Amperometric nitrogen dioxide gas sensor based on PAn/Au/Nafion® prepared by constant current and cyclic voltammetry methods

Polyaniline (PAn) was electro-deposited on Au/Nafion® by the cyclic voltammetry (CV) and constant current (CC) methods, respectively. The electrochemical properties and surface morphologies of PAn/Au/Nafion® were characterized by SEM, cyclic voltammetry, and ac impedance, respectively. The maximum BET surface area was found to be 10.36 m2 g−1 for PAn/Au/Nafion® prepared by CV method with cycle number of 25 in 1.0 M HClO4 aqueous solution. Using PAn/Au/Nafion® prepared by CV method in 1.0 M HClO4, 1.0 M HCl, and 0.5 M H2SO4 aqueous solutions as working electrodes, the sensitivities of NO2 gas sensors with a gas flow rate of 300 ml min−1 were evaluated to be 3.04, 2.68, and 2.54 μA ppm−1, respectively. Using PAn/Au/Nafion® prepared with CC method to fabricate NO2 gas sensor, the sensitivity decreased from 2.35 to 1.41 μA ppm−1 when the current density for preparing PAn/Au/Nafion® increased from 1 to 10 mA cm−2.