Synthesis and characterization of reduced graphene oxide films by aqueous electrochemical reduction

INTRODUCTION In recent years, the electrochemical synthesis of graphene materials has drawn considerable attention thanks to the negative potentials employed that can overcome the energy barriers to efficiently reduce the... [ view full abstract ]

INTRODUCTION
In recent years, the electrochemical synthesis of graphene materials has drawn considerable attention thanks to the negative potentials employed that can overcome the energy barriers to efficiently reduce the oxygen functional groups (OFGs) in graphene oxide (GO), more than it is possible via chemical methods [1, 2]. In this paper, ErGO films were synthesized by a two-step approach involving a spin-coating step of the GO dispersion and subsequent electrochemical reduction. The effects of OFGs in GO and the electrochemical reduction methods based on potential modulation were assessed.
EXPERIMENTAL
The aqueous dispersions of GO were spin-coated on ITO substrates and dried at 100 °C. The GO films were reduced in aqueous NaNO3 solution by modulated potential approaches in a three-electrode set-up. The structure, morphology and degree of reduction were analyzed by Infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SE) and electrochemical tools.
RESULTS AND DISCUSSION
ErGO thin films with controlled residual content of functional groups can be obtained by electrochemical reduction. The analysis of cyclic voltammograms showed that reduction potential and the electroreduction current plateau obtained by chronoamperometric mode are influenced by the initial content of OFGs in GO films. The FTIR spectroscopy results confirmed the partial removal of OFGs by the decrease in peak intensity of corresponding groups. The Raman measurements indicated the defect degree in ErGO films is dependent on the electroreduction approach. As a measure of electroreduction degree, the ErGO films were used as substrate for nucleation of ZnO nanocrystals, since these employ the OFGs as nucleation sites. It was observed that ZnO nucleation and growth decreased on ErGO (figure 1b and 1d) with respect to corresponding GO substrate (figure 1a and 1c).
This study shows that electrochemical reduction technique has great potential for providing graphene materials with versatile electrochemistry and applicability in various fields.

ACKNOWLEDGMENTS. Financial support from the Romanian National Authority for Scientific Research and Innovation, CNCS – UEFISCDI (project number PN-II-RU-TE-2014-4-0806) is gratefully acknowledged.

REFERENCES
1. H.L. Guo et al., ACS Nano 3, 2653 (2009).
2. A. Pruna et al, J. Nanoparticle Res. 15, 1605 (2013).