Facile Embedding of Aromatic Carbon Rings into g-C₃N₄ Framework for Boosting Piezocatalytic Water Splitting

Abstract

Piezocatalysis is a potential green technology that can effectively address environmental pollution and energy crises in an effective manner. Graphitic carbon nitride (g-C3N4) is a promising candidate, featuring unique 2D layered structure and excellent chemical stability. To overcome the limitations of its piezocatalytic performance including a weak piezoelectric response and low charge separation efficiency, a series of aromatic carbon ring-embedded carbon nitride (CNAn) catalysts were prepared via the copolymerization method by adjusting the amounts of 2-aminobenzonitrile (ABN) and urea. In CNAn samples, aromatic carbon rings were successfully grafted into the 3-s-triazine rings of g-C3N4. Comprehensive characterizations and density functional theory (DFT) calculations reveal that the incorporation of aromatic carbon rings not only regulates the structural asymmetry of g-C3N4 and enhances the local unit dipole moment, thereby strengthening the piezoelectric polarization to drive charge separation, but also expands the π-conjugated system to promote electron delocalization, improving in-plane charge mobility. Meanwhile, it has been demonstrated to increase the specific surface area and form mesoporous structures, thus exposing more active sites. Accordingly, the optimal sample (CNA40) achieved an enhanced piezocatalytic water-splitting hydrogen evolution rate of 214.69 μmol·h-1·g-1, which is 3.75 times higher than that of CN. Besides, this study offers novel insights into the design of high-performance piezocatalysts containing organic functional groups.