Hollow SnO2/alpha-Fe2O3 spheres with a double-shell structure for gas sensors

Double-shell SnO2/alpha-Fe2O3 hollow composites were synthesized by a low-cost and environmentally friendly hydrothermal strategy. Various techniques were employed for the characterization of the structure and morphology of hybrid nanostructures. The results revealed that the alpha-Fe2O3 nanorods grew epitaxially on the surface of hollow SnO2 spheres, which were composed of primary nano-sized particles. The diameter of the alpha-Fe2O3 nanorods was about 10 nm, and the thickness of the SnO2 spherical shell was about 100 nm. In order to explore the formation mechanism of the composites, the structure features of the double-shell structural SnO2/alpha-Fe2O3 hollow composites at different reaction stages were investigated. The ethanol sensing properties of the pure SnO2 and SnO2/alpha-Fe2O3 composites were tested. It was found that such double-shell composites exhibited enhanced ethanol sensing properties compared with the single-component SnO2 hollow spheres. For example, at an ethanol concentration of 100 ppm, the response of the SnO2/alpha-Fe2O3 composites was about 16, which was about 2 times higher than that of the primary SnO2 nanostructures. The response time of the sensor to 10 ppm ethanol was about 1 s at the operating temperature of 250 degrees C.