The preparation of reduced graphene oxide-encapsulated α-Fe2O3 hybrid and its outstanding NO2 gas sensing properties at room temperature

A novel graphene-encapsulated α-Fe2O3 hybrid was synthesized through the first hydrolysis process of Fe3+ ions in the colloidal solution of graphene oxide (GO) and following hydrothermal procedure. The energy dispersive X-ray spectrometry (EDS) data proved the existence and uniform distribution of C element in the hybrid. We further demonstrated the successful encapsulation of α-Fe2O3 grains by extremely small graphene pieces through transmission electron microscopy (TEM). As a proof-of-concept demonstration of the function, the as-prepared samples were utilized as gas-sensing materials to explore their potential applications. Results showed that the optimal hybrid exhibited a response of 8.2-5 ppm of NO2 at room temperature (RT), which was 3.9 times higher than that of undoped α-Fe2O3 (125 °C). The hybrid sensor also displayed a short response time of 2.1 min, an excellent NO2 selectivity, a long-term stability of 20 days and an extremely low detection limit of 50 ppb toward NO2 at RT. The significantly enhanced NO2 sensing properties could be attributed to much higher specific surface area, more defects and local p-n heterojunctions in the hybrid. We consider that our work could provide a fresh idea for the future design of high-performance room temperature gas sensors.