Hydrogen can be stored as acid

Hydrogen gas holds promise as a carbon-free fuel, but is difficult to store and transport because it is highly flammable, diffuse and has a low energy density. Jonathan Hull at Brookhaven National Laboratory in New York and his colleagues have found a possible way to store hydrogen as an aqueous solution of formic acid (HCOOH), which has a higher energy density.

At ambient temperature and pressure, an iridium catalyst dissolved in water causes H₂ to react with carbon dioxide to form the acid under mildly basic conditions. Acidifying the solution triggers the release of pure pressurized H₂ gas. Because of the mild conditions needed for the reactions, the work could eventually lead to a mechanism for H₂ storage.

Nature Chem. 10.1038/nchem.1295 (2012)