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

Highlights: • Ag/α-Fe₂O₃ hierarchical microspheres were prepared. • Ag/α-Fe₂O₃ microspheres showed 1.7 times higher response for ethanol than α-Fe₂O₃. • The enhanced performance was attributed to the heterojunctions and catalytic effect. 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.