title: Electron transfer kinetics on mono- and multilayer graphene.
abstract: Understanding of the electrochemical properties of graphene, especially the electron transfer kinetics of a redox reaction between the graphene surface and a molecule, in comparison to graphite or other carbon-based materials, is essential for its potential in energy conversion and storage to be realized. Here we use voltammetric determination of the electron transfer rate for three redox mediators, ferricyanide, hexaammineruthenium, and hexachloroiridate (Fe(CN)(6)(3-), Ru(NH3)(6)(3+), and IrCl(6)(2-), respectively), to measure the reactivity of graphene samples prepared by mechanical exfoliation of natural graphite. Electron transfer rates are measured for varied number of graphene layers (1 to ca. 1000 layers) using microscopic droplets. The basal planes of mono- and multilayer graphene, supported on an insulating Si/SiO(2) substrate, exhibit significant electron transfer activity and changes in kinetics are observed for all three mediators. No significant trend in kinetics with flake thickness is discernible for each mediator; however, a large variation in kinetics is observed across the basal plane of the same flakes, indicating that local surface conditions affect the electrochemical performance. This is confirmed by in situ graphite exfoliation, which reveals significant deterioration of initially, near-reversible kinetics for Ru(NH3)(6)(3+) when comparing the atmosphere-aged and freshly exfoliated graphite surfaces.
authors.affiliation: School of Chemistry, §School of Computer Science, ∥School of Materials, ⊥School of Physics and Astronomy, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Matěj
authors.initials: M
authors.lastname: Velický
authors.forename: Dan F
authors.initials: DF
authors.lastname: Bradley
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Cooper
authors.forename: Ernie W
authors.initials: EW
authors.lastname: Hill
authors.forename: Ian A
authors.initials: IA
authors.lastname: Kinloch
authors.forename: Artem
authors.initials: A
authors.lastname: Mishchenko
authors.forename: Konstantin S
authors.initials: KS
authors.lastname: Novoselov
authors.forename: Hollie V
authors.initials: HV
authors.lastname: Patten
authors.forename: Peter S
authors.initials: PS
authors.lastname: Toth
authors.forename: Anna T
authors.initials: AT
authors.lastname: Valota
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Worrall
authors.forename: Robert A W
authors.initials: RA
authors.lastname: Dryfe
keywords: basal plane; electrochemistry; electron transfer; graphene; graphite; kinetics; voltammetry