Promising Supercapacitive and Photocatalytic Performances of TiO2 Nanotubes Loaded with Graphene: Insight on the Quantitative Chatacterisation by EIS

In the present work, graphene (Gr) was successfully electrodeposited on TiO2 nanotubes (TiNT) by electrochemical deposition from dispersed graphene. Graphene was produced by electrochemical exfoliation of pure (P) graphite sheet and 5B pencil cores in sulfate-containing electrolytes. The electrochemical capacitance performance of Gr/TiNT electrodes was investigated by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry techniques. The results demonstrate that Gr/TiNT electrodes are a promising candidate for supercapacitive applications, as they perform better than TiNT alone. Electrochemical impedance spectroscopy is among the most commonly applied approaches for characterizing electrodes for energy applications. The effects of oxygen functional groups are so evaluated in accordance with the parameters derived from the impedance spectra, with the aim of providing insight into the effects of oxygen functional groups in the energy storage process. Oxygen functional groups lowered the surface conductivity of the materials and hindered ions from reaching the pores, resulting in the decrease of the capacitive performance. Moreover, PGr/TiNT electrode have proven to be much more effective photocatalyst than TiNT alone. PGr/TiNT showed a two-fold increase in photocatalytic efficiency under visible light.