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Summary: Obstacles to the efficient operation of rechargeable aluminum‐air batteries include slow oxygen reduction reaction (ORR), slow kinetics, and large overpotential of oxygen evolution reactions (OER). An effective solution is to develop a new bifunctional electrocatalyst that is effective for both the ORR/OER processes. In this study, we prepared the α‐MnO2/Co3O4 bifunctional composite catalyst by the in situ generation of Co3O4 nanoparticles on α‐MnO2 nanorods. ORR/OER catalytic activity and structures of the prepared catalysts have been investigated systematically. Compared with single‐component α‐MnO2 nanorods and Co3O4 particles catalyst, the α‐MnO2/Co3O4 composite catalyst possesses the smallest average pore diameter (11.84 nm), and the largest specific surface area (41.34 m2 g−1), which is due to the restriction of the growth of Co3O4 particles by α‐MnO2 nanorods. Besides, during the ORR process, the α‐MnO2/Co3O4 composite catalyst shows the most positive onset potential of 0.833 V, the most positive half‐wave potential of 0.760 V, and the biggest limiting current density of 3.881 mA cm−2. Meanwhile, during the OER process, the composite catalyst exhibits the lowest onset potential of 1.630 V, the lowest overpotential of 554 mV, and the biggest limiting current density of 24.590 mA cm−2. Furthermore, the α‐MnO2/Co3O4‐assembled aluminum‐air battery (AAB) delivers the best cycling performance. Our work provides an idea for optimizing the bifunctional catalyst with high ORR/OER activity and low cost used in secondary AAB. Highlights: A novel α‐MnO2/Co3O4 bifunctional composite catalyst was prepared successfully.The α‐MnO2/Co3O4 composite catalyst was applied in a rechargeable Al‐air battery.The α‐MnO2/Co3O4 exhibited better ORR/OER catalytic activity than α‐MnO2 and Co3O4.The Al‐air battery using α‐MnO2/Co3O4 catalyst showed excellent cycling performances. Novelty Statement: This is our original work. Neither the entire paper nor any part of its content has been published or has been accepted elsewhere. It is not being submitted to any other journal. [ABSTRACT FROM AUTHOR]

Overcoming the self-corrosion and surface passivation of aluminum anode, and the slow kinetics of cathodic electrochemical reactions are of great significance for the practical application of aluminum–air battery. In this study, we replaced the traditional aqueous electrolyte with AlCl 3 -urea ionic liquid electrolyte, and prepared Co–MnO 2 /C catalysts as cathode catalyst. Structures and electrocatalytic activity of the x % Co–MnO 2 /C (x is the mole percent of Co to Mn, x = 0, 10, 20, 30, 40 and 50) catalysts have been investigated systematically. After Co ions intercalation, the specific surface area of the catalyst increased and average pore diameter decreased. The unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalyst in the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) compared with MnO 2 /C. In particular, 40% Co–MnO 2 /C showed the largest specific surface area (154.25 m2 g−1) and the smallest average pore diameter (6.47 nm). It showed the most positive half-wave potential (0.727 V vs. RHE) and the biggest limiting current density (4.744 mA cm−2) in ORR process, and also exhibited the lowest onset potential (1.593 V) and the biggest limit current density (15.177 mA cm−2) in OER process. Furthermore, aluminum–air battery assembled with 40% Co–MnO 2 /C demonstrated excellent reversible charge and discharge performance, which had an average discharge voltage of 1.5 V and an average charge voltage of 2 V during 30 cycles at a limited battery capacity of 375 mAh g−1. Our results reveal the possibility of designing a rechargeable aluminum-air battery working at ambient conditions based on the Co–MnO 2 /C air cathode catalyst for the first time. Our work opens up a new way to achieve the rechargeability of aluminum-air batteries, and our highly active electrocatalytic materials can be used in a wider range of electrochemical energy applications. Co–MnO 2 /C catalysts were prepared by intercalating Co ions between MnO 2 layers, the unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalysts in ORR/OER process compared with MnO 2 /C, and the aluminum–air battery assembled with 40% Co–MnO 2 /C catalyst and AlCl 3 -urea ionic liquid electrolyte demonstrated excellent reversible charge and discharge performance. Image 1 • A novel Co–MnO 2 /C catalyst was successfully prepared by intercalating Co ions between MnO 2 layers. • The unique interaction between Co ions and MnO 2 led to an increase in the catalytic activity of the catalyst. • 40% Co–MnO 2 /C as air cathode catalyst exhibited the best ORR/OER catalytic activity. • A button-type rechargeable aluminum-air battery working at ambient conditions was designed for the first time. • As-prepared aluminum-air battery demonstrated excellent reversible charge and discharge performance. [ABSTRACT FROM AUTHOR]