Pseudo-capacitance of silver oxide thin film electrodes in ionic liquid for electrochemical energy applications

Alex.I. Oje,Nathaniel Tsendzughul,Mojtaba Mirzaeian,A.A. Ogwu,A.M. Oje

doi:10.1016/j.jsamd.2019.04.003

Abstract

Abstract The energy storage potential of silver oxide (Ag2O) thin film electrodes, deposited via radio frequency reactive magnetron sputtering, was investigated in an ionic electrolyte (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide for supercapacitor applications. X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR) tools were used to evaluate the structural and oxide phases present in the sputtered silver oxide thin film electrodes. The growth mode, morphology, surface area, wettability and surface energy of the deposited nano-structure silver oxide thin films were confirmed by scanning electron microscope (SEM) data, the Brunauer-Emmett-Teller (BET) analysis and by goniometer and tensiometer studies. Furthermore, the ion diffusion, the Faradaic redox reactions and the capacitance of the sputtered thin films exposed to 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic electrolyte, were monitored with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The SEM micrographs depict that silver oxide thin films exhibit a columnar growth mode. The wettability analysis reveals that Ag2O thin films are hydrophilic, an indication for excellent electrochemical behaviour. Cyclic voltammetry measurements show that Ag2O thin films exhibit a specific capacitance of 650 F/g at higher sputtering power, demonstrating its promising potential as an active electrode for supercapacitor applications.

Highlights

The population of the world is expected to be on the increase as the years go by, the use of energy is expected to increase with population density [1]
In this research, radio frequency magnetron sputtering was successfully used to fabricate thin film electrodes based on nanostructure silver oxide materials, for energy storage application, supercapacitor to be precise
XRD, Raman spectroscopy, XPS and FTIR reveals that the oxide phases belong to silver oxide

Summary

Introduction

The population of the world is expected to be on the increase as the years go by, the use of energy is expected to increase with population density [1]. Activated carbon is one the most investigated carbon materials for EDLC because of their low cost, high surface area and good electrical properties, but yields lower energy density and are unsuitable for high-temperature use [8]. Despite ruthenium oxide excellent electrochemical performance, its toxicity to the environment and its high cost hinders its wider commercialization as electroactive material for supercapacitor applications. Fuji et al [18] and Kim et al [19] reported silver oxide widely used in optical disk storage due to their photoactivation properties Her et al [20] integrated silver oxide thin films into super resolution near field structures, for optical memory applications. The energy storage potential of Ag2O thin films produced by reactive magnetron sputtering was investigated in ionic electrolyte to determine its electrochemical performance and suitability for supercapacitor application. The following voltage range was used for the cyclic voltammetry analysis -1000mV to 1000mV, for scan rate of 2mV/s, 5mV/s and 10mV/s respectively

Results and Discussion

Wettability and Surface Energy Analysis

Conclusions