[pfdietz]

Ammonia is synthesized using hydrogen gas. Yes, the final product is not hydrogen, but hydrogen is an essential feedstock.

All this pearl clutching about hydrogen embrittlement ignores that industry solved this problem a century or more ago. It's a consideration that must be taken into account when selecting materials, not some sort of all powerful showstopper.

To be clear, none of what I'm saying should be taken as an endorsement of hydrogen as a fuel for automobiles.

[pama]

I worked in materials science in the past. Although I dont recall all details, I have seen seen convincing presentations from researchers at the Weizman institute claiming strongly we are far from ready for a transition to a hydrogen economy, and I have seen no evidence or supporting studies since then arguing that we know how to introduce hydrogen cars to steel cities. We wont have ammonia synthesizers in every street of Manhattan, yet we have plenty of buildings that might start failing fast if people replaced their parked cars with hydrogen cars. I do think it would be cool if the structural part of the world was different and would allow for such cars to roam the streets, but the US is not loving rebuilding physical structures for the purpose of a new technology, so I think it will take a while, and a couple accidents to get things right at a slower pace. We might never need H-cars in the end.

[pfdietz]

Sure. But this isn't because of embrittlement, it's because of other issues: lower round trip efficiency than batteries, difficulty of storing hydrogen in a vehicle, and the cost of fuel cells.