If the goal is reducing CO2 emissions, then electricity will be used to break H2 from water. Currently most H2 is extracted from natural gas, which produces CO2 as a by-product. That is, H2 needs to be used as a chemical energy storage mechanism for low-carbon energy sources such as solar, wind, or (ick) nuclear.
Problem with this is that the round trip efficiency of electricity to H2 and back is around 30%. If you use the H2 in a combustion system then you might get 35-40% efficiency. LiION batteries are around 90%.
So once you solve the materials handling problems with H2 you are still left with a very expensive energy storage mechanism.
Of course, Lithium is a limited resource so we are going to need more storage mechanisms anyway, but pronouncing H2 as the future is misleading at best.