Enhanced hydrogen storage properties of MgH2 catalyzed by TiVCrFeNi high entropy alloy

Abstract

MgH₂ has a high theoretical hydrogen storage capacity (7.6 wt.%) and cost advantages, but its high hydrogen absorption and desorption temperatures, as well as its slow kinetic performance, seriously restrict its practical application. In this study, a TiVCrFeNi high entropy alloy (HEA) catalyst was prepared using a powder metallurgy process, and a high-energy ball milling process successfully synthesized MgH₂-x wt.% TiVCrFeNi (x = 3, 5, 7, 10) composites. The catalytic mechanism of TiVCrFeNi HEA with FCC phase structure on the hydrogen storage performance of MgH₂ was studied. The synergistic effect of multivalent transition metal elements in HEA produces a 'cocktail' effect, which effectively optimizes the hydrogen absorption and desorption reaction path of MgH₂. Among them, the MgH₂-5 wt.% TiVCrFeNi composite exhibits the best comprehensive hydrogen storage performance. Compared to ball-milled MgH₂, the dehydrogenation activation energy of the composite is significantly reduced to 71.49 kJ/mol H₂ (a decrease of 42.4%), and the initial hydrogen desorption temperature is reduced to 455 K (an 80 K reduction). This study provides an effective strategy for utilizing high-entropy alloys to catalytically enhance the hydrogen storage properties MgH₂.