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Electrolysis occurs when a non-spontaneous redox reaction occurs when electrical energy is put into it. An electrochemical cell functions by using two redox reactions to facilitate movement of electrons. So for an alkaline battery, the zinc anode will oxidize and release electrons, which will flow through the circuit to reach the manganese ($\ce{MnO2}$) cathode, which will be reduced, allowing more electrons to flow through the circuit without buildup of electric charge. I assume here that both reactions are spontaneous, and the electron buildup in the anode prevents further zinc oxidation when the circuit is incomplete. $$\ce{Zn(s) + 2OH- (aq) \rightarrow ZnO(s) + H2O(l) +2e-} [E^\theta= 1.28V]$$ $$\ce{2MnO2(s) + H2O(l) + 2e- \rightarrow Mn2O3(s) +2OH- (aq)}\ [E^\theta= 0.15V]$$

If the alkaline battery is linked to an electrolytic cell, won't it just be like two electrochemical cells working in conjunction to each other? The zinc anode will be linked to the cathode of the electrolytic cell, and then the ensuing redox reaction will (probably) be spontaneous. So the "electrical energy" put into the electrolytic cell will be instead chemical energy?

Also, seeing that the $\ce{MnO2}$ cathode has a relatively small $E^\theta$ value, won't it be hard to trigger oxidation of the electrolytic anode? When connected to the electrolytic cell, do the cathode and anode of the electrochemical cell now work totally independently? If that is the case, the voltage of the battery should not be considered, but instead the electrode potentials of the anode and cathode, but that is usually not the case. What am I misunderstanding about this?

edit: I'm asking about the mechanism when an electrochemical cell is linked to an electrolytic cell, not about the reactions taking place in the electrochemical cell itself, so the question suggested doesn't quite fit the bill.

edit 2: Added a picture to better show my doubts. If the galvanic cell is linked to an electrolytic one as shown here, the galvanic anode and the electrolytic cathode are linked and seemingly acts as a separate cell. The same thing can be said about the other two electrodes. If this is the case, doesn't the galvanic anode and cathode each act independently of one another, and therefore the electrode potential of the individual half cell must be considered? If they are actually linked, how?

galvanic linked to electrolytic

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    $\begingroup$ related: Reaction in Zinc-Carbon-Ammonium Chloride battery $\endgroup$
    – cngzz1
    Jan 2, 2021 at 7:24
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    $\begingroup$ It is not clear to me just what you mean by linking an electrochemical cell to an electrolytic cell. For example, you can use a 9 V battery to electrolyze a salt water solution. In fact, aspects of this are a common query here. Perhaps you could edit down to what you really want to ask about and a picture is worth a thousand words, as they say. $\endgroup$
    – Ed V
    Jan 2, 2021 at 14:45

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For an electrolytic cell, a galvanic cell is nothing else but a power source.

For a galvanic cell, an electrolytic cell is nothing else but a powered electronic circuit.

The galvanic cell anode/cathode does not form with the electrolytic cell cathode/anode a respective separate cell, as there is no ionic flow between them. Similarly for a simpler case, 2 half cells do not form a cell if there is no ionic connection between them.

The reason for it is simple, based on the electrostatic neutrality requirement and enormous forces between unbalanced charges. Imagine you managed to push the current 1 A for 20 s through the wire, without being balanced by ionic motion. The comparable unbalanced charge causes in atmosphere a lightning several kilometres long.

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  • $\begingroup$ I think I'm catching your drift now! So for the image above, since there isn't a salt bridge or something of the sort, for each electron used to reduce a cation in the electrolytic cell, an electron is produced by oxidation of an anion, as to maintain neutrality of charge. Am I getting this right? $\endgroup$
    – chematwork
    Jan 5, 2021 at 16:08
  • $\begingroup$ Therefore, the galvanic cell as a whole is used to drive electrons into the electrolytic anode and out the electrolytic cathode. Makes much more sense if that's the case! $\endgroup$
    – chematwork
    Jan 5, 2021 at 16:09
  • $\begingroup$ Like that You can consider the galvanic cell as a water pump and the electrolytic cell as the piping system. But there is circulation of charge,instead of water. $\endgroup$
    – Poutnik
    Jan 5, 2021 at 16:12
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    $\begingroup$ If there were charge disbalance, it would very quickly build an electrostatic potential acting against the charge flow leading to such a disbalance, and the current would cease. $\endgroup$
    – Poutnik
    Jan 5, 2021 at 16:20
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You seem to be mixing a couple of things. One important clarification regarding

Also, seeing that the MnO2 cathode has a relatively small E$^o$ value, won't it be hard to trigger oxidation of the electrolytic anode? When connected to the electrolytic cell, do the cathode and anode of the electrochemical cell now work totally independently?

The listed electrode potentials are valid only in relatively dilute solutions under very specific conditions. Don't apply the half cells on a dry cell or an alkaline cell. In short, those numbers are not meaningful for an alkaline battery or a carbon-zinc dry cell. Those commercial cell compositions is just a magical mixture, which is more art than science. Battery technology is not that trivial. Think why there are not many types of batteries despite 300 years of research?

If you consider a galvanic cell such as your alkaline battery as a simple water pump, then a lot of your confusions will go away. Its only job is to "circulate" the electrons. When you connect a galvanic cell to an electrolytic cell, the anode and cathodes can no longer be considered independent. If the galvanic cell pumps out one electron, the electron has to travel the cathode, anode and the external circuit of the electrolytic cell. In that process, something in the electrolytic cell has to chemically decompose!

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  • $\begingroup$ So what I understand about this is that alkaline cells cannot be thought of as just a simple anode and cathode, and are more than the sum of its parts. Also, kinda dumb question; for linking a galvanic cell to a electrolytic one, you mentioned that the electron travels from the cathode to the anode. If you can detail this process a bit more, I would be very grateful. $\endgroup$
    – chematwork
    Jan 3, 2021 at 6:32
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    $\begingroup$ Check this answer chemistry.stackexchange.com/questions/144334/… $\endgroup$
    – AChem
    Jan 3, 2021 at 6:36
  • $\begingroup$ Electron current always travels from anode to cathode whether it is a galvanic cell or electrolytic cell. There is no dumb question. $\endgroup$
    – AChem
    Jan 3, 2021 at 6:38
  • $\begingroup$ I have another doubt, sorry to bother. I have pinned a picture onto the post, which supposedly shows a galvanic cell linked to an electrolytic cell. The way this is set up is as if the anode of the galvanic cell and the cathode of the electrolytic cell act as a separate cell altogether, same goes with the other two electrodes. If what you said is true and the electrons travel a full circuit (galvanic anode to galvanic cathode), how are the cells linked? $\endgroup$
    – chematwork
    Jan 5, 2021 at 9:20

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