An innovative approach could transform nanoparticles into simple hydrogen storage tanks. Highly volatile gas is seen as a promising energy carrier for the future, which could provide climate-friendly fuels for airplanes, ships and trucks, for example, as well as enable environmentally friendly steel and cement production. climate – depending on how hydrogen gas is generated. However, the storage of hydrogen is expensive: either the gas must be kept in pressurized tanks, up to 700 bar, or it must be liquefied, that is, cooled to minus 253 degrees. Celsius. Both procedures consume additional energy.

A team led by DESYAndreas Stierle laid the groundwork for an alternative method: storing hydrogen in tiny nanoparticles made of palladium, a precious metal, with a diameter of just 1.2 nanometers. It has been known for some time that palladium can absorb hydrogen like a sponge. “However, until now there has been a problem with extracting the hydrogen from the material again,” says Stierle. “That’s why we’re trying palladium particles that are only about a nanometer in diameter. A nanometer is a millionth of a millimeter.

To ensure that the tiny particles are strong enough, they are stabilized by a core made of iridium, a rare precious metal. In addition, they are attached to a graphene support, an extremely thin layer of carbon. “We are able to attach particles of palladium to graphene at intervals of only two and a half nanometers,” reports Stierle, who heads DESY NanoLab. “The result is a regular and periodic structure. The team, which also includes researchers from the universities of Cologne and Hamburg, published their findings in the journal American Chemical Society (ACS) ACS Nano.

DESY’s PETRA III X-ray source was used to observe what happens when the palladium particles come into contact with hydrogen: Essentially, hydrogen adheres to the surface of the nanoparticles, almost none of them penetrate the interior. Nanoparticles can be represented as chocolates: an iridium nut in the center, wrapped in a layer of palladium, rather than marzipan, and coated in chocolate on the outside with hydrogen. To recover the stored hydrogen, just add a small amount of heat; hydrogen is quickly released from the particle surface because gas molecules do not have to exit from inside the cluster.

“Then we want to know what storage densities can be achieved using this new method,” says Stierle. However, there are still some challenges to be overcome before moving on to practical applications. For example, other forms of carbon structures might be a more suitable support than graphene – experts are considering using carbon sponges, containing tiny pores. Substantial amounts of palladium nanoparticles are expected to fit inside them.

Reference: “Hydrogen Solubility and Atomic Structure of Graphene Supported Pd Nanoclusters” by Dirk Franz, Ulrike Schröder, Roman Shayduk, Björn Arndt, Heshmat Noei, Vedran Vonk, Thomas Michely and Andreas Stierle, October 11, 2021, ACS Nano.
DOI: 10.1021 / acsnano.1c01997