Аннотация:The influence of electrolyte composition on the kinetics of electrocatalytic reactions was discussed in the seminal works of Frumkin. However, recent findings have reignited interest in the role of cations and pH in electrocatalysis, particularly in alkaline environments. Manganese oxides have attracted much attention as catalysts for both oxygen reduction and oxygen evolution reactions. In addition, some Mn oxides are promising materials for supercapacitors due to their high pseudocapacitance. In this work, we combine electrochemical measurements with microkinetic modeling to unveil the influence of pH and cation concentration on the interfacial recharging behavior of α-MnOOH, α-Mn2O3, and LaMnO3. Titration experiments revealed that the isoelectric point of manganese oxides is around 5, indicating that they are negatively charged in alkaline environments. Cyclic voltammetry showed that both OH− and Na+ concentrations influence the Mn(III)/Mn(IV) redox transition at the oxide-electrolyte interface, with distinct behaviors for α-MnOOH, α-Mn2O3, and LaMnO3. It is noteworthy that α-MnOOH exhibits two types of interfacial redox centers, protonated and cationic, which emphasize that the redox behavior is determined by ion-exchange equilibria
