Um yeah don't use liquid oxygen. But oxygen dissolved or otherwise absorbed in a material is fair game. Even without anything fancy, water can contain about 1%

Um yeah don't use liquid oxygen. But oxygen dissolved or otherwise absorbed in a material is fair game. Even without anything fancy, water can contain about 1% free oxygen, which is 8x what you could do with gaseous oxygen (which is in turn 5x what atmospheric mixture has). And there are a lot of chemical reactions that can produce oxygen much better than 1%. The trick is going to be avoiding heat changes.