Reduced graphene oxide/patronite composite as highly active catalyst precursors for enhancing the hydrogen desorption of MgH2
Yanxia Liu, Chenxing Wang, Yan Song, Zhenglong Li, Xinqiang Wang, F. Z. Qi, Jian Chen, Yongfeng Liu, Mingxia Gao, Hongge Pan
Abstract
• The synergic catalytic effect of in-situ generated and uniformly scattered metallic V and MgS facilitates the improved hydrogen desorption of MgH 2 by introducing the rGO@VS 4 composite. • The MgH 2 –15 wt% rGO@VS 4 starts releasing hydrogen at 180 °C and peaks at 220 °C, which is 145 °C and 128 °C lower than that of the Pristine MgH 2 , respectively. • The MgH 2 –15 wt% rGO@VS 4 composite shows excellent cycling stability, of which reversible hydrogen storage capacity can stabilize at about 5.9 wt% with capacity retention of 98.2% at 300 °C for 100 cycles. Although MgH 2 is widely deemed to be the most promising solid-state hydrogen storage materials for the medium-high temperature fuel-cell applications expected in the near future, the high-temperature desorption and sluggish hydrogen absorption/desorption kinetics are the major challenges for its applications. Herein, reduced graphene oxide/patronite nanoparticle composite (rGO@VS 4 ) is successfully synthesized using an ionic liquid (IL)-assisted hydrothermal method, and superior catalytic effects originated from the rGO@VS 4 composite precursor towards the hydrogen storage reaction of MgH 2 are systematically investigated. The VS 4 reacts with MgH 2 leads to the in-situ formed and uniformly scattered of metallic V and MgS during both ball-milling and the initial hydrogen desorption, and the synergic catalytic effect of metallic V and MgS facilitates the improved hydrogen desorption of MgH 2 . The MgH 2 –15 wt% rGO@VS 4 composite starts releasing hydrogen at 180 °C and peaks at 220 °C, which is 145 °C and 128 °C lower than that of the Pristine MgH 2 , respectively. The energy required for H 2 desorption from MgH 2 is decreased to 63.8 kJ mol −1 , 58.9 kJ mol −1 lower than that of the Pristine MgH 2 . Furthermore, the MgH 2 –15 wt% rGO@VS 4 composite shows excellent cycling stability, of which reversible hydrogen capacity can stabilize at about 5.9 wt% with capacity retention of 98.2% at 300 °C for 100 cycles. This study provides a deeper insight into metallic V and MgS to enhance the hydrogen desorption of solid-state hydrogen storage materials and also offers a perspective for the construction of high-activity catalysts for solid-state hydrogen storage materials. The synergistic effect of the rGO, metallic V and MgS derived from highly active catalyst precursor enhance the hydrogen desorption of MgH 2 .