Synthesis and characterization of Ag/α-Fe2O3 microspheres and their application to highly sensitive and selective detection of ethanol

Hierarchical oxide nanostructures had proved their promising features in gas sensing due to their high surface areas and well-aligned nanoporous structures containing less agglomerated configurations. In this study, a facile method was developed to prepare Ag/α-Fe2O3 microspheres using α-FeOOH microspheres as precursor and AgNO3 as Ag resource. Various characterization techniques were employed to identify the structures and morphologies of the hybrid nanostructures. The results revealed that Ag nanoparticles with diameters of 5 nm formed on the surface of hollow α-Fe2O3 spheres were composed of primary nano-sized particles. The ethanol sensing properties of pure α-Fe2O3 and Ag/α-Fe2O3 microspheres were evaluated and Ag/α-Fe2O3 microspheres showed higher responses towards ethanol when compared to other gases, such as toluene, ammonia, acetone, and formaldehyde. The response of Ag/α-Fe2O3 microspheres to 50 ppm ethanol was estimated to ∼11.2, which was 1.7 folds higher than that of pure α-Fe2O3 at 240 °C. Furthermore, the sensor could easily be recovered to its initial state in short periods after exposure to fresh air. The addition of Ag served as an active catalyst, creating more active sites believed crucial for enhancing sensitivity.