Bimetal Oxides Anchored on Carbon Nanotubes/Nanosheets as High-Efficiency and Durable Bifunctional Oxygen Catalyst for Advanced Zn-Air Battery: Experiments and DFT Calculations

To meet increasing requirement for innovative energy storage and conversion technology, it is urgent to prepare effective, affordable, and long-term stable oxygen electrocatalysts to replace precious metal-based counterparts. Herein, a two-step pyrolysis strategy is developed for controlled synthesis of Fe2O3 and Mn3O4 anchored on carbon nanotubes/nanosheets (Fe2O3-Mn3O4-CNTs/NSs). The typical catalyst has a high half-wave potential (E1/2 = 0.87 V) for oxygen reduction reaction (ORR), accompanied with a smaller overpotential (eta 10 = 290 mV) for oxygen evolution reaction (OER), showing substantial improvement in the ORR and OER performances. As well, density functional theory calculations are performed to illustrate the catalytic mechanism, where the in situ generated Fe2O3 directly correlates to the reduced energy barrier, rather than Mn3O4. The Fe2O3-Mn3O4-CNTs/NSs-based Zn-air battery exhibits a high-power density (153 mW cm-2) and satisfyingly long durability (1650 charge/discharge cycles/550 h). This work provides a new reference for preparation of highly reversible oxygen conversion catalysts. Fe2O3-Mn3O4-CNTs/NSs are fabricated by a facile pyrolysis method. The specific structure of carbon nanotubes and carbon nanosheets provide large ECSA and expose more active sites. The catalyst shows excellent oxygen conversion efficiency and durability in Zn-air battery. image