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

A capacitive electrode material of nanocrystalline intermetallic W₂C has been synthesized and studied for electrochemical capacitors. A specific capacitance of 158.2 F g⁻¹ is found in 1 mol dm⁻³ H₂SO₄ (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. W₂C 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 W₂C//activated carbon shows a high energy density and accompanying power density of 19.2 and 8976.6 W kg⁻¹, facilitating high duty applications.