Selective Dissolution of Pt-Co Binary Alloys and Surface Enrichment of Platinum in Sulfuric Acid Solution

The selective dissolution of cobalt and the consequent surface enrichment of platinum in Pt Co binary alloys immersed in 0.5 mmol:m(-3) H2SO4 at 298K were investigated. Four different Pt Co alloy thin films with various Pt contents, deposited on glassy carbon sheets by physical vapor deposition, were investigated: 51 at% Pt (Pt-51-Co-49), 43 at% Pt (Pt-43-Co-57), 28 at% Pt (Pt-28-Co-72), and 24 at% Pt (Pt-24-Co-76). When the thin films were immersed for 24 h in a 0.5 mmol:m-3 112SO4 solution, a Pt-enriched layer was formed on the surface of all the alloys due to Coselective dissolution. The enriched layer formed in the higher-Pt alloys (Pt-51-Co-49 and Ft(43)/O-57) significantly suppressed further dissolution, whereas the lower-Pt alloys (Pt28 Co72 and Pt28-Co-26) exhibited more extensive selective dissolution and roughened surfaces. In this study, the selective dissolution and surface morphology of the Pt Co alloys are discussed on the basis of these experimental results.