| Hydrogen energy would be the most promising form of clean energy because it is most likely the only true clean burning fuel for its oxidation product:water. And hydrogen storage is proving to be one of the most important issues for the implementation of hydrogen economy. The sodium alane hydrid NaAlH4 is so far the most investigated and promising hydrogen storage material, at least on a short time scale.In this study, NaAlH4 has been homogeneously mixed with nano TiO2 powders or amporous aluminum oxide by high-energy ball milling. The dehydrogenation reaction properties have been investigated by DSC/TG analysis and hydrogen storage performance test at 180℃for 5000s. The hydrogen desorption of 2.5 mol％Al2O3 together with different molar ratio of TiO2 were also studied.The result shows that NaAlH4 does not decompose during the Ball milling process. The two stages of decomposition reaction shifted to a lower temperature after ball milling, respectively from 300℃to 252℃, and 378.6℃to 369.3℃But it will take an extremely long period to complete the dehydrogenation reaction for the milled samples. The formation of amorphous NaAlH4 was also detected by XRD.Nano TiO2 powder improved the hydrogen capacity of NaAlH4, from 3.427 to 4.378 wt%, and decreased the temperature of the first stage decomposition reaction by from 300℃to 210℃. For amporous A12O3 as the modification reagent, thermodaynamic stabilities of NaAlH4 are dramatically drowned, resulting a decrease in the temperature by 115℃at which the first decomposition takes place.The influences of ball milling time and the ratio of the TiO2 addition were also studied. The hydrogen capacity decreases with longer ball milling time and more TiO2 additives.The first decomposition reaction of co-modified NaAlH4 begins at185℃when tested by the DSC/TG. The hydrogen desorption capacity of 2.5 mol% Al2O3 modified NaAlH4 and added with 3mol% TiO2 increases 23% from that of commercial NaAlH4, which is up to 4.22.wt.％. |
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