Surface and Inner Defects in Au/CeO2 WGS Catalysts: Relation between Raman Properties, Reactivity and Morphology

Defects (O vacancies) with different Raman properties (A–C, see graphic) and reactivity are present on Au/CeO2. A is Raman inactive, located in external layers, able to form O22− species with O2; B, formed by a Au-catalysed reduction in H2, is Raman active, located in non-stoichiometric surface layer, and reacts with O2 without forming O22− species; C is Raman active, located in inner positions, and gives negligible reactivity upon O2. Only A and B defects react with H2O.