The use of hydrogen is very practical. It's already becoming a popular option in material handling because a tank can be swapped in a minute rather than charging a bunch of batteries and they can run all day indoors completely clean.
The production and logistics are the challenge.
- Free hydrogen (unbound to any other element) isn't all that common on earth. So you can't just harvest it from the air, it has to be taken from a compound (like H2O) and as previously stated breaking a hydrorgen particle off of a comound requires a good bit of energy.
- The conversion wont be 1 to 1 so there will be some energy loss.
- The molicules are so small they are incredibly difficult to seal so there will be a great deal of loss over time. To the extent that a hydrogen molicule can leak through the walls of a steel bottle over time. Not counting the seals and valves.
That sealing issue isn't a big deal for a small amount of production, but on the scale of a daily power source for 250 million people living 2000 miles away from the point of production... it's a lot.
I think local production of hydrogen for vehicles using clean energy sources could be a fantastic way to make clean, energy efficient vehicles. Far more so than electric cars and not much more dangerous than liquid gasoline.