Hydrogen doesn't seem viable to me, this video does a pretty good job explaining why:
Basically the cheapest way to produce hydrogen is to process natural gas, which consumes a lot of energy and produces greenhouse gases. You can create hydrogen from water cleanly via electrolysis but that consumes even more energy. Then you have to transfer the hydrogen around and store and pressurize it (which requires energy), as cars need the hydrogen to be at 700 bar in order to hold enough hydrogen to have a viable range...and then the conversion of the hydrogen in the fuel cell to generate electricity is itself also a fairly inefficient process.
If you wanted the cleanest possible outcome, you'd start with renewable electricity and you'd lose a large chunk of that energy converting it into hydrogen and back vs. just charging a battery.
I think hydrogen fuel cells could still find a niche, that video suggests it could find a role in aviation (where the added weight of a battery would be more of a problem) and I think there might be a niche for it for trucking, but they are currently not a very good option for consumer vehicles. In fact, right now,
the main supplier of hydrogen to the Los Angeles area is having problems and so now it has been 2-3 weeks with spotty hydrogen availability. I bet all those people who leased Mirais and Clarities for the free hydrogen are not too happy about this.
