1. Department of Chemical Engineering, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Department of Experimental Sciences, University Pablo de Olavide, Ctra. Utrera km 1. 41013 Sevilla, Spain, Condensed Matter and Interfaces, Utrecht University, Utrecht University, P. O. Box 80.000, 3508 TA Utrecht, The Netherlands, and ChevronTexaco, Energy Technology Company, Chevron Way 100, Richmond, California 94802-0627