Predominant hydroxyl group reduction for gas sensitivity control in graphene oxide

Abstract Reduced graphene oxide (rGO), prepared via thermal reduction, was studied as a gas sensing material for detecting NO, NO2, ethanol, and NH3. Structural analysis using X-ray diffraction (XRD) and Raman spectroscopy revealed that rGO maintained a partially disordered layered structure with residual oxygen functionalities, indicated by a broadened (001) peak and a high D/G intensity ratio. X-ray photoelectron spectroscopy (XPS) confirmed selective removal of hydroxyl groups and enrichment of sp2-hybridized C = C bonds, highlighting surface chemical tuning. SEM imaging showed a wrinkled and loosely stacked morphology uniformly covering the electrode surface, contributing to a large surface area and stable interfacial contact. Gas sensing properties were assessed by monitoring resistance changes across various gas concentrations (2–10 ppm). The rGO sensor demonstrated strong, gas-specific, and concentration-dependent responses: ~ 50% for NO at 10 ppm, 27% for ethanol at 2 ppm, 25% for NH3 at 5 ppm, and 17% for NO2 at 10 ppm. Time-resolved measurements revealed faster response and recovery for NO and NO2 than for NH3 and ethanol. These findings suggest that thermally reduced rGO, with its defect-rich structure, favorable morphology, and optimized surface chemistry, holds significant potential for use in selective and sensitive gas sensing applications.