Nanoparticulate ZrNi: In Situ Disproportionation Effectively Enhances Hydrogen Cycling of MgH<sub>2</sub>
Lingchao Zhang, Xin Zhang, Wenxuan Zhang, Zhenguo Huang, Fang Fang, Juan Li, Limei Yang, Changdong Gu, Wenping Sun, Mingxia Gao, Hongge Pan, Yongfeng Liu
Abstract
High thermal stability and sluggish absorption/desorption kinetics are still important limitations for using magnesium hydride (MgH 2 ) as a solid-state hydrogen storage medium. One of the most effective solutions in improving hydrogen storage properties of MgH 2 is to introduce a suitable catalyst. Herein, a novel nanoparticulate ZrNi with 10–60 nm in size was successfully prepared by co-precipitation followed by a molten-salt reduction process. The 7 wt % nano-ZrNi-catalyzed MgH 2 composite desorbs 6.1 wt % hydrogen starting from ∼178 °C after activation, lowered by 99 °C relative to the pristine MgH 2 (∼277 °C). The dehydrided sample rapidly absorbs ∼5.5 wt % H 2 when operating at 150 °C for 8 min. The remarkably improved hydrogen storage properties are reasonably ascribed to the in situ formation of ZrH 2, ZrNi 2, and Mg 2 NiH 4 caused by the disproportionation reaction of nano-ZrNi during the first de-/hydrogenation cycle. These catalytic active species are uniformly dispersed in the MgH 2 matrix, thus creating a multielement, multiphase, and multivalent environment, which not only largely favors the breaking and rebonding of H–H bonds and the transfer of electrons between H – and Mg 2+ but also provides multiple hydrogen diffusion channels. These findings are of particularly scientific importance for the design and preparation of highly active catalysts for hydrogen storage in light-metal hydrides.