Materials Research Bulletin, Vol.116, 44-49, 2019
The synergistic effect of fluorination and embedded SnO2 on the NO gas sensing of expanded graphite
To achieve high-performance nitric oxide (NO) gas sensing, expanded graphite (EG) was modified with SnO2 and fluorine functional groups. SnO2 was introduced into EG with an aqueous solution of SnCl2, whereas the fluorine functional groups were introduced via fluorine gas. The properties of the samples were analyzed by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and NO gas sensing. A SnO2 phase from the SnCl2 solution formed on and uniformly coated the EG surface. The number of fluorine functional groups increased with increasing fluorination temperature. The EG/SnO2 fluorinated at 400 degrees C exhibited the highest NO gas sensitivity (5.2%). The SnO2 induced the adsorption of NO gas, and the fluorine functional groups transferred electrons from the EG surface to the NO gas adsorbed onto SnO2. Therefore, the high NO gas sensitivity is attributed to the synergistic effect of the introduced SnO2 and fluorine functional groups.