Interweaving between MnO2 nanowires/ nanorods and carbon nanotubes as robust multifunctional electrode for both liquid and flexible electrochemical energy devices

Abstract In this paper, as a proof-of-concept study, a newly designed multifunctional composite electrode materials consisting of an interweaving structure of MnO2 nanowires (NWs)/nanorods (NRs) and carbon nanotubes (CNTs) (MnO2-NWRs/CNTs) are directly synthesized by a facile and scalable strategy, which show high catalytic activity for both oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) processes and large specific capacitance for supercapacitors (SCs). Such a MnO2-NWRs/CNTs350 material is induced by the strong coupling and synergistic effect between MnO2-NWRs and CNTs, as well as the coexistence of NRs/NWs and the existence of favorable crystal planes, which enable the multifunctional high-performance in zinc-air batteries (ZABs), magnesium-air batteries (MABs), SCs and also their flexible devices. The MnO2-NWRs/CNTs350 catalyst exhibits high electrochemical activity (ΔE: 0.98 V), decent capacitance (1183 F g−1) and excellent battery performance (specifically, 640 mW cm−2 for MABs). In MnO2-NWRs/CNTs350, the (110) and (101) crystal planes of MnO2-NWRs are advantageous for both ORR and OER processes. Additionally, the structural changes of MnO2-NWRs/CNTs350 (the coexistent NRs and NWs) improve the capacitance of the material. Even more encouraging, the interweaving structure endows the flexible rechargeable MABs, ZABs, and SCs with excellent electrochemical performance in terms of both activity and stability.