JP2006090991A - Electrochemical gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ammonia gas detection electrochemical gas sensor and an alcohol gas detection electrochemical gas sensor having high reliability in long-term use, and having excellent gas selectivity. <P>SOLUTION: This electrochemical gas sensor has at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode. The electrolyte is a molten salt constituted of nitrogen-including aromatic cation or aliphatic onium cation and fluorine-including anion, to thereby acquire the miniaturized and thinned electrochemical gas sensor having high reliability and excellent gas selectivity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrochemical gas sensor using a room temperature molten salt that becomes an ionic liquid at a relatively low temperature as an electrolyte.

  Conventionally, electrochemical gas sensors have features such as low power consumption, linear output characteristics, and relatively good gas selectivity, so they can detect industrial gas concentration measuring instruments and, recently, carbon monoxide, etc. Widely used for alarm devices.

First, FIG. 2 shows an example of a conventional electrochemical gas sensor.
The conventional electrochemical gas sensor 1 has a case 2, and the case 2 has an opening 22, and a lid 25 in which a capillary 26 having a smaller opening is formed.
In this case 2, a working electrode 11, a counter electrode 12, a reference electrode 13, an electrolyte holding body 14, and gas permeable membranes 15a and 15b are housed, and are fixed to the case 2 by means not shown.
Further, an electrolyte solution storage portion 32 for storing the electrolyte solution 31 is provided in the case 2, and a hydrophilic conductive material such as glass fiber is provided from the electrolyte solution storage portion 32 toward the electrolyte holder 14. A liquid 33 is provided. The electrolyte solution 31 stored in the electrolyte solution storage part 32 through the conductive liquid 33 is configured to be constantly replenished to the electrolyte holder 14.
In addition, electrode pins (not shown) are provided in contact with the working electrode 11, the counter electrode 12, and the reference electrode 13, respectively, and are connected to an external circuit such as a measurement circuit including a potentiostat, When the detection target gas reaches the working electrode 11, the gas component of the detection target gas sequentially undergoes oxidation or reduction reaction, and this reaction is output to the outside through the electrode pin connected to the working electrode 11.

Among these electrochemical gas sensors, particularly when detecting ammonia gas, the electrochemical gas sensor is superior in stability compared to other means such as semiconductor gas sensors. One using an aqueous ammonium salt solution or the like is known (see, for example, Patent Documents 1 and 2).
However, since these electrolyte solutions are highly hygroscopic and volatile, there is a problem that the volume and concentration of the electrolyte solution change depending on the surrounding humidity, and the reliability is lacking, such as affecting sensitivity. Further, when the volume increases, there is a problem such as leakage of the electrolyte solution.

In addition, when detecting alcohol gas, the electrochemical gas sensor is superior in gas selectivity compared to sensors of other means such as a catalytic combustion type gas sensor. For example, most flammable gases are detected especially with catalytic combustion gas sensors, but flammable gases other than alcohol are not detected with electrochemical gas sensors, so they are excellent in detecting alcohol gas in such an atmosphere. . As an electrochemical gas sensor for detecting these alcohol gases, for example, one using sulfuric acid or a lithium chloride aqueous solution as an electrolyte solution is known (see, for example, Patent Document 3).
However, these electrolyte solutions are highly hygroscopic in the case of sulfuric acid, and highly hygroscopic and volatile in the case of an aqueous lithium chloride solution, so that volume changes and concentration changes of the electrolyte solution are likely to occur depending on the surrounding humidity. In particular, when a lithium chloride aqueous solution is used, there is a problem in that the volume is remarkably easily changed due to volatilization, so that the sensitivity is likely to fluctuate and the reliability is insufficient. Further, when sulfuric acid is used, the hygroscopic property is high, and there is a problem that the volume of the electrolyte solution increases and liquid leakage occurs.
In addition, electrochemical gas sensors that use lithium chloride aqueous solution or sulfuric acid for these electrolyte solutions are sensitive to various gases, so they may detect gases other than the target gas. is there.

In recent years, the use of a room temperature molten salt that becomes an ionic liquid at a relatively low temperature as a molten salt for various reaction solvents and electrochemical applications has been investigated, and this room temperature molten salt was used in place of a solid electrolyte. Nitrogen oxide sensors and carbon dioxide sensors have also been proposed (for example, Patent Documents 4 and 5).
However, in the above Patent Documents 4 and 5, in a sensor using a solid electrolyte as an electrolyte, the electrolyte is replaced with a room temperature molten salt. Therefore, in the nitrogen oxide sensor, “mainly lithium nitrate or lithium nitrite” is used. It is essential that the auxiliary phase is equipped with an electrode-auxiliary phase assembly in which the auxiliary phase is integrally joined to one or both of the detection electrode and the counter electrode made of a gas diffusion electrode. It is essential that the phase is integrally joined to the detection electrode. For this reason, since the structure is naturally complicated, there is a problem that the shape of the sensor becomes large and the manufacturing cost is high. Moreover, there is no suggestion about the solution about gas selectivity.

JP 2001-208723 A (page 2) JP-A-2-195247 (first page, third page) US Pat. No. 3,966,579 (pages 6-7) JP 2003-172722 A (Page 2) JP 2003-172723 A (second page)

  An object of the present invention is to provide an ammonia gas detection electrochemical gas sensor and an alcohol gas detection electrochemical gas sensor that are highly reliable in long-term use and excellent in gas selectivity.

The electrochemical gas sensor according to claim 1 is an electrochemical sensor having at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode, wherein the electrolyte is a nitrogen-containing aromatic cation or an aliphatic onium cation. And a fluorine-containing anion, and the detection target gas is ammonia gas.
And it becomes a liquid state without requiring a solvent by making the electrolyte into a molten salt which is composed of a nitrogen-containing aromatic cation or an aliphatic onium cation and a fluorine-containing anion and is in a liquid state in a room temperature range. Therefore, it can be used similarly to the conventional electrolyte solution.
In addition, since the molten salt has almost no hygroscopicity or volatility, it is difficult for the volume to change. Therefore, it is sufficient to sufficiently impregnate the electrolyte holding body 14 with the molten salt. Therefore, it is essential in the conventional electrochemical gas sensor 1. By eliminating the need for the electrolyte solution reservoir 32 and the conductive liquid 33, the electrochemical gas sensor can be reduced in size and thickness.
Further, since this molten salt has almost no hygroscopicity or volatility, the sensor output does not fluctuate greatly, and there is little risk of liquid leakage or the like, and a highly reliable electrochemical gas sensor is obtained.
Furthermore, by using this molten salt as an electrolyte, a suitable electrochemical gas sensor having excellent gas selectivity can be obtained.

The electrochemical gas sensor according to claim 2 is an electrochemical sensor having at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode, wherein the electrolyte is a nitrogen-containing aromatic cation or an aliphatic onium cation. And a fluorine-containing anion, and the detection target gas is an alcohol gas.
And it becomes a liquid state without requiring a solvent by making the electrolyte into a molten salt which is composed of a nitrogen-containing aromatic cation or an aliphatic onium cation and a fluorine-containing anion and is in a liquid state in a room temperature range. Therefore, it can be used similarly to the conventional electrolyte solution.
In addition, since the molten salt has almost no hygroscopicity or volatility, it is difficult for the volume to change. Therefore, it is sufficient to sufficiently impregnate the electrolyte holding body 14 with the molten salt. Therefore, it is essential in the conventional electrochemical gas sensor 1. By eliminating the need for the electrolyte solution reservoir 32 and the conductive liquid 33, the electrochemical gas sensor can be reduced in size and thickness.
Further, since this molten salt has almost no hygroscopicity or volatility, the sensor output does not fluctuate greatly, and there is little risk of liquid leakage or the like, and a highly reliable electrochemical gas sensor is obtained.
Furthermore, by using this molten salt as an electrolyte, a suitable electrochemical gas sensor having excellent gas selectivity can be obtained.

The electrochemical gas sensor according to claim 3 is the electrochemical gas sensor according to claim 1 or 2, wherein the nitrogen-containing aromatic cation is an alkylimidazolium ion or an alkylpyridinium ion.
Then, the nitrogen-containing aromatic cation constituting the molten salt is an alkylimidazolium ion or an alkylpyridinium ion, whereby an electrochemical gas sensor having more preferable characteristics is obtained.

The electrochemical gas sensor according to claim 4 is the electrochemical gas sensor according to claim 1 or 2, characterized in that the fluorine-containing anion is a borofluoride ion, a phosphofluoride ion or a trifluoromethanesulfonate ion.
Then, when the fluorine-containing anion constituting the molten salt is a borofluoride ion, a phosphofluoride ion or a trifluoromethanesulfonic acid ion, an electrochemical gas sensor having more preferable characteristics is obtained.

  According to the electrochemical gas sensor of claim 1, it has at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode, and the electrolyte includes a nitrogen-containing aromatic cation or an aliphatic onium cation, Electrochemical system with a molten salt composed of fluorine-containing anions and ammonia gas as a detection target, which is smaller, thinner, more reliable, and more selective than conventional electrochemical gas sensors. A gas sensor can be obtained.

  According to the electrochemical gas sensor of claim 2, it has at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode, and the electrolyte is a nitrogen-containing aromatic cation or an aliphatic onium cation, Electrochemical system with a molten salt composed of fluorine-containing anions and alcohol gas as a detection target, which is smaller, thinner, more reliable, and more selective than conventional electrochemical gas sensors. A gas sensor can be obtained.

  According to the electrochemical gas sensor according to claim 3, in the electrochemical gas sensor according to claim 1 or 2, the nitrogen-containing aromatic cation is an alkylimidazolium ion or an alkylpyridinium ion. A gas sensor can be obtained.

  According to the electrochemical gas sensor of claim 4, in the electrochemical gas sensor of claim 1 or 2, the fluorine-containing anion is a borofluoride ion, a phosphofluoride ion, or a trifluoromethanesulfonate ion. The electrochemical gas sensor can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of an electrochemical gas sensor. The electrochemical gas sensor 10 has a case 21 made of, for example, a synthetic resin.
The case 21 has an opening 22 on one surface side, that is, the upper surface side, and a lid 25 made of, for example, synthetic resin is attached to the one surface side, and a capillary 26 that is a small opening is formed on the lid 25. Yes. Further, the case 21 is composed of a plurality of parts and is formed by being joined by a joint portion (not shown).

  In the case 21, the working electrode 11, the counter electrode 12, the reference electrode 13, the electrolyte holding body 14, and the gas permeable membranes 15a and 15b are housed.

The gas permeable membrane 15a is liquid-tightly coupled to the case 21 by caulking or the like through a joint portion (not shown), and the working electrode 11 is provided in close contact with the one side facing the case 21 of the gas permeable membrane 15a. Yes. A counter electrode 12 and a reference electrode 13 are provided in close contact with one surface of the other gas permeable membrane 15b, and each of the counter electrode 12, the reference electrode 13, and the working electrode 11 is in contact with the electrolyte holding body 14. The electrolyte holder 14 is in contact with the gas permeable membranes 15a and 15b so as to be held and fixed in the case 21. It may be fixed by a projection (not shown) in the case 21 or an electrode pin (not shown).
The gas permeable membranes 15a and 15b are formed into a sheet shape with a material such as polytetrafluoroethylene (PTFE) having hydrophobicity and air permeability.

The counter electrode 12 and the reference electrode 13 are externally connected through a gas permeable membrane 15b, a gap in the case 21, and a portion of the gas permeable membrane 15a where the working electrode 11 is not provided, and further through a capillary 26 provided on the lid 25. Communicating with
Here, a small opening or the like (not shown) may be provided in the case 21 so as to communicate with the outside through the opening or the like.

The working electrode 11, the counter electrode 12 and the reference electrode 13 are gas diffusion electrodes containing a catalyst and a hydrophobic resin. As the catalyst, platinum (Pt), gold (Au), ruthenium (Ru), ruthenium oxide (RuO ₂ ). ), Palladium (Pd), carbon (C) and the like are suitably used, and PTFE resin and the like are suitably used as the hydrophobic resin.

The electrolyte holder 14 is made of, for example, glass fiber, and the electrolyte holder 14 is sufficiently impregnated with a room temperature molten salt as an electrolyte.
As this room temperature molten salt, a molten salt mainly composed of a nitrogen-containing aromatic cation or aliphatic onium cation and a fluorine-containing anion that is in a liquid state at room temperature, for example, in the range of −10 ° C. to + 50 ° C., is used. .
As the nitrogen-containing aromatic cation, for example, an alkyl imidazolium ion or an alkyl pyridinium ion is used. As the fluorine-containing anion, for example, borofluoride ion, phosphorous fluoride ion or trifluoromethanesulfonate ion is used.

  In addition, electrode pins (not shown) are provided in contact with the working electrode 11, the counter electrode 12, and the reference electrode 13, respectively, and are connected to an external circuit such as a measurement circuit including a potentiostat.

  In this electrochemical gas sensor 10, after the gas to be detected such as ammonia gas or alcohol gas moves in the capillary 26 of the lid 25 at a limited moving speed, the opening 22 of the case 21 and the gas permeable membrane The working electrode 11 is reached through 15a. The gas component of the detection target gas in this working electrode 11 sequentially undergoes oxidation or reduction reaction, and this reaction is output to the outside through an electrode pin connected to the working electrode 11.

  Further, the counter electrode 12 and the reference electrode 13 may be provided directly on the electrolyte holder 14 without using the gas permeable membrane 15b. Further, in the example of FIG. 1, a working electrode 11, a counter electrode 12, a reference electrode 13, and a sensor having three electrodes are shown, but in addition to this, the working electrode 11, the counter electrode 12, A sensor having an electrode may be used.

Next, examples of the above embodiment will be described. In all of the following examples, measurement was performed without the lid 25 attached in order to evaluate the original performance of the electrochemical gas sensor.
First, the characteristics of the electrochemical gas sensor of the present invention in a dry atmosphere will be described.

  As the electrochemical gas sensor of the present invention, two electrochemical gas sensors 10 having the structure shown in FIG. 1 as described above were prepared. First, PTFE sheets are used as the gas permeable sheets 15a and 15b, platinum (Pt) is used as a catalyst for the working electrode 11, the counter electrode 12, and the reference electrode 13, and a room temperature molten salt as an electrolyte is 1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate (1-Ethyl-3-methylimidazolium Trifluoromethanesulfonate) (hereinafter “ EMIMTf salt ”was selected, and 0.05 ml was injected into the electrolyte support 14 as a sufficient amount for impregnation. The structural formula of this EMIMTf salt is shown in Chemical Formula 1.

The electrochemical gas sensors of the present invention thus obtained were designated as Sample 1- (1) and Sample 1- (2).
Sample 1- (1) and Sample 1- (2) were exposed to 100 ppm of ammonia gas, and the sensor output after 2 minutes was measured. This was the initial output. Thereafter, Sample 1- (1) and Sample 1- (2) were placed in a dryer at a temperature of about 50 ° C. in a dry atmosphere of about 5 ° C. for 3 days in a dryer, and again with ammonia gas of 100 ppm. The sensor output 2 minutes after exposure was measured, and this was taken as the output 3 days later. Furthermore, after that, it was left in the same dry atmosphere for another 4 days, again exposed to 100 ppm of ammonia gas again, and the sensor output after 2 minutes was measured. This was the output after 7 days. The results are shown in Table 1.

  For comparison, two electrochemical gas sensors 1 having the structure shown in FIG. 2 are prepared as conventional electrochemical gas sensors, and 2M chloride generally used in an electrochemical gas sensor for detecting ammonia gas as an electrolyte. An electrochemical gas sensor was prepared using the same members as in Example 1 except that a lithium (LiCl) aqueous solution was used. At this time, 0.3 ml of the lithium chloride aqueous solution as the electrolyte was injected into the electrolyte solution reservoir 32. The conventional electrochemical gas sensor thus obtained is referred to as Comparative Example 1- (1) and Comparative Example 1- (2), as in Samples 1- (1) and 1- (2). The sensor output was measured after 3 days and 7 days when placed in an atmosphere. The results are also shown in Table 1.

From these results shown in Table 1, in Sample 1- (1) and Sample 1- (2) of the present invention using EMIMTf salt as a normal temperature molten salt as an electrolyte, 3 days and 7 days in a dry atmosphere at 50 ° C. Even when the sensor was placed, the sensor output changed slightly, but it was found that there was no significant change in output. On the other hand, in the comparative type 1- (1) and the comparative example 1- (2) of the conventional type using the lithium chloride aqueous solution as the electrolyte, the sensor output is already almost zero after 3 days in the dry atmosphere. Thus, it can be seen that it no longer functions as a gas sensor.
Further, when the inside of the sensor of Comparative Example 1- (1) and Comparative Example 1- (2) after 7 days in a dry atmosphere is examined, the lithium chloride aqueous solution evaporates in the electrolyte solution reservoir 32 and the electrolyte holder 14. It was in a dry state.
The same experiment was conducted with other types of room temperature molten salts, but no significant changes were observed in the sensor output when placed in a dry atmosphere at 50 ° C. for 7 days.

  Therefore, the electrochemical gas sensor of the present invention using a normal temperature molten salt as an electrolyte can be used in a dry atmosphere as compared with a conventional electrochemical gas sensor using an aqueous solution of a salt such as lithium chloride as an electrolyte. It can be seen that the sensor output does not change greatly and has high reliability.

  Next, gas sensitivity when various room temperature molten salts are used as the electrolyte when ammonia gas is selected as the detection target gas will be described.

An electrochemical gas sensor was prepared in the same manner as Sample 1- (1) in Example 1 except that 0.05 ml of room temperature molten salt shown in Table 2 was used as the electrolyte. It was set as Sample 2- (3).
Samples 2- (1) to 2- (3) were exposed to 100 ppm of ammonia gas, and the sensor outputs after 2 minutes were measured.
For comparison, as a conventional type electrochemical gas sensor, a sensor similar to Comparative Example 1- (1) of Example 1, that is, an electrochemical gas sensor using 0.3 ml of a 2M lithium chloride aqueous solution as an electrolyte was prepared. It was set as Comparative Example 2.

From these results shown in Table 2, in Samples 2- (1) to 2- (3) using a room temperature molten salt in which the nitrogen-containing aromatic cation is an alkylimidazolium ion, a comparative example using an aqueous lithium chloride solution Compared to 2, it can be seen that a preferable sensor output was obtained although the output was somewhat inferior.
In addition, when these samples 2- (1) to 2- (3) were tested in the same manner as in Example 1, they were in a dry atmosphere as in samples 1- (1) and 1- (2). It was confirmed that the sensor output was maintained even when placed.

Moreover, although the result in the case of using platinum as a catalyst material has been shown, the same experiment was conducted on ruthenium oxide (RuO ₂ ), gold (Au), and palladium (Pd) in addition to platinum. It was confirmed that a good sensor output was obtained.
Furthermore, as for the ambient temperature molten salt in which the cation is an alkylpyridinium ion or an aliphatic onium ion, for example, an aliphatic ammonium ion, the sensor output for ammonia gas was confirmed in the same manner. As a result, the above sample 2- (1) to sample 2- Although it is equivalent to (3) or slightly inferior, it was confirmed that sensor output was obtained.

  As described above, when ammonia gas is selected as the detection target gas, a normal electrochemical gas sensor is used when an ambient temperature molten salt whose cation is an alkylimidazolium ion, an alkylpyridinium ion, or an aliphatic onium ion is used as an electrolyte. It turns out that it is obtained.

  Next, gas sensitivity when various normal temperature molten salts are used as the electrolyte when alcohol gas is selected as the detection target gas will be described.

An electrochemical gas sensor was prepared in the same manner as Sample 1- (1) in Example 1 except that 0.05 ml of room temperature molten salt shown in Table 3 was used as the electrolyte. It was set as Sample 3- (3). In addition, about the sample 3- (2) and the sample 3- (3), since the vendor of the room temperature molten salt did not clarify the composition, the vendor and the model number are shown in Table 3.
Samples 3- (1) to 3- (3) were exposed to 100 ppm of ethanol gas as alcohol gas, and the sensor output after 2 minutes was measured. Table 3 shows the respective sensor outputs.
For comparison, an electrochemical gas sensor similar to Comparative Example 1- (1) of Example 1 was prepared as a conventional type electrochemical gas sensor except that 0.3 ml of 40% sulfuric acid was used as an electrolyte. It was.

From these results shown in Table 3, sample 3- (1) in which the cation is an alkylimidazolium ion is almost equivalent to Comparative Example 3 which is a conventional electrochemical gas sensor using sulfuric acid as an electrolyte. It can be seen that the sensor output can be obtained. On the other hand, Sample 3- (2) in which the cation is an alkylpyridinium ion and Sample 3- (3) in which the cation is an aliphatic ammonium ion are about 1/10 compared to Sample 3- (1) or Comparative Example 3. The sensor output was able to be obtained though it was about.
Note that although the results in the case of using platinum as the material of the catalyst, in addition to platinum, ruthenium oxide (RuO _2), gold (Au), was the same experiment also palladium (Pd), just as It was confirmed that a good sensor output was obtained.

Further, when the same tests as those of Example 1 were performed on these samples 3- (1) to 3- (3), they were in a dry atmosphere in the same manner as samples 1- (1) and 1- (2). It was confirmed that the sensor output was maintained even when placed.
Further, contrary to Example 1, when placed in a high humidity atmosphere at 60 ° C. and a relative humidity of 90% for 30 days, Comparative Example 3 leaks liquid due to an increase in volume due to moisture absorption of the electrolyte. However, in Samples 3- (1) to 3- (3), it was confirmed that the sensor output was maintained without causing liquid leakage.

  Further, as alcohol gas other than ethanol as a detection target gas, for example, methanol, 2-propanol, 1-butanol, and 2-octanol are measured in the same manner, but each sensor has a different sensitivity, but a suitable sensor output can be obtained. Was confirmed.

  Thus, when alcohol gas is selected as the gas to be detected, when an ambient temperature molten salt whose cation is an alkylimidazolium ion, an alkylpyridinium ion or an aliphatic onium ion is used as the electrolyte, a good electrochemical gas sensor It can be seen that

  Next, gas selectivity will be described when ammonia gas or alcohol gas is selected as the detection target gas.

First, as an electrochemical gas sensor whose detection target gas is ammonia gas, the same sensor as Sample 1- (1) to Sample 1- (2) of Example 1, that is, EMIMTf salt was used as a room temperature molten salt as an electrolyte. A sensor was prepared and used as Sample 4- (1).
For comparison, a sensor identical to that of Comparative Example 1 of Example 1, that is, a sensor using a 2M lithium chloride aqueous solution as an electrolyte was prepared, and this was designated as Comparative Example 4- (1).

Sample 4- (1) and Comparative Example 4- (1) were first exposed to 100 ppm of ammonia gas, which is a detection target gas, and the sensor output after 2 minutes was measured. Next, as a gas other than the detection target gas (hereinafter referred to as “miscellaneous gas”), carbon monoxide (CO) 100 ppm, hydrogen (H ₂ ) 100 ppm, hydrogen sulfide (H ₂ S) 10 ppm, sulfur dioxide (SO ₂ ) 30 ppm. The sensor output after 2 minutes when exposed to 10 ppm of nitric oxide (NO), 100 ppm of ethylene (C ₂ H ₄ ), 1% of carbon dioxide (CO ₂ ) and 100 ppm of methanol gas was also measured. Of these gas concentrations, hydrogen sulfide, sulfur dioxide, and nitric oxide, which are highly toxic gases, were set to 10 ppm or 30 ppm. From these results, the sensor output value of Sample 4- (1) and the sensor output value of Comparative Example 4- (1) were obtained, and the relative output with the output of ammonia gas, which is the detection target gas, set to 100, respectively. 4 shows.

  From the results shown in Table 4, the sample 4- (1) of the present invention using the EMIMTf salt as the ambient temperature molten salt as the electrolyte is compared with the conventional comparative example 4- (1) using the lithium chloride aqueous solution as the electrolyte. Thus, it can be seen that the miscellaneous gas sensitivity with respect to the detection target gas is low and the electrochemical gas sensor has excellent gas selectivity, and in particular, the gas selectivity with respect to carbon monoxide (CO) gas is particularly excellent.

Next, as an electrochemical gas sensor whose detection target gas is alcohol gas, the same sensor as Sample 3- (1) of Example 3, that is, 1-n-butyl-3-methylimidazolium as a room temperature molten salt as an electrolyte A sensor using trifluoromethanesulfonate (hereinafter referred to as “BMIMTf salt”) was prepared, and this was used as Sample 4- (2).
For comparison, five sensors identical to Comparative Example 1 of Example 3, that is, a sensor using 40% sulfuric acid as an electrolyte were prepared, and this was designated as Comparative Example 4- (2).

The sample 4- (2) and the comparative example 4- (2) were first exposed to 100 ppm of ethanol gas as an alcohol gas as a detection target gas, and the sensor output after 2 minutes was measured. Next, as miscellaneous gases, carbon monoxide (CO) 100 ppm, hydrogen (H ₂ ) 100 ppm, hydrogen sulfide (H ₂ S) 10 ppm, sulfur dioxide (SO ₂ ) 30 ppm, nitrogen monoxide (NO) 10 ppm, ethylene (C ₂ The sensor output after 2 minutes when exposed to 100 ppm of H ₄ ), 1% of carbon dioxide (CO ₂ ), and 100 ppm of ammonia gas was also measured. Of these gas concentrations, hydrogen sulfide, sulfur dioxide, and nitric oxide, which are highly toxic gases, were set to 10 ppm or 30 ppm. From these results, the sensor output value of Sample 4- (2) and the sensor output value of Comparative Example 4- (2) were obtained, and the relative output with the output of ethanol gas, which is the detection target gas, being 100, As shown in FIG.

From the results shown in Table 5, the sample 4- (2) of the present invention using BMIMTf salt as the room temperature molten salt as the electrolyte is compared with the conventional comparative example 4- (2) using sulfuric acid as the electrolyte. It can be seen that this is an electrochemical gas sensor with low miscellaneous gas sensitivity to the detection target gas and excellent gas selectivity, and particularly excellent gas selectivity with respect to carbon monoxide (CO) gas and ethylene (C ₂ H ₄ ). I understand that.

  Thus, it can be seen that the electrochemical gas sensor of the present invention using a room temperature molten salt as an electrolyte has excellent gas selectivity as compared with a conventional electrochemical gas sensor.

  The electrochemical gas sensor for detecting ammonia gas of the present invention is excellent in stability and gas selectivity, and can be suitably used for industrial gas sensors and environmental monitoring sensors mainly used in chemical factories. Furthermore, since it can be reduced in size and thickness, it can be used for applications such as portable measuring instruments and personal gas monitors.

  The electrochemical gas sensor for detecting alcohol gas of the present invention is excellent in stability and excellent in gas selectivity, and can be suitably used mainly for an ethanol gas sensor in breath for use in equipment and industrial applications. Furthermore, since the size and thickness can be reduced, it can be used for applications such as a portable breath ethanol checker and a portable bad breath checker.

It is sectional drawing of the electrochemical type gas sensor of one embodiment of this invention. It is sectional drawing of the electrochemical gas sensor of the conventional form.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Working electrode 12 Counter electrode 13 Reference electrode 14 Electrolyte holding body 15a, 15b Gas-permeable film 21 Case

Claims (4)

An electrochemical sensor having at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode,
The electrolyte is a molten salt composed of a nitrogen-containing aromatic cation or aliphatic onium cation and a fluorine-containing anion,
An electrochemical gas sensor, wherein the gas to be detected is ammonia gas. An electrochemical sensor having at least a working electrode and a counter electrode, and an electrolyte in contact with the working electrode and the counter electrode,
The electrolyte is a molten salt composed of a nitrogen-containing aromatic cation or aliphatic onium cation and a fluorine-containing anion,
An electrochemical gas sensor, wherein the gas to be detected is alcohol gas.   The electrochemical gas sensor according to claim 1 or 2, wherein the nitrogen-containing aromatic cation is an alkyl imidazolium ion or an alkyl pyridinium ion. 3. The electrochemical gas sensor according to claim 1, wherein the fluorine-containing anion is a borofluoride ion, a phosphorus fluoride ion, or a trifluoromethanesulfonate ion.

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