Solvothermal synthesis of Co3O4/Al2O3 hollow core–shell microspheres for the catalytic oxidation of CO

Abstract

A facile template-free solvothermal strategy has been developed for the synthesis of uniform and hollow core–shell Co₃O₄/Al₂O₃ microspheres composed of numerous tiny nanorods. The morphology, structure, and composition of the spheres have been investigated using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, H₂-temperature programmed reduction (H₂-TPR) and X-ray diffraction analysis (XRD). The specific surface area and pore-size distribution of the obtained products as determined by gas sorption measurements show that the core–shell microspheres exhibit a high surface area and porosity. The formation of the hollow structure involves a trisodium citrate (TSC)-assisted Ostwald ripening process. The structure and factors that govern the shape evolution of the core–shell Co₃O₄/Al₂O₃ microspheres have been carefully studied, such as the Co wt% content, the TSC/Al ratio and the temperature. The catalytic activity of the as-prepared core–shell Co₃O₄/Al₂O₃ microspheres has been evaluated for CO catalytic oxidation. Their high performance may be attributed to their large specific surface area, high porosity and mesoporous structure.