Electrodeposition of Cu from Cu(I) Ions in Ambient-Temperature Molten Salt Baths

The electrodeposition of Cu from Cu(I) ions in ambient-temperature molten salt baths (CuCl-1-butylpyridinium chloride (BPC) system or AlCl3-CuCl-BPC system) has been investigated, and the following results were obtained. (1) The CuCl-BPC binary salt melted at around room temperature, and copper was deposited from it under a 1-electron reaction. Current efficiencies from baths of 66.7mol%CuCl-33.3mol%BPC and 50.0mol%CuCl-50.0mol%BPC were about 100% at 10mA·cm-2 and 90°C. It was also demonstrated that the ion species concerned in the copper deposition are Cu3Cl4- and CuCl2- for the former bath and CuCl2- for the latter. (2) The addition of acetonitrile to CuCl-BPC baths made possible copper deposition under a 1-electron reaction at around room temperature. (3) Copper deposition was also possible from AlCl3-CuCl-BPC ternary baths under a 1-electron reaction, and at 5mA·cm-2 and 70°C, current efficiency was 99.5% and purity was 99.997%.