JP2014094334A - Oxygen decreasing device and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen decreasing device which can control performance deterioration due to cathode flooding phenomena and impurity ions and can also control the deterioration of durability resulting from the exfoliation between an anode and an electrolyte film.SOLUTION: The oxygen decreasing device includes an oxygen decreasing cell, an electrode assembly, and cathode current-collecting layer. The oxygen decreasing cell includes an anode in which a catalyst which oxidizes the water vapor supplied is contained, a cathode which has the cathode catalyst layer in which the catalyst which reduces the oxygen is contained, and an electrolyte film held between the anode and the cathode. The electrolyte film has proton conductivity. The electrode assembly is arranged across the anode between the electrolyte film. The electrode assembly includes the anode current-collecting layer and a vaporizing layer to which water is supplied. The vaporizing layer is arranged at least on one surface of both surfaces of anode current-collecting layer. The vaporizing layer evaporates the water supplied to the layer to water vapor in order to supply to the anode. It is characterized to arrange the cathode current-collecting layer across the cathode between the electrolyte film.

Description

  Embodiments of the present invention relate to an oxygen reduction device for reducing the oxygen concentration, and a refrigerator including this device.

  In order to enhance the storage stability of foods and the like, oxygen reduction devices have been proposed in which the oxygen concentration in a 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 (liquid) can be supplied to the anode. As a result, water is electrolyzed at the anode and a water generation reaction is performed at the cathode, so that the oxygen concentration in the storage space is 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.

  In the oxygen reduction device, a phenomenon in which water stagnates at the cathode (cathode flooding phenomenon) may occur. This phenomenon is easily manifested when extra water is supplied to the cathode in addition to water (liquid) generated at the cathode by the oxygen-reducing reaction.

That is, during the operation of the oxygen-reducing cell equipped with the electrolyte membrane having proton conductivity, several protons (H ⁺ ) generated by the electrolysis of water at the anode supplied with water (liquid) are about several molecules. Water molecules move from the anode to the cathode. As a result, the excess water at the cathode is not smoothly discharged from the cathode but stays at the cathode.

  As the cathode flooding phenomenon occurs, the staying water closes the pores of the cathode catalyst layer, so that the supply of oxygen to the cathode catalyst layer is hindered. In such a situation, the voltage required for the oxygen-reducing reaction may increase and become excessive, thereby reducing the performance of the oxygen-reducing device.

Water (liquid) supplied to the anode may contain impurity ions such as metal ions. When the oxygen reduction device is operated under such water supply, impurity ions are accumulated in the polymer electrolyte membrane. As this accumulation proceeds, the proton (H ⁺ ) conductivity in the electrolyte membrane decreases. As a result, since the electrical resistance of the oxygen reduction cell increases, the voltage required for the oxygen reduction reaction may increase and become excessive, thereby reducing the performance of the oxygen reduction device.

  During operation of the oxygen reduction device, the polymer electrolyte membrane is swollen by water molecules moving from the anode to the cathode. At the same time, during operation of the oxygen reduction device, the oxygen reduction cell is in a state where the temperature is raised by the heat generated by the reaction. For this reason, as the operation of the oxygen reduction device is stopped, the electrolyte membrane is dried by the residual heat of the oxygen reduction cell. On the other hand, every time the storage space is opened, the oxygen concentration in this space becomes the same as the oxygen concentration in the atmosphere. Accordingly, each time the opened storage space is closed, the oxygen reduction device is operated so that the storage space has a target low oxygen concentration.

  As a result, the electrolyte membrane of the oxygen reduction device repeats swelling and drying, and the dimensions of the electrolyte membrane change with such swelling and drying. Due to this, there is a possibility that peeling occurs at the joint surface between the electrolyte membrane of the oxygen reduction cell and the anode, and the durability of the oxygen reduction device is lowered.

Japanese Patent Laid-Open No. 9-19621 Japanese Patent No. 3299422

  The embodiment is capable of suppressing performance deterioration due to cathode flooding phenomenon and impurity ions, and is also capable of suppressing deterioration in durability due to peeling between the anode and the electrolyte membrane. It is to provide an apparatus and a refrigerator.

  In order to solve the above-described problems, an oxygen reduction device according to an embodiment includes an oxygen reduction cell, an electrode assembly, and a cathode current collecting layer. The oxygen reduction cell includes an anode containing a catalyst that oxidizes supplied water vapor, a cathode having a cathode catalyst layer containing a catalyst that reduces oxygen, and an electrolyte membrane sandwiched between the cathode and the anode. The electrolyte membrane has proton conductivity. The electrode assembly is disposed between the electrolyte membrane and an anode. The electrode assembly includes an anode current collecting layer and a vaporized layer to which water is supplied. The vaporization layer is disposed on at least one of both surfaces of the anode current collecting layer. The vaporization layer supplies the supplied water to the anode as water vapor. The cathode current collecting layer is disposed with the cathode sandwiched between the electrolyte membrane.

It is a schematic sectional drawing which shows a part of refrigerator which concerns on one embodiment. It is sectional drawing which shows schematically the structure of the oxygen reducing apparatus used for the refrigerator of FIG.

  Hereinafter, an oxygen reduction device 21 according to an embodiment and a storage such as a refrigerator 1 including the oxygen reduction device 21 will be described in detail with reference to FIGS. 1 and 2.

  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 middle in the vertical direction 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. The oxygen reduction box 4 is cooled to a temperature suitable for refrigeration of food by the refrigerant flowing through the refrigerant pipe. 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 is guided by the rail 7.

  Therefore, the container 6 can smoothly 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.

  For example, the freezer compartment 13 divided into upper and lower three stages is formed in the lowermost part of the refrigerator main body 2 independently of the oxygen reducing 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. The refrigerator main body 2 is formed with a recess 20 that is open on one side, for example, the back surface. The recess 20 is provided on the rear side of the oxygen reduction chamber 3. The recess 20 and the oxygen-reducing chamber 3 are communicated with each other via a through hole 2a formed in a wall that partitions them.

  Next, the oxygen reduction device 21 will be described with reference to FIG. The oxygen reduction device 21 includes an oxygen reduction stack 22, a power source 24, an oxygen reduction container 25, voltage detection means such as a voltmeter 27, a controller 29, and the like.

  The oxygen reduction stack 22 includes an oxygen reduction cell 23, an electrode assembly 36, and a cathode current collecting layer 39, which are elements of the stack. The oxygen reduction stack 22 is not limited to one, and a plurality of oxygen reduction stacks 22 may be provided.

  The oxygen reduction cell 23 includes an anode 30 that is an element of the oxygen reduction stack 22, a cathode 31, and an electrolyte membrane 35.

  A polymer electrolyte membrane can be suitably used for the electrolyte membrane 35. One side surface of the anode 30 is joined to one side surface of the electrolyte membrane 35. The cathode 31 is bonded to the other side surface of the electrolyte membrane 35 by contacting a cathode catalyst layer 32 described later. Therefore, the electrolyte membrane 35 is sandwiched between the anode 30 and the cathode 31.

  An electrode assembly 36 is joined to the other side of the anode 30, that is, the side that is not in contact with the electrolyte membrane 35. Therefore, the electrode assembly 36 is disposed between the electrolyte membrane 35 and the anode 30.

  The electrode assembly 36 includes an anode current collecting layer 37 and a vaporization layer 38 that are elements of the oxygen reduction stack 22. The anode current collecting layer 37 of the electrode assembly 36 forms one electrode of the oxygen reduction stack 22. The anode current collecting layer 37 is bonded to the side surface of the anode 30. The vaporized layer 38 of the electrode assembly 36 is bonded to the anode current collecting layer 37 on the opposite side of the anode 30 with the anode current collecting layer 37 as a boundary. Therefore, the vaporization layer 38 is disposed with the anode current collecting layer 37 between the anode 30 and the anode 30.

  Note that the electrode assembly 36 may be formed by bonding the vaporized layer 38 to the anode side surface of the anode current collecting layer 37, contrary to the present embodiment. The electrode assembly 36 may be formed by bonding the vaporized layer 38 to both side surfaces of the anode current collecting layer 37.

  In the case of using these electrode assemblies 36, an electrode insulating body is provided by interposing an electrically insulating layer having water vapor permeability between the vaporization layer bonded to the anode side surface of the anode current collecting layer 37 and the anode 30. 36 may be disposed with the anode 30 sandwiched between the electrolyte membrane 35. Thereby, as compared with the configuration in which the vaporized layer 38 is bonded to the anode 30 and the electrode assembly 36 is disposed, it is possible to avoid the possibility that the oxygen reduction cell 23 and the electrode assembly 36 are corroded. Therefore, it is possible to ensure the durability of the oxygen reduction device 21. The oxygen reduction device 21 of this embodiment that does not require such insulation measures is preferable in that it has no corrosion problem and is excellent in durability despite its small number of parts.

  A cathode current collecting layer 39 as an element of the oxygen reduction stack 22 is joined to the outer surface of the cathode 31, that is, the side surface of a gas diffusion layer 34 described later that is not in contact with the porous layer 33 described later. The cathode current collecting layer 39 forms the other electrode of the oxygen reduction stack 22. The cathode current collecting layer 39 and the anode current collecting layer 37 are electrically connected to the power source 24.

  The oxygen reduction container 25 contains the oxygen reduction stack 22 configured as described above. The oxygen reduction container 25 is formed by connecting a first container member 41 and a second container member 45 made of an electrical insulating material. The electrolyte container 35 of the oxygen reduction cell 23 is sandwiched between the first container member 41 and the second container member 45. At the same time, the first container member 41 and the second container member 45 fasten the oxygen reduction stack 22 along its thickness direction. Thereby, the closeness at each joint surface is ensured.

  An anode chamber 42 is formed between the first container member 41 and the electrode assembly 36 covering the anode 30. A cathode chamber 46 is formed between the second container member 45 and the cathode current collecting layer 39 covering the cathode 31.

  The first container 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 container member 41. Water for electrolysis, such as water (liquid), is introduced into the anode chamber 42 from water supply means such as a water supply tank (not shown) connected to the water intake port 43. The water (liquid) supplied to the anode chamber 42 may be an acidic aqueous solution or the like.

The oxygen outlet 44 is provided in the upper part of the first container member 41 and guides oxygen generated by water oxidation reaction (electrolysis reaction) at the anode 30 from the anode chamber 42 to the outside.

  The second container 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 in the side wall portion of the second container member 45 facing the cathode 31, and introduces air (oxygen) used for the oxygen reduction reaction into the cathode chamber 46. The drain port 48 is provided in the lower end part of the 2nd container member 45, and guides the water produced | generated by the oxygen reduction reaction from the cathode chamber 46 outside.

  Next, each element of the oxygen reduction stack having the oxygen reduction cell 23 will be described in more detail.

  First, the anode 30 will be described. The anode 30 contains a catalyst (anode catalyst) having an ability to oxidize water vapor. The anode catalyst is preferably supported on a substrate.

As the anode catalyst, for example, a composite oxide of a conductive metal oxide and a matrix oxide can be used. Examples of the conductive metal oxide include ruthenium oxide (RuO ₂ ) and iridium oxide (IrO ₂ ). Examples of the composite oxide with the matrix oxide include titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), and tantalum oxide (Ta ₂ O).

The anode catalyst may be selected in consideration of its activity, durability, cost and the like. As the composite oxide that forms this catalyst, in addition to the above, for example, RuO ₂ —Ta ₂ O, RuO ₂ —IrO ₂ , RuO ₂ —IrO ₂ —TiO ₂ , RuO ₂ —SnO ₂ , RuO ₂ —Ta ₂ O, IrO ₂ -Ta ₂ O, and the like can be given.

  The base material supporting the anode catalyst has a mesh structure, and is selected in consideration of conductivity, electrochemical stability, adhesion to the anode catalyst, and the like. For example, an expanded metal such as titanium, a punching metal, an etching metal or the like that has been used in the field of the electrolytic industry can be used as the base material. The electrode in which the surface of the base material made of titanium is coated with the composite oxide is called a dimensionally stable (DSA) electrode.

  The anode 30 can be manufactured by a technique such as a coating method, a dipping method, or a spray method. For example, a method for manufacturing the anode 30 by the dipping method will be described below. As a base material, a titanium expanded metal having a thickness of 100 μm and an aperture ratio of 30% is prepared.

First, this substrate is washed after being immersed in a 10% oxalic acid aqueous solution maintained at 80 ° C. for 1 hour. Thereby, the surface of a base material is roughened and activated. Next, an immersion process, a drying process, and a baking process are further repeated a plurality of times in the order of description on the base material. In the dipping process, the substrate is dipped in a butanol solution in which tantalum oxide of Ta; I = 0.3: 0.7 and iridium chloride are dissolved. In the drying step, the immersed substrate is dried in air at 60 ° C. for 10 minutes. In the firing step, the dried substrate is fired in air at 45 ° C. for 10 minutes. The anode 30 is manufactured through these steps. In this case, the catalyst carrying amount coated on the surface of the base material having a mesh structure is manufactured such that, for example, a composite oxide of iridium oxide (IrO ₂ ) -tantalum oxide (Ta ₂ O) is 0.01 mg / cm ^2. Is done. In this adjustment, the amount of catalyst supported can be determined from the change in mass of the manufactured anode.

  The cathode 31 will be described. The cathode 31 is preferably composed of a cathode catalyst layer 32, a conductive porous layer (MPL) 33, and a gas diffusion layer (GDL) 34.

  The cathode catalyst layer 32 is formed in a sheet shape and is bonded to one surface of the porous layer 33. The gas diffusion layer 34 is formed in a sheet shape from a conductive material having air permeability or liquid permeability. The gas diffusion layer 34 is bonded to the other surface of the conductive porous layer 33, and the porous layer 33 is sandwiched between the cathode catalyst layer 32.

  The cathode catalyst layer 32 contains a catalyst (cathode catalyst) having an ability to reduce oxygen. The cathode catalyst layer 32 is preferably a porous layer formed of a cathode catalyst and a proton conductive binder. The cathode catalyst preferably has a form in which at least one of noble metal particles and noble metal alloy particles is supported on a conductive carrier.

  The noble metal particles are preferably composed of at least a noble metal selected from the group consisting of platinum Pt, ruthenium Ru, rhodium Rh, palladium Pd, and iridium Ir. However, this is not restrictive.

  When noble metal alloy particles are used as the cathode catalyst, it is possible to improve the dissolution resistance and activity of the cathode catalyst. Examples of such noble metal alloy particles include, but are not particularly limited to, the following description, alloys including only two or more kinds of noble metal elements, alloys including noble metal elements and other metal elements, and the like.

  The noble metal alloy particles can obtain a high catalytic activity effect. For this reason, noble metal alloy particles based on platinum Pt may be used. Specifically, an alloy of one or more noble metal elements and platinum Pt is preferable. The one or more noble metal elements include noble metals other than platinum Pt such as ruthenium Ru, rhodium Rh, palladium Pd, iridium Ir, and the like, for example, titanium Ti, vanadium V, chromium Cr, manganese Mn, iron Fe, cobalt Co, and nickel Ni. Selected from the group.

  Although the alloy composition of the noble metal alloy particles depends on the type of metal element to be alloyed, platinum (Pt) is 30 atomic% to 95 atomic%, and the metal element to be alloyed is 5 atomic% to 70 atomic%. Is preferred. Here, “alloy” is a general term for a plurality of metal elements, or those having metallic properties formed from metal elements and non-metal elements. Alloys include solid solutions that are completely dissolved, eutectics in which the component metal elements are independent at the crystal level, and intermetallic compounds that are bonded at a certain ratio at the atomic level. An alloy in the state of

  The conductive support of the cathode catalyst layer 32 carries noble metal particles and / or noble metal alloy particles (that is, at least one of these particles). This conductive carrier is selected in consideration of electron conductivity, gas diffusibility, adhesion to the cathode catalyst, and the like. For example, carbon black, activated carbon, graphite and the like can be used, and a nanocarbon material can also be used. Examples of carbon black include furnace black, channel black, acetylene black, Vulcan (registered trademark; Cabot Corporation), and ketjen black. The nanocarbon material may be any of a fiber shape, a tube shape, a coil shape, and a sheet shape, for example.

The specific surface area of the conductive support, the cathode catalyst may be a sufficient to highly dispersed carrier, specifically ^a 50m ² / g~1400m 2 / g. If the specific surface area is less than 50 m ² / g, the dispersibility of the cathode catalyst in the conductive support may be reduced, and sufficient catalytic action may not be obtained. On the other hand, if the specific surface area exceeds 1400 m ² / g, the effective utilization rate of the cathode catalyst may decrease, and sufficient catalyst performance may not be obtained. Therefore, the specific surface area of the conductive support may be in the range, preferred specific surface area of ^{80m 2} / ^g~1200m 2 / g, still more preferably a specific surface area of 100m ² / g~1000m ² / g.

  When the noble metal particles or the noble metal alloy particles are used as the cathode catalyst in the cathode catalyst layer 32 in which the cathode catalyst is supported on the conductive support, the noble metal particles or the noble metal alloy particles are supported on the same conductive material that forms the conductive support. Alternatively, it may be supported on a different conductive material forming a conductive carrier. Similarly, when both the noble metal particles and the noble metal alloy particles are used as the cathode catalyst in the cathode catalyst layer 32 in which the cathode catalyst is supported on the conductive carrier, the noble metal particles and the noble metal alloy particles have the same conductivity as the conductive carrier. It may be carried on a material or may be carried on a different conductive material forming a conductive carrier.

  In the cathode catalyst layer 32 formed by supporting at least one of noble metal particles or noble metal alloy particles as a cathode catalyst on a conductive support, the loading amount of the cathode catalyst is 10 wt% with respect to the total mass of the cathode catalyst layer 32. % To 90 wt% is preferable.

  When the loading amount of the cathode catalyst is less than 10 wt%, the catalyst activity per unit mass is lowered and the desired catalyst performance is lowered. This is not preferable because a large amount of the cathode catalyst is required to obtain the desired catalyst performance. Moreover, it is not preferable in that the diffusibility of the reaction characteristics in the cathode catalyst layer 32 is lowered.

  On the contrary, when the loading amount of the cathode catalyst exceeds 90 wt%, the degree of dispersion of the cathode catalyst on the conductive support is lowered. As a result, the catalyst performance is not sufficiently improved while the amount of the cathode catalyst supported is increased, and the cost of the cathode catalyst layer 32 is increased, which is not preferable.

  Accordingly, the supported amount of the cathode catalyst may be in the above range, the preferable supported amount is 20 wt% to 80 wt%, and the more preferable supported amount is 30 wt% to 70 wt%.

  When the catalyst particles of the cathode catalyst are nanoparticles, the highest activity can be obtained. The average particle size of the catalyst particles is desirably 10 nm or less. If the average particle size 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. When the average particle diameter of the catalyst particles 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 cathode catalyst can be produced using a solution method such as an impregnation method, a precipitation method, a colloid method, or a dry method such as a sputtering method. Specific examples of the method for producing the cathode catalyst are as follows.

  First, acetylene black is dispersed in an aqueous solution in which chloroplatinic acid is dissolved, and sodium bicarbonate is added dropwise thereto to adjust the pH of the solution to 7-8. As a result, Pt oxide was supported on acetylene black. Next, 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 atmosphere). Thereafter, the obtained solid was pulverized and reduced with hydrogen gas to carry Pt on acetylene black. The amount of Pt supported was 10 wt%.

  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 be evaluated by a powder sample obtained by cutting out a part of the catalyst layer used for the synthesized catalyst or the cathode of the oxygen reduction cell. 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. 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 cathode catalyst can be calculated from the crystallite diameter obtained from the half width of the strongest diffraction peak of the catalyst in X-ray diffraction analysis (XRD). The Scherrer equation was used for the calculation.

  The composition analysis of the noble metal catalyst contained in the cathode catalyst layer 32 can be evaluated by inductively coupled plasma emission spectroscopy (ICP).

The analysis sample can also be evaluated by a powder sample obtained by cutting out a part of the catalyst layer used for the electrode catalyst or the cathode of the oxygen reduction cell. 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, pretreatment can be performed by an alkali melting method having a strong dissolving power by high-temperature melting. In this dissolution method, sodium carbonate (Na ₂ CO ₃ ), sodium peroxide (Na ₂ O ₂ ), a mixture of sodium hydroxide and sodium nitrate (NaOH + NaNO ₃ ), or the like can be used as the decomposition agent.

  The cathode catalyst layer 32 in the cathode 31 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 32 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 support and the proton conductive binder is such that the mass ratio (P / C) of the proton conductive binder (P) is 0.05 to 0.5 with respect to the total mass (C) of the catalyst layer. A range is desirable. If the mass ratio P / C is greater than 0.5, the continuity of the catalyst-supporting carbon may be reduced and the conductivity may be lowered.

  The cathode catalyst layer 32 is formed immediately above the conductive porous layer (MPL) 33 joined to the gas diffusion layer (GDL) 34. As the GDL with MPL, a commercially available product can be appropriately selected and used.

  The gas diffusion layer 34 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) 33 is a porous layer made of a water repellent and carbon particles.

  As the water repellent used for the gas diffusion layer 34 and the conductive porous layer 33, a fluororesin is selected. For example, polytetrafluoroethylene (PTFE), ethylene tetrafluoride-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin (PFA), and the like can be used.

  As the carbon particles used for the conductive porous layer 33, the same carbon particles as those described above can be used.

  The cathode catalyst layer 32 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 34 and dried. Thereby, the cathode catalyst layer 32 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 31, 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 31. The catalyst amount of Pt determined from the composition of the catalyst slurry and the weight change of GDL with MPL was 1 mg / cm ² .

  The polymer electrolyte membrane 35 will be described. The electrolyte membrane 35 is preferably a thin film made of a perfluorocarbon sulfonic acid polymer because of its high proton conductivity. Examples of the electrolyte membrane 35 include fluororesins having a sulfonic acid group such as Nafion (registered trademark: manufactured by DuPont), Flemion (registered trademark: manufactured by Asahi Kasei Co., Ltd.), Aciplex (registered trademark: manufactured by Asahi Glass Co., Ltd.), and the like. Can be mentioned. However, it is not limited to these, The electrolyte membrane 35 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 35 is preferably 10 μm to 150 μm in consideration of the membrane resistance. A more preferable film thickness is 30 μm to 100 μm.

  The vaporization layer 38 of the electrode assembly 36 will be described. The vaporization layer 38 is formed of a porous material, and is provided to convert water (liquid) supplied from the anode chamber 42 into water vapor and supply the water vapor to the anode 30. Therefore, the vaporization layer 38 is a gas-liquid separation layer. The vaporized layer 38 is formed of a material having excellent thermal conductivity, in other words, a material having high thermal responsiveness, for example, a carbon porous body such as carbon paper, carbon cloth, or carbon felt.

  The vaporization layer 38 contains a water repellent that imparts a water repellent function. The water repellent function of the vaporized layer 38 prevents water (liquid) supplied to the anode chamber 42 from coming into direct contact with the anode 30. Examples of the water repellent include fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer resin (FEP), and tetrafluoroethylene perfluoroalkyl-vinyl ether copolymer resin (PFA). Can be preferably used.

  There is no guarantee that the treatment of the water repellent (fluororesin) on the carbon porous body will be performed uniformly. For this reason, when the content of the fluororesin is less than 5 wt (mass)%, the water repellent function in the vaporization layer 38 becomes insufficient, and the water (liquid) in the anode chamber 42 passes through the vaporization layer 38 to the anode 30. There is a risk of reaching. When the content of the fluororesin exceeds 50 wt (mass)%, the water repellent (fluororesin) is filled in the pores of the carbonaceous porous body, and the pore volume is reduced. As a result, the amount of water vapor supplied from the vaporized layer 38 to the anode 30 decreases, making it difficult to obtain a sufficient current density necessary for the oxygen reduction operation, and thus the rate of oxygen reduction may be reduced.

  Therefore, the content of the water repellent (fluorine resin) in the carbon porous body is preferably 5 wt% to 50 wt%, more preferably 8 wt% to 40 wt%, and 10 wt% to 35 wt%. Is more preferable.

In order for the vaporization layer 38 to supply water (water vapor) necessary for the operation of the oxygen reduction cell 23 to the anode 30 without excess or deficiency, the pore diameter, porosity, and layer thickness of the vaporization layer 38 are set as follows. Has been.
In the pore distribution with the pore diameter of the vaporization layer 38 as the horizontal axis and the pore volume of the vaporization layer 38 as the vertical axis, if the median diameter of the pores is less than 15 μm, the vaporization layer 38 to the anode 30 The supply amount of water vapor is less than the appropriate amount, and it becomes difficult to obtain a sufficient current density necessary for the oxygen reduction operation, and there is a possibility that the rate of oxygen reduction becomes slow. Further, since the treatment with the water repellent agent is not necessarily performed uniformly on the carbon porous body, it is conceivable that the median diameter of the pores exceeds 60 μm when the treatment is insufficient. In this case, water (liquid) in the anode chamber 42 may reach the anode 30 through the vaporization layer 38 without becoming water vapor.

  Therefore, the median diameter of the pore diameter is preferably 15 μm to 60 μm, more preferably 20 μm to 55 μm, and even more preferably 25 μm to 50 μm.

  If the porosity of the vaporization layer 38 is less than 40%, the amount of water vapor supplied from the vaporization layer 38 to the anode 30 is less than the appropriate amount, and it becomes difficult to obtain a sufficient current density necessary for the oxygen reduction operation. Therefore, the rate of oxygen reduction may be slow. On the other hand, if the porosity exceeds 90%, the strength of the vaporized layer 38 is insufficient, and there is a risk of trouble in process management such as water repellent treatment.

  Therefore, the porosity is preferably 40% to 90%, further preferably 45% to 85%, and more preferably 50% to 80%.

  When the thickness of the carbonized porous body is less than 100 μm, there is a possibility that the strength of the vaporized layer 38 is insufficient and the process management such as the water repellent treatment may be troubled. Also, if the thickness of the porous body exceeds 500 μm, the amount of water vapor supplied from the vaporization layer 38 to the anode 30 will be less than the appropriate amount, and it will be difficult to obtain a sufficient current density necessary for the oxygen reduction operation. The rate of oxygen reduction may be slow. Therefore, the thickness of the vaporized layer 38 is preferably 100 μm to 500 μm, more preferably 110 μm to 450 μm, and even more preferably 130 μm to 400 μm. In addition, the thickness of the vaporization layer 38 is obtained by dividing the area of the vaporization layer 38 into 16 regions and measuring the thickness of the center position of each region to obtain an average value of the measured values.

  In addition, the pore diameter and porosity of the vaporization layer 38 in the embodiment can be evaluated using a mercury porosimeter. A mercury porosimeter is an apparatus for evaluating the size of pores in a porous material by a mercury injection method. For this evaluation apparatus, “Autopore 9520 type” manufactured by Shimadzu Corporation can be used.

  The sample of the vaporized layer measured with a mercury porosimeter was dried under reduced pressure at room temperature for several hours, then cut into strips of about 1.2 × 2.5 cm, and 0.07 g to 0.13 g was used as a standard cell. take. Using this sample, the pore diameter and the porosity are measured under each condition of an initial pressure of about 5 kPa (about 0.7 psia, corresponding to a pore diameter of about 250 μm). At this time, the mercury parameters are set to a mercury contact angle of 130 degrees and a mercury surface tension of 485 dynes / cm. The pore volume is measured by detecting the pressure in the measurement process and the amount of mercury injected with a capacitance detector. Then, by modeling the pores into a cylindrical shape, the maximum diameter, bulk density, apparent density, porosity, and pore distribution can be obtained. The relationship between the pressure and the pore diameter through which mercury can enter at that pressure is expressed by the Washburn equation.

  An example of a specific method for manufacturing the vaporized layer 38 used in the embodiment will be described. First, carbon paper is immersed for 1 minute in a PTFE (polytetrafluoroethylene) -dispersed aqueous solution adjusted to a predetermined concentration and dried overnight at room temperature. Next, the carbon paper thus dried is fired at 380 ° C. for 10 minutes in an argon atmosphere. Thereby, the vaporized layer 38 made of carbon paper subjected to water repellent treatment is created. In addition, the manufacturing method of this vaporization layer 38 is not specifically limited.

  The content of the water repellent (fluororesin) in the produced vaporized layer 38 can be evaluated by measuring a decrease in weight due to combustion. Alternatively, the fluororesin content of the vaporized layer 38 can also be evaluated by measuring weight loss due to combustion of carbon or fluororesin by differential thermal-thermogravimetric simultaneous measurement (TG-DTA).

  By selecting a structure in which a porous carbon particle layer (MPL) having air permeability or liquid permeability is laminated on the vaporization layer 38, the air permeability and liquid permeability to the anode 30 can be made uniform. . By making the air permeability and liquid permeability to the anode 30 uniform, the oxidation reaction of water on the anode catalyst proceeds smoothly, and an increase in electrolysis voltage can be suppressed. Therefore, it is desirable that the porous carbon particle layer is disposed on the anode 30 side.

  On the other hand, even if the porous carbon particle layer is disposed on the back surface side of the anode 30, liquid water can be uniformly diffused into the vaporized layer 38 through the porous carbon particle layer. Thereby, the air permeability and liquid permeability to the anode 30 are further promoted. Therefore, it is possible to dispose the porous carbon particle layer on both surfaces of the vaporization layer 38, but the disposition of the porous carbon particle layer is appropriately determined in consideration of the required cost, the performance of the oxygen reduction cell 23, and the life. Just choose.

  The porous carbon particle layer is a porous layer composed of a water repellent and carbon particles. A fluororesin is selected as the water repellent material. For example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer resin (PFA) ) Etc. can be used. As the carbon particles, the same carbon particles as those described above can be used.

  Since the porous carbon particle layer has a water-repellent function necessary for making air permeability and liquid permeability uniform, it appropriately contains a fluororesin. When the content of the fluororesin is less than 5 wt%, the water repellent function becomes insufficient, and liquid water may stagnate inside the porous carbon particle layer and block the pores. When the content of the fluororesin exceeds 50 wt%, the fluororesin fills the pores of the porous carbon particle layer and decreases the pore volume. As a result, the amount of water vapor supplied to the anode 30 is reduced, and the current density necessary for the oxygen reduction operation cannot be sufficiently obtained, so that the oxygen reduction rate may be delayed. Therefore, the fluororesin content is desirably 5 wt% to 50 wt%, preferably 8 wt% to 40 wt%, and more preferably 10 wt% to 35 wt%.

  The porous carbon particle layer has an appropriate thickness for uniform air permeability and liquid permeability. If the thickness of the porous carbon particle layer is less than 10 μm, it is difficult to obtain a uniform porous carbon particle layer due to the unevenness of the vaporized layer 38 as a base material, and air permeability and liquid permeability are made uniform. Becomes difficult. On the other hand, if the thickness of the porous carbon particle layer is larger than 100 μm, the amount of water vapor supplied to the anode 30 is reduced and the current density necessary for the oxygen reduction operation cannot be obtained sufficiently, so that the oxygen reduction rate becomes slow. There is a fear. Accordingly, the thickness of the porous carbon particle layer is desirably 10 μm to 100 μm, preferably 15 μm to 80 μm, and more preferably 20 μm to 50 μm.

The thickness of the porous carbon particle layer was an average value obtained by observing the cross section of the vaporized layer 38 with a scanning electron microscope and observing at least five locations. The measurement conditions were as follows.
Apparatus: JXA-8100 manufactured by JEOL Ltd.
SEM observation conditions: acceleration voltage: 15 kV, magnification: 400 times As a specific example of a method for producing the vaporized layer 38 on which the porous carbon particle layer used in the embodiment is laminated, a known method can be used.

  For example, first, carbon particles and a PTFE-dispersed aqueous solution are mixed and dispersed in an organic solvent such as water or alcohol to a predetermined concentration and composition to form a slurry. Next, this slurry is applied to a vaporized layer prepared in advance and dried, and this is fired in an argon atmosphere at 380 degrees for 10 minutes to produce a vaporized layer 38 on which a porous carbon particle layer is laminated. . The dispersion method in this production method is not particularly limited, and a dissolver, a ball mill, a homogenizer, or the like can be used. A coating method in the production method is not particularly limited, and can be performed by a casting method, a spray method, or the like. The vaporized layer 38 on which a commercially available porous carbon particle layer is laminated can be appropriately selected in consideration of required cost, device performance, and lifetime.

  The oxygen reduction stack 22 described above can be manufactured, for example, by the following method.

First, the anode 30, the cathode 31, and the electrolyte membrane 35 of the oxygen reduction cell 23 are joined (thermocompression bonding) using an apparatus capable of heating and pressurizing. 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 from which the binding property of an electrode and the electrolyte membrane 35 is obtained, and is generally 100 to 400 degreeC. The pressing pressure depends on the hardness of the electrode used, but is ^{usually, 5kg / cm 2 ~200kg / cm} 2. Next, the obtained oxygen-reducing cell 23 is combined with a cathode current collecting layer 39 serving as an electrode, a vaporization layer 38 of an electrode assembly 36, and an anode current collecting layer 37 serving as an electrode. Thereby, the oxygen reduction stack 22 can be obtained.

  The oxygen reduction device 21 is disposed in the refrigerator main body 2 so that the oxygen reduction cell 23 can react with oxygen in the oxygen reduction chamber 3. As a specific example, the oxygen reduction device 21 is accommodated in the recess 20 of the refrigerator main body 2 with the air intake 47 formed in the second container member 45 facing the through hole 2a of the refrigerator main body 2 as shown in FIG. ing. As a result, the cathode chamber 46 and the oxygen reduction chamber 3 are communicated with each other via the through hole 2 a, and the cathode 31 of the oxygen reduction cell 23 can react with oxygen in the oxygen reduction chamber 3.

  As shown in FIG. 2, the anode current collecting layer 37 of the oxygen reducing cell 23 is electrically connected to the positive electrode of the power source 24, and the cathode current collecting layer 39 of the oxygen reducing cell 23 is electrically connected to the negative electrode of the power source 24. It is connected. The power source 24 applies a voltage or current between the anode 30 and the cathode 31 of the oxygen reduction cell 23. In FIG. 2, reference numeral 29 indicates a detector. The detector 29 detects a voltage or current applied to the oxygen reduction cell 23 and is, for example, a voltmeter.

  Each time the opening / closing member 5 of the refrigerator 1 is opened, the oxygen concentration in the oxygen reduction chamber 3 becomes the same as the oxygen concentration in the atmosphere. For this reason, every time the opening / closing member 5 is closed, the oxygen reduction device 21 is operated so that the oxygen reduction chamber 3 has a target low oxygen concentration. Next, a reaction (oxygen reduction reaction) in which oxygen in the oxygen reduction chamber 3 is reduced by the operation of the oxygen reduction device 21 will be described.

  In a state where water (liquid) is supplied from the water intake port 43 to the anode chamber 42, a DC voltage is applied from the power source 24 between the anode 30 and the cathode 31 of the oxygen reduction cell 23 under the control of the controller 29 to reduce the amount. The oxygen cell 23 is operated. Since the vaporized layer 38 of the electrode assembly 36 is subjected to water repellent treatment between the anode 30 and the anode chamber 42, water (liquid) in the anode chamber 42 is directly applied to the anode 30 of the oxygen reduction cell 23. There is no contact.

As the oxygen reduction cell 23 is operated, water (H ₂ O) is electrolyzed (oxidized) on the surface of the anode 30, and water (liquid) is generated on the surface of the cathode 31.

That is, oxygen (O ₂ ), protons (H ⁺ ), and electrons (e ⁻ ) are generated by the electrolysis reaction of water at the anode 30.

This reaction is represented by the formula (1) of 2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ . Oxygen (O ₂ ) generated by such oxidation of water is discharged out of the anode chamber 42 through the oxygen outlet 44.

On the other hand, the generated proton (H ⁺ ) moves from the anode 30 to the cathode 31 through the electrolyte membrane 35. At the same time, the generated electrons (e ⁻ ) move to the cathode 31 through an external circuit including the power source 24 and the like.

Air (oxygen and nitrogen) in the oxygen-reducing chamber 3 is supplied to the cathode chamber 46 through an air intake 47. Therefore, at the cathode 31, oxygen (O ₂ ) in the oxygen reduction chamber 3 reacts with protons (H ⁺ ) and electrons (e ⁻ ) supplied to the cathode 31 to generate water (liquid).

This reaction is represented by the formula (2) of O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O. As described above, oxygen in the air is converted into water by the reduction reaction of oxygen at the cathode 31, so that the oxygen concentration in the oxygen reduction chamber 3 is reduced. 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.

  Since the oxygen-reducing reaction described above is an exothermic reaction, the temperature of the oxygen-reducing cell 23 and the cell peripheral member joined to the cell so as to conduct heat rises with the oxygen-reducing reaction. Although the calorific value of the oxygen reduction cell 23 differs depending on the density of the current passed through the oxygen reduction cell 23 for the oxygen reduction reaction, it was confirmed that the oxygen reduction cell 23 rose by about 30 ° C. due to its operation. Along with this, the temperature of the vaporization layer 38 having high thermal responsiveness to the oxygen reduction cell 23 rises close to the temperature of the oxygen reduction cell 23.

  For this reason, in the oxygen reduction reaction, water (liquid) supplied from the anode chamber 42 through the anode current collecting layer 37 to the vaporized layer 38 is heated by the vaporized layer 38 and converted into water vapor to the anode 30. Supplied.

The pressure of water vapor supplied to the anode 30 is defined by the saturated water vapor pressure. As a result, water molecules are inhibited from moving from the anode 30 through the electrolyte membrane 35 to the cathode 31 together with protons (H ⁺ ).

  In this way, excess water is suppressed from being transferred from the anode 30 to the cathode 31 to the cathode 31 that generates water (liquid) by the reaction in the formula (2). Therefore, excessive stagnation of water (liquid) at the cathode 31 can be suppressed. At the same time, the water (liquid) in the anode chamber 42 is restrained from being transferred as excess water from the anode 30 to the cathode 31, so that the water required for the reaction at the anode 30 is reduced with respect to the anode 30. There is no risk of supply shortage.

  As the stagnation of water (liquid) at the cathode 31 is suppressed, the cathode flood phenomenon is less likely to occur. For this reason, it is suppressed that water (liquid) obstruct | occludes the pore of the cathode catalyst layer 32, and the supply of the oxygen in the oxygen reduction chamber 3 to the cathode catalyst layer 32 is prevented. Therefore, since the voltage required for the oxygen reduction reaction can be prevented from becoming excessive, it is possible to suppress a decrease in the performance of the oxygen reduction device 21.

  In the oxygen reduction operation, water (liquid) supplied to the anode chamber 42 may contain impurity ions such as metal ions. In this case, as described above, the water in the anode chamber 42 is heated by the vaporization layer 38 before reaching the anode 30 and is supplied to the anode 30 as water vapor. Thus, the vaporization layer 38 exhibits ion trap performance because the vaporization layer 38 distills water.

Thereby, impurity ions such as metal ions are prevented from accumulating in the electrolyte membrane 35, so that the proton (H ⁺ ) conductivity in the electrolyte membrane 35 is suppressed from decreasing. As a result, the electrical resistance of the oxygen reduction cell 23 is increased, and an excessive increase in the voltage required for the oxygen reduction reaction is suppressed, so that a decrease in performance of the oxygen reduction device can be suppressed.

  Furthermore, in the operation of the oxygen reduction device 21, movement of excess water molecules from the anode 30 to the cathode 31 can be suppressed by supplying water vapor to the anode 30 by the vaporization layer 38 as described above. This suppresses the electrolyte membrane 35 from being swollen with water molecules during the oxygen reduction operation. On the other hand, the electrolyte membrane 35 is heated by the residual heat of the oxygen reduction cell 23 with the stop operation of the oxygen reduction device 21. Nevertheless, changes in the dimensions of the electrolyte membrane 35 due to swelling and drying of the electrolyte membrane 35 are suppressed. Therefore, it is possible to suppress peeling at the joint surface between the electrolyte membrane 35 and the anode 30 of the oxygen reduction cell 23, and to suppress a decrease in durability of the oxygen reduction device 21.

  In the oxygen reduction device 21, the amount of water vapor supplied to the anode 30 is affected by the vaporization layer 38. For this reason, an electric heater may be attached to the outside of the oxygen reduction stack 22, specifically, the oxygen reduction container 25, and the temperature of the oxygen reduction stack 22 having the oxygen reduction cell 23 may be controlled by the heat generated by the heater. Thereby, the amount of water vapor supplied to the anode 30 can be stably controlled.

  Hereinafter, an embodiment of the oxygen reduction device 21 will be described.

Example 1
In Example 1, the vaporized layer 38 is obtained by the following manufacturing method. First, carbon paper having a thickness of 180 μm is immersed in an aqueous PTFE dispersion for 1 minute, and then dried overnight at room temperature. Next, the carbon paper thus dried is baked at 380 ° C. for 10 minutes in an argon atmosphere. To do. As a result, a vaporized layer 38 made of carbon paper having a PTFE content of 5 wt% as a fluororesin was obtained. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 70%.

The oxygen reduction stack 22 in Example 1 was obtained by the following manufacturing method. An anode 30 made by the above-described manufacturing method and having a size of 20 cm ² is prepared. A cathode 31 made by the above-described manufacturing method and having a size of 12 cm ² is prepared. Along with this, an electrolyte membrane (registered trademark; Nafion, manufactured by DuPont) 35 having a thickness of 50 μm and a size of 30 cm ² is prepared. The anode 30, the cathode 31, and the electrolyte membrane 35 were heated and pressurized with a hot press machine and joined (thermocompression bonding) to obtain the oxygen-reducing cell 23. Hot pressing was performed under the conditions of a temperature of 160 ° C., a pressure of 20 kg / cm ² , and a pressing time of 3 minutes. The oxygen reduction stack 22 is obtained by preparing and combining the elements of the oxygen reduction cell 23 and other elements, that is, the vaporization layer 38, the anode current collection layer 37, and the cathode current collection layer 39.

  Evaluation in Example 1 is as follows.

  The oxygen reduction stack 22 was sandwiched between the first container member 41 and the second container member 45, and these were connected to create the oxygen reduction container 25. Thereby, the oxygen reduction device 21 is created. The anode current collecting layer 37 and the cathode current collecting layer 39 of this device were connected to the power source 24. In the evaluation of the oxygen reduction device 21, the anode chamber 42 of the first container member 41 containing the anode 30 is filled with water (liquid), and the cathode chamber 46 of the second container member 45 containing the cathode 31 is filled. Air was supplied by spontaneous breathing.

In such a state, a voltage was applied to the oxygen reduction cell 23 by the power source 24 to control the reaction current to be a constant current. In this constant current control, for example, a voltage applied to the oxygen reduction cell 23 is detected by a voltmeter 27 (see FIG. 2) as voltage detection means, and the controller 29 determines the output voltage of the power source 24 based on the detection information. It was done by controlling. By this constant current control, for example, a constant current of 0.2 A / cm ² was applied to the oxygen reduction cell 23 to cause the oxygen reduction reaction, and the electrolytic voltage was measured 1 hour and 1000 hours after the start of the reaction. The results are shown in Table 1.

(Example 2)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Tables 1 to 4.

(Example 3)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 30 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 60%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 1.

(Example 4)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 50 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 55%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 1.

(Example 5)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 1 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 75%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 1.

(Example 6)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 60 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 45%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 1.

(Comparative Example 1)
An oxygen reduction device without a vaporization layer was created. Therefore, in the oxygen reduction device of Comparative Example 1, the anode current collecting layer is directly joined to the anode. Using the oxygen reduction apparatus of Comparative Example 1, the oxygen reduction reaction was performed in the same manner as in Example 1, and the electrolysis voltage was measured 1 hour and 1000 hours after the start of the reaction. The results are shown in Table 1.

  As shown in Table 1, the oxygen reduction devices of Examples 1 to 4 having a vaporized layer having a fluororesin content of 5 wt% or more and less than 50 wt% were provided with a vaporized layer having a fluororesin content of 1 wt%. Compared with the oxygen reduction device of Example 5, the oxygen reduction device of Example 6 having a vaporization layer with a fluororesin content of 60 wt%, and the oxygen reduction device of Comparative Example 1 having no vaporization layer, 1000 hours later It was confirmed that the electrolysis voltage can be kept low. That is, when the fluorine content of the vaporized layer 38 is in the range of 5 wt% to 50 wt%, the amount of water vapor supplied from the vaporized layer 38 to the anode 30 is appropriate.

  As a result, even if electrolysis is performed for a long time, the amount of water that permeates the cathode 31 is limited, so that the water generated by the electrolysis is smoothly discharged from the cathode 31 and maintains a low electrolysis voltage even after 1000 hours. can do. From this, it can be seen that the fluorine content of the vaporization layer 38 that can supply the amount of water vapor necessary for the operation of the oxygen reduction cell 23 to the anode 30 without excess or deficiency is preferably 5 wt% to 50 wt%. It has become clear that the oxygen reduction device that has been removed and the oxygen reduction device without the vaporization layer are not suitable for long-time operation.

(Example 7)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 60 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 2.

(Example 8)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 45 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 2.

Example 9
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 15 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 2.

Example 10
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 100 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 2.

Example 11
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 10 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 2.

  As shown in Table 2, the oxygen reduction device of Example 2 provided with a vaporization layer having a median diameter of pores of 15 μm or more and 60 μm, and the oxygen reduction device provided with the vaporization layer of Examples 7 to 9 are median. Compared with the oxygen reduction device of Example 10 provided with a vaporization layer having a diameter of 100 μm and the oxygen reduction device of Example 10 provided with a vaporization layer having a median diameter of 10 μm, the electrolysis voltage after 1000 hours is kept low. It was confirmed that it could be done. That is, when the median diameter of the vaporized layer 38 is in the range of 15 μm to 60 μm, the amount of water vapor supplied from the vaporized layer 38 to the anode 30 is appropriate.

  As a result, even if electrolysis is performed for a long time, the amount of water that permeates the cathode 31 is limited, so that the water generated by the electrolysis is smoothly discharged from the cathode 31 and maintains a low electrolysis voltage even after 1000 hours. can do. From this, it is understood that the pore diameter of the vaporized layer 38 that can supply the amount of water vapor necessary for the operation of the oxygen reduction cell 23 to the anode 30 without excess or deficiency is such that the median diameter is 15 μm to 60 μm. It became clear that an oxygen reduction device outside this range and an oxygen reduction device without a vaporized layer are not suitable for long-time operation.

(Example 12)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 90%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 3.

(Example 13)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 75%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 3.

(Example 14)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 40%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 3.

(Example 15)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 180 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 30%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 3.

  As shown in Table 3, the oxygen reduction device of Example 2 and the oxygen reduction devices of Examples 12 to 14 having a vaporization layer 38 having a porosity of 40% or more and less than 90% have a porosity of 30%. It was confirmed that the electrolysis voltage after 1000 hours can be kept low as compared with the oxygen reduction device of Example 15 provided with a certain vaporization layer. That is, if the porosity of the vaporized layer 38 is in the range of 40% to 90%, the amount of water vapor supplied from the vaporized layer 38 to the anode 30 is appropriate.

  As a result, even if electrolysis is performed for a long time, the amount of water that permeates the cathode 31 is limited, so that the water generated by the electrolysis is smoothly discharged from the cathode 31 and maintains a low electrolysis voltage even after 1000 hours. can do. From this, it is understood that the porosity of the vaporized layer 38 that can supply the water vapor amount necessary for the operation of the oxygen reduction cell 23 to the anode 30 without excess or deficiency is preferably 40% to 90%. It became clear that the oxygen reduction device and the oxygen reduction device without the vaporization layer are not suitable for long-time operation.

(Example 16)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 110 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 4.

(Example 17)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 270 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 4.

(Example 18)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 360 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 4.

(Example 19)
In the same manner as in Example 1, a vaporized layer 38 made of carbon paper having a thickness of 600 μm and a PTFE content of 10 wt% was produced. As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having this vaporized layer 38 was prepared by performing the same operation as in Example 1, and the oxygen reduction reaction was performed by the same operation as in Example 1. After 1 hour and 1000 hours from the start of the reaction, The electrolysis voltage of was measured. The results are shown in Table 4.

  As shown in Table 4, the oxygen reduction device of Example 2 and the oxygen reduction devices of Examples 16 to 18 having a vaporization layer 38 having a thickness of 100 μm or more and less than 500 μm are vaporized layers having a thickness of 600 μm. It was confirmed that the electrolysis voltage after 1000 hours can be kept low compared with the oxygen reduction device of Example 19 provided with That is, when the thickness of the vaporized layer 38 is in the range of 100 μm to 500 μm, the amount of water vapor supplied from the vaporized layer 38 to the anode 30 is appropriate.

  As a result, even if electrolysis is performed for a long time, the amount of water that permeates the cathode 31 is limited, so that the water generated by the electrolysis is smoothly discharged from the cathode 31 and maintains a low electrolysis voltage even after 1000 hours. can do. From this, it is understood that the thickness of the vaporized layer 38 that can supply the amount of water vapor necessary for the operation of the oxygen reduction cell 23 to the anode 30 without excess or deficiency is preferably 100 μm to 500 μm. The oxygen device and the oxygen reduction device without the vaporized layer are not suitable for long-time operation.

(Example 20)
The water supplied to the anode 30 was adjusted so as to contain 500 ppm of metal impurity ions such as Na, Ca, Al, Fe, Ni, Cu, and Zn, and this was supplied to an oxygen reduction device similar to that in Example 2 for evaluation. did. The results are shown in Table 5.

(Comparative Example 2)
The water containing impurity ions prepared in Example 20 was supplied to the oxygen reduction apparatus similar to Comparative Example 1 and evaluated. The results are shown in Table 5.

  As shown in Table 5, the oxygen reduction apparatus of Example 2 did not change the capacity of the oxygen reduction apparatus even when water (liquid) containing impurity ions was supplied as shown in Example 20. On the other hand, as shown in Comparative Example 2, when water containing impurity ions is supplied to the oxygen reduction device of Comparative Example 1 having no vaporized layer, the electrolytic voltage immediately increases and the performance of the oxygen reduction device decreases. It was confirmed.

  That is, in the oxygen reduction device of Comparative Example 2, if impurity ions such as metal ions are contained in the water supplied to the anode, it accumulates in the polymer electrolyte membrane and the conductivity of hydrogen ions decreases. Resulting in. On the other hand, the oxygen reduction device of Example 2 and the oxygen reduction device of Example 20 distill water supplied to the anode 30 by the vaporization layer 38 provided therein, and supply water vapor to the anode 30. For this reason, impurity ions are not accumulated in the electrolyte membrane 35 of the oxygen reduction cell 23. Therefore, the electrolytic voltage after 1000 hours can be maintained in a low state.

(Example 21)
(Manufacture of the vaporization layer 38 which laminated | stacked the porous carbon particle layer)
The carbon powder and the PTFE dispersion aqueous solution were mixed with the isopropyl alcohol aqueous solution and stirred to prepare a carbon slurry. In the same manner as in Example 1, a vaporized layer made of carbon paper having a thickness of 180 μm and a PTFE content of 5 wt% was manufactured. The slurry was applied to the vaporized layer by a spray method and dried at 80 ° C. overnight. This was baked at 380 ° C. for 10 minutes in an argon atmosphere to obtain a vaporized layer 38 in which a porous carbon particle layer containing 5% PTFE was laminated to a thickness of 20 μm.

  As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 70%. An oxygen reduction device having the vaporized layer 38 was produced by performing the same operation as in Example 1. However, the vaporization layer 38 was installed so that the porous carbon particle layer was oriented to the oxygen-reducing cell side. Using this oxygen reduction apparatus, the oxygen reduction reaction was carried out in the same manner as in Example 1, and the electrolytic voltage was measured 1 hour and 1000 hours after the start of the reaction. The results are shown in Tables 6 and 8.

(Example 22)
In the same manner as in Example 21, a vaporized layer 38 in which a porous carbon particle layer containing 20% PTFE was laminated to a thickness of 20 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 21. The results are shown in Table 6.

(Example 23)
In the same manner as in Example 21, a vaporized layer 38 in which a porous carbon particle layer containing 50% PTFE was laminated to a thickness of 20 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 21. The results are shown in Table 6.

(Example 24)
In the same manner as in Example 21, a vaporized layer 38 in which a porous carbon particle layer containing 1% PTFE was laminated to a thickness of 20 μm was produced. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 21. The results are shown in Table 6.

(Example 25)
In the same manner as in Example 21, a vaporized layer 38 in which a porous carbon particle layer containing 60% PTFE was laminated to a thickness of 20 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 21. The results are shown in Table 6.

  As shown in Table 6, the oxygen reduction devices of Examples 21 to 23 in which the vaporized layers having a fluororesin content contained in the porous carbon particle layer of 5 wt% to 50 wt% are disposed in the porous carbon particle layer. The oxygen reduction device of Example 24 in which a vaporized layer having a fluororesin content of 1 wt% is arranged, or the oxygen reduction device of Example 25 in which a vaporized layer having a fluorocarbon resin content of a porous carbon particle layer of 60 wt% is arranged, Alternatively, it was confirmed that the electrolysis voltage after 1 hour or 1000 hours from the start of the reaction was lower than that of the oxygen reduction apparatus of Example 1 (see Table 1) that does not have a porous carbon particle layer in the vaporized layer.

  That is, according to the oxygen reduction devices of Examples 21 to 23, the amount of water vapor supplied from the vaporization layer 38 to the anode 30 is appropriate, and the air permeability and liquid permeability to the anode 30 are uniform. Thereby, the oxidation reaction of water on the anode catalyst proceeds smoothly, and an increase in electrolysis voltage is suppressed.

(Example 26)
(Manufacture of vaporized layer with porous carbon particle layer)
The carbon powder and the PTFE dispersion aqueous solution were mixed with the isopropyl alcohol aqueous solution and stirred to prepare a carbon slurry. This slurry was applied to the vaporized layer produced in Example 17 by a spray method and dried at 80 ° C. overnight. This was baked at 380 ° C. for 10 minutes in an argon atmosphere to obtain a vaporized layer 38 in which a porous carbon particle layer containing 25% PTFE was laminated to a thickness of 10 μm.

  As a result of evaluating the vaporized layer 38 by pore distribution measurement, the median diameter of the vaporized layer 38 was 35 μm, and the porosity was 65%. An oxygen reduction device having the vaporized layer 38 was produced by performing the same operation as in Example 1. However, the vaporization layer 38 was installed so that the porous carbon particle layer was oriented toward the killing cell. Using this oxygen reduction apparatus, the oxygen reduction reaction was carried out in the same manner as in Example 1, and the electrolytic voltage was measured 1 hour and 1000 hours after the start of the reaction. The results are shown in Table 7.

(Example 27)
In the same manner as in Example 26, a vaporized layer 38 in which a porous carbon particle layer containing 25% PTFE was laminated to a thickness of 100 μm was produced. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 26. The results are shown in Table 7.

(Example 28)
In the same manner as in Example 26, a vaporized layer 38 in which a porous carbon particle layer containing 25% PTFE was laminated to a thickness of 80 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 26. The results are shown in Table 7.

(Example 29)
In the same manner as in Example 26, a vaporized layer 38 in which a porous carbon particle layer containing 25% PTFE was laminated to a thickness of 5 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 26. The results are shown in Table 7.

(Example 30)
In the same manner as in Example 26, a vaporized layer 38 in which a porous carbon particle layer containing 25% PTFE was laminated to a thickness of 200 μm was manufactured. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction device was evaluated in the same manner as in Example 26. The results are shown in Table 7.

  As shown in Table 7, the oxygen reduction apparatuses of Examples 26 to 28 in which the vaporized layers having a porous carbon particle layer thickness of 10 to 100 μm are arranged are vaporized with a porous carbon particle layer thickness of 5 μm. The oxygen reduction device of Example 29 in which a layer is arranged, or the oxygen reduction device of Example 30 in which a vaporization layer having a thickness of a porous carbon particle layer of 200 μm is arranged, or an implementation in which the vaporization layer does not have a porous carbon particle layer Compared to the oxygen reduction device of Example 17 (see FIG. 4), it was confirmed that the electrolysis voltage was lower after 1 hour or 1000 hours from the start of the reaction.

  That is, according to the oxygen reduction devices of Examples 26 to 28, the amount of water vapor supplied from the vaporization layer 38 to the anode 30 is appropriate, and the air permeability and liquid permeability to the anode 30 are uniform. Thereby, the oxidation reaction of water on the anode catalyst proceeds smoothly, and an increase in electrolysis voltage is suppressed.

(Example 31)
A hypoxic device was produced and evaluated in the same manner as in Example 21. However, the vaporization layer 38 was installed so that the porous carbon particle layer was oriented on the surface opposite to the oxygen-reducing cell side. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction reaction was performed in the same manner as in Example 21 and in the same manner as in Example 1, and the electrolysis voltage after 1 hour and 1000 hours after the start of the reaction. Was measured. The results are shown in Table 8.

(Example 32)
(Manufacture of vaporized layer with porous carbon particle layer)
The carbon powder and the PTFE dispersion aqueous solution were mixed with the isopropyl alcohol aqueous solution and stirred to prepare a carbon slurry. This carbon slurry was applied to both sides of the vaporized layer produced in Example 1 by a spray method and dried at 80 ° C. overnight. This was baked at 380 ° C. for 10 minutes in an argon atmosphere, and a porous carbon particle layer containing 25% PTFE was formed on both sides of the vaporized layer with a thickness of 25 μm. Using the oxygen reduction device having the vaporized layer 38, the oxygen reduction reaction was performed in the same manner as in Example 1, and the electrolysis voltage was measured 1 hour and 1000 hours after the start of the reaction. The results are shown in Table 8.

  As shown in Table 8, Example 21 or Example 31 in which the arrangement relationship between the porous carbon particle layer laminated on the vaporization layer 38 and the anode 30 was changed, or the porous carbon particle layer on both sides of the vaporization layer 38 were obtained. It was confirmed that the formed Example 32 had a lower electrolysis voltage after 1 hour or 1000 hours from the start of the reaction as compared with Example 1 in which the vaporized layer 38 did not have a porous carbon particle layer.

  That is, according to the oxygen reduction device of Example 21, or Example 31 or Example 32, the amount of water vapor supplied from the vaporization layer 38 to the anode 30 is appropriate, and the air permeability and liquid flow to the anode 30 are also suitable. Uniformity. Thereby, the oxidation reaction of water on the anode catalyst proceeds smoothly, and an increase in electrolysis voltage is suppressed.

  Although one embodiment has been described as described above, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment 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 stack, 23 ... Hypoxic cell, 25 ... Hypoxic container, DESCRIPTION OF SYMBOLS 30 ... Anode, 31 ... Cathode, 32 ... Cathode catalyst layer, 35 ... Electrolyte membrane, 36 ... Electrode assembly, 37 ... Anode current collection layer, 38 ... Vaporization layer, 39 ... Cathode current collection layer

Claims (7)

An anode containing a catalyst for oxidizing supplied water vapor, a cathode having a cathode catalyst layer containing a catalyst for reducing oxygen, and an electrolyte membrane sandwiched between the cathode and the anode, and the electrolyte membrane comprises A hypoxic cell having proton conductivity;
An anode current collecting layer and a vaporization layer disposed on at least one of both surfaces of the anode current collection layer are provided with the anode sandwiched between the electrolyte membrane and supplied to the vaporization layer An electrode assembly for supplying water to the anode as water to be vaporized in the vaporization layer;
A cathode current collector layer disposed between the electrolyte membrane and the cathode;
An oxygen reduction device comprising:   The oxygen reduction apparatus according to claim 1, wherein the vaporization layer is a porous body made of carbon.   The oxygen reduction device according to claim 2, wherein the porosity of the vaporized layer is 40% or more and 90% or less.   In the pore distribution with the horizontal axis representing the pore diameter of the vaporized layer and the horizontal axis representing the pore volume of the vaporized layer, the median diameter of the pores of the vaporized layer is 15 μm to 50 μm, The oxygen reduction device according to claim 2 or 3.   5. The oxygen reduction device according to claim 2, wherein the vaporized layer has a thickness of 100 μm or more and 500 μm.   The oxygen-reducing layer according to any one of claims 2 to 5, wherein the vaporization layer contains a water repellent, and the content of the water repellent is 5 wt% or more and 50 wt%. apparatus. 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;
The oxygen reduction apparatus according to any one of claims 1 to 6, wherein a cathode of an oxygen reduction cell provided in the apparatus is disposed in the refrigerator main body so as to react with oxygen in the oxygen reduction chamber. Said oxygen reduction device;
The refrigerator characterized by comprising.

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