Metal Deposition Process from Quaternary Ammonium Triflate-type Non-aluminate Room Temperature Molten Salts

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The redox and/or electrodeposition behaviors of copper, nickel, zinc, titanium, magnesium, and Cu-Mg alloy were examined using an "ammonium imide" room temperature molten salt as a novel electrolytic medium in order to clarify the applicability of the salt to the electrochemical process. Trimethyl-n-hexylammonium bis((trifluoromethyl)sulfonyl)amide (TMHA-Tf_2N), having an electrochemical window of 5.6 V (50 ℃), and metal salts were used to prepare the electrolyte. In TMHA-Tf_2N media monovalent copper ion, Cu(I), was stable and Cu metal was oxidized, or corroded, in the presence of Cu(II) species as : Cu^2+ + Cu → 2Cu^+. Cathodic electrodeposition of copper metal and its anodic dissolution were, thus, one-electron reactions and their current efficiencies were almost 100%.Nickel, zinc, and Cu-Mg alloy can also be electrodeposited from the TMHA-Tf_2N media at a certain potentiostatic condition. The nickel and zinc metals deposited appeared as a gray-colored film, while the magnesium was dendritic. In contrast, though the TMHA-Tf_2N salt containing titanium species gave the redox current of dissolving titanium species, titanium metal was not able to deposit electrochemically.The TMHA-Tf_2N salt containing both Cu^+ and Mg^<2+> ions, provided an Cu-Mg alloy containing about 23 at. % Mg. X-ray diffraction of the alloy gave a set of reflection due to elemental copper, suggesting that the magnesium formed a solid solution with copper.