Room-Temperature NO2 Gas Sensors Based on Granulated Carbon Nanofiber Material

Room-temperature gas sensors based on granulated carbon nanofiber material were investigated for the detection of NO2. The granulated material consisting of intertwined carbon nanofibers was synthesized by the decomposition of CH4 over the Ni/Al2O3 catalyst in a vibro-fluidized bed reactor. Carbon material was investigated using transmission electron microscopy, Raman spectroscopy, low-temperature nitrogen adsorption, and X-ray photoelectron spectroscopy. Investigation of the gas sensors towards NO2 at room temperature (25 +/- 2 degrees C) was carried out in a dynamic flow-through setup in the range from 1 to 500 ppm. A comparison of the sensitivity gas sensor to NH3 and CH4 was also given. The sensor based on non-treated carbon nanofiber material showed the response Delta R/R-0 of 5.1 % to 10 ppm of NO2. It was found that the sensor response to NO2 decreased when increasing the relative humidity. The effect of the relative humidity was more pronounced for low concentrations of nitrogen dioxide and decreases with a further increase in them.