Enhancing Oxygen Reduction Reaction Activity of α-MnO2 Nanowires Through Ag Doping

Abstract

Enhancing the catalytic activity of manganese oxide in oxygen reduction reaction (ORR) is a key issue for its large-scale application in metal-air fuel cells. Ag-doped [Formula: see text]-MnO2 nanowires without Ag or Ag2O have been successfully synthesized via a facile hydrothermal method, and the changes in both the structure and electrochemical catalytic performances after Ag doping are investigated. Compared with the pristine [Formula: see text]-MnO2, the as-prepared Ag-doped MnO2 exhibits a significantly enhanced catalytic activity in both ORR and Mg-air fuel cell application. With Ag/Mn ratio of 1:25, Ag-doped MnO2 exhibits a typical 4e-reaction pathway and presents a 163 mV higher half-wave potential than that of the pristine [Formula: see text]-MnO2. Furthermore, it demonstrates a power density of 75.1[Formula: see text]mW[Formula: see text]cm[Formula: see text] at current density of 134.5[Formula: see text]mA[Formula: see text]cm[Formula: see text] in the Mg-air fuel cells. The enhanced ORR performances are considered to be contributed from the activation of surface lattice oxygen, the improvement in conductivity and the increase in oxygen vacancies of [Formula: see text]-MnO2. These findings provide new understanding for developing high-performance manganese oxide catalysts.