Abstract
We identify hydrogen-related point defects as a dominant defect species involved in (de)hydrogenation of sodium alanate, a viable hydrogen storage material. These defects are positively or negatively charged, and hence their formation energies are Fermi-level dependent—an important feature that has not been recognized in past studies. This dependence enables us to explain why small amounts of transition-metal additives drastically alter the kinetics of dehydrogenation. The rate-limiting step for hydrogen release is the creation of charged hydrogen-related defects, while transition-metal additives act as electrically active impurities that lower the formation energy of these defects.
- Received 24 September 2007
DOI:https://doi.org/10.1103/PhysRevB.76.214101
©2007 American Physical Society