P-π conjugated hydroxyl grafted carbon nitride with enhanced carriers generation and transfer for boosting H2 evolution

Conjugated structure modification is an effective strategy for improving the photocatalytic activity of graphitic carbon nitride (g-C3N4). Herein, we introduce p-π conjugated to g-C3N4 by surface grafting of hydroxyl (-OH) groups through a facile hydrothermal process to improve the photo-carriers generation and separation. Experiments and DFT calculations indicate that the hydrothermal treatment decorated –OH groups onto the C sites of g-C3N4 and formed p-π conjugated structure between the 2p orbitals of the O and the π orbitals of the tri-s-triazine unit. The extended p-π electrons delocalization of g-C3N4 increases the concentration of the carriers, and the –OH groups serve as electrons transport channels facilitating the separation of the carriers. Consequently, –OH grafted g-C3N4 with hydrothermal treated at 120 °C exhibits the highest and recyclable H2 evolution rates of 2.3 mmol h−1 g−1 under simulated sunlight irradiation, which outperform pristine g-C3N4 1.42 times. This work proposes a new mechanism of the p-π conjugate of –OH decorated g-C3N4 for improving charge carriers formation and separation, and provides a mild strategy to engineer the other conjugated molecular structures.