The electrodeposition of Cu from Cu(I) ions in ambient-temperature molten salt baths (CuCl-1-butylpyridinium chloride (BPC) system or AlCl
3-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 Cu
3Cl
4- and CuCl
2- for the former bath and CuCl
2- 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 AlCl
3-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%.
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