JP2014036944A - Oxygen reduction device, method for operating the same, and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen reduction device capable of suppressing deterioration of the cathode catalytic layer of a cathode possessed by an oxygen-reducing cell.SOLUTION: An oxygen reduction device 21 includes an oxygen-reducing cell 22, a power source 23, and a controller 25. The oxygen-reducing cell 22 includes: a cathode 33 having a cathode catalytic layer 34; an anode 31; and an electrolyte membrane 37 sandwiched between the cathode 33 and the anode 31. The electrolyte membrane 37 has proton conductivity. The power source 23 generates a first voltage V1 and at least either of second or third voltages V2, V3 that are higher than the first voltage V1. The controller 25 applies the first voltage V1 across the cathode 33 and anode 31, and applies a voltage that is higher than the first voltage at least either before or after applying the first voltage V1.

Description

  Embodiments described herein relate generally to an oxygen reduction device for reducing the oxygen concentration, an operation method of the device, and a refrigerator including the oxygen reduction device.

  In order to improve the storage stability of foods and the like, an oxygen reduction device has been proposed in which the oxygen concentration in the storage space (deoxygenation space) is reduced by an electrochemical reaction using an electrolyte membrane.

  This apparatus includes a hypoxic cell in which a polymer electrolyte membrane having proton conductivity is sandwiched between an anode and a cathode. This cell is arranged with the cathode facing a storage space for food or the like. The oxygen reduction device is operated by applying a voltage between the anode and the cathode in a state where water can be supplied to the anode. Accordingly, water is electrolyzed at the anode and a water generation reaction is performed at the cathode, so that oxygen in the storage space can be reduced along with the water generation reaction.

  The reduction of oxygen occurring at the cathode of the oxygen reduction cell is performed by generating water as a result of the oxygen reduction reaction (hereinafter referred to as “deoxygenation reaction” in this specification). This reaction proceeds in the cathode catalyst layer of the cathode. The cathode catalyst layer includes a catalyst such as platinum and a carrier supporting the catalyst. The deterioration of the cathode catalyst layer is caused by the elution of the catalyst. As the deterioration of the cathode catalyst layer progresses, the voltage applied to the cathode becomes excessive, causing a reduction in the performance of the oxygen reduction cell and reducing the durability of the oxygen reduction device.

  In order to promote the practical use of this apparatus, it is important to suppress the deterioration of the cathode catalyst layer and ensure the durability of the oxygen reduction apparatus over a long period of time.

  On the other hand, a method for producing a catalyst capable of suppressing deterioration of the catalyst has been proposed. In this manufacturing method, first, a catalyst made of a platinum alloy supported on carbon black is heat-treated. After this, the catalyst is contacted with carbon monoxide. Finally, the catalyst is heat treated again under an inert gas atmosphere. According to this production method, the distance between the platinum and platinum atoms is stabilized to be small, and therefore a catalyst excellent in activity and durability can be produced.

  However, even this technique cannot prevent the catalyst such as platinum contained in the cathode catalyst layer from eluting due to a change in the voltage of the oxygen reduction cell accompanying a change in the current flowing through the oxygen reduction cell.

  During operation of the oxygen reduction device, the voltage (cell voltage) applied to the oxygen reduction cell changes periodically or aperiodically in accordance with the change in the current flowing through the oxygen reduction cell. Since this phenomenon involves a change in the voltage of the oxygen reduction cell, the oxidation and reduction reactions of the catalyst contained in the cathode catalyst layer are frequently repeated.

  If the catalyst using platinum or the like is maintained at a constant potential even if the cell voltage is high, the catalyst surface is stable and the catalyst is not eluted. However, when the catalyst is oxidized or reduced, the potential of the catalyst changes greatly as the voltage applied to the oxygen reduction cell changes. Thereby, the elution of the catalyst becomes remarkable and the catalyst deteriorates. As this deterioration progresses, the voltage applied to the cathode is excessively increased, and the performance of the oxygen reduction cell is lowered. This causes a decrease in durability and further increases the voltage applied to the oxygen reduction cell.

Japanese Patent Laid-Open No. 9-287869 JP 2001-52718 A

  An embodiment is to provide an oxygen reduction device capable of suppressing deterioration of a cathode catalyst layer of a cathode of an oxygen reduction cell, a method of operating the device, and a refrigerator.

  In order to solve the above-described problem, an oxygen reduction apparatus according to an embodiment includes an oxygen reduction cell, a power source, and a controller. The oxygen reduction cell includes a cathode having a cathode catalyst layer, an anode, and an electrolyte membrane sandwiched between the cathode and the anode. The electrolyte membrane has proton conductivity. The power supply generates a first voltage V1 and at least one of a second voltage V2 and a third voltage V3 that are higher than the voltage V1. The controller applies a first voltage V1 between the cathode and the anode to generate a hypoxic reaction at the cathode, and applies a voltage higher than the first voltage V1 before or after the application. It is characterized by letting.

It is a schematic sectional drawing which shows a part of refrigerator which concerns on 1st Embodiment. It is sectional drawing which shows schematically the structure of the oxygen reducing apparatus used for the refrigerator of FIG. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 2 by 1st Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 2 by 2nd Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 2 by 3rd Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 2 by 4th Embodiment. It is a time chart which shows the change of the applied voltage at the time of driving | running the oxygen reduction apparatus of FIG. 2 by 5th Embodiment. It is sectional drawing which shows schematically the structure of the other oxygen reduction apparatus used for the refrigerator of FIG. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 8 by 6th Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 8 by 7th Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 8 by 8th Embodiment. It is a flowchart which shows the procedure which operate | moves the oxygen reduction apparatus of FIG. 8 by 9th Embodiment. It is a time chart which shows the change of the applied voltage at the time of driving | running the oxygen reduction apparatus of FIG. 8 by 10th Embodiment.

  Hereinafter, the oxygen reduction device 21 according to the first embodiment, the operation method thereof, and the storage, for example, the refrigerator 1 including the oxygen reduction device 21 will be described in detail with reference to FIGS. 1 to 3.

  First, the refrigerator 1 is demonstrated with reference to FIG. The refrigerator 1 includes a refrigerator body 2 made of a heat insulating box. The refrigerator body 2 has a refrigerating chamber at an upper portion (not shown), and has a hypoxic chamber 3 at the lower portion of the refrigerator body 2.

  The oxygen-reducing chamber 3 is provided for preserving articles to be stored such as vegetables accommodated therein in a low temperature and low oxygen environment for a long period of time. The oxygen-reducing chamber 3 is partitioned by an oxygen-reducing box 4 that forms a part of the wall of the refrigerator body 2 and whose outer surface is covered with a heat insulating material, and is not communicated with a refrigerator room or the like. The oxygen reduction box 4 is opened on the front surface of the refrigerator body 2. This opening is opened and closed by the opening / closing member 5.

  A refrigerant pipe (not shown) is provided on the outer surface of the oxygen reduction box 4. For this reason, the oxygen reduction box 4 is cooled by the refrigerant | coolant which distribute | circulates refrigerant | coolant piping to the temperature suitable for refrigeration of a foodstuff. Thereby, it is possible to refrigerate food stored in the oxygen reduction chamber 3 formed of the internal space of the oxygen reduction box 4.

  The opening / closing member 5 has a configuration in which a heat insulating material is filled therein, and also serves as a front wall of the storage container 6 whose upper surface is opened, for example. The storage container 6 is movable in the front-rear direction with respect to the oxygen reduction chamber 3. Vegetables etc. can be taken in and out through the opened upper surface in a state where the container 6 is pulled out to the front side.

  In order to move the container 6 smoothly, a rail 7, a fixed roller 8, and a movable roller 9 are used. The rails 7 are arranged in the oxygen reduction chamber 3 at two positions on the left and right sides in the width direction of the oxygen reduction chamber 3 and extend in the front-rear direction. A fixed roller 8 that contacts the container 6 from below is fixed to the front end of each rail 7. The movable roller 9 is fixed to the lower surface of the rear end of the container 6 and can roll on the rail 7.

  Therefore, the container 6 can move in the front-rear direction with the rotation of these rollers while being supported by the fixed roller 8 and the movable roller 9 from below.

  An annular seal packing 10 is attached to the periphery of the opening / closing member 5. With the opening / closing member 5 closing the front opening of the oxygen reduction box 4, the seal packing 10 is brought into close contact with the front surface of the refrigerator main body 2 to keep the oxygen reduction chamber 3 sealed. The opening / closing member 5 may be a heat insulating door attached to the front surface of the refrigerator main body 2 so as to be rotatable by a hinge. For this reason, the container 6 may be pivotally attached.

  A freezer compartment 13 divided into upper and lower stages is formed in the lowermost part of the refrigerator main body 2 independently of the oxygen reduction chamber 3. The front opening of the freezer compartment 13 is opened and closed by a heat-insulating door 14. A machine room 15 is formed on the back side of the refrigerator body 2 and at the lower end. A compressor 16 is installed in the machine room 15. In the refrigerator body 2, a cooler 17 and a fan 18 to which a refrigerant is supplied by a compressor 16 are disposed, and a cover 19 that covers these from the front side is disposed. Cold air generated by the cooler 17 and the fan 18 is circulated to the freezer compartment 13.

  The refrigerant flowing out of the cooler 17 is sucked into the compressor 16 via the refrigerant pipe (not shown) attached to the outer surface of the oxygen reduction box 4.

  Next, the oxygen reduction device 21 will be described with reference to FIG. The oxygen reduction device 21 includes an oxygen reduction cell 22, a power source 23, current measuring means such as an ammeter 24, and a controller 25. The oxygen reduction cell 22 is not limited to one, and a plurality of oxygen reduction cells 22 may be provided.

  The oxygen reduction cell 22 includes an anode 31, a cathode 33, and an electrolyte membrane 37.

  The anode 31 electrolyzes the water for electrolysis supplied thereto. The water for electrolysis is not limited to water but includes an acidic aqueous solution.

  The cathode 33 is formed by bonding a cathode catalyst layer 34, a conductive porous layer (MPL) 35, and a gas diffusion layer (GDL) 36.

  The cathode catalyst layer 34 is formed in a sheet shape and joined to the porous layer 35. The gas diffusion layer 36 is formed in a sheet shape from a conductive material having air permeability or liquid permeability. The gas diffusion layer 36 is bonded to the conductive porous layer 35, and the porous layer 35 is sandwiched between the cathode catalyst layer 34.

  A polymer electrolyte membrane can be suitably used for the electrolyte membrane 37. An anode 31 is bonded to one side surface of the electrolyte membrane 37. The cathode 33 is bonded to the other side of the electrolyte membrane 37 with the cathode catalyst layer 34 in contact therewith. Therefore, the electrolyte membrane 37 is sandwiched between the anode 31 and the cathode 33.

  An anode current collector 38 is in intimate contact with the outer surface of the anode 31, that is, the side surface not in contact with the electrolyte membrane 37. Similarly, the cathode current collector 39 is in close contact with the outer surface of the cathode 33, that is, the side surface of the gas diffusion layer 36 that is not in contact with the porous layer 35. The anode current collector 38 and the cathode current collector 39 are electrically connected to the power source 23.

  The oxygen reduction cell 22 having the above-described configuration is sandwiched between a first fastening member 41 and a second fastening member 45 made of an electrical insulating material. The first fastening member 41 and the second fastening member 45 are connected. The first fastening member 41 and the second fastening member 45 fasten the oxygen-reducing cell 22 along their stacking direction. Thereby, the closeness at each joint surface is ensured.

  An anode chamber 42 is formed between the first fastening member 41 and the anode 31. A cathode chamber 46 is formed between the second fastening member 45 and the cathode 33.

  The first fastening member 41 has a water intake port 43 and an oxygen outlet 44 that communicate with the anode chamber 42. The water intake 43 is provided at the lower end of the first fastening member 41 and introduces electrolysis water such as water into the anode chamber 42. The oxygen outlet 44 is provided at the upper end portion of the first fastening member 41 and guides oxygen generated by the electrolysis reaction at the anode 31 from the anode chamber 42 to the outside.

  The second fastening member 45 has an air intake 47 and a drain 48 that communicate with the cathode chamber 46. A plurality of air intake ports 47 are provided on the side wall of the second fastening member 45 facing the cathode 33, and introduces air (oxygen) used for the oxygen reduction reaction into the cathode chamber 46. The drain port 48 is provided at the lower end portion of the second fastening member 45, and guides water generated by the oxygen reduction reaction from the cathode chamber 46 to the outside.

  Next, each member constituting the oxygen reduction cell 22 will be described in more detail.

The anode 31 contains a catalyst (anode catalyst) having the ability to electrolyze water. Examples of the anode catalyst include electrically conductive noble metal oxides such as ruthenium oxide (RuO ₂ ) and iridium oxide (IrO ₂ ), titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), and tantalum oxide (Ta ₂ O _5). ), And the like. However, the present invention is not limited to these, and the anode catalyst may be selected in consideration of its activity, durability, cost, and the like. As other anode catalysts, RuO ₂ -TiO ₂ , RuO ₂ -IrO ₂ , RuO ₂ -IrO ₂ -TiO ₂ , RuO ₂ -SnO ₂ , RuO ₂ -Ta ₂ O ₅ , IrO ₂ -Ta ₂ O ₅ etc. Can be mentioned.

  The base material supporting the anode catalyst is selected in consideration of electrical conductivity, electrochemical stability, adhesion to the anode catalyst, and the like. For example, as the base material, an expanded metal such as titanium or a punching metal having a track record of use in the field of the electrolytic industry can be used. An anode having such a substrate has a titanium surface coated with a complex oxide thin film, and an electrode (anode) having such a structure is called a dimensionally stable (DSA) electrode.

  The anode 31 is manufactured by a known method such as a coating method, a dipping method, or a spray method. An example of specific production will be described below. This manufacturing example has a dipping process, a drying process, and a firing process, and the anode 31 is manufactured by repeating these processes a plurality of times.

In the dipping process, titanium base metal (thickness: 500 μm, porosity: 30%) is immersed for 1 hour in an 80% 10% oxalic acid aqueous solution to roughen and activate the surface. Thereafter, the substrate is washed, and the substrate is immersed in a butanol solution of iridium chloride and tantalum chloride (Ir: Ta = 0.3: 0.7 mol ratio). In the next drying step, the substrate obtained through the dipping step is dried in air at 60 ° C. for 10 minutes. In the final firing step, the substrate obtained through the drying step is fired in air at 450 ° C. for 10 minutes. Each of these steps is repeated multiple times. Thereby, the anode 31 was manufactured so that the composite oxide of iridium oxide-tantalum oxide was 0.01 mg / cm ^{2 on} the titanium mesh surface. The catalyst loading was determined from the change in weight of the titanium mesh.

  As described above, the cathode 33 includes the cathode catalyst layer 34, a conductive porous layer (MPL) 35, and a gas diffusion layer (GDL) 36.

  The cathode catalyst layer 34 only needs to contain a noble metal catalyst having an ability to reduce oxygen. Although it does not restrict | limit especially as a noble metal catalyst, For example, what consists of at least 1 type of noble metal selected from the group which consists of platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), and iridium (Ir) Is preferred.

  Furthermore, in order to improve the dissolution resistance, activity, etc. of the catalyst, noble metal alloy particles may be used as the catalyst component. The noble metal alloy particles are not particularly limited, and examples thereof include alloys composed of two or more kinds of noble metal elements, alloys containing noble metal elements and other metal elements, and the like.

  Since the noble metal alloy particles have high catalytic activity, a noble metal alloy catalyst based on Pt is preferable.

  Specific examples of noble metal alloy catalysts include noble metals other than Pt such as Ru, Rh, Pd, and Ir, titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), and cobalt. An alloy of one or more metal elements selected from the group consisting of (Co) and nickel (Ni) and Pt is preferable.

  Although the alloy composition of the noble metal alloy particles depends on the type of metal element to be alloyed, Pt is preferably 30 to 95 atomic%, and the metal element to be alloyed is preferably 5 to 70 atomic%.

  Here, the alloy is a generic name for a plurality of metal elements or those having metallic properties composed of metal elements and non-metal elements. Alloys include solid solutions that are completely dissolved, eutectics in which the metal elements of the components are independent at the crystal level, and intermetallic compounds that are bonded at a certain ratio at the atomic level, but are limited to any of these. It is not a thing.

  The conductive carrier supporting at least one of the noble metal particles or the noble metal alloy particles may be selected in consideration of electrical conductivity, gas diffusibility, adhesion with a catalyst, and the like. For example, carbon black, activated carbon, and graphite can be used as the conductive carrier. Examples of carbon black include furnace black, channel black, acetylene black, Vulcan (registered trademark of Cabot Corporation), and ketjen black. Furthermore, for example, a nanocarbon material such as a fiber shape, a tube shape, or a coil shape may be used as the conductive carrier.

The specific surface area of the conductive support may be a sufficient catalyst to cause a highly dispersed supported, for ^example, a 50m ² / g~1400m 2 / g. If the specific surface area is too small, that is, if it is less than 50 m ² / g, the dispersibility of the catalyst component on the conductive support may be lowered, and sufficient performance may not be obtained. On the other hand, if the specific surface area is too large, that is, if it exceeds 1400 m ² / g, the effective utilization rate of the catalyst component may decrease. Therefore, it was set as the said range. Preferred specific surface area was ^{80m 2} / ^g~1200m 2 / g, more preferably from 100m ² / g~1000m ² / g.

  In a cathode catalyst in which at least one of noble metal particles or noble metal alloy particles is supported on a conductive support, when both noble metal particles and noble metal alloy particles are used as a catalyst component, the noble metal particles and the noble metal alloy particles are the same conductive material. It may be carried on a different conductive material.

  In the cathode catalyst in which at least one of noble metal particles or noble metal alloy particles is supported on the conductive material of the catalyst composition, the supported amount of metal components such as noble metal particles or noble metal alloy particles is based on the total amount of the oxygen reduction catalyst. It is preferable that it is 10 mass%-90 mass%. If the supported amount of the metal component is too small, that is, if it is less than 10% by mass, the catalyst activity per unit mass is reduced and a large amount of catalyst is required to obtain the desired performance. This is not preferable because the diffusibility of the reactant decreases. On the other hand, if the amount of the metal component supported is too large, that is, if it exceeds 90% by mass, the degree of dispersion of the catalyst component on the conductive material will decrease, and the performance will be small and economical for the amount supported. There is a possibility that the advantage in the case is reduced. Therefore, the carrying amount is in the above range. A preferable loading is 20% by mass to 80% by mass, and more preferably 30% by mass to 70% by mass.

  The cathode catalyst can be produced using a solution method such as an impregnation method, a precipitation method, or a colloid method. When the catalyst particles are nano-particles, the highest activity can be obtained. The average particle size of the catalyst particles is desirably 10 nm or less. This is because if the average particle diameter of the catalyst particles exceeds 10 nm, the activity efficiency of the catalyst may be significantly reduced. A more preferable range of the average particle diameter of the catalyst particles is 0.5 nm to 10 nm. This is because if the thickness is less than 0.5 nm, it is difficult to control the catalyst synthesis process and the catalyst production cost increases. As the catalyst particles, fine particles having an average particle diameter of 10 nm or less may be used alone, but aggregates (secondary particles) of primary particles made of the fine particles may be used.

  The crystal structure of the cathode catalyst can be confirmed by assigning a diffraction peak in X-ray diffraction analysis (XRD). For example, RINT1200 manufactured by Rigaku can be used for an X-ray diffraction analysis (XRD) apparatus.

  The sample can also be evaluated by a powder sample obtained by cutting out a part of a catalyst layer used for a synthesized catalyst or a cathode of a battery.

  The analysis sample was pulverized in an agate mortar and used a powder that passed through a 45 μm sieve. In the measurement, a glass sample plate (size of sample portion: length 20 mm × width 20 mm × depth 0.2 mm) was filled with a glass plate so that the analysis sample was smooth with the surface of the sample plate.

The measurement conditions are as follows. For details on other measurement methods, refer to “Guidelines for X-ray diffraction (revised third edition)” issued by Rigaku Denki Co., Ltd.
Tube: Cu
Tube voltage: 40 kV
Tube current: 40 mA
Divergence slit: 1 deg
Scattering slit: 1 deg
Receiving slit: 0.30mm
Sampling angle: 0.020 deg
Scan speed: 2 deg / min
The average particle diameter of the catalyst component can be calculated from the crystallite diameter obtained from the half width of the strongest diffraction peak of the catalyst component in X-ray diffraction analysis (XRD). The Scherrer equation was used for the calculation.

  When taking out the catalyst from the sample, the cross-sectional portion of the substantially central portion of the surface having the maximum surface area of the product is used as the sample.

  As a specific example of the method for producing the cathode catalyst, for example, acetylene black is dispersed in an aqueous solution in which chloroplatinic acid is dissolved, and sodium hydrogen carbonate is dropped therein to adjust the pH of the solution to 7 to 8, Pt oxide was supported on acetylene black. The solid content was separated from the solution by filtration, washed with an aqueous sulfuric acid solution, and then dried at 60 ° C. (in the air). The obtained solid was pulverized and reduced with hydrogen gas to support Pt on acetylene black. The amount of Pt supported was 10% by mass.

  The composition analysis of the noble metal catalyst contained in the cathode catalyst layer 34 can be evaluated by inductively coupled plasma emission spectroscopy (ICP). The analysis sample can be evaluated by a powder sample obtained by shaving a part of the catalyst layer used for the electrode catalyst or the cathode of the battery.

There are several methods for the pretreatment (solution) of the analysis sample, and these can be used in appropriate combination according to the element used for the catalyst. For example, in the case of an acid dissolution method, concentrated hydrochloric acid that forms a complex with many elements to assist dissolution, nitric acid having strong oxidizing power, hot concentrated sulfuric acid capable of high-temperature heat decomposition, and the like can be used. Further, when it is difficult to dissolve with a single acid, a mixed acid obtained by combining these acids may be used. When acid decomposition is difficult, there is an alkali melting method with strong dissolving power due to high-temperature melting. Decomposing agents include sodium carbonate (Na ₂ CO ₃ ), sodium peroxide (Na ₂ O ₂ ), sodium hydroxide and sodium nitrate. A mixture of (NaOH + NaNO ₃ ) can be used.

  The cathode catalyst layer 34 in the cathode 33 is a porous layer formed of a cathode catalyst and a proton conductive binder. The proton conductive binder is used to immobilize the cathode catalyst, and a perfluorosulfonic acid polymer (for example, product name: Nafion manufactured by DuPont) is selected.

  It is desirable that the cathode catalyst layer 34 has a catalyst layer structure that maintains a high proton conductivity and conductivity while maintaining a porous property that facilitates material diffusion. For this reason, the mixing ratio of the catalyst-supporting carbon and the proton conductive binder is such that the weight ratio (P / C) of the proton conductive binder (P) is 0.05 to 0.5 with respect to the total weight (C) of the catalyst layer. A range is desirable. If the weight ratio P / C is larger than 0.5, the continuity of the catalyst-carrying carbon may be lowered and the conductivity may be lowered.

  The cathode catalyst layer 34 is formed immediately above a conductive porous layer (MPL) 35 laminated on a gas diffusion layer (GDL) 36. As the GDL with MPL, a commercially available product can be appropriately selected and used.

  The gas diffusion layer 36 is a sheet made of a material having air permeability or liquid permeability, such as carbon paper, carbon cloth, carbon felt, etc., which has been appropriately given water repellency by a water repellent, and has conductivity. The conductive porous layer (MPL) 35 is a porous layer made of a water repellent and carbon particles.

  As the water repellent used for the gas diffusion layer 36 and the conductive porous layer 35, a fluororesin is selected. For example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin (PFA), etc. can be generally used.

  As the carbon particles used for the conductive porous layer 35, the same carbon particles as those described above can be used.

  The cathode catalyst layer 34 can be produced, for example, by the following method. First, a cathode catalyst and a proton conductive binder are mixed and dispersed in an organic solvent such as water or alcohol to form a catalyst slurry. Next, this slurry is applied to the gas diffusion layer 36 and dried. Thereby, the cathode catalyst layer 34 is formed. The dispersion method is not particularly limited, and examples thereof include a dissolver, a ball mill, and a homogenizer.

  As a specific manufacturing method of the cathode 33, for example, 5 g of water, 8 g of 1-propanol, 8 g of 2-propanol, and 2 g of ethylene glycol were weighed and mixed with 1 g of Pt / C obtained above, and zirconia balls were used. Mix for 1 hour on a ball mill. The obtained catalyst slurry was applied to the MPL surface of the GDL with MPL, dried at 60 ° C. in the air, and then washed with 1% hydrogen peroxide for 1 hour to prepare the cathode 33.

  The polymer electrolyte membrane 37 is preferably a thin film made of a perfluorocarbon sulfonic acid polymer because of its high proton conductivity. Examples of the electrolyte membrane 37 include fluororesins having a sulfonic acid group such as Nafion (trade name: manufactured by DuPont), Flemion (trade name: manufactured by Asahi Kasei Co., Ltd.), Aciplex (trade name: manufactured by Asahi Glass Co., Ltd.), and the like. Can be mentioned. However, it is not limited to these, The electrolyte membrane 37 should just be a thin film which consists of an organic polymer material which has a sulfonic acid group. The film thickness of the polymer electrolyte membrane 37 is preferably 10 μm to 150 μm in consideration of membrane resistance. A more preferable film thickness is 30 μm to 100 μm.

  The polymer electrolyte membrane 37 can reduce the amount of water that passes through the membrane without impairing proton conductivity by being subjected to the electron beam irradiation treatment. When the electron beam is irradiated onto the electrolyte membrane 37, the polymer on the surface of the electrolyte membrane 37 is cleaved from the ether bond portion of the hydrophilic side chain and the sulfonic acid group at the end of the side chain, and carboxylic acid is generated instead. Infrared spectroscopy revealed. As a result, it is considered that the hydrophilic cluster size on the surface of the electrolyte membrane 37 was reduced and the water permeation amount was reduced without impairing proton conductivity.

If the irradiation process is excessively performed to change the membrane structure, proton conductivity is impaired, leading to an increase in membrane resistance. Therefore, it is desirable that the conditions for the electron beam irradiation treatment are an electron acceleration voltage of 25 kV to 100 kV and an irradiation dose of 3 μC / cm ^{2 to 20} μC / cm ² . If the acceleration voltage is less than 25 kV, the effect of the electron beam treatment is small, and the effect of suppressing water permeation cannot be obtained sufficiently. Therefore, the flooding reduction effect at the cathode 33 is small. On the other hand, when the acceleration voltage is higher than 100 kV, the film structure is strongly changed and the film resistance is increased, so that the electrolytic performance is deteriorated. Similarly, if the irradiation dose is smaller than 3 μC / cm ^2, the effect of the electron beam treatment is small, and the effect of suppressing water permeation cannot be obtained sufficiently, so the effect of reducing flooding at the cathode is small. On the other hand, if the irradiation dose is higher than 20 μC / cm ² , the film structure is strongly changed and the film resistance is increased, so that the electrolysis performance is lowered. A commercially available apparatus can be used for the electron beam treatment. Examples of the electron beam processing apparatus that can be used include a single-lamp decompression type irradiator (manufactured by USHIO), but may be selected in consideration of the manufacturing process, cost, etc., and is limited to the irradiator. It is not a thing.

The anode 31 and the cathode 33 and the polymer electrolyte membrane 37 can be joined using a device capable of at least one of heating and pressurization. Generally, joining is performed by a hot press machine. The press temperature in that case should just be more than the glass transition temperature of the proton-conductive polymer used as a binder, and is generally 100 degreeC-400 degreeC. The pressing pressure depends on the hardness of the electrode used, but is ^{usually, 5kg / cm 2 ~200kg / cm} 2.

  The oxygen reduction cell 22 is disposed in the refrigerator main body 2 so that it can react with oxygen in the oxygen reduction chamber 3. Specifically, a hollow cell holder 20 (see FIG. 1) is attached to, for example, a rear wall of the oxygen reduction box 4 so as to cover a communication port (not shown) formed in the rear wall. The inside of the cell holder 20 and the oxygen reduction chamber 3 are communicated with each other via the communication port. An oxygen reduction cell 22 is fixed to the rear wall of the cell holder 20. The second fastening member 45 and the cathode 33 of the fixed oxygen-reducing cell 22 face the cell holder 20. Therefore, the cathode 33 of the oxygen reduction cell 22 communicates with the oxygen reduction chamber 3 via the internal space of the cell holder 20 and is arranged so that it can react with oxygen in the oxygen reduction chamber 3.

  The anode current collector 38 of the oxygen reduction cell 22 is electrically connected to the positive electrode of the power source 23, and the cathode current collector 39 of the oxygen reduction cell 22 is electrically connected to the negative electrode of the power source 23. Thereby, the voltage of the power source 23 can be applied between the anode 31 and the cathode 33 of the oxygen reduction cell 22.

  The power supply 23 generates a first voltage V1 and a second voltage V2 having predetermined values. The second voltage V2 is higher than the first voltage V1.

  The oxygen reduction device 21 of the first embodiment is operated with the first voltage V1 applied to the oxygen reduction cell 22 kept constant during the steady operation. The advantages of operating the oxygen reduction cell 22 at a constant voltage in this way will be described below.

  First, since the voltage (cell voltage) applied to the oxygen reduction cell 22 is constant, it is easy to perform electrical control. Second, hydrogen generation from the cathode 33 can be suppressed. Specifically, during the operation of the oxygen reduction cell 22, as will be described later, the oxygen reduction reaction (water generation reaction) is formed at the cathode 33, so that a part of the generated water covers the cathode catalyst layer 34. And hinders gas diffusibility at the cathode 33. Such a phenomenon is called a flooding phenomenon. When the oxygen-reducing cell 22 is steadily operated at a constant current, the cell voltage increases as the flooding phenomenon progresses. Therefore, a hydrogen production reaction occurs instead of the hypoxic reaction. However, by operating the oxygen-reducing cell 22 while keeping the voltage constant, the cell voltage does not increase regardless of the flooding phenomenon. For this reason, generation of hydrogen from the cathode 33 can be suppressed.

  The ammeter 24 measures the current (cell current) flowing through the oxygen reduction cell 22. The measurement information of the ammeter 24 is supplied to the controller 25 as an electrical signal.

  The voltage (cell voltage) applied to the oxygen reduction cell 22 is not the voltage of the power source 23 but the voltage corresponding to the current measured by the ammeter 24. The power supply voltage and the cell voltage do not always match due to the effect of the ohmic loss of the electrical cables used to electrically connect the oxygen reduction cell 22 and the power supply 23. By using the ammeter 24 as a countermeasure against this, it is possible to know the cell voltage from which the influence of the ohmic loss is eliminated.

  Next, a reaction for reducing oxygen in the oxygen reduction chamber 3 (oxygen reduction reaction) will be described.

  In a state where water is supplied from the water intake 43 to the anode chamber 42, a DC voltage is applied from the power source 23 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 under the control of the controller 25, and the oxygen reduction cell 22. To drive.

  As a result, water is electrolyzed on the surface of the anode 31 and water is generated on the surface of the cathode 33.

That is, oxygen (O ₂ ), protons (H ⁺ ), and electrons (e ⁻ ) are generated by the electrolysis reaction of water. The generated oxygen (O ₂ ) is discharged out of the anode chamber 42 through the oxygen outlet 44. On the other hand, the generated proton (H ⁺ ) moves to the cathode 33 through the anode 31 and the electrolyte membrane 37. At the same time, the generated electrons (e ⁻ ) move to the cathode 33 through an external circuit including the power source 23 and the like.

Oxygen (O ₂ ) in the oxygen-reducing chamber 3 is supplied to the cathode chamber 46 through the air intake 47, so that oxygen (O ₂ ) in the oxygen-reducing chamber 3 and the cathode 33 are supplied at the cathode 33. Protons (H ⁺ ) and electrons (e ⁻ ) react to produce water. Along with this, the oxygen concentration in the oxygen reduction chamber 3 decreases. Thereby, it is possible to preserve | save the preservation | save object accommodated in the oxygen reduction chamber 3 hold | maintained at the temperature lower than the outside of a store | warehouse | chamber, for example, vegetables, keeping freshness over a long time.

  The controller 25 monitors the cell current flowing through the oxygen reduction cell 22 based on the measurement information of the ammeter 24, and the first voltage V1 and the second voltage V2 generated by the power source 23 according to the flowchart shown in FIG. Is applied to the oxygen-reducing cell 22. Thereby, the oxygen concentration in the oxygen-reducing chamber 3 can be lowered.

  The oxygen reduction operation of the oxygen reduction cell 22 is started by first executing step S1 in which the second voltage V2 is applied for a predetermined time. Next, step S2 for applying the first voltage V1 is executed, and the oxygen reduction operation is continued. Finally, step S3 for stopping the application of voltage to the oxygen reduction cell 22 at a predetermined time is executed, and the oxygen reduction operation is terminated.

  In such control, the second voltage V2 applied to the oxygen reduction cell 22 before the application of the first voltage V1 is higher than the first voltage V1. At the same time, the application time of the second voltage V2 is shorter than the application time of the first voltage V1, and may be, for example, not less than 1 minute and not more than 10 minutes, and is preferably set to 4 to 6 minutes. This is because if the application time of the second voltage V2 is less than 1 minute, the oxidized catalyst of the cathode 33 cannot be sufficiently reduced, and if the application time of the second voltage V2 exceeds 10 minutes, This is because the deterioration of the oxygen reduction cell 22 is promoted by the second voltage V2 higher than the first voltage V1.

  The cathode catalyst layer 34 containing a cathode catalyst such as platinum in the oxygen reduction cell 22 may be oxidized along with potential fluctuations during operation of the oxygen reduction cell 22. Further, when the operation of the oxygen reduction cell 22 is stopped, the cathode 33 may be exposed to a high potential due to oxygen remaining in the cathode 33 and a part of the cathode catalyst layer 34 may be oxidized. When at least a part of the cathode catalyst layer 34 is oxidized, the cathode catalyst such as platinum is easily eluted.

  When the oxygen reduction cell 22 in this state is operated next, the cell voltage is controlled according to the flowchart of FIG. 3 as described above, so that the potential of the cathode 33 is changed from the second voltage V2 to the first voltage. Decreasing in response to falling to V1. Accordingly, reduction of the cathode catalyst such as platinum is promoted, so that deterioration due to elution of the cathode catalyst is suppressed and the cathode 33 is activated. The application time of the second voltage V2 is preferably just before the application of the first voltage V1.

  Subsequent to the reduction of the cathode catalyst layer 34, the first voltage V1 is applied to the oxygen reduction cell 22 to shift to a steady oxygen reduction operation. This operation is performed for a time longer than the application time of the second voltage V2. As a result, when the oxygen concentration in the oxygen reduction chamber 3 is lowered to a predetermined value, step S3 is executed, and the oxygen reduction operation is completed.

(Example 1)
In Example 1, the anode 31 of the area of 20 cm ^2, the area is a cathode 33 of 12cm ^2, and create a reduced oxygen cell 22 by joining the electrolyte membrane 37 of the polymer by hot pressing. Hot pressing was performed under the conditions of a temperature of 150 ° C., a pressing pressure of 40 kg / cm ² , and a pressing time of 3 minutes. The test was performed by sandwiching the oxygen-reducing cell 22 produced as described above between the first fastening member 41 and the second fastening member 45 shown in FIG.

  In this test, the anode chamber 42 was filled with water, and air was supplied to the cathode chamber 46 at 120 mL / min. An electronic load device (not shown), a power source 23, and an ammeter 24 were connected to the anode current collector 38 and the cathode current collector 39. In this state, the controller 25 applied a voltage of 1.2 V as the second voltage V2 for 5 minutes before applying the first voltage V1 of 1.0 V to the oxygen reduction cell 22. Thereafter, the oxygen reduction operation was continued at a constant voltage of 1.0 V, and current values were measured 1 hour and 1000 hours after this point.

(Comparative Example 1)
The oxygen reducing element was produced in the same manner as in Example 1. The test was performed by sandwiching the oxygen-reducing cell 22 produced as described above between the first fastening member 41 and the second fastening member 45 shown in FIG. In this case, the anode chamber 42 was filled with water, and air was supplied to the cathode chamber 46 at 120 mL / min. An electronic load device (not shown), a power source, and an ammeter 24 are connected to the anode current collector 38 and the cathode current collector 39, and the oxygen reduction operation is started at a constant voltage of 1.0 V. One hour after the start The current value after 1000 hours was measured. The results are shown in Table 1.

  As shown in Table 1, by applying the second voltage V2 of 1.2V for 5 minutes before applying the first voltage V1 of 1.0V, the cell current value after 1 hour from the start of the reaction of the oxygen reduction cell 22, and It was confirmed that both of the electrolytic current values after 1000 hours showed a higher cell current than that of Comparative Example 1.

  FIG. 4 shows a second embodiment. The second embodiment is different from the first embodiment in the control procedure described below, and is otherwise the same as the first embodiment. For this reason, configurations having the same or similar functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Together with this, FIG. 1 and FIG. 2 are also referred to as necessary.

  In the second embodiment, the power source 23 generates the first voltage V1 and the third voltage V3 having predetermined values. The third voltage V3 is higher than the first voltage V1. These voltages are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 according to the flowchart shown in FIG.

  First, step S2 in which the first voltage V1 is applied to the oxygen reduction cell 22 is executed for the oxygen reduction cell 22, and a steady oxygen reduction operation is started. Step S4 is executed when the oxygen concentration in the oxygen reduction chamber 3 has decreased to a predetermined value due to continued operation for a long time in step S2, and the third voltage V3 is applied to the oxygen reduction cell 22 for a predetermined time. Continue oxygen operation. Then, step S3 is performed and the application of the voltage with respect to the oxygen reduction cell 22 is stopped, and an oxygen reduction operation is complete | finished.

  The oxygen reduction device 21 of the second embodiment and the refrigerator 1 including the same are the same as those of the first embodiment except for the above description, including the configuration not shown in FIG. Therefore, also in the second embodiment, it is possible to solve the above problem and suppress the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22.

  That is, in the control for operating the oxygen reduction cell 22 as described above according to the flowchart of FIG. 4, the third voltage V3 applied after the application of the first voltage V1 is higher than the first voltage V1. At the same time, the application time of the third voltage V3 is shorter than the application time of the first voltage V1, and may be, for example, 1 minute or more and 10 minutes or less, and is preferably set to 4 to 6 minutes. The reason for this is that when the application time of the third voltage V3 is less than 1 minute, the oxidized catalyst of the cathode 33 cannot be sufficiently reduced in the next oxygen reduction operation, and the application of the third voltage V3 is not possible. This is because when the time exceeds 10 minutes, the deterioration of the oxygen reduction cell 22 is promoted by the third voltage V3 higher than the first voltage V1.

  As described above, after the oxygen reduction cell 22 is operated at the first voltage V1, the third voltage V3 having a voltage value higher than the first voltage V1 is applied to the oxygen reduction cell 22 and is included in the cathode catalyst layer 34. Reduction of the cathode catalyst such as platinum is promoted, and deterioration due to elution of the cathode catalyst is suppressed. Therefore, in a state where the cathode catalyst layer 34 is activated, it is possible to apply the first voltage V1 to the oxygen reduction cell 22 when the oxygen reduction operation is resumed and to perform a steady operation.

  FIG. 5 shows a third embodiment. The third embodiment is different from the first embodiment in the control procedure described below, and is otherwise the same as the first embodiment. For this reason, configurations having the same or similar functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Together with this, FIG. 1 and FIG. 2 are also referred to as necessary.

  In the third embodiment, the power source 23 generates a first voltage V1, a second voltage V2, and a third voltage V3 having predetermined values. The second voltage V2 and the third voltage V3 are higher than the first voltage V1. These voltages are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 according to the flowchart shown in FIG.

  First, step S1 in which the second voltage V2 is applied to the oxygen reduction cell 22 for a predetermined time is executed, and the oxygen reduction operation is started. Next, step S2 for applying the first voltage V1 is executed, and the steady oxygen reduction operation is continued. Step S4 is executed when the oxygen concentration in the oxygen reduction chamber 3 is lowered to a predetermined value due to the continuous operation in Step S2, and the third voltage V3 is applied to the oxygen reduction cell 22 for a predetermined time. Continue the oxygen reduction operation. Then, step S3 is performed and the application of the voltage with respect to the oxygen reduction cell 22 is stopped, and an oxygen reduction operation is complete | finished.

  The oxygen reduction device 21 of the third embodiment and the refrigerator 1 including the same are the same as those of the first embodiment except for the above description, including the configuration not shown in FIG. Therefore, also in the third embodiment, it is possible to solve the above-described problem and suppress the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22.

  That is, in the control for operating the oxygen reduction cell 22 as described above according to the flowchart of FIG. 5, the second voltage V2 applied to the oxygen reduction cell 22 and the first voltage V1 applied before the first voltage V1 is applied. The third voltage V3 applied to the oxygen reduction cell 22 after the application of is all higher than the first voltage V1. At the same time, the application time of the second voltage V2 and the third voltage V3 is shorter than the application time of the first voltage V1, and may be, for example, 1 minute or more and 10 minutes or less, and is preferably set to 4 to 6 minutes. This is because when the application time of the second voltage V2 and the third voltage V3 is less than 1 minute, the catalyst of the oxidized cathode 33 cannot be sufficiently reduced, and the application of the second voltage V2 and the third voltage V3 is not possible. This is because when the time exceeds 10 minutes, the deterioration of the oxygen reduction cell 22 is promoted by the second voltage V2 and the third voltage V3 which are higher than the first voltage V1.

  In the third embodiment, reduction of the cathode catalyst such as platinum contained in the cathode catalyst layer 34 is promoted based on the voltage difference between the first voltage V1 and the second voltage V2 at the beginning of the operation of the oxygen reduction cell 22. Therefore, the oxygen-reducing cell 22 can be steadily operated by the first voltage V1 in a state where deterioration due to elution of the cathode catalyst is suppressed. In addition, after the oxygen reduction cell 22 was operated at the first voltage V1, the third voltage V3 having a voltage value higher than the first voltage V1 was applied to the oxygen reduction cell 22, and thus included in the cathode catalyst layer 34. Reduction of the cathode catalyst such as platinum is promoted, and deterioration due to elution of the cathode catalyst is suppressed. Therefore, in a state where the cathode catalyst layer 34 is activated, it is possible to apply the first voltage V1 to the oxygen reduction cell 22 when the oxygen reduction operation is resumed and to perform a steady operation.

  FIG. 6 shows a fourth embodiment. The fourth embodiment is different from the first embodiment in the control procedure described below, and is otherwise the same as the first embodiment. For this reason, configurations having the same or similar functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Together with this, FIG. 1 and FIG. 2 are also referred to as necessary.

  In the fourth embodiment, the power source 23 generates a first voltage V1 having a predetermined value and a third voltage V3 higher than the first voltage V1. These voltages are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 according to the flowchart shown in FIG.

  First, step S2 in which the first voltage V1 is applied to the oxygen reduction cell 22 is executed, and the oxygen reduction operation is started. Next, the controller 25 executes step S <b> 5, and measures the value of the current flowing through the oxygen reduction cell 22 using an ammeter (see FIG. 2) 23. The measurement information of the ammeter 23 is supplied to the controller 25.

  Step S <b> 6 executed next by the controller 25 is first current determination means included in the controller 25. The first current determination means compares the first lower limit threshold (Imin.) Of the current set in advance with the measurement information of the ammeter 23. When the measurement information (current value) of the ammeter 23 is larger than the first lower limit threshold, the determination by the first current determination unit is YES. In response to this result, the controller 25 causes Step S7 to continue supplying the first voltage V1. Thereby, the oxygen reduction operation is continued.

  In such a situation, when deterioration proceeds due to oxidation of the cathode catalyst layer 34 of the oxygen reduction cell 22 due to potential fluctuation during operation, the value of the current flowing through the oxygen reduction cell 22 gradually decreases.

  Accordingly, when the determination in step S6 is NO (that is, when the measurement information of the ammeter 23 is less than the first lower limit threshold value), the controller 25 sets the predetermined third voltage V3 to the oxygen reduction cell 22. Step S8 is applied. The application time of the third voltage V3 is shorter than the total application time of the first voltage V1, and may be, for example, not less than 1 minute and not more than 10 minutes, and is preferably set to 4 to 6 minutes. Following step S8, the controller 25 executes step S9 of applying the first voltage V1 to the oxygen reduction cell 22 again.

  For this reason, the potential of the cathode 33 of the oxygen-reducing cell 22 decreases in accordance with the decrease from the third voltage V3 to the first voltage V1 that is lower than the third voltage V3. As the applied voltage decreases, the reduction of the cathode catalyst such as platinum is promoted, so that deterioration due to elution of the cathode catalyst is suppressed. By reducing the cathode catalyst layer 34 in this way, this catalyst layer is activated.

  Next, the controller 25 executes Step S <b> 10 and measures the value of the current flowing through the oxygen reduction cell 22 using the ammeter 23. The measurement information is supplied to the controller 25. Further, the controller 25 executes the next step S11. This step S11 is a second current determination means included in the controller 25, and the second lower limit threshold (Imin.) Of the current preset in this means is compared with the measurement information of the ammeter 23. The second lower limit threshold and the first lower limit threshold are, for example, the same value (current value).

  If the measurement information (current value) of the ammeter 23 is larger than the second lower limit threshold, the determination in step S11 is YES, and it is determined that the deterioration of the cathode catalyst layer 34 has not progressed sufficiently. In response to this result, the controller 25 executes step S <b> 12 in which the supply of the first voltage V <b> 1 to the oxygen reduction cell 22 is continued. This oxygen reduction operation is continued for a time longer than the application time of the third voltage V3.

  In the steady operation in which the first voltage V1 is supplied, when the deterioration proceeds due to oxidation of the cathode catalyst layer 34 of the oxygen reduction cell 22 due to potential fluctuation during operation, the oxygen reduction cell 22 measured by the ammeter 23 is changed. The flowing current value gradually decreases. Thereby, if the measurement information of the ammeter 23 is less than the lower limit threshold, the determination in step S11 is NO. That is, it is determined that the deterioration of the cathode catalyst layer 34 has progressed excessively to some extent. In response to this result, the controller 25 executes step S13 to notify the refrigerator user that the deterioration of the oxygen reduction cell 22 has progressed excessively. This notification is performed by display on a display provided on the outer surface of the refrigerator 1 or a warning sound.

  In addition, when the oxygen concentration in the oxygen reduction chamber 3 is lowered to a predetermined value due to the continuous operation for a long time in Steps S7 and S12, the controller 25 executes Step S14 to change the voltage to the oxygen reduction cell 22. The application is stopped and the oxygen reduction operation is terminated.

  As described above, the oxygen reduction device 21 of the fourth embodiment measures the current flowing through the oxygen reduction cell 22 and compares it with the first lower limit threshold value in the oxygen reduction operation. As a result, when the deterioration of the cathode catalyst layer 34 becomes less than the first lower limit threshold, the potential of the cathode 33 is lowered, so that the reduction of the oxidized cathode catalyst of the cathode catalyst layer 34 is promoted and the deterioration is suppressed. Is possible.

  The oxygen reduction device 21 of the fourth embodiment and the refrigerator 1 including the same are the same as those of the first embodiment except for the above description, including the configuration not shown in FIG. Therefore, also in the fourth embodiment, the above-described problem is solved, and it is possible to suppress deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22 as described above. In the fourth embodiment, step S6 and step S11 may always monitor the current value flowing through the oxygen reduction cell 22 during operation and determine the monitored current value.

  FIG. 7 shows a fifth embodiment. The fifth embodiment is different from the first embodiment in the control procedure described below, and is otherwise the same as the first embodiment. For this reason, configurations having the same or similar functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Together with this, FIG. 1 and FIG. 2 are also referred to as necessary.

  In the fifth embodiment, the power source 23 generates a first voltage V1 having a predetermined value and a third voltage V3 higher than the first voltage V1. These voltages are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 as shown in the time chart of FIG.

  That is, the controller 25 applies the first voltage V1 to the oxygen reduction cell 22 to start the oxygen reduction operation, and further applies the third voltage V3 to the oxygen reduction cell 22 every predetermined time t during this operation. As a result, the potential of the cathode 33 of the oxygen-reducing cell 22 decreases every predetermined time t in response to a decrease from the third voltage V3 to the first voltage V1 lower than the third voltage V3. Along with this, reduction of the cathode catalyst such as platinum is promoted, so that it is possible to suppress the progress of deterioration due to elution of the cathode catalyst. It should be noted that the controller 25 stops applying the voltage to the oxygen reduction cell 22 and terminates the oxygen reduction operation when the oxygen concentration in the oxygen reduction chamber 3 is lowered to a predetermined value by such operation.

  The oxygen reduction device 21 of the fifth embodiment and the refrigerator 1 including the same are the same as those of the first embodiment except for the above description, including the configuration not shown in FIG. Therefore, also in the fifth embodiment, it is possible to solve the above-described problems and suppress the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22 as described above.

  8 and 9 show a sixth embodiment. The sixth embodiment is different from the first embodiment in matters described below, and is otherwise the same as the first embodiment. For this reason, configurations having the same or similar functions as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and description thereof is omitted. Together with this, FIG. 1 is also referred to if necessary.

  In the sixth embodiment, voltage measuring means such as a voltmeter 26 (see FIG. 8) is used instead of the ammeter used in the first embodiment. The voltmeter 26 for measuring the voltage applied to the oxygen reduction cell 22 is connected to the anode current collector 38 and the cathode current collector 39, and the measurement information is supplied to the controller 25. The power source 23 generates a first current I1 having a predetermined value and a second current I2 having a predetermined current value that is larger than the first current I1. These currents are applied to the oxygen reduction cell 22 by the controller 25.

  The oxygen reduction device 21 of the sixth embodiment is operated with the current flowing through the oxygen reduction cell 22 kept constant. The advantages of operating the oxygen reduction cell 22 with a constant current will be described below.

  The rate of decrease of the oxygen concentration in the oxygen reduction chamber 3 of the refrigerator 1 accompanying the operation of the oxygen reduction cell 22 depends on the current value flowing through the oxygen reduction cell 22 and the application time. For this reason, under the operating conditions where the current value is constant, the time required for the oxygen reduction chamber 3 to reach the desired oxygen reduction concentration is uniquely determined by the application time. Accordingly, it is possible to monitor the oxygen concentration in the oxygen-reducing chamber 3 by managing the application time without providing a measuring means such as an oxygen concentration meter in the oxygen-reducing chamber 3.

  Next, the operation of the oxygen reduction device 21 will be described. The controller 25 monitors the voltage (cell voltage) applied to the oxygen reduction cell 22 from the measurement information of the voltmeter 26, and reduces the first current I2 and the second current I2 generated by the power supply 23 according to the flowchart shown in FIG. The oxygen reduction cell 22 is operated in order to reduce the oxygen concentration in the oxygen reduction chamber 3 by being applied to the oxygen cell 22.

  The oxygen reduction operation of the oxygen reduction cell 22 is started by first executing step S1 in which the second current I2 is applied for a predetermined time. Next, step S2 for applying the first current I1 is executed, and the oxygen reduction operation is continued. Finally, step S3 for stopping the application of current to the oxygen reduction cell 22 at a predetermined time is executed, and the oxygen reduction operation is terminated.

  In such control, the value of the second current I2 applied to the oxygen reduction cell 22 before the application of the first current I1 is larger than the value of the first current I1. At the same time, the application time of the second current I2 is shorter than the application time of the first current I1, and may be, for example, not less than 1 minute and not more than 10 minutes, and is preferably set to 4 to 6 minutes. The reason is that the applied voltage is high when the applied current is large, and conversely the applied voltage is low when the applied current is small. Therefore, when the application time of the second current I2 is less than 1 minute, the oxidized cathode 33 When the catalyst cannot be sufficiently reduced and the application time of the second current I2 exceeds 10 minutes, the deterioration of the oxygen reduction cell 22 is promoted by the second current I2 having a current value larger than the first current I1. It is.

  The cathode catalyst layer 34 containing a cathode catalyst such as platinum in the oxygen reduction cell 22 may be oxidized along with potential fluctuations during operation of the oxygen reduction cell 22. Further, when the operation of the oxygen reduction cell 22 is stopped, the cathode 33 may be exposed to a high potential due to oxygen remaining in the cathode 33, and a part of the cathode catalyst layer 34 may be oxidized. When at least a part of the cathode catalyst layer 34 is oxidized, the cathode catalyst such as platinum is easily eluted.

  When the oxygen reduction cell 22 in such a state is operated next, the current applied to the oxygen reduction cell 22 is controlled according to the flowchart of FIG. In response to a decrease from the value of the second current I2 to the value of the first current I1. Accordingly, the potential of the cathode 33 is lowered and the reduction of the cathode catalyst such as platinum is promoted, so that deterioration due to elution of the cathode catalyst is suppressed and the cathode catalyst is activated. The application time of the second current I2 is preferably just before the application of the first current I1. Then, following the reduction of the cathode catalyst layer 34, the operation proceeds to the steady operation of the oxygen reduction cell 22 by the first current I1, that is, the steady oxygen reduction operation. This operation is performed for a time longer than the application time of the second current I2. Thereby, step S3 is performed in the stage where the oxygen concentration of the oxygen reduction chamber 3 fell to a predetermined value, and oxygen reduction operation is complete | finished.

(Example 2)
In Example 2, the anode 31 of the area of 20 cm ^2, the area is a cathode 33 of 12cm ^2, and create a reduced oxygen cell 22 by joining the electrolyte membrane 37 of the polymer by hot pressing. The hot press was performed under the conditions of a temperature of 150 ° C., a press pressure of 40 kg / cm ² , and a press time of 3 minutes. The test was performed by sandwiching the oxygen-reducing cell 22 produced as described above between the first fastening member 41 and the second fastening member 45 shown in FIG.

  In this test, the anode chamber 42 was filled with water, and air was supplied to the cathode chamber 46 at 120 mL / min. An electronic load device (not shown), a power source 23, and a voltmeter 26 were connected to the anode current collector 38 and the cathode current collector 39. Then, a current of 3.0 A was applied as the second current I2 for 5 minutes before the controller 25 applied the current of 2.4 A to the oxygen reduction cell 22 as the first current I1. Thereafter, the oxygen reduction operation was continued at a current of 2.4 A, and the voltage after 1 hour and 1000 hours from this point was measured.

(Comparative Example 2)
The oxygen reducing element was produced in the same manner as in Example 2. The test was performed by sandwiching the oxygen-reducing cell 22 produced as described above between the first fastening member 41 and the second fastening member 45 shown in FIG. In this case, the anode chamber 42 was filled with water, and air was supplied to the cathode chamber 46 at 120 mL / min. An electronic load device (not shown), a power source, and a voltmeter 26 were connected to the anode current collector 38 and the cathode current collector 39. Then, the oxygen reduction operation was started at a constant current of 2.4 A, and the voltage after 1 hour and 1000 hours after the start was measured. The results are shown in Table 2.

  As shown in Table 2, by applying the second current I2 of 3.0A for 5 minutes before applying the first current I1 of 2.4A, the cell voltage after 1 hour from the start of the reaction of the oxygen reduction cell 22, and 1000 It was confirmed that the increase in both electrolytic voltages after time was suppressed to a low level as compared with Comparative Example 2.

  FIG. 10 shows a seventh embodiment. The seventh embodiment differs from the sixth embodiment in the control procedure described below, and is otherwise the same as the sixth embodiment. For this reason, the structure which exhibits the same or similar function as that of the sixth embodiment is denoted by the same reference numeral as that of the sixth embodiment, and the description thereof is omitted. Together with this, FIG. 1 is also referred to if necessary.

  In the seventh embodiment, the power source 23 generates a first current I1 having a predetermined value and a third current I3 having a predetermined value and a value larger than the first current I1. These currents are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 according to the flowchart shown in FIG.

  First, the step S2 of applying the first current I1 to the oxygen reduction cell 22 is executed for the oxygen reduction cell 22, and the steady oxygen reduction operation is started. Step S4 is executed when the oxygen concentration in the oxygen-reducing chamber 3 has dropped to a predetermined value due to the continued operation in step S2, and the third current I3 is applied to the oxygen-reducing cell 22 for a predetermined time. Continue hypoxic operation. Thereafter, step S3 is executed to stop the application of current to the oxygen reduction cell 22, and the oxygen reduction operation is terminated.

  The oxygen reduction device 21 of the seventh embodiment and the refrigerator 1 equipped with the same are the same as those of the sixth embodiment except for the above description, including the configuration not shown in FIG. Therefore, also in the seventh embodiment, the above-described problem can be solved and deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22 can be suppressed.

  That is, in the control for operating the oxygen reduction cell 22 as described above according to the flowchart of FIG. 10, the value of the third current I3 applied after the application of the first current I1 is larger than the value of the first current I1. At the same time, the application time of the third current I3 is shorter than the application time of the first current I1, and may be, for example, not less than 1 minute and not more than 10 minutes, and is preferably set to 4 to 6 minutes. This is because, when the application time of the third current I3 is less than 1 minute, the oxidized catalyst of the cathode 33 cannot be sufficiently reduced in the next oxygen reduction operation, and the application of the third current I3 is not possible. This is because when the time exceeds 10 minutes, the deterioration of the oxygen reduction cell 22 is promoted by the third current I3 larger than the first current I1.

  As described above, after the oxygen reduction cell 22 is operated with the first current I1, the third current I3 having a current value larger than the first current I1 is applied to the oxygen reduction cell 22, and thus included in the cathode catalyst layer 34. Reduction of the cathode catalyst such as platinum is promoted, and deterioration due to elution of the cathode catalyst is suppressed. Therefore, in a state where the cathode catalyst layer 34 is activated, it is possible to apply the first current I1 to the oxygen reduction cell 22 when the oxygen reduction operation is resumed and to perform a steady operation.

  FIG. 11 shows an eighth embodiment. The eighth embodiment differs from the sixth embodiment in the control procedure described below, and is otherwise the same as the sixth embodiment. For this reason, the structure which exhibits the same or similar function as that of the sixth embodiment is denoted by the same reference numeral as that of the sixth embodiment, and the description thereof is omitted. Together with this, FIG. 1 and FIG. 8 are also referred to as necessary.

  In the eighth embodiment, the power source 23 generates a first current I1, a second current I2, and a third current I3 having predetermined values. The values of the second current I2 and the third current I3 are larger than the value of the first current I1. The oxygen reduction device 21 is operated by applying these currents between the anode 31 and the cathode 33 of the oxygen reduction cell 22 by the controller 25 in accordance with the flowchart shown in FIG.

  First, step S1 in which the second current I2 is applied for a predetermined time to the oxygen reduction cell 22 is executed, and the oxygen reduction operation is started. Next, step S2 for applying the first current I1 is executed, and the steady oxygen reduction operation is continued. Step S4 is executed when the oxygen concentration in the oxygen-reducing chamber 3 has dropped to a predetermined value due to the continued operation in step S2, and the third current I3 is applied to the oxygen-reducing cell 22 for a predetermined time. Continue hypoxic operation. Then, step S3 is performed and the application of the electric current with respect to the oxygen reduction cell 22 is stopped, and oxygen reduction operation is complete | finished.

  The oxygen reduction device 21 of the eighth embodiment and the refrigerator 1 including the same are the same as those of the sixth embodiment, including the configuration not shown in FIG. 11, except for the above description. Therefore, also in the eighth embodiment, it is possible to solve the above problems and suppress the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22.

  That is, in the control for operating the oxygen reduction cell 22 as described above according to the flowchart of FIG. 11, the value of the second current I2 applied to the oxygen reduction cell 22 before the first current I1 is applied, and the first The value of the third current I3 applied to the oxygen reduction cell 22 after the application of the current I1 is larger than the value of the first current I1. At the same time, the application time of the second current I2 and the third current I3 is shorter than the application time of the first current I1, and may be, for example, 1 minute or more and 10 minutes or less, and is preferably set to 4 to 6 minutes. This is because if the application time of the second current I2 and the third current I3 is less than 1 minute, the oxidized catalyst of the cathode 33 cannot be sufficiently reduced, and the application of the second current I2 and the third current I3 is not possible. This is because when the time exceeds 10 minutes, the deterioration of the oxygen reduction cell 22 is promoted by the second current I2 and the third current I3 which are larger than the first current I1.

  In the eighth embodiment, the cathode catalyst such as platinum contained in the cathode catalyst layer 34 can be reduced based on the current difference between the first current I1 and the second current I2 at the beginning of operation of the oxygen reduction cell 22. In a state where deterioration due to elution of the cathode catalyst is suppressed, the oxygen reduction cell 22 can be operated in a steady state by applying the first current I1. In addition, after the oxygen reduction cell 22 was operated with the first current I1, the third current I3 having a current value smaller than the first current I1 was applied to the oxygen reduction cell 22 and was included in the cathode catalyst layer 34. Reduction of the cathode catalyst such as platinum is promoted, and deterioration due to elution of the cathode catalyst is suppressed. Therefore, in a state where the cathode catalyst layer 34 is activated, it is possible to apply the first current I1 to the oxygen reduction cell 22 when the oxygen reduction operation is resumed and to perform a steady operation.

  FIG. 12 shows a ninth embodiment. The ninth embodiment differs from the sixth embodiment in the control procedure described below, and is otherwise the same as the sixth embodiment. For this reason, the structure which exhibits the same or similar function as that of the sixth embodiment is denoted by the same reference numeral as that of the sixth embodiment, and the description thereof is omitted. Together with this, FIG. 1 and FIG. 8 are also referred to as necessary.

  In the ninth embodiment, the power source 23 generates a first current I1 having a predetermined value and a third current I3 having a predetermined value and a current value larger than the first current I1. These currents are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 according to the flowchart shown in FIG.

  First, step S2 in which the first current I1 is applied to the oxygen reduction cell 22 is executed, and the oxygen reduction operation is started. Next, the controller 25 executes step S <b> 5, and measures the voltage applied to the oxygen reduction cell 22 with a voltmeter (see FIG. 8) 26. Measurement information of the voltmeter 26 is supplied to the controller 25.

  Step S <b> 6 executed next by the controller 25 is first voltage determination means included in the controller 25. The first voltage determination means compares the first upper limit threshold (Vmax.) Of the voltage set in advance with the measurement information (voltage value) of the voltmeter 26. When the measurement information of the voltmeter 26 is less than the first upper limit threshold, the determination by the first voltage determination unit is YES. In response to this result, the controller 25 executes step S7 in which the application of the first current I1 is continued, whereby the oxygen reduction operation is continued.

  Under such circumstances, when the deterioration proceeds due to oxidation of the cathode catalyst layer 34 of the oxygen reduction cell 22 due to potential fluctuation during operation, the voltage value applied to the oxygen reduction cell 22 gradually increases.

  Accordingly, when the determination in step S6 becomes NO (that is, when the voltage value measured by the voltmeter 26 exceeds the first upper limit threshold value), the controller 25 sets the predetermined third current I3. Step S8 applied to the oxygen reduction cell 22 is executed. The application time of the third current I3 is shorter than the total application time of the first current I1, and may be, for example, 1 minute or more and 10 minutes or less, and is preferably set to 4 to 6 minutes. After step S8, the controller 25 executes step S9 in which the first current I1 is applied to the oxygen reduction cell 22 again.

  For this reason, the current flowing through the cathode 33 of the oxygen reduction cell 22 decreases in accordance with the decrease from the third current I3 to the first current I1 having a smaller current value. As the current value decreases in this manner, the reduction of the cathode catalyst such as platinum is promoted, so that deterioration due to elution of the cathode catalyst is suppressed. By reducing the cathode catalyst layer 34 in this way, this catalyst layer is activated.

  Next, the controller 25 executes step S <b> 10 and measures the voltage value applied to the oxygen reduction cell 22 by the voltmeter 26. The measurement information is supplied to the controller 25. Further, the controller 25 executes the next step S11. This step S11 is a second voltage determination unit included in the controller 25, and the second upper limit threshold (Vmax.) Of the voltage preset in this unit is compared with the measurement information of the voltmeter 26. The second upper limit threshold and the first upper limit threshold are, for example, the same value (voltage value).

  If the determination by the second voltage determination means is YES, that is, if the voltage value measured by the voltmeter 26 is less than the second upper limit threshold, it is determined that the deterioration of the cathode catalyst layer 34 has not progressed. . In response to this result, the controller 25 executes step S <b> 12 in which the supply of the first current I <b> 1 to the oxygen reduction cell 22 is continued. This oxygen reduction operation is continued for a time longer than the application time of the third current I3.

  In the steady operation in which the first current I1 is supplied, if the deterioration proceeds due to oxidation of the cathode catalyst layer 34 of the oxygen reduction cell 22 due to potential fluctuation during operation or the like, the oxygen reduction cell 22 measured by the voltmeter 26 is measured. The applied voltage value gradually increases. As a result, when the determination by the second voltage determination means is NO, that is, when the voltage value measured by the ammeter 26 exceeds the second upper limit threshold (Vmax.), The cathode catalyst layer 34 is excessively deteriorated. Judged to have progressed. In response to this result, the controller 25 executes step S13 to notify the user of the refrigerator 1 (see FIG. 1) that the deterioration of the oxygen reduction cell 22 has progressed excessively. This notification is performed by display on a display provided on the outer surface of the refrigerator 1 or a warning sound.

  Further, when the oxygen concentration in the oxygen-reducing chamber 3 is lowered to a predetermined value due to the continuous operation for a long time in step 7 and step S12, the controller 25 executes step S14 to supply current to the oxygen-reducing cell 22. The application is stopped and the oxygen reduction operation is terminated.

  As described above, the oxygen reduction device 21 of the ninth embodiment measures the voltage applied to the oxygen reduction cell 22 in the oxygen reduction operation and compares it with the first upper limit threshold of voltage. As a result, when the deterioration of the cathode catalyst layer 34 exceeds the first upper limit threshold set in the first voltage determination means, the potential of the cathode 33 is lowered, so that the reduced cathode catalyst in the cathode catalyst layer 34 is reduced. It is possible to suppress the deterioration.

  Except for the above description, the oxygen reduction device 21 of the ninth embodiment and the refrigerator 1 including the same are the same as those of the sixth embodiment, including the configuration not shown in FIG. Therefore, also in the ninth embodiment, the above-described problem is solved, and the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22 can be suppressed as described above. In the ninth embodiment, in step S6 and step S11, the value of the voltage applied to the oxygen reduction cell 22 during operation may be constantly monitored and determined.

  FIG. 13 shows a tenth embodiment. The tenth embodiment is different from the sixth embodiment in the control procedure described below, and is otherwise the same as the sixth embodiment. For this reason, the structure which exhibits the same or similar function as that of the sixth embodiment is denoted by the same reference numeral as that of the sixth embodiment, and the description thereof is omitted. Together with this, FIG. 1 and FIG. 8 are also referred to as necessary.

  In the tenth embodiment, the power supply 23 generates a first current I1 having a predetermined value and a third current I3 having a larger current value. These currents are applied by the controller 25 between the anode 31 and the cathode 33 of the oxygen reduction cell 22 as shown in the time chart of FIG.

  That is, the controller 25 applies the first current I1 to the oxygen reduction cell 22 to start the operation, and then applies the third current I3 to the oxygen reduction cell 22 every predetermined time t during the operation. As a result, the current flowing through the cathode 33 of the oxygen reduction cell 22 every predetermined time t decreases as the current value decreases from the third current I3 to the first current I1 having a smaller current value. As the current flowing through the oxygen-reducing cell 22 decreases in this way, the reduction of the cathode catalyst such as platinum is promoted, so that the progress of deterioration due to the elution of the cathode catalyst can be suppressed. It should be noted that the controller 25 stops applying the current to the oxygen reduction cell 22 and terminates the oxygen reduction operation when the oxygen concentration in the oxygen reduction chamber 3 is lowered to a predetermined value by such operation.

  The oxygen reduction device 21 of the tenth embodiment and the refrigerator 1 including the same are the same as those of the sixth embodiment except for the configuration described above, including the configuration not shown in FIG. Therefore, also in the tenth embodiment, the above-described problem is solved, and the deterioration of the cathode catalyst layer 34 of the cathode 33 included in the oxygen reduction cell 22 can be suppressed as described above.

  Although several embodiments have been described as described above, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and for example, various omissions, replacements, and changes can be made. At the same time, these embodiments and modifications thereof are included in the scope of the invention, and also included in the invention described in the claims and the equivalent scope thereof.

  The oxygen reduction device of the embodiment can be applied to commercial and household refrigerators that can preserve vegetables, foods, etc. in a high-quality state for a long period of time, and is sensitive to oxygen concentration, medicines, medical materials, It can be applied to refrigerators that store chemical substances.

  DESCRIPTION OF SYMBOLS 1 ... Refrigerator, 2 ... Refrigerator main body, 3 ... Hypoxic chamber, 4 ... Hypoxic box, 5 ... Opening / closing member, 21 ... Hypoxic device, 22 ... Hypoxic cell, 23 ... Power supply, 24 ... Ammeter (Current measuring means) ), 25 ... Controller 26 ... Voltmeter (voltage measuring means), 31 ... Anode, 33 ... Cathode, 34 ... Cathode electrode, 37 ... Electrolyte membrane, V1 ... First voltage, V2 ... Second voltage, V3 ... Third voltage , I1 ... first current, I2 ... second current, I3 ... third current

Claims (13)

A hypoxic cell comprising a cathode having a cathode catalyst layer, an anode, and an electrolyte membrane sandwiched between the cathode and the anode, wherein the electrolyte membrane has proton conductivity;
A power supply that generates the first voltage V1 and at least one of the second voltage V2 and the third voltage V3 higher than the voltage V1,
In order to generate a hypoxic reaction at the cathode, the first voltage V1 is applied between the cathode and the anode, and at least one of the first voltage V1 before and after the application of the first voltage V1. A controller for applying the voltage higher than
An oxygen reduction device comprising:   The apparatus further comprises current measuring means for measuring the current flowing through the oxygen-reducing cell, and the controller has current determining means in which a predetermined current value is set in advance as a threshold, and after the application of the first voltage V1 is started, When the current value measured by the current measuring means is less than the threshold value, the controller applies a voltage higher than the first voltage V1 to the oxygen reduction cell and then applies the first voltage V1. The oxygen reduction device according to claim 1.   2. The oxygen reduction device according to claim 1, wherein a voltage higher than the first voltage V <b> 1 is applied by the controller every predetermined time during the application of the first voltage V <b> 1. Between the anode sandwiching the electrolyte membrane having proton conductivity and the cathode having the cathode catalyst layer, at least one of the first voltage V1 and the second voltage V2 and the third voltage V3 higher than the voltage V1. A method of operating a hypoxia device applied to generate a hypoxic reaction at the cathode, comprising:
A method of operating an oxygen reduction device, wherein the voltage higher than the first voltage V1 is applied before or after the application of the first voltage V1.   If the value of the current flowing through the oxygen reduction cell after the start of application of the first voltage V1 is less than a preset current value, a voltage higher than the first voltage V1 is applied to the oxygen reduction cell. The operation method of the oxygen reduction device according to claim 4, wherein the first voltage V1 is applied.   The operation method of the oxygen reduction device according to claim 4, wherein a voltage higher than the first voltage V1 is applied every predetermined time during the application of the first voltage V1. A hypoxic cell comprising a cathode having a cathode catalyst layer, an anode, and an electrolyte membrane sandwiched between the cathode and the anode, wherein the electrolyte membrane has proton conductivity;
A power source for generating a first current I1 and at least one of a second current I2 and a third current I3 having a value larger than the current I1,
In order to generate a hypoxic reaction at the cathode, the first current I1 is applied between the cathode and the anode, and at least one of the first current I1 before and after the application of the first current I1. A controller for applying the current having a larger value;
An oxygen reduction device comprising:   The controller further comprises voltage measuring means for measuring the voltage applied to the oxygen reduction cell, the controller having voltage determination means in which a predetermined voltage value is set in advance as a threshold value, and the voltage after the start of application of the first current I1. When the voltage value measured by the measuring means exceeds the threshold value, the controller applies the first current I1 after applying a current larger than the first current I1 to the oxygen reduction cell. The oxygen reduction device according to claim 7.   The oxygen reduction device according to claim 7, wherein a current higher than the first current I1 is applied by the controller at predetermined time intervals during the application of the first current I1. Between the anode sandwiching the electrolyte membrane having proton conductivity and the cathode having the cathode catalyst layer, at least one of the first current I1 and the second current I2 and the third current I3 having a value larger than the current I1. One of the currents is a method of operating the oxygen reduction device applied to generate the oxygen reduction reaction at the cathode,
A method of operating an oxygen reduction device, wherein the current having a value larger than that of the first current I1 is applied before or after the application of the first current I1.   When the voltage applied to the oxygen reduction cell after the start of application of the first current I1 exceeds a preset voltage value, a current higher than the first current I1 is applied to the oxygen reduction cell and the first current I1 is applied. The operation method of the oxygen reduction device according to claim 10, wherein the current I <b> 1 is applied.   The operation method of the oxygen reduction device according to claim 10, wherein a current having a value larger than the first current I1 is applied at predetermined time intervals during application of the first current I. A refrigerator body having an oxygen reduction box forming an oxygen reduction chamber;
An opening / closing member that is attached to the refrigerator main body so that the oxygen reduction box can be opened and closed, and that holds the oxygen reduction chamber in a closed state in a closed state;
10. The oxygen reduction device according to any one of claims 1 to 3 and claim 7 to 9, wherein the oxygen reduction cell is configured such that a cathode of the oxygen reduction cell reacts with oxygen in the oxygen reduction chamber. The oxygen reduction device disposed in the refrigerator body;
The refrigerator characterized by comprising.

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