[marcosdumay]

I don't think any hydrogen vehicle in actual use has a fuel cell (and if there's any, it's an incredibly rare exception). They are all internal combustion engines.

Proton exchange membranes are very unreliable and expensive. They are also not power-dense, one that powers a bus will be very large.

[ch_sm]

It‘s actually the opposite: some hydrogen cars that use combustion exist, but they are really, really rare. Almost all hydrogen cars that are road legal use a fuel cell in combination with BEV parts to smooth out/extend power delivery.

[pipodeclown]

That is completely incorrect, it is the opposite.