Band structure engineering of polymeric carbon nitride with oxygen/carbon codoping for efficient charge separation and photocatalytic performance.

The high charge recombination efficiency and weak visible-light absorption of polymeric carbon nitride (CN) severely suppress its photocatalytic performance. To overcome these defects, oxygen/carbon codoped CN (OCN) was prepared firstly using acrylamide as the additive. OCN exhibits much enhanced visible light absorption, charge separation and transfer, and thus photoactivity in hydrogen production and environmental remediation. OCN exhibits a ~6-fold higher photocatalytic hydrogen production rate (~2626 μmol h-1 g-1) than CN, comparable to most of nonmetal-doped CN, and an apparent quantum yield of ~16.3% (420 nm). OCN is also much better at producing singlet oxygen than CN. The significantly enhanced charge separation for OCN arises from the O/C codoping structure which forms an impurity level above the valence band edge in the bandgap, i.e., works as a hole-capture center. This work affords a simple and effective strategy to synthesize modified CN for photoactivity enhancement, clarifies the doping mechanism, and may guide research on other nonmetal doped organic semiconductor photocatalysts.