(514f) Enhancement of Visible Light Absorption of Ordered Mesoporous Titanium (Ti3+) and Nitrogen Doped Titanium Dioxide Thin Films for Solar Energy Conversion

Authors: 
Islam, S. Z., University of Kentucky
Rankin, S. E., University of Kentucky

The optical and electronic properties of TiO2 thin films provide tremendous opportunities in several applications including photocatalysis, photovoltaics and photconductors for energy production. The primary challenge of using TiO2 thin film for solar energy conversion is its inability to absorb the visible light of the solar spectrum due to its high band gap. In this study, visible light responsive cubic ordered mesoporous titanium (Ti3+) and nitrogen codoped TiO2 thin films (Ti3+-N-TiO2) are prepared by a surfactant templated sol-gel method. Hydrazine is used as a nitrogen source as well as a reducing agent to form Ti3+ in TiO2. To prepare the films, cubic ordered mesoporous TiO2 thin films are first prepared using Pluronic F127 as the template and TiCl4 as the precursor. After aging and calcination, the films are dipped into hydrazine hydrate to induce nitrogen doping / reduction, followed by annealing at low temperature. After doping, the films are confirmed to have an accessible, well-ordered cubic mesopore structure by XRD and SEM analyses.  XPS analysis shows that Ti3+ and both interstitial and substitutional nitrogen are present in the doped films.  The Ti3+-N-TiO2 has a narrower band gap than pure TiO2, and as a result, the Ti3+-N-TiO2 films show better visible-light photocatalytic activity than undoped TiO2 for both the degradation of methylene blue in aqueous solution and hydrogen generation by water splitting. The effects of materials synthesis conditions on the doping process and photocatalytic activity will be discussed.