The anion effect on the oxygen reduction of MnX (X = O, S, and Se) catalysts

In this study, a series of Mn-based compounds, MnX (X = O, S, and Se), were prepared and investigated as electrocatalysts for the oxygen reduction reaction (ORR). These compounds adopt the same rock-salt-type crystal structure and present a similar morphology and close particle size. Among them, the unreported MnSe catalyst exhibits the best performance towards the ORR, in terms of onset potential, kinetic current density, and four-electron selectivity, as demonstrated by cyclic voltammetry (CV) and polarization measurements. The different activities of MnX can be ascribed to the anion, which can assist in the change of the Mn valance state. Besides, the methanol tolerance and stability of MnSe are comparable to those of commercial Pt/C. Our results would enlighten the rational design of transition metal-based ORR catalytic materials by taking advantages of the anion effect.