JPH05254803A - Electrochemical regulator for oxygen concentration using solid polyelectrolyte film - Google Patents

Abstract

PURPOSE:To improve the reverse diffusive migration of water by arranging the anode and the cathode sandwiching a solid polyelectrolyte film therebetween so as to provide the specific shortest distance. CONSTITUTION:The anode 1 for electrolyzing water and producing O2 is constructed of an anodic substrate 14 composed of an expanded metal of a Pt-plated Ti and an anodic catalyst layer 26 and the cathode 2 for producing water and consuming O2 is constructed of a cathodic substrate 15 and a cathodic catalyst layer 27. A solid polyelectrolyte film 3 having about 130mum thickness is sandwiched between the anodic substrate 14 and the cathodic substrate 15, hot pressed and bitten into both the electrode substrates to form the anodic catalyst layer 26 and the cathodic catalyst layer 27, which are arranged so as to provide <=50mum shortest distance 16 between both the electrodes. This eletrochemical regulator for the O2 concentration is capable of remarkably increasing the reverse diffusive migration of water from the cathode 2 into the anode 1. Water produced in the cathode 2 and water migrated into the cathode 2 are mostly returned through the solid polyelectrolyte film 3 to the anode 1. Thereby, a reservoir for the produced water, a reservoir for feed water and a pump can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical oxygen concentration regulator using a solid polymer electrolyte membrane. More specifically, electrochemical oxygen using a solid polymer electrolyte membrane that can be suitably used for applications such as oxygen depletion that lowers the oxygen concentration in a refrigerator vegetable compartment and oxygen enrichment in an air conditioner that increases the oxygen concentration in the refrigerator Concerning the concentration adjuster.

[0002]

2. Description of the Related Art FIG.
FIG. 5 is a configuration diagram of an electrochemical oxygen concentration adjuster disclosed in Japanese Patent Publication No. JP-A-2003-242, in FIG. 4, 1 is an anode, 2 is a cathode, 3 is a solid polymer electrolyte membrane, 4 is a current collector, and 5 is oxygen enriched. Chamber, 6 is an oxygen depleted chamber, 7 is a gas inlet to the oxygen enriched chamber, 8 is a gas outlet of the oxygen enriched chamber, 9 is a gas inlet to the oxygen depleted chamber, and 10 is a gas outlet of the oxygen depleted chamber. , 11 is a generated water reservoir, 12 is a supply water reservoir,
13 is a pump. Here, oxygen depletion means reducing the oxygen concentration in the gas, and oxygen enrichment means increasing the oxygen concentration in the gas. As the solid polymer electrolyte membrane 3, for example, Nafion-117 manufactured by Du Pont, which is described in Japanese Patent Publication No. 63-52119, is used, and its nominal thickness is 7 mils. It is about 170 μm, and the shortest distance between the anode and the cathode is about 150 μm.

The operation of the electrochemical oxygen concentration regulator will be described below.

At the anode 1, water is electrolyzed by an external electric power to cause the reaction of the formula (1) to increase the oxygen concentration in the oxygen enrichment chamber.

2H ₂ O → O ₂ + 4H ⁺ + 4e ⁻ (1) Protons (H ⁺ ) generated at this time pass through the solid polymer electrolyte membrane, and electrons (e ⁻ ) pass through an external circuit to reach the cathode. By the reaction of the equation (2), oxygen is consumed to reduce the oxygen concentration in the oxygen depleted chamber.

O ₂ + 4H ⁺⁺ 4e ⁻ → 2H ₂ O (2) Further, together with the proton (H ⁺ ), about 3 molecules of water move from the anode to the cathode on average. Therefore, at the cathode, along with the water produced by the reaction of the formula (2), extra water moves from the anode, and on the other hand, water is required at the anode. Therefore, it is necessary to move the water to the generated water reservoir 12 using the pump 13. There is.

An electrochemical oxygen concentration adjuster using the oxygen depletion chamber shown in FIG. 4 is disclosed in Japanese Examined Patent Publication No. 55-2534.
There is application to a vegetable storage such as a fruit and vegetable storage or a refrigerator as described in Japanese Patent Publication No.

There is an air conditioner that utilizes the oxygen enriched chamber, and the air conditioner is used to increase the oxygen concentration in a room such as a hospital.

[0009]

In the conventional electrochemical oxygen concentration regulator, the produced water reservoir 11 and the feed water reservoir 1 are as described above.
2 is required, and there is a problem that water needs to be moved by the pump 13 as needed.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an electrochemical oxygen concentration regulator which can omit the generated water reservoir, the feed water reservoir and the pump.

[0011]

Means for Solving the Problems The present invention comprises an anode for electrolyzing water to generate oxygen, a cathode for generating water to consume oxygen, the anode and a solid polymer electrolyte membrane held by the cathode. An electrochemical oxygen concentration adjuster, which comprises oxygen generation at the anode or oxygen consumption at the cathode to adjust the oxygen concentration, wherein the shortest distance between the anode and the cathode is 50 μm.
The present invention relates to an electrochemical oxygen concentration adjuster using a solid polymer electrolyte membrane, which is characterized by being m or less.

[0012]

In the electrochemical oxygen concentration controller using the solid polymer electrolyte membrane of the present invention, the shortest distance between the anode and the cathode is 50 μm.
Since it is less than m, the reverse diffusion movement of water from the cathode to the anode becomes remarkable, and most of the water generated at the cathode and the water moving to the cathode returns to the anode through the solid polymer electrolyte membrane, and , The supply sump and pump can be omitted.

[0013]

EXAMPLES An example of an electrochemical oxygen concentration regulator (hereinafter referred to as oxygen concentration regulator) using the solid polymer electrolyte membrane of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an embodiment of the oxygen concentration controller of the present invention.

In FIG. 1, reference numeral 1 is an anode that electrolyzes water to generate oxygen, and includes an anode electrode substrate 14 and an anode catalyst layer 26.
Composed of. Reference numeral 2 denotes a cathode that generates water and consumes oxygen, and includes a cathode electrode base material 15 and a cathode catalyst layer 27. 3 is a solid polymer electrolyte membrane sandwiched by the anode and the cathode, 14 is an anode electrode base material made of Pt-plated titanium expanded metal, and 15 is a cathode electrode base material made of carbon fiber, both of which are porous.

In the figure, the wavy line between 16 and 17 indicates that the solid polymer electrolyte membrane 3 bites into the anode electrode base material 14 and the cathode electrode base material 15, and the above-mentioned bitten layer is Anode catalyst layer 26 and cathode catalyst layer 2 in which platinum catalyst is present
It is also shown that it is 7.

Reference numeral 16 represents the shortest distance between the anode and the cathode, and 17
Indicates the thickness of the solid polymer electrolyte membrane. Nafion-115 manufactured by DuPont is used as the solid polymer electrolyte membrane 3, and its thickness is about 130 μm. The shortest distance 16 between the anode and the cathode in FIG. 1 has been confirmed to be 30 μm by observing a cross section with a scanning electron microscope.

The electrode base material for the anode and cathode is 190 ° C.
The positive electrode catalyst layer 26 and the negative electrode catalyst layer 27 in which the platinum catalyst existing in the solid polymer electrolyte membrane by hot pressing under the condition of 50 kgf / cm ² is present to carry out the reactions of the formulas (1) and (2) are formed. In the solid polymer electrolyte membrane, the anode base material or the cathode base material is present in a three-dimensional distribution in the invaded layer.

Reference numeral 18 denotes an electrically insulating resin, which is divided into an oxygen-enriched side 19 and an oxygen-poor side 20 with a coin-shaped anode 1, cathode 2 and solid polymer electrolyte membrane 3 in between. ing. Reference numeral 21 is an arrow indicating the direction of back diffusion of water from the cathode to the anode. In addition, no production water reservoir, supply water reservoir and pump are provided.

Next, the operation of the oxygen concentration controller will be described. FIG. 2 uses the oxygen concentration regulator of the present invention shown in FIG. 1, uses the oxygen-enriched side 19 as a closed chamber, and applies a DC voltage of 2.5 V between the anode and the cathode using an external DC power source. The results of examining changes in relative humidity and oxygen concentration in the closed chamber over time are shown in graphs, and are indicated by solid lines 22 and 23. Thickness 170 for comparison
The same experiment as in the case of the oxygen concentration regulator of the present invention was performed by using a conventional oxygen concentration regulator using Nafion-117 manufactured by DuPont with a minimum distance of 150 μm between the anode and the cathode. The results are shown in FIG. 2 by the alternate long and short dash line. The solid line 23 and the alternate long and short dash line 25 indicate changes in relative humidity of the oxygen concentration regulator of the present invention and the conventional oxygen concentration regulator, respectively, and the solid line 22 and the alternate long and short dash line 24 indicate the oxygen concentration regulator of the present invention, respectively. 3 shows changes in oxygen concentration of a conventional oxygen concentration regulator.

In the oxygen concentration regulator of the present invention in which the shortest distance between the anode and the cathode is 30 μm, the oxygen concentration rises to almost the same level as the conventional type, but the relative humidity does not decrease much. This indicates that there is no shortage of water in the sealed chamber on the oxygen-enriched side 19, that is, the amount of back diffusion of water from the cathode to the anode shown by the arrow 21 in FIG. 1 is large. In this way, the amount of back diffusion of water is large, because the distance between the anode and the cathode is shortened, the back diffusion due to the concentration difference of water from the cathode to the anode becomes easy,
It is considered that this is because the water in the cathode returns to the anode faster than the water evaporates from the anode.

On the other hand, oxygen has a low solubility in water, and even if the distance between the anode and the cathode is shortened, as long as the solid polymer electrolyte membrane contains water, the oxygen-rich side 19 becomes the oxygen-poor side. The amount of oxygen diffused into 20 was small, and was hardly affected by the reduction in the distance between the anode and the cathode as shown by the solid line 22 in FIG. In other words, the reverse diffusion amount of water can be significantly increased by shortening the distance between the anode and the cathode without using a pump to move the water from the cathode to the anode as in the conventional oxygen concentration regulator. It can be clearly seen from the result of FIG. 2 that the oxygen concentration adjusting function is not impaired.

With respect to the oxygen-poor side 20, the same experiment was conducted with the oxygen-poor side as a closed chamber, and it was confirmed that the oxygen concentration adjusting effect was obtained.

By making the distance 16 between the anode and the cathode much shorter than the thickness 17 of the solid polymer electrolyte membrane, the diffusion distance of oxygen can be made larger than the back diffusion distance of water, and the cathode From water to the oxygen-depleted side 20 can be reduced, and as a result, more water can be returned from the cathode to the anode, and oxygen can be more reliably prevented from diffusing to the cathode side.

Actually, using the oxygen concentration regulator of the present invention,
FIG. 3 shows the result of examining the relationship between the shortest distance between the anode and the cathode and the amount of back diffusion of water.

In this case, in order to change the shortest distance between the anode and the cathode, the thickness of the solid polymer electrolyte membrane and the hot pressing conditions for hot pressing the anode electrode base material and the cathode electrode base material Was changed.

The solid polymer electrolyte membrane used was Nafion 117 (a thickness of about 170 μm) manufactured by DuPont, and hot pressing was performed at 190 ° C. and a surface pressure of 50 kgf / cm ² for 3 minutes. The depth of biting into the substrate was adjusted using a spacer having a constant thickness.

The other conditions are the same as in the case of examining the relationship between the oxygen concentration and relative humidity and the elapsed time, the results of which are shown in FIG. 2, and in FIG. The humidity is plotted.

As can be seen from the results of FIG. 3, in the oxygen concentration regulator of the present invention in which the shortest distance between the anode and the cathode is 50 μm or less, the relative humidity is clearly higher than that of the other ones. It shows that the water consumption on the side is low. It is considered that the above phenomenon occurs because the amount of back diffusion of water from the cathode to the anode increased.

The present invention has been described based on the above-mentioned embodiment. However, in the oxygen concentration controller of the present invention, the solid polymer film may be sandwiched between the anode and the cathode, as in the above-mentioned embodiment. The anode and the cathode do not necessarily have to dig into the solid polymer electrolyte membrane, and if the shortest distance between the anode and the cathode is 50 μm or less, preferably 20 to 50 μm, the back diffusion amount of water is large, and the cathode of oxygen is The diffusion to the anode can be prevented. In this case, for example, a solid polymer electrolyte membrane having a thickness of 50 μm or less can be used.

Further, if at least one of the anode and the cathode has a porous base material invading the solid polymer electrolyte membrane, even if the thickness of the solid polymer electrolyte membrane is 50 μm or more, the anode and the cathode are formed. By setting the shortest distance to and from 50 μm or less, the back diffusion amount of water can be increased as in the above embodiment. In addition, both the anode and cathode substrates do not necessarily have to dig into the solid polymer electrolyte membrane as in the above-mentioned embodiment.

In the oxygen concentration regulator of the present invention, when at least one of the anode and the cathode has a porous base material which is invaded in the solid polymer electrolyte membrane, the diffusion of oxygen from the cathode to the positive is more effectively prevented. There is an effect that can be done.

In the electrochemical oxygen concentration regulator of the present invention, the electrode base material is not particularly limited as long as it is a corrosion-resistant and electrically conductive porous body, but the anode electrode base material is the porous expanded metal described above. In addition, for example, a stainless steel fiber or a stainless steel fiber usually used as an anode electrode material is plated with platinum, and the cathode electrode base material is, in addition to the carbon fiber, for example, an ordinary electrode material. The stainless steel fibers and nickel fibers used may be used.

The solid polymer electrolyte membrane may be any one that conducts protons. From these points, Nafion-117 and Nafion-1 manufactured by DuPont can be used.
15, XUS-13.204.10 manufactured by Dow Chemical Co., which is usually used as a solid polymer electrolyte membrane.
Etc.

The oxygen concentration controller of the present invention may be composed of an anode and a cathode and a solid polymer electrolyte membrane sandwiched by both of them, and the size thereof is not particularly limited, but is as compact as possible. It may be bent to be

The capacity of the oxygen concentration regulator of the present invention varies depending on its size and cannot be determined unconditionally. For example, an oxygen concentration regulator having an electrode area of 100 cm ² produces 20 to 200 cc / oxygen. The amount of oxygen and the amount of deoxidization are 20 to 200 cc / min.

[0037]

According to the present invention, since the shortest distance between the anode and the cathode is set to 50 μm or less, the reverse diffusion movement of water from the cathode to the anode can be remarkably increased, and the water generated at the cathode and the cathode can be transferred. Since most of the transferred water returns to the anode through the solid polymer electrolyte membrane, the generated water reservoir, the feed water reservoir,
Further, it is possible to omit the pump and provide an inexpensive device.

[Brief description of drawings]

FIG. 1 is a sectional view of an electrochemical oxygen concentration regulator using a solid polymer electrolyte membrane according to an embodiment of the present invention.

FIG. 2 is a graph showing changes with time in relative humidity and oxygen concentration of an oxygen concentration regulator using a solid polymer electrolyte membrane.

FIG. 3 is a graph showing the relationship between the relative distance and the shortest distance between the anode and the cathode of an oxygen concentration regulator using a solid polymer electrolyte membrane.

FIG. 4 is a cross-sectional view of a conventional electrochemical oxygen concentration adjuster using a solid polymer electrolyte membrane.

[Explanation of symbols]

 1 Anode 2 Cathode 3 Solid Polymer Electrolyte Membrane 14 Anode Electrode Base Material 15 Cathode Electrode Base Material 16 Shortest Distance between Anode and Cathode 17 Solid Polymer Electrolyte Membrane Thickness

Claims (2)

[Claims] 1. Oxygen generation at the anode, comprising an anode for electrolyzing water to generate oxygen, a cathode for generating water to consume oxygen, and the anode and a solid polymer electrolyte membrane sandwiched by the cathode. Alternatively, an electrochemical oxygen concentration adjuster for adjusting oxygen concentration by using oxygen consumption at the cathode, wherein a solid polymer electrolyte membrane having a shortest distance between the anode and the cathode of 50 μm or less is used. There was an electrochemical oxygen concentration regulator. 2. The electrochemical oxygen concentration adjuster according to claim 1, wherein at least one of the anode and the cathode has a porous electrode base material that is digged into the solid polymer electrolyte membrane.