Tuning the surface oxygen concentration of {111} surrounded ceria nanocrystals for enhanced photocatalytic activities

Abstract

For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO₂ nanocrystals (NCs) via a facile, green hydrothermal method for the investigation of photocatalytic activities. X-ray diffraction and transmission electron microscopy were employed to examine the crystal phase and morphology of the as-prepared nanocrystals. Raman and X-ray photoelectron spectroscopy techniques were implemented to investigate the presence and variations in oxygen vacancy concentration in un-doped and indium doped CeO₂ nanocrystals. The photocatalytic activity results revealed that 10 at% doping is the optimal indium doping level to demonstrate superior dye removal efficiency (∼40%) over un-doped and doped CeO₂ NCs. Moreover, the 10% In-doped CeO₂ nanocrystals expressed excellent cycling stability and superior photocatalytic performance toward other dye pollutants. Finally, on the basis of our findings, a possible photocatalytic mechanism in which indium doping can generate more surface oxygen vacancies in the ceria lattice which delay the electron–hole recombination rates, thus increasing the lifetime of electron–hole separation for enhanced photocatalytic performances was proposed.