Development of Electrochemical CO Gas Sensor Using Expanded Polytetrafluoroethylene Membrane Modified by Ion Implantation

An amperometric gas sensor based on electrolysis of CO gas has been developed by using gas permeable membrane modified by ion implantation technology. Expanded polytetrafluoroethylene (ePTFE) membrane has chemically stable nature and high permeability of gases without permeation of electrolytic solutions. Ion implantations of several kinds of ion into ePTFE membranes with fluenses of 1×1014∼5×1015 ions/cm2 was carried out to modify the gas permeable membranes. Gas permeable electrodes were prepared by Au coating on the ion-implanted ePTFE membranes. For CO detection, sensors constructed with the ion-implanted gas permeable electrode showed 5.5∼38 times higher sensitivity than that used non-ion-implanted one. Morphology change observed by SEM showed increase of effective surface area of the electrodes using ion implanted into ePTFE membrane. The increase of electrode surface area enhances sensor sensitivity, however, the enhancement depends on reactive gas species. For CO detection, the enhancement, response current ratio of sensor used ion-implanted membrane against that used non-ion-implanted, is remarkably high in comparison with that for the other gases such as H2S and NO except H2. In the case of CO detection, the modification of membranes brings active nature of electrode process of CO oxidation, which improves selectivity of CO. The surface modification of ePTFE will be useful method for development of a practical CO gas sensor.