Full disclosure, I'm just a high school chem student, but I've got this question and I couldn't find the answer anywhere online. I was reading an article about some futuristic "artificial gill", which kinda sounds like BS to me, but it got me thinking about this.
We were just learning in class about electrochemistry, and we just did electrolysis, so I was just thinking, instead of filtering the water, what if they used electrolysis to produce O2 gas? There would still be hurdles, like diluting the 100% O2 to about 20% gas by volume, storing the necessary electric power to drive the reaction, and making sure that the unit wouldn't blow up, but could it theoretically work if we could overcome these other issues?
Basically, could you produce enough O2 gas to survive, through the electrolysis of H2O, in a unit small enough for a man to use?