Synthesis of Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TNT) Composites as an Electrical Double Layer Capacitor.

John Lazarte,Regine Dipasupil,Liza Bautista-Patacsil,Ruey-An Doong,Ramon Eusebio,Aileen Orbecido,Gweneth Pasco

doi:10.3390/nano8110934

Abstract

Composites of synthesized reduced graphene oxide (rGO) and titanium dioxide nanotubes (TNTs) were examined and combined at different mass proportions (3:1, 1:1, and 1:3) to develop an electrochemical double layer capacitor (EDLC) nanocomposite. Three different combination methods of synthesis—(1) TNT introduction during GO reduction, (2) rGO introduction during TNT formation, and (3) TNT introduction in rGO sheets using a microwave reactor—were used to produce nanocomposites. Among the three methods, method 3 yielded an EDLC nanomaterial with a highly rectangular cyclic voltammogram and steep electrochemical impedance spectroscopy plot. The specific capacitance for method 3 nanocomposites ranged from 47.26–165.22 F/g while that for methods 1 and 2 nanocomposites only ranged from 14.03–73.62 F/g and 41.93–84.36 F/g, respectively. Furthermore, in all combinations used, the 3:1 graphene/titanium dioxide-based samples consistently yielded the highest specific capacitance. The highest among these nanocomposites is 3:1 rGO/TNT. Characterization of this highly capacitive 3:1 rGO/TNT EDLC composite revealed the dominant presence of partially amorphous rGO as seen in its XRD and SEM with branching crystalline anatase TNTs as seen in its XRD and TEM. Such property showed great potential that is desirable for applications to capacitive deionization and energy storage.

Highlights

Electrical double layer capacitors (ELDCs) are important engineering devices that can be fabricated using specific nanomaterials
In order to assess whether a material can be an electrochemical double layer capacitor (EDLC) electrode, these properties may be determined through electrochemical means such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS)
The XRD of synthesized pure reduced graphene oxide (rGO) recorded peaks at 24◦ and 43◦. This corresponds to the literature with a phase shift of around 3◦ to the left as the expected peaks corresponding to rGO are found at 27◦ and 46◦

Summary

Introduction

Electrical double layer capacitors (ELDCs) are important engineering devices that can be fabricated using specific nanomaterials. Ions between them maintain their identity as desired and arrange themselves on the electrode surface in response to the electric field between the two electrodes to form an electrochemical double layer. This layer consists of ionic species that accumulated on the electrode–electrolyte interface, effectively making two layers of capacitors connected in series in each of the electrode surface [2]. The diffuse layer contains nonspecifically adsorbed ions This behavior cannot just be achieved by any nanomaterial as it requires high material inertness, conductivity, and surface area available for capacitance [3]. For an EDLC material, a rectangular CV plot with high specific capacitance should be obtained, as this indicates minimized redox reactions during charge transfer, and a steep linear EIS Nyquist plot should be obtained, as this indicates low material resistance [4,5,6]

Methods

Results

Conclusion