Influence of temperature on the charging/discharging process of IrO2 coating deposited on p-Si substrate

The influence of temperature on the charging/discharging process of the IrO2 coating deposited on p-Si has been investigated using cyclic voltammetry. The measured apparent activation energy (E-a) depends strongly on the used scan rate in the cyclic voltammetry measurements. In fact at low scan rates (5 mV/s), E-a for the charging/discharging process has a value of about 2.4 kJ/mol; this is related to a slow process due to diffusion of protons within the IrO2 coating. At high scan rates (500 mV/s), E-a reaches a value close to zero. This has been attributed to the double layer capacitance, which is an instantaneous electrostatic process. (C) 2008 Elsevier B.V. All rights reserved.