Electron-induced effect and coordinated pi-delocalization synergistically promote charge transfer in benzenesulfonic acid modified g-C3N4 with efficient photocatalytic performance

Abstract

Strengthening the photocatalytic performance of graphitic carbon nitride (g-C₃N₄), which simultaneously enhances the original π-conjugated system and promotes the intramolecular charge transfer, has attracted considerable attention. In this work, a small organic molecule of sulfanilic acid (4-ABS) is employed to construct benzenesulfonic acid functionalized g-C₃N₄ (CN-ABS) photocatalysts via a facile thermally induced copolymerization with urea, which can simultaneously expand the delocalization system of g-C₃N₄ and enhance the driving force of photogenerated carrier migration. The experiment and density functional theory calculation reveal that the electron-induced effect of the sulfonic acid group accelerates the directional migration of electrons to improve the delocalization performance of the aromatic ring for melon units. In addition, the synergistic effect of the sulfonic acid group and aromatic ring will induce the charge redistribution of g-C₃N₄ with an optimized band structure, which strengthens the reduction ability of photogenerated charges and expands the visible light absorption range. As a result, the CN-ABS samples display superior photocatalytic H₂ production performance with an apparent quantum efficiency of 5.23% at 420 ± 15 nm and effective photodegradation of reactive red 2.