Impact of plasma-induced surface chemistry on electrochemical properties of microfabricated pyrolytic carbon electrodes

Plasma technology is a widely used approach for carbon activation and enhancing the surface energy by generating various functional groups. Gas selection is an important factor determining the type of functional groups to be formed on carbon surfaces. In this study, we investigate the impact of plasma-induced chemical surface alterations on performance of pyrolytic carbon as electrode material. Pyrolytic carbon electrodes were microfabricated by pyrolysis of SU-8 structures defined using UV lithography and treated using Ar, O2, N2 and air plasma gases. The resulting surface chemistry and geometry were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. Close inspection of electrochemical properties was done by using both outer (Ru(NH3)63+/2+) and inner (Fe(CN)63-/4− and dopamine) redox systems. The electrochemical performances of the carbon electrodes treated with various plasma gases were compared based on information on heterogeneous electron transfer rates determined by cyclic voltammetry and electrochemical impedance spectroscopy. This work provides a fundamental insight into electrochemistry of plasma-modified pyrolytic carbon surfaces and strategies on how to enhance surface properties overcoming possible electron transfer limitations for future enhancement in carbon-based electrochemical applications.