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.