The Preparation Of Novel Titanium Dioxide Electrodes And Study On Capacitive Properties

Supercapacitors,as one type of clean energy storage devices,have been attracting much interest owing to their high power density and long cycle life.Due to their higher power density than that of secondary batteries and higher energy density than that of physical capacitors,the supercapacitors efficiently bridge the gap between the secondary batteries and the physical capacitors.However,the energy density of supercapacitors is still far from the increasing requirement of energy storage application.We introduced the titanium dioxide nanowire arrays grown on titanium substrate as novel binder-free negative electrode for aqueous asymmetric supercapacitor in the paper.Firstly,the binder-free TiO₂ NWAs electrode anchored on the titanium substrate is prepared via a two step method combining a chemical oxidation?with melamine as soft-template?process with a pyrolysis process.The TiO₂ NWAs precursor is obtained via the dissolution of titanium to titania sol and the recrystallization to titania nanowire arrays gel assisted by the melamine.Due to the good electrochemical stability and the high over-potential for hydrogen evolution,the TiO₂ NWAs electrode exhibits ultra-negative potential range in the aqueous electrolyte?0^-1.4 V vs SCE?,making it ideal for the negative electrode of asymmetric supercapacitor.After a series of characterization of TiO₂ NWAs and a series of tests of TiO₂ electrodes,it has been proved that the aqueous asymmetric supercapacitor assembled with this titanium-based TiO₂ NWAs exhibited a higher volume energy density.Secondly,to improve the energy density of the TiO₂ NWAs electrode based high cell voltage aqueous asymmetric supercapacitors,a binder-free multi-layered carbon coating hydrogenated TiO₂-? phase nanowire arrays?ML-HTO?electrode is facilely constructed via introduction of a carbon coating network layer between two hydrogenated TiO₂ NWAs layers.The well-defined three dimensional?3D?nanostructure endow the ML-HTO electrode higher active TiO₂ material loading,continuous electric conductive networks,short ionic transport channels and functionalized hydrophilic surfaces.As results,such an electrode exhibits extremely higher areal specific capacitance(710.7 mF cm^-2).Thus,for the first time,a novel aqueous asymmetric supercapacitor is assembled with the ML-HTO electrode as the negative electrode and the home made MnO₂ electrode as the positive electrode.Surprisingly,this aqueous asymmetric supercapacitor presents ultrahigh cell voltages?2.4 V?and high volumetric energy densities of 90.3 Wh kg^-1 at the power density of 349.0 W kg^-1.