VISIBLE-LIGHT INDUCED HYDROGEN EVOLUTION ON CDS/K4NB6O17 PHOTOCATALYST

The photocatalytic ability of CdS/K4Nb6O17 photocatalyst for H-2 evolution by visible light irradiation was studied in connection with its structure. CdS/K4Nb6O17 was prepared by cation exchange reaction of K+ to Cd2+ ions in aqueous Cd(NO3)(2) solution, followed by sulfurization in aqueous Na2S solution. The catalyst obtained by this procedure showed much higher H-2 evolution activity in aqueous K2SO3 solution under visible light irradiation (lambda>420 nm) than a physical mixture of CdS and K4Nb6O17 powders. This result was interpreted as due to more intimate contact of CdS and K4Nb6O17 in CdS/K4Nb6O17 photocatalyst, which enabled the efficient transfer of excited electrons. The activity of the catalyst was greatly dependent on the sulfurization condition, with this optimum condition: at room temperature for one week. XRD, EXAFS, TEM, and UV-DRS showed that most CdS particles, ca. 10 nm in diameter, existed on the external surface of K4Nb6O17, while a small amount of CdS was inferred to be located at the interlayer space of K4Nb6O17 as ultra fine particles.