| Santanu Chaudhuri, Nanocatalysis Group, Department of Chemistry & Center for Functional Nanomaterials, Brookhaven National Laboratory, Building 555, Upton, NY 11973, Ping Liu, Dept. Chemistry, Brookhaven National Laboratory, Upton, NY NY 11973, and James T. Muckerman, Chemistry Department, Brookhaven National Laboratory, Bldg. 555A, Upton, NY 11973. |
| NaAlH4 doped with ~2% titanium is a promising hydrogen storage material. Density Functional Theory using the RPBE functional can predict the role of Ti during the multi-step hydrogen absorption-desorption cycle. Two of the most probable mechanisms of Ti assisted hydrogen storage e.g. the replacement of Na by Ti on the surfaces and formation of a Ti-Al alloy, have been probed in this work. The energetics of the hydrogen absorption process indicates that the intermediate perovskite phase, Na3AlH6, is less reactive compared to the end product of the hydrogen desorption cycle, NaH and Al. The NaH surface doped with Ti (figure 1) has been found to promote exothermic dissociative absorption of molecular hydrogen. This explains why nanometric NaH doped with Ti is reported to be a good hydrogenation catalyst. The use of DFT in unraveling the myriad correlations between electronic structure, oxidation state, defects and hydrogen storage efficiency will be discussed. 
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