Electrochemistry of graphene: The current state of the art
Carbon materials are widely used in both analytical and industrial electrochemistry. Glassy carbon (GC) electrodes consisting of sp2 bonds show a wide potential window and are low cost materials in comparison to metal electrodes such as gold or platinum. The electrochemical activity of graphitic electrodes such as GC and highly oriented pyrolytic graphite (HOPG) depends mainly on surface roughness and on the amount and kind of surface oxygen functions. Recently, new carbon-based materials including boron-doped diamond (BDD), BDD nanowire electrodes and carbon nanotubes (CNTs) have attracted considerable interest for electroanalytical applications. While BDD electrodes exhibit enlarged potential windows with low capacitive currents as compared to GC advantageous for electrocatalysis and electro-oxidation of organic compounds, the electron transfer rate is for several analytics (e.g; dopamine) slower at BDD electrodes than on conventional carbon electrodes. The reduction in sp2 carbon prevents catecholamines and nucleic acids to increase the electron transfer through the formation of π−π stacking interactions with BDD electrodes, preventing often biomolecular detection with good sensitivity and selectivity on unmodified BDD interfaces. The last decade has thus, in parallel, seen an extraordinary amount of research devoted to the electrochemical properties of nanometer sized sp2 hybridized carbon materials such as carbon nanotubes, fullerenes and most recently graphene-based electrodes. The rapidly growing interest in graphene and related materials such as graphene oxide (GO) and reduced graphene oxide (rGO) is due to the promising electrochemical characteristics such as large potential window, fast heterogeneous electron transfer kinetics and increased capacitance of these materials. In this chapter, the bulk electrochemical properties of graphene-based interfaces will be discussed. The importance of the graphene source on the electrochemistry of these electrodes will be highlighted. Thereafter, advancements related to electrochemical sensing and for energy storage will be presented.