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

To fully manifest the high energy densities of lithium-oxygen (Li-O2) 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 Li2O2. To address these issues, this work proposes a grafted hybrid nanosheet array architecture to enable efficient bifunctional oxygen catalytic cathodes for Li-O2 batteries. As a demonstration, Co3O4 nanosheet arrays (MnO2-Co3O4@CC) grafted with MnO2 nanosheets are prepared on carbon cloth by facile electrodeposition followed by calcination in air. The mutually perpendicular Co3O4 and MnO2 nanosheets in the grafted architecture enable both the ORR catalytically active site of MnO2 and the OER catalytically active site of Co3O4 easily accessible during repeated cycling. Thus, the synergistic bifunctional catalysis of hybrid MnO2-Co3O4@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. Co3O4 nanosheet arrays grafted by MnO2 nanosheets on carbon cloth (MnO2-Co3O4@CC) are successfully prepared as oxygen cathodes for lithium-oxygen batteries. The mutually perpendicular nanosheets in the grafted architecture manifest both the oxygen reduion reaction (ORR) and the oxygen evolution reaction (OER) catalytically active sites to achieve the synergistic bifunctional catalysis of hybrid MnO2-Co3O4@CC.image