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Hydrogen has amazing potential as an energy-dense and clean-burning fuel source but unfortunately, it is very volatile meaning it must be kept at a low temperature or high pressure at all times otherwise it will quickly melt and evaporate away, causing corrosion to its environment, and/or presents an explosion hazard. The challenges and expenses are insurmountable when dealing with hydrogen, so coming up with a solution for making hydrogen usable as a fuel source for the masses without excess risk is no simple task. However, recent developments from DESY (Deutsches Elektronen-Synchrotron) located in Hamburg, Germany seems to suggest Palladium-infused nano-chocolates as a cheaper mechanism to store hydrogen at ambient temperature and pressure (see Fig 1 & 3). They are called nano-chocolates because their shape resembles a box of classic fancy chocolate, but are actually iridium-seeded palladium nanocluster superlattices with graphene (a carbon structure) and iridium bases as support. Normally hydrogen would be absorbed by pure palladium, making it difficult to access due to the octahedral form they make (see Fig. 4), But due to the iridium core, the space for hydrogen to absorb into is filled, making it so that palladium can only adsorb the hydrogen onto its surface (see Fig 3).When hydrogen comes into contact with the palladium, it forms a bond with little to no polarity due to the extremely similar electronegativity values between Pd_s (2.2) and H_g (2.1) resulting in an extremely low when bonded (see Fig 5) i.e. a nonpolar bond. Without an iridium center of the nanostructure, this normally forms Palladium Hydride (PdH_x) which is a metallic palladium crystal that contains a substantial quantity of hydrogen within its crystal lattice (note, number of H is unknown because value varies with reaction conditions).

Unlike fossil fuels, the combustion of hydrogen does not generate carbon dioxide (CO₂), but only water vapor. Nano-chocolates could provide climate-friendly fuels for airplanes, ships, and many other vehicles, as well as facilitate clean steel and cement production as only a small amount of heat is needed for desorption (release of hydrogen from nano-chocolates). Emissions from complete and incomplete combustion systems like gasoline and diesel vehicles, are a major source of air pollution. By contrast, hydrogen-powered fuel cells emit none of these harmful substancesonly water (H₂O) and warm air.

Question for Discussion

With all of the benefits nano-chocolates present, there is still ongoing research being made for alternate models that could adsorb even more hydrogen. For example DESY are looking into using carbon sponges instead of graphene as a support because carbon sponges have small pores that can absorb significant levels of palladium nanoparticles allowing for more hydrogen to be stored in a given volume. Do you think that scientists should work to mass produce the nano-chocolate technology now, or focus their efforts on researching better and more efficient models like the carbon sponges?