Effect of graphene nanoplatelet edges on the iodide/triiodide redox reaction

Carbon electrodes have been extensively studied for the development of Pt-free dye-sensitized solar cells. In this study, the influence of graphene nanoplatelet edges on the activity of an electrolyte reaction was investigated. The reaction activities of graphene nanoplatelet aggregates (GNAs) and graphene nanoplatelets (GNs), which have different surface areas, were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The charge transfer resistances (RCT) of the GNAs and GNs were determined from EIS to be 12 Ω and 1.4 × 103 Ω, respectively. The coefficient components (AW) of the diffusion impedance, known as the Warburg impedance, of GNAs and GNs were 63 Ω Hz0.5 and 1.2 × 102 Ω Hz0.5, respectively. From these results, it was found that the edge plane area of the graphene aggregates affects both the reaction resistance and electrolyte diffusion in the carbon film.