The Haber–Weiss cycle consists of the following two reactions:
H2O2 + OH→ H2O + O2− + H+ and
H2O2 + O2− → O2 + OH− + OH.
The second reaction achieved notoriety as a possible source of hydroxyl radicals. However, it has a negligible rate constant. It is believed that iron(III) complexes can catalyse this reaction: first, Fe(III) is reduced by superoxide, followed by oxidation by dihydrogen peroxide.