TiO2-glucose LMCT complex/reduced graphene oxide sheet (rGO): An efficient visible light photocatalyst for Cr(VI) reduction

In this study, reduced graphene oxide (rGO) supported TiO2 photocatalyst was successfully synthesized by a facile wet impregnation method. The synthesized rGO/TiO2 photocatalyst was further surface complexed with simple glucose molecule and their photocatalytic activity was evaluated towards toxic Cr(VI) to Cr(III) reduction. The surface complex formation, morphology and crystallinity of photocatalysts were confirmed by FT-IR, FESEM and XRD techniques. Interestingly, glucose functionalized rGO/TiO2 surface complex showed enhanced photocatalytic activity under visible light irradiation (lambda > 400 nm) in comparison with pure TiO2 and rGO/TiO2 photocatalyts. Almost 100% Cr(VI) (30 ppm) reduction was achieved within 60 min. The remarkable visible light photoreduction activity of glucose functionalized rGO/TiO2 was mainly due to the charge transfer (CT) complex formation between rGO/TiO2 and glucose, which extended a strong visible light absorption up to 500 nm and induced the ligand to metal charge transfer (LMCT). The LMCT complex formation between glucose and TiO2/rGO photocatalyst significantly reduced the excited state carrier's life time (2.5 ns) and facilitate the rapid electron-hole pair separation. Hence, surface complexation of glucose on TiO2/rGO photocatalyst is not only extent the visible light absorption but also increase the electron-hole pair separation that further influence on the photocatalytic Cr(VI) reduction activity.