A novel hydrogen clathrate hydrate that forms at room temperature and relatively low pressure is a potential solution for the storage and transportation of hydrogen, the most environmentally friendly fuel.
Ice is a highly complex substance with multiple polymorphic modifications that keep growing in number as scientists make discoveries, explains a statement.
In their new study, chemists from the United States, China, and Russia focused on hydrogen hydrates. If stored in its natural form, hydrogen poses an explosion hazard, whereas density is way too low even in compressed hydrogen. That is why scientists are looking for cost-effective hydrogen storage solutions.
“Our new paper describes hydrates that contain less hydrogen but can exist at much lower pressures,” Skoltech professor Artem R. Oganov says in the statement.
The crystal structure of hydrogen hydrates strongly depends on pressure. At low pressures, it has large cavities which, according to Oganov, resemble Chinese lanterns, each accommodating hydrogen molecules. As pressure increases, the structure becomes denser, with more hydrogen molecules packed into the crystal structure, although their degrees of freedom become significantly fewer.
The scientists performed experiments to study the properties of various hydrogen hydrates and discovered an unusual hydrate with 3 water molecules per hydrogen molecule. They then used the USPEX evolutionary algorithm developed by Oganov and his students to puzzle out the compound’s structure responsible for its peculiar behavior.
The researchers simulated the experiment’s conditions and found a new structure very similar to the known proton-ordered C1 hydrate but differing from C1 in water molecule orientations. The team showed that proton disorder should occur at room temperature, thus explaining the X-ray diffraction and Raman spectrum data obtained in the experiment.
Photo credit: Tim Geers, flickr/Creative Commons