Template Synthesis and Electrochemical Characterization of Nickel-Based Tubule Electrode Arrays

A nickel-based tubule electrode array was fabricated by using electroless deposition with a polycarbonate membrane serving as a template. Hypophosphite was the reducing agent in the Ni deposition, and electrodes made of a Ni−P alloy were formed. The tubule has an internal diameter of ca. 180 nm, a wall thickness of ca. 20 nm, and a length of ca. 2 μm. The electrode array provided an exposed area ca. 8.8 times as large as that of a planar electrode, suggesting a potential application of the array in sensor devices. Cyclic voltammetric measurements in KOH showed that the electrochemical response from the Ni(OH) 2 /NiOOH redox reaction for the electrode arrays was more than 40 times larger than that for an planar electrode. The nanoscale structure of the tubule was concluded to be responsible for this magnification of the redox response. Heat treatment combined with overcharge oxidation of the electrode arrays was found to significantly improve the charge storage capacity resulting from the redox reaction. The present work has provided important concepts capable of improving the performance of a nickel hydroxide electrode for nickel metal hydride batteries.