Cyclic voltammetry and impedance spectroscopy analysis for graphene-modified solid-state electrode transducers

The transducer of solid-state electrodes based on an epoxy-graphite composite was modified by two different methods, such as direct mixed and layer deposition of graphene (commercial and synthesized by electrochemical exfoliation of graphite). The modified electrodes were characterized by cyclic voltammetry and impedance spectroscopy. Also, scanning electron microscopy (SEM) was carried out to acquire information concerning the morphology of the composite electrode. Voltammetric measurements, in presence of [Fe(CN)₆]³⁻ as electroactive standard, determined a quasi-reversible electrochemical behavior under linear diffusion control. Electronic transference for modified and unmodified electrodes was compared. Solid-state electrode modified by inclusion of synthesized graphene showed a better electronic transference at electrode surface, due to the lower potential difference between anodic and cathodic peaks (ΔE = 125 mV) with respect to unmodified electrode (ΔE = 160 mV). Impedance spectroscopy characterization of electrode bodies in solid-state it was revealed a higher electronic conductivity and a supercapacitive behavior for the modified composites (values of intrinsic capacitances in the order of nanofarads) due to inclusions of graphite and graphene in the epoxy matrix. These inclusions were verified through SEM microscopy. The electronic conductivity and the supercapacitive character contributed both to the enhancement of electronic transference at electrode surface.