Electrochemical gas sensor

Details Electrochemical gas sensor Electrochemical gas sensor

1989-04-28

1993-06-01

Tung, T.

Chemistry: electrical and wave energy

Apparatus

Electrolytic

204415, 204424, 204426, 204431, G01N 27407

Patent

active

052156435

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL BACKGROUND OF THE INVENTION

This invention relates to electrochemical gas sensors and, more particularly, to devices electrochemically sensing gases of electrolytic type detecting and determining the quantities of predetermined gas components with an electrolytic reaction utilized.
The electrochemical gas sensors of the kind referred to are high in the sensitivity so that they may be effectively utilized in detecting, for example, industrial use gas concentration, an excessive indoor presence over a predetermined level of such a predetermined gas as CO gas and the like, and so on.


DISCLOSURE OF PRIOR ART

For the electrochemical gas sensors of the kind referred to with the electrolytic reaction utilized, various ones employing an electrochemical element have been suggested in, for example, U.S. Pat. No. 4,227,984 to Russell M. Dempsey et al which showing to employ such polymeric solid electrolyte as sulfonated perfluorocarbon, and U.S. Pat. No. 4,265,714 to Mary E. Nolan et al. In the known electrochemical element, there are provided on one surface of a membrane formed by a solid electrolyte with active and reference electrodes, and on the other surface with an active electrode.
There have arisen various problems, on the other hand, in the foregoing sensors. In particular, for the sensors suggested by Dempsey et al and Nolan et al, they have been defective in that they are difficult to be made compact, thin and minimized in size, the structure of providing the electrodes on both sides of the membrane renders their manufacturing complicated, improper to be mass-produced and to be of high cost, while involving also a problem in respect of characteristic stabilization.


DISCLOSURE OF THE INVENTION

A primary object of the present invention is, therefore, to provide an electrochemical gas sensor which assures a compact arrangement to render the sensor to be thin and small, increases the sensitivity with the ionic conduction remarkably improved, and also increases the durability to a large extent.
According to the present invention, the above object can be attained by providing an electrochemical gas sensor comprising an insulating substrate, active and counter electrodes disposed on one and the same surface of the insulating substrate as mutually spaced and to have respectively reactive portions, a reference electrode provided as spaced from the active and counter electrodes and having a reactive portion, a solid electrolyte layer formed to cover and across at least the reactive portions of the active, counter and reference electrodes, and means giving at least to said active electrode an influence for improving and stabilizing the sensitivity to gases.
Other objects and advantages of the present invention should be made clear in the following description of the invention detailed with reference to preferred embodiments shown in accompanying drawings.


BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a perspective view of the electrochemical gas sensor in an embodiment according to the present invention;
FIG. 2 is a fragmentary plan view as magnified of the sensor shown in FIG. 1;
FIG. 3 is a graph showing a detection current responsive to inflow time of CO gas into the sensor of FIG. 1;
FIG. 4 is a graph showing a detection current responsive to inflow time of ethanol (EtOH) gas into the sensor of FIG. 1;
FIG. 5 is a graph showing a detection current responsive to the CO gas inflow time into a known sensor in which no reference electrode is disposed between the active and counter electrodes;
FIG. 6 is a graph showing a detection current responsive to the EtOH gas inflow time into the same sensor as in FIG. 5;
FIG. 7 is a graph showing a potential of the reference electrode of Au responsive to the CO gas inflow time into the sensor of FIG. 1;
FIG. 8 is a graph showing a detection current responsive to the CO gas inflow time into the sensor having the reference electrode of Au in FIG. 1;
FIG. 9 is a graph showing a potential of the reference electrode of Pt in a known sensor responsive to the CO gas

REFERENCES:
patent: 4020830 (1977-05-01), Johnson et al.
patent: 4171253 (1979-10-01), Nolan et al.
patent: 4521290 (1985-06-01), Venkatasetty
patent: 4795543 (1989-01-01), Setter et al.
patent: 4812221 (1989-03-01), Madou et al.
patent: 4865717 (1989-09-01), Setter et al.
patent: 4900405 (1990-02-01), Otagawa et al.
patent: 4913792 (1990-04-01), Nagata et al.
Translation of JP Utility Model Laid Open 55-64760 (May 1980).

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