encapsulation of CoO polyhedra in graphene sheets for high-capacitance supercapacitors

• Published in: Dalton transactions : an international journal of inorganic chemistry 2019-04, Vol.48 (17), p.5773-5778
• Main Authors: Lin, Guanyu, Jiang, Yulin, He, Chengen, Huang, Zhiyong, Zhang, Xiaofang, Yang, Yingkui
• Format: Article
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c9dt00521h

Co 3 O 4 polyhedra were well encapsulated in reduced graphene oxide (rGO) sheets by in situ growth of Co-based zeolitic imidazolate framework (ZIF-67) polyhedra in the presence of graphene oxide followed by thermal annealing. The resultant rGO/Co 3 O 4 composites consist of a continuously-conductive double-network constructed from graphene sheets and the derived N-doped carbons from ZIF-67, showing a large specific surface area of 523 m 2 g −1 . The as-fabricated symmetrical supercapacitor based on rGO/Co 3 O 4 exhibits a high specific capacitance of 277.5 F g −1 at 25 A g −1 and an energy density of 24.7 W h kg −1 at a power density of up to 40 kW kg −1 . The supercapacitor also retains 87.5% of the initial capacitance over 5000 cycles at 5 A g −1 . Such large capacitance, high energy density, and excellent cycling stability for rGO/Co 3 O 4 are attributable to the 3D double conductive network from 2D graphene sheets and porous channels of pseudo-capacitive Co 3 O 4 polyhedra. The graphene encapsulated Co 3 O 4 polyhedra (rGO/Co 3 O 4 ) exhibited large capacitance, high energy density, and excellent cycling stability, due to the 3D double conductive network from graphene sheets and porous channels of Co 3 O 4 polyhedra/N-doped carbon hybrid.