Photoluminescent and photocatalytic properties of layered caesium titanates, Cs2TinO2n+1 (n=2, 5, 6)

Abstract

Photoluminescence and photocatalytic H 2 evolution reactions of layered caesium titanates, Cs 2 Ti n O 2n+1 (n =2,5,6), have been studied to evaluate the photoactivity of these materials. Cs 2 Ti 2 O 5 showed a broad emission around 420 nm upon excitation at 270 nm at 77 K, while both Cs 2 Ti 5 O 11 and Cs 2 Ti 6 O 13 showed an emission around 490 nm upon excitation at 290 nm. Cs 2 Ti 2 O 5 showed a blue emission even at 300 K. The Raman spectrum of Cs 2 Ti 2 O 5 was similar to that of the well characterized K 2 Ti 2 O 5 . The results of the luminescence and the Raman spectrum suggested that Cs 2 Ti 2 O 5 consists of a layered structure with TiO 5 units, as observed in K 2 Ti 2 O 5 . Cs 2 Ti 2 O 5 with the five-coordinate structure showed higher photocatalytic activity for H 2 evolution from aqueous methanol solutions than Cs 2 Ti 5 O 11 and Cs 2 Ti 6 O 13 with ordinary six-coordinate structures.