| AVS 60th International Symposium and Exhibition | |
| Actinides and Rare Earths Focus Topic | Tuesday Sessions |
| Session AC+AS+EN-TuA |
| Session: | Actinides and Rare Earths: The Nuclear Fuel Cycle and Critical Materials |
| Presenter: | H. Idriss, SABIC, Saudi Arabia |
| Authors: | Y. Al Salik, SABIC, Saudi Arabia I. Al Shankiti, SABIC and University of Colorado H. Idriss, SABIC, Saudi Arabia |
| Correspondent: | Click to Email |
Thermal water splitting to hydrogen on reducible materials is one of the promising methods to secure renewable energy vectors for the future. the process relies on a redox cycle whereby steam is introduced to a prior reduced CeO2 to generate hydrogen which is consequently oxidized. However to achieve this cycle CeO2 needs be reduced at elevated temperatures (> 1500oC) [1, 2]. Mixing CeO2 with metal cations can lower the energy needed for the reduction process. Among the methods of changing CeO2 are the incorporation of metal cations smaller in size than Ce4+ cations such as Zr4+ [3] or the addition of a metal cation that can transfer electrons to Ce4+ [4, 5]. In this work we present a core and valence level study of the extent of reduction of Ce4+ cations by the addition of Fe and U cations. We compare XPS Ce3d, Ce4d of stoichiometric CeO2 to those of CexFe1-xO2 and CexU1-xO2 (x<1). We also investigate the reduction of these materials upon Ar ions sputtering. We find that the addition of Fe or U cations in any proportions increases the reduction of Ce4+ cations. In particular considerable enhancement of the reduction of CeO2 with Ar ions was noticed (compared to CeO2 alone) when x>0.5 in both CexFe1-xO2 and CexU1-xO2 series of the oxide materials. The reasons for the enhancement of CeO2 reduction by Fe cations can be linked to both size and electron transfer effect while in the case of U cations it is mainly due to electron transfer from the U5f to Ce4f levels. Tests for hydrogen production by thermal water splitting for both series were conducted and indicated the enhancement of the activity of the mixed oxide when compared to CeO2 alone.
[1] W.C. Chueh, C. Falter, M. Abbott, D. Scipio, P. Furler, S. M. Haile, A. Steinfeld, Science (2010) 330: 1797-1801.
[2] K-S Kang, C-H Kim, C-S Park, J-W Kim, J. Ind. Eng. Chem. (2007) 13: 657-663.
[3] S. Abanades, A. Legal, A. Cordier, G. Peraudeau, G. Flamant, A. Julbe, J Mater Sci (2010) 45:4163–4173.
[4] I. Al-Shankiti, F. Al-Otaibi, Y. Al-Salik, H. Idriss, Topics in Catalysis (2013) in press.
[5] B.E. Hanken, C.R. Stanek, N. Grønbech-Jensen, M. Asta, Phys. Rev. B (2011) 84: 085131-1 to 085131-9.