Synthesis of highly efficient Co₃O₄ catalysts by heat treatment ZIF-67 for CO oxidation

The present work reported the porous rhombic dodecahedral Co₃O₄ catalysts undergoing ZIF-67 calcination in air condition at different temperatures. The structural and textural properties of the obtained catalysts were fully characterized using scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption–desorption, and X-ray photoelectron spectroscopic (XPS). H₂-temperature-programmed reduction (H₂-TPR) was used to test their redox properties. Both surface structure and morphology of Co₃O₄ catalysts exhibited good correlation with their catalytic activity. The results demonstrated that the catalyst calcined at 500 °C (Co₃O₄-500) exhibited the best performance with respect to the complete CO conversion temperature at 115 °C. This finding was reproducible and tentatively attributed to the unique structure, higher amount of surface Co²⁺ and adsorbed oxygen species, and good low-temperature reduction behavior. Finally, the effect of water vapor on catalytic activity was also determined, which indicated that the addition of water vapor to the feedstock had a negative effect on CO conversion over Co₃O₄-500.