Reactivity enhancement of oxide skins in reversible Ti-doped NaAlH{sub 4}
- Laboratory for Hydrogen and Energy, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland)
- Laboratory for Nanoscale Materials Science, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland)
The reversibility of hydrogen sorption in complex hydrides has only been shown unambiguously for NaAlH{sub 4} doped with transition metal compounds. Despite a multitude of investigations of the effect of the added catalyst on the hydrogen sorption kinetics of NaAlH{sub 4}, the mechanism of catalysis remains elusive so far. Following the decomposition of TiCl{sub 3}-doped NaAlH{sub 4} by in-situ X-ray photoelectron spectroscopy (XPS), we link the chemical state of the dopant with those of the hydride and decomposition products. Titanium and aluminium change their oxidation states during cycling. The change of the formal oxidation state of Al from III to zero is partly due to the chemical reaction from NaAlH{sub 4} to Al. Furthermore, aluminium oxide is formed (Al{sub 2}O{sub 3}), which coexists with titanium oxide (Ti{sub 2}O{sub 3}). The interplay of metallic and oxidized Ti with the oxide skin might explain the effectiveness of Ti and similar dopants (Ce, Zr…)
- OSTI ID:
- 22420209
- Journal Information:
- AIP Advances, Journal Name: AIP Advances Journal Issue: 12 Vol. 4; ISSN AAIDBI; ISSN 2158-3226
- Country of Publication:
- United States
- Language:
- English
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