Cathodically Dissolved Platinum Resulting from the O₂ and H₂O₂ Reduction Reactions on Platinum Ultramicroelectrodes

The cathodic dissolution of platinum, resulting from the oxygen reduction reaction (ORR) or hydrogen peroxide reduction on platinum, has been investigated. Highly oxidizing hydroxyl radicals (OH^•) are believed to be the species responsible for the platinum dissolution phenomenon. These radicals are produced from the ORR byproduct, hydrogen peroxide, through a 1 electron reduction pathway (H₂O₂ + e^- → OH^• + OH^-). Platinum ultramicroelectrodes (UMEs) were polarized sufficiently negative to drive the ORR or H₂O₂ reduction on the platinum surface, mainly using square wave potential pulses but constant applied potential and cyclic voltammetry (CV) were also investigated. The dissolved platinum was detected using a femtomolar level detection technique which involves reducing platinum ions to platinum metal species followed by an electrocatalytic amplification of proton reduction on an inert carbon fiber electrode. This method has allowed the quantification of the amount of platinum metal dissolved into the solution, from which the rate of platinum dissolution could be determined. Additionally, the detection method demonstrates the platinum is dissolved into the solution as an ionic species and does not form metallic nanoparticles.