Potentiometrical investigations of nanocrystalline copper

Various samples of nanocrystalline copper have been investigated as electrodes in acid CuSO4 solutions, with the objective of examining growth and relaxation processes by studying the time dependence of the potential E. During the dissolution of Cu2O the disproportionation of Cu+ ions and the formation of nanocrystalline copper was detected in the E(t) curve. A simple model for estimating the surface relaxation according to the Gibbs-Wulff theorem was applied to crystals with shapes varying between cube and octahedron. When the edge atoms are included in the energetic calculations, the excess surface energy becomes dependent on the size of the crystals. Surface relaxation then interferes with crystal growing. In agreement with these results, no separate time region of relaxation could be found for the E(t) of nanocrystalline copper. It was shown that the accurate measurement of electrode potentials of copper requires attention to the specific electrochemical properties of copper, above all its extreme sensitivity to O-2 traces. A simple procedure has been developed for trapping O-2 in the cell and monitoring its absence electrochemically. (C) 2000 Elsevier Science B.V. All rights reserved.