Low-temperature catalysts of mesoporous Co 3 O 4 and Au/Co 3 O 4 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 Co 3 O 4 , whereas the Co 3 O 4 nanosheets prepared by the precipitation method exhibited the most exposed {112} facets. We found that the mesoporous Co 3 O 4 was significantly more active for ethylene oxidation than the Co 3 O 4 nanosheets. The results indicated that the crystal facet {110} of Co 3 O 4 played an essential role in determining its catalytic oxidation performance. The synthesized Au/Co 3 O 4 materials, in which the gold nanoparticles were assembled into the pore walls of the Co 3 O 4 mesoporous support, exhibited stable, highly dispersed, and exposed gold sites. Gold nanoparticles present on Co 3 O 4 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.

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