(207h) Improvement of Low Temperature Activity for CO Oxidation on Ceria Catalyst By Transition Metal Substitution

Recently, reduction of exhaust gas has been an important issue with increasing the sales of automobiles. CO reduction in various exhaust gases is particularly critical because it damages people and environment. A ceria-based catalyst that can reduce automotive emissions instead of three-way catalysts have been developed. When the temperature is lowered, however, the efficiency is rapidly decreased. In order to improve the activity of ceria catalyst, we synthesized transition metal (TM)-doped ceria. In this study, we examined four transition metal (TM=Cu, Co, Mn, and Fe) doped and their co-doped ceria. TM-doped ceria (Ce_0.95TM_0.05O_2-δ) were synthesized by EDTA-citrate complexing method. By means of this method, we obtained highly pure and homogeneous nano-powder. The nanoparticles were then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (SEM-EDS). To clarify the positive effects of doping, the surface area was evaluated by Brunauer-Emmett-Teller (BET) measurement. It turns out that the TM-doped ceria powders had higher specific surface area than that of undoped ceria, and correspondingly, the larger specific surface area enhanced the catalytic activity. Our density functional theory results demonstrated that this is attributed to the different interactions between dopant and support. Our results will be helpful for effectively exploring the TM dopant candidates of ceria and determining their optimal concentration for the enhanced catalytic activity.