A strategy for the synthesis of VN@C and VC@C core-shell composites with hierarchically porous structures and large specific surface areas for high performance symmetric supercapacitors.

A novel strategy for the fabrication of vanadium nitride (VN) and vanadium carbide (VC) encapsulated into amorphous carbon nanotube core-shell structured composites (denoted as VN@C and VC@C) was developed by the thermal treatment with H2V3O8@C core-shell composites under N2 and Ar atmospheres, respectively. The as-prepared VN@C and VC@C were comprised of core-shell structures with cores of crystalline VN particles and particles and shells of amorphous carbon nanotubes. There are some O elements remaining both in VN@C and VC@C. VN@C and VC@C exhibited hierarchically porous structures ranging from mesopores to macropores and high specific surface areas, which reached 222 and 164 m2 g-1, respectively. Symmetric supercapacitor (SSC) devices using VN@C and VC@C (denoted as VN@C SSC and VC@C SSC) were assembled and they showed good pseudocapacitive properties and were promising electrode materials for electrochemical capacitors. The VN@C SSC device exhibited better electrochemical performance including specific capacitance, areal energy density and cycling stability than the VC@C SSC device. The present findings revealed that VN@C and VC@C could be considered as potential materials for high-performance energy storage materials.