Poly(4-vinylphenol) as a new stable and metal-free sensitizer of titania for visible light photocatalysis through ligand-to-metal charge transfer process

Abstract

In this study, poly (4-vinylphenol) (denoted as PVP) was firstly used as a stable and low-cost sensitizer of titania for visible light photocatalysis. The PVP thin-layer was readily grafted on TiO2 (PVP/TiO2) through surface complexation between the multiple hydroxyl groups of PVP and the surface titanol groups (Ti-OH), via simple dispersion of PVP and TiO2 powders in organic solvent. We have demonstrated that the PVP layer sensitizes TiO2 under visible light through the ligand-to-metal charge transfer (LMCT) mechanism. The PVP/TiO2 (with platinum as co-catalyst) composite exhibited a visible light activity of H2 production in the presence of suitable electron donors, whereas phenol-complexed TiO2 (compared as a control) did not generate H2 in the identical condition. Furthermore, PVP/TiO2 exhibited efficient photocatalytic degradation of organic pollutant (4-cholorophenol) under visible light irradiation. In addition, the photoelectrochemical measurements for PVP/TiO2-coated electrodes (PVP/TiO2/FTO) supported the visible light-induced LMCT process on PVP/TiO2, which involves the direct electron transfer from the highest occupied molecular orbital (HOMO) of PVP to the conduction band of TiO2 as the origin of the visible light photocatalytic activity.