Capacitive performance of vertically aligned reduced titania nanotubes coated with Mn₂O₃ by reverse pulse electrodeposition

Abstract

In this study, a composite material, manganese oxide/reduced titania nanotubes (Mn₂O₃/R-TNTs), was synthesized through incorporation of Mn₂O₃ onto R-TNTs <i>via</i> the reverse pulse electrodeposition technique. The influence of pulse reverse duty cycles on the morphological, structural and electrochemical performance of the surface was studied by varying the applied duty cycle from 10% to 90% for 5 min total on-time at an alternate potential of -0.90 V (<i>E</i> _on) and 0.00 V (<i>E</i> _off). FESEM analysis revealed the uniform deposition of Mn₂O₃ on the circumference of the nanotubes. The amount of Mn₂O₃ loaded onto the R-TNTs increased as a higher duty cycle was applied. Cyclic voltammetry and galvanostatic charge-discharge tests were employed to elucidate the electrochemical properties of all the synthesized samples in 1 M KCl. The specific capacitance per unit area was greatly enhanced upon the incorporation of Mn₂O₃ onto R-TNTs, but showed a decrease as a high duty cycle was applied. This proved that low amounts of Mn₂O₃ loading enhanced the facilitation of the active ions for charge storage purposes. The optimized sample, Mn₂O₃/R-TNTs synthesized at 10% duty cycle, exhibited high specific capacitance of 18.32 mF cm^-2 at a current density of 0.1 mA cm^-2 obtained from constant current charge-discharge measurements. This revealed that the specific capacitance possessed by Mn₂O₃/R-TNTs synthesized at 10% duty cycle was 6 times higher than bare R-TNTs.