Insights into the role of graphene in hybrid photocatalytic system by in-situ shell-isolated nanoparticle-enhanced Raman spectroscopy

Insightful understanding of how graphene capture photoinduced carrier from semiconductor is one of the most important issue for graphene-supported photocatalysts. Here we employ in-situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) using Ag-core/silica-shell particles (Ag@SiO2) on rhodamine B molecules (RhB)/g-C3N4 nanodots (CNINDs)/electrochemical exfoliated graphene layers (EGLs) reaction platform, to reveal the role of EGLs in hybrid photocatalytic system (HPS). The inherent features of EGLs (such as crystal defects, etc.) for modulating the photoinduced electron-hole separation efficiency of semiconductor are studied. We track the photodegradation process of RhB using dynamic Raman mappings, and combine with hybrid density functional theory (DFT) calculations to present: I) Crystal defects of graphene are prior active sites after they accepted photoinduced carrier from semiconductor; II) Oxygen-containing functional groups for opening/adjusting the band gap of graphene and building the staggered band alignment, can dramatically enhance the photocatalytic efficiency; III) High oxygen content transforms the role of graphene from electron acceptor to electron donor in g-C3N4/graphene system; IV) Graphene can sensitize the semiconductor when an appropriate interface interaction is achieved, for narrowing the band gap and expanding absorption band edge of semiconductor. (C) 2019 Elsevier Ltd. All rights reserved.