Enhanced supercapacitor performance using hierarchical TiO2 nanorod/Co(OH)2 nanowall array electrodes

We report novel hierarchical TiO2 nanorod (NR)/porous Co(OH)(2) nanowall array electrodes for high-performance supercapacitors fabricated using a two-step process that involves hydrothermal and electrodeposition techniques. Field-emission scanning electron microscope images reveal a bilayer structure consisting of TiO2 NR arrays with porous Co(OH)(2) nanowalls. Compared with the bare TiO2 NRs, the hierarchical TiO2 NRs/Co(OH)(2) electrodes showed improved pseudocapacitive performance in a 2-M KOH electrolyte solution, exhibiting an areal specific capacitance of 274.3 mF cm(-2) at a scan rate of 5 mV s(-1). The electrodes exhibited good stability, retaining 82.5% of the initial capacitance after 4000 cycles. The good pseudocapacitive performance of the hierarchical nanostructures is mainly due to the porous structure, which provides fast ion and electron transfer, a large surface area, short ion diffusion paths, and a favourable volume change during the cycling process. (C) 2014 Elsevier Ltd. All rights reserved.