Selective Photocatalytic CO 2 Reduction to CH 4 on Tri- s -triazine-Based Carbon Nitride via Defects and Crystal Regulation: Synergistic Effect of Thermodynamics and Kinetics.

Realizing the high selectivity of CH 4 from the photocatalytic CO 2 reduction reaction (CO 2 RR) remains a great challenge owing to the lower efficiency of multi-electron transfer and the similar thermodynamic properties of CH 4 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 a -axis. Owing to the increased electron density of the N defect, the kinetic possibilities of CH 4 production have increased. Furthermore, the potential energy of the mid-gap states introduced by the N defect favors the thermodynamics of CH 4 production. The selectivity values of CH 4 based on yield and electrons are 87.1 and 96.4%. This work unravels the mechanism to selectively produce CH 4 from CO 2 photoreduction through the crystalline phase and defect regulation and provides significant guidance for the rational design of CO 2 reduction photocatalysts for selective CH 4 production.