Highly Conductive Mo₂C Nanofibers Encapsulated in Ultrathin MnO₂ Nanosheets as a Self-Supported Electrode for High-Performance Capacitive Energy Storage

Nanostructured transition metal carbides (TMCs) with superior electrochemical properties are promising materials for high-efficiency energy-storage applications. Herein one-dimensional molybdenum carbide nanofibers (Mo 2 C NFs) have been fabricated by a facile and effective electrospinning strategy. Based on the cross-linked network architecture with ultrahigh electronic conductivity, each Mo 2 C NF is uniformly encapsulated in lamellar manganese dioxide (MnO 2 ) via electrodeposition, forming a self-supported MnO 2 –Mo 2 C NF film with excellent electrochemical activity. Remarkably, the highly conductive inner layer of porous Mo 2 C NFs acts like a “highway” to facilitate charge transport and ionic diffusion, while the MnO 2 nanosheets with abundant active area are favorable for the accumulation of effective electric charges. Benefiting from these features, the hybrid film is directly applied as the self-standing electrode of supercapacitors (SCs) without any additives, which delivers considerably large specific capacitance with strong durability in both aqueous and organic (ionic liquid) electrolytes. This work elucidates a feasible way toward heteronanofiber engineering of TMCs on a promising additive-free electrode for flexible and high-performance SCs.