Hydrogen desorption kinetics of CeCl3-doped sodium aluminum hydride compacts measured by parallel in situ FTIR-ATR-spectroscopy and gravimetry

In this work, in situ FTIR-ATR-spectroscopy and gravimetry were used in parallel to determine the dehydrogenation reaction kinetics of 2 mol% CeCl3-doped NaAlH4 compacts. Dehydrogenation measurements were performed under isothermal and isobaric conditions at different temperatures. Subsequently spectroscopic and gravimetric data were fitted by Johnson-Mehl-Avrami and Arrhenius equation to obtain the rate constants of the dehydrogenation and activation energy of the NaAlH4-Na3AlH6 phase change. On the one hand the measurements showed that cycling of the powder compacts enhances the dehydrogenation reaction kinetics of the NaAlH4 phase, whereby a decrease of the activation energy by 3.4 kJ/mol was measured. On the other hand an influence on the calibration of the spectroscopic signal to the mass of desorbed hydrogen was observed.