Surface-Related Factors Affecting the Photocatalytic Process of Semiconductor Oxides: Ceria and Titania

Abstract

Nanoparticles of CeO 2 , with rod-, and cubic-morphology, were synthesized by hydrothermal method and compared with commercial polyhedral ceria particles. Comparison of the synthesized CeO 2 with the commercial powder revealed the influence of its defectivity with the absorption edge energy. The defectivity of CeO 2 has also been determined in correlation with the photocatalytic performance of CeO 2 per unit particles area, under narrow band UV-light (LED) condition. Analysis of the photocatalytic performance of the synthesized and commercial CeO 2 , as well as the reference TiO 2 powder, revealed an enhancement in the decolorization of methylene blue dye (MB) with pH. The improvement in photocatalysis was associated with the surface charge condition of CeO 2 particles, which controls the adsorption of molecules during the process. Furthermore, it was observed that the highly negative surface charge of cubic-morphology CeO 2 favored the decolorization of MB, despite the low BET surface area. The photoelectrochemical study of ceria electrodes revealed a low photopotential compared to that of TiO 2 , the impact of which leads to a worse photocatalytic performance of CeO 2 compared to TiO 2 .