Manganese oxides (MnOx) in a-, b-, g-, d-MnO2 phases, Mn3O4, Mn2O3, and MnOOH are synthesized for
systematically comparing their electrocatalytic activity of the oxygen reduction reaction (ORR) in the Zn
eair battery application. The optimal MnOx/XC-72 mass ratio for the ORR is equal to 1 and the oxide
crystalline structure effect on the ORR is compared. The order of composites with respect to decreasing
the ORR activity is: a-MnO2/XC-72 > g-MnO2/XC-72 > b-MnO2/XC-72 > d-MnO2/XC-72 > Mn2O3/XC-
72 > Mn3O4/XC-72 > MnOOH/XC-72. The textural properties of MnOx are investigated by scanning
electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms
with BrunauereEmmetteTeller (BET) analysis, X-ray diffraction (XRD), and thermogravimetric
analysis (TGA). Electrochemical studies include linear sweep voltammetry (LSV), rotating ring-disk
electrode (RRDE) voltammetry, and the full-cell discharge test. The discharge peak power density of
Zneair batteries varies from 61.5 mW cm2 (a-MnO2/XC-72) to 47.1 mW cm2 (Mn3O4/XC-72). The
maximum peak power density is 102 mW cm2 for the Zneair battery with an air cathode containing a-
MnO2/XC-72 under an oxygen atmosphere when the carbon paper is 10AA. The specific capacity of all
full-cell tests is higher than 750 mAh g1 at all discharge current densities.