An anomalous peak observed in the electrochemistry of the platinum/perfluorosulfonic acid membrane interface

A solid-state cell is used to study the electrochemistry of platinum at a perfluorosulfonic acid membrane. An anomalous peak is observed in the platinum electrochemistry at approximately 0.6–0.65 V vs. RHE. The plausible origins of this feature are discussed and experiments which were carried out to characterise the conditions under which the anomalous peak is observed are described. Experiments rule out the possibility of contamination and show that conditions of slow scan rate and low membrane hydration facilitate the appearance of the peak. Scan rate tests indicate that the anomalous feature owes to a surface process. A possible explanation for the origin of the peak is the formation of oxygenated species on the platinum surface.