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

Abstract

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.