Potentiometrical investigations of nanocrystalline copper

Various samples of nanocrystalline copper have been investigated as electro des in acid CuSO4 solutions, with the objective of examining growth and rel axation processes by studying the time dependence of the potential E. Durin g the dissolution of Cu2O the disproportionation of Cu+ ions and the format ion of nanocrystalline copper was detected in the E(t) curve. A simple mode l for estimating the surface relaxation according to the Gibbs-Wulff theore m 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 relax ation then interferes with crystal growing. In agreement with these results , no separate time region of relaxation could be found for the E(t) of nano crystalline copper. It was shown that the accurate measurement of electrode potentials of copper requires attention to the specific electrochemical pr operties of copper, above all its extreme sensitivity to O-2 traces. A simp le procedure has been developed for trapping O-2 in the cell and monitoring its absence electrochemically. (C) 2000 Elsevier Science B.V. All rights r eserved.