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-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.