A novel carbon-induced-porosity mechanism for improved cycling stability of magnesium hydride

Abstract

MgH₂ has been extensively studied as one of the most ideal solid hydrogen storage materials. Nevertheless, rapid capacity decay and sluggish hydrogen storage kinetics hamper its practical application. Herein, a Ni/C nano-catalyst doped MgH₂ (MgH₂Ni/C) shows an improved hydrogen absorption kinetics with largely reduced activation energy. Particularly, the MgH₂Ni/C displays remarkable cycling stability, which maintains a high capacity of 6.01 wt.% (98.8% of initial capacity) even after 50 full hydrogen ab/desorption cycles, while the undoped MgH₂ counterpart retains only 85.2% of its initial capacity. Detailed microstructure characterizations clearly reveal that particle sintering/growth accounts primarily for the deterioration of cycling performance of undoped MgH₂. By comparison, MgH₂Ni/C can maintain a stable particle size with a growing porous structure during long-term cycling, which effectively increases the specific surface of the particles. A novel carbon-induced-porosity stabilization mechanism is proposed, which can stabilize the proportion of rapid hydrogen absorption process, thus dominating the excellent cycling performance of MgH₂Ni/C. This study provides new insights into the cycling stability mechanism of carbon-containing Mg-based hydrogen storage materials, thus promoting their practical applications.