1. International Research Center for Renewable Energy; State Key Laboratory of Multiphase Flow in Power Engineering; Xi'an Jiaotong University, Xi'an, Shaanxi; 710049 China
2. Department of Inorganic Chemistry; University of Cologne; Greinstr. 6 50939 Cologne Germany
3. Ohio Aerospace Institute (OAI); NASA Glenn Research Center; Cleveland OH 44135 USA.