Highly stable supercapacitive performance of one-dimensional (1D) brookite TiO2 nanoneedles

Abstract

We report the highly stable supercapacitive performance of one-dimensional (1D) nanoneedles of brookite (β) TiO2 synthesized on a conducting glass substrate. The 1D β-TiO2 nanoneedles synthesized over a large area array utilizing hot-filament metal vapor deposition (HFMVD) were ∼24-26 nm wide, ∼650 nm long and tapered in a downward direction. X-ray photoemission spectroscopy (XPS) revealed their chemical properties and stoichiometric Ti and O composition. The 1D β-TiO2 nanoneedles execute as parallel units for charge storage, yielding a specific capacitance of 34.1 mF g-1. Electrochemical impedance spectroscopy revealed that the large surface area and brookite crystalline nature of the 1D nanoneedles provided easy access to Na+ ions, and resulted in low diffusion resistance, playing a key role in their stable charging-discharging electrochemical mechanism. Moreover, the non-faradic mechanism of these nanoneedles delivered better durability and high stability up to 10000 cycles, and a columbic efficiency of 98%. Therefore, 1D β-TiO2 nanoneedles hold potential as an electrode material for highly stable supercapacitive performance with long cycle lifetime.