Theoretical design and experimental study a novel direct Z-scheme V2O5/C3N5 heterojunction for efficient photocatalytic hydrogen production

The key to construct an efficient direct Z-scheme heterojunction lies in the selection of two semiconductors with matching Fermi energy levels, visible light response capability and the elaborately designed interface. Herein, a research method that theoretical calculation first and then experimental study was employed to develop an efficient direct Z-scheme V 2 O 5 /C 3 N 5 photocatalyst for hydrogen production . First, the theoretical calculations on the V 2 O 5 (110)/C 3 N 5 (001) heterojunction suggested the large interface binding energy between these two components, their visible-light absorption properties and matching Fermi energy levels, and the charge difference density of V 2 O 5 /C 3 N 5 allowing the migration path of photogenerated carriers in composite structure, which satisfies the requirements for constructing a direct Z-scheme. Then, the V 2 O 5 /C 3 N 5 heterojunction was experimentally constructed by calcining the mixture of 3-amino-1,2,4-triazole and ammonium metavanadate , which Z-scheme charge transfer path was further verified by free radical trapping and in situ irradiated XPS analyses. We also found that N–O bonding was formed between C 3 N 5 and V 2 O 5 , which could provide a favorable interface for facilitating the charge transfer within the heterojunction. The optimal V 2 O 5 /C 3 N 5 -3.7 heterojunction exhibited a H 2 yield of 329.9 μmol/h under the visible light irradiation , 19.8 times that of single C 3 N 5 , and showed an apparent quantum efficiency of 7.21% at 420 nm. The high charge separation of the V 2 O 5 /C 3 N 5 heterojunction is revealed to be mainly responsible for the enhancement in its photocatalytic activity . This work sheds light on the research method that consists of theoretical design first and then experimental study for constructing high-efficiency direct Z-scheme heterojunctions.