Surface exsolution and local atomic structure of amorphous CeTiOx

Abstract

We made precipitated nano-ceria (∼5 nm) on the surface of the catalyst by heat treatment of Ce-supersaturated amorphous CeTiOx to improve the oxygen storage properties of CeO2. The catalysts were prepared by sol-gel methods and TiO2 nanoparticles were preferentially generated as a core material to form selective Ce-supersaturated structure on the catalyst surface. Reaction temperature and amount of doping element are optimized to induce selective crystallization of CeO2. CeCe (2nd shell) bond around 0.38 nm of Ce L3-edge extended X-ray absorption fine structure is reduced and nanostructure of precipitated ceria on the surface is observed by HREM. The catalyst is present as amorphous with precipitated nano-CeO2 on the surface. The de-NOx efficiency of the catalyst, which has precipitated CeO2, improves by ∼50% owing to the simultaneous reactions of the nano CeO2 and the amorphous CeTiOx.