Use of an ionic liquid for storing hydrogen

A method of storing and releasing hydrogen within a borohydride/borate system, the method comprising:

• providing a first ionic liquid as a homogeneous aqueous solution, the first ionic liquid comprising a borohydride anion with releasable hydrogen and a cation;
• releasing hydrogen out of the first ionic liquid by contacting the homogenous aqueous solution with a catalyst, the release of hydrogen from the first ionic liquid forming a second ionic liquid including a borate anion and the cation from the first ionic liquid in a second homogeneous aqueous solution;
• regenerating the first ionic liquid by treating the second ionic liquid with an amount of borohydride salt to form an aqueous mixture comprising the regenerated first ionic liquid and a borate salt, wherein:
• the first ionic liquid and the second ionic liquid are both water miscible;
• (ii) adding a phase separation inducer to the aqueous mixture to induce separation of the first ionic liquid as a separate phase from the aqueous mixture, the phase separation inducer including a salt which coordinates to the water in the aqueous mixture and does not react with the borohydride, wherein the phase separation inducer is selected from the group consisting of hydroxide salt, carbonate salt, chloride salt, sulfate salt, phosphate salt, carboxylate salt, an amount of borate salt in addition to the borate salt formed when regenerating the first ionic liquid, an amount of borohydride salt in addition to the borohydride salt used to regenerate the first ionic liquid, and combinations thereof;
• and
• separating the regenerated first ionic liquid from the borate salt and the phase separation inducer.

A method of storing and releasing hydrogen within a borohydride/borate system, the method comprising:

• providing a first ionic liquid as a homogeneous aqueous solution, the first ionic liquid comprising a borohydride anion with releasable hydrogen and a cation;
• releasing hydrogen out of the first ionic liquid by contacting the homogenous aqueous solution with a catalyst, the release of hydrogen from the first ionic liquid forming a second ionic liquid including a borate anion and the cation from the first ionic liquid in a second homogeneous aqueous solution;
• regenerating the first ionic liquid by treating the second ionic liquid with an amount of regenerative borohydride salt to form an aqueous mixture comprising the regenerated first ionic liquid and a borate salt, wherein:
• the first ionic liquid and the second ionic liquid are both water miscible;
• and
• adding a phase separation inducer, in addition to the amount of regenerative borohydride salt used to regenerate the first ionic liquid, to the aqueous mixture to induce separation of the first ionic liquid as a separate phase from the aqueous mixture,
• wherein the regenerated first ionic liquid further comprises inorganic borohydride to an extent that the first regenerated ionic liquid remains water miscible and the second ionic liquid after the release of hydrogen from the first ionic liquid, remains water miscible and are present within the aqueous mixture.