Rational Design of High-Concentration Ti3+ in Porous Carbon-Doped TiO2 Nanosheets for Efficient Photocatalytic Ammonia Synthesis.

Photocatalytic ammonia synthesis is exciting but quite challenging with a very moderate yield at present. One of the greatest challenges is to develop highly active centers in a photocatalyst for N2 reduction under ambient conditions. Herein, porous carbon-doped anatase TiOx (C-TiOx ) nanosheets with high-concentration active sites of Ti3+ are presented, which are produced by layered Ti3 SiC2 through a reproducible bottom-up approach. It is shown that the high-concentration Ti3+ sites are the major species for the significant increase in N2 photoreduction activity by the C-TiOx . Such bottom-up substitutional doping of C into TiO2 is responsible for both visible absorption and generation of Ti3+ concentration. Together with the porous nanosheets morphology and the loading of a Ru/RuO2 nanosized cocatalyst for enhanced charge separation and transfer, the optimal C-TiOx with a Ti3+ /Ti4+ ratio of 72.1% shows a high NH3 production rate of 109.3 µmol g-1 h-1 under visible-light irradiation and a remarkable apparent quantum efficiency of 1.1% at 400 nm, which is the highest compared to all TiO2 -based photocatalysts at present.