Switching charge transfer process of carbon nitride and bismuth vanadate by anchoring silver nanoparticle toward cocatalyst free water reduction

摘要

With the aim of exploring and modulating the interfacial charge kinetics, a ternary g-C3N4/Ag/BiVO4 was constructed with excellent photocatalytic performance and preferable stability toward H-2 evolution in absence of cocatalyst. Both density functional theory (DFT) and experimental results implied that the type II g-C3N4/BiVO4 composite can be switched to Z-scheme via Ag nanoparticles as the electron shuttle. The optimal photocatalytic H-2 yield rate achieved for g-C3N4/Ag/BiVO4 was 57.4 mu mol.g(-1).h(-1), being far surpassed the H-2 harvest rate of g-C3N4/BiVO4, Ag/g-C3N4 and g-C3N4, which is 2.9, 14.8 and 1.7 mu mol.g(-1).h(-1), respectively. The apparent quantum efficiency of g-C3N4/Ag/BiVO4 photocatalyst was also determined to be 1.23%. Besides, the photocatalytic performance of g-C3N4/Ag/BiVO4 well preserved over 5 runs in 50 h. The improved H-2 production performance is considered as the consequence of promoted segregation of photoexcited charge carriers and SPR effects of Ag nanoparticles. In combination with photocurrent measurement, examination of active species and DFT calculation, it is found that Ag nanoparticles as an electron mediator can highly promote the Z-scheme carrier migration that electrons come from conduction band of BiVO4 will quickly assemble with the photo-induced holes from valence band of g-C3N4, leaving electrons in the conduction band of g-C3N4 and holes in valence band of BiVO4 that could greatly enhance the charge separation efficiency. (C) 2018 Elsevier Inc. All rights reserved.