Fluorite TiO2(111) Surface Phase for Enhanced Visible-Light Solar Energy Conversion

The wide band gap of titanium dioxide (TiO2) limits its photoactivity only in the ultraviolet-light region and greatly blocks application of TiO2 in solar energy. Finding a pure TiO2 phase with a band gap around 2.0 eV is a very important issue for solar energy applications. We use the first-principles calculations to predict a fluorite TiO2(111) surface phase formed on the reconstructed high-energy rutile TiO2(011) surface. The band gap of the fluorite TiO2(111) surface phase is about 2.1 eV. We propose that engineering the high-energy surfaces of common TiO2 to obtain the fluorite TiO2(111) surface phase at room conditions is a promising method for the preparation of pure TiO2 materials with visible-light activity.