Perovskiet-like BaZrO3 nanocatalyst with rich oxygen vacancies on boosting hydrogen storage property of MgH2

Abstract

Magnesium hydride (MgH₂) as a promising solid hydrogen syorage material has been extensively researched. but the higher separating temperature and sluggish kinetics hinder its large-scale practical application. To solve this problem, a BaZrO₃ nanocatalyst with abundant oxygen vancies is manuscripted, exerts significant improvement to the hydrogen storage performance of MgH₂. Impressively, the onset dehydrogenation temperature of MgH₂-10 wt% BaZrO₃-O_v composite is reduced markedly from 390 °C(for pure MgH₂) to 260 °C. Additionally, the composite can discharge 4.22 wt% H₂ with 10 min at 275 °C and a total dehydrogenation amouut of 5.88 wt% is achieved at 300 °C. For hydrogen absorption, the composite can rapidly recharge hydrogen at a low temperature of 150 °C and approximately 5.08 wt% H₂ can be absorbed at 275 °C within 10 min. The dehydrogenation activation energy of BaZrO₃-O_v-added MgH₂ is as low as 92.61 kJ mol⁻¹ compared to pure MgH₂ (164.78 kJ mol⁻¹). Meantime, the composite presents unexceptionable reversible kinetic performance with a retention rate of 97.35 % after 10 cycles. The excellent catalytic effects can be attributed to the in-situ generation of ZrO₂-O_v, BaO-O_v and ZrH₂ from BaZrO₃-O_v during the first de-/rehydrogenation cycle, which function as nanosized active sites on MgH₂ matrix to accelerate electron transfer and provide abundant hydrogen diffusion channels. Density functional theory calculations results verify that the Mg–H length and dehydrogenation energy barrier are ameliorated through BaZrO₃-O_v. This work provides a unique perspective on modification MgH₂ by perovskiet-like BaZrO₃-O_v nanocatalyst.