See https://www.nature.com/articles/s41561-024-01480-8 for the paper. It's quite short, and very much a geochemistry and/or geomicrobiology paper, so I am not the best person to really comment on it.
Now for a bit of ragging on the journal... The fact that this is in Nature Geoscience says a lot. I have an abysmally low opinion of that journal after seeing the first crop of papers published in it (it's fairly new). Lots of things that just didn't pass basic sanity checks of "is this physically plausible?". Hopefully it's improved... So far it's been "here's all the wacky crap that got rejected from Nature and couldn't be published in a reputable domain-specific journal".
Right now I treat it as a journal that has no clue how to pick peer reviewers. Therefore, stuff gets published that really shouldn't make it through peer review. While this _probably_ isn't one of those papers, I have trouble trusting Nature Geoscience to have picked relevant reviewers.
Despite having worked a lot on related topics, I don't know enough about deep marine ecosystems to really peel things back. With that said, we know there are plenty of different microorganisms that can produce oxygen in these circumstances. It seems odd to me to dismiss biological production immediately. Even if these samples were fully "poisoned" and that really did kill all microbes, why would electrolysis be the dominant source of oxygen for the entire ecosystem? Microbes are a lot easier to explain... But I am likely missing something critical there.
That's a key part of why I I'm focusing on the journal it's in. Based on previous publications, I have trouble trusting Nature Geoscience to have picked good peer reviewers on this. If it holds up, it should have been in Nature. I suspect it was rejected from Nature for some fairly fundamental reasons and then got through much lighter reivew in Nature Geoscience...
But I hope I'm wrong!
There are a lot of zany ideas that are unlikely but also aren't impossible. Those are pretty common and quite fun. Occasionally, they're correct. Much more frequently, they're not. But they make for a lot of interesting discussion and are incredibly important science. I hope this fits into that category.
I'm sorely tempted to ask a friend of mine who works on these exact types of microbes what she thinks of this... It'll make for an interesting discussion at least!