The interfacial charge transfer in triphenylphosphine-based COF/PCN heterojunctions and its promotional effects on photocatalytic hydrogen evolution

In this study, the novel triphenylphosphine-based covalent organic frameworks (P-COF-1) were firstly introduced into polymeric carbon nitride (PCN) to fabricate P-COF-1/PCN heterojunctions via intermolecular pi-pi interaction. The photocatalytic H-2 production rate over the 9% P-COF-1/PCN heterojunctions is ca. 12 times as much as that of pure PCN. The photoelectrochemical measurements and theoretical calculation results show that due to the well-matched band structure between P-COF-1 and PCN, the photo-generated electrons tend to migrate from P-COF-1 into the conduction band of PCN through the interface of heterostructures. In addition to the pi ->pi* electron transition of conjugated tri-s-triazine units in the 9% P-COF-1/PCN with band gap energy of 2.53 eV, the lone pair electrons of P transition to the pi* orbitals of P-COF-1 (n ->pi*) with lower band gap energy of 1.82 eV results in the effective separation of photo-generated carriers and more visible light absorption, and thus enhanced the photocatalytic hydrogen evolution. (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Automated summary

The novel triphenylphosphine-based covalent organic frameworks (P-COF-1) were introduced into polymeric carbon nitride (PCN) to fabricate P-COF-1/PCN heterojunctions for improved photocatalytic activity in hydrogen evolution. The well-matched band structure between P-COF-1 and PCN facilitates electron migration and enhances photo-generated carriers separation, resulting in enhanced photocatalytic hydrogen evolution efficiency.