Catalytically active Co₃O₄ hybrid microstructures and their morphology evolution induced by ceria

Mixed metal oxides with hybrid structures often show synergistic effects and thus much better catalytic properties than their single components. We present here the synthesis of Ce/Co mixed oxalates via a facile co-precipitation method, and the following calcination process resulted in the final CeO₂/Co₃O₄ hybrid microstructures. Then the systematical characterizations were conducted to study their structure evolution and composition-dependent properties on catalytic CO oxidation. The results show that the hybrids of CeO₂/Co₃O₄ were composed of 5 nm sized CeO₂ and 20 nm sized Co₃O₄. While increasing the feeding amount of Ce, the morphologies of the as-obtained CeO₂/Co₃O₄ hybrids changed from the flower-like microstructures to the hot dog-like ones, and finally to the sheet-like ones. After catalytic tests, it was found that the CeO₂/Co₃O₄ hybrids show different catalytic activities by varying the molar ratios of Ce/Co (pure Co for Co-oxalate, Ce/Co = 1/19 for Ce₁/Co₁₉-oxalate, Ce/Co = 1/9 for Ce₁/Co₉-oxalate, Ce/Co = 3/7 for Ce₃/Co₇-oxalate, Ce/Co = 5/5 for Ce₅/Co₅-oxalate, pure Ce for Ce-oxalate). Among these samples, Ce/Co = 1:19, which has a higer pore volume performed the optimal catalytic property compared to the others.