Synthesis of C/Co3O4 composite mesoporous hollow sphere sandwich graphene films for high-performance supercapacitors

Carbon/Co3O4 composite mesoporous hollow spheres (C/Co3O4 MHSs) and graphene oxide were successfully synthesized to fabricate hybrid films. Unique sandwich and mesoporous structures can provide more pathways for electrolyte transmission and achieve excellent electrochemical performance. After combining with C/Co3O4 MHSs, the hybrid films can achieve a specific capacity of 1266.0 F g(-1) at a current density of 1 A g(-1), which is much higher than that of the C/Co3O4 MHSs (153.9 F g(-1)) and reduced graphene oxide (rGO) films (213.5 F g(-1)). Moreover, a rGO/C/Co3O4//rGO asymmetric supercapacitor (ASC) device was fabricated. The ASC exhibits a high energy density of 32.7 Wh kg(-1) (power density of 800 W kg(-1)) and an excellent cycling stability with 85.9% capacitance retention after 5000 cycles. Besides, white LED bulbs (3.2 V) can be lit by two ASCs in series.