Dissolution of noble metals and their alloys studied by electrochemical quartz crystal microbalance

The electrochemical dissolution of noble metals (Pd, Pt, Rh) and their alloys (Pd–Pt, Pd–Rh, Pd–Pt–Rh) under conditions of cyclic voltammetry in 0.5 M H2SO4 has been studied using the electrochemical quartz crystal microbalance (EQCM). The extent of dissolution depends on the electrode potential, scan rate and the kind of metal/alloy. The results confirm that Pd and Rh are much more sensitive to dissolution than Pt. It has been found that at relatively low potentials Rh is the most soluble metal, while above a certain potential value (ca. 1 V) Pd dissolves the most rapidly. At a potential slightly lower than the oxygen evolution potential the amount of dissolved metal at scan rate 0.1 V s−1 corresponds to ca. 15% of monolayer of surface atoms for Pd, 4% for Rh and 0.2% for Pt. The EQCM experiments indicate great metal dissolution during the procedure of continuous potential cycling of noble metal alloys through the oxygen region.