Synthesis and characterization of spinel Co3O4 octahedra enclosed by the {111} facets

Abstract Spinel Co 3 O 4 octahedra synthesized by a facile redox-precipitation method were investigated for the complete oxidation of methane. XRD analysis showed that the spinel structural Co 3 O 4 octahedra had a relatively strong (1 1 1) diffraction peak as compared with that of the irregular shaped Co 3 O 4 nanoparticles prepared by a conventional precipitation method. The results of methane combustion test demonstrated that the Co 3 O 4 octahedra had no catalytic activity at 300–500 °C, while the Co 3 O 4 irregular nanoparticles were highly active at the same reaction conditions. HRTEM studies revealed that the Co 3 O 4 octahedra were predominantly exposed by the low Miller-index {1 1 1} facets with the lowest surface energy, and the Co 3 O 4 irregular nanoparticles were exposed by various crystal facets. The results exhibited that the {1 1 1} facets with the low surface energy of the Co 3 O 4 octahedra resulted in the inert catalytic activity in the methane oxidation reaction.