Ce-ion, Surface Oxygen Vacancy, and Visible Light-induced Photocatalytic Dye Degradation and Photocapacitive Performance of CeO-Graphene Nanostructures.

Cerium oxide nanoparticles (CeO NPs) were fabricated and grown on graphene sheets using a facile, low cost hydrothermal approach and subsequently characterized using different standard characterization techniques. X-ray photoelectron spectroscopy and electron paramagnetic resonance revealed the changes in surface states, composition, changes in Ce to Ce ratio, and other defects. Transmission electron microscopy (TEM) and high resolution TEM revealed that the fabricated CeO NPs to be spherical with particle size of ~10-12 nm. Combination of defects in CeO NPs with optimal amount of two-dimensional graphene sheets had a significant effect on the properties of the resulting hybrid CeO-Graphene nanostructures, such as improved optical, photocatalytic, and photocapacitive performance. The excellent photocatalytic degradation performances were examined by monitoring their ability to degrade Congo red ~94.5% and methylene blue dye ~98% under visible light irradiation. The photoelectrode performance had a maximum photocapacitance of 177.54 Fg and exhibited regular capacitive behavior. Therefore, the Ce-ion, surface-oxygen-vacancies, and defects-induced behavior can be attributed to the suppression of the recombination of photo-generated electron-hole pairs due to the rapid charge transfer between the CeO NPs and graphene sheets. These findings will have a profound effect on the use of CeO-Graphene nanostructures for future energy and environment-related applications.