Electron cloud density localized graphitic carbon nitride with enhanced optical absorption and carrier separation towards photocatalytic hydrogen evolution

High photogenerated carrier recombination and poor visible light response in symmetry graphitic carbon nitride are two classical problems for photocatalytic hydrogen evolution. In this work, we rationally design a novel carbon nitride (DPCN) with asymmetric embeddedness of pyridine ring. The embedded pyridine ring modulates the localization of electron cloud density, resulting in a narrowed bandgap and an enhanced carriers' separation efficiency. They are further confirmed by UV–vis spectra and femtosecond transient absorption (fs-TA) spectroscopy, whose results are consistent with DFT theoretical calculations. This DPCN catalyst shows enhanced photocatalytic hydrogen evolution rate of 180.5 μmol h−1 and the apparent quantum efficiency of 14.6 % at 420 nm, surpassing most reported g-C3N4-based photocatalysts. This work provides a new sight on designing two-dimensional photocatalysts by modulating the localization of electron cloud density through breaking topological symmetry.