Hollow NiFe2O4 microspindles derived from Ni/Fe bimetallic MOFs for highly sensitive acetone sensing at low operating temperatures

Abstract

Hollow semiconductor oxide micro-/nanomaterials can provide significant advantages for gas sensing by facilitating the diffusion of target gases and the surface reaction. In this study, we report the synthesis of hollow NiFe₂O₄ microspindles through an as-developed metal–organic framework (MOF) route, which involves two steps: the preparation of Ni/Fe bimetallic MOF solid microspindle precursors and their subsequent transformation to the final materials via an annealing treatment in the air. The hollow NiFe₂O₄ microspindles were demonstrated to be composed of primary nano-building particles and abundant deep pores in the hollowed-out shells. Furthermore, in synergy with the large specific surface area, hollow interior, and abundant surface oxygen species, as expected, the gas sensor based on the hollow NiFe₂O₄ microspindles delivered a high sensitivity of 52.8 towards 200 ppm acetone vapor as well as good selectivity and cyclic stability at a low working temperature (120 °C). Finally, the sensing mechanism for the gas sensing behavior was also proposed. The high-performance sensing behavior towards acetone suggests that the as-fabricated sensor can be a promising candidate for environmental monitoring; thus, this study paves the way towards the efficient fabrication of advanced gas sensors on the basis of metal oxides derived from appropriate MOF precursors in the future.