Selective Photocatalytic CO Reduction to CH on Tri--triazine-Based Carbon Nitride via Defects and Crystal Regulation: Synergistic Effect of Thermodynamics and Kinetics.

Realizing the high selectivity of CH from the photocatalytic CO reduction reaction (CO RR) remains a great challenge owing to the lower efficiency of multi-electron transfer and the similar thermodynamic properties of CH and CO. Herein, nitrogen-deficient carbon nitride two-dimensional (2D) nanosheets were prepared via the high-temperature crystalline phase transformation process. Optimizing crystallinity enhances the in-plane polarization along the -axis. Owing to the increased electron density of the N defect, the kinetic possibilities of CH production have increased. Furthermore, the potential energy of the mid-gap states introduced by the N defect favors the thermodynamics of CH production. The selectivity values of CH based on yield and electrons are 87.1 and 96.4%. This work unravels the mechanism to selectively produce CH from CO photoreduction through the crystalline phase and defect regulation and provides significant guidance for the rational design of CO reduction photocatalysts for selective CH production.