Fig. 1: Redox changes during the OER catalysed by MnO₂.

a, Representative redox reactions associated with manganese ions. b, Redox processes on MnO₂ at potentials below 1.75 V vs. RHE in sulfuric acid^{7,8,9,10,11,12,21,22,23,24,25,26,27,28,29,30,31}. Under these conditions, Mn undergoes sequential oxidation from Mn²⁺ to Mn³⁺ and then Mn⁴⁺ during the OER cycle, but no Mn⁷⁺ is generated. c, Redox processes on MnO₂ at potentials above 1.75 V vs. RHE. Mn⁷⁺ is generated, resulting in irreversible catalyst dissolution^7,8,9,10. d, Target catalytic network of this study. Although MnO₄⁻ is formed during the OER, the charge comproportionation reaction between Mn⁷⁺ and Mn²⁺ forms Mn³⁺, which can be reincorporated into the OER cycle. CD, charge disproportionation; CC, charge comproportionation.