Preparation of MnO2-Cr2O3 mesoporous oxide and its application for an active and reversible air catalyst for Li-O2 batteries

Highlights: • Highly porous MnO₂ and Cr₂O₃ with regular structure was successfully obtained. • Obtained mesoprous MnO₂ and Cr₂O₃ shows high activity as air electrode of Li-O₂ battery. • Composite of single wall carbon nanotube and mesoporous MnO₂-Cr₂O₃ is active air electrode. • Reasonably large discharge capacity and cycle stability was achieved. -- Abstract: Preparation of highly porous MnO₂ and Cr₂O₃ with regular structure was investigated in this study by using hard template method. Cr₂O₃ nanoarchitects with regular pore structure and α-MnO₂ with porous nanosheet were successfully prepared. By mixing with single wall carbon nanotube (SWCNT), application of MnO₂, Cr₂O₃ nano architects (Mn-Cr oxides supported SWCNT) was studied as active air electrode for Li-O₂ battery which is now expecting as a new rechargeable battery with large capacity. It was found that the synergy effects between two mesoporous metal oxides with SWCNT resulted in excellent electrochemical properties of air electrode. Prepared Mn-Cr oxide supported SWCNT can sustain stable charge and discharge capacity up to 150 cycles with 500 mAh/g without capacity degradation indicating outstanding catalytic activity for oxygen reduction and evolution reaction (ORR/OER). Consecutive cyclic voltammetry tests also showed excellent reversibility of formation and decomposition of reaction products of Li₂O₂. This could be resulted from large pore volume and ordered structure of Cr₂O₃, MnO₂/SWCNT air electrode.