Humidity Sensing Behaviour of Lyophilized rGO/Fe2O3 Nanocomposite

For the purpose of humidity sensing, the rGO/Fe 2 O 3 nanocomposite was synthesized through precipitation technique that is followed by lyophilization process to enhance the surface area of the prepared nanocomposite. In order to investigate the sensor preparation quality, its activity and efficiency, the prepared nanocomposite has undergone different characterization techniques such as; high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermo-gravimetric analysis (TGA), BET surface area and BJH pore diameter distribution. The study showed that Fe 2 O 3 nanoparticles are densely and homogeneously loaded over rGO sheets. The porosity and surface area play an important role on humidity sensing property. In addition, the BET surface area and BJH pore radius of the rGO/Fe 2 O 3 are found to be 2002.09 m 2 g −1 and 1.68 nm, respectively. Furthermore, the humidity-sensing performances were investigated in a wide range of working humidity (11–97% RH) and frequency (100 Hz–100 kHz). The obtained results confirmed that the optimum measuring frequency is 1 kHz, due to in inability of water molecule to be polarized at higher frequency. The humidity sensing performance of rGO/Fe 2 O 3 nanocomposite shows a parabola relationship with the RH value from 11 to 97%. The incorporation of Fe 2 O 3 into rGO creates more active sites, such as vacancies and defects which promote the adsorption of water molecule thereby increasing the sensitivity of the sensor. Molecular models of graphene; graphene/2Fe 2 O 3 , graphene/2Fe 2 O 3 /2H 2 O were built. The model suggested that decorating the graphene with 2Fe 2 O 3 enable it to be sensitive for humidity.