Tuning and understanding the supercapacitance of heteroatom-doped graphene

Carbon nanomaterials are promising for making high-performance supercapacitors. However, their specific capacitances and energy densities still need further improvement for many important and challenging applications. Here we report the superior capacitive performance of heteroatom-doped graphene synthesized by a thermal annealing method at low temperature (200 degrees C), and remarkably enhanced specific capacitance of 629 F g(-1) at 0.2 A g(-1), energy density of 43 Wh kg(-1) at 140W kg(-1), and cycle life of 10,000 times are achieved. The mechanisms for the outstanding performance are analyzed, and a corresponding model connecting the dopant and capacitance is proposed and validated by the first-principle calculations. The thermal annealing temperature plays a critical role in the dopant configuration of heteroatom and hence significantly affects the capacitive properties of graphene If annealing at low temperature, non-graphitic dopant configuration is dominant, inducing a large Faradaic pseudocapacitance; if annealing at high temperature, graphitic clopant configuration is dominant, giving rise to a relatively lower electrical double layer capacitance. These findings demonstrate that the supercapacitance of graphene can be purposely tuned by the rational doping of heteroatoms, which may open up new strategies for further design and application of advanced graphene-based materials for electrochemical supercapacitors. (C) 2015 Elsevier B.V. All rights reserved.