Evaluation of Alkyl-Ferrocene Monolayers on Carbons for Charge Storage Applications, a Voltammetry and Impedance Spectroscopy Investigation

Electrochemical properties of functionalized carbons with ferrocene-alkyl monolayer were evaluated with different electrolytes and solvents for charge storage applications. Investigations were performed both by cyclic voltammetry and impedance spectroscopy using edge plane pyrolytic graphite (PG) electrodes, being a good example of fragile and porous carbon material. The functionalization method is based on the electrografting of protected aryldiazonium ions that leads after deprotection to the formation of a covalently attached monolayer. In a second step, C-11-long chain alkyl ferrocene is attached on the platform. The functionalization considerably increases the charge density by a factor of 5-10 depending on the electrolyte with the advantage that it does not alter the structure of the carbon surface. The grafted layer presents a very fast electron transfer kinetics providing an easy way for increasing the charge density in devices like supercapacitors, the charging time being limited by the resistance of the electrolyte.