High NH3 sensing performance of NiO/PPy hybrid nanostructures

•NiO/PPy hybrid films synthesized by simple vapour-phase polymerization.•NiO/PPy ratios obtained by regulating FeCl3 oxidant contents on NiO-nanoparticles.•NiO/PPy hybrid films having high sensing performance of response, selectivity, and reversibility to NH3 gas.•Experimental results verified the existence of NiO/PPy hybrid structure. In this work, NiO/PPy hybrid nanostructured films were fabricated by chemical vapor-phase polymerization using NiO nanoparticles films drop-coated FeCl3 oxidant on Al2O3 substrates. The NiO nanoparticles with a size of about 20 nm were synthesized by a hydrothermal method. Different ratios between NiO and PPy in the NiO/PPy hybrid films were modified by regulating FeCl3 oxidant content when using FeCl3 solutions with concentrations of 0.15, 0.2, 0.4, 0.8, and 1.5 M. X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, and Raman scattering spectroscopy were used to analyze specific material characteristics of these films. The gas-sensing performance of the films was examined by exploring their resistances responding to NH3, NO2, H2, CO, and relative humidity at an operating temperature range from 25 to 110 °C. The NiO/PPy hybrid films presented to have a very high sensitivity to NH3 gas in comparison to the non-hybrid films based on only NiO or PPy. The highest sensitivity to NH3 gas (the sensing response S = 246.6 % for 350 ppm at 25 °C) was found for the NiO/PPy film with the used 0.2 M FeCl3 oxidant solution. The gas-sensing performance of the NiO/PPy films was suggested by the main contribution of the hybrid nanostructure between NiO nanoparticles and PPy.