Construction of NiCo2S4 heterostructure based on electrochemically exfoliated graphene for high-performance hybrid supercapacitor electrode

Bimetallic transition metal sulfides (TMSs) hold great promise as electrode materials for supercapacitive energy storage devices compared with their monometallic counterparts. However, it is still necessary to develop efficient synthetic protocols for favorable electrode architecture in order to further improve the electrochemical performance. This study presents a facile and controllable method to construct NiCo2S4 heterostructure based on electrochemically exfoliated graphene with good adhesion, which involves the growth of bimetallic MOF precursor and in-situ conversion into NiCo2S4 nanoparticles. This integrated architecture was found to be efficient for supercapacitive energy storage, as evident by the improved utilization of NiCo2S4 and excellent electrochemical performance including high capacity of 1802.5 F g(-1) at 1 A g(-1) and good rate capability (86.1% capacity retention at 10 A g(-1)). Additionally, N-doped mesoporous carbon spheres (NMCS) were synthesized by sacrificial template method and used as anode for practical application. Benefiting from good charge balance and compatibility, the assembled EEG@NiCo2S4//NMCS hybrid supercapacitor (HSC) exhibited outstanding energy density (30.4 Wh kg(-1) at 800.0 W kg(-1)) and excellent cycling stability (80.1% capacitance retention after 9000 cycles). (C) 2020 Elsevier B.V. All rights reserved.