Mesoporous Co₃O₄ and Au/Co₃O₄ Catalysts for Low-Temperature Oxidation of Trace Ethylene

Abstract

Low-temperature catalysts of mesoporous Co₃O₄ and Au/Co₃O₄ with high catalytic activities for the trace ethylene oxidation at 0 °C are reported in this paper. The catalysts were prepared by using the nanocasting method, and the mesostructure was replicated from three-dimensional (3D) cubic KIT-6 silicas. High resolution transmission electron microscopy (HRTEM) studies revealed that {110} facets were the exposed active surfaces in the mesoporous Co₃O₄, whereas the Co₃O₄ nanosheets prepared by the precipitation method exhibited the most exposed {112} facets. We found that the mesoporous Co₃O₄ was significantly more active for ethylene oxidation than the Co₃O₄ nanosheets. The results indicated that the crystal facet {110} of Co₃O₄ played an essential role in determining its catalytic oxidation performance. The synthesized Au/Co₃O₄ materials, in which the gold nanoparticles were assembled into the pore walls of the Co₃O₄ mesoporous support, exhibited stable, highly dispersed, and exposed gold sites. Gold nanoparticles present on Co₃O₄ readily produced surface-active oxygen species and promoted ethylene oxidation to achieve a 76% conversion at 0 °C, which is the highest conversion reported yet.