Facile embedding of aromatic carbon rings into the 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 a 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 (CNA_n) catalysts were prepared via the copolymerization method by adjusting the amounts of 2-aminobenzonitrile (ABN) and urea. In CNA_n samples, aromatic carbon rings were successfully grafted into the 3-s-triazine rings of g-C₃N₄. Comprehensive characterization studies 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.