I'm trying to learn more about fuel cells, and a question came across my mind. Before I ask, I once read that a fuel cell is not the reversal of an electrolytic reaction, and vise versa. Can someone please elaborate in the following question? Anyway, If I had two containers, both enclosed (pressure is out of the question), one with a mixture of hydrogen and oxygen (the infamous "HHO" mixture as they call it, for a lack of a better term), and the other simply with water containing the proper electrolytes for the reaction to take place, is it possible to essentially make a reverse reaction by submerging electrodes in each of the containers? In the perfect system taking place in my mind, I imagine the water would convert to HHO while the HHO in the other container would convert into water with perfect efficiency, but it would obviously be far less than perfect, that is, if it would even work. If so, are there any examples? If not, I would like to know what's preventing the reaction from taking place.