Enhanced hydrogen storage property of MgH caused by a BaCrO nanocatalyst.

Magnesium hydroxide (MgH) has a broad application prospect in solid hydrogen storage, but the associated higher dehydrogenation temperature and undesirable cycling capacity limit its large-scale application. In this study, a BaCrO nanocatalyst prepared a wet chemistry method was added to MgH to achieve better kinetic and thermodynamic performances. Kinetic tests suggested that the onset hydrogen desorption temperature was decreased for milled MgH from 390 °C to below 280 °C after the introduction of a 5 wt% BaCrO nanocatalyst and the maximum dehydrogenation amount was up to 6.32 wt%. With regard to hydrogen absorption, MgH incorporated with 10 wt% BaCrO could fully absorb 5.78 wt% H within 10 min at 300 °C and recharge 3.1 wt% H at a low temperature of 250 °C. In comparison, the hydrogen uptake amounts for MgH under the same conditions were only 3.98 wt% and 1.52 wt%. With regard to hydrogen desorption, 5 wt% BaCrO-modified MgH could discharge 4.25 wt% H within 10 min at 325 °C and 4.81 wt% H at 300 °C, while MgH could not dehydrogenate at 300 °C. Meanwhile, only 5% of the performance decayed for 5 wt% BaCrO-modified MgH during ten cycles. Dehydrogenation reduced to 106.75 kJ mol in contrast to 156.55 kJ mol for MgH. In addition, DFT results verified that the BaCrO nanocatalyst reduced the band gap from 2.78 eV to 2.16 eV to improve the thermodynamic property of MgH and contributed to the decrease in the dehydrogenation energy barrier from 2.27 eV to 1.54 eV. This work provides an insight into the performance of ternary transition metal nanocatalysts for MgH hydrogen storage systems.