1. Department of Physics and Fribourg Center for Nanomaterials, Fribourg University, Fribourg, Switzerland; Department of Chemical Engineering, University of Washington, Seattle, Washington 98195-1750; Helsinki University of Technology, Espoo, Finland; Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Station 6, CH-1015 Lausanne, Switzerland; and Néstlé Research Center, Vers-Chez-Les-Blanc, 1000 Lausanne 26, Switzerland