An amperometric solid-state NO2 sensor with a solid polymer electrolyte and a reticulated vitreous carbon indicator electrode

Reticulated vitreous carbon (RVC) was tested as a material for the preparation of the indicator electrode in solid-state gas sensors. The test planar sensor contained a RVC indicator, a platinum auxiliary and a Pt/air reference electrode, with a solid polymer electrolyte (SPE) of 10% PVC, 3% tetrabutylammonium hexafluorophosphate (TBAHFP) and 87% of 2-nitrophenyloctyl ether (NPOE). The analyte, gaseous nitrogen dioxide in air, was monitored by reduction at −500 mV vs. the Pt/air electrode. The reduction current was linearly dependent on the analyte concentration over the whole test range, from 0.2 to 2.2 ppm (v/v). The sensitivity of determination amounted to 277 nA/ppm, the limit of detection was 80 ppb (at a relative humidity, RH, of 54%) and 90% of the steady-state signal was attained within 19 s. The measuring sensitivity depended on the temperature, the gas flow rate and the RH with slopes of 1.04% per 1°C, 32% per 1 ml/s and 0.16% per 1% RH, respectively. It has been demonstrated that RVC can successfully replace noble metals in gas solid-state sensors.