1 Department of Physical Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel. Department of Solar Energy and Environmental Physics, Swiss Institute for Dryland Environmental and Energy Research, J. Blaustein Institutes for Desert Research and Ilse, Katz Inst. of Nano-Science and Technology, Ben-Gurion University of the Negev Sede Boqer campus, Midreshet Ben-Gurion 8499000, Israel.