Electrochemical energy storage of silver and silver oxide thin films in an aqueous NaCl electrolyte

Abstract

We present an investigation into the pseudo-capacitive energy storage potential of silver (Ag) and silver oxide (Ag2O) thin film electrode materials prepared by reactive magnetron sputtering. The growth mode and morphology of the prepared films were investigated using the scanning electron microscope (SEM), which reveals columnar growth structure and microporous sites.The stoichiometry and oxidation states of the silver oxide films were monitored with X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). The XRD results reveal the nano-crystalline nature of the silver and silver oxide thin films with peak intensities indexed at (111) planes.Static and dynamic Contact angle measurements were used to probe the penetration of the aqueous NaCl electrolyte into the pores in the prepared silver and silver oxide films, with surface wettability of all (Ag) and (Ag2O) thin films hydrophilic in nature, which is vital for a good electrochemical performance.The Faradaic redox reactions, capacitance and the charge discharge of the films when exposed to the NaCl electrolyte, were monitored with cyclic voltammetry and chronopotentiometry charge-discharge. Results show that Silver and silver oxide possess specific capacitance of 240.52 F/g and 275.50 F/g at 2 mV/s respectively, which is promising for electrochemical energy storage application.