JP2004077301A - Moisture detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure moisture contained in air with a wide range from a low concentration of ppm level to a high concentration of % level. <P>SOLUTION: This moisture detector comprises a porous positive electrode, a porous negative electrode, an electrolyte layer arranged so as to make contact with the positive electrode at one surface and the negative electrode at the other surface between both the electrodes and made of a material exhibiting hydrogen ion conductivity even without contained moisture, and a power source applying voltage between the electrolyte layer and the positive electrode and the negative electrode. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a moisture detector using an ionic conductive solid electrolyte.
[0002]
[Prior art]
FIG. 5 relates to a moisture detecting (moisture sensitive) element described in, for example, JP-A-60-36947, and shows the structure thereof. In FIG. 5, 1 is an anode feeder, 2 is an anode, 5 is a cathode, and 6 is a cathode feeder. The anode 2 and the cathode 5 are each subjected to a porous substrate Pt plating of titanium. Reference numeral 4 denotes a solid polymer electrolyte membrane (trade name; Nafion 117: manufactured by DuPont). Pt electroless plating is applied between each electrode and the solid polymer electrolyte membrane 4. 7 is a lead wire and 8 is a DC power supply. 10 is an ammeter. When a DC voltage of 3.5 V is applied between the two electrodes, a current proportional to the humidity flows (see FIG. 6). This is because the solid polymer electrolyte membrane has a water content corresponding to the high humidity, and the conductivity of the solid polymer membrane changes according to the increase and decrease of the water content.
[0003]
[Problems to be solved by the invention]
Conventional moisture detectors use an ion-exchange membrane (solid polymer electrolyte membrane) that exhibits hydrogen ion conductivity by absorbing moisture, so even when trying to detect ppm-level moisture, the moisture content in the solid polymer electrolyte membrane is almost constant. As a result, the conductivity was lowered and water detection could not be performed, so that it could not be used practically.
When used in contact with a high humidity atmosphere, the solid polymer is equilibrated with the humidity in the atmosphere. The electrolytic reaction of the moisture absorbed in the electrolyte takes precedence, and the moisture (humidity) in the atmosphere cannot be measured quickly.
[0004]
Thus, in the present invention, such that the solid electrolyte layer of the moisture detector does not contain moisture, moisture can be detected even when the moisture in the atmosphere is at the ppm level. A wide range of moisture (humidity) in the atmosphere can be measured from a low concentration of ppm level to a high concentration of% level so that the moisture can be detected even when the solid electrolyte contains a large amount of water. It is intended to provide a moisture detector.
[0005]
[Means for Solving the Problems]
The moisture detector according to the first invention comprises:
A porous anode,
A porous cathode;
Between the anode and the cathode, one surface is in contact with the anode, provided so that the other surface is in contact with the cathode,
An electrolyte layer made of a substance exhibiting hydrogen ion conductivity even in a state without water content,
A power supply for applying a voltage between the electrolyte layer and the anode and the cathode is provided.
[0006]
In the moisture detector according to the second invention,
The solid electrolyte layer is triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ),
X in the above molecular formula is a compound that is between 1 ≦ x ≦ 2.
[0007]
In the moisture detector according to the third invention,
The solid electrolyte layer is hexamethylenetetramine sulfate (C ₆ H ₁₂ N ₄ .xH ₂ SO ₄ ),
X in the above molecular formula is a compound that is in the range of 1.5 ≦ x ≦ 2.5.
[0008]
In the moisture detector according to the fourth invention,
At least two anodes are provided on one surface of the solid electrolyte, the anodes are arranged without being in contact with each other, and one of the anodes is provided with a water-repellent layer.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described. FIG. 1 is a diagram showing a configuration of a moisture detector according to the present invention. In the figure, reference numeral 1 denotes an anode power supply, and 5 denotes a cathode power supply. The respective materials are made of stainless steel and plated with Pt. Reference numeral 2 denotes an anode and 5 denotes a cathode, each of which is formed by Pt sputtering to a thickness of 20 to 40 nm.
Reference numeral 4 denotes an amine-sulfate solid electrolyte composed of hydrogen ion conductive triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ) with a value of x = 1.5. The reason for setting x = 1.5 is that, as shown in FIG. 2, the conductivity of triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ) is x (the molar composition ratio of sulfate to amine 1). This is because, depending on the value of x), the highest conductivity is exhibited when x = 1.5.
[0010]
In addition, the conductivity data shown in FIG. 2 indicates that after the electrodes are provided on the solid electrolyte containing no water in the synthesis process to form an electrochemical element, a dry atmosphere is further maintained in the presence of phosphorus pentoxide to sufficiently absorb moisture. This is data after removing moisture, and it can be confirmed that the sample exhibits hydrogen ion conductivity even without moisture absorption.
[0011]
Next, the operation will be described.
When a voltage is applied from the DC power supply 8 between the anode 2 and the cathode 5, H ₂ O is
^{_{H 2 O → 2H + + 1}} / 2O 2 + 2e - ··· (1)
To generate H ⁺ ions, move in the solid electrolyte 4 toward the cathode, and generate 2H ⁺ + 2e ⁻ → H ₂ (2) at the cathode 5.
Reaction occurs. FIG. 4 shows the relationship between the moisture concentration and the output current in a low humidity atmosphere with the applied voltage as a parameter. From the graph shown in FIG. 4, this element (moisture detector) is used for detecting a water concentration in a relatively low humidity range of several tens ppm to several thousand ppm, which could not be measured by an element using a solid polymer electrolyte. It turns out to be effective.
[0012]
Embodiment 2 FIG.
Hereinafter, Embodiment 2 of the present invention will be described. FIG. 3 is a diagram showing a configuration of the moisture detector according to the present invention. In the figure, reference numeral 2 denotes an anode, and two anodes 2 a and 2 b are provided on the solid electrolyte 4. The anode 2a and the anode 2b are arranged without being in contact with each other. One anode 2a has a water-repellent layer 9 and the other anode 2b does not have a water-repellent layer. Here, the water-repellent layer 9 is spray-sprayed with a dispersion material (trade name: Hirec 110; manufactured by NTT Advanced Technology Co., Ltd.) containing PTFE (polytetrafluoroethylene) and exhibiting super water repellency with a contact angle of 150 ° or more. ing.
[0013]
Hereinafter, the operation will be described.
The current i ₂ flowing through the anode 2b having no water-repellent layer was measured by a current meter 11b, the current value is measured i ₁ flowing through the anode 2a which is provided with a water-repellent layer with an ammeter 11a. Current i ₂ is to cause the original hydrogen ion current water that had been moisture in the electrolyte is caused by causing electrode reaction (1), the electrode reaction at the anode 2b after initiation atmospheric moisture energized (1) It is the sum of the hydrogen ion current generated by
After starting the energization, electric current value difference i ₂ and current i ₁ is gradually decreased. This is because, among the current components constituting the current value i ₂ , the hydrogen ion current due to the moisture originally absorbed by the electrolyte decreases with time, so that the current value i ₂ decreases with time. Will go on.
[0014]
Over time, the current value i ₂ is decreasing, the value of the current (i 2 _{-i 1)} becomes almost constant, when it is substantially constant, the water that had been originally moisture in the electrolyte The relationship between the current value and the gaseous phase moisture in a state where the influence is eliminated can be obtained.
Moisture detectors have two or more anodes on a solid electrolyte, one of which has a water-repellent layer on the anode, so even in high humidity conditions, the electrolyte is originally included in the electrolyte. The moisture in the atmosphere can be detected with the influence of the absorbed moisture removed. Therefore, it has become possible to measure a wide range of air moisture concentration from low humidity (several ppm) to high humidity (several%).
[0015]
In this embodiment, the solid electrolyte is composed of triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ), and the case where x is 1.5 in the molecular formula on the left has been described. Is the same when 1 ≦ x ≦ 2, the same effect is obtained.
The same effect can be obtained by using a compound in which hexamethylenetetramine sulfate (C ₆ H ₁₂ N ₄ .xH ₂ SO ₄ ) x is between 1.5 ≦ x ≦ 2.5 as the solid electrolyte.
[0016]
According to the first and second embodiments, the solid electrolyte performs moisture detection using a substance exhibiting hydrogen ion conductivity even when the solid electrolyte itself does not contain moisture.
In addition, when performing moisture detection (in the atmosphere) in a relatively high humidity region where the moisture content is a% level,
In order to be able to measure even if the amount of moisture absorption of the amine-sulfate compound constituting the solid electrolyte of the moisture detector is not negligible,
A hydrogen ion current generated by electrolysis caused by water absorption in the solid electrolyte and a hydrogen ion current generated by electrolysis generated at the anode by water contained in the test gas can be distinguished.
[0017]
For this purpose, two or more anodes are provided on one surface of the solid electrolyte, and these anodes are arranged without being in contact with each other. Further, any one of the anodes is provided with a water-repellent layer. The anode provided with the water-repellent layer can eliminate the influence of the hydrogen ion current generated by moisture absorption in the solid electrolyte.
After the start of voltage application between the anode and the cathode of the moisture detector, the difference between the current flowing between the anode and the cathode without the water-repellent layer and the current between the anode and the cathode with the water-repellent layer becomes substantially constant. From this point on, moisture in the test gas can be detected without being affected by the moisture contained in the electrolyte layer.
[0018]
【The invention's effect】
According to the first invention, a porous anode,
A porous cathode;
Between the anode and the cathode, one surface is in contact with the anode, provided so that the other surface is in contact with the cathode,
An electrolyte layer made of a substance exhibiting hydrogen ion conductivity even in a state without water content,
Since a power source for applying a voltage between the electrolyte layer and the anode and the cathode is provided,
The solid electrolyte exhibiting hydrogen ion conductivity even without moisture absorption makes it possible to measure the water concentration in a low water concentration range of several ppm.
[0019]
According to the second invention, the solid electrolyte layer is made of triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ),
Since x in the above molecular formula is a compound between 1 ≦ x ≦ 2,
Moisture concentration measurement in a low moisture concentration range of several ppm has become possible.
[0020]
According to the third aspect, the solid electrolyte layer is hexamethylenetetramine sulfate (C ₆ H ₁₂ N ₄ .xH ₂ SO ₄ ),
Since x in the above molecular formula is a compound that is between 1.5 ≦ x ≦ 2.5,
Moisture concentration measurement in a low moisture concentration range of several ppm has become possible.
[0021]
According to the fourth aspect of the present invention, there are at least two anodes on one surface of the solid electrolyte, the respective anodes are arranged without being in contact with each other, and one of the anodes is provided with a water-repellent layer. ,
By the water-repellent layer provided on the anode, it is possible to remove the influence of the current generated by the moisture absorption originally contained in the solid electrolyte layer,
It is possible to accurately detect the moisture concentration even in a high humidity region.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a moisture detector of the present invention.
FIG. 2 is a diagram showing the conductivity of a solid electrolyte layer used in the moisture detector of the present invention.
FIG. 3 is a diagram showing a configuration of a moisture detector of the present invention.
FIG. 4 is a diagram showing a relationship between a moisture concentration and a current in the moisture detector of the present invention.
FIG. 5 is a diagram showing a configuration of a conventional moisture detector.
FIG. 6 shows the relationship between relative humidity and current density in a conventional moisture detector.
[Explanation of symbols]
1 anode feeder, 2 anode, 4 solid electrolyte, 5 cathode,
6 Cathode feeder, 7 Lead wire, 8 Power supply.

Claims (4)

A porous anode,
A porous cathode;
Between the anode and the cathode, one surface is in contact with the anode, provided so that the other surface is in contact with the cathode,
An electrolyte layer made of a substance exhibiting hydrogen ion conductivity even in a state without water content,
A moisture detector comprising: the electrolyte layer; and a power supply for applying a voltage between the anode and the cathode. The solid electrolyte layer is triethylenediamine sulfate (C ₆ H ₁₂ N ₂ .xH ₂ SO ₄ ),
2. The moisture detector according to claim 1, wherein x in the molecular formula is a compound that satisfies 1 ≦ x ≦ 2. The solid electrolyte layer is hexamethylenetetramine sulfate (C ₆ H ₁₂ N ₄ .xH ₂ SO ₄ ),
2. The moisture detector according to claim 1, wherein x in the molecular formula is a compound that satisfies 1.5 ≦ x ≦ 2.5. At least two anodes are provided on one surface of the solid electrolyte, the respective anodes are arranged without being in contact with each other, and one of the anodes is provided with a water-repellent layer. 3. The moisture detector according to any one of 3.

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