Synthesis of Co–Mn oxides with double-shelled nanocages for low-temperature toluene combustion

Abstract

In this paper, we report a template-engaged strategy for the synthesis of Co–Mn oxides with double-shell box-in-box hollow nanocage (BHNC) structures. The inner shell of the box is made of Co₃O₄, while the outer shell is made of Co–Mn oxides. The composition of the outer shell was tuned by changing the Mn/Co molar ratio. This facile method can be used to construct box-in-box hollow structures of other transition metal oxides such as those of Co–Ni, Co–Cu and Co–Fe. These Co–Mn oxides with BHNCs exhibit toluene conversions over 90% at 250 °C, which is much higher than those of Co₃O₄ nanocages (NCs) and the traditional Co₃O₄-CP synthesized by co-precipitation method at the same temperature. Moreover, the former is superior to the latter in terms of resistance towards H₂O and CO₂. The superior catalytic performance of Co₁Mn₁ BHNCs is attributed to the high mobility of lattice oxygen, low toluene desorption temperature and active Co³⁺ sites originated from the oxidation of Co²⁺ by Mn³⁺.