I've looked all over the place to find a way for me to separate water without needing to put in salt. What I've found is you can separate water into hydrogen and oxygen through electrolysis (which needs salt to make the water conductive), radiation (which I don't want to use - this is a house project that I want to get into), thermal (the water needs to be hotter than what I can provide), and photobiological (looks cool - but it looks like it won't produce much).
There's a lot of things out there for electrolysis water splitting, but every single one looks like it needs salt. Can I initially provide salt to a water splitting machine, then never refill it and still split water? Is there anything else, in which I could put in the water to make it split, and not have to ever refill said thing?
Really, I want to build the machine, and not have to keep providing resources that I'm going to have to get - just provide the machine water and electricity.