Long term cycling behavior of titanium doped NaAlH4 prepared through solvent mediated milling of NaH and Al with titanium dopant precursors

Abstract A simple and an efficient synthesis route, solvent mediated milling of NaH and Al with 2 mol% of the dopant precursor, Ti(OBu) 4 followed by hydrogenation, has been developed and employed to synthesize Ti-doped NaAlH 4 . The long-term hydrogenation and dehydrogenation, up to 100 cycles were carried out systematically. Reversibility of about 3.4 wt.% hydrogen release was obtained during the first dehydrogenation (160 °C) run after the initial hydrogenation of Ti-doped (NaH+Al) at 150 °C; ∼11.4 MPa H 2 for 12 h. In the subsequent cycles, the storage capacity increased, reaching an optimum of 4.0 wt.%. This capacity was retained for 40 cycles with the dehydrogenation kinetic curves showing remarkable reproducibility. Comparison of the X-ray diffraction profiles of Ti-doped (NaH+Al) from initial and final stages of the cycling study reveals a growing resistance to the hydrogenation of Na 3 AlH 6 to NaAlH 4 .

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