Amperometric nitrogen dioxide gas sensor: preparation of PAn/Au/SPE and sensing behaviour

Au/Nafion® and PAn (polyaniline)/Au/Nafion® were prepared by Takenaka–Torikai (T–T) chemical plating and the electrochemical polymerisation methods, respectively. Using Au/Nafion® as a working electrode, the sensitivity of NO2 gas sensor was obtained as 2.28 μA ppm−1 when the gas flow rate was >300 ml min−1. The potential window for limiting current was in the range of 0.3–0.1 V (versus Ag/AgCl/3 M NaCl aqueous solution) by using PAn/Au/Nafion® as a working electrode. The sensitivity of NO2 gas sensor decreased from 2.54 to 1.40 μA ppm−1 when the potential for preparing PAn/Au/Nafion® increased from 0.8 to 1.0 V and gas flow rate was 300 ml min−1. The diffusion resistance of NO2 through the gas film can be neglected for the gas flow rate >300 ml min−1 when Au/Nafion® and PAn/Au/Nafion® prepared at 0.8 and 0.9 V were used as working electrodes.