Functionality of reduced graphene oxide flakes at the growth of conducting zone in polyaniline-graphene composite films

When reduced graphene oxide (RGO) flakes were included in polyaniline (PANI), the PANI-RGO composite film exhibited faster redox conversion than the PANI film did. A reason of the enhancement of the conversion rate was searched by examining the growth rates of the conducting zone which appeared at the boundary between the oxidized and the reduced PANI in the film when the reduced composite was oxidized electrochemically from one end of the film. The film was prepared by drying PANI-RGO colloidal suspensions, which were formed by coating flaky RGO particles with PANI. Higher anodic potentials and higher ratio of RGO fractions enhanced the growth rates. There are several possible reasons for the increase in the rates; electro-catalytic properties for the oxidation, enhancement of the conductivity by RGO, the electric percolation, and enhancement of specific surface area of RGO. The growth rate was modeled with the oxidation at the Tafel-typed rate, which was restrained by the IR-drop between the conducting front and the electrode. The growth length was expressed by a time-dependent non-linear differential equation. The numerical solution allowed us to analyze the experimental data of the time variation of the growth length. RGO functions as an increase in the rough surface area of the oxidation rather than electric percolation, enhancement of conductivity and catalytic effects.