KR101995639B1 - Microfluidic fuel cell and method for improving the performance of the same - Google Patents

Abstract

It is an object of the present invention to provide a microfluidic fuel cell with improved performance and a method for improving performance of a microfluidic fuel cell. To this end, the present invention provides a microfluidic fuel cell including a microchannel through which a fuel and an oxidant flow, wherein the microchannel extends in the longitudinal direction of the channel and divides an inner space of the microchannel into a plurality of divided spaces The present invention also provides a microfluidic fuel cell comprising a microchannel in which a fuel and an oxidant flow, the microchannel extending in a longitudinal direction of the channel into a microchannel of the microfluidic fuel cell, Is inserted into a plurality of divided spaces in the microfluidic device. According to the present invention, various types of microfluidic fuel cells including conventional microchannels include a structure for partitioning the inside of a channel, thereby improving the performance of a microfluidic fuel cell.

Description

TECHNICAL FIELD [0001] The present invention relates to a microfluidic fuel cell and a microfluidic fuel cell,

The present invention relates to a method for improving the performance of a microfluidic fuel cell and a microfluidic fuel cell.

Recently, the problem of depletion of fossil energy and environmental problems have become more and more intensified with the emergence of emerging consumption countries such as China, India and Korea, and the rise of resource nationalism in the Middle East and South America. And as the crude oil price surpassed $ 100 in March 2008, the era of high oil prices has arrived. With anxiety about limited fossil energy depletion rising, global energy consumption in 2020 is projected to increase by 45% from 2002 to 15,064 million TOE. Therefore, it is interesting to see the new energy industry, which is eco- .

Fuel cell is a cell that directly converts energy generated by oxidation of fuel into electric energy. In 1839, British physicists Grove and William Robert developed a Grove cell, an anode made of zinc in dilute sulfuric acid and a platinum anode in dense nitric acid, which became the beginning of the current fuel cell. Fuel cells, which are expected to be a new energy source, were commercialized in spacecraft in the 1960s and commercialized in automobiles, home heating and power supplies, and electronic devices. In the 1990s, research on reducing environmental burden due to environmental pollution problems, energy that can achieve energy efficiency nearly twice that of gasoline engines, and auxiliary power for automotive power supplies and fixed power equipment Development is underway. Much research is under way in Korea, which is dependent not only on Europe but also on overseas resources, starting with the United States and Japan.

Fuel cells require exchange membranes. The higher the reaction temperature, the higher the chemical reaction efficiency but the lower the efficiency of the proton exchange as the exchange membrane is dried. Therefore, there is a structural disadvantage that the exchange membrane must be kept hydrated. In addition, fuel crossover, in which the fuel flows back through the exchange membrane, is also pointed out as a major disadvantage. The proton exchange membrane is very expensive and the process becomes complicated when manufacturing the fuel cell.

Microfluidic fuel cells utilize the property that fluids flowing in microchannels form laminar flow and do not mix well. That is, fuel and oxidant fluids flow respectively into the microchannel to form a liquid-liquid interface of the fuel and the oxidant, which replaces the role of the proton exchange membrane. Therefore, problems in proton exchange membrane fuel cells such as membrane humidification, fuel crossover, exchange membrane breakage, and clogging can be easily solved. In addition, since no expensive exchange membrane is used, the process can be simplified and the manufacturing cost can be reduced. However, there is a problem that the performance of the fuel cell is deteriorated due to mixing due to diffusion at the liquid interface.

Therefore, research on microfluidic fuel cells is necessary and important for the development of portable electronic devices power supplies of new energy type. Particularly, various studies are being conducted on a technique for improving the performance of a fuel cell without using a proton exchange membrane.

Korean Patent Laid-Open No. 10-2009-015711 discloses a microfluidic fuel cell in which a channel shape of a fuel cell is limited to a specific shape so that it can flow with a low Reynolds number when a fuel and an oxidant flow, Discloses a technique for improving the efficiency of a fuel cell.

Korean Patent Laid-Open Publication No. 10-2012-0088240 shows that the performance of a fuel cell can be improved by a method including an electrode provided with irregularities.

Further, Korean Patent Laid-Open No. 10-2016-0007718 discloses that the performance of the fuel cell can be improved by changing the shape structure such as the distance between the electrodes.

However, the performance of the microfluidic fuel cell still needs to be improved, and in particular, it is necessary to improve the performance of the microfluidic fuel cell in a manner that does not significantly change its structure.

Accordingly, the inventors of the present invention have made a study of a method for improving the performance of a fuel cell by suppressing a fuel consumption region and a fuel diffusion region generated in a process of flowing a fuel and an oxidant in a microchannel.

It is an object of the present invention to provide a microfluidic fuel cell with improved performance and a method for improving performance of a microfluidic fuel cell.

To this end,

The microfluidic fuel cell includes a microchannel through which a fuel and an oxidant flow, wherein the microchannel extends in a longitudinal direction of the channel and divides an internal space of the microchannel into a plurality of divided spaces A microfluidic fuel cell,

Further, the present invention is characterized by inserting a structure that extends in the longitudinal direction of a channel into a microchannel of a microfluidic fuel cell including a microchannel through which a fuel and an oxidant flow, dividing an inner space of the microchannel into a plurality of divided spaces The microfluidic fuel cell comprising:

According to the present invention, various types of microfluidic fuel cells including conventional microchannels include a structure for partitioning the inside of a channel, thereby improving the performance of a microfluidic fuel cell.

1 is a schematic view showing a known Y-shaped microfluidic fuel cell,
2 is a cross-sectional view perpendicular to the flow direction of a fuel and an oxidant in a microfluidic fuel cell including a structure according to an embodiment of the present invention,
FIG. 3 is a graph showing the performance of a microfluidic fuel cell according to an embodiment of the present invention, and FIG.
4 is a graph showing the concentration gradient of fuel and oxidant in a microfluidic fuel cell according to an embodiment of the present invention.

In the entire specification of the present patent application, 'mixed region' or 'mixing region' and 'fuel diffusion region' or 'fuel diffusion region' are used in the same sense.

The present invention relates to a microfluidic fuel cell with improved performance and a method for improving the performance of a microfluidic fuel cell. Hereinafter, the present invention will be described in detail.

The present invention

A microfluidic fuel cell comprising a microchannel through which a fuel and an oxidant flow,

And a structure that extends in the longitudinal direction of the channel and divides an inner space of the microchannel into a plurality of divided spaces in the microchannel.

Hereinafter, the present invention will be described in detail with respect to each constitution.

The invention relates to a microfluidic fuel cell comprising a microchannel through which a fuel and an oxidant flow, wherein the fuel and the oxidant injected into the fuel cell can be injected together with a known microfluidic fuel cell. For example, an oxidant may be injected into the microchannel through the Y-shaped injection port on one side of the fuel and on the other side.

1 is a schematic view of a conventional microfluidic fuel cell. As can be seen from FIG. 1, the conventional general microfluidic fuel cell has a structure in which the fuel and the oxidant are injected into the Y-shaped end of the microchannel of the fuel cell. In the present invention, the fuel and the oxidant may be injected into the microchannel through the injection unit, for example, as shown in FIG. 1, and then formed into a laminar flow and may flow through the microchannel and be discharged through the exhaust port. In the microfluidic fuel cell according to the present invention, the fuel and the oxidant flow laminarly in the microchannel to form the liquid interface, which replaces the proton exchange membrane, eliminating the need for a separate exchange membrane.

At this time, the microfluidic fuel cell according to the present invention includes a structure that extends in the longitudinal direction of the channel in the microchannel, and divides an internal space of the microchannel into a plurality of divided spaces. The microfluidic fuel cell according to the present invention includes the structure as described above, thereby suppressing the development of the fuel consumption region and the fuel diffusion region, thereby improving the performance of the fuel cell.

The structure according to the present invention is preferably formed so as to cross a surface in contact with the fuel and the oxidant within the microchannel. The fuel and the oxidant injected into the microchannel flow while forming a laminar flow if they form a liquid-liquid interface in the longitudinal direction of the channel. The structure according to the present invention is preferably formed to cross the liquid-liquid interface of the fuel and the oxidant formed in the longitudinal direction of the channel.

It is preferable that a plurality of the above structures included in the microfluidic fuel cell according to the present invention are plural. Further, when a plurality of structures are included, development of the fuel consumption region and the fuel diffusion region can be further suppressed, thereby further improving the performance of the fuel cell.

When there are a plurality of structures, it is preferable that the plurality of structures are parallel to each other. In this case, since the structure may have a single plane from one end to the other end, or may have another shape, the parallelism in the description that the plurality of structures is parallel to each other may be a plane, It means that the structures do not touch each other. As the plurality of structures are formed parallel to each other, the development of the fuel consumption region and the fuel diffusion region can be suppressed, and the performance of the fuel cell can be further improved.

It is preferable that the structure has a cross-sectional shape in which the center portion of the structure is not located on the straight line with the both end portions of the structure on the cross section perpendicular to the direction in which the fuel and the oxidant flow. The structure included in the microfluidic fuel cell according to the present invention may be a flat plane from one end to the other end, or may be in a different form. In particular, when viewed from a cross section perpendicular to the direction in which the fuel and the oxidant flow, the shape of the cross section in which the center portion of the structure is not located in a straight line with the both end portions of the structure, that is, Or have a cross-sectional shape in a sedimented form. As the structure according to the present invention has such a shape, the performance of the fuel cell can be further improved.

As described above, the microfluidic fuel cell according to the present invention has the above-described structure, and thus, in the process of forming the laminar flow of the fuel and the oxidant in the microchannel of the microfluidic fuel cell, And the performance of the fuel cell is improved as a result.

In addition,

And a structure for dividing the inner space of the microchannel into a plurality of divided spaces is inserted into the microchannel of the microchannel of the microchannel fuel cell including the microchannel through which the fuel and the oxidant flow, Thereby improving the performance of the fuel cell.

Hereinafter, the performance improving method of the present invention will be described in more detail.

A microfluidic fuel cell is a fuel cell that does not use a replacement membrane due to the tendency of the fluid to flow and form a laminar flow when the fluid flows at a low speed. Since the exchange membrane is not used, maintenance of wetting of the membrane, fuel backflow phenomenon, Problems such as clogging can be easily solved. In addition, since an expensive exchange membrane is not used, the process can be simplified, and the manufacturing cost can be reduced.

However, on the other hand, as the flow distance of the fuel flow and the oxidant flowing when the laminar flow is formed becomes longer, the fuel consumption region develops between the electrode and the fuel diffusion region necessarily develops at the liquid interface. As a result, the performance of the fuel cell deteriorates due to the fuel consumption region and the fuel diffusion region which are developed according to the structural characteristics. Various studies have been carried out to reduce the fuel consumption area and the fuel diffusion area which are inevitably generated due to the structural characteristics. However, the existing technologies are complicated in structure, so that it is difficult to manufacture, the channel length must be long, There is a problem such as falling.

In the present invention, a structure is formed in which a fuel and an oxidant are injected into the microchannel of the fuel cell, and the microchannel extends in the longitudinal direction of the channel to divide the inner space of the microchannel into a plurality of divided spaces Thereby improving the performance of the microfluidic fuel cell as a result of suppressing the development of the fuel consumption region and the fuel diffusion region.

The fuel consumption area and the fuel diffusion area develop in proportion to the distance of the fuel and the oxidant flowing in the microchannel. The fuel consumption area occurs on the electrode surface, and the byproducts resulting from the oxidation- And the fuel diffusion region is a cause of the reverse flow of the fuel, resulting in deterioration of the performance of the fuel cell.

The present invention relates to a microfluidic fuel cell in which the development of a fuel consumption region and a fuel diffusion region is suppressed through a method of inserting a structure dividing an internal space of a microchannel into a plurality of divided spaces in a longitudinal direction of a channel, Improves performance.

At this time. The fuel and the oxidant flowing into the microchannels of the microfluidic fuel cell flow together forming a laminar flow. When the flowing fuel and the oxidant do not form laminar flow, the performance of the fuel cell greatly deteriorates due to the reverse flow of the fuel.

The structure according to the present invention is preferably inserted into the microchannel so as to cross the surface where the fuel and the oxidant contact each other. The fuel and the oxidant injected into the microchannel flow while forming a laminar flow if they form a liquid-liquid interface in the longitudinal direction of the channel. The structure according to the present invention is preferably inserted across the liquid-liquid interface of the oxidant and the fuel formed in the longitudinal direction of the channel.

It is preferable that a plurality of the above structures included in the microfluidic fuel cell according to the present invention are inserted into the microchannels. Further, when a plurality of structures are included, development of the fuel consumption region and the fuel diffusion region can be further suppressed, thereby further improving the performance of the fuel cell.

When there are a plurality of structures, it is preferable that the plurality of structures are parallel to each other. In this case, since the structure may have a single plane from one end to the other end, or may have another shape, the parallelism in the description that the plurality of structures is parallel to each other may be a plane, It means that the structures do not touch each other. As the plurality of structures are formed parallel to each other, the development of the fuel consumption region and the fuel diffusion region can be suppressed, and the performance of the fuel cell can be further improved.

It is preferable that the structure has a cross-sectional shape in which the center portion of the structure is not located on the straight line with the both end portions of the structure on the cross section perpendicular to the direction in which the fuel and the oxidant flow. In the method for improving the performance of a microfluidic fuel cell according to the present invention, a structure to be inserted may be a flat plane from one end to the other end, or may be in a different form. In particular, when viewed from a cross section perpendicular to the direction in which the fuel and the oxidant flow, the shape of the cross section in which the center portion of the structure is not located in a straight line with the both end portions of the structure, that is, Or have a cross-sectional shape in a sedimented form. As the structure according to the present invention has such a shape, the performance of the fuel cell can be further improved.

As described above, the present invention is advantageous in that the structure of the above-described structure is inserted into the channel of the microfluidic fuel cell so that the fuel consumption region and the fuel diffusion region are prevented from developing in the microchannel, have.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. The following Examples, Comparative Examples and Experimental Examples are merely examples for the explanation of the present invention, and the scope of the present invention is not limited by the matters described in the following Examples, Comparative Examples and Experimental Examples. In the following embodiments, the x-direction is a direction perpendicularly intersecting the liquid-liquid interface formed between the fuel and the oxidant in the direction from one electrode to the other electrode, and the z-direction is a direction perpendicular to the x- There is a section perpendicular to the direction in which the fuel and oxidant flow in the microchannel in the plane between the x-direction and the z-direction.

≪ Example 1 >

Fabrication of Microfluidic Fuel Cell 1

A Y-shaped microfluidic fuel cell of known type was fabricated and the following structure was inserted into the channel of the microfluidic fuel cell. The total length of the microchannels was 30 mm. The thickness of the electrode used for fabrication was 25 μm. The injection direction lengths of the fuel injecting portion and the oxidizing agent injecting portion were all 10 mm and the angle between each injecting portion and the microchannel was 45 ° so that the fuel injecting portion and the oxidizing agent injecting portion formed an angle of 90 °. The insertion direction was inserted in the channel length direction of the microfluidic fuel cell so that the structure crosses the liquid-liquid interface formed between the fuel and the oxidizer in the direction of the opposite electrode from one electrode.

- Shape of structure -

2 (a)

A first structure extending from the one electrode in the x-direction and extending to the other electrode, and forming a surface protruding in the z-direction in the vicinity of a liquid-liquid interface formed by contacting the fuel and the oxidizing agent.

A second structure that extends from one electrode in the x-direction and extends to the other electrode, and forms a surface protruding in the z-direction in a direction opposite to the first structure in the vicinity of a liquid-liquid interface formed by the contact of the fuel and the oxidizer .

The thickness of the first structure and the second structure was 25 μm, and the distance between the first structure and the second structure was 0.15 mm before the z-direction protrusion and 0.25 mm after the protrusion.

≪ Example 2 >

Fabrication of Microfluidic Fuel Cell 2

A microfluidic fuel cell was fabricated in the same manner as in Example 1, except that the shapes of the structures were different.

- Shape of structure -

2 (b)

A first structure extending from the one electrode toward the liquid-liquid interface formed by the fuel and the oxidizing agent in contact with each other and extending to the other electrode, wherein the center of the structure is positioned higher than the both ends of the structure in the z-direction.

Wherein the second structure is located at a predetermined distance from the first structure in the same shape as the first structure.

The thickness of the first structure and the second structure was 25 μm, and the separation distance between the first structure and the second structure was 0.15 mm.

≪ Example 3 >

Fabrication of Microfluidic Fuel Cell 3

A microfluidic fuel cell was fabricated in the same manner as in Example 1, except that the shapes of the structures were different.

- Shape of structure -

2 (c)

A first structure extending from one side of the liquid-liquid interface formed by contacting the fuel and the oxidizer in a rhombic shape on a section perpendicular to the direction of flow of the fuel and the oxidizer.

Wherein the second structure is located at a predetermined distance from the first structure in the same shape as the first structure.

The thicknesses of the first structure and the second structure were 25 μm, and the separation distance between the first structure and the second structure was 0.175 mm.

≪ Comparative Example 1 &

Fabrication of Microfluidic Fuel Cell 4

A conventional Y-shaped microfluidic fuel cell (total microchannel length 30 mm) was used. The injection direction lengths of the fuel injection portion and the oxidant injection portion are all 10 mm, and the angle between each injection portion and the microchannel is 45 °, so that the fuel injection portion and the oxidant injection portion form an angle of 90 °. The rest of the standard is the same as that of the microfluidic fuel cell of Example 1.

<Experimental Example 1>

Fuel cell performance evaluation

The performance of the fuel cells of Examples 1 to 3 and Comparative Example 1 was evaluated by the following method, and the results are shown in FIG.

For the fuel cells of Examples 1 to 3 and Comparative Example 1, the electrochemical flow was simulated using a COMSOL multifunctional analysis commercial program for the flow region inside the actual micro fuel cell channel. The current density and the power density were measured according to the voltage change (0 ~ 0.8 V) of the cathode by injecting fuel and oxidant at the same flow rate (250 μL / min) at room temperature (298 K) and atmospheric pressure (1 atm) The results are shown in Fig.

FIG. 3 shows that the performance of the fuel cell according to the present invention is greatly improved by the insertion of the structure according to the present invention. In particular, the fuel cell including the structure according to the second embodiment of the present invention has the best performance .

<Experimental Example 2>

Confirmation of formation of mixed region according to the shape of structural material

Experiments were conducted on the fuel cells of Examples 1 to 3 in the following manner in order to confirm the mixing region formation behavior of the fuel cell in the microchannel according to the type of the structural member, and the results are shown in FIG.

The electrochemical flow was simulated using the multisectoral ductility analysis program, COMSOL, in the flow regions inside the actual F / F cell channels of Examples 1 to 3. FIG. 4 is a graph showing the results obtained by injecting fuel and oxidant at a flow rate (250 L / min) under the conditions of room temperature (298 K) and atmospheric pressure (1 atm) And the distribution of the fuel concentration when the voltage of the cathode is 0.4 V is shown.

According to Fig. 4, it can be seen that the fuel mixing region is formed relatively small in the case of the practical examples 1 to 3, and in particular, it is confirmed that the fuel mixing region is the least formed in the case of the practical example 2.

Claims (10)

A microfluidic fuel cell comprising a microchannel through which a fuel and an oxidant flow,
And a structure that extends in the longitudinal direction of the channel and divides an internal space of the microchannel into a plurality of divided spaces,
Wherein the structure is formed so as to cross a surface in contact with the fuel and the oxidant within the microchannel.
delete The method according to claim 1,
Wherein a plurality of the structures are present inside the microchannels.
The method of claim 3,
Wherein the plurality of structures are parallel to each other.
The method according to claim 1,
Wherein the structure has a cross-sectional shape in which a central portion on the cross section perpendicular to a direction in which the fuel and the oxidant flow is not positioned in a straight line with the both ends.
A structure for inserting a structure that extends in a longitudinal direction of a channel into a microchannel of a microfluidic fuel cell including a microchannel through which a fuel and an oxidant flow, dividing an inner space of the microchannel into a plurality of divided spaces,
Wherein the structure is inserted into the microchannel so as to cross the surface where the fuel and the oxidant contact each other.
delete The method according to claim 6,
Wherein a plurality of the structures are inserted into the microchannels.
9. The method of claim 8,
Wherein the plurality of structures are parallel to each other.
The method according to claim 6,
Wherein the structure has a cross-sectional shape in which a central portion on a cross section perpendicular to a direction in which the fuel and an oxidant flow is not positioned in a straight line with the both ends.

Images