Electrochemical behaviour of (111) B-Doped Polycrystalline Diamond: Morphology/surface conductivity/activity assessed by EIS and CS-AFM

Overview & Synopsis

Electrochemical activity, morphology and surface electrical conductivity of Boron-Doped Polycrystalline Diamond films prepared by MPCVD have been investigated. Heterogeneous apparent rate constants of three different redox systems, [Fe(CN)(6)](3-/4-), [IrCl(6)](2-/3-) and [Ru(NH(3))(6)](3+/2+) have been measured by both Cyclic Voltammetry and Electrochemical Impedance Spectroscopy on < 100 > textured films with a predominance of (111) faces: first measurements have been done with [Fe(CN)(6)](3-/4-) only on as grown samples, and secondly after a mild electrochemical pretreatment the three redox systems have been investigated. "As-grown" samples showed a moderate average activity which was related to the presence of a minority of electronically conducting areas among insulating zones. Electrochemical treatment in neutral conditions substantially increased the activity and heterogeneous apparent rate constants k(app) for the three couples were measured in the range of 10(-2) cm s(-1) with a good stability in time. Current-sensing AFM images performed ex situ showed that the electrochemically pre-treated material presented a high superficial conductivity whereas the grown sample showed major area of low conductivity.