Co3O4 nanoparticle-decorated hierarchical flower-like α-Fe2O3 microspheres: Synthesis and ethanol sensing properties

Co3O4 nanoparticle-decorated hierarchical flower-like α-Fe2O3 microspheres were prepared via a facile two-step method and subsequent annealing. The structure, morphology and surface characteristics of the as-prepared products were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). Considering the potential applications, the gas sensing performances of the sensor based on α-Fe2O3/Co3O4 composites and pure α-Fe2O3 microspheres were investigated towards a series of volatile organic compounds. The response of hierarchical α-Fe2O3/Co3O4 composites sensor to 100 ppm ethanol at operating temperature of 170 °C is about 16.1, which is twice as much as the pure α-Fe2O3 microspheres sensor at 300 °C. Moreover, a dramatic reduction of response/recovery time (3.3 s/5.4 s) has been achieved at different operating temperature. The enhanced sensitivity performance is mainly due to its unique hierarchical structure, which provides high surface area, a large number of active sites, and the synergistic effect between n-type α-Fe2O3 and p-type Co3O4.