, ionomers, and solvents,
The ink is dispersed using an ultrasonic dispersion method,
A method of manufacturing an electrode for a fuel cell. 10. The method of claim 9,
The graphitized carbon nanomaterial is
which is produced by heat-treating carbon nanomaterials at 1800°C to 3000°C in an inert atmosphere,
A method of manufacturing an electrode for a fuel cell. 10. The method of claim 9,
The graphitized carbon nanomaterial is included in 10wt% to 50wt% compared to the catalyst material,
A method of manufacturing an electrode for a fuel cell.

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