Metal oxide nanotubes via electrodeposition for battery-electrochemical capacitor hybrid device.

Charge accessibility in nanotube electrodes and consequent electrochemical properties exploitable for energy storage and sensing device is higher due to their dual surfaces than solid nanowires; however, their controlled growth is often challenging. This article demonstrates synthesis of metal nanowires of cobalt and nickel using a template-assisted electrodeposition technique and its transformation into cobalt oxide (Co 3 O 4) and nickel oxide (NiO) nanotubes by controlled annealing. The materials are characterized for their phase, surface, and morphology. The Co 3 O 4 nanotubes has a spinal-type crystal structure, an inner diameter of ~100 nm and wall thickness of ~220 nm with uniform micropores centered at ~21 nm, whereas NiO has a face centered cubic crystal structure, inner diameter ~90 nm and wall thickness ~330 nm with uniform micropores centered at ~21 nm. The electrochemical charge storability of the nanotubes is evaluated in an aqueous alkaline electrolyte (6 M KOH) using a three-electrode system measurement. The Co 3 O 4 and the NiO nanotubes delivered discharge specific charges of ~324 and ~263 C g−1, respectively, the difference charge storability is attributed to the surface and electrochemical properties. Further, a battery – electrochemical capacitor hybrid device is developed with desirable charge storage performance indicators using the Co 3 O 4 nanotubes and reduced graphene oxide as positive electrode and negative electrode, respectively. This research thereby provides a method for developing scalable, reproducible, and efficient battery-electrochemical capacitor hybrid device using NiO and Co 3 O 4 nanotubes. • Co 3 O 4 and NiO nanotubes are synthesized via template-assisted electrodeposition. • The tubes had higher wall thickness than inner diameter for operational stability. • The nanotubes showed superior surface properties for charge storage. • Co 3 O 4 showed lower electrochemical resistance due to surface characteristics. • A battery – electrochemical capacitor hybrid is fabricated using the Co 3 O 4 nanotubes. [ABSTRACT FROM AUTHOR]