TWI382580B - Membrane electrode assembly and biofuel cell using the same - Google Patents

Description

Membrane electrode and biofuel cell using the same

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

Biofuel cells are devices that use enzymes as catalysts to convert chemical energy in organic matter directly into electrical energy. Generally, the prior biofuel cell includes: a Membrane Electrode Assembly (MEA), the membrane electrode includes a proton exchange membrane (Proton Exchange Membrane) and cathode electrodes respectively disposed on opposite surfaces of the proton exchange membrane and An anode electrode; an anode chamber containing biofuel, and the anode electrode is immersed in the biofuel; a flow field plate (FFP) is disposed on the surface of the cathode electrode away from the proton exchange membrane; a current collector (Current Collector Plate, referred to as CCP) is placed on the surface of the deflector away from the proton exchange membrane; and related auxiliary components such as blowers, valves, pipelines, etc.

Wherein, the anode electrode comprises a carbon fiber paper and an enzyme catalyst distributed on the surface of the carbon fiber paper. The cathode electrode includes a gas diffusion layer and a catalyst layer disposed on the surface of the gas diffusion layer, and the catalyst layer is located at the proton Between the exchange membrane and the gas diffusion layer. The catalyst layer comprises a catalyst material (generally noble metal particles such as platinum, gold or rhodium, etc.) and a support thereof (generally carbon particles such as graphite, carbon black, carbon fibers or carbon nanotubes). The gas diffusion layer is mainly composed of carbon fiber paper. The proton exchange membrane material is selected from the group consisting of perfluorosulfonic acid, polystyrenesulfonic acid, polytrifluorostyrenesulfonic acid, phenolic resin sulfonic acid or hydrocarbon.

However, the membrane electrode of the biofuel cell of the prior art has the following disadvantages: First, since the anode electrode includes a carbon fiber paper and an enzyme catalyst distributed on the surface of the carbon fiber paper, on the one hand, the carbon fiber paper contains a large amount of disorderly distribution. Carbon fiber causes uneven distribution of pore structure in carbon fiber paper, and has small specific surface area, which affects the uniformity of enzyme catalyst distribution, makes the contact area of enzyme catalyst and biofuel small, and limits the utilization of catalyst; on the other hand, carbon fiber paper resistance The rate is large, which restricts the transmission of electrons generated by the reaction, thereby directly affecting the reactivity of the membrane electrode. Second, since the cathode electrode includes a gas diffusion layer and a catalytic layer formed on the surface of the gas diffusion layer, on the one hand, the cathode electrode structure allows the prepared membrane electrode to have a large thickness and can increase gas diffusion in the membrane electrode. The contact resistance between the layer and the catalytic layer is not conducive to the electron conduction necessary for the reaction, thereby directly affecting the reactivity of the membrane electrode; on the other hand, the catalyst dispersion in the catalytic layer in the cathode electrode structure is uniform, and the reaction gas The contact area is small, limiting 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 biofuel cell using the membrane electrode.

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

A biofuel cell comprising: a proton exchange membrane; an anode electrode and a cathode electrode, the anode electrode and the cathode electrode being respectively disposed on two opposite surfaces of the proton exchange membrane; and an anode chamber containing biofuel And an anode electrode is immersed in the biofuel; a baffle is disposed on the surface of the cathode electrode remote from the proton exchange membrane; and a gas supply and extraction device is in communication with the baffle, wherein the anode electrode includes at least A nanometer carbon tube long-line composite structure, and the nano-carbon tube long-line composite structure includes a long carbon nanotube line and an enzyme catalyst distributed in the long line of the carbon nanotube.

Compared with the prior art, the membrane electrode has the following advantages: First, the anode electrode adopts a long carbon wire composite structure of a carbon nanotube, so that the contact resistance between the diffusion layer and the catalyst layer in the prior art can be avoided, which is advantageous. The electrons necessary for the reaction and the conduction of electrons generated by the reaction. Second, 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 enzyme catalyst has a large contact area with the biofuel, and the enzyme catalyst can be improved. Utilization rate. Third, since the resistivity of the carbon nanotube itself is lower than that of the carbon fiber, the anode electrode using the nanowire long-line composite structure has a low electrical resistivity, and can effectively conduct electrons and reactions necessary for the reaction. Generated electron It helps 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 , an anode electrode 204 , and a cathode electrode 206 . The anode electrode 204 and the cathode electrode 206 are respectively disposed on two opposite surfaces of the proton exchange membrane 202. At least one of the anode electrode 204 and the cathode electrode 206 includes a carbon nanotube long-line composite structure. Wherein, the anode electrode 204 is a composite structure of a long carbon nanotube tube and an enzyme catalyst. The cathode electrode 206 is a composite structure of a carbon nanotube long line and a noble metal catalyst.

The long carbon nanotube line comprises a plurality of carbon nanotubes arranged end to end and arranged in a preferred orientation. 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 tightly coupled by van der Waals. 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 nai The long diameter of the carbon tube is 1 micron to 1 mm in diameter, and its length is not limited, and can be obtained according to actual needs. By immersing the above long carbon nanotubes in a glucose oxidase aqueous solution, a composite structure of a long carbon nanotube and an enzyme catalyst can be obtained. Before preparing the composite structure of the long carbon nanotube and the enzyme catalyst, it is necessary to functionalize the long carbon nanotube line to introduce hydrophilicity on the wall or end cap of the carbon nanotube in the long line of the carbon nanotube. The carboxyl group (-COOH) or hydroxyl group (-OH) enhances the adsorption of the carbon nanotube to the enzyme catalyst. Therefore, in the composite structure of the long carbon nanotube and the enzyme catalyst, the enzyme catalyst is evenly distributed on the surface of the carbon nanotubes of the long carbon nanotubes. Before the drawn carbon nanotube film is prepared into a long carbon nanotube wire, the precious metal catalyst is physically or chemically deposited on the surface of the carbon nanotube film, and then subjected to mechanical external force shrinkage treatment (surface tension of organic solvent volatilization) Function); twist spinning treatment or crimping to obtain a composite structure of a long carbon nanotube and a noble metal catalyst. Referring to Figure 2, the platinum catalyst is uniformly distributed on the surface of the carbon nanotube film. Therefore, in the composite structure of the long carbon nanotube and the noble metal catalyst, the noble metal catalyst is uniformly distributed on the surface of the carbon nanotube long-line carbon nanotube.

The enzyme catalyst can be any enzyme catalyst capable of catalyzing a biofuel, such as an oxidase containing a prosthetic FAD or a dehydrogenase containing a prosthetic NAD(P) ⁺ . The enzyme catalyst is uniformly adsorbed on the surface of the carbon nanotube in the long line of the carbon nanotube and bonded to the carbon nanotube through a carboxyl group or a hydroxyl group. It will be appreciated that the different enzyme catalysts used will be different for different biofuels. In this embodiment, the biofuel is a glucose solution, and the enzyme catalyst is glucose oxidase.

The noble metal catalyst is a noble metal particle such as one of platinum, gold, rhodium or a mixture of 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 anode electrode 204 or the cathode electrode 206 includes 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 carbon nanotubes are long. There can be no gap setting or spacing between the line composite structures. 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 the anode electrode 204 includes a composite structure of at least one carbon nanotube long line and an enzyme catalyst, the cathode electrode 206 is not limited in structure, and may include a diffusion layer and a catalyst layer disposed on the diffusion layer. And 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). When the cathode electrode 206 includes a composite structure of at least one carbon nanotube long line and a noble metal catalyst, the anode electrode 204 is not limited in structure, and may include a diffusion layer and a catalyst layer disposed on the diffusion layer, and the catalyst The 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 an enzyme catalyst material and a carrier thereof (generally carbon particles) Grain, such as: graphite, carbon black, carbon fiber or carbon nanotubes). In this embodiment, preferably, the anode electrode 204 and the cathode electrode 206 each comprise a plurality of carbon nanotube long-line composite structures. That is, the anode electrode 204 includes a composite structure of a plurality of carbon nanotube long lines and an enzyme catalyst. The cathode electrode 206 includes a composite structure of a plurality of carbon nanotube long wires and a noble metal catalyst. Further, a plurality of carbon nanotube long-line composite structures are disposed in parallel with the gap on the surface of the proton exchange membrane 202.

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 anode electrode 204 and the cathode electrode 206 are both made of a long carbon nanotube composite structure, so that the contact resistance between the diffusion layer and the catalyst layer in the prior art can be avoided. The electrons necessary for the reaction and the conduction of electrons generated by the reaction. Second, 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 biofuel 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 long-line composite structure of the carbon nanotube has a low electrical resistivity, and can effectively conduct electrons and reaction formation necessary for the reaction. The electrons help to improve the reactivity of the membrane electrode. Fourth, the anode electrode 204 and the cathode electrode 206 both adopt a long carbon composite structure of a carbon nanotube, and the long carbon nanotube has a function of collecting current and supporting the catalyst and diffusing the biofuel or the oxidant gas, and has a simple structure and is used. Convenience.

Referring to FIG. 3, the embodiment of the present technical solution further provides a biofuel cell 20 using the membrane electrode 200, which comprises: a membrane electrode 200, an anode chamber 214, a baffle 208, and a current collecting plate 210. And a gas supply and extraction device 212.

The structure of the membrane electrode 200 is as described above. Moreover, the anode electrode 204 includes a plurality of carbon nanotube long lines and a composite structure of the enzyme catalyst disposed on the surface of the proton exchange membrane 202 without gaps. The cathode electrode 206 includes a plurality of carbon nanotube long lines and a composite structure of a noble metal catalyst disposed on the surface of the proton exchange membrane 202 without a gap.

The anode chamber 214 is disposed on the anode electrode 204 side of the membrane electrode 200 for loading the biofuel 216. In this embodiment, the biofuel 216 is a glucose solution. The membrane electrode 200 separates the biofuel 216 from the oxidant gas, and the anode electrode 204 is immersed in the biofuel 216 such that the enzyme catalyst can be in contact with the biofuel 216.

The baffles 208 are respectively disposed on the surface of the cathode electrode 206 away from the proton exchange membrane 202, and have one or more flow guiding grooves 218 on the surface of the baffle 208 near the cathode electrode 206 for conducting the oxidant gas and the reaction product. water. The baffle 208 is made of a metal or conductive carbon material.

The current collecting plate 210 is made of a conductive material and is disposed on a surface of the baffle 208 remote from the proton exchange membrane 202 for collecting and conducting electrons required for the reaction. It can be understood that, in this embodiment, since the long-line structure of the carbon nanotube has good conductivity and can be used for collecting current, the current collecting plate 210 is an optional structure.

The air supply and air extraction device 212 includes a blower, a pipeline, a valve, etc. Not shown). The blower is connected to the baffle 208 through a conduit for providing oxidant gas to the cathode electrode 206. In this embodiment, the oxidant gas is pure oxygen or oxygen-containing air.

When the biofuel cell 20 is in operation, at the end of the anode electrode 204, the biofuel 216 (taking glucose as an example) undergoes the following reaction under the catalysis of the enzyme catalyst: glucose → gluconic acid + 2H ⁺ + 2e. The protons generated by the reaction pass through the proton exchange membrane 202 to reach the cathode electrode 206, and the electrons generated by the reaction enter the external circuit.

At one end of the cathode electrode 206, an oxidant gas (taking oxygen as an example) is introduced into the cathode electrode 206 through the deflector 208 by means of its gas supply and suction means 212. While oxygen diffuses to the cathode electrode 206, electrons pass through the external circuit to the cathode electrode 206. Under the action of the noble metal catalyst, oxygen reacts with protons and electrons as follows: 1/2O ₂ + 2H ⁺ + 2e → H ₂ O. During this process, a certain potential difference is formed between the anode electrode 204 and the cathode electrode 206, and when an external circuit is connected to a load 220, a current will be formed. The water generated by the reaction is discharged from the biofuel cell 20 through the deflector 208.

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‧‧‧Biofuel cell

200‧‧‧ membrane electrode

202‧‧‧Proton exchange membrane

204‧‧‧Anode electrode

206‧‧‧Cathode electrode

208‧‧‧ deflector

210‧‧‧ Collector

212‧‧‧Air supply and extraction devices

214‧‧‧Anode chamber

216‧‧ biofuels

218‧‧ ‧ guide trough

220‧‧‧load

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

2 is a surface carbon-deposited nano-carbon with a platinum layer provided by an embodiment of the present technical solution. A partial scanning electron micrograph of the tube film.

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

200‧‧‧ membrane electrode

202‧‧‧Proton exchange membrane

204‧‧‧Anode electrode

206‧‧‧Cathode electrode

Claims (20)

A membrane electrode comprising: a proton exchange membrane, an anode electrode and a cathode electrode, wherein the anode electrode and the cathode electrode are respectively disposed on two opposite surfaces of the proton exchange membrane, wherein the anode electrode comprises at least a nanometer carbon tube long-line composite structure, the nano-carbon tube long-line composite structure comprises a long carbon nanotube composed of a plurality of carbon nanotubes and an enzyme catalyst distributed in the plurality of nanotubes in the long line of the carbon nanotube Carbon tube surface. The membrane electrode according to claim 1, wherein the anode electrode comprises a plurality of carbon nanotube long-line composite structures arranged in parallel or crosswise on a surface of the proton exchange membrane. 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 according to claim 4, wherein the adjacent carbon nanotubes are tightly bonded by van der Waals. 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 surface of the carbon nanotube comprises a plurality of carboxyl groups or hydroxyl groups, and the enzyme catalyst is uniformly adsorbed on the surface of the carbon nanotube by the carboxyl group or the hydroxyl group. The membrane electrode according to claim 1, wherein the enzyme catalyst comprises an oxidase or a dehydrogenase. The membrane electrode according to claim 1, wherein the cathode electrode comprises at least one carbon nanotube long-line composite structure, and the nano-carbon nanotube long-line composite structure comprises a plurality of carbon nanotubes. The carbon nanotube long line and the catalyst are distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The membrane electrode according to claim 11, wherein the catalyst is a noble metal particle uniformly distributed 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. The membrane electrode according to claim 1, wherein the cathode electrode comprises a diffusion layer and a catalyst layer formed on a surface of the diffusion layer, and the catalyst layer is disposed between the proton exchange membrane and the diffusion layer. The membrane electrode of claim 14, wherein the diffusion layer comprises a carbon nanotube layer or a carbon fiber paper. A biofuel cell comprising: a proton exchange membrane; an anode electrode and a cathode electrode, wherein the anode electrode and the cathode electrode are respectively disposed on two opposite surfaces of the proton exchange membrane; and a chamber containing biofuel, And an anode electrode is immersed in the biofuel; a baffle is disposed on the surface of the cathode electrode away from the proton exchange membrane; and a gas supply and extraction device is in communication with the baffle, the improvement is that the anode electrode comprises a long-line composite structure of at least one nano carbon tube, and the nano-carbon tube long-line composite structure comprises a long carbon nanotube composed of a plurality of carbon nanotubes and an enzyme catalyst distributed in the long line of the carbon nanotube The surface of a carbon nanotube. The biofuel cell according to claim 16, wherein the carbon nanotubes are connected end to end and arranged in a preferred orientation. The biofuel cell according to claim 16, wherein the cathode electrode comprises at least one carbon nanotube long-line composite structure, and the nano-carbon tube long-line composite structure comprises a plurality of carbon nanotubes. The long carbon nanotubes and the catalyst are distributed on the surface of the plurality of carbon nanotubes in the long line of the carbon nanotube. The biofuel cell according to claim 18, wherein the catalyst is a noble metal particle, the material of which is one of platinum, gold or rhodium, or a mixture of any combination thereof, the noble metal particles being uniformly distributed in the nanometer. The carbon tube is in the long line. The biofuel cell according to claim 16, wherein the biofuel cell further comprises a current collecting plate disposed on a surface of the baffle plate remote from the proton exchange membrane.