Researchers led by Andreas Stierle at the Deutsches Elektronen-Synchrotron (DESY) have laid the groundwork for an alternative method of hydrogen storage, using superlattices of iridium-seeded palladium nanoclusters with cluster diameters of 1.2 nanometers. The team, which also includes researchers from the universities of Cologne and Hamburg, published their findings in the journal ACS Nano.
The fact that palladium can absorb hydrogen like a sponge has been known for some time.
However, until now, re-extracting the hydrogen from the material has been a problem. That’s why we’re trying palladium particles that are only about a nanometer in diameter.
To ensure that the tiny particles are strong enough, they are stabilized by a core of iridium, a rare precious metal. In addition, they are fixed on a graphene support.
The palladium nanoparticles (green) are stabilized by an iridium core (red). Hydrogen can accumulate on their surface and can be released again by heating. Credit: DESY, Andreas Stierle
Attaching palladium particles to graphene at intervals of just two and a half nanometers results in a regular, periodic structure, said Stierle, who heads the DESY NanoLab.
DESY’s PETRA III X-ray source was used to observe what happens when palladium particles come into contact with hydrogen: essentially, the hydrogen sticks to the surfaces of the nanoparticles, with almost none penetrating inside .
To recover the stored hydrogen, it suffices to add a small amount of heat; the hydrogen is quickly released from the surface of the particles, because the gas molecules do not have to come out from inside the cluster.
Researchers want to know what stocking densities can be achieved using this new method, Stierle said. Challenges still need to be overcome before moving on to practical applications. For example, other forms of carbon structures might be a more suitable support than graphene – the researchers are considering using carbon sponges, which contain tiny pores. Substantial amounts of palladium nanoparticles should fit inside them.
D. Franz, U. Schröder, R. Shayduk, B. Arndt, H. Noei, V. Vonk, T. Michely, A. Stierle (2021) “Hydrogen Solubility and Atomic Structure of Graphene Supported Pd Nanoclusters”, ACS Nano doi:10.1021/acsnano.1c01997