Excited State Dynamics in Dual-Defects Modified Graphitic Carbon Nitride
Shriya Gumber, Sraddha Agrawal, Oleg V. Prezhdo
Abstract
Significant efforts are focused on defect-engineering of metal-free graphitic carbon nitride (g-C3N4) to amplify its efficacy. A conceptually new multidefect-modified g-C3N4 having simultaneously two or more defects has attracted strong attention for its enhanced photocatalytic properties. We model and compare the excited state dynamics in g-C3N4 with (i) nitrogen defects (N vacancy and CN group) and (ii) dual defects (N vacancy, CN group, and O doping) and show that the nonradiative recombination of charge carriers in these systems follows the Shockley–Read–Hall mechanism. The nitrogen defects create three midgap states that trap charges and act as recombination centers. The dual-defect modified systems exhibit superior properties compared with pristine g-C3N4 because the defects facilitate rapid charge separation and extend the spectrum of absorbed light. The system doped with O shows better performance due to enhanced carrier lifetime and higher oxidation potential caused by a downshifted valence band. The study provides guidance for rational design of stable and efficient photocatalytic materials.