1. Department of Inorganic Chemistry, Faculty of Science, P.J. Šafárik University, Moyzesova 11, Košice SK-041 54, Slovakia
2. Institute of Physics, P. J. Šafárik University, Park Angelinum 9, Košice SK-04154, Slovakia
3. Laboratory of Adsorption and Catalysis, University of Antwerp, Universiteitsplein 1, Wilrijk B-2610, Belgium
4. Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, Prague CZ-128 43, Czech Republic