Abstract:

Increasing the availability of π-electron in graphitic carbon nitride (g-C₃N₄) can reduce the band gap and thus enhance the photocatalytic hydrogen (H₂) generation activity upon exposure to visible light. However, such strategy has not yet been largely applied to increase the H₂ generation of g-C₃N₄. Herein, we successfully increased the amount of π-electron in g-C₃N₄ by incorporating π-electron-rich benzene rings through copolymerization of melamine and trimesic acid in air. The incorporation of benzene rings not only extends the light absorption of g-C₃N₄ to 650 nm, but also improves the electrical conductivity due to delocalization of π electrons in benzene rings. As a result, a 3.4 times enhancement of photocatalytic H₂ generation was achieved from the g-C₃N₄ with benzene ring incorporation in comparing with that of pristine g-C₃N₄. More interestingly, H₂ generation still occurs under irradiation of the light of λ ≥ 490 nm, above the absorption edge of pristine g-C₃N₄ (～ 460 nm), illustrating the positive effectiveness of incorporated benzene rings on enhancing the H₂ generation capacity of g-C₃N₄. The present work manifests the advantages of increasing π-conjugated electrons on designing highly active g-C₃N₄ photocatalysts.

Key words: Photocatalysis, Hydrogen, g-C₃N₄ , π-Electron, enzene ring