rGO functionalized α-Fe2O3/Co3O4 heterojunction for NO2 detection

To improve α-Fe2O3 gas sensing properties the composites of α-Fe2O3/Co3O4 heterojunction decorated with rGO were prepared via hydrothermal, chemical bath deposition (CBD) and thermal reduction methods. Structure and morphology characterizations of the as-prepared products were proved by X-ray diffraction (XRD), Raman spectra (Raman), Scanning electron microscope (SEM),Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Ultraviolet and visible spectrophotometry(UV–vis). Gas-sensing measurements revealed that the ternary composite of α-Fe2O3/Co3O4-5 min-rGO-0.15 wt% showed high response of 17.64 at 130 °C towards 2 ppm NO2, which is 6.17 times and 1.46 times higher than that of pure α-Fe2O3 (2.86) and binary composite of α-Fe2O3/Co3O4-5 min (12.16) and faster response/recovery time compared with published NO2 sensors based on α-Fe2O3. The enhanced sensing mechanism was also discussed in detail, which is attributed to the synergistic effects aroused by the as-formed p-n heterojunctions and modification of rGO. The work shed a new light to design p-n junction composites and fabricate high performance NO2 sensors.