Effect of interlaced energy bands in polymeric carbon nitride nanotubes on the greatly enhanced visible-light photocatalytic hydrogen evolution

The microstructure design of polymeric carbon nitride (PCN) has been proved to promote the interlayer transport of photogenerated electron, but its influence mechanism is still not unequivocal. Herein, based on the PCN nanotube model with actual thickness, we proposed a novel mechanism by density functional theory (DFT) calculation, which explained the effect of the nanotube structure of photogenerated electron interlayer transport. The calculation results revealed that the bending layers with different curvatures in PCN nanotubes has a varying energy band structure, so there was a phenomenon of energy band interleaving between the layers. Moreover, the generated built-in electric field can drive the transport of photogenerated electron between layers. On the basis of theoretical calculations, PCN nanotubes were synthesized by a typical supramolecular assembly method. As expected, the results were consistent with the calculated results. The synthesized PCN nanotube sample exhibited improved photogenerated carrier separation capabilities, significantly changed band structure, and enhanced hydrogen production performance under visible light (4.35 mmol·g−1·h−1), which was 15.76 times higher than that of layered bulk PCN. The current work can provide new insights into the specific mechanism of the photogenerated electron interlayer transfer for microstructure design.