Solvent-Free Chemical Approach to Synthesize Various Morphological Co₃O₄ for CO Oxidation

Co₃O₄ nanomaterials with diverse morphologies were usually synthesized in liquid phase accompanied by the template or surfactant under harsh conditions, which further restricted their practical application. Herein, we reported an extremely simple and practical solid-state chemical method to synthesize Co₃O₄-octahedrons, -plates, and -rods. Among these, the shape control of Co₃O₄-octahedrons and Co₃O₄-plates involve variation of the amount of reactant, and the formation of Co₃O₄-rods with {110} facet can be achieved by replacing the reactant. The formation of the Co₃O₄ nanomaterials with different morphologies originated from the different microenvironments of reaction and the structure of reactants. The catalytic activity of Co₃O₄ samples for CO oxidation was evaluated in normal feed gas. The as-prepared Co₃O₄-rods exposed {110} facet exhibited superior catalytic activity for CO oxidation, which can be attributed to more oxygen defects on Co₃O₄-rods surface. Additionally, Co₃O₄-rods exhibited excellent durablility (without pretreatment) in normal feed gas, even in the presence of moisture, comparable or better than that reported in the literature. The practical and environmental friendly solvent-free strategy provided a new promising route for large-scale preparation of (metal) oxide with remarkable CO oxidation performance for practical application.