Microscopic Revelation of Charge Trapping Sites in Polymeric Carbon Nitrides for Enhanced Photocatalytic Activity by Correlating with Chemical and Electronic Structures.

The influences of chemical and electronic structures on the photophysical properties of polymeric carbon nitrides (PCN) photocatalysts, which govern the microscopic mechanisms of the superior photocatalytic activity under visible-light irradiation, have been resolved in this work. Time-resolved photoluminescence and in-situ electron paramagnetic resonance measurements indicate that the photoexcited electrons in the fractured PCNs swiftly transfer to the C localized states where the trapped photoelectrons exhibit longer lifetime compared to those in the ordinary PCNs. Moreover, the structure deviation at the carbon (Cb) atoms around the bridging sites of heptazine ring units, where trapped photoelectrons are localized, has been determined in the fractured PCNs based on the C solid-state nuclear magnetic resonance spectra and the density functional theory calculations. Accordingly, the formation of fractured PCNs by breaking the in-plane hydrogen bonds at a high temperature is a promising strategy for the enhancement of photocatalytic activity.