Porous graphitic carbon nitride with nitrogen defects and cobalt-nitrogen (Co[sbnd]N) bonds for efficient broad spectrum (visible and near-infrared) photocatalytic H2 production

Abstract

The porous graphitic carbon nitride (g-C3N4) with nitrogen defects and cobalt-nitrogen (CoN) bonds (g-C3N4-Co-K) is prepared by controllable copolymerization of melamine with KOH and Co(NO3)2·6H2O. The method not only provides g-C3N4 with porous structure and CoN bonds that accelerate photoexcited carrier transfer and endow numerous active sites, but also redshifts the g-C3N4 absorption edge into near-infrared (NIR) light region through the introduction of nitrogen defects and thus is suitable for H2 evolution. The g-C3N4-Co-K exhibits significantly superior photocatalytic hydrogen generation performance (808 µmol h−1 g−1) under simulated solar light irradiation, about 15.5 times higher than pure g-C3N4, about 5.2 times higher than g-C3N4 with CoN bonds (g-C3N4-Co), and about 2.1 times higher than g-C3N4 with nitrogen defects (g-C3N4-K). Interestingly, it is for the first time revealed that the synergistic effect of nitrogen defects and CoN bonds result in enhanced H2 generation activity (470 µmol h−1 g−1) under NIR light irradiation.