High Entropy Alloy Catalytic Action on MgH2 Hydrogen Storage Materials

TL;DR

This study demonstrates that a high-entropy alloy catalyst significantly enhances the hydrogen storage and release kinetics of MgH2, reducing desorption temperature and maintaining capacity over multiple cycles.

Contribution

The paper introduces a novel HEA catalyst that improves MgH2 hydrogen storage performance, showing significant kinetic enhancements and stability over repeated cycles.

Findings

Desorption temperature reduced from 376°C to 338°C with HEA catalyst.

MgH2 absorbs 6.1 wt% hydrogen in 2 minutes at 300°C.

Storage capacity degrades negligibly after 25 cycles.

Abstract

Magnesium hydride (MgH2) is the mostly used material for solid-state hydrogen storage. However, their slow kinetics and highly unfavorable thermodynamics make them unsuitable for the practical applications. The current study describes the unusual catalytic action of a new class of catalyst, a high-entropy alloy (HEA) of Al20Cr16Mn16Fe16Co16Ni16, on the de/re-hydrogenation properties of MgH2. The onset desorption temperature of MgH2 is reduced significantly from 376 {\deg}C (for pristine MgH2) to 338 degC when it is catalyzed with a HEA-based catalyst. On the other hand, a fast de/re-hydrogenation kinetics of MgH2 was observed during the addition of HEA-based catalyst. It ab sorbs 6.1 wt% of hydrogen in just 2 minutes at a temperature of 300 degC under 10 atm hydrogen pressure and desorbs ~ 5.4 wt% within 40 minutes. At moderate temperatures and low pressure, the HEA-based catalyst reduced desorption temperatures and improved re-hydrogenation kinetics. Even after 25 cycles of de/re-hydrogenation, the storage capacity of MgH2 catalyzed with the leached version of HEA degrades negligibly.