Catalytic activity of Al-Cu-Fe-Ni-Cr high entropy alloy

TL;DR

This study demonstrates that Al-Cu-Fe-Ni-Cr high entropy alloy significantly improves MgH2 hydrogen storage by lowering desorption temperature, enhancing kinetics, and maintaining stability over multiple cycles.

Contribution

It introduces a novel HEA catalyst that markedly enhances MgH2 hydrogen storage performance and provides insights into its catalytic mechanism.

Findings

Desorption temperature lowered from 425°C to 180°C

Achieved 7.3 wt. % hydrogen absorption in 3 minutes

Maintained stability over 25 cycles with minimal fluctuation

Abstract

Magnesium hydride (MgH2) is a promising material for hydrogen storage because of its abundance and beneficial properties, such as high storage capacity and cost-effectiveness under mild conditions. Despite of these benefits, MgH2 unfavorable thermodynamics and kinetics make it difficult to use in real applications. In this work, the hydrogen storage properties of MgH2have been improved using Al-Cu-Fe-Ni-Cr high entropy alloy (HEA) based catalysts, which has been synthesized via mechanical alloying. The experimental findings show that the beginning desorption temperature of MgH2significantly lowered from 425{\deg}C to 180{\deg}C by adding 5 wt. % Al-Cu-Fe-Ni-Cr HEA in MgH2. Moreover, the catalyst shows enhanced kinetics, attaining 7.3 wt. % hydrogen absorption in 3 minutes at 320{\deg}C with 15 atm hydrogen pressure, and ~5 wt. % desorption in 6 minutes at 320{\deg}C. These results highlight, how much lower its desorption temperature is than those of other well-known catalysts. Over a span of 25 cycles, MgH2 catalyzed by Al-Cu-Fe-Ni-Cr HEA exhibits remarkable cyclic stability with negligible fluctuations (~ 0.05 wt. %).After a thorough characterization of the materials, a workable catalytic mechanism for HEA was proposed in light of the results.