KR20080045416A - Method of driving direct oxidation fuel cell system - Google Patents

Abstract

A method for driving a direct oxidation fuel cell system is provided to prevent a power reduction problem over time in the direct oxidation fuel cell system, thereby improving life characteristics of the fuel cell. A direct oxidation fuel cell system includes: at least one electricity generation part(101) which comprises a membrane-electrode assembly having an anode electrode and a cathode electrode placed to face each other, and a polymer electrolyte membrane placed between the anode and cathode electrodes, and separators placed on both sides of the membrane-electrode assembly, and generates electricity through oxidation of fuel and reduction of an oxidant; a fuel supply part(102) which supplies fuel to the electricity generation parts through a fuel pump(130); and an oxidant supply part(103) which supplies an oxidant to the electricity generation part. A method for driving the direct oxidation fuel cell system includes a step of performing driving under the condition capable of supplying fuel in a stoichiometry of 3-10 when a ratio of the actual amount of fuel supplied to the theoretical amount of fuel supplied is stoichiometry.

Description

METHOOD OF DRIVING DIRECT OXIDATION FUEL CELL SYSTEM}

1 is a view schematically showing the structure of a direct oxidation fuel cell system of the present invention.

Figure 2 is a graph showing the measurement of the voltage and output density according to the use time of the direct oxidation fuel cell prepared according to Examples 1, 2, 4 and Comparative Examples 1, 2 of the present invention.

[Industrial use]

The present invention relates to a method for driving a direct oxidizing fuel cell system, and more particularly, to facilitate CO ₂ emission, thereby preventing a problem of output reduction with time in a direct oxidizing fuel cell. The present invention relates to a method of driving a direct oxidation fuel cell system capable of improving characteristics.

  [Prior art]

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

This fuel cell is a clean energy source that can replace fossil energy, and has the advantage of generating a wide range of outputs by stacking unit cells, and having an energy density of 4-10 times that of a small lithium battery. It is attracting attention as a compact and mobile portable power source.

Representative examples of the fuel cell include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell (Direct Oxidation Fuel Cell). The use of methanol as fuel in the direct oxidation fuel cell is called a direct methanol fuel cell (DMFC).

The polymer electrolyte fuel cell has an advantage of having a high energy density and a high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen as fuel gas. There is a problem that requires additional equipment such as a device.

On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but it is easy to handle fuel and has a low operating temperature, so that it can be operated at room temperature, in particular, it does not require a fuel reformer.

In such fuel cell systems, the stack that substantially generates electricity comprises several unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a structure laminated to several tens. The membrane-electrode assembly is called an anode electrode (also called a “fuel electrode” or an “oxide electrode”) and a cathode electrode (one side “air electrode” or “reduction electrode”) with a polymer electrolyte membrane including a hydrogen ion conductive polymer therebetween. ) Is located.

  The principle of generating electricity in a fuel cell is that fuel is supplied to an anode electrode, which is a fuel electrode, adsorbed to a catalyst of the anode electrode, and the fuel is oxidized to generate hydrogen ions and electrons. Reaching the cathode electrode, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode electrode. An oxidant is supplied to the cathode, and the oxidant, hydrogen ions, and electrons react on the catalyst of the cathode to generate electricity while generating water.

Disclosure of Invention An object of the present invention is to drive CO ₂ emissions, thereby preventing a problem of power reduction over time in a direct oxidation fuel cell, and thus driving a direct oxidation fuel cell system that can improve the life characteristics of the fuel cell. To provide.

In order to achieve the above object, the present invention provides at least one electricity generating unit for generating electricity through the oxidation reaction of the fuel and the reduction reaction of the oxidant, a fuel supply unit for supplying fuel to the electricity generating unit through a fuel pump, and an oxidant In the method of driving a direct oxidation type fuel cell system including an oxidant supply unit for supplying to the electricity generating unit, when the ratio of the actual fuel supply to the theoretical fuel supply is stoichiometry, the stoichiometry is 3 to 10. A method of driving a direct oxidation fuel cell system including a step of driving under a fuel supply condition is provided. In this case, the electricity generating unit includes a membrane-electrode assembly including an anode electrode and a cathode electrode positioned opposite to each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode; And separators positioned on both sides of the membrane-electrode assembly.

Hereinafter, the present invention will be described in more detail.

A direct oxidation fuel cell is a system that generates electricity by inducing an electrochemical reaction by injecting an oxidant into a cathode electrode and fuel into an anode electrode, and water is generated and discharged from the cathode electrode side as a result of the electrochemical reaction. CO ₂ is generated and discharged from the electrode side. At this time, it can be divided into active type (active type) and passive type (called passive type, or air breathing type) according to the injection method of the oxidant and fuel. The active type is a method of supplying the oxidant by using a pump. In the case of the passive type, the oxidant is supplied to the cathode electrode by convection without such equipment, and the fuel is also generally supplied to the anode electrode by diffusion. Will be supplied. Accordingly, in the case of the passive fuel cell, there is no oxidant compressor, which is a peripheral device (Balance of plant: BOP), which supplies an oxidant to the cathode and discharges water. There is no fuel supply pump, a BOP that fuels and releases CO ₂ . Therefore, this series of reactions are difficult to occur smoothly, and the output characteristics of the membrane-electrode assembly are reduced due to the problem of releasing water and CO ₂ , which are reaction products. In general, in the passive type direct oxidation type fuel cell, the output characteristics of the membrane-electrode assembly with time change are reduced by 30 to 50% between 30 minutes and 1 hour.

On the other hand, the present invention includes a pump for supplying fuel to the cathode electrode side, and by setting the fuel supply of the pump to the optimum conditions to drive the fuel cell, by increasing the flow rate of the anode electrode to facilitate the discharge of CO _{2 as} a product Therefore, it was possible to prevent the power reduction problem over time in the direct oxidation fuel cell, thereby improving the life characteristics of the fuel cell.

That is, the driving method of the direct oxidation type fuel cell system according to an embodiment of the present invention includes at least one electricity generation unit for generating electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant, and the fuel through the fuel pump. A method of driving a direct oxidation fuel cell system comprising a fuel supply unit for supplying an electricity generator and an oxidant supply unit for supplying an oxidant to the electricity generator, wherein the ratio of the actual fuel supply to the theoretical fuel supply is called stoichiometry. In this case, the step of driving under the conditions of supplying fuel at the stoichiometry of the 3 to 10.

More preferably, the fuel cell may be operated under conditions for supplying fuel with stoichiometry of 3 to 6. If the stoichiometry is less than 3, CO2 emission is not preferable for supplying fuel and if it is more than 10, methanol crossover is increased and output is drastically reduced, which is not preferable.

In addition, the fuel cell is preferably driven at a temperature range of room temperature to 50 ° C, more preferably at a temperature range of 30 ° C to 50 ° C. Room temperature means 15 ° C usually known to those skilled in the art. When the driving temperature range of the fuel cell is lower than room temperature, it is not preferable because the operation stability is lowered by flooding at the cathode electrode, and when the temperature exceeds 50 ° C, the membrane is dried and the output is decreased, which is not preferable.

In addition, the fuel is preferably used at a concentration of 1 to 10M, more preferably at a concentration of 2M to 5M. If the concentration of the fuel is less than 1M, the concentration is low, which is not preferable for fuel supply. If the concentration of the fuel is more than 10M, the methanol crossover increases and the output decreases rapidly, which is not preferable.

A schematic structure of a direct oxidation fuel cell system according to an embodiment of the present invention is shown in FIG. 1. Referring to Figure 1 in more detail as follows. However, although the fuel cell system of the present invention represents a system for supplying fuel to the electricity generation unit through the pump 130, the fuel cell system of the present invention is not limited to this structure, and does not use a pump, but uses a diffusion method. Of course, it can also be used in system architecture.

The direct oxidation fuel cell system 100 according to an embodiment of the present invention includes at least one electric generator 101 for generating electrical energy through an electrochemical reaction between a fuel and an oxidant, and a fuel pump to the electricity generator. And a fuel supply unit 102 for supplying fuel through the 130, and an oxidant supply unit 103 for supplying an oxidant to the electricity generating unit 101.

The electricity generating unit 101 includes a membrane-electrode assembly and a separator (bipolar plate, also referred to as a current collector, 110) located on both sides of the membrane-electrode assembly, and the outermost anode electrode side of the electricity generating unit The separator 110 is connected to the fuel supply unit 102.

The oxidant supply unit 103 is positioned on the surface of the electricity generating unit 101 that is not connected to the fuel supply unit 102. The oxidant supply unit 103 serves as a separator and supplies an oxidant such as oxygen or air to the electricity generating unit 101 through a plurality of vent holes 140.

The fuel supply unit 102 includes a fuel tank 120 for storing fuel, and a fuel pump 130 connected to the fuel tank. The fuel supply unit 102 is connected to the electricity generating unit 101 and is driven by a driving force of the pump. Fuel may be supplied to the electricity generating unit 101.

In addition, the membrane-electrode assembly in the electricity generating unit includes an anode electrode and a cathode electrode located opposite each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode.

More specifically, at least one of the anode electrode and the cathode electrode in the membrane-electrode assembly includes an electrode substrate and a catalyst layer.

The electrode substrate serves to support the fuel cell electrode while spreading the fuel and the oxidant to the catalyst layer so that the fuel and the oxidant can easily access the catalyst layer. The electrode substrate is a conductive substrate, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous film or polymer fiber composed of metal cloth in a fibrous state). The metal film is formed on the surface of the cloth formed with)) may be used, but is not limited thereto.

In addition, it is preferable to use a water-repellent treatment with a fluorine-based resin as the electrode base material, since it is possible to prevent the reactant diffusion efficiency from being lowered by the electrochemically generated water in the catalyst layer of the cathode when the fuel cell is driven. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene or copolymers thereof can be used.

A catalyst layer is formed on the electrode substrate.

The catalyst layer catalyzes the associated reaction (oxidation of fuel and reduction of oxidant) and includes a catalyst.

As the catalyst, any one that can be used as a catalyst may participate in the reaction of the fuel cell, and as a representative example, a platinum-based catalyst may be used. Platinum-based catalysts include platinum, ruthenium, osmium, platinum-ruthenium alloys, platinum-osmium alloys, platinum-palladium alloys, and platinum-M alloys (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni). , A transition metal selected from the group consisting of Cu, Zn, Sn, Mo, W, Rh, and combinations thereof), and mixtures thereof. As described above, the anode electrode and the cathode electrode may use the same material, but in order to prevent the catalyst poisoning caused by CO generated during the anode electrode reaction in the direct oxidation fuel cell, a platinum-ruthenium alloy catalyst is used as the anode. It is more preferable as an electrode catalyst. Specific examples include Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W, Pt / Ru / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, Pt / Ru / Sn / W, and mixtures thereof may be used.

In addition, such a catalyst may be used as the catalyst itself (black), or may be used on a carrier. As the carrier, carbon-based materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball, or activated carbon may be used, and alumina, silica, zirconia, Or inorganic fine particles such as titania may be used, but carbon-based materials are generally used.

 The catalyst layer may further include a binder resin for improving the adhesion of the catalyst layer and the transfer of hydrogen ions.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder resin, more preferably a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. Any polymer resin can be used. Preferably, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether A hydrogen ion conductive polymer selected from the group consisting of ether ketone polymers, polyphenylquinoxaline polymers, copolymers thereof, and mixtures thereof, more preferably poly (perfluorosulfonic acid), poly ( Perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene) -5 , 5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole), copolymers thereof and mixtures thereof Line in county made up Which may be the hydrogen-ion conductive polymer.

 The binder resin may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to adjust the usage-amount so that it may be suitable for a purpose of use.

 Examples of the non-conductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), ethylene / tetrafluoro Ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoro propylene (PVdF-HFP), dode More preferably, they are selected from the group consisting of silbenzenesulfonic acid, sorbitol, copolymers thereof and mixtures thereof.

In addition, the membrane-electrode assembly according to the present invention may further be formed with a microporous layer (not shown) to enhance the diffusion effect of the reactants on the electrode substrate. These microporous layers are generally conductive powders having a small particle diameter, such as carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotubes, carbon nanowires, and carbon nanohorns. -horn or carbon nano ring, and the like.

 The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, and the like may be preferably used. The solvent may be ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or the like. Alcohol, water, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and the like can be preferably used. The coating process may be a screen printing method, a spray coating method or a coating method using a doctor blade or the like depending on the viscosity of the composition, but is not limited thereto.

In addition, the membrane-electrode assembly including the electrode includes a polymer electrolyte membrane positioned between the anode and the cathode electrode.

It is preferable to use a polymer having excellent hydrogen ion conductivity as the polymer electrolyte membrane. Representative examples thereof may be any polymer resin having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups and derivatives thereof in the side chain. Preferably, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether Ether ketone polymers, polyphenylquinoxaline polymers, copolymers thereof, and mixtures thereof, and more preferably poly (perfluorosulfonic acid) (generally Nafion). Commercially available), poly (perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m -Phenylene) -5,5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole), their air Group consisting of coalescing and mixtures thereof Can be selected from.

It is also possible to substitute H with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger of such a hydrogen ion conductive polymer. In the cation exchanger at the side chain terminal, when Na is replaced with Na, tetrabutylammonium hydroxide is used when tetrabutylammonium is used, and K, Li or Cs may be substituted with an appropriate compound. Can be. Since this substitution method is well known in the art, detailed description thereof will be omitted.

When driving the direct oxidation fuel cell according to the embodiment of the present invention having the structure as described above, the oxidant is supplied from the oxidant supply unit to the cathode electrode of the electricity generation unit, and the anode electrode of the electricity generation unit through the fuel pump from the fuel supply unit Is supplied with fuel. As such, electricity is generated by an electrochemical reaction induced from the fuel and the oxidant supplied to the cathode electrode and the anode electrode of the electricity generating unit.

In this case, when the ratio of the actual fuel supply to the theoretical fuel supply is stoichiometry, the direct oxidation fuel cell is preferably operated under the condition of supplying fuel at the stoichiometry of 3 to 10. Preferably, the fuel pump is preferably operated under conditions of supplying fuel with stoichiometry of 3 to 6.

In addition, the direct oxidation fuel cell is preferably driven in a temperature range of room temperature to 50 ℃, more preferably in a temperature range of 30 to 50 ℃.

In this case, the fuel may be a gaseous or liquid hydrocarbon fuel, and examples thereof include methanol, ethanol, propanol, butanol or natural gas. More preferably, methanol can be used. The fuel is preferably used at a concentration of 1 to 10M, more preferably at a concentration of 2M to 5M. If the concentration of the fuel is less than 1M, the concentration is low, which is not preferable for fuel supply. If the concentration of the fuel is more than 10M, the methanol crossover increases and the output decreases rapidly, which is not preferable.

By driving the direct oxidation fuel cell by the above driving method, it is possible to facilitate the emission of CO ₂ to prevent the problem of output reduction with time in the direct oxidation fuel cell, thereby improving the life characteristics of the fuel cell. there was. This effect can be maximized in passive type direct oxidation fuel cells.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited by the following examples.

(Reference example)

A catalyst composition for the cathode electrode was prepared using 88 wt% of a Pt / C catalyst as a cathode electrode and 12 wt% of Nafion / H ₂ O / 2-propanol (Solution Technology Inc.) at a concentration of 5 wt% as a binder. . A catalyst composition for the anode electrode was prepared in the same manner as above except that the PtRu / C catalyst was used.

The cathode electrode catalyst composition and the anode electrode catalyst composition were respectively applied to one surface of a commercial fuel cell polymer electrolyte membrane (Nafion 115 Membrane, manufactured by DuPont) using a spray coater to apply a cathode electrode catalyst layer and an anode electrode catalyst layer. Formed. At this time, the catalyst loading amounts in the catalyst layer of the cathode electrode and the catalyst layer of the anode electrode were 6 mg / cm ² and 1.5 mg / cm ² , respectively.

Using a gasket as a support on each side of the polymer electrolyte membrane on which the catalyst layer was formed, an ELAT electrode substrate of E-Tek was laminated, and hot rolled at 120 ° C. for 7 minutes to prepare a membrane-electrode assembly. The active area of the membrane-electrode assembly was 25 cm ² . At least one membrane-electrode assembly was stacked to manufacture an electricity generator.

A fuel supply unit including a fuel pump and a fuel tank was attached to the anode electrode side of the electricity generating unit, and the cathode electrode side was opened to manufacture a direct oxidation fuel cell.

(Example 1)

For the direct oxidation type fuel cell manufactured in the above reference example, the cathode was opened in the air at room temperature, and the oxidant was supplied in a convection type, and the test station (Test Station, manufactured by WonAtech) was used. MeOH was supplied to the anode electrode through a metering pump with a stoichiometry of 3 to drive the fuel cell.

(Example 2)

For the direct oxidation type fuel cell prepared in the reference example, the cathode electrode side was opened in the air at room temperature to supply the oxidant in a convection manner, and 3M MeOH was chemically treated using a test station (manufactured by WonAtech). On the contrary, the fuel cell was driven by feeding it toward the anode electrode through a metering pump.

(Example 3)

For the direct oxidation type fuel cell prepared in the reference example, the cathode electrode side was opened in the air at room temperature to supply the oxidant in a convection manner, and 3M MeOH of 5 was tested using a test station (test station, manufactured by WonAtech). The stoichiometry of the fuel cell was driven by feeding it to the anode electrode through a metering pump.

(Example 4)

For the direct oxidation fuel cell prepared in the reference example, the cathode electrode side was opened in the air to supply the oxidant in a convection manner, and 3M MeOH was determined by 6 stoichiometry using a test station (manufactured by WonAtech). The fuel cell was driven by feeding the pump toward the anode electrode.

(Example 5)

For the direct oxidation fuel cell manufactured in the reference example, the cathode electrode side was opened in the air at 30 ° C. in the air to supply the oxidant in a convection manner, and 1 M of MeOH was added using a test station (test station, manufactured by WonAtech). The stoichiometry of the fuel cell was driven by feeding it to the anode electrode through a metering pump.

(Example 6)

For the direct oxidation type fuel cell prepared in the reference example, the cathode was opened at 50 ° C. in the air to supply the oxidant in a convection manner, and 5 M of MeOH was added using a test station (test station, manufactured by WonAtech). The stoichiometry of the fuel cell was driven by feeding it to the anode electrode through a metering pump.

(Comparative Example 1)

For the direct oxidation type fuel cell manufactured in the reference example, the cathode electrode side was opened in the air at room temperature to supply the oxidant in a convection manner, and 3M MeOH of 1 was tested using a test station (test station, manufactured by WonAtech). The stoichiometry of the fuel cell was driven by feeding it to the anode electrode through a metering pump.

(Comparative Example 2)

For the direct oxidation fuel cell manufactured in the reference example, the cathode electrode side was opened in the air at room temperature to supply an oxidant in a convection manner, and 3M MeOH was chemically treated using a test station (manufactured by WonAtech). On the contrary, the fuel cell was driven by feeding it toward the anode electrode through a metering pump.

The voltage drop over time was measured for 30 minutes under constant voltage conditions by applying a current having a battery voltage of 0.33 V to the fuel cells of Examples 1, 2, and 4 and Comparative Examples 1 and 2. The results are shown in FIG.

In FIG. 2, the flow rate of fuel per minute of Comparative Example 2 was 0.069 ml / min, 0.104 ml / min for Example 1, and 0.138 ml / min for Example 2.

As a result, the output density of Comparative Example 1 at 0.33V was 21 mW / cm ² , 23 mW / cm ^{2 for} Comparative Example ² , 20 mW / cm ^{2 for} Example 1, 18 mW / for Example 2 In the case of cm ² , example 4, 21 mW / cm ² was shown.

As shown in FIG. 2, the fuel cells of Examples 1, 2, and 4, which are set and driven to supply fuel within the stoichiometric range of the present invention, have a significantly lower voltage drop over time than Comparative Examples 1 and 2. It was confirmed that the decrease. From this, the reduction of the output density was also significantly improved, and the life characteristics of the direct oxidation fuel cell could be expected to be improved.

The fuel densities of Examples 3, 5 and 6 were also carried out in the same manner as described above to measure the output density. As a result, the same power density as in Example 1 was shown.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

The fuel cell driving method of the present invention facilitates the emission of CO ₂ to prevent the problem of power reduction with time in the direct oxidation fuel cell, thereby improving the life characteristics of the fuel cell.

Claims (7)

A membrane-electrode assembly comprising an anode electrode and a cathode electrode positioned opposite to each other, and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode; And at least one electricity generating unit including separators disposed on both sides of the membrane electrode assembly and generating electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant. A fuel supply unit supplying fuel to the electricity generation unit through a fuel pump; And A driving method of a direct oxidation fuel cell system comprising an oxidant supply unit for supplying an oxidant to the electricity generation unit, A method of driving a direct oxidation fuel cell system comprising a step of operating under a condition of supplying fuel at a stoichiometry of 3 to 10 when the ratio of the actual fuel supply to the theoretical fuel supply is stoichiometry. The method of claim 1, And the driving method includes driving under a condition of supplying fuel at stoichiometry of 3 to 6. The method of claim 1, The driving temperature of the fuel cell is a method of driving a direct oxidation fuel cell system is a room temperature to 50 ℃. The method of claim 1, And the fuel is a gaseous or liquid hydrocarbon fuel. The method of claim 1, And the fuel is methanol. The method of claim 1, And the fuel is used at a concentration of 1 to 10M. The method of claim 1, And the fuel cell system is a passive fuel cell system.

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