Effect of acid on passivation of a copper electrode in LiCF3SO3/propylene carbonate in underpotential region

The electrochemical behaviour of a copper electrode is examined using micro electrode (diameter = 0.025 mm) techniques over a wide potential range (+3. 5 to -0.2 V vs. Li/Li+) in LiCF3SO3 which contains propylene carbonate (PC) . Cyclic voltametry and differential pulse voltammetry suggest that water m ay be the cause of passivation of a copper electrode. Small amounts of stro ng acid can prevent this passivation by changing the reduction mechanism of oxygen and water in the underpotential region. X-ray photoelectron spectro scopic analysis reveals that lithium compounds precipitate on copper, even in the underpotential region, when no acid is added to the organic solution . (C) 1999 Elsevier Science S.A. All rights reserved.