Carbon Defects Induced Delocalization of π Electrons Enables Efficient Charge Separation in Graphitic Carbon Nitride for Increased Photocatalytic H2 Generation

Carbon defects in graphitic carbon nitride (g-CN) can modulate the electronic structure for efficient separation of electron–hole pairs, and thereby potentially enhance the photocatalytic H2 generation. However, the mechanism on the separation of electrons and holes in C defect-modified g-CN still remains unclear. Here we report an autogenic ammonia gas route via in-situ urea decomposition to create carbon defects in g-CN for realizing increased photocatalytic H2 generation rate of 36.62 µmol h−1 under visible light exposure, which is 10 times higher than that of g-CN obtained in the absence of autogenic ammonia gas (~ 3.63 µmol h−1). Illustrated by the density functional theory calculations, the C defects can not only reduce the band gap for increased light harvesting, but also delocalize the π electrons in valence band (VB) and conduction band (CB) for efficient charge transfer. Such delocalization of π electrons facilitates the efficient separation of electrons in LUMO and holes in HOMO, then promoting the photocatalytic H2 generation. Therefore, the creation of C defects can be used as an effective route to delocalize the π electrons in g-CN for efficient photocatalytic H2 generation.