Graphene has great potential to significantly enhance the electrochemical activity of redox-active materials for supercapacitors. However, the agglomeration of graphene sheets remains a critical challenge to excellent energy storage performance of hybrid composites supported by graphene. Herein, a facile hydrothermal approach for the synthesis of porous Ni2CO3(OH)2/functionalized graphene (NCB/FGN) composites is developed. To improve the dispersion properties of graphene, sulfonated salicylic acid serving as a functionalized composition is covalently anchored to the surface of functionalized graphene. The systematic investigation indicates that the presence of functionalized graphene plays a crucial role in establishing the porous structure of hybrid composites. Compared to reduced graphene oxide (rGO), functionalized graphene is more beneficial to accommodate the expansion of the surface area and the reduction of the pore length in hybrid composites. The detailed electrochemical characterization demonstrates that the unique porous structure of NCB/FGN composites encompasses the great capability of rapid kinetic diffusion of active ions in electrolytes during the electrochemical reaction. The specific capacitance of NCB/FGN composites is 1508 F g−1 at a current density of 1 A g−1, higher than 1258 F g−1 for NCB/rGO composites and 1039 F g−1 for pristine NCB. After 3000 charge–discharge cycles at a current density of 10 A g−1, the specific capacitance of NCB/FGN composites still approaches their initial capacitance.

A facile approach for the fabrication of NiO/sulfonated graphene composites (NiO/sGNS) using ammonium carbamate as a precipitating agent was developed. With an enhanced specific surface area and a desirable surface chemical environment, the NiO/sulfonated graphene composites exhibit excellent electrochemical performance. The results from cyclic voltammetry (CV) demonstrate that traditional electrical double-layer capacitive processes contribute to improving the storage energy capabilities of the NiO/sGNS composites. Galvanostatic charge–discharge tests show that the specific capacitance of the NiO/sulfonated graphene composites increased to 530 F g−1 at a current density of 1.0 A g−1 in comparison with specific capacitances of 382 F g−1 for NiO/thermal reduced graphene composites (NiO/TRG) and 238 F g−1 for pristine NiO. Moreover, electrochemical impedance spectroscopy (EIS) indicates the considerable effect of sulfonated graphene on building electron and ion transport channels for faradaic reaction processes of the NiO/sGNS composites.

Graphene has great potential to significantly enhance the electrochemical activity of redox-active materials for supercapacitors. However, the agglomeration of graphene sheets remains a critical challenge to excellent energy storage performance of hybrid composites supported by graphene. Herein, a facile hydrothermal approach for the synthesis of porous Ni2CO3(OH)2/functionalized graphene (NCB/FGN) composites is developed. To improve the dispersion properties of graphene, sulfonated salicylic acid serving as a functionalized composition is covalently anchored to the surface of functionalized graphene. The systematic investigation indicates that the presence of functionalized graphene plays a crucial role in establishing the porous structure of hybrid composites. Compared to reduced graphene oxide (rGO), functionalized graphene is more beneficial to accommodate the expansion of the surface area and the reduction of the pore length in hybrid composites. The detailed electrochemical characterization demonstrates that the unique porous structure of NCB/FGN composites encompasses the great capability of rapid kinetic diffusion of active ions in electrolytes during the electrochemical reaction. The specific capacitance of NCB/FGN composites is 1508 F g−1 at a current density of 1 A g−1, higher than 1258 F g−1 for NCB/rGO composites and 1039 F g−1 for pristine NCB. After 3000 charge–discharge cycles at a current density of 10 A g−1, the specific capacitance of NCB/FGN composites still approaches their initial capacitance.