How about hydrogen from water? Yeah, you need high amounts of electricity to get it, but, as one example, if it's used in ICE engines, isn't that significantly cleaner than petrol? And a lot less damaging than making lithium batteries? Once burned, wouldn't it just react with oxygen to then form water vapour? And then, if it's making water, that's a self-sufficient cycle?

I feel like hydrogen can potentially be a very good solution, but the technology needs to catch up massively. I mean, scientists are getting to on nuclear fusion reactors, and their yield seems a lot better than everything else. Even fission reactors.

Also, I had this thought the other day, and yes, it's extremely futuristic, with the right people in charge thought, but mining gas planets for the hydrogen. We'll more than likely never inhabit those ones or use them for much, so we might as well use them for something, at least. At least before Dyson swarms become a thing.