1. Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel
2. LPI, Institut Chimie Physique, EPFL, CH-1015 Lausanne, Switzerland
3. Laboratoire d'Electrochimie (UMR 7575), F 75231 Paris Cedex, France
4. Department of Physics, Technion, Haifa 32000, Israel