Low-energy and accelerated hydrogen release from MgH2–5 wt% NaTiOxH catalyzed hydrogen storage reactor by graphite responsive microwave

Abstract

Owing to high thermal stability and large reaction enthalpy, MgH₂ has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process, which consumes lots of energy. To achieve hydrogen release with low energy consumption, accelerated reaction rate, and high heating uniformity, this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiO_xH catalyst. A multi-physics model of the 5 wt% NaTiO_xH catalyzed MgH₂ reactor integrated with a microwave generator is developed to investigate the reaction, heat and mass transfer process of hydrogen release. It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed, reduce the energy consumption by at least 10.71% and save the hydrogen release time by 53.49% compared with the traditional electric heating method. Moreover, the hydrogen desorption thermodynamics could be improved with the increase of microwave power. The hydrogen release time is shortened by 19.55% with the increase of 20 W microwave power. Meanwhile, it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt% have better heating performance. Therefore, it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH₂ hydrogen storage reactor.