Two-dimensional transition metal-based high-entropy oxide nanoplates for enhanced hydrogen storage of LiBH4

LiBH 4 , with its ultrahigh hydrogen capacity of 18.5 wt%, is regarded as a promising solid-state hydrogen storage material; however, its high thermodynamic stability and sluggish kinetics severely hinder practical application. In this study, two-dimensional Co-based high-entropy metal oxide nanoplates, (CoNiMnFeCr) 3 O 4 (HEO), were synthesized as catalysts to enhance the hydrogen storage performance of LiBH 4 . Benefiting from the unique multicomponent synergy and abundant oxygen vacancies generated by lattice distortions, HEO significantly lowers the dehydrogenation temperature of LiBH 4 . Specifically, in the case of LiBH 4 catalyzed by 30 wt% HEO, the onset and peak hydrogen release temperatures decrease to 100.0 °C and 364.8 °C, respectively—reductions of 175 °C and 130 °C compared with pristine LiBH 4 . The decomposition fractions of LiBH 4 before 250 °C and 400 °C increase from 2 % and 16 % (without catalyst) to 29 % and 61 %, respectively. Moreover, the catalytic effect of HEO surpasses that of mixed metal oxides and single-component Co-based oxides in reducing the dehydrogenation temperature of LiBH 4 . The dehydrogenation activation energy of LiBH 4 is reduced by 37.37 kJ mol −1 H 2 , enabling complete hydrogen desorption within 1 h at 380 °C, demonstrating excellent dehydrogenation kinetics. During the first two cycles, Co B-like high-entropy borides are formed in-situ on the surface of HEO through reaction with LiBH 4 , which effectively prevents further hydrogen capacity loss and catalyzes subsequent H 2 absorption/desorption cycles. After 10 cycles, the reversible H 2 capacity of LiBH 4 under the catalysis of HEO stabilizes at 6.38 wt%, corresponding to a capacity retention of 66.7 %.