Abstract: One dimensional α-MnO2 nanorods were etched for surface modification by ferrous ion，and the nanorods with different etching degrees were obtained by a facile liquid phase redox reaction.Electrochemical studies indicated that the nanorods obtained under 20% etching conditions had higher activity than the pristine α-MnO2 and showed the accelerating kinetic process for the oxygen reduction reaction（ORR）.On the contrary，30% over etched nanorods exhibited worse oxygen reduction and lower electrical conductivity.The improvement of ORR performance is attributed to the reduce of the Mn4+ and the rise of more Mn3+ active sites caused by the defects of the materials，which can accelerates the speed controlling step of O2 adsorption and the kinetic process of ORR.Excessive etching of 30% resulted in a significant decrease in the electrical con ductivity and a decline in the ORR performance.The results showed that moderate etching can make a balance between the defects exposure and electrical conductivity，and thus leading to high efficient oxygen reduction electrocatalysts.

Key words: manganese dioxide；ferrous ions etched；oxygen reduction reaction