Electrodeposition of silver-aluminum alloys from room-temperature chloroaluminate molten salts

The electrodeposition of silver-aluminum alloys was investigated in the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EtMeImCl) molten salt containing electrogenerated AB(I) at 25 degrees C. Current-sampled 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 to 0 V). The aluminum content of these alloys varied with the applied potential and displayed an inverse dependence on the Ag(I) concentration, indicating that the alloy formation process was kinetically limited. That is, at a fixed potential, the current for the co-deposition of aluminum cannot keep pace with the mass-transport limited current for silver deposition. Thus, the aluminum content of the alloy declines as the Ag(I) concentration is increased. Experiments conducted in melts with different compositions revealed that at a fixed potential and Ag(I) concentration the atomic fraction of aluminum in the alloy increased as the amount of Al2Cl7- in the molten salt increased.