Synthesis of novel CoOx decorated CeO2 hollow structures with an enhanced photocatalytic water oxidation performance under visible light irradiation

Abstract

Cobalt oxide decorated octahedral ceria hollow structures (CoO_x/CeO₂) with various contents of CoO_x 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_x/CeO₂ nanocage composites. The photocatalytic results indicate that the CoO_x/CeO₂ nanocage composite with 1 mol% CoO_x shows the highest photocatalytic activity. The excellent photocatalytic activity can be attributed to the improved visible-light absorption of CoO_x/CeO₂ composites and the efficient separation of excited electron–hole pairs between CoO_x and CeO₂, which can effectively enhance the lifetime of charge carriers in the CoO_x-modified samples and then improve the oxygen evolution activity. Cobalt oxide is expected to be an excellent water oxidation co-catalyst for semiconductor photocatalysts.