Adsorption kinetics of NO₂ gas on oxyfluorinated graphene film

We report the fabrication of high-performance NO₂ gas sensors based on oxyfluorinated graphene (OFG) layers. At room temperature, the times of adsorption/desorption of NO₂ on/from the surface of thin OFG films are less than 1200 s and can be reduced by increasing the operation temperature. The sensors are capable of detecting NO₂ molecules at sub-ppm level with a sensitivity of 0.15 ppm^-1 at 348 K. The temperature dependence of the rate constants shows that the simultaneous presence of a large number of fluorine- and oxygen-containing groups on the graphene surface provides the formation of low-energy sites (ΔH_a < 0.1 eV) for NO₂ adsorption. The combination of the high sensitivity of the sensor and a reasonable adsorption/desorption time of the analyte is promising for on-line monitoring.