Electrodeposition of silver aluminum alloys from a room-temperature chloroaluminate molten salt

The electrodeposition of silver-aluminum alloys was investigated at platinum and tungsten electrodes in the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EtMeImCl) molten salt containing electrogenerated silver(I) at 25 degreesC. Sampled-current voltammetry indicated that it is possible to electrodeposit Ag-Al alloys at potentials positive of that where the bulk deposition of aluminum is normally observed (similar to0 V). The aluminum content of these alloys varied with the applied potential and displayed an inverse dependence on the silver(I) concentration, indicating that the alloy formation process was kinetically limited. Experiments conducted in melts with different compositions revealed that at a fixed potential and silver(I) concentration, the atomic fraction of aluminum in the alloy is virtually independent of the melt composition. At high concentrations, silver(I) adsorbs on platinum and tungsten, but this process is inhibited by the addition of benzene. The adsorption process does not appear to affect the codeposition of aluminum with silver. X-ray diffraction analysis of bulk Ag-Al alloy electrodeposits prepared in melt containing benzene as a cosolvent indicated the presence of both face-centered cubic Ag and hexagonal close-packed delta -Ag2Al. (C) 2001 The Electrochemical Society. All rights reserved.