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

Abstract 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 N 2 reduction under ambient conditions. Herein, porous carbon‐doped anatase TiO x (C‐TiO x ) nanosheets with high‐concentration active sites of Ti 3+ are presented, which are produced by layered Ti 3 SiC 2 through a reproducible bottom‐up approach. It is shown that the high‐concentration Ti 3+ sites are the major species for the significant increase in N 2 photoreduction activity by the C‐TiO x . Such bottom‐up substitutional doping of C into TiO 2 is responsible for both visible absorption and generation of Ti 3+ concentration. Together with the porous nanosheets morphology and the loading of a Ru/RuO 2 nanosized cocatalyst for enhanced charge separation and transfer, the optimal C‐TiO x with a Ti 3+ /Ti 4+ ratio of 72.1% shows a high NH 3 production rate of 109.3 µ mol 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 TiO 2 ‐based photocatalysts at present.