A Noble-Metal-Free Ce_0.90Co_0.10O_{2 – δ} Catalyst with Enhanced Three-Way Catalytic Performance¹

Abstract—Co ion doped ceria, Ce_0.90Co_0.10O_{2 – δ}, and Pd ion doped ceria, Ce_0.98Pd_0.02O_{2 – δ}, were coated on honeycomb structured cordierite monolith by solution combustion method. The dip–dry–heat procedure was followed for the catalyst coating on the monolith. The color of the monolith confirmed the highly crystalline fluorite structure of the catalytic coating. X-ray diffraction and transmission electron microscopy studies confirmed the single phase of Co ion doped CeO₂, and the particle size of about 9 nm was determined by the particle-size distribution curve. Ce_0.90Co_0.10O_{2 – δ} showed little higher catalytic activities than Ce_0.98Pd_0.02O_{2 – δ} in CO oxidation, hydrocarbons oxidation, and NO reduction by CO. Three-way catalytic reactions over Ce_0.90Co_0.10O_{2 – δ} were competitively better than those over Ce_0.98Pd_0.02O_{2 – δ}. The X-ray photoelectron spectroscopy study confirmed that some of Co³⁺ ions are reduced to Co²⁺ ions after three-way catalytic reactions on Ce_0.90Co_0.10O_{2 – δ} catalyst due to the utilization of excess lattice oxygen for the oxidation reaction. Economically, Ce_0.90Co_0.10O_{2 – δ} catalyst is far preferable than Ce_0.98Pd_0.02O_{2 – δ} catalyst due to the high expense of noble metals compared to other transition metals.