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-50Fewas 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 (E-U) and was significantly suppressed, even for Pt-50Fe, when EU was 0.6 V. (C) 2017 The Electrochemical Society. All rights reserved.