JP2010085130A - Electrochemical gas sensor and operation electrode thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical gas sensor detecting irritating poisonous gas selectively with high sensitivity. <P>SOLUTION: In the electrochemical gas sensor formed, by immersing an operational electrode member 10 and a counter electrode 22 into an electrolyte 24, particles 12 constituted of gold (Au) having an average particle size of not more than 4 nm in a sheet-like base material 11, consisting of carbon fiber are dispersed and held in the operation electrode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrochemical gas sensor that detects a gas concentration using an oxidation catalyst formed on a gas permeable membrane as a working electrode.

The electrochemical gas sensor is configured by immersing a working electrode in which a conductive oxidation catalyst layer is formed on a breathable porous membrane having water repellency, a counter electrode, and a reference electrode in an electrolytic solution.
Platinum black is usually used as the conductive oxidation catalyst layer, but the selectivity is low, especially the sensitivity to the inert gases such as mustard and lewisite is low, and the improvement of the sensitivity to these gases has been demanded. .

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electrochemical gas sensor that can selectively detect an inert gas with high sensitivity.
Another object of the present invention is to provide a working electrode suitable for the electrochemical gas sensor.

  In order to achieve such a problem, in the present invention, in an electrochemical gas sensor configured by immersing a working electrode and a counter electrode in an electrolytic solution, the working electrode is an average of a sheet-like base material made of carbon fiber. It consists of dispersed and held gold (Au) particles with a particle size of 4 nanometers or less.

  According to the present invention, an inert gas such as mustard gas can be detected with high selectivity and sensitivity.

Details of the present invention will be described based on the illustrated embodiments.
Reference numeral 10 in the figure denotes a working electrode member characterized by the present invention, which is fixed in a liquid-tight state to a gas inlet 21 of a case 20 that contains an electrolytic solution 24. The counter electrode 22 corresponds to the concentration of the gas to be measured. And an electrolysis current between them. Reference numeral 23 in the figure denotes a reference electrode.

The working electrode member 10 has an average particle size of 4 nanometers between a conductive and breathable base material 11 formed by, for example, forming carbon fibers into a sheet shape by punching or compression, and fibers constituting the base material. It is configured by dispersing and holding gold (Au) particles 12 of a meter or less.
If necessary, a porous sheet 13 having air permeability and water repellency may be adhered to the measured gas inflow side in order to prevent leakage of the electrolyte.

  The gold particles are dispersed and retained by reducing chloroauric acid with NaBH4 and growing to an average particle size of 4 nanometers by heating to form particles. The process consists of a process of suspending and uniformly impregnating the base material 11 and finally heating to about 300 ° C. to volatilize the liquid.

  The gold particles 12 thus dispersed were dispersed on the surface of each fiber 11a constituting the substrate, and it was confirmed by a transmission electron microscope (TEM) that the fiber was modified with the gold particles.

  Next, 0.1 g of a 0.3 mm-thick base material is prepared, and a working electrode member with a different amount of gold particle modification is manufactured on this to produce a baseline drift as a sensor and sensitivity to the gas to be measured (mustard gas). As a result, the results shown in FIG. 2 (a) and FIG. 2 (b) were obtained.

  That is, as is clear from FIG. 2 (a), the modification amount of the gold particles and the baseline drift are almost proportional, and as is clear from FIG. 2 (b), the maximum sensitivity to the mustard gas is obtained. The modification amount of the gold particles shown was found to be 1 μg peak when converted to a base material having a thickness of 0.3 mm and 0.1 g.

  That is, the relationship between the modification amount of the gold particles and the S / N ratio was found to have a peak of 0.5 μg of gold particles with respect to a substrate having a thickness of 0.3 mm and 0.1 g as shown in FIG.

  Based on these results, a working electrode member in which about 0.5 μg of gold particles was dispersed in a base material having a thickness of 0.3 mm and 0.1 g was manufactured, and the response to the mustard gas and the linearity were investigated. As shown in FIG. 4, the responsiveness was faster than a normal electrochemical gas sensor using platinum black.

  On the other hand, it was confirmed that the concentration of the mustard gas and the detected value remained almost linear as shown in FIG.

  Finally, when the interference with various gases was investigated, the results shown in Table 1 were obtained. That is, the sensitivity was very low for gases such as CO, NO, NO2, SO2, Cl2, and NH3 present in the atmosphere, and the sensitivity was also low for semiconductor material gases (AsH3, B2H6, PH3, SiH4). . This confirmed that mustard can be detected with high sensitivity and selectivity.

  In the above-described embodiment, a breathable porous film having water repellency is disposed on the measured gas inflow side in order to surely prevent leakage of the electrolyte, but the conductive base material has sufficient water repellency. Obviously, it is not necessary if Further, in the above-described embodiment, the three-pole type provided with the reference electrode has been described. However, it was confirmed that the same effect can be obtained even when used as a working electrode of a two-pole type gas sensor having only a working electrode member and a counter electrode. .

Drawing (a), (b) is a photograph which replaces with sectional drawing which shows one example of the electrochemical gas sensor of the present invention, and drawing which expands and shows a working electrode member, respectively. Figures (a) and (b) are graphs showing the relationship between the modification amount of the gold particles, the baseline drift, and the signal intensity, respectively. It is a diagram which shows the relationship between the modification amount of a gold particle, and S / N ratio. It is a figure which shows responsiveness. It is a diagram which shows the relationship between the density | concentration of to-be-measured gas, and an output.

Explanation of symbols

10 Working electrode member 11 Substrate made of conductive and breathable fibers 12 Gold (Au) particles with an average particle size of 4 nanometers or less 13 Porous sheet 22 Counter electrode 24 Electrolyte

Claims (3)

In an electrochemical gas sensor configured by immersing a working electrode and a counter electrode in an electrolyte,
An electrochemical gas sensor in which the working electrode is configured by dispersing and holding gold (Au) particles having an average particle diameter of 4 nanometers or less of a sheet-like base material made of carbon fiber. 2. The electrochemical gas sensor according to claim 1, wherein a gas permeable membrane having air permeability and water repellency is disposed in close contact with the gas inflow side of the working electrode. A working electrode for an electrochemical gas sensor configured by dispersing and holding gold (Au) particles having an average particle diameter of 4 nanometers or less on a sheet-like base material made of carbon fiber.

Images