Microstructural characterization of nanocrystalline gold particles supported on CoCr2O4

This work presents results of high-resolution transmission electron microscope investigations of microstructure evolution of Au/CoCr(2)O(4) catalyst subjected to various chemical treatments (reduction in hydrogen, reaction of propane oxidation and reaction of CO oxidation). Crystallites of CoCr(2)O(4) support have octahedral or truncated octahedral shape and exhibit well-developed faces, mostly (111). No change in the support morphology was noticed in catalyst samples after various chemical treatments. Small (approximately 8 nm) nanocrystals of gold supported on crystalline CoCr(2)O(4) were observed for the fresh sample. The nanoparticles grow at the surface of CoCr(2)O(4) as thin, disk-like crystallites, in the preferred (111)Au parallel(111)CoCr(2)O(4) epitaxial orientation. Further treatment in hydrogen and in reaction conditions (CO and propane oxidation) did not change noticeably the size of Au particles, but modified slightly their shape. A main reason why Au particles retain small size despite heat treatment is their epitaxial contact with the CoCr(2)O(4) support established during the catalyst preparation.