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Proton Conducting Oxide |
The goal of this project is to explore the microscopic dynamics of hydrogen ions in proton conducting oxide materials. Proton conduction is a
fundamental process that has attracted considerable attention based on important developments and applications in hydrogen energy
research;
therefore experimental characterization of transition rates and migration mechanisms is highly valuable. We employ an optical picosecond pump-probe technique that directly measures the vibrational lifetimes of hydrogen related defects. These measurements reveal that proton migration is
highly coupled to infrared photon absorption and suggest a means to enhance proton conduction in important device applications.
Important Results:
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>>Photon-Stimulated Hydrogen Transport in TiO2
In this study the vibrational lifetimes of the O-H and O-D stretch mode in rutile TiO2 show that the proton hops over the potential barrier between oxygen ions when a resonant IR photon is absorbed. The rutile sublattice (a) and potential energy surface (b) are shown in the above figure. Arrows indicate the migration pathway of the proton.
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The vibrational lifetimes, shown in the figure are found to be only a few picoseconds indicating that the hopping transport process is very efficient. The photonstimulated hopping rate is found to be approximately 1 THz at room temperature. In contrast, the thermal diffusion rate at room temperature is only 103 s-1, indicating a giant enhancement of 9 orders of magnitude! This photoenhanced hydregen transport effect is significant for potential.
Reference:
E. J. Spahr, L. Wen, M. Stavola, L. A. Boatner, L. C. Feldman, N. H. Tolk, G. Lüpke, Giant Enhancement of Hydrogen Transport in Rutile TiO2 at Low Temperatures, Phys. Rev. Lett. 104, (2010) 205901.
Funding: NSF, DoE, Jeffress Foundation
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