The critical role of hydroxyl groups in water vapor sensing of graphene oxide

Excellent adsorption of water vapor on the surface of graphene oxide ( GO), which contains several inherited functional groups, leads to the development of improved humidity monitoring systems that can urgently meet the high industrial demand. In this study, we fabricated a GO- based humidity sensor and investigated the influence of hydroxyl group concentration on its performance. The sensor exhibited excellent humidity sensing performance in terms of sensitivity ( sensor response 40 for 90% RH), selectivity, stability ( both long- term and short- term) and reaction time ( sres 1/4 8.5 s and srec 1/4 13 s). Additionally, this sensor does not require external power consumption for heating; thus, the aforementioned performance ( recorded at room temperature) with an applied voltage of 0.1 V can significantly reduce the power/ energy consumption to about 1.314 10 4 kW h per year. In the future, this type of sensor can be integrated into smart humidity monitoring systems to not only monitor but also control the humidity levels on a specific application area. Based on complementary characterization techniques, such as XRD, AFM, Raman and electrical measurement, here, we propose a physicalchemical sensing model to elucidate the aforementioned sensor characteristics.