Titanium-Impregnated Polymer Shows Promise as Top Hydrogen Storage Medium
A low-cost, high-capacity hydrogen-storage medium is essential for the commercialization of hydrogen fuel-cell technologies. Researchers had previously looked at carbon nanotubes, hydrogen-clathrate-hydrates and other nanostructured materials as ways of storing hydrogen, but they only work in fuel cells at low temperatures or high pressures. Now, Ihm and co-workers have shown that polymers covered with metal atoms can store a significant amount of hydrogen under more practical working conditions.
The large storage capacity is predicted because numerous hydrogen molecules are attracted to the metal atoms that lie along the polymer chain. Using a series of first-principles electronic-structure calculations, the physicists worked out how much energy the hydrogen molecules need to bind to the metal atoms. They looked at a wide combination of metal atoms (including titanium, scandium and vanadium), polymers (including polyacetylene, polypyrrole and polyaniline) and bonding sites for the hydrogen on the metal atoms.
The researchers found that a form of polyacetylene "decorated" with titanium atoms was the best. This molecule consists of a series of carbon atoms linked together in a chain by alternating single and double bonds. Each carbon atom has one hydrogen atom that can be replaced by a particular atom like titanium.
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