VISIBLE-LIGHT INDUCED PHOTOCATALYTIC BEHAVIOR OF A LAYERED PEROVSKITE TYPE NIOBATE, RBPB2NB3O10

Photocatalytic behaviors of some modified layered compounds derived from RbPb2Nb3O10 which was an ion exchanger with perovskite structure were examined. Under visible light irradiation (>420 nm) RbPb2Nb3O10-based catalysts were found to evolve H-2 from an aqueous methanol solution. The rate of H-2 evolution was greatly enhanced by replacing Rb+ ions with H+ ions. Further increase of the activity was obtained by Pt-loading. When [Pt(NH3)4]Cl2 was used as a precursor for Pt-loading instead of H2PtCl4, much higher activity was observed. It was interpreted that in the former case reduced Pt particles were highly dispersed at interlayer spaces due to the intercalation of [Pt(NH3)42+] ions prior to the photoreduction, while Pt particles existed only at the external surface of the catalyst in the latter case. The proposed structures for both catalysts were directly supported by TEM and XPS measurements. Several kinds of alcohols (ethanol, 1-propanol, and 1-butanol) were also used as sacrificial reagents. Among them methanol was by far the most suitable one for H-2 evolution. This remarkable shape selectivity was attributed to the intercalation of reactants into the catalyst.