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

Abstract 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 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.