Solubility product difference-guided synthesis of Co3O4–CeO2 core–shell catalysts for CO oxidation

Abstract

It is still an important issue to develop a facile, environmentally friendly way to synthesize bimetal oxide materials. In this paper, Co₃O₄–CeO₂ core–shell catalysts were prepared by an interfacial reaction, where Co(CO₃)_0.35Cl_0.2(OH)_1.1 nanorods were dispersed in Ce³⁺ 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(CO₃)_0.35Cl_0.2(OH)_1.1 precursor combined with Ce³⁺ 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 H₂-temperature programmed reduction (H₂-TPR) analysis revealed that there is a synergistic effect between Co₃O₄ and CeO₂ in the as-prepared Co₃O₄–CeO₂ core–shell catalysts, which is responsible for their enhanced catalytic activity toward CO oxidation in comparison to pure Co₃O₄ and CeO₂.