Defective g-C 3 N 4 Prepared by the NaBH 4 Reduction for High-Performance H 2 Production

Defects play a significant part in promoting photocatalytic activity for H 2 production. Various methods such as chemical reduction have been performed to metal oxide based photocatalysts. Herein, we present the NaBH 4 reduction route to introduce the defects into the graphitic carbon nitride (g-C 3 N 4 ) to enhance photocatalytic activity. A new −C≡N group is observed in the FTIR spectra of treated g-C 3 N 4 nanosheets indicating the presence of structural defects. At the same time, the B signal appears in the X-ray photoelectron spectroscopy analysis, suggesting that B is doped in the g-C 3 N 4 during the treatment. All these results manifested that multiple types of defects are introduced in the g-C 3 N 4 during the NaBH 4 treatment. The UV–vis spectra illustrate that the absorption band edge of g-C 3 N 4 is extended from 420 to 450 nm after NaBH 4 treatment. This demonstrates that the band gap of g-C 3 N 4 turns narrow owing to the introduction of defects. Photocatalytic H 2 production of defective g-C 3 N 4 is ∼5-fold better than that of pristine g-C 3 N 4 . To understand the enhanced mechanism, the apparent quantum efficiency, photoluminescent spectra, transient photocurrent and electrochemical impedance spectra are investigated. The results show that the charge separation efficiency is greatly strengthened in the defective g-C 3 N 4 . Upon these findings, the enhancement of catalytic activity can be attributed to both the broad light adsorption range and highly efficient charge separation process.