Photocatalytic activity and reaction mechanism of Pt-intercalated K4Nb6O17 catalyst on the water splitting in carbonate salt aqueous solution

Both the structure of Pt-intercalated K4Nb6O17 catalyst and the photocatalytic activity on the water splitting in aqueous carbonate salt solution were studied using various kinds of analytical measurements such as FT-IR, EXAFS, TEM, SEM and TPR. K4Nb6O17 was the layered semiconductor which have two kinds of interlayer spaces (interlayers I and II), and it was found by FT-IR that the [Pt(NH3)(4)](2+) cation was preferentially intercalated only into the interlayer I of K4Nb6O17. Fine Pt metal particles less than 6 Angstrom (1 Angstrom=0.1 nm) were prepared homogeneously in the interlayer space I by the photoreduction method. By H-2 reduction, some Pt particles grew more than 15 Angstrom and contributed to the destruction of the layered sheet. The photocatalytic water splitting reaction occurred by the addition of carbonate salt in spite of the exposure of Pt on the outer surface of catalyst. The photocatalytic activity of the Pt/K4Nb6O17 prepared by the photoreduction was higher than that prepared by the H-2 reduction. The deactivation of the catalyst was not observed in the carbonate aqueous solution for long time. The reaction mechanism that the Pt particles in the interlayer I acted as H-2 evolution site and the O-2 evolved in the interlayer II was proposed. (C) 1998 Elsevier Science S.A. All rights reserved.