Facile synthesis and enhanced visible-light photocatalytic activity of Ag2S nanocrystal-sensitized Ag8W4O16 nanorods

Abstract Narrow band-gap (NBG) Ag 2 S nanocrystals (NCs) attaching on the surface of wide band-gap (WBG) Ag 8 W 4 O 16 nanorods were prepared by employing a facile in situ anion exchange method with the reaction between S 2 − and WO 4 2 - , and the photocatalytic activity was evaluated by the photocatalytic decolorization of methyl orange solution under visible-light irradiation. It was found that in situ anion exchange could uniformly deposit Ag 2 S NCs on the surface of Ag 8 W 4 O 16 nanorods, controllably adjust the size, distribution and amount of Ag 2 S NCs, and solidly connect Ag 2 S NCs to the Ag 8 W 4 O 16 nanorods via the replacement of S 2 − in the solution with lattice WO 4 2 - on the Ag 8 W 4 O 16 surface. The photocatalytic results indicated that the as-prepared Ag 2 S/Ag 8 W 4 O 16 composite photocatalysts exhibited obviously higher activity compared with the pure Ag 8 W 4 O 16 and N-TiO 2 photocatalysts. On the basis of band structures of Ag 2 S and Ag 8 W 4 O 16 semiconductors and the quantum size effect of Ag 2 S NCs, a possible photocatalytic mechanism about the Ag 2 S nanocrystal-sensitized Ag 8 W 4 O 16 nanorods was proposed to account for the effective visible-light photocatalytic activities. This present work may provide some insight into the design of novel and high-efficiency NBG semiconductor NCs coupled with WBG semiconductor composite photocatalysts.