Pd/FeOx catalysts were prepared by co-precipitation and characterized before and after reduction using X-ray powder diffraction, thermal analysis, CO chemisorption, electron microscopy, and X-ray photoelectron spectroscopy. Results give evidence for the encapsulation of palladium particles by iron oxide after reduction at high temperatures (523 K). Oxidation of carbon monoxide was applied as test reaction to characterize catalyst samples in different states. Strong metal-support interactions significantly enhance catalytic activity for oxidation of carbon monoxide. However, this state is not stable under the applied reaction conditions. Catalyst deactivation occurs in two ways: (1) via changes in the oxidation state of iron species and (2) due to sintering of palladium particles. (C) 2014 Elsevier Inc. All rights reserved.