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Catalyst doping is a critical approach to improve the kinetics of MgH2. However, reported activation energy ( E a ) values of catalyzed MgH2 systems show a large discrepancy. This study investigates the effect of the driving force on E a for (de)hydrogenation reactions. The kinetic rate constant is calculated using Johnson-Mehl-Avrami-Kolomogorov (JMAK) model. E a is obtained according to a series of kinetic measurements under a nearly constant driving force. Under a low driving force ( P I n / P e q = 1.5 ) , the E a for dehydrogenation and hydrogenation are calculated to be 102.3 ± 5.0 and 41.6 ± 7.5 kJ/mol H2, respectively. Under a high driving force ( P I n / P e q = 10 ) , the E a for dehydrogenation and hydrogenation are calculated to be 101.4 ± 25.8 and 57.4 ± 5.0 kJ/mol H2, respectively. The result shows that the high driving force leads to higher hydrogenation E a over the E a obtained the low driving force, while dehydrogenation E a remains unchanged under different driving forces. |
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