Synthesis of core–shell α-Fe2O3@NiO nanofibers with hollow structures and their enhanced HCHO sensing properties

Abstract

Different components and well-defined structures may cooperatively improve the performances of composite materials and enhance their applicability. In this paper, core–shell α-Fe₂O₃@NiO nanofibers (α-Fe₂O₃@NiO CSNFs) with hollow nanostructures are synthesized by a facile coaxial electrospinning method and calcination procedure. Considering the temperature-dependent solute degradation process and different influencing factors including the solvent evaporation rate and phase separation, a multistage formation mechanism has been proposed to understand the formation of the CSNF structure. The gas sensing tests indicate that the α-Fe₂O₃@NiO CSNFs exhibit significantly improved gas sensitivity and selectivity performances in comparison with NiO hollow nanofibers (NiO HNFs) and α-Fe₂O₃ nanofibers (α-Fe₂O₃ NFs). The response of α-Fe₂O₃@NiO CSNFs to 50 ppm HCHO at 240 °C is ∼12.8, which is 10- and 7.1-times higher than those of pure NiO and α-Fe₂O₃, respectively. The synergy between the heterojunction, core–shell hollow nanofiber structure and Fe loading into the NiO shell contribute to the enhanced response of α-Fe₂O₃@NiO CSNFs. Moreover, extremely fast response–recovery behavior (∼2 s and ∼9 s) has been observed at the optimal working temperature of 240 °C. The detection limit for HCHO could be lower than 1 ppm. These favorable gas sensing performances make the α-Fe₂O₃@NiO CSNFs promising materials for gas sensors.