Formation of Oxide Films at Platinum Anodes in Alkaline Solutions: II . Temperature Study

Abstract

The kinetics of growth of oxide films at platinum anodes in solution is determined at different temperatures using the galvanostatic charging technique. The growth of the oxide film at potentials above about 1.0V vs.RHE follows the model of high field assisted formation of ions at the metal/ oxide interface and their migration within the oxide film. The activation energy and preexponential factor are determined as 18.5 kcal/mole and 10¹³cm⁻², respectively. These parameters differ significantly from the respective values reported for the growth in acid solutions. Comparison of the growth kinetics in acid and alkaline solutions leads to a serious difficulty. Neither the process of ion formation at the metal/oxide interface, nor the process of ion migration through the oxide phase as the rate‐determining step, can account for the growth kinetics in alkaline solutions, unless it is assumed that different oxide phases form in acid and alkaline solutions. This is, however, an unlikely assumption.