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) spec-troscopy, whose results are consistent with DFT theoretical calculations. This DPCN catalyst shows enhanced photocatalytic hydrogen evolution rate of 180.5 mu mol 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 topo-logical symmetry.

Automated summary

The high rate of photogenerated carrier recombination and poor visible light response in symmetry graphitic carbon nitride has been a challenge in photocatalytic hydrogen evolution. In this study, a novel carbon nitride material (DPCN) with asymmetric embeddedness of pyridine ring was designed, which effectively modulates the localization of electron cloud density, resulting in a narrower bandgap and improved carriers' separation efficiency. Experimental results, along with UV-vis spectra and femtosecond transient absorption spectroscopy, confirmed the theoretical calculations. The DPCN catalyst exhibited an enhanced photocatalytic hydrogen evolution rate of 180.5 mu mol h-1 and an apparent quantum efficiency of 14.6% at 420 nm, surpassing most reported g-C3N4-based photocatalysts. This work provides a new perspective on the design of two-dimensional photocatalysts by manipulating the localization of electron cloud density through breaking topological symmetry.