Improvement of characteristics of amperometric Cl₂ and COCl₂ gas sensors by ion irradiation into the gas permeable membranes

Abstract

  Electrochemical sensors based on electrolysis of chlorine (Cl₂) and phosgene (COCl₂) gas have been developed by using gas permeable membrane modified by ion irradiation technique. An expanded polytetrafluoroethylene (ePTFE) membrane is a chemically stable substance and has high permeability of gases without permeation of electrolytic solutions. In this study, gas permeable membrane of ePTFE has been made of ion irradiation of Ne⁺ with a fluence of 1×10¹⁵ ions/cm². After ion-irradiation into ePTFE, Ag was coated by a vacuum evaporation method, which was used as a working electrode to construct the electrochemical gas sensors for Cl₂ and COCl₂. The sensitivity for Cl₂ and COCl₂ of the sensors used the ion-irradiated ePTFE membrane showed significant enhancement, which was more than 3.8 and 1.3 times higher than that of non ion-irradiated one. Morphology change of ePTFE by ion irradiation was observed by scanning electron microscopy. The enhancement of the sensitivity by the ion irradiation is due to changing of active nature of the Ag electrode and increase of the effective surface area.