Voltammetric studies of TiO2-nanographite based composites

Abstract

Titanium dioxide (TiO 2 ) is a promising electrode material for use as an electrode in electrochemical energy storage. However, its low electrical conductivity limits its performance. This study investigated the influence of nanographite incorporation and ionic liquid (IL) addition on the structural and electrochemical properties of TiO 2 . Hydrothermally synthesized TiO 2 nanoparticles and TiO 2 modified with the ILs triethylammonium-propane-sulfonic acid tetrafluoroborate ([TEA-PS][BF 4 ]) (TB) and 1-butyl-3-methylimidazolium hydrogen sulfate ([BMIM][HSO 4 ]) (BM) were used to prepare thick-film electrodes of pure TiO 2 (T) and TiO 2 /nanographite (T/NG) composites. Diffractograms revealed TiO 2 oxide phases in the anatase form, along with characteristic graphite peaks. Scanning electron microscopy revealed porous films composed of agglomerated TiO 2 , while Raman spectroscopy confirmed the integrity of the graphitic framework through the characteristic D, G, and 2D bands. Cyclic voltammetry showed that the incorporation of nanographite increased the voltammetric charge by up to three orders of magnitude compared with pure TiO 2 . After normalization by the active mass, the T/NG/BM electrode exhibited the highest specific charge, reaching 6.93 C g −1 under cathodic polarization, whereas pure TiO 2 remained below 0.22 C g −1 . The distinct electrochemical responses obtained for the two ionic liquids indicate that they modify the interfacial charge-storage mechanism through different kinetic pathways. Overall, the results support a hybrid charge-storage mechanism involving surface-confined Faradaic reactions coupled with pseudocapacitive contributions at the TiO 2 /nanographite interface.