Reduced graphene oxide (RGO) on TiO2 for an improved photoelectrochemical (PEC) and photocatalytic activity

[Display omitted] •TiO2/RGO nanocomposite was fabricated via a hydrothermal method for photocatalysis.•Existence of graphene greatly improved the photocatalytic activity of the TiO2 NPs.•TiO2/RGO photoanode showed 3.3-fold higher photocurrent compared to pure TiO2.•Mott-Schottky plot showed 7.4-fold increase in ND and 64% decrease in WSCL.•RGO enhanced the PEC performance of TiO2 with increasing ND and decreasing WSCL. In this study, TiO2 nanoparticles (NPs) /reduced graphene oxide (RGO) composites were prepared by hydrothermal process and physiochemical, optical, photocatalytic and photoelectrochemical properties of prepared materials was investigated. Photocatalytic activity measurement showed that methylene blue (MB) photodegraded faster by TiO2-RGO composites compared to bare TiO2. Furthermore, photoelectrochemical (PEC) properties of TiO2 and TiO2-RGO electrodes were investigated under the illumination of a 150 W Xe lamp in 1M aqueous solution of KOH as the electrolyte. Moreover, TiO2-RGO electrodes showed greatly improved photocurrent density which is 3.3-fold higher than pure TiO2. Combined analyses of Mott-Schottky plots and electrochemical impedance spectroscopy (EIS) confirmed that RGO in the TiO2-RGO nanocomposite increased the donor concentration (ND), decreased recombination process of charge carriers (τD), thinner the space charge layer (WSCL) and reduced flat band potential (VFb) of the TiO2, thereby greatly enhancing the PEC performances of the TiO2 photoanodes. The improved PEC performance of the TiO2-RGO nanocomposite compared to TiO2 NPs attributed to great enhancement of electron transport through the RGO in the TiO2- RGO film and consequently charge separation.