Tuning Nitrogen Content in Carbon Nitride by Isonicotinic Acid for Highly Efficient Photocatalytic Hydrogen Evolution

Graphical This study reports a strategy to tune nitrogen content in carbon nitride using isonicotinic acid as an additive in the precursors. The nitrogen-rich and nitrogen-deficient g-C 3 N 4 samples display enhanced visible light absorption and improved separation of charge carriers, and thus the high hydrogen evolution rate. Graphitic carbon nitride (CN) with various nitrogen contents can be prepared to regulate its electronic structure and energy band levels. The newly-prepared graphitic carbon nitride manifests high photocatalytic activity. In this work, nitrogen-rich CN (CN-NR100) and nitrogen-deficient CN (CN-ND500) were prepared by tuning nitrogen contents in CN while using isonicotinic acid (IA) as an additive in the precursors. It is found that IA reacting with urea can introduce its nitrogen to CN, while reacting with CN can take away the amino group of CN, thus reduces its nitrogen content. Interestingly, the gas that comes from the decomposition of IA is essential for the formation of porous morphology in CN. Both CN-NR100 and CN-ND500 can provide more photocatalytic sites, narrow bandgaps to enhance the absorption of visible light and significantly improve the charge carrier separation efficiency. Therefore, CN-NR100 and CN-ND500 manifest an excellent photocatalytic hydrogen evolution rate of 73 μmol h −1 (about 4 times of that of CN) and 120 μmol h −1 (6.7 times of that of CN), respectively. This work provides an efficient strategy to prepare CN with different nitrogen contents by pyrolysis of precursors modified by IA for high photocatalytic hydrogen evolution.