Presentation on theme: "Interaction of hydrogen with a LaB 6 (111) surface Advisor: Prof. Michael Trenary Jenna Cameli."— Presentation transcript:
Interaction of hydrogen with a LaB 6 (111) surface Advisor: Prof. Michael Trenary Jenna Cameli
Objective There is critical need for the development of an alternative energy source to fossil fuel. A hydrogen based economy presents a feasible alternative. To achieve this, a suitable material for hydrogen storage has to be found. Metal hydrides are one of the most promising materials for hydrogen storage. In order to make hydrogen storage, and by extension a hydrogen economy a reality, basic research on metal hydrides is necessary.
Why Lanthanum hexaboride (LaB 6 )? Boron hydrides have high weight percentages which come close to the DOE target of 9% for a suitable material for hydrogen storage. It has been shown that CaB 6 can be hydrogenated to give Ca(BH 4 ) 2. LaB 6 has the same structure as CaB 6. We assume LaB 6 to interact with hydrogen in a similar manner.
Introduction- Lanthanum hexaboride (LaB 6 ) A refractory ceramic material with a m.p. = 2210 ºC. Insoluble in water. Stable in vacuum. Principal use is in hot cathodes. Also used in electron microscopes, microwave tubes, electron lithography, x-ray tubes and electron beam welding.
Appearance and structure – LaB 6 Unit cell of LaB 6
Experimental Outline 1) Design and install a hydrogen atom source. 2) Use RAIRS (Reflection Absorption Infrared Spectroscopy) to find out if B-H bonds are formed. 3) Use XPS (X-ray Photoelectron Spectroscopy) to monitor elements present on surface.. 4) Use LEED (Low Energy Electron Diffraction) for structure determination of the surface.
Experimental Apparatus Ultra-High Vacuum (UHV); Pressure: 4.0 x 10 -11 torr Viewport XPS LEED IR Detector IR Spectrometer
Structure of LaB 6 (111) Top view Side view T. Yorisaki, A. Tillekaratne, Q. Ge, C. Oshima, S. Otani, M. Trenary. Surface Science. Submitted.
LEED Pattern of LaB 6 (111) After annealing to 1363 K
XPS before Annealing
XPS After Annealing
Summary XPS and LEED used to examine sample surface RAIRS used to identify B-H bonds No B-H bonds seen under any tested conditions Possible reasons for lack of B-H bonds: – –tungsten blocking boron sites thus preventing hydrogen from reacting – –a lower temperature is required for B-H bond formation
Acknowledgements Thanks to Dr. Trenary and Aashani Tillekaratne for guidance throughout the program and to Dr. Takoudis, Dr. Jurisch, and Qian Tao for all their hard work in organizing the program. Special thanks to the NSF and DOD for financial support from grant EEC-NSF Grant # 0755115 and the NSF for grant CMMI-NSF Grant # 0925425