Initial Anodic Growth of Oxide Film on Platinum in 2N H 2 SO 4 under Galvanostatic, Potentiostatic, and Potentiodynamic Conditions: The Question of Mechanism

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Abstract
Potentiodynamic, galvanostatic, and hybrid galvano‐potentiostatic experiments were conducted in saturated on a polished platinum disk electrode. The results show conclusively that for coverage between one and three monolayers the law of anodic growth of oxide film on platinum is precisely the same regardless of the mode of growth (i.e., potentiostatic, galvanostatic, or potentiodynamic). A correspondence is analytically established between galvanostatic and potentiodynamic data, and this correspondence is verified experimentally. Galvanostatic and potentiodynamic data both show that the growth of the oxide film cannot be explained by any mechanism for which is independent of (e.g., adsorption). The high‐field ionic conduction model accounts for the major features of all the data. A comparison of galvanostatic and hybrid galvano‐potentiostatic experiments shows that there is no aging of the film over a time interval, , comparable to the duration of the experiments . The effect of “holding” (i.e., interrupting the potential sweep and maintaining a constant potential for a time) during potentiodynamic experiments is explained entirely in terms of the potentiostatic growth of the oxide film during the holding period.

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