One-step in situ synthesis of CeO₂nanoparticles grown on reduced graphene oxide as an excellent fluorescent and photocatalyst material under sunlight irradiation

Abstract

CeO2 nanoparticles (NPs) with average particle size of ∼17 nm were grown on graphene sheets by simply mixing cerium chloride as the Ce precursor with graphene oxide (GO) in distilled water and the simultaneous reduction of GO to reduced graphene oxide (rGO), followed by a one-step hydrothermal treatment at 150 °C. A unique blue to green tuneable luminescence was observed as a function of the excitation wavelength. With this method, significant applications of rGO-CeO2 nanocomposites in many optical devices could be realized. The photocatalytic activity of the as-synthesized CeO2 and rGO-CeO2 nanocomposite was investigated by monitoring the degradation of methylene blue (MB) dye under direct sunlight irradiation. The rGO-CeO2 nanocomposite exhibited excellent photocatalytic activity compared to CeO2 NPs by degrading 90% of the MB dye in 10 min irradiation under sunlight. This property of rGO-CeO2 nanocomposites was ascribed to the significant suppression of the recombination rate of photo-generated electron-hole pairs due to charge transfer between rGO sheets and CeO2 NPs and the smaller optical band-gap in the rGO-CeO2 nanocomposite.

Ce3+-ion, Surface Oxygen Vacancy, and Visible Light-induced Photocatalytic Dye Degradation and Photocapacitive Performance of CeO2-Graphene Nanostructures

“…When the CR and MB dye solution comprising the CeO 2 -Graphene nanostructure is exposed to visible light, electron–hole pairs are generated because of the ejection of an electron from the VB, which makes a hole in the VB. For the duration of the photoexcitation process, some of the ejected electrons transfer to the CB and some electrons are trapped by the localized defect (defects and oxygen vacancies as confirmed by the XPS and EPR results) levels lying below the Ce 4f band 36, 46, 64 . The photogenerated CB electrons are transferred rapidly to the conducting graphene sheets and react with the oxygen dissolved in the dye solution making superoxide radicals (O 2 · ).…”

“…A speedy transfer of the photogenerated electrons from the excited CeO 2 NPs is the result. Therefore, due to the transfer of electrons from CeO 2 NPs to the graphene sheets, the recombination rate of photo-generated electron–hole pairs in CeO 2 NPs is suppressed 46, 64 (Fig. 11).…”

The Template‐Free Synthesis of CuO@CeO2 Nanospheres: Facile Strategy, Structure Optimization, and Enhanced Catalytic Activity toward CO Oxidation

“…Ceria (CeO 2 ) plays an important role as a catalyst that supports a variety of catalytic reactions, due to its excellent redox properties and high oxygen‐storage capacity . The properties of ceria, in turn, are associated with the arrangement of the terminated surface oxygen atoms, which greatly depends on the morphology, structure, and components.…”

An Electrocatalyst for a Hydrogen Evolution Reaction in an Alkaline Medium: Three‐Dimensional Graphene Supported CeO2 Hollow Microspheres

“…In comparison to CeO 2 hollow microspheres, 3D‐rGO‐CeO 2 , and CeO 2 /rGO show similar Ce 4+ 3d 5/2 peaks, but the Ce 4+ 3d 3/2 peak at 907.2 eV shifts to 907.7 eV for 3D‐rGO‐CeO 2 and CeO 2 /rGO, suggesting the existence of electron interactions between CeO 2 and rGO in the composites. Besides, a new peak corresponding to Ce 3+ 3d 3/2 appears at 904.0 and 903.0 eV for 3D‐rGO‐CeO 2 and CeO 2 /rGO, respectively,, indicating the increasing content of Ce 3+ ions in the composites, which would result in more oxygen vacancies . High oxygen vacancies in the composites suggest the charge transfer between rGO and CeO 2 …”