Honestly, H2's got a long long way (if viable at all) to go as the future of clean cars. There is not much natural H2. In a way, H2 acts like a battery as well using electricity to produce from H2O, and discharge as electricity to H2O. Producing it cleanly, like with green power, isn't efficient yet – it's only around 70% efficient. Plus, getting H2 from the factory to the customer is way way pricier than just using our current electricity grid for charging stations... Converting it to electricity is only about ~30% efficient(?) It will cost a few times more than electricity in the foreseeable future. It will be definitely much harder than have charging stations everywhere.

Not to mention the technical challenges (assume we can handle) of the low volume density, low temperature..