A Novel Amperometric O2 Gas Sensor Based on Supported Room‐Temperature Ionic Liquid Porous Polyethylene Membrane‐Coated Electrodes

A novel solid-state amperometric O2 gas sensor based on the supported 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) porous polyethylene membrane-coated electrodes has been proposed with its characterization. By electrochemical impedance technique, the ionic conductivity of the supported EMIBF4 membrane was estimated to be ca. 0.6 S m−1, indicating that the supported EMIBF4 membrane (the thickness: 50 μm) can be used as a solid state ionic conductor at room temperature. The cyclic voltammograms obtained for the one-electron redox reaction of O2/O2−.(O2−.: superoxide ion) couple at high scan rates (>100 mV s−1) showed a couple of usual redox peaks, while at low scan rates (<30 mV s−1) S-shaped steady-state voltammograms similar to those obtained by rotating disk voltammetry were obtained. These results were explained on the basis of the mass transport of O2 at the supported EMIBF4 membrane-coated electrode system. The transient and steady-state reduction currents for the reduction of O2 to O2−.as well as the transient oxidation current for the reoxidation of O2−.to O2, which were obtained by potential-step chronoamperometry, could be used to measure the change of O2 concentration in O2-N2 mixed gas stream. The present O2 gas sensor demonstrated a wide detection range, a high sensitivity and an excellent reproducibility.