Magnesium deposition and dissolution processes in ethereal grignard salt solutions using simultaneous EQCM-EIS and in situ FTIR spectroscopy

Magnesium deposition and dissolution processes in ethereal Grignard salt so lutions using tetrahydrofuran as the solvent and Grignard salt which includ ed RMgCl, RMgBr, and R2Mg (R = methyl, ethyl, butyl, or benzyl) are reporte d. Mg dissolution and deposition in these solutions are basically reversibl e with an overall mass balance close to zero for complete cycles. In prolon ged Mg deposition processes, the mass accumulated per mole of electron tran sferred was similar to 12 g/mol, the equivalent weight of magnesium. Howeve r, Mg deposition-dissolution is not a simple two-electron process, but invo lves adsorption-desorption processes of species such as MgR . and/or MgX2 ( X = Cl, Br). These adsorption processes lead the Mg electrodes to develop h igh impedance upon storage in these solutions (up to hundreds of thousands of Omega cm(2)). However, this passivation is not stable, and breaks down a s the electrochemical processes proceed. (C) 1999 The Electrochemical Socie ty. S1099-0062(99)08-012-8. All rights reserved.