Preparation of hollow porous Co-doped SnO2 microcubes and their enhanced gas sensing property

Abstract

Hollow porous Co-doped SnO₂ microcubes were achieved by a template-free chemical solution route combined with subsequent alkali-washing, calcination and acid-washing process. Spontaneous phase segregation yields such a special hollow porous structure. Several techniques, such as X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric-differential thermal analysis, and Brunauer–Emmett–Teller N₂ adsorption–desorption analyses, were used to characterize the structure and morphology of the products. During the process, alkali-washing in the first step is critical to the formation of the hollow structure. The process of inducing porosity starts with a crystalline single-phase hydroxide precursor CoSn(OH)₆ formed by co-precipitation of the metal ions from aqueous solution. Thermal decomposition of the precursors leads to an intimate mixture of Co₃O₄ and porous tetragonal SnO₂. The hollow porous Co-doped SnO₂ microcubes are obtained after the Co₃O₄ phase has been removed by acid-washing. A decomposition–aggregation–dissolution process is proposed to demonstrate the formation of such a special structure. Furthermore, the gas sensing properties of the as-prepared hollow, porous, Co-doped SnO₂ microcubes for some volatile organic vapors were tested, which exhibited a much better sensing performance than that of the porous Co-doped SnO₂ microcubes, indicating that the special hollow porous Co-doped SnO₂ structures are highly promising for applications as gas sensors.