Characterization of boron doped diamond electrodes during oxidation processes: relationship between electrochemical activity and ageing time

The paper presents the results on the evolution of electronic features and electrochemical activity of boron doped diamond samples during oxidative ageing tests. For 1 cm(2) of electrode surface, the resistance increases from 7 12 to about 200 12 during the first hour of work, than it decreases down to 2 Omega in 350 h. In this condition, high values of heterogeneous electron-transfer rate constants for ferro/ferricyanide are measured in the order of 10(-4) cm/s, indicating a semi-metallic behaviour of the samples. Results from Raman analyses are also presented and a possible explanation of the observed behaviour of the samples is proposed, in terms of both the intrinsic movement of the H within the structure of the film and the variation of free acceptor levels associated to the B atoms in the lattice. (c) 2006 Elsevier B.V. All rights reserved