Electrochemical QCM studies of aluminum deposition and alloy formation on Au(111) in ambient temperature molten salts/benzene mixtures

• Published in: Journal of the Electrochemical Society Vol. 148; no. 12; pp. C799 - C802
• Main Authors: LEE, Jae-Joon, YIBO MO, SCHERSON, Daniel A, MILLER, Barry, WHEELER, Kraig A
• Format: Journal Article
• Language: English
• Published: Pennington, NJ Electrochemical Society 2001
• Subjects: Applied sciences; Chemistry; Electrochemistry; Electrodeposition; Exact sciences and technology; General and physical chemistry; Metallic coatings; Metals. Metallurgy; Production techniques; Study of interfaces; Surface treatment; Gold; Crystal orientation; Electrochemical coating; Molten electrolyte; Transition metal; Aluminium; Aluminium Alloys; Molten salt; Electrodes; Organic solvent; Aluminium Chlorides; Benzene; Noble metal; Electrochemical reaction; Room temperature; Quartz microbalance
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.1417556

Certain aspects of the electrochemical deposition of Al on Au electrodes from ambient-temperature acidic AlCl sub 3 /1-ethyl-3-methyl imidazolium chloride (EMIC) melts have been examined in situ using a quartz crystal microbalance (QCM). These experiments were performed using benzene as a cosolvent to decrease the very high viscosity of the neat molten salt. A linear correlation was found between the change in the frequency of the QCM and the amount of electrodeposited Al for amounts of Al ranging from 0.05 to 0.27 mu g/cm exp 2 . This observation suggests that within this mass range the films are relatively smooth and rigidly bound to the underlying substrate. For lower masses, the plot was also linear, except that the slope was significantly smaller than that expected based on the weight of Al, a phenomenon attributed to mass compensation. Large deviations from linearity were observed when the amount of deposited Al increased beyond 0.27 mu g/cm exp 2 . This behavior is consistent with the growth of discrete Al clusters leading to increased surface roughness and to liquid entrapment within the cluster array, which contributes to the frequency changes measured by the QCM. Long times were required for the mass of the Au electrode to return to its original value following deposition and stripping, which is consistent with the formation of bulk Al/Au alloys as has been earlier proposed.