Ti K-edge x-ray absorption near edge spectroscopy (XANES) was used to explore the Ti valence and coordination in Ti-activated sodium alanate. An empirical relationship was established between the Ti valence and the Ti K-edge onset based on a set of standards. This relationship was used to estimate oxidation states of the titanium catalyst in 2 mol% and 4 mol% Ti-doped NaAlH4. These results demonstrate that the formal titanium valence is zero in doped sodium alanate and nearly invariant during hydrogen cycling. A qualitative comparison of the edge fine structure suggests that the Ti is present on the surface in the form of amorphous TiAl3.
@article{arxiv.cond-mat/0404363,
title = {X-ray absorption study of Ti-activated sodium aluminum hydride},
author = {J. Graetz and A. Y. Ignatov and T. A. Tyson and J. J. Reilly and J. Johnson},
journal= {arXiv preprint arXiv:cond-mat/0404363},
year = {2009}
}