Formation of NiCo2O4 hierarchical tubular nanostructures for enhanced xylene sensing properties

Abstract

Complex hollow structures with ultra-thin 2D building blocks represent a unique type of functional nanostructures because of their structural merits. In this work, hierarchical NiCo2O4 hollow microtubules assembled by ultra-thin 2D nanosheets have been successfully prepared via a template-assisted process with subsequent etching treatment. The purity, morphology, crystallographic information and surface chemical composition of as-obtained hierarchical NiCo2O4 hollow microtubules are characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM),transmission electron microscopy (TEM), element mapping, X-ray photoelectron spectroscopy (XPS) and Nitrogen adsorption–desorption analysis. Gas sensing performance of hierarchical NiCo2O4 hollow microtubules is discussed in detail. The results show that hierarchical NiCo2O4 hollow microtubules not only exhibit rapid response/recovery (20/9 s) speed to 100 ppm xylene at relatively low working temperature of 220 °C, but also show low detection limit (1 ppm), high response, excellent gas selectivity and superior long-term stability, which are significantly better than irregular NiCo2O4 nanosheets. The results demonstrate that unique hierarchical NiCo2O4 hollow microtubules are promising candidates for efficient and reliable detection of xylene.