Promotion effect of nanosized Pt, RuO2 and NiOx loading on visible light-driven photocatalysts K4Ce2M10O30 (M = Ta, Nb) for hydrogen evolution from water decomposition

Metal oxide photocatalysts K4Ce2M10O30 (M = Ta, Nb) capable of responding to visible light were synthesized by conventional high temperature solid-state reaction. The photocatalysts have an appropriate band gap energy ca. 1.8-2.3 eV and excellent chemical potential level to evolve H-2 from aqueous solutions containing a sacrificial electron donor (Na2SO3) under visible light irradiation (lambda > 420 nm) without any co-catalyst. When they were loading with Pt, RuO2 and NiOx, the activities for evolving H-2 were prompted markedly. By SEM and TEM investigations, it can be seen that these loading metal and metal oxides are dispersed on the surface of photocatalysts K4Ce2M10O30 (M = Ta, Nb) in diameter of about 10-30 nm particles, especially the NiOx loading even formed double layered structure with metal nickel (Ni) and metal oxide (NiO). The reasons for the increasing activities after these loading may be attributable to facilitate electron migrating from the conduction band of K4Ce2M10O30 (M = Ta, Nb) to the Pt, RuO2 and NiOx nanoparticles, which function as H-2 production sites on the surface of catalysts. The same phenomenon appears on the solid solution K4Ce2Ta10-xNbxO30 (x = 0-10) with loading RuO2. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.