Phosphorus- and fluorine-co-doped carbon nitride: modulated visible light absorption, charge carrier kinetics and boosted photocatalytic hydrogen evolution

A phosphorus and fluorine co-doped carbon nitride (PF-CN) photocatalyst was synthesized to modulate the band gap structure, visible light response ability and photocatalytic H2 evolution activity. Experimental results demonstrated that the electronic structure of g-C3N4 was regulated by phosphorus replacing the C site and fluorine substituting the N site in the g-C3N4 framework to form P-N species and C-F bonds, respectively. P- and F-co-doped carbon nitride gave rise to a more negative conduction band potential, larger surface area, efficient separation of photogenerated charge carriers and a faster charge transfer rate, contributing to an enhancement of photocatalytic H2 production activity. PF-CN achieved an optimal H2 evolution activity of 1690.56 μmol g-1 which was 17.83 times higher with respect to that of pristine g-C3N4 (94.81 μmol g-1). Meanwhile, PF-CN achieved the highest apparent quantum efficiency of 3.76% at 435 nm.