In-situ fabrication of manganese oxide nanorods decorated manganese oxide nanosheets as an efficient and durable catalyst for oxygen reduction reaction

Manganese oxide (MnO2 )-based nanostructures are believed to be an excellent catalyst capable of competing with the highly expensive and scary noble metal catalysts for oxygen reduction reaction (ORR). Herein, different structures of MnO2 such as nanorods, nanoflowers, and three dimensional (3D) spheres have been successfully synthesized by the controlled manner and their catalytic activity and mechanism for ORR were investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), rotating disc electrode (RDS), and electrochemical impedance spectroscopy (EIS). It is found that the 3D-MnO2 spheres exhibit outstanding catalytic performance with an over potential of 68 mV/dec for ORR which is lower than that of the nanoflowers (72 mV/dec) and nanorods (75 mV/dec), attributed by 4e(-) transfer pathway in alkaline media. The 3D-MnO2 spheres retained 96.8% of its original activity after 10000 s and superior methanol tolerance capability in comparison with commercial Pt/C catalyst. The high catalytic activity of the 3D-MnO2 sphere is mainly due to the high surface area and more active sites provided by its unique three-dimensional interconnectivity and mesoporous structure. The obtained results suggested that as-prepared catalyst can be used as an alternative to the highly expensive Pt-based catalyst for the ORR.