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I was trying to use a $500~\mathrm V$ AC power supply to split water, but nothing happened. I tested everything with a $9~\mathrm V$ battery, and it all worked fine.

Why did it not work with the high voltage? (Do not worry, I was taking the proper precautions, such as insulation and three pairs of gloves, and I did not touch any live wires.)

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    $\begingroup$ Why in the name of all that is good and sensible are you trying to split water at $500~\mathrm V$??? That is a preposterously high voltage for the purpose. $\endgroup$
    – hBy2Py
    Nov 20, 2016 at 12:16
  • $\begingroup$ No duplicate, but related: chemistry.stackexchange.com/questions/8642/… $\endgroup$ Nov 21, 2016 at 7:15

1 Answer 1

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Alternating current (AC) is your problem. AC spends half its time pushing electrons forward through the circuit, and half the time pushing them in reverse through the circuit. Thus, on average the net current pushed through the cell is zero.

So, leaving aside any metal dissolution/deposition, you were forming tiny, tiny amounts of electrolysis gases at the surface of your electrodes while there was current moving through the cell in one direction, but immediately consuming them again when the current reversed. The total number of coulombs passed in each direction was presumably so small that no gas bubble nucleation occurred before the polarity reversed.

Regardless: stop using 500 V for electrochemistry experiments. It's way more potential than you need, and terrifically unsafe. In most cases, anything above 40 V is overkill, and for most experiments that 9 V battery you mentioned will more than suffice.

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    $\begingroup$ It has been quite a while since this answer was posted, but I must point out that products are formed with AC electrolysis but mixed, at least if you just use your mains supply(50Hz) (pro: easy to test). The mix is explosive (incase of water electrolysis), but it is formed $\endgroup$ Apr 6, 2020 at 16:22
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    $\begingroup$ @VaradMahashabde Agreed! When I was a kid, I built a simple carbon arc contraption in my basement chemistry lab. I controlled the current using a saltwater rheostat: a jar of saltwater with copper wires stuck in the saltwater. I used 120 V AC line voltage. The carbon arc was blindingly bright, the fuses kept blowing until I got the salt concentration right and chlorine gas was released. I know that smell very well: it is how I was introduced to chemistry and became a chemist. $\endgroup$
    – Ed V
    Feb 19, 2022 at 13:29

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