Understanding Photocatalytic Metallization of Preadsorbed Ionic Gold on Titania, Ceria, and Zirconia

A nonaqueous photodeposition procedure for forming Au nanoparticles oil semiconducting supports (TiO2, CeO2, and ZrO2) was investigated. Intrinsic excitation of the Support wits sufficient to induce Au-0 nucleation, without the need for an organic hole-scavenging species. Photoreduction rates were higher over TiO2, and ZrO2 than over CeO2, likely due to,I lower rate of photogenerated electron recombination. Illumination resulted in metallization of the adsorbed Au species and formation of crystalline Au nanoparticles dispersed across the oxide surfaces. Oil the basis of transmission electron microscopy (TEM) evidence of a strong Au particle-metal oxide interaction, it is proposed that Au deposit formation proceeds via the nucleation of highly dispersed clusters which call diffuse and amalgamate at room temperature to form larger surface-defect-immobilized clusters, with the final particle size being Significantly smaller than that achieved by conventional aqueous photodeposition. From this work, it is possible to draw several new fundamental insights, with regards to both the nonaqueous photodeposition process and the general mechanism by which dispersed metallic Au nanoparticles are formed front ionic precursors adsorbed upon metal oxide supports.