Direct synthesis and dehydrogenation properties of NaAlH_4 catalyzed with ball-milled Ti–B
【摘要】：Ball-milled Ti–B-doped sodium aluminum hydride was directly synthesized via mechanical ball-milling of a NaH/Al mixture. The mixture was completely hydrogenated to NaAlH_4 after 70 h under hydrogen pressure of 1 MPa. And higher hydrogen pressure is beneficial for the conversion from NaH/Al mixture to NaAlH_4. The dehydrogenation properties of the as-synthesized Ti–Bdoped sodium aluminum were systematically investigated.The result shows that ball-milled Ti–B has a remarkable catalytic effect on the enhanced dehydrogenation properties of NaAlH_4. As-synthesized Ti–B-doped NaAlH_4 sample releases hydrogen at the temperature of about 100 ℃. Approximately 4.15 wt% H_2 is released from ballmilled Ti–B-doped NaAlH_4 at 233.7 ℃. Even at 110 ℃, it also releases about 2.83 wt% hydrogen. The apparent activation energy(E_a) for the first step is estimated to be 83.97 k J·mol~(-1) using Arrhenius equation. Thus, utilization of ball-milled Ti–B as catalyst would substantially enhance the practical applications of NaAlH_4 for hydrogen storage.