Chou model was used to investigate the dehydriding reaction kinetic mechanism of MgH_2-Nb_2O_5 hydrogen storage materials at 573 K.A new conception,'characteristic absorption/desorption time(t_c)'was introduced to characterize the reaction rate The fitting results show that for the hydrogen desorbing mechanism,the surface penetration is the rate-controlling step.The mechanism remains the same even when the original panicle size of Nb_2O_5 is before ball milling(BM) or when the BM time changes And t_c indicates that the desorption rate of MgH_2-Nb_2O_5 will be faster than that of MgH_2-Nb_2O_5 by BM.The dehydriding reaction rate of MgH_2-Nb_2O_5(micro particle) BMed for 50 h is 4.76 times faster than that of the MgH_2-Nb_2O_5(micro panicle) BMed for 0.25 h,while the dehydriding reaction rate of MgH_2-Nb_2O_5(nano particle) BMed for 50 h is only 1.18 times as that of the MgH2-Nb_2O_5 (nano particle) BMed for 0.25 h.The dehydriding reaction rate of the BMed MgH_2-Nb_2O_5(nano particle) is 1-9 times faster than that of the BMed MgH_2-Nb_2O_5(micro particle).
