1. Institute of Aurel Stodola, Faculty of Electrical Engineering and Information Technology, University of Zilina, Univerzitna 8215/1, 010 26Zilina, Slovakia
2. Laboratory of Renewable Energy Science and Engineering, Ecole Polytechnique Fédérale de Lausanne, Station 9, CH-1015Lausanne, Switzerland
3. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California94720, United States