The electromotive force (emf) of nanocrystalline silver (nano-Ag) vs. bulk Ag (micro-Ag) has been measured in a solid state electrochemical cell with RbAg4I5 as solid electrolyte, and thermodynamic and kinetic data have been extracted. The excess emf of nanocrystalline silver is evaluated as a function of time and temperature (333-413 K). It is quantified in terms of surface energy and curvature, and its transient is interpreted as an underlying relaxation process due to electrochemical Ostwald ripening. (C) 2004 Elsevier B.V. All rights reserved.