Electrodeposition of ordered mesoporous cobalt hydroxide film from lyotropic liquid crystal media for electrochemical capacitors

Abstract

A novel ordered mesoporous cobalt hydroxide film (designated H_I-e Co(OH)₂) has been successfully electrodeposited on titanium substrate from the hexagonal lyotropic liquid crystalline phase using surfactant Brij 56 as the structure-directing agent. Low-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies indicate that the film electrodeposited from the liquid crystal template has a regular nanostructure consisting of a hexagonal array of cylindrical pores. Cyclic voltammeter (CV) and galvanostatic charge/discharge measurements show that the ordered mesoporous H_I-e Co(OH)₂ film electrode has excellent electrochemical capacitance between a potential range of –0.1–0.45 V, and a maximum specific capacitance as high as 1084 F g^–1 could be achieved in 2 M KOH solution at a charge–discharge current density of 4 A g^–1. Meanwhile, the properties of Co(OH)₂ film electrodeposited from aqueous solution without templates (designated Aq-e Co(OH)₂) are also discussed for comparison.