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I've been creating hydrogen via electrolysis of water, using pure nickel strips as electrodes, in a sodium hydroxide solution. (These nickel strips are commonly sold for use in battery packs).

I'm wary of using stainless steel as I have been advised that hazardous chemicals are released.

Graphite sticks corrode and make a mess.

I've recently heard of carbon fiber -- I mean the raw fiber sheets before they are infused with resin to make composite material.

I saw this patent, which seems to suggest that carbon fiber performs better than stainless steel. (However, the application is for HHO injection into automobile engines which in my view damages the credibility of the study.)

Is there a chemical reason that carbon fiber or any material should be more effective than another? I imagine for a constant voltage and electrolyte, the amount of gas created is mostly just a function of the current?

Could it be that carbon fiber is more effective because of the huge amount of surface area?

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  • $\begingroup$ In this case the likely cause is indeed the surface area. You could use a current meter to determine the current used by each of the configurations. $\endgroup$
    – Alan
    Apr 2 at 10:37
  • $\begingroup$ Given your sentence on current, I am wondering how you define efficiency? The amount of H2 and O2 being made per current or the amount of energy to make them? The former is called the Faradaic or Current efficiency, the latter is the energy efficiency. Using an active catalyst will require less potential for the same current increasing the energy efficiency, a selective catalyst will only form the wanted products increasing the faradaic efficiency. Your electrode material is essentially your catalyst. Please clarify which efficiency you mean. $\endgroup$
    – Noah
    Apr 2 at 14:54
  • $\begingroup$ By efficiency I meant amount of gas produced per watt of electricity. $\endgroup$ Apr 2 at 22:31

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Nickel, which you're using, is reasonably efficient (in having low resistance and not building up an electrically resistant oxide layer). Monel alloy (Cu-Ni) also works well. BTW, alkaline electrolyte, nickel (and iron) electrode batteries (nickel-iron cells) have seen continuous use for decades in mining, so with careful use, nickel should serve well.

Carbon, even graphite, tends to disintegrate, as you mention (I believe due to hydrogen intercalation)

In brine electrolysis, mercury was used, for example by Hooker Electrochemical Company, leading to tainted soil in Love Canal.

Platinum is one of the best materials for electrodes, but a bit out of reach for most. Pt might make more efficient use of electricity (due to catalytic effects possibly lowering over-voltage requirements), though I do not have any information on that. Platinum-plated titanium is available commercially.

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  • $\begingroup$ Can I ask, please, what tangible benefit could I attain by replacing nickel with platinum in my setup? $\endgroup$ Apr 1 at 21:29
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    $\begingroup$ @MadScientist, The opportunity to improve the economy! The mining industry and their subsidiaries will appreciate your investment. Or you could be cheap and just spend a nickel. Sorry, that's just my 5¢. $\endgroup$ Apr 1 at 21:47

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