Synthesis of novel CoO decorated CeO hollow structures with an enhanced photocatalytic water oxidation performance under visible light irradiation.

Cobalt oxide decorated octahedral ceria hollow structures (CoO/CeO) with various contents of CoO nanoparticles were prepared via a simple chemical impregnation method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse-reflectance spectroscopy (DRS), surface photovoltage spectroscopy (SPV) and transient photovoltage spectroscopy (TPV). The photocatalytic oxygen evolution via water oxidation was investigated for the as-prepared CoO/CeO nanocage composites. The photocatalytic results indicate that the CoO/CeO nanocage composite with 1 mol% CoO shows the highest photocatalytic activity. The excellent photocatalytic activity can be attributed to the improved visible-light absorption of CoO/CeO composites and the efficient separation of excited electron-hole pairs between CoO and CeO, which can effectively enhance the lifetime of charge carriers in the CoO-modified samples and then improve the oxygen evolution activity. Cobalt oxide is expected to be an excellent water oxidation co-catalyst for semiconductor photocatalysts.