JP4730818B2 - Electrode body for constant potential electrolysis gas detector for hydrogen detection - Google Patents

Description

  The present invention relates to an electrode body suitable for a constant potential electrolytic gas detector that detects a concentration of a test gas by an electrolytic current at that time by subjecting the test gas to an electrolyte and electrochemically oxidizing or reducing the reaction. In particular, the present invention relates to a structure of an electrode body having selectivity for hydrogen.

For example, in a constant potential electrolysis gas detector, the gas concentration is detected from the magnitude of the electrolysis current generated between the test gas and the counter electrode by bringing the surface of the working electrode into contact with the electrolyte.
As described in Patent Document 1, such a working electrode improves the gas permeability by forming protrusions on at least one surface of the porous fluororesin plate by plasma ion etching, and also has a catalyst on the protrusion surface side. It has been proposed to improve the sensitivity by forming a conductive film having an action.
However, the base material is easily damaged and there is a problem in reliability.
In Patent Document 2, in order to increase the oxygen permeability of the polyimide resin film containing fluorine, H +, He in a range where the dose amount φ is 1 × 10 10 pieces / cm 2 ≦ φ ≦ 1 × 10 16 pieces / cm 2. Although it is described that ions such as +, C +, N +, O +, Na +, N2 +, O2 +, Ar +, and Kr + are implanted, the resin film containing fluorine is originally a gas. Not only is it unclear whether it can be used for the electrode body of the detector, but it is also unclear whether a membrane having high selectivity and sensitivity to hydrogen can be provided, or to obtain such characteristics. The ionic species are not specified.
JP-A 64-31043 Japanese Patent Laid-Open No. 2003-62422

  The present invention has been made in view of such problems, and its object is to provide an electrode for a potentiostatic gas detector having selectivity for hydrogen without causing liquid leakage or an increase in electrical resistance. Is to provide a body.

In order to achieve such a problem, in the present invention, at least one of O and N is injected into at least one of the surfaces of the porous fluororesin plate from 10 15 to 10 17 or less per square centimeter. Thus, a conductive film having a catalytic action is formed on the surface.

  Oxygen and nitrogen injection increase the number of OH groups, improving the selectivity and sensitivity to hydrogen.

Therefore, details of the present invention will be described below based on the illustrated embodiment.
As a diaphragm of the gas detector, a fluorine-based porous film having a balance between water repellency and gas permeability is accommodated in a bell jar of a 200 kV ion implantation apparatus, and acceleration energy is several MeV, preferably 10 keV to 2 MeV, an ion beam. Of H, He, C, N, O, Na, N2, O2, Ar, Kr, etc., which are known as ion species that do not excessively destroy the structure of the polymer film at a current of 3 μA / cm 2 or less, O, N At least one of these is implanted with 10 <17> or less, for example, 10 <15> or 10 <16> per square centimeter to produce film samples, and these films have a catalytic action on the ion implantation side An electrode was formed to prepare a sample. The electrode can be formed by vapor deposition or sputtering of one or more of gold, platinum, and platinum-gold alloy.

When these samples were incorporated as working electrodes of a constant potential electrolytic gas detector and the output against 2500 ppm of hydrogen was measured, the results shown in FIG. 1 were obtained.
In FIG. 1, symbols A to D represent nitrogen implanted to the 10 15th power per square centimeter, and symbols F represent 10 16 power implanted, and symbols G to J represent 10 15th power per square centimeter. , And the symbol K indicate those in which oxygen is implanted to the 16th power.

  From this, it was found that the selectivity (detection sensitivity) with respect to hydrogen was twice or more than that of the other samples in which O or N was injected to the 10 16th power per square centimeter (symbol K).

Further, when the membrane thus obtained was analyzed with an FFIR analyzer, the sample K contained much more OH groups than the other samples, which contributed to the improvement in selectivity (sensitivity) to hydrogen. It is estimated that
The reason why O and N are less than 10 to the 15th power is unclear as compared to the 10th to the 16th power.

  As a precaution, when O and N are irradiated more than 10 to the 17th power, the polymer membrane is damaged, but the gas permeability is less than 10 to the 17th power though the OH group of the polymer film increases. There is a problem that the sensitivity is lower than that of irradiation and improvement in sensitivity cannot be expected.

  Similarly, when the ion beam current is higher than 3 μA / cm 2, there is a problem that the temperature of the polymer film as a target rises, the deterioration of the polymer material progresses, and the gas permeability decreases.

It is a figure which shows the relationship between the amount of ion implantation, and the detection output with respect to hydrogen. It is a figure which shows the result of having analyzed the component of the film | membrane.

Claims (1)

At least one of O and N is injected into at least one surface of the porous fluororesin plate over 10 15 to 10 17 per square centimeter, and a conductive film having catalytic action is formed on the surface. Electrode body for constant potential electrolytic gas detector for hydrogen detection.

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