Effect of potential cycling on dissolution of equimolar Pt–M (M: Co, Ni, Fe) alloys in sulfuric acid solution

Abstract

Dissolution of equimolar Pt–M (M: Co, Ni, Fe) alloys covered with a Pt-enriched layer on the surface has been studied under potential cycling in 0.5M H2SO4 solution at 25°C. The Pt-enriched layer was formed on the surface of Pt–M alloys by a selective dissolution treatment of M under immersion condition in the solution. The amounts of Pt and M dissolved under potential cycling with various combinations of upper potential limit Eupper and lower potential limit Elower were determined with an inductively coupled plasma mass spectrometry (ICP-MS). During the selective dissolution treatment, rest potential Erest of the Pt–M alloys approaches to that of pure Pt, indicating the enrichment of Pt on the surface. The Pt-enriched layer strongly suppresses further selective dissolution of M under the immersion condition. However, when the Pt–M alloys are exposed under potential cycling in the potential ranges of Eupper>Erest (≈1.0V vs. SHE) and Elower<0.5V, the selective dissolution of M takes place again, although it is suppressed at the initial stage of the potential cycling by formation of the thicker Pt-enriched layer.