Is there a complete list of all the half equations for $\ce{H2O2}$ - both oxidation and reduction, in acidic and alkaline conditions? I've looked on the internet but can't seem to find a list with all of them.

These are my first attempts:

  • $\ce{H2O2 + 2e^- -> 2OH^-}$ (in alkaline conditions)
  • $\ce{H2O2 + 2H^+ + 2e^- -> 2H2O}$ (in acidic conditions)
  • $\ce{H2O2 -> 2H^+ + O2 + 2e^-}$ (in acidic conditions)

Are these correct and are there any more?


1 Answer 1


From Proceedings of the Symposium on Oxygen Electrochemistry and Water Research 2002, 36 (1), 85-94:

$$ \begin{array}{lcc} \text{Formation}&:&~\ce{2H+ + O2 + 2e- &->& H2O2} &\quad E^0=\pu{0.440V} \text{ vs. SCE}\\ \text{Reduction}&:& ~\ce{H2O2 + 2H+ + 2e- &->& 2H2O} &\quad E^0=\pu{1.534V} \text{ vs. SCE}\\ \text{Direct water}&:& ~\ce{2H+ + 1/2O2 + 2e- &->& H2O}\\ \text{Decomposition}&:& ~\ce{H2O2 &->& H2O + 1/2 O2} \end{array}$$

($\text{SCE}$ stands for Saturated Calomel Electrode)

Another strange suggested reaction involves the anion $\ce{HO2-}$ (Abel E.: Über die Selbstzersetzung von Wasserstoffsuperoxyd. Monatshefte für Chemie 1952 83(2) 422–39.):

$$\text{Decomposition 2}:\ce{H2O2 + H2O- -> H2O + O2 + OH-}$$

At the cathode occur at the same time the hydrogen gas evolution:

$$\ce{2H+ + 2e- -> H2~} \qquad\qquad\phantom{00} E^0=\pu{0.242 V} \text{ vs. SCE}$$

Meanwhile, at the anode, oxygen gas is evolved:

$$~\ce{2H2O -> 4H+ + O2 + 4e-} \quad E^0=\pu{0.987V} \text{ vs. SCE}$$


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