Boosting Photocatalytic Activity over Graphitic Carbon Nitride by Hydrogen-Bonding-Assisted Charge Transfer

Abstract

Graphitic carbon nitride (g-C3N4) offers a great number of advantages for use as a photocatalyst to facilitate a wide variety of photocatalytic reactions. However, pristine g-C3N4 suffers from unsatisfactory photocatalytic performance in actual practice. Nonetheless, as a nitrogen-rich layered material, g-C3N4 offers abundant opportunities for the formation of hydrogen bonds between the NH/NH2 groups within the layers, which can incite proton transfer reactions owing to the inherent polarity of the proton donor and acceptor in the hydrogen bond and thereby improve the transport rate of photogenerated carriers, especially for holes. Yet, relatively little work has been done to improve the photocatalytic performance of g-C3N4 through efforts to enhance its hydrogen bond network. The present work addresses this issue by constructing a hydrogen bond network on g-C3N4 by pressurizing a mixture of pristine g-C3N4 nanosheets with water at a temperature of 120 °C for 12 h. The results of nuclear magnetic resonance spectroscopy and density functional theory demonstrate that the hydrogen bonds on the g-C3N4 surfaces provide an additional pathway for the separation of photogenerated electrons and enhanced hole transfer kinetics. The hydrogen bond network formed between the g-C3N4 layers effectively suppresses charge complexation, improves the photocatalytic efficiency of g-C3N4, and increases the selectivity for photocatalytic products. Our results provide valid insights for designing g-C3N4 photocatalysts with high photocatalytic activity.