XPS study of cobalt-ceria catalysts for ammonia synthesis – The reduction process

The activation process of a cobalt catalyst promoted with cerium compounds was examined. The reduction of precursor was performed in a High Pressure Cell (HPC), being a part of an ultra-high vacuum (UHV) system, at 500 °C under hydrogen atmosphere. X-ray photoelectron spectroscopy (XPS) was subsequently used to investigate the evolution of surface composition. High resolution X-ray photoelectron analysis confirms total reduction of cobalt oxide into Co metallic form. After exposure to hydrogen, Ce4+ ions prevail in the structure of cerium oxides identified on the surface.