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

A novel solid‐state amperometric O 2 gas sensor based on the supported 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF 4 ) porous polyethylene membrane‐coated electrodes has been proposed with its characterization. By electrochemical impedance technique, the ionic conductivity of the supported EMIBF 4 membrane was estimated to be ca. 0.6 S m −1 , indicating that the supported EMIBF 4 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 O 2 /O 2 −. (O 2 −. : 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 O 2 at the supported EMIBF 4 membrane‐coated electrode system. The transient and steady‐state reduction currents for the reduction of O 2 to O 2 −. as well as the transient oxidation current for the reoxidation of O 2 −. to O 2 , which were obtained by potential‐step chronoamperometry, could be used to measure the change of O 2 concentration in O 2 ‐N 2 mixed gas stream. The present O 2 gas sensor demonstrated a wide detection range, a high sensitivity and an excellent reproducibility.