A Noble-Metal-Free Ce0.90Co0.10O2-δ Catalyst with Enhanced Three-Way Catalytic Performance

Co ion doped ceria, Ce0.90Co0.10O2-delta, and Pd ion doped ceria, Ce0.98Pd0.02O2-delta, 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. Ce0.90Co0.10O2-delta showed little higher catalytic activities than Ce0.98Pd0.02O2-delta in CO oxidation, hydrocarbons oxidation, and NO reduction by CO. Three-way catalytic reactions over Ce0.90Co0.10O2-delta were competitively better than those over Ce0.98Pd0.02O2-delta. The X-ray photoelectron spectroscopy study confirmed that some of Co ions are reduced to Co2+ ions after three-way catalytic reactions on Ce0.90Co0.10O2-delta catalyst due to the utilization of excess lattice oxygen for the oxidation reaction. Economically, Ce0.90Co0.10O2-delta catalyst is far preferable than Ce0.98Pd0.02O2-delta catalyst due to the high expense of noble metals compared to other transition metals.