Preparation and Improved Capacitive Behavior of NiO/TiO2 Nanocomposites as Electrode Material for Supercapacitor

Abstract

Background: Of late, supercapacitors have been drawing great attention over other rechargeable energy storage devices. More efforts are made on the electrode materials of the supercapacitors, in order to improve the specific capacitance and energy density. Based on the past literature, it was stated that pure TiO2 (as electrode material) could promote faradaic reaction to a limited extent due to its low electronic conductivity. Further, this low conductivity could hinder the ion transfer process between electrolyte and electrode during intercalation and de-intercalation, resulting in poor energy density. Hence, it is essential to incorporate high electronic conductivity material into TiO2, for improving the electrochemical performance. Objective: In the present study, the preparation and electrochemical performance of NiO/TiO2 nanocomposites as an electrode material for supercapacitor were extensively studied. Methods: NiO/TiO2 nanocomposites were synthesized by sol-gel method. The as-prepared nanocomposites were characterized by high-resolution TEM, field emission SEM and XRD. The electrochemical behaviors of the electrode using nanocomposites were assessed by means of cyclic voltammetry (CV) and galvanostatic charge-discharge tests. Results: The maximum specific capacitance of the nanocomposites based electrode witnessed through CV test was 405 F g-1 at the scan rate of 5 mV s-1 in 1M Na2SO4 electrolyte. The capacitance retention after 5000 charge-discharge cycles was estimated as 92.32%. The energy and power densities at current density of 1 A g-1 were found to be 5.67 Wh kg-1 and 210.52 W kg-1, respectively. Conclusion: NiO/TiO2 nanocomposites synthesized via sol-gel technique appeared to be flake-like structure. NiO incorporated into TiO2 increased higher electronic conductivity while comparing to pure TiO2. Also, an introduction of NiO into TiO2 improved the specific capacitance, power density, energy density and cycle stability. Due to these facts, combining NiO with TiO2 could be considered to be an efficient way of enhancing the electrochemical performance of electrodes of the supercapacitor.