Note I am not trying to "double fuel efficiency" in a car or something scamey like that. My purpose is to fill balloons with hydrogen and possibly power an HHO torch (also make it safer because pure hydrogen or pure oxygen will not explode).

I found this https://www.thingiverse.com/thing:1200458 HHO generator someone made which seems perfect for my needs except that it outputs HHO together. I cannot find a design for actually useful HHO production that actually separates H2 and O (by useful I mean large volumes of gas, not just a science experiment).

My plan for alterations is to make that design thicker so that it can hold two arrays of plates and split it in halves. I would also add in separate nozzles for each side. I would then print both halves and glue them together with a metal plate (aluminum) in the middle. Would this work? I don't see why it would not however I have not seen a design like this which probably means that I'm wrong rather than everyone else :D

  • $\begingroup$ An electrolytic cell divided with an aluminum wall reminds me of an aircraft seen in the "Flight of the Phoenix" (the one they built from the wreckage, I mean). It did fly, but that's not what I would recommend to anyone, unless they are stranded in the desert with no hope of rescue. $\endgroup$ Apr 9, 2019 at 22:35

1 Answer 1


A cell with two electrodes separated from each other and an aluminum divider plate in the middle is really two cells: one has an aluminum plate as a cathode, and the other cell has the same aluminum plate as the anode.

In this situation, the solution does not directly connect the external anode and cathode; the aluminum divider separates the solution into two separate cells.

When you pass current (electrons) thru this arrangement, ions travel. Protons (or other cations) travel toward the negative electrode. In the cell attached to the external positive source, protons move away, and discharge at the aluminum. Simultaneously, protons in the adjacent cell move away from the aluminum and discharge at the stainless steel cathode. Hydroxyls (or other anions) do the reverse.

You will need twice the cell voltage to get a high current, and hydrogen will be evolved from the external cathode (-) and the farther side of the aluminum divider plate. Oxygen will be evolved from the other side of this aluminum plate and from the external anode (+).

Now make a small change: let the aluminum divider go from the top of your case to below the water line, say, halfway down. Then ions can travel thru the solution. This is now just one cell. Hydrogen will be evolved at the (one) cathode and oxygen will be evolved at the (one) anode. Your separation of the gas phase by the aluminum divider allows hydrogen to be collected separately from the oxygen. BTW, you might as well use stainless steel for this divider, since it is used for the electrodes.

When collecting the gasses, hydrogen will be evolved at twice the rate of oxygen. If you build up pressure, the cell will respond by pushing liquid from the cathode compartment into the anode compartment to equalize the pressure. You may have to use a check valve or some kind of flow equalizer to keep liquid from spurting out of one of the gas outlets.

  • $\begingroup$ Ahh I see. I actually planned to make the electrodes aluminum and use baking soda as electrolyte (lye would erode aluminum fast). I will revise design to have holes drilled in the center sheet near the bottom. I worry that some bubbles will still get fizz though. Does the size of the holes make a difference in efficiency? I assume it would perform as if the plates were spaced farther apart? Any suggestions for a design that would allow for high volume production of separate gasses? I did not think about the pressure difference although I did know that hydrogen was created 2x Oxygen. $\endgroup$
    – RootInit
    Apr 10, 2019 at 21:10

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