Synergistic effect of carbon dopants on photoinduced water−splitting on graphitic carbon nitride

Graphitic carbon nitride (g-CN), composed of heptazines, holds promise as a photocatalyst for hydrogen evolution. But its suboptimal visible light absorption and poor electrical conductivity limit photocurrent density and catalytic activity. Carbon atom doping, specifically carbon-modified g-CN (C/g-CN), enhances photocatalytic performance. This study investigates the impact of carbon dopants at the three-coordinated nitrogen atom (N3C) and the two-coordinated nitrogen atom (N2C) sites on the reaction mechanism of water-splitting in the ground and excited states. Nonadiabatic dynamics simulations are employed on water hydrogen-bonded to C-doped heptazines (H2O⋯C/heptazine) to unveil the molecular-level decomposition mechanism in the excited states. The simulations reveal that the C dopants at N2C improve the activity for water-splitting in the ground state. The C dopants at N3C improve the H atom detachment from H2O via the electron-driven proton transfer (EDPT) process. The synergistic effect of carbon dopants on enhanced catalytic activity of C/g-CN is elucidated.