Enhanced hydrogen storage property of MgH2 caused by a BaCrO4 nanocatalyst.

ABSTRACT

Magnesium hydroxide (MgH2) 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 BaCrO4 nanocatalyst prepared via a wet chemistry method was added to MgH2 to achieve better kinetic and thermodynamic performances. Kinetic tests suggested that the onset hydrogen desorption temperature was decreased for milled MgH2 from 390 °C to below 280 °C after the introduction of a 5 wt% BaCrO4 nanocatalyst and the maximum dehydrogenation amount was up to 6.32 wt%. With regard to hydrogen absorption, MgH2 incorporated with 10 wt% BaCrO4 could fully absorb 5.78 wt% H2 within 10 min at 300 °C and recharge 3.1 wt% H2 at a low temperature of 250 °C. In comparison, the hydrogen uptake amounts for MgH2 under the same conditions were only 3.98 wt% and 1.52 wt%. With regard to hydrogen desorption, 5 wt% BaCrO4-modified MgH2 could discharge 4.25 wt% H2 within 10 min at 325 °C and 4.81 wt% H2 at 300 °C, while MgH2 could not dehydrogenate at 300 °C. Meanwhile, only 5% of the performance decayed for 5 wt% BaCrO4-modified MgH2 during ten cycles. Dehydrogenation E a reduced to 106.75 kJ mol-1 in contrast to 156.55 kJ mol-1 for MgH2. In addition, DFT results verified that the BaCrO4 nanocatalyst reduced the band gap from 2.78 eV to 2.16 eV to improve the thermodynamic property of MgH2 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 MgH2 hydrogen storage systems.