Flexible solid-state CuxO-based pseudo-supercapacitor by thermal oxidation of copper foils

Many research efforts point nowadays towards the development of flexible, lightweight and efficient energy storage devices. Herein we report a simple procedure for the fabrication of nanostructured electrodes based on CuxO nanowire/nanoporous layer grown on copper foils and we propose, for the first time to the best of our knowledge, their integration into solid-state pseudo-supercapacitors. An easy and scalable thermal oxidation process in ambient atmosphere is employed to grow a CuxO film on Cu substrates. Electron microscopy, contact angle measurements, infrared and X-Ray photoelectron spectroscopy are employed to obtain a deep understanding of the morphology, wettability, structure and composition of the copper oxides. We show that the annealing time strongly influences the nanostructures formation promoting the evolution of the oxide film from Cu2O to CuO/Cu2O bilayer with the subsequent growth of CuO nanowires. The obtained materials represent flexible and binder-free electrodes for pseudo-supercapacitors in which the current collector and the active element are joined in the same substrate without further processing. The electrical characterizations of symmetric devices fabricated with a polymeric electrolyte show the pseudo-capacitive behavior of the proposed nanostructures. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.