DC-field-driven combustion waves for one-step fabrication of reduced manganese oxide/multi-walled carbon nanotube hybrid nanostructures as high-performance supercapacitor electrodes

Abstract

Micro–nanostructured metal oxides can facilitate the development of electrochemical electrodes with enhanced features for supercapacitors and batteries. However, the fabrication of electrodes using precisely controlled metal oxides generally requires high-cost, multi-step procedures, which limits the scalability. Herein, we report that a direct current-field-driven combustion wave (DC-CW) enables the one-step fabrication of high-performance supercapacitor electrodes from hybrid nanostructures comprising reduced manganese oxides and multi-walled carbon nanotubes (MWCNTs). A layered film of MnO₂ nanoparticles (NPs) and MWCNTs on a nitrocellulose membrane is prepared and subsequently subjected to a DC-electric field, thereby igniting and propagating CWs throughout the film surface within one second. The underlying mechanism of the DC-CW process is elucidated by comparative analysis of the electrodes generated by the laser irradiation-driven combustion wave process without the DC-field and the as-prepared MnO₂/MWCNT film. The Mn_xO_y/MWCNT hybrids via DC-CWs exhibit higher specific capacitance (757 F g⁻¹) and capacitance retention (100%) than the other two systems over 10 000 charge–discharge cycles, due to the improved inter-conductivity and substantial contact interfaces in heterogeneously mixed, less agglomerated nanostructures. The DC-CWs may enable various manipulation methods of micro–nanostructured metal oxides and their hybrid structures via a low-cost, fast, and scalable process for high-performance electrochemical electrodes.