Tailoring magnesium based materials for hydrogen storage through synthesis: Current state of the art

Effective solutions for the storage of energy are paramount to enable the transition toward decarbonized energy systems relying on widely abundant and recyclable resources. In this context, the use of hydrogen as the universal clean energy vector has always appeared as a prominent solution. The attraction for hydrogen resides in its high energy density, versatile means of production, and flexible end-use. Hydrogen can be utilised across a range of stationary and portable applications but the Holy Grail remains the development of high-density hydride materials for use in vehicles. In particular, magnesium and its hydride compounds provide a safe and efficient way to store hydrogen with high density; however these hydrides suffer from significant drawbacks in terms of kinetics and operating temperatures for hydrogen uptake/release. The properties of hydride materials can be tailored to meet set targets for practical operation, but this strongly depends upon the very early stages of the synthetic approaches utilised and their effectiveness in leading to the desired performances. Herein, with a special focus on magnesium based materials and the current understanding of their interaction with hydrogen, the various synthetic methods developed so far are reviewed and compared with the aim of guiding future developments toward practical hydrogen storage materials. The review is then extended to complex hydrides of magnesium with potentially more favourable thermodynamics.