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 we report a benzene ring doped g‐C3N4 via one‐pot thermal polycondensation of dicyandiamide and 2,4‐diaminobenzenesulfonic acid. 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 reasons for enhanced photocatalytic performance are 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.