High-performance binder-free RuO2/electrospun carbon fiber for supercapacitor electrodes

Abstract

Binder-free RuO2/carbon fiber composite electrodes were prepared by depositing RuO2 on electrospun carbon fibers using the incipient wetness impregnation method. The amount of RuO2 in the composites monotonically increased with the number of impregnation cycles. When the composite was thermally treated at 300 °C, RuO2 particles coalesced to form a wrinkle-like structure. Additionally, hydrous RuO2 partly converted to crystalline RuO2. We demonstrated that the relative contents of crystalline and hydrous RuO2 were closely related to the amount of RuO2 in the composite: the crystalline RuO2 content increased, whereas the hydrous RuO2 content decreased with an increase in the amount of RuO2 in the composite. When the composites were used as supercapacitor electrodes, the specific capacitance increased and then decreased with the amount of RuO2 in the composite. The maximum capacitance of 544 F/g in 2 M of H2SO4 at a scan rate of 2 mV/s was achieved with an RuO2 content of 12.23%; this was attributed to the favorable RuO2 content in the composite and the suitable amounts of hydrous/crystalline RuO2. When the amount of RuO2 in the composite was high, RuO2 caused fiber fracture during electrochemical reactions, resulting in poor electrode stability.