Fumaric Acid Assistant Band Structure Tunable Nitrogen Defective g-C₃N₄Fabrication for Enhanced Photocatalytic Hydrogen Evolution

Tuning the structural defects of graphite carbon nitride (g-C3N4) is an effective strategy to modify its band structure and promote charge separation, but it is still limited by complex and harsh preparation processes. Herein, g-C3N4 with nitrogen defects were fabricated by one-pot thermal polymerization of urea and fumaric acid. The N-(C)3 site, being the active site for photocatalytic hydrogen evolution, reached at a rate of 94.1 μmol·h-1, which was approximately 2.64 times that of the original g-C3N4. Nitrogen defective g-C3N4 had more electrons and stronger H2O molecule adsorption capacity, identified by systematic experiments and DFT calculations. The carboxyl group of fumaric acid reacted with amino group of urea to prevent self-polymerization process of urea and induce nitrogen defects. The changed band structures promoted the absorption of visible light, effective separation of charge, and increased hydrogen evolution driving force. This work will provide a simple and green approach to prepare nitrogen defective g-C3N4 with tunable band structures.