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

The electrodeposition of silver-aluminum alloys was investigated at platinu m and tungsten electrodes in the Lewis acidic aluminum chloride-1-ethyl-3-m ethylimidazolium chloride (AlCl3-EtMeImCl) molten salt containing electroge nerated silver(I) at 25 degreesC. Sampled-current voltammetry indicated tha t it is possible to electrodeposit Ag-Al alloys at potentials positive of t hat 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, indica ting that the alloy formation process was kinetically limited. Experiments conducted in melts with different compositions revealed that at a fixed pot ential and silver(I) concentration, the atomic fraction of aluminum in the alloy is virtually independent of the melt composition. At high concentrati ons, silver(I) adsorbs on platinum and tungsten, but this process is inhibi ted by the addition of benzene. The adsorption process does not appear to a ffect 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 hexag onal close-packed delta -Ag2Al. (C) 2001 The Electrochemical Society. All r ights reserved.