Solubility product difference-guided synthesis of CoO-CeO core-shell catalysts for CO oxidation

It is still an important issue to develop a facile, environmentally friendly way to synthesize bimetal oxide materials. In this paper, Co 3 O 4 -CeO 2 core-shell catalysts were prepared by an interfacial reaction, where Co(CO 3 ) 0.35 Cl 0.2 (OH) 1.1 nanorods were dispersed in Ce 3+ aqueous solution for 2 days, followed by a calcination step. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Based on the characterization and comparative experimental results, we proposed that the OH − ions slowly dissociated from the Co(CO 3 ) 0.35 Cl 0.2 (OH) 1.1 precursor combined with Ce 3+ to develop into Ce(OH) 3 nanoparticles because of its smaller solubility product constant than that of the Co precursor or Co(OH) 2 . Neither an additional precipitation agent nor stabilizing molecules were employed during the whole preparation. Raman spectroscopy and H 2 -temperature programmed reduction (H 2 -TPR) analysis revealed that there is a synergistic effect between Co 3 O 4 and CeO 2 in the as-prepared Co 3 O 4 -CeO 2 core-shell catalysts, which is responsible for their enhanced catalytic activity toward CO oxidation in comparison to pure Co 3 O 4 and CeO 2 . Co 3 O 4 -CeO 2 core-shell catalysts are successfully fabricated by an ion exchange procedure between Co(CO 3 ) 0.35 Cl 0.2 (OH) 1.1 nanorods and Ce 3+ aqueous solution, followed by a calcination step.