A Mechanistic Study of Dissolution of Pt–Fe Binary Alloys in 0.5 M H2SO4 Solution by Channel Flow Triple Electrode

Abstract

A channel flow triple electrode (CFTE) was applied for the in situ detection of Fe ions (Fe(II) and Fe(III)) and Pt ions (Pt(II) and Pt(IV)) dissolved from Pt–50at%Fe (Pt–50Fe) and Pt–25at%Fe (Pt–25Fe), under potential cycling in 0.5 M H2SO4 at 298 K. These ions, dissolved from a Pt–Fe alloy working electrode set upstream in a channel, were simultaneously detected on two Au collector electrodes placed downstream by reducing or oxidizing their dissolved ions. When Pt–50Fe was potential-cycled between 0.05 and 1.4 V vs. standard hydrogen electrode, Fe dissolution was significantly enhanced in a double-layer (DL) charging region (0.25–0.85 V), probably owing to the surface diffusion of Pt atoms. In addition, the Fe dissolution was enhanced by Pt dissolution which takes place in a place-exchange potential region (1.2–1.4 V) and in the reduction potential of Pt oxides (0.9–0.5 V) in the cathodic scan. On the contrary, when Pt–25Fe was potential-cycled between 0.05 and 1.4 V, Fe dissolution was strongly suppressed by a Pt–enriched layer, especially in the potential region for the DL. The dissolution also depended on the upper limit of potential cycling (EU) and was significantly suppressed, even for Pt–50Fe, when EU was 0.6 V.