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A method that is used by space-confining NaAlH 4 into the as-synthesized ordered mesoporous silica (OMS) is presented in the present work. NaAlH 4 in the pores of OMS is obtained by impregnation and drying techniques. It has been found that the space-confined NaAlH 4 in the pores of OMS shows the lower temperature and faster kinetics for dehydrogenation than that of the pristine NaAlH 4 . Moreover, in the absence of a catalyst, the rehydrogenation in a dehydrogenated NaAlH 4 system with nanoscale particles and phases can be achieved even with the temperatures of 125−150 °C and the hydrogen pressures of 3.5−5.5 MPa. The physical limitation of the NaAlH 4 particles, as well as the resulting Al and NaH phases, to be nanoscale in size by the pores of OMS is believed to be responsible for these.
Zheng et al. (Wed,) studied this question.