Anchoring carbon layers and oxygen vacancies endow WO 3- x /C electrode with high specific capacity and rate performance for supercapacitors.

Herein, novel hierarchical carbon layer-anchored WO 3- x /C ultra-long nanowires were developed via a facile solvent-thermal treatment and a subsequent rapid carbonization process. The inner anchored carbon layers and abundant oxygen vacancies endowed the WO 3- x /C nanowire electrode with high conductivity, as measured with a single nanowire, which greatly enhanced the redox reaction active sites and rate performance. Surprisingly, the WO 3- x /C electrode exhibited outstanding specific capacitance of 1032.16 F g -1 at the current density of 1 A g -1 in a 2 M H 2 SO 4 electrolyte and maintained the specific capacitance of 660 F g -1 when the current density increased to 50 A g -1 . Significantly, the constructed WO 3- x /C//WO 3- x /C symmetric supercapacitors achieved specific capacitance of 243.84 F g -1 at the current density of 0.5 A g -1 and maintained the capacitance retention of 94.29% after 5000 charging/discharging cycles at the current density of 4 A g -1 . These excellent electrochemical performances resulted from the fascinating structure of the WO 3- x /C nanowires, showing a great potential for future energy storage applications.