Palladium nanoneedle structures enhance hydrogen transfer efficiency in magnesium-based storage systems

A team of researchers at the University of Milan has developed a new method to speed up the hydrogenation and dehydrogenation of magnesium nanoparticles that could significantly improve the efficiency of hydrogen storage and support easier scaling up the technology.

Magnesium is a promising material for storing hydrogen thanks to its low weight, high natural abundance, non-toxicity and ability to adsorb high hydrogen content – up to 7.6 wt % forming magnesium hydride. While MgH₂ stability is good for storage, hydrogen release is endothermic process at almost 283 °C at 1 bar of pressure. This is an obstacle to scaling up magnesium-based storage.

The researchers investigated the potential for lower hydrogen desorption temperatures when using nanostructured magnesium, with promising early results. Nanostructured materials are those for which a single unit, which could be a cluster, crystal or molecule, measures between 1 and 100 nanometres. The weaker hydrogen bonding within the magnesium lattice allows for a lower desorption temperature.

Hydrogenation of Mg is normally a slow process that could be improved by structuring magnesium as nanoparticles. Nanoparticles increase active surface area, but at the same time increase the risk of oxidizing in the open air creating a layer of MgO, which affects the hydrogenation process. To eliminate oxidizing nanoparticles layer was covered by protective film of SiNx. But protective layer also prevents direct hydrogenation, so another way has to be created или it is necessary to create another way for hydrogen to easily reach the magnesium.

Palladium has excellent oxidizing stability as well as the ability to catalytically dissociate H2 molecules into H atoms and support their rapid diffusion into its lattice. In this work, a palladium layer was used to transfer hydrogen towards the magnesium nanoparticles sandwiched between palladium bottom layer and silicon nitride cover. Using this approach, a thicker magnesium nanoparticle layer leads to slower hydrogenation of the uppermost nanoparticle layers in the layer. The new idea proposed by researcher’s team to solve this problem is use so-called palladium nanoneedles which can function, in the authors’ terminology, as “highways”, supporting the faster diffusion of hydrogen atoms to the magnesium nanoparticles further from the plane of intersection between the palladium and magnesium layers.

The new nanoneedle structure represents a simple and affordable method for hydrogenation and dehydrogenation of magnesium nanoparticles, offering greater coverage and speed compared with a flat palladium layer. This represents a possible solution to a pre-existing bottleneck in magnesium-based hydrogen storage systems. The study is currently at the proof-of-concept stage, and there is therefore vast potential for performance improvements based on changes to experiment design and configurations, as well as the introduction of other materials.

Hydrogen energy is a relatively new field in renewable energy, with significant potential to provide emissions-free power for heavy vehicles such as trucks, ships and even aeroplanes. Hydrogen fuel cells also have the potential to revolutionise energy storage, reducing dependency on electrical grids, supporting load balancing, and storing excess electricity generated through other renewable technologies such as solar and wind. Palladium is a crucial metal in green hydrogen power generation thanks to its catalytic properties, high selectivity and hydrogen absorption.
The report, authored by Katrina E. Schieck, Luca Pedicone, Stefnia Crespi and Marcel Di Vece, was published in the March 2025 edition of the Journal of Materials Science.

Source: researchgate.net