Metal-Support Interactions in CeO₂- and SiO₂-Supported Cobalt Catalysts: Effect of Support Morphology, Reducibility,...

With the increasing demand for highly efficient and durable catalysts, researchers have been doing extensive research to engineer the shape, size, and even phase (e.g., hcp or fcc Co) of individual catalyst nanoparticles, as well as the interface structure between the catalyst and support. In this work, cobalt oxides were deposited on ceria with rod-like morphology (CeO₂NR) and cube-like morphology (CeO₂NC) and silica with sphere-like morphology (SiO₂NS) via a precipitation-deposition method to investigate the effects of support morphology, surface defects, support reducibility, and the metal-support interactions on redox and catalytic properties. XRD, Raman, XPS, BET, H₂-TPR, O₂-TPD, CO-TPD, TEM, and TPR/TPO cycling measurements have been mainly employed for catalysts characterization. Compared with CeO₂NC and SiO₂NS supports, as well as CeO₂NC- and SiO₂NS-supported cobalt catalysts, CeO₂NR counterparts exhibited enhanced reducibility and CO oxidation performance at a lower temperature. Both the apparent activation energy and CO conversion demonstrated the following catalytic activity order: 10 wt % CoO _x/CeO₂NR > 10 wt % CoO _x/CeO₂NC > 10 wt % CoO _x/SiO₂NS. These results showed a strong support-dependent reducibility, CO oxidation, and redox cycling activity/stability of the as-prepared catalysts. Moreover, the significantly enhanced catalytic CO oxidation of the 10 wt % CoO _x/CeO₂NR catalyst indicated the vital role of CeO₂NR support with rich surface oxygen vacancies, superior oxygen storage capacity and mobility, and excellent adsorption/desorption behavior of CO and O₂ species.