[freebeard]

Don't know, but the use of graphene to make hydrogen tanks might reduce losses.

I went looking for a reference, and found:

Scientists discover white graphene architecture with hydrogen storage potential
Boron nitride-based structure could be used for safe hydrogen storage to fuel vehicles

More generally:

Impermeability

Sheets of graphene have such closely knit carbon atoms that they can work like super-fine atomic nets, stopping other materials from getting through. That means graphene is useful for trapping and detecting gases—but it might also have promising applications holding gases (such as hydrogen) that leak relatively easily from conventional containers. One of the drawbacks of using hydrogen as a fuel (in electric cars) is the difficulty of storing it safely. Graphenes, potentially, could help to make fuel-cell cars running on hydrogen a more viable prospect.

Graphene - A simple introduction - Explain that Stuff