Shifting the band gap from UV to visible region in cerium oxide nanoparticles.

• Band gap engineering of CeO 2-x nanoparticles shifts absorption from UV to visible. • CeO 2-x nanoparticles of high surface area and surface O vacancy population used for H 2 production. • Improving the activity of CeO 2-x nanoparticles for the photocatalytic H 2 production. High surface area cerium oxide (CeO 2-x) nanoparticles (S = 170 m2/g) were synthesized by the precipitation method with a narrow band gap (2.73 ± 0.03 eV). In comparison to typical band gap values for cerium oxide, it presents a red shift in the light absorption spectrum from UV to visible region. X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Absorption Spectroscopy (XAS), X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS) measurements were conducted aiming to elucidate this promising property for photocatalytic applications of the nanoparticles synthesized. It was obtained that the high structural disorder and O vacancy population of the nanoparticles synthesized are responsible for the narrow band gap found. Furthermore, the CeO 2-x nanoparticles were applied to the photocatalytic H 2 production reaction and presented activity 10 times higher than the commercial CeO 2-x standard, besides a much better performance than typical results found for CeO 2-x in the literature. [ABSTRACT FROM AUTHOR]