Highly Conductive Mo 2 C Nanofibers Encapsulated in Ultrathin MnO 2 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 (Mo2 C NFs) have been fabricated by a facile and effective electrospinning strategy. Based on the cross-linked network architecture with ultrahigh electronic conductivity, each Mo2 C NF is uniformly encapsulated in lamellar manganese dioxide (MnO2 ) via electrodeposition, forming a self-supported MnO2 -Mo2 C NF film with excellent electrochemical activity. Remarkably, the highly conductive inner layer of porous Mo2 C NFs acts like a "highway" to facilitate charge transport and ionic diffusion, while the MnO2 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.