Small nitrogen-doped carbon dots as efficient nanoenhancer for boosting the electrochemical performance of three-dimensional graphene.

As a new class of zero-dimensional carbon nanomaterials, carbon dots have triggered intensive research interest in various fields. However, the low surface area, hydrophilicity, and agglomeration characteristics limit their applications in energy storage fields. Herein, we demonstrate that nitrogen-doped carbon dots can be employed as efficient nanoenhancer to boost the electrochemical performance of three-dimensional graphene. The as-prepared materials exhibit an interconnected framework with abundant oxygen- and nitrogen-containing functional groups, which enable fast penetration and transport of electrolyte ions and provide more active sites and electric conductivity. Employed as binder-free electrode for supercapacitors, the resultant materials present high specific capacitance (338 F g-1 ) and areal capacitance (604 μF cm-2 ) at a current density of 0.5 A g-1 , which is much higher than that of pristine three-dimensional graphene (190 F g-1 , and 114 μF cm-2 ), with an enhancement of 78% and 430%, respectively. Moreover, superior long-term cycling stability (94% of capacitance retention after 20 000 charging/discharging cycles at 10 A g-1 ) as well as improved electric conductivity can also be achieved. These results certify that nitrogen-doped carbon dots can be applied as nanobooster to comprehensively improve the performance of graphene for high-performance electrochemical energy storage.