Titanium dioxide-decorated rGO as an effective electrode for ultrahigh-performance capacitive deionization

•Wide range of TiO2/rGO ratios were investigated as an efficient CDI electrodes.•CDI performance is extraordinarily augmented by combination of rGO and TiO2.•The best TiO2/rGO ratio achieved the highest specific capacitance of 635.1 F/g. Capacitive deionization (CDI) technology has received great attention in water desalination. In this study, the performance of reduced graphene oxide (rGO) decorated with TiO2 nanoparticles (NPs) was investigated. Electrodes were synthesized via a modified Hummers’ method followed by a hydrothermal treatment step. Different TiO2 percentage (0, 10, 15, 25, 50, 75, and 100 wt% with respect to rGO) were investigated. The morphology, surface area, wettability, crystal structure and chemical composition of the as-prepared materials were characterized. Transmission electron microscopy (TEM) images indicated the homogeneous distribution of TiO2 on the rGO sheets with an average particle size of 9.3 nm. The performance of the prepared rGO-xTiO2 nanocomposite electrodes in terms of electrochemical behavior was evaluated by cyclic voltammetry (CV) experiments. The results illustrated that among all the prepared rGO-xTiO2 electrodes, the rGO-15TiO2 electrode showed the best performance in CDI, because of the significant improvement in its hydrophilicity and surface area. The rGO-15TiO2 electrode achieved the highest specific capacitance of 635.1 F/g, corresponding to 7 and 19 times greater than those of the rGO- (87.77 F/g) and TiO2-based (7.039 F/g) electrodes, respectively. These results indicate excellent potential for the application of this electrode in CDI and energy storage.