Ag/Ag2S–TiO2 composite film formed using dual phase Ag/Ag2O layer as a sulfurized layer for enhanced photocatalytic activity

Abstract

The Ag/Ag2S–TiO2 composite films were synthesized through vulcanizing sputtering Ag/Ag2O dural-phase template capping layer on the TiO2 film. After hydrothermal vulcanization using thiourea as a sulfur precursor, the initially decorated Ag2O layer transformed into the Ag2S. The surface morphology of the continuous block structure of the Ag/Ag2S composite layer gradually shrinks to form irregular island grains dispersed on the surface of the composite film, with vulcanization reaction duration increased from one to 3 h. The light absorption ability of the Ag/Ag2S–TiO2 composite film was enhanced substantially compared to the TiO2 film because of the surface plasmon resonance effect from the Ag particles and the narrow energy band of the Ag2S. Among various surface morphologies of the Ag/Ag2S–TiO2 composite films, the irregular island Ag/Ag2S grains-decorated TiO2 composite film presents superior photoelectrochemical and photocatalytic degradation performances than the composite films consisting of continuous block and spider-web structure of the Ag/Ag2S decorated layers. The synergistic effects of surface plasmon resonance, Ag pathway between the semiconductors, and Z-scheme charge transfer mechanism explain the high-efficiency photocatalytic activity of the Ag/Ag2S–TiO2 composite films.