Improved the hydrogen sorption properties of MgH_2 by CeMnZr solid solution

摘要

Magnesium hydride (MgH_2) is one of the promising solid-state hydrogen storage materials because of its high capacity, abundant resource and excellent reversibility. However, the high dehydrogenation temperatures and sluggish kinetics restrict its practical application. It was found that doping catalysts could significantly improve the hydrogen storage properties of MgH_2. The solid solution Ce_(0.8)Mn_(0.1)Zr_(0.1)O_2 (denoted as CeMnZr) with abundant oxygen vacancy was synthesized and its catalytic influence on the hydrogen sorption properties of MgH_2 have been investigated. CeMnZr modified MgH_2 composite showed a reduced initial decomposition temperature, almost 62 K lower than the pristine MgH_2. At 473 K, MgH_2-CeMnZr composite had an absorption capacity of 4.08 wt% hydrogen within 3,500 s, which was about twice better than the pure MgH_2 at same condition. MgH_2-CeMnZr sample could desorb 2.56 wt% of H_2 within 3,500 s at 573 K compared to low desorption rate and 0.85 wt% H_2 by as-milled MgH_2. The activation energy (Ea) for CeMnZr codoped MgH_2 sample is about 50 kJ·mol~(-1) lower than the milled MgH_2. Based on the characteration analysis, the in-situ generated MgO and CeH_(2.51) species as well as abundant oxygen vacancy is believed to play synergistic catalytic effects in enhancing the hydrogen storage properties of MgH_2.