Growth restriction of Co3O4 nanoparticles by α-MnO2 nanorods as air cathode catalyst for rechargeable aluminum-air battery

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 alpha-MnO2/Co3O4 bifunctional composite catalyst by the in situ generation of Co3O4 nanoparticles on alpha-MnO2 nanorods. ORR/OER catalytic activity and structures of the prepared catalysts have been investigated systematically. Compared with single-component alpha-MnO2 nanorods and Co3O4 particles catalyst, the alpha-MnO2/Co3O4 composite catalyst possesses the smallest average pore diameter (11.84 nm), and the largest specific surface area (41.34 m(2) g(-1)), which is due to the restriction of the growth of Co3O4 particles by alpha-MnO2 nanorods. Besides, during the ORR process, the alpha-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 alpha-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 alpha-MnO2/Co3O4 bifunctional composite catalyst was prepared successfully. The alpha-MnO2/Co3O4 composite catalyst was applied in a rechargeable Al-air battery. The alpha-MnO2/Co3O4 exhibited better ORR/OER catalytic activity than alpha-MnO2 and Co3O4. The Al-air battery using alpha-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.

Automated summary

In this study, a novel α-MnO2/Co3O4 bifunctional composite catalyst was successfully prepared and applied in a rechargeable aluminum-air battery. The α-MnO2/Co3O4 catalyst exhibited better ORR/OER catalytic activity compared to α-MnO2 and Co3O4. The aluminum-air battery using the α-MnO2/Co3O4 catalyst showed excellent cycling performances.