Increasing π-electron availability in benzene ring incorporated graphitic carbon nitride for increased photocatalytic hydrogen generation

Increasing the availability of π-electron in graphitic carbon nitride (g-C 3 N 4 ) can reduce the band gap and thus enhance the photocatalytic hydrogen (H 2 ) generation activity upon exposure to visible light. However, such strategy has not yet been largely applied to increase the H 2 generation of g-C 3 N 4 . Herein, we successfully increased the amount of π-electron in g-C 3 N 4 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-C 3 N 4 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 H 2 generation was achieved from the g-C 3 N 4 with benzene ring incorporation in comparing with that of pristine g-C 3 N 4 . More interestingly, H 2 generation still occurs under irradiation of the light of λ ≥ 490 nm, above the absorption edge of pristine g-C 3 N 4 (∼ 460 nm), illustrating the positive effectiveness of incorporated benzene rings on enhancing the H 2 generation capacity of g-C 3 N 4 . The present work manifests the advantages of increasing π-conjugated electrons on designing highly active g-C 3 N 4 photocatalysts.