Co(9)S(8) nanoparticle-decorated carbon nanofibers as high-performance supercapacitor electrodes

This work reported Co(9)S(8) nanoparticle-decorated carbon nanofibers (CNF) as a supercapacitor electrode. By using a mild ion-exchange method, the cobalt oxide-based precursor nanoparticles were transformed to Co(9)S(8) nanoparticles in a microwave hydrothermal process, and these nanoparticles were decorated onto a carbon nanofiber backbone. The composition of the nanofibers can be readily tuned by varying the Co acetate content in the precursor. The porous carbon nanofibers offered a fast electron transfer pathway while the well dispersed Co(9)S(8) nanoparticles acted as the redox center for energy storage. As a result, high specific capacitance of 718 F g(−1) at 1 A g(−1) can be achieved with optimized Co(9)S(8) loading. The assembled asymmetric supercapacitor with Co(9)S(8)/CNF as the cathode showed a high energy density of 23.8 W h kg(−1) at a power density of 0.75 kW kg(−1) and good cycling stability (16.9% loss over 10 000 cycles).