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

A g-C₃N₄ allotrope, a curved leaf-like graphitic C₂N₃ (g-C₂N₃) with an intrinsic spontaneous polarization electric field (ISPEF), has been constructed for efficient solar energy conversion into H₂ energy via photocatalytic H₂O splitting. The curved leaf-like π-delocalization g-C₂N₃ 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-C₃N₄ allotrope demonstrates a very high H₂-production activity of 14.9 mmol g^-1 h^-1 accompanied by a lot of H₂ bubbles, which is 2.6 times of g-C₃N₄ loading with Pt. In comparison with the reported metal-free photocatalysts or those supported with noble metals, g-C₃N₄ allotrope (i.e., leaf-like g-C₂N₃) is confirmed to be the best metal-free photocatalyst for H₂O splitting into H₂ fuel so far. The contructed leaf-like g-C₂N₃ with SPEF supplies a suitable platform for solar energy conversion into H₂ fuel, which actively contributes to clean energy production.