The fabrication and electrochemistry of a new class of graphene?electrodes are presented. Through high-temperature annealing of hydrazine-reduced?graphene oxides followed by high-speed centrifugation and size-selected ltrafiltration,flakes of reduced graphene oxides (r-GOs) of nanometer and?submicrometer dimensions, respectively, are obtained and separated from the larger?ones. Using n-dodecanethiol-modified Au ultramicroelectrodes of ppropriately small?sizes, quick dipping in dilute suspensions of these small r-GOs allows attachment of?only a single flake on the thiol monolayer. The electrodes thus fabricated are used to?study the heterogeneous electron transfer (ET) kinetics at r-GOs and the nanoscopic?charge transport dynamics at electrochemical interfaces. The r-GOs are found to?exhibit similarly high activity for electrochemical ET reactions to metal electrodes. Voltammetric analysis for the relatively slow?ET reaction of Fe(CN)6?3? reduction produces slightly higher ET rate constants at r-GOs of nanometer sizes than at large ones.?These ET kinetic features are in accordance with the defect-dominant nature of the r-GOs and the increased defect density in the?nanometer-sized flakes as revealed by Raman spectroscopic measurements. The voltammetric enhancement and inhibition for?the reduction of Ru(NH3)6?3+ and Fe(CN)6?3?, respectively, at r-GO flakes of submicrometer and nanometer dimensions upon?removal of supporting electrolyte are found to significantly deviate in magnitude from those predicted by the electroneutralitybased?electromigration theory, which may evidence the increased penetration of the diffuse double layer into the mass transport?layer at nanoscopic electrochemical interfaces.
Bo Zhang,Lixin Fan,Huawei Zhong,Yuwen Liu,and Shengli Chen.
Journal of the American Chemical Society,135,10073?10080(2013)