ORIGIN OF OHMIC LOSSES AT CO3O4/TI ELECTRODES

Co3O4/Ti and NiCo2O4/Ti electrodes were prepared in different ways to investigate the origin of the ohmic losses observed experimentally. In particular, titanium was pretreated in various ways including etching with a HF mixture, and reduction by cathodic hydrogen discharge prior to coating. Different types of commercial titanium and different concentrations of the precursors in solution were also tried. Some electrodes were prepared with a RuO2 interlayer. Nickel and mild steel were also used as supports. Parameters to quantify the ohmic losses were the peak distance in voltammetric curves, and the initial slope and the deviation from linearity of current vs sweep rate plots. The experimental picture corroborates the view that the main component of the ohmic drop comes from the insulating barrier which forms at the support/oxide layer interface. The intrinsic conductivity of spinels does not appear to represent the main problem for thermal layers as usually prepared.