A comparative study of partial reduction of ceria via laser ablation in air and soft chemical route

Experimental results are presented on the reduction of CeO2 (bandgap of 3.1 eV) either via irradiation in air with UV excimer lasers (KrF, XeCl) or via treatment with hydrazine at 100°C. Both kinds of treatment result in similar modifications of the diffuse reflectance spectra (DRS) of samples: the appearance of an absorption band in the visible which is assigned to oxygen vacancies and to charge transfer transitions between Ce3+ and Ce4+ ions. The influence of laser fluence on the DRS of ceria has been studied below and above the ablation threshold of ∼1 J/cm2. Electron spin resonance (ESR) spectra of ceria samples obtained from both kinds of treatment confirm the presence of paramagnetic species. The reduced ceria promotes the electroless deposition of Pd from a plating solution containing hydrazine. This finding has been applied to the selective metallization of composite oxides, that is to the selective deposition of Pd on ceria particle size of 2–8 nm supported on insulating carriers, such as alumina or silica.