Cerium doped zirconium dioxide as a potential new photocatalyticmaterial. The role of the preparation method on the propertiesof the material

Small amounts of Ce4+ions dispersed in the bulk of ZrO2give to this material unexpected properties ofphotoactivity under visible light. Three different samples have been synthesized following different meth-ods and using different precursors and all show some degree of photoactivity. This has been monitoredvia EPR spectroscopy in terms of charge separation (electrons and holes formation) under polychromaticlight having > 420 nm. This behaviour, unimaginable for bare zirconia due to the large band gap of thisoxide (around 5 eV), is possible because of the presence in the solid of empty 4f Ce states located in themiddle of the band gap which act as intermediate levels in a double excitation mechanism. The dopedoxide here described can be considered an example of third generation photoactive material operatingunder visible light.