A Grafted Hybrid Nanosheet Array Architecture Enables Efficient Bifunctional Oxygen Catalytic Electrodes for Rechargeable Lithium−Oxygen Batteries

Abstract To fully manifest the high energy densities of lithium−oxygen (Li−O 2 ) batteries, bifunctional catalytic cathodes that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are mandatorily required. However, catalysts with intrinsic bifunctional catalytic activities are limited in practice. In addition, the practical utilization rate of oxygen catalytic cathodes is usually lower due to the deposition of insoluble discharge product Li 2 O 2 . To address these issues, this work proposes a grafted hybrid nanosheet array architecture to enable efficient bifunctional oxygen catalytic cathodes for Li−O 2 batteries. As a demonstration, Co 3 O 4 nanosheet arrays (MnO 2 −Co 3 O 4 @CC) grafted with MnO 2 nanosheets are prepared on carbon cloth by facile electrodeposition followed by calcination in air. The mutually perpendicular Co 3 O 4 and MnO 2 nanosheets in the grafted architecture enable both the ORR catalytically active site of MnO 2 and the OER catalytically active site of Co 3 O 4 easily accessible during repeated cycling. Thus, the synergistic bifunctional catalysis of hybrid MnO 2 −Co 3 O 4 @CC is effectively realized to deliver a high specific capacity of 8115 mA h g −1 and a low overall overpotential of 0.64 V. This work provides a universal and effective approach for fabricating various efficient catalytic electrodes via the facile integration of different nanomaterials on nanoarray architectures.