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

• TiO2/Co(OH)2 hierarchical nanostructure was prepared by a combination of hydrothermal and cathodic electrodeposition method.
• Hierarchical nanostructure electrode exhibited a maximum capacitance of 274.3 mF cm−2 at a scan rate of 5 mV s−1.
• Combination of Co(OH)2 nanowall with TiO2 NR into a single system enhanced the electrochemical behavior of supercapacitor electrode.

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.

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