Preparation of graphene film decorated TiO2 nano-tube array photoelectrode and its enhanced visible light photocatalytic mechanism

Graphene film decorated TiO2 nano-tube array (GF/TiO2 NTA) photoelectrodes were prepared through anodization, followed by electrodeposition strategy. Morphologies and structures of the resulting GF/TiO2 NTA samples were characterized by scanning electrons microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. In addition, the optical and photoelectrochemical properties were investigated through UV-visible light diffuse reflection spectroscopy, photocurrent response and Mott-Schottky analysis. Furthermore, the photodecomposition performances were investigated through yield of hydroxyl radicals and photocatalytic (PC) degradation of methyl blue (MB) under visible light irradiation. It was found that GF/TiO2 NTA photoelectrode exhibited intense light absorption both in UV light and visible region, higher transient photoinduced current of 0.107 mA cm−2 and charge carrier concentration of 0.84 × 1019 cm−3, as well as effective PC performance of 65.9% for the degradation of MB. Furthermore, contribution of several reactive species to the PC efficiency of GF/TiO2 NTA photoelectrode was distinguished. Moreover, the enhanced visible light PC mechanism was proposed and confirmed in detail.