Polyethyleneimine-Mediated Fabrication of Two-Dimensional Cobalt Sulfide/Graphene Hybrid Nanosheets for High-Performance Supercapacitors

Abstract

Two-dimensional (2D) hybrid nanosheets made of electrochemically active materials and graphene, featuring fast reaction kinetics and excellent structural stability, are appealing as electrodes for supercapacitors. Herein, we report a general polyethyleneimine (PEI)-mediated fabrication of the 2D cobalt sulfide/graphene hybrid nanosheets via a facile hydrothermal strategy. Detailed analysis reveals that the uniform cobalt sulfide (CoS) nanoparticles are well-anchored on the 2D graphene surface. Thereinto, the nitrogen species originating from the PEI molecules as bridging sites are helpful in enhancing the coupling effect between the graphene and CoS species, which endows the hybrid nanosheets with high electroactivity and excellent structural stability. The as-obtained hybrid nanosheets with typical pseudocapacitive features demonstrate a high specific capacitance (320 F g–1@1 A g–1) and a superior electrochemical stability with the initial capacitance of 86.5% after 20 000 cycles as electrodes for supercapacitors. The assembled asymmetric supercapacitors by combining activated carbon electrodes further show a high charge storage of 28.8 Wh kg–1 with an output power of 130 W kg–1. More importantly, the similar strategy can be easily extended to fabricate other 2D hybrid nanosheets with extraordinary electrochemical performance with the maximum charge storage of 815 F g–1 and energy density of 44. 6 Wh kg–1. The present work, which achieves the general fabrication of 2D hybrid nanosheets with tuned compositions, may provide a new opportunity for the development of supercapacitors.

Boosting Supercapacitor Performance of Graphene by Coupling with Nitrogen‐Doped Hollow Carbon Frameworks

“…Graphene oxide (GO) and PEI‐functionalized graphene (G‐P) were first prepared according to our previous literature . The obtained G‐P nanosheets were dissolved into 60 mL methyl alcohol, followed by ultrasonic treatment for 0.5 hours.…”

“…Graphene oxide (GO) and PEI-functionalized graphene (G-P) were first prepared according to our previous literature. [39,40] The ob- tained G-P nanosheets were dissolved into 60 mL methyl alcohol, followed by ultrasonic treatment for 0.5 hours. Then, 1.46 gm etal salts (Zn(NO 3 ) 2 •6H 2 O) was dissolved into 20 mL methyl alcohol to obtain ah omogeneous solution, which was slowly poured into the above G-P solution and further stirred for another 12 h. Thereafter, 2.5 gd imethylimidazole was mixed with 20 mL methyl alcohol and then poured into the above solution to react with Zn 2 + for 6hours.…”

Biomass-Derived Carbon Materials for High-Performance Supercapacitors: Current Status and Perspective

“…Among pseudocapacitive materials, conducting polymers and metallic oxides are particularly promising and can easily be combined with various carbon materials such as graphene (Gr) [145], carbon nanotubes (CNTs) [146] and porous carbon [147] to fabricate composite materials with suitable physicochemical properties to satisfy the requirements of high-energy-density SCs. Traditional approaches to the facile production of composite electrodes are too complex and expensive, however, and hinder further application on a practical scale, and therefore, the combination of biomass-based carbon materials with pseudocapacitive materials through green, facile and renewable methods is more promising.…”

Hierarchical Transition Metal Oxide Arrays Grown on Graphene‐Based Fibers with Enhanced Interface by Thin Layer of Carbon toward Solid‐State Asymmetric Supercapacitors

“…For cathode materials, the combination of carbon substrate with electrochemically active transition metal compounds including MnO 2 , CoS, Co 3 O 4 , and NiCo‐double hydroxide (NiCo‐DH) is an effective strategy for constructing high‐performance supercapacitors. In particular, conductive graphene frameworks could improve the conductivity of electrodes and provide ion transport channels for faradaic reactions .…”