Improvement of gas sensitivity for a polymer membrane electrode by high-energy ion beam irradiation

Abstract

In industrial applications and environmental monitoring, amperometric gas sensors are very useful for detecting H 2 and toxic gases. Expanded polytetrafluoroethylene (ePTFE) membrane was modified by high-energy ion beam irradiation to improve its gas sensitivity. The membrane was irradiated with N and Kr ion beams at energies of 5 MeV/nucleon and 4 MeV/nucleon, respectively, at fluences ranging from 1×10 12 to 1×10 13 ions/cm 2 . The energy loss of irradiated ions was simulated by the stopping and range of ions in matter. The irradiated ePTFE surfaces were characterized by field-emission scanning electron microscopy and Raman spectroscopy. The characteristic currents for H 2 and toxic gases were measured by sensors equipped with non-irradiated and irradiated membranes. Chemical bonds were broken and the pore size increased with increasing fluences. The characteristic currents for H 2 and toxic also increased with increasing fluences. The CO gas sensitivity of N-irradiated ePTFE reached a maximum of only 212%. Meanwhile, I g /I 0 for CO sensing was significantly enhanced by Kr-irradiation at a fluence of 5×10 12 ions/cm 2 . This is due to the porous and amorphous structure on the membrane surface induced by ion beam irradiation. Thus, heavy ion irradiation was effective for improving gas sensitivity.