Fabrication of nanocomposites composed of silver cyanamide and titania for improved photocatalytic hydrogen generation.

Highly efficient composite photocatalysts composed of silver cyanamide (Ag2NCN) and anatase titania (TiO2) were fabricated through a chemical precipitation process of silver nitrate and cyanamide in TiO2 suspensions. The TiO2 nanoparticles around 15 nm were immobilized on the surface of rectangular Ag2NCN particles to form a hetero-structure, and the contents of TiO2 were varied to tune the structure and the photocatalytic performances. In comparison with single TiO2 or Ag2NCN, the TiO2/Ag2NCN nanocomposites exhibited a prominent improved photocatalytic activity in the hydrogen generation, and the hydrogen evolution rate (1494.0 μmol (g h)(-1)) was higher than most of the reported TiO2-composite photocatalysts. Based on the structure investigation, the photocatalytic mechanism of these TiO2/Ag2NCN nanocomposites was proposed. The enhanced photocatalytic activity was attributed to three points: the matched energy level between TiO2 and Ag2NCN promoted the electron-hole transfer and thus inhibited the recombination of photogenerated electrons and holes; the great electron storage capacity of metallic silver produced in the photocatalytic process also facilitated the charge separation; in addition, the expanded absorption spectrum because of the composite structure enhanced the UV and visible light response ability. These TiO2/Ag2NCN nanocomposites also presented good photocatalytic stability in the typical cycle tests. This work provided new insights into fabricating highly efficient composite photocatalysts containing silver and TiO2 for hydrogen generation.