TWI382581B - Membrane electrode assembly and fuel cell using the same - Google Patents

Description

Membrane electrode and fuel cell using the same

The present invention relates to a membrane electrode and a fuel cell using the membrane electrode, and more particularly to a membrane electrode based on a carbon nanotube and a fuel cell using the membrane electrode.

Fuel cell is an electrochemical power generation device that converts fuel and oxidant gas into electrical energy. It is widely used in military defense and civil power, automotive, communications and other fields (see, Recent advances in fuel cell technology and its application, Journal of Power Sources, V100, P60-66 (2001)).

Generally, a fuel cell mainly includes a Membrane Electrode Assembly (MEA), a Flow Field Plate (FFP), a Current Collector Plate (CCP), and related auxiliary components such as a blower. , valves, pipelines, etc.

A membrane electrode (MEA) is a core component of a fuel cell unit, which is typically composed of a Proton Exchange Membrane and electrodes disposed on both surfaces of the proton exchange membrane. The electrode further includes a Catalyst Layer and a Gas Diffusion Layer (GDL), and the catalytic layer is disposed between the gas diffusion layer and the proton exchange membrane. The proton exchange membrane material is selected from the group consisting of perfluorosulfonic acid, polystyrenesulfonic acid, polytrifluorostyrenesulfonic acid, phenolic resin sulfonic acid or hydrocarbon. The catalytic layer comprises a catalyst material (generally noble metal particles such as platinum, gold or rhodium) and a carrier thereof (generally carbon particles) Such as: graphite, carbon black, carbon fiber or carbon nanotubes). The gas diffusion layer is mainly composed of carbon fiber paper.

However, the membrane electrode of the fuel cell of the prior art has the following disadvantages: First, since the gas diffusion layer is mainly composed of carbon fiber paper, on the one hand, the carbon fiber paper contains a large amount of disorderly distributed carbon fibers, resulting in a pore structure distribution in the carbon fiber paper. Uniform, and small specific surface area, thereby affecting the uniformity of the diffusion of the reaction gas; on the other hand, the carbon fiber paper has a high electrical resistivity, restricting the electrons necessary for the reaction and the electrons generated by the reaction, thereby directly affecting the reactivity of the membrane electrode. Second, since each electrode includes a gas diffusion layer and a catalytic layer formed on the surface of the gas diffusion layer, on the one hand, the structure allows the membrane electrode to have a large thickness, and the membrane electrode gas diffusion layer and the catalytic layer can be enlarged. The contact resistance between them is not conducive to electron conduction; on the other hand, the contact area of the catalyst in the catalyst layer with the reaction gas is small, which limits the utilization of the catalyst.

In view of the above, it is necessary to provide a membrane electrode which has high reactivity and can improve the utilization of a catalyst, and a fuel cell using the membrane electrode.

A membrane electrode comprising: a proton exchange membrane, a first electrode and a second electrode, wherein the first electrode and the second electrode are respectively disposed on two opposite surfaces of the proton exchange membrane, wherein the first At least one of the first electrode and the second electrode comprises at least one nano-carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure includes a long carbon nanotube line and a catalyst distributed in the long carbon nanotube line.

A fuel cell comprising: a proton exchange membrane; a first electrode and a second electrode, the first electrode and the second electrode are respectively disposed on two opposite surfaces of the proton exchange membrane; a first baffle and a second baffle are respectively disposed on the first electrode and the second electrode The electrode is away from the surface of the proton exchange membrane; and a first gas supply and extraction device and a second gas supply and extraction device are respectively connected to the first baffle and the second baffle, wherein the first At least one of the electrode and the second electrode comprises at least one nano-carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure comprises a nano carbon tube long line and a catalyst is distributed in the long carbon nanotube line.

Compared with the prior art, the membrane electrode has the following advantages: First, at least one of the first electrode and the second electrode adopts a composite structure of a long carbon nanotube and a catalyst, so that the prior art can be avoided. The contact resistance between the diffusion layer and the catalyst layer facilitates the conduction of electrons necessary for the reaction and electrons generated by the reaction. Secondly, the long carbon nanotube has a large specific surface area. Therefore, the long carbon nanotube can effectively and uniformly support the catalyst, so that the catalyst has a large contact area with the hydrogen fuel or the oxidant gas, and the catalyst can be improved. Utilization. Third, since the resistivity of the carbon nanotube itself is lower than that of the carbon fiber, the electrode having the composite structure of the long carbon nanotube and the catalyst has a low resistivity and can effectively conduct electrons necessary for the reaction. And the electrons generated by the reaction help to improve the reactivity of the membrane electrode.

The technical solution will be further described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 , an embodiment of the present technical solution provides a membrane electrode 200 including a proton exchange membrane 202 , a first electrode 204 , and a second electrode 206 . The first electrode 204 and the second electrode 206 are respectively disposed on the mass The opposite surfaces of the sub-exchange membrane 202. At least one of the first electrode 204 and the second electrode 206 includes at least one nano carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure includes a long carbon nanotube line and a catalyst distributed on the nano carbon In the long line of the pipe.

The carbon nanotube long line comprises a plurality of carbon nanotubes connected end to end and arranged in a preferred orientation along the axial/longitudinal direction of the long carbon nanotube. Specifically, the carbon nanotubes in the long line of the carbon nanotubes are arranged in parallel or spirally along the axial/longitudinal direction of the long carbon nanotubes. The length of the carbon nanotubes in the long carbon nanotubes is basically the same, and the adjacent carbon nanotubes are closely combined by the van der Waals force. The carbon nanotubes include one or more of a single-walled carbon nanotube, a double-walled carbon nanotube, and a multi-walled carbon nanotube. The single-walled carbon nanotube has a diameter of 0.5 nm to 10 nm, the double-walled carbon nanotube has a diameter of 1.0 nm to 15 nm, and the multi-walled carbon nanotube has a diameter of 1.5 nm to 50 nm. Nano. The length of the carbon nanotubes is greater than 100 microns. In this embodiment, preferably, the length of the carbon nanotubes is 200 to 900 μm.

The long carbon nanotube wire can be obtained by stretching a carbon nanotube array to obtain a carbon nanotube film, mechanically contracting (surface tension of organic solvent volatilization); twist spinning treatment or crimping. The long diameter of the carbon nanotubes is 1 micrometer to 1 millimeter, and the length thereof is not limited, and can be obtained according to actual needs. Before the drawn carbon nanotube film is prepared into a long carbon nanotube line, the catalyst is physically or chemically deposited onto the surface of the carbon nanotube film, and then subjected to mechanical external force shrinkage treatment (surface tension of organic solvent volatilization) ); twisting spinning treatment or crimping can obtain a composite structure of a long carbon nanotube and a catalyst. Referring to Figure 2, the catalyst is evenly distributed on the surface of the carbon nanotube film. Therefore, the carbon nanotubes are long. In the line composite structure, the catalyst is uniformly distributed on the surface of the carbon nanotubes in the long line of the carbon nanotubes.

The material of the catalyst is not limited and may be a mixture of noble metal particles such as platinum, gold, rhodium or any combination thereof. The metal particles have a diameter of 1 to 10 nm. The precious metal catalyst has a loading of less than 0.5 mg/cm ² and is uniformly distributed on the surface of the carbon nanotube long-line carbon nanotube. In this embodiment, the noble metal catalyst is platinum.

The nano carbon tube long-line composite structure is fixed to the surface of the proton exchange membrane 202 by its own viscous, binder or hot pressing method. When the electrode comprises a plurality of nano carbon tube long-line composite structures, a plurality of nano-carbon tube long-line composite structures may be arranged in parallel or crosswise on the surface of the proton exchange membrane 202, and the nano carbon tube long-line composite structure may be No gap setting or interval setting. When a plurality of carbon nanotube long-line composite structures are crossed and spaced apart, a plurality of uniform and regularly distributed micropores are formed between the nano-carbon nanotube long-line composite structures, and the micropore pore size is less than 1 micrometer.

It can be understood that when at least one of the first electrode 204 and the second electrode 206 includes at least one nano tube long-line composite structure, the structure of the other electrode is not limited, and may include a diffusion layer and a catalyst layer setting. On the diffusion layer, the catalyst layer is disposed between the proton exchange membrane and the diffusion layer. The diffusion layer can be a carbon fiber paper or a carbon nanotube layer. The catalyst layer comprises a precious metal catalyst material and a support thereof (generally carbon particles such as graphite, carbon black, carbon fiber or carbon nanotubes). In this embodiment, preferably, the first electrode 204 and the second electrode 206 each comprise a plurality of carbon nanotube long-line composite structures. Moreover, the plurality of carbon nanotube long-line composite structures are disposed in parallel with no gaps on the two phases of the proton exchange membrane 202. Right surface.

The material of the proton exchange membrane 202 is perfluorosulfonic acid, polystyrenesulfonic acid, polytrifluorostyrenesulfonic acid, phenolic resinsulfonic acid or hydrocarbon. In this embodiment, the material of the proton exchange membrane 202 is perfluorosulfonic acid.

The membrane electrode 200 has the following advantages: First, the first electrode 204 and the second electrode 206 both adopt a composite structure of a long carbon nanotube and a catalyst, so that the diffusion layer and the catalyst layer in the prior art can be avoided. The contact resistance facilitates the conduction of electrons necessary for the reaction and electrons generated by the reaction. Secondly, the long carbon nanotube has a large specific surface area. Therefore, the long carbon nanotube can effectively and uniformly support the catalyst, so that the catalyst has a large contact area with the hydrogen fuel or the oxidant gas, and the catalyst can be improved. Utilization. Third, since the resistivity of the carbon nanotube itself is lower than that of the carbon fiber, the electrode having the composite structure of the long carbon nanotube and the catalyst has a low resistivity and can effectively conduct electrons necessary for the reaction. And the electrons generated by the reaction help to improve the reactivity of the membrane electrode. Fourth, the first electrode 204 and the second electrode 206 both adopt a composite structure of a long carbon nanotube and a catalyst, and the long carbon nanotube has a function of collecting current and supporting the catalyst and diffusing hydrogen fuel or oxidant gas. The structure is simple and convenient to use.

Referring to FIG. 3, the embodiment of the present invention further provides a fuel cell 20, including: a membrane electrode 200, a first deflector 208a and a second deflector 208b, a first current collector 216a and A second current collecting plate 216b, and a first air supply and exhausting device 210a and a second air supply and air extracting device 210b.

The structure of the membrane electrode 200 is as described above. That is, the first electrode 204 and the second electrode 206 each include a composite structure of a plurality of carbon nanotube long wires and noble metal catalyst particles. Moreover, the plurality of carbon nanotube long-line composite structures are disposed in parallel without gaps on the opposite surfaces of the proton exchange membrane 202.

The first baffle 208a and the second baffle 208b are respectively disposed on the surface of the first electrode 204 and the second electrode 206 away from the proton exchange membrane 202. The surface of the first baffle 208a and the second baffle 208b adjacent to the proton exchange membrane 202 has one or more flow guiding grooves 212 for conducting fuel gas, oxidant gas and reaction product water. The first baffle 208a and the second baffle 208b are made of metal or conductive carbon material.

The first current collecting plate 216a and the second current collecting plate 216b are made of a conductive material, and are respectively disposed on the surface of the first baffle 208a and the second baffle 208b remote from the proton exchange film 202 for collecting and conducting. The electrons produced by the reaction. It can be understood that, in this embodiment, since the long carbon nanotubes themselves have good electrical conductivity and can be used for collecting current, the first current collecting plate 216a and the second current collecting plate 216b are an optional structure.

The first air supply and extraction device 210a and the second air supply and extraction device 210b include a blower, a pipeline, a valve, and the like (not shown). The blower is connected to the first baffle 208a and the second baffle 208b through pipelines for supplying fuel gas and oxidant gas to the fuel cell 20. In this embodiment, the fuel gas is hydrogen, and the oxidant gas is pure oxygen or oxygen-containing air. Among them, the second electrode 206 in the fuel cell 20 near the input end of the oxidant gas is referred to as a cathode, and the first electrode 204 near the input end of the fuel gas is referred to as an anode.

When the fuel cell 20 is in operation, the fuel gas (hydrogen gas) and the oxidant gas (pure oxygen or oxygen-containing air) are respectively supplied to the membrane electrode 200 through the gas guide plate 208 by the gas supply and the evacuation device 210. Among them, hydrogen gas reaches the anode through the flow guiding groove 212. Under the action of the catalyst, hydrogen reacts as follows: H ₂ → 2H ⁺ + 2e. The protons generated by the reaction pass through the proton exchange membrane 202 to the cathode, and the electrons generated by the reaction pass through the external circuit to the cathode.

At the other end of the fuel cell 20, oxygen enters the cathode while electrons pass through the external circuit to the cathode. Under the action of the catalyst, oxygen reacts with protons and electrons as follows: 1/2O ₂ + 2H ⁺ + 2e → H ₂ O. The water generated by the reaction is discharged from the fuel cell 20 through the second electrode 206 and the deflector 208. During this process, a certain potential difference is formed between the first electrode 204 and the second electrode 206, and when an external circuit is connected to a load 214, a current will be formed.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

20‧‧‧ fuel cell

200‧‧‧ membrane electrode

202‧‧‧Proton exchange membrane

204‧‧‧First electrode

206‧‧‧second electrode

208a‧‧‧First deflector

208b‧‧‧Second deflector

210a‧‧‧First gas supply and extraction device

210b‧‧‧Second gas supply and extraction device

212‧‧‧Guide trough

214‧‧‧ load

216a‧‧‧First header plate

216b‧‧‧Second Collector

FIG. 1 is a schematic structural view of a membrane electrode according to an embodiment of the present technical solution.

2 is a partial scanning electron micrograph of a carbon nanotube film deposited on a surface with a platinum layer provided by an embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a fuel cell according to an embodiment of the present technical solution.

200‧‧‧ membrane electrode

202‧‧‧Proton exchange membrane

204‧‧‧First electrode

206‧‧‧second electrode

Claims (20)

A membrane electrode comprising: a proton exchange membrane, a first electrode and a second electrode, wherein the first electrode and the second electrode are respectively disposed on two opposite surfaces of the proton exchange membrane, and the improvement is that At least one of the first electrode and the second electrode comprises at least one nano carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure comprises a long carbon nanotube line composed of a plurality of carbon nanotubes and The catalyst is distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The membrane electrode according to claim 1, wherein at least one of the first electrode and the second electrode comprises a plurality of carbon nanotube long-line composite structures arranged in parallel or crosswise disposed on the proton exchange membrane. surface. The membrane electrode according to claim 1, wherein the nano carbon tube long-line composite structure has a diameter of 1 μm to 1 mm. The membrane electrode according to claim 1, wherein the carbon nanotubes are connected end to end and arranged in a preferred orientation. The membrane electrode according to claim 4, wherein the carbon nanotubes are arranged in parallel along an axial direction of the nanocarbon long-chain composite structure. The membrane electrode according to claim 4, wherein the carbon nanotubes are arranged in an axial spiral along a long-line composite structure of the carbon nanotubes. The membrane electrode of claim 4, wherein the adjacent carbon nanotubes are tightly bonded by van der Waals force. The membrane electrode according to claim 4, wherein the carbon nanotube has a length of 200 to 900 μm and a diameter of less than 50 nm. The membrane electrode according to claim 4, wherein the catalyst is uniformly distributed on the surface of the carbon nanotube in the long line of the carbon nanotube. The membrane electrode according to claim 1, wherein the catalyst is a noble metal particle. The membrane electrode according to claim 10, wherein the noble metal material is one of platinum, gold or rhodium or a mixture of any combination thereof. The membrane electrode according to claim 1, wherein the first electrode and the second electrode each comprise at least one nano carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure comprises a plurality of The nano carbon tube long line and the precious metal particle catalyst composed of the carbon nanotubes are evenly distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The membrane electrode according to claim 12, wherein the noble metal material is one of platinum, gold or rhodium or a mixture of any combination thereof. A fuel cell comprising: a proton exchange membrane; a first electrode and a second electrode, wherein the first electrode and the second electrode are respectively disposed on two opposite surfaces of the proton exchange membrane; a first diversion a plate and a second baffle are respectively disposed on the surface of the first electrode and the second electrode remote from the proton exchange membrane; and a first gas supply and extraction device and a second gas supply and extraction device respectively and the first guide The flow plate and the second baffle are connected to each other, and the improvement is that at least one of the first electrode and the second electrode comprises at least one nano-carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure comprises A long carbon nanotube and a catalyst composed of a plurality of carbon nanotubes are distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The fuel cell according to claim 14, wherein the carbon nanotubes are connected end to end and arranged in a preferred orientation, and the catalyst is uniformly distributed on the surface of the nanocarbon. The fuel cell of claim 14, wherein the catalyst is a noble metal particle. The fuel cell according to claim 16, wherein the noble metal material is one of platinum, gold or rhodium or a mixture of any combination thereof. The fuel cell of claim 14, wherein the first electrode and the second electrode each comprise at least one nano carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure comprises a plurality of The carbon nanotube long line and the noble metal particle catalyst composed of the carbon nanotubes are uniformly distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The fuel cell of claim 14, wherein the surface of the first baffle and the second baffle near the proton exchange membrane has one or more flow guiding grooves. The fuel cell of claim 14, further comprising a first current collecting plate and a second current collecting plate respectively disposed on the surface of the first baffle and the second baffle away from the proton exchange membrane .