In this article, we review a series of studies that use synchrotron-based techniques (high-resolution photoemission, time-resolved Xray diffraction (XRD), and X-ray absorption near-edge spectroscopy) to investigate the physical and chemical properties of Ce 1-x Zr x O 2 nanoparticles and Ce 1-x Zr x O 2 (1 1 1) surfaces (x ≤ 0.5). CeO 2 and Ce 1-x Zr x O 2 particles in sizes between 4 and 7 nm were synthesized using a novel microemulsion method. The results of XANES (O K-edge, Ce and Zr L III -edges) indicate that the Ce 1-x Zr x O 2 nanoparticles and Ce 1-x Zr x O 2 (1 1 1) surfaces have very similar electronic properties. For these systems, the lattice constant decreased with increasing Zr content, varying from 5.4 Å in CeO 2 to 5.3 Å in Ce 0.5 Zr 0.5 O 2 . Within the fluorite structure, the Zr atoms exhibited structural perturbations that led to different types of Zr-O distances and non-equivalent O atoms in the Ce 1-x Zr x O 2 compounds. The Ce 1-x Zr x O 2 nanoparticles were more reactive towards H 2 and SO 2 than the Ce 1-x Zr x O 2 (1 1 1) surfaces. The Ce 1-x Zr x O 2 (1 1 1) surfaces did not reduce in hydrogen at 300 • C. At temperatures above 250 • C, the Ce 1-x Zr x O 2 nanoparticles reacted with H 2 and water evolved into gas phase. XANES showed the generation of Ce 3+ cations without reduction of Zr 4+ . There was an expansion in the unit cell of the reduced nanoparticles probably as a consequence of a partial Ce 4+ → Ce 3+ transformation and the sorption of hydrogen into the bulk of the material. S K-edge XANES spectra pointed to SO 4 as the main product of the adsorption of SO 2 on the Ce 1-x Zr x O 2 nanoparticles and Ce 1-x Zr x O 2 (1 1 1) surfaces. Full dissociation of SO 2 was seen on the nanoparticles but not on the Ce 1-x Zr x O 2 (1 1 1) surfaces. The metal cations at corner and edge sites of the Ce 1-x Zr x O 2 nanoparticles probably play a very important role in interactions with the H 2 and SO 2 molecules.