Yup that would be the sticking point with electrolysis, unless they could find some sort of cheap catalytic method to produce it requiring much less energy inputted into the separation process. I still say nuclear fusion is the way to go, and think more should be spent investigating that.
Take it from a (former) chemist: Catalysts can change the kinetics (rate) of a reaction, but they can’t change the thermodynamics. Energy in will (at best!) equal energy out, no matter how you do it.