ELECTROCHEMICAL DEPOSITION OF ALUMINUM AT VITREOUS CARBON IN A ROOM-TEMPERATURE MOLTEN SALT

摘要

The electrochemical deposition of aluminum at vitreous carbon has been studied in the AlCl_3 : 1-ethyl-3-methylimidazolium chloride molten salt system. In a 1.2:1.0 acidic melt, multiple Al stripping peaks are observed at low coverage, which implies that there are several types of nucleation sites on the carbon surface, In neutral buffered (Nad) melts, a symmetrical oxidation peak at -0.4 V (vs Al/1.5:1.0 melt) suggests aluminum stripping after initial deposition at -1.40 V. This oxidation process becomes two peaks, at -0.2 V and 0.0V, if the potential is held for 180s at -1.40 V before scan reversal. This behavior is believed to be due to the loss by diffusion of NaCl, formed during Al_2Cl_7~- reduction, from the electrode surface during potential hold. As a result, aluminum stripping soon exhausts the supply of NaCl at the surface, and the remainder of the aluminum is stripping into an essentially acidic melt at 0.0 V. Scanning electron microscopy of long-term (3600 s) deposits on vitreous carbon show considerable amounts of chlorine and sodium, in addition to aluminum, suggesting that inclusion of melt has occurred during deposition.