Underpotential and overpotential deposition of al onto Cu(111) from the AlCl3-EtMeImCl room temperature molten salt

Abstract

The processes of underpotential (UPD) and overpotential (OPD) deposition of Al onto Cu(111), from the room temperature molten salt AlCl3-EtMeImCl of different compositions, has been investigated by the cyclic volatmmetry (CV) and potentiostatic pulse techniques. It was shown that the CVs of the UPD are characterized by two sharp peaks, while the potentiostatic cathodic and anodic j-t-transients of this process are characterized by two waves indicating that the UPD of Al results in the formation of two structures. The first, less dense one, most probably the (?3x?3)R30? ordered structure of Al is formed at a more positive potential of about 200 mV vs. Al, while the second one, a complete momolayer of Al, is formed at about 20mV vs. Al, just before the reversible potential of Al in these melts (-20mV vs. Al). The OPD of Al was detected at potentials more negative than -30mV vs. Al, occurring through the progressive 3D nucleation and growth mechanism. Slow surface alloying of Al with Cu was found to occur at a potential close to the reversible potential of Al.