Fabrication of CeO2–MOx (M = Cu, Co, Ni) composite yolk–shell nanospheres with enhanced catalytic properties for CO oxidation

CeO2-MO x (M = Cu, Co, Ni) composite yolk-shell nanospheres with uniform size were fabricated by a general wet-chemical approach. It involved a non-equilibrium heat-treatment of Ce coordination polymer colloidal spheres (Ce-CPCSs) with a proper heating rate to produce CeO2 yolk-shell nanospheres, followed by a solvothermal treatment of as-synthesized CeO2 with M(CH3COO)2 in ethanol solution. During the solvothermal process, highly dispersed MO x species were decorated on the surface of CeO2 yolk-shell nanospheres to form CeO2-MO x composites. As a CO oxidation catalyst, the CeO2-MO x composite yolk-shell nanospheres showed strikingly higher catalytic activity than naked CeO2 due to the strong synergistic interaction at the interface sites between MO x and CeO2. Cycling tests demonstrate the good cycle stability of these yolk-shell nanospheres. The initial concentration of M(CH3COO)2·xH2O in the synthesis process played a significant role in catalytic performance for CO oxidation. Impressively, complete CO conversion as reached at a relatively low temperature of 145 °C over the CeO2-CuO x -2 sample. Furthermore, the CeO2-CuO x catalyst is more active than the CeO2-CoO x and CeO2-NiO catalysts, indicating that the catalytic activity is correlates with the metal oxide. Additionally, this versatile synthesis approach can be expected to create other ceria-based composite oxide systems with various structures for a broad range of technical applications.