Electrochemical dissolution of metallic platinum in ionic liquids

The electrochemical dissolution of Pt in several ionic liquids (IL’s) was studied. Different IL’s were tested assessing their potential to dissolve Pt. Dissolution rate and current efficiency were evaluated. The main focus was on Cl containing IL’s: first generation, eutectic based IL’s and second generation IL’s with discrete anions. Pt dissolution only occurred in type 1 eutectic-based IL’s with a max. dissolution rate of 192.2 g m−2 h−1 and a max. current efficiency of 99 % for the ZnCl2-1-ethyl-3-methylimidazolium chloride IL, and 9.090 g m−2 h−1 and 96 % for the 1:1 ZnCl2–choline chloride ionic liquid. The dissolution occurred via the formation of [PtClx]y− complexes. To form these complexes, addition of a metal chloride was necessary. Furthermore, an IL with an electrochemical window of 1.5 V, preferably 2.0 V is required to achieve Pt dissolution. The added metal salt needed to have a higher decomposition potential than 1.5 V or should be a Pt salt.