Low-temperature direct synthesis of mesoporous vanadium nitrides for electrochemical capacitors

Mesoporous vanadium nitrides are directly synthesized by a one-step chemical precipitation method at a low temperature (70 degrees C). Structural and morphological analyses reveal that vanadium nitride consist of long and slender nanowhiskers, and mesopores with diameters of 2-5 nm. Compositional analysis confirms the presence of vanadium in the VN structure, along with oxidized vanadium. The cyclic voltammetry and charge-discharge tests indicate that the obtained material stores charges via a combination of electric double-layer capacitance and pseudocapacitance mechanisms. The vanadium nitride electrode exhibits a specific capacitance of 598 F/g at a current density of 4 Ng. After 5000 charge-discharge cycles, the electrode has an equivalent series resistance of 1.42 Omega and retains 83% of its initial specific capacitance. This direct low-temperature synthesis of mesoporous vanadium nitrides is a simple and promising method to achieve high specific capacitance and low equivalent series resistance for electrochemical capacitor applications. (C) 2016 Elsevier B.V. All rights reserved.