Nitrogen defect-containing polymeric carbon nitride for efficient photocatalytic H2 evolution and RhB degradation under visible light irradiation

Abstract

Introducing defects in polymeric carbon nitride (CN) in a predetermined way is a great challenge to explicate the effect of defects on the photocatalytic activity. Herein, we provide a pathway to synthesize g-C₃N₄ with nitrogen defects by simply calcining melamine and trithiocyanuric acid at elevated temperature. Nitrogen defects at the N-bridging sites lead to an intermediate energy gap between the valence band and the conduction band, which greatly increases the photon absorption in the visible light range. Electron paramagnetic resonance (EPR) and photoluminescence (PL) verify that the significantly improved light utilization efficiency and rapid charge transfer correlate with nitrogen defects. The hydrogen evolution rate of 2SCN reached 41.4 μmol h⁻¹, about 20.7 times that of pure g-C₃N₄, and its degradation rate for rhodamine B (RhB) is about 2.5 times that of CN. The experimental results proved that the photoinduced electron–hole pairs react with adsorbed O₂ to form ˙O₂⁻, facilitating the photodegradation of organic pollutants.