Photoreduction of metallic co-catalysts onto novel semiconducting metal oxides

Photoreduction of ionic platinum or gold into metallic nanoparticles on the surface of a new type of porous metal oxide material was done from aqueous solutions of the metal salts. The metallization patterns were investigated in an effort to understand the photo activity and electronic properties of new semiconductor materials. In this study, KTiNbO5 and KNb3O8 were used as starting compounds, and colloids were derived via their chemical exfoliation. The colloids consist of individual lamellar particles that retain their crystallinity from the parent compounds. The colloids were agglomerated into highly porous framework solids. The synthesis provides a low temperature route to stable, porous, polycrystalline materials. Elemental analyses, scanning electron microscopy, and optical absorbance measurements were done to characterize the porous substrates and the metal deposition kinetics. Compared to the gold deposition, the platinum metal nanoparticles were deposited as smaller more widely dispersed islands on the surface of the photocatalysts. The rate of gold deposition was much faster than the platinum and the deposited gold particles were in the 50–400 nm diameter range, with most diameters near 100 nm. The diameters of the particles of platinum varied between 10 and 200 nm, but most were 50 nm or less.