Spherical α-MnO(2) Supported on N-KB as Efficient Electrocatalyst for Oxygen Reduction in Al–Air Battery

Traditional noble metal platinum (Pt) is regarded as a bifunctional oxygen catalyst due to its highly catalytic efficiency, but its commercial availability and application is often restricted by high cost. Herein, a cheap and effective catalyst mixed with α-MnO(2) and nitrogen-doped Ketjenblack (N-KB) (denoted as MnO(2)-SM150-0.5) is examined as a potential electrocatalyst in oxygen reduction reactions (ORR) and oxygen evolution reactions (OER). This α-MnO(2) is prepared by redox reaction between K(2)S(2)O(8) and MnSO(4) in acid conditions with a facile hydrothermal process (named the SM method). As a result, MnO(2)-SM150-0.5 exhibits a good catalytic performance for ORR in alkaline solution, and this result is comparable to a Pt/C catalyst. Moreover, this catalyst also shows superior durability and methanol tolerance compared with a Pt/C catalyst. It also displays a discharge voltage (~1.28 V) at a discharge density of 50 mA cm(−2) in homemade Al–air batteries that is higher than commercial 20% Pt/C (~1.19 V). The superior electrocatalytic performance of MnO(2)-SM150-0.5 could be attributed to its higher Mn(3+)/Mn(4+) ratio and the synergistic effect between MnO(2) and the nitrogen-doped KB. This study provides a novel strategy for the preparation of an MnO(2)-based composite electrocatalyst.