TiO₂–Co₃O₄ Core–Shell Nanorods: Bifunctional Role in Better Energy Storage and Electrochromism

Abstract

A suitably designed heterostructured TiO2–Co3O4 core–shell nanorod array has been found to exhibit improved supercapacitive as well as electrochromic properties as compared to the nanowires of either of the oxides when used individually. The core–shell nanostructures have been grown on an FTO coated glass substrate by preparing TiO2 nanorods through hydrothermal reaction followed by growing a Co3O4 shell layer by electrodeposition. The core–shell electrode shows high specific and areal capacitance of ∼342 F/g and ∼140 mF/cm2 (at scan rate of 100 mV/s), respectively. Such an improvement in supercapacitive behavior, as compared to the behavior of the existing ones, is likely due to increased surface area and modified charge dynamics within the core–shell heterojunction. Additionally, these core–shells also exhibit stable and power efficient bias induced color change between transparent (sky blue) and opaque (dark brown) states with coloration efficiency of ∼91 cm2/C. Porous morphology and strong adhesion to the surface of transparent conducting glass electrode give rise to superior cyclic stability in both energy storage and electrochromic applications, which make these core–shell structures suitable candidates for future electronic devices.