Tunable Heptazine/triazine Feature of Nitrogen Deficient Graphitic Carbon Nitride for Electronic Modulation and Boosting Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g-C3N4) as metal-free semiconductor was a fascinating photocatalyst for hydrogen production, suffering from fast charge recombination due to incomplete polymerization. In this regard, nitrogen deficient crystalline with tunable heptazine/triazine feature was obtained. It's found that incorporation of 2,4-diamino-6-hydroxypyrimidine into g-C3N4 framework and the subsequent molten salt re-polymerization pro-cess led to nitride deficient feature and maneuverable tuned heptazine/triazine units, resulting the band gap red shift from 2.53 to 2.08 eV with broadened band tail in the range of about 480-800 nm. Careful characterizations revealed that nitrogen deficient crystalline g-C3N4 exhibited more negative band edge potential and faster charge carrier transfer, which was superior to undoped g-C3N4. The photocatalytic hydrogen production rate of nitrogen deficient crystalline g-C3N4 was boosted to 569.5 mu mol g -1h- 1, which was 3.44 and 8.12 times higher than undoped g-C3N4 and bulk g-C3N4. Besides, the apparent quantum efficiency of optimal catalyst was obtained 10.71 % at 435 nm. This work may offer a useful route to fabricate tunable heptazine/triazine-based carbon nitride photocatalyst for hydrogen production.