The Perseron Stamsa robot, which landed on Mars some time ago, succeeded in breaking down carbon dioxide on Mars to produce about 5g of oxygen.
This is enough for an astronaut to breathe for about 10 minutes, and it produced oxygen from the gold box in the second picture of a toaster-sized device called MOXIE built into the rover.
I didn’t see how long it took to make 5g.
Photo, sources: BBC official Instagram