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X-ray absorption study of Ti-activated sodium aluminum hydride

2004; American Institute of Physics; Volume: 85; Issue: 3 Linguagem: Inglês

10.1063/1.1773614

1520-8842

Jason Graetz, J.J. Reilly, John R. Johnson, Alexander Ignatov, Trevor A. Tyson,

Ammonia Synthesis and Nitrogen Reduction

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.