ABSTRACT
When doing electrochemistry with compounds that are sensitive to trace amounts of moisture or oxygen present in nonaqueous solvents, it is necessary to use vacuum electrochemical techniques. The rigorous exclusion of water is particularly important when the starting material is sensitive to moisture, since it can decompose rapidly to hydrolysis products and make the electrochemical measurements erroneous. The products of electrode reactions are often highly reactive species and are usually present at concentrations low enough to make small amounts of water and oxygen critically important. However, specialized vacuum-line techniques might not be required if the starting material is not sensitive to hydrolysis or if only qualitative measurements are done, for it is possible to remove moisture in an electrochemical cell by adsorption onto activated alumina [1]. It has been demonstrated that vacuum technique alone is not sufficient for the complete removal of adsorbed water from the cell [2]. In this case, a special vacuum electrochemical cell equipped with an internal drying column can be used to recirculate the solvent-electrolyte solution over activated alumina to remove the last traces of water. Moisture can be introduced into the electrochemical system via the solvent, the electrolyte, the electrode assembly, and the glass surfaces. Using vacuum-line techniques, the concentrations of water and oxygen inside the cell can usually be reduced to acceptable levels. Further advantages of using vacuum-line techniques include thorough solution degassing and effective long-term isolation of the solution from the atmosphere. In carefully dried and deoxygenated solvents, the usable “potential window” can be increased, since H+ reduction is avoided in dry nonaqueous solvents.
