The CEO of Toyota is pushing internal combustion engines burning hydrogen as a carbon-neutral power source.
The other problem is it's pretty difficult to make a hydrogen ICE car - I mean it's not as if hydrogen FCEVs are easy *either* but hydrogen ICE introduces even more complexities.
To make an efficient one, you basically have the same problem efficient, powerful diesels have: NOx. So you won't be getting rid of adblue any time soon. 'tho I suppose you could produce the ammonia from excess hydrogen.
It's also even less efficient than hydrogen FCEV, because an ICE is just not that thermodynamically efficient. The best fuel cells are ca. 75-80% efficient, with a motor, maybe 60-70% of hydrogen goes to the wheels; an ICE is what, 33-40%? I am not sure how hydrogen changes that efficiency, but we also have to remember that a FCEV gets you "hybrid" for free, that is, regen braking, electric A/C, electric PS, and no ICE running under inefficient acceleration/coast profiles. Those usually only come if you then bolt an electric motor onto the side of an ICE engine, so you still need a small battery pack and inverter.
It's really hard to see what the Toyota CEO is thinking here - he's clearly betting on battery EVs being too expensive (despite the fact you can now get 50kWh battery cars like e-208 which aren't *that* much more expensive than their ICE counterpart) - but at the same time thinks that we're going to have massive amounts of hydrogen infrastructure and hydrogen fuel to throw about. Obviously, because we'd be throwing away 5x as much renewable energy per km travelled with hydrogen ICE than a battery EV.
I do see a strong future for hydrogen, but I think it will be in domestic/industrial heating, air travel, trucks and for trains where they are impractical to otherwise electrify. It just doesn't add up for passenger cars.