Hydrogen generation from Nd-Ni-Mg system by hydrolysis reaction
Résumé
The generation of hydrogen from both the new NdNiMg15 ternary compound and the 1Nd - 1Ni - 15Mg mixtures (using NdH2.6 or NdCl3 as Nd precursors) by hydrolysis reaction were investigated. The Nd-Ni-Mg mixtures were prepared by ball milling process (for 1, 3 and 5 h) and the hydrolysis reaction was carried out in a 3.5 wt % NaCl solution (i.e. seawater). Independently of the composition, Nd-Ni-Mg mixtures show better hydrolysis performance compared with NdNiMg15 compound. The best hydrolysis performances were achieved with the mixtures 1NdH2.6 - 1Ni - 15Mg + 15 wt % NaCl and 1NdCl3 - 1Ni - 15Mg mixtures milled for 3 h. A 100% of theoretical hydrogen yield was obtained in 3 and 4 min respectively. The presence of chloride salts such as NaCl or NdCl3 during ball milling improves significantly the hydrolysis performance due to its ball milling and electrolyte properties. The activation energies of best mixtures, with and without adding salts (NdH2.6-Ni-15Mg (1 h BM) and NdH2.6-Ni-15Mg + 15 wt % NaCl (3 h BM)), were calculated using Avramie Erofeev model. A lower activation energy (24 kJ/mol < 31 kJ/mol) was found for NdH2.6-Ni-15Mg + 15 wt % NaCl (3 h BM) mixture, which demonstrates the beneficial effect of adding NaCl during ball milling.