The spatially oriented redistribute of photogenerated carriers and photocatalytic hydrogen evolution mechanism research on polymeric carbon nitride Van der Waals homojunction

Abstract

The weaker interlayer Van der Waals force of polymeric carbon nitride (PCN) increases the potential barrier of electron transfer between layers, which greatly inhibits the carrier separation efficiency of PCN. Herein, we designed and prepared Van der Waals homojunction of PCN (VHPCN), which the interlayer Van der Waals force forces were instead by Coulomb force. DFT calculated reveals that the equilibrium distance and the interface adhesion energy of VHPCN were significantly decreased and enhanced, respectively, under the function of Coulomb force. The equilibrium distance decreased from 3.27 Å to 2.49 Å and the interface adhesion energy enhanced from −0.35 eV to −1.78 eV. This structure not only the transfer distance of electrons at the interface is effectively decreased, but also the transfer barrier of electrons at the interface is reduced. Thus, the electrons/holes pairs in the VHPCN photocatalyst present the phenomenon of oriented interlayer transfer and ultrahigh carrier separation efficiency under the synergistic effect between the built-in electric field and the interlayer Coulomb force of the Van der Waals homojunction. The optimal VHPCN exhibited the photocatalytic H2 evolution rate and apparent quantum yield (AQY), which are 7.9 mmol·g−1·h−1 and 32.4% (>420 nm), respectively. This work put forward a promising strategy to construct novel Van der Waals homojunction within 2D materials for the desirable photogeneration carrier spatially distribution controlling, which could be generalized to other 2D materials for photocatalytic applications in the advanced energy and environmental field.