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

Abstract

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.