Graphitic C₂N₃: An Allotrope of g-C₃N₄ Containing Active Azide Pentagons as Metal-Free Photocatalyst for Abundant H₂ Bubble Evolution

A g -C 3 N 4 allotrope, a curved leaf-like graphitic C 2 N 3 ( g -C 2 N 3 ) with an intrinsic spontaneous polarization electric field (ISPEF), has been constructed for efficient solar energy conversion into H 2 energy via photocatalytic H 2 O splitting. The curved leaf-like π-delocalization g -C 2 N 3 was composed of aromatic azide pentagons and normal triazine hexagons obtained by cycloaddition between −C≡N groups from dicyandiamide polymerization and azide from the heat-treated polypyrrole fibers. Under light irradiation (λ > 420 nm), photo-generated charges are driven to separate efficiently and transfer from bulk to active sites of the surface under ISPEF that is opposite to the Coulomb field. Consequently, without any cocatalyst, g -C 3 N 4 allotrope demonstrates a very high H 2 -production activity of 14.9 mmol g –1 h –1 accompanied by a lot of H 2 bubbles, which is 2.6 times of g -C 3 N 4 loading with Pt. In comparison with the reported metal-free photocatalysts or those supported with noble metals, g -C 3 N 4 allotrope ( i.e., leaf-like g -C 2 N 3 ) is confirmed to be the best metal-free photocatalyst for H 2 O splitting into H 2 fuel so far. The contructed leaf-like g -C 2 N 3 with SPEF supplies a suitable platform for solar energy conversion into H 2 fuel, which actively contributes to clean energy production.