Charge transfer and band gap opening of a ferrocene/graphene heterostructure

Abstract

The objective of this paper was to study the electrochemical and electronic behavior of pristine graphene used as a catalyst for redox reactions and the charge transport mechanisms that occur in the interface between graphene and covalently attached ferrocene. The covalent grafting and chemical modification of epitaxial graphene by a ferrocene redox marker was performed through electrochemical oxidation of ethylene diamine that provided a low coverage density and a short distance between the ferrocene and graphene. The electrochemical activity, as well as, the electronic and structural properties of the nanomaterials were characterized by Cyclic Voltammetry, Electrochemical Impedance Spectroscopy, X-ray Photoelectron Spectroscopy, RAMAN spectroscopies and Angle-Resolved-Photoelectron Spectroscopy. We show that the proposed modification improved the electronic properties of graphene where p-doping was observed and a band gap opening of about 60 meV was demonstrated. The electrochemical activity and electron transfer ability was inproved. A heterogeneous electron transfer rate of KS = 7 s−1, was obtained thanks to a low density of immobilzed ferrocene and the small spacer provided by ethylene diamine giving a fast tunneling electron transfer. We believe promising perspectives for the development of self-organized graphene electrodes with various electrochemical properties by tailoring the attached redox functional groups.