Synthesis and characterization of polypyrrole/molybdenum oxide composite for ammonia vapour sensing at room temperature
M. Shariq, Ahmad Husain, Mahfoozurrahman Khan, Anees Ahmad
Abstract
In this study, polypyrrole (PPy) and polypyrrole/molybdenum oxide composite (PPy/MoO 3 ) were synthesized by the chemical oxidative method in an aqueous medium, using anhydrous ferric chloride (FeCl 3 ) as an oxidant. The successful preparation of materials was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance electron microscopy (TEM). PPy and PPy/MoO 3 were converted into pellets which were used as the sensor. A four-in-line probe device was used for studying DC electrical conductivity–based ammonia vapour–sensing properties at three different ammonia concentrations, that is, 1 M, 0.5 M and 0.1 M. The PPy/MoO 3 sensor showed much-improved sensing performance than the PPy sensor in terms of % sensing response and reversibility. PPy/MoO 3 sensor showed excellent selectivity for ammonia vapours against various VOCs. The % sensing response of PPy/MoO 3 sensor towards ammonia was found to be 2.19, 2.50, 3.16, 3.87, 4.1, 5.15, 6.19, 6.55 and 7.77 times greater than ethanol, methanol, acetone, acetaldehyde, formaldehyde, toluene, benzene, chloroform and n-hexane, respectively. In the end, a sensing mechanism was also proposed, which is based on rapid adsorption–desorption of ammonia molecules on the PPy/MoO 3 sensor’s surface.