Electrochemistry in a drop: a study of the electrochemical behaviour of mechanically exfoliated graphene on photoresist coated silicon substrate

Peter S Toth,Robert A W Dryfe,Ernie W Hill,Ian A Kinloch,Kostya S Novoselov,Matěj Velický,Anna T Valota

doi:10.1039/c3sc52026a

Abstract

A micro apparatus for electrochemical studies on individual high quality graphene flakes is presented. A microinjection-micromanipulator system has been employed to deposit droplets of aqueous solutions containing redox-active species directly on selected micro-scale areas of mechanically exfoliated graphene layers on polymer coated silicon wafers. This approach allows the clear distinction between the electrochemical activity of pristine basal planes and the edges (defects) or steps to be measured. Voltammetric measurements were performed in a two-electrode configuration, and the standard heterogeneous electron transfer rate (k°) for reduction of hexachloroiridate (IrCl62−) was estimated. The kinetics of electron transfer were evaluated for several types of graphene: mono, bi, and few layer basal planes, and the k° was estimated for an edge/step between two few layer graphene flakes. As a comparison, the kinetic behaviour of graphite basal planes was measured for the deposited aqueous droplets. The appearance of ruptures on the graphene monolayer was observed after deposition of the aqueous solution for the case of graphene on a bare silicon/silicon oxide substrate.

Highlights

Since the rst isolation of graphene in 2004,1 many studies have been carried out in order to characterise the electronic,[2,3,4,5,6] magnetic,[7,8,9] mechanical[10,11,12] and thermal[13,14,15] properties of this new material
The kinetics of electron transfer were evaluated for several types of graphene: mono, bi, and few layer basal planes, and the k was estimated for an edge/step between two few layer graphene flakes
We present data on the dependence of heterogeneous electron transfer rate, using electrochemical reduction of IrCl62À at high quality mechanically exfoliated graphene akes, as a function of the number of the graphene layers

Summary

Introduction

Since the rst isolation of graphene in 2004,1 many studies have been carried out in order to characterise the electronic,[2,3,4,5,6] magnetic,[7,8,9] mechanical[10,11,12] and thermal[13,14,15] properties of this new material. In 2008, a solid electrolyte and a top gate con guration were employed in order to monitor the gate voltage doping effect on graphene using Raman spectroscopy.[30] In 2009, an individual monolayer of graphene was masked with a photoresist layer and its intrinsic capacitance was investigated using ionic liquids as an electrolyte.[31] In 2011, the rst attempts to study the electron transfer kinetics of individual monolayer graphene akes using solution phase redox couples were reported by Li et al.[32] and in our previous work,[33] where the standard heterogeneous transfer rate constant for the reduction of ferricyanide was estimated to be higher for monolayer

Results

Conclusion