Temperature Study of Oxide Film Growth at Platinum Anodes in H 2 SO 4 Solutions

Abstract

The growth of anodic oxide films at platinum in sulfuric acid solution was studied at different temperatures using galvanostatic transients. The activation energy and preexponential factor for the rate of growth were evaluated. In the plane in which the rate‐determining step occurs the surface density of ions, or ion pairs participating in the growth process, is about 1015 cm−2. This is close to the density of atoms in the surface of the metal. The analysis appears to support the process at the metal/oxide interface being the rate‐determining step. However, the same value for N is compatible with, the field‐assisted place exchange process as the rate‐determining step at the metal/ oxide interface or within the oxide phase. Because the growth follows the same rate equation from the very early stages of oxide formation, the process at the metal/oxide interface seems to be the rate‐determining step.