Nanocrystalline Intermetallic Tungsten Carbide: Nanoscaled Solidoid Synthesis, Nonfaradaic Pseudocapacitive Property, and Electrode Material Application

摘要

A capacitive electrode material of nanocrystalline intermetallic W_2C has been synthesized and studied for electrochemical capacitors. A specific capacitance of 158.2 F g~(-1) is found in 1 mol dm~(-3) H_2SO_4 (aq) at a specific current density of 1 A g~(-1), and 99.5% of capacitance remains after 5000 cycles of charging- discharging. 88.9% of the initial value remains at a current density of 10 A g~(-1). W_2C exhibits a high electrochemical capacitance that may be attributed to the electrical conductivity, which can promote the electrochemical performance more observably and ensure a long life cycle and fast electrical charge transfer rate. Based on the specific surface areas and specific capacitances, the sub-surface space nonfaradaic pseudocapacitive mechanism is proposed. In addition, the assembled asymmetrical electrochemical capacitor of W_2C//activated carbon shows a high energy density and accompanying power density of 19.2 and 8976.6 W kg~(-1), facilitating high duty applications.