(544am) The Influence of Size and Surface Structure of Co3O4-Supported Pd Nano-Particles on CO Oxidation Activity
After Euro 6 emission standards were introduced, the exhaust emissions have been required to meet the much lower emitted level. Especially for the toxic gas carbon monoxide (CO), catalytic oxidation efficiency needs to be significantly improved. Among various noble metals, Pd is well-known as an effective catalyst for CO oxidation. In addition, Co3O4 is expected to be a potential support because relatively weak Co-O bond leads to easily supply the reactive oxygen. In this study, we investigated Co3O4-supported Pd nanoparticles (NPs) as the catalyst candidate for CO oxidation. We synthesized various sizes of Pd NPs from 2 nm to 18 nm to search for the optimum Pd particle size for the excellent reaction activity. The Pd NPs of 4 ~7 nm showed the best catalytic activity of CO oxidation among the samples we examined. The different facets of exposed PdO were observed for different sized Pd NPs by STEM. It is therefore thought that the surface structure of Pd NP influences on the reaction activity. Our density functional theory results verified that the catalytic activity of CO oxidation is changed with the surface structure of Pd. This relationship we elucidated in this study will be useful to rationally design the efficient catalyst for CO oxidation.