Benzene Ring Engineering of Graphitic Carbon Nitride for Enhanced Photocatalytic Dye Degradation and Hydrogen Production from Water Splitting

The photocatalytic activity of graphitic carbon nitride (g-C₃N₄) strongly depends on its electronic structure. To design the photocatalysts with efficient charge separation and transfer property, here a benzene ring-doped g-C₃N₄ via one-pot thermal polycondensation of dicyandiamide and 2,4-diaminobenzenesulfonic acid is reported. The carbon-rich benzene ring is embedded into g-C₃N₄, which enables the asymmetric modification of the heptazine units in g-C₃N₄ and the extension of the π-conjugate system without altering its long-range order structure significantly. Such molecular structure optimization effectively improves the visible light harvesting and charge carriers separation ability. A high photocatalytic hydrogen evolution rate and dye degradation performance is achieved under visible light irradiation (λ > 420 nm), which is about 8.4 and 4.4-fold higher than that of pristine g-C₃N₄, respectively. The reason for enhanced photocatalytic performance is ascribed to a favorable optical property, suppressed charge carrier recombination, and efficient charge transfer processes. This work provides a green and economical method to functionalize g-C₃N₄ using low-content organic carbon molecule for efficient energy conversion-related applications.