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

Abstract

Double-shell SnO₂/α-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 α-Fe₂O₃ nanorods grew epitaxially on the surface of hollow SnO₂ spheres, which were composed of primary nano-sized particles. The diameter of the α-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/α-Fe₂O₃ hollow composites at different reaction stages were investigated. The ethanol sensing properties of the pure SnO₂ and SnO₂/α-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/α-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 °C.