▎ 摘　　要

This paper reports the preparation of alpha-MnO2 NWs/graphene composites as the cathode catalyst for magnesium-air fuel cell and its excellent electrochemistry performance. The composites are synthesized by self-assembly of alpha-MnO2 nan alpha-MnO2 NWs/graphene was synthesized and studied in Mg-air fuel cell. alpha-MnO2 NWs/graphene was synthesized and studied in Mg-air fuel cell. owires (NWs) on the surface of graphene via a simple hydrothermal method. The alpha-MnO2 NWs/graphene composites showed a higher electrochemical activity than the commercial MnO2. The oxygen reduction peak of the alpha-MnO2 NWs/ graphene composites catalyst is tested in a 0.1 M KOH solution at -0.252 V, which is more positive than the commercial MnO2 (-0.287 V). The ORR limit current density for 28% alpha-MnO2 NWs/graphene composite is approximately 2.74 mA/cm(2), which is similar to that of the 20% Pt/C(2.79 mA/cm(2)) in the same conditions. Based on the Koutecky-Levich plot, the ORR mechanism of the composite involves a one-step, quasi-4-electron pathway. In addition, magnesium-air fuel cell with alpha-MnO2 NWs/graphene as catalyst possesses higher current density (140 mA/cm(2)) and power density (96 mW/cm(2)) compared to the commercial MnO2. This study proves that the cost-effective alpha-MnO2 NWs/ graphene with higher power generation ability make it possible for the substitute of the noble metals catalyst in the Mg-air fuel cell. (C) 2016 Published by Elsevier Ltd.