Defect induced tunable nitrogen configuration in holey graphene for enhanced supercapacitive performance

Abstract

Nitrogen (N) doped graphene has attracted various attention in many fields due to its adjustable physicochemical properties. However, directional control of graphitic N content in graphene sheets under mild conditions without decreasing the total N content remains a challenge. Here, by combining the defect engineering and lattice restoring agent, tuning the graphitic N contents in a wide range can be achieved at low temperature. X-ray photoelectron spectroscopy (XPS) was used for identifying the N configuration and N content. The content of total N changes from 5.62% to 6.61%, and the content of graphitic N changes from 10.73% to 82.34% with the increase of defects in graphene sheets. Results from electrochemical impedance spectroscopy (EIS) suggest that the ion diffusion capacity increases with the increasing defect level. Results from scanning electron microscopy (SEM) suggest that higher defect level leads to smaller wrinkle structure. Nitrogen adsorption-desorption and electrochemical tests suggest that the specific pore volume, specific surface area and specific capacitances of the optimum sample are 4.35, 2.06 and 1.89 times higher than those samples without defect-introducing- treatment. The supercapacitor assembled with thus modified graphene has a high energy density of 13.8 Wh·Kg−1 and a high power density of 13 000 W·Kg−1. Moreover, the assembled supercapacitor holds a high capacitance retention of 86.8% after 10,000 charge-discharge cycles at 20 A·g−1. This simple and effective method of tuning surface chemistry of graphene provides a reference for the functionalization of graphene.