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I am currently conducting an electrolysis experiment using a 30 amp power supply with a voltage ranging from 10 to 16 volts.I am thinking of using potassium sulfate (K2SO4) dissolved in water as an electrolyte. I am using graphite rods as the electrodes. My primary goal is to produce hydrogen and oxygen gases through the electrolysis process. However, before proceeding further, I would like to clarify a few points:

-Is potassium sulfate a suitable pH-neutral electrolyte for my intended purpose of producing only hydrogen and oxygen gases?

-Will the electrolysis of potassium sulfate generate any harmful byproducts that I should be aware of?

-Are there any specific considerations or precautions I should keep in mind while using graphite rods as the electrodes with potassium sulfate electrolyte?

I appreciate any insights, suggestions, or relevant information that can help me optimize my experiment and ensure the safe and efficient production of hydrogen and oxygen gases. Thank you!

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3 Answers 3

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As peroxosulfates/peroxodisulfates ($\ce{SO5^2-}$, $\ce{S2O8^2-}$) are assumed to be created roughly at $U \ge \pu{2.4 V}$, do not raise the applied voltage above $2.0 - 2.1 \pu{V}$.

To increase the passing current during the experiment design stage, do not increase the voltage but improve the geometry of the electrolytic cell to minimize internal resistance. Increase electrode surfaces, decrease the electrode distance(s), increase (reasonably) electrolyte concentration.

Note that, aside of unwanted side reactions, applying too high voltage leads to excessive Ohmic heat loses and overall low energy efficiency, if that is important parameter for your case.

And last but not least, evaluate all aspects of possible danger and danger precautions, while manipulating/storing hydrogen. At no circumstances mix it with air nor even oxygen. The only exception is small volume of few dozen milliliters max for explosion demonstration purposes, avoiding brittle materials like glass or ceramics.

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  • $\begingroup$ Aren't those values you listed for sulfate oxidation products versus SHE (it's always best to relate the voltage to a reference in these cases because it is very system dependent otherwise)? The cell voltage is not a good measure to determine the potential at the anode side. There will be losses on the cathode and throughout the solutions (the latter will probably be the biggest contributing factor). I do agree that this experiment is dangerous, definitely not something someone should just do in their backyard when they have to pose the question about the electrolyte. $\endgroup$
    – Noah
    Commented Jun 12, 2023 at 9:34
  • $\begingroup$ Well, the SP of H2/H2O at pH 7 is about -0.4 V wrt SHE, for peroxodisulphate is it near + 2.0 V. Sure Ohmic loses and eventual overvoltages add. The suggested limit of applied voltage was just ballpark number guidance. For one time experiemnt, it is not that much important nor dangerous to have some peroxodisulphate present. $\endgroup$
    – Poutnik
    Commented Jun 12, 2023 at 9:38
  • $\begingroup$ 10-16 V is too high. There is needed much lower voltage with high enough current supply. $\endgroup$
    – Poutnik
    Commented Jun 12, 2023 at 11:02
  • $\begingroup$ Any can be used, but what you want may not be the same as what you get. About 8 V will be wasted on heat, so about 4/5 of the power. You can use it for boiling eggs if left ON for long enough. $\endgroup$
    – Poutnik
    Commented Jun 12, 2023 at 12:26
  • $\begingroup$ So if I use 10 volt it will not create byproducts and only waste it’s energy as heat? $\endgroup$
    – Noah
    Commented Jun 12, 2023 at 12:27
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Potassium sulfate is a good electrolyte for electrolytic purposes. The only risk is the production of persulfates as secondary product at the anode if the current is too high. The intensity of the current depends on the surface of the anode. Apart from this, nothing disagreeable will occur. Graphite electrode can do the job of course, but you should know that they will progressively be corroded by the electrolysis and graphite powder will slowly be produced to fall down the solution. The only parameter to check is the temperature. With a 30 Am power supply, the temperature of the solution will quickly increase. It should not make it boil.

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Use a screw thats conductive with alot of surface area.. if you have some change to spare.. this is what I would do.. buy a 1 once bar of silver and coat the screw in it.. silver is the most conductive element on the periodic table.. once done you cant really improve unless you wanna pay a fortune for precision machine work to improve on a fine threaded screw.Electrolyte wise, Sodium sulfate would be good, or if you got the resources or know how silver sulfate.. or sodium acetate, tho many just use salt lol.. dont know why you chose the one you did. but.. I assume availability and price, but graphite rods dont seem like a cheaper option lol unless you just were aware of surface area of the electrodes being a bottle neck. a rod does not have good surface area at all.. at all.. lol it just lasts longer. Next thing I would do tho im not aware of its efficiency increase is I would lower the temperature of your electrolyte solution. Lower temperatures equal less resistance in metals.. Im not positive but assume the same is true universally to a point. So you could go about that several ways. Interestingly this is not the part of the reaction where I had questions when I was gathering an compressing oxy-hydrogen, My questions were on the compression side. An the release as fuel. Just remember going forward.. silver then copper for all things electrical. Silver isnt too ludicrous.. its much more expensive then 8 years ago when i loaded up on pounds of it.. but.. still.. its underpriced.. the market is rigged and flooded with paper silver.. dont invest in silver you dont earn is another pointer.. bc eventually your gonna find out.. you dont own silver, you own an IOU lol.

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    $\begingroup$ There are plenty of errors in your post. Silver is a really bad catalyst for HER, for the OER I'm not sure, but Nickel is a commonly used, better and cheaper metal (although not stable in acidic solutions). Table salt will generate chloride which is dangerous. Higher temperatures are typically more efficient as the rates of all processes but the electronic conductivity rise with temperature and the latter is almost never a bottle neck. In general, your response is lacking a lot of structure and is wrong in many ways. I advise you to research more about the topic if you're interested of course! $\endgroup$
    – Noah
    Commented Jun 13, 2023 at 15:22

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