Fe₂O₃ Nanotube-Decorated ZnFe₂O₄ Open Nanocages for High-Sensitive H₂S Detection

The rational integration of nanomaterials with different functions is a new solution to improve the gas-sensing performance of metal oxide gas sensors. In this paper, Fe₂O₃ nanotube-decorated ZnFe₂O₄ open nanocages and nanoboxes with a hierarchical complex superstructure are prepared by an autotemplate epitaxial growth strategy combined with an annealing process. The gas sensitivity test result shows that the Fe₂O₃ nanotube-decorated ZnFe₂O₄ open nanocage exhibited good gas selectivity for H₂S at a relatively low operating temperature (140 °C) with fast response/recovery time (12/96 s) and a detection limit as low as 39 ppb. The superior gas-sensing performance of Fe₂O₃ nanotube-decorated ZnFe₂O₄ open nanocages is attributed not only to the combination of open cavities and porous shell structures but also to the highly active tubular Fe₂O₃ subunits with ultrathin wall thickness to promote the adsorption of gas molecules and the migration of carriers. Quasi <i>in situ</i> X-ray photoelectron spectroscopy and <i>in situ</i> infrared characterization reveal that H₂S is physically adsorbed in an unstable state on the surface of the Fe₂O₃-nanotube-decorated ZnFe₂O₄ open nanocages during the gas-sensing response. This unstable adsorption facilitates faster desorption, thereby significantly reducing the sensor's response/recovery times. This work not only provides a novel strategy for designing high-performance H₂S gas-sensing materials but also proposes a promising approach for engineering complex nanostructures with enhanced functionalities.