Influence of electrochemical pre-treatment on highly reactive carbon nitride thin films deposited on stainless steel for electrochemical applications

In this work, a-CNx films prepared by DC magnetron sputtering on stainless steel substrate have been investigated as electrode materials. While their wide potential window was confirmed as a property shared by boron doped diamond (BDD) electrodes, their electrochemical activity with respect to fast and reversible redox systems, [Ru(NH3)(6)](3+)/(2+), [Fe(CN)(6)](3-)/(4-) and [IrCl6](2-)/(3-), was assessed by Electrochemical Impedance Spectroscopy (EIS) after cathodic or anodic electrochemical pre-treatments or for as grown samples. It was shown for the three systems that electrochemical reactivity of the a-CNx films was improved after the cathodic pre-treatment and degraded after the anodic one, the apparent heterogeneous rate constant ko(app) being decreased by at least one order of magnitude for the latter case. A high ko(app), value of 0.11 cm s(-1) for [IrCl6](2-)/(3-) was obtained, close to the highest values found for BDD electrodes. (C) 2012 Elsevier Ltd. All rights reserved.