Boosting the cyclic stability and supercapacitive performance of graphene hydrogels via excessive nitrogen doping: Experimental and DFT insights

Abstract

Nitrogen-doped mesoporous graphene hydrogel (MGHG) enjoys many unique characteristics for use as an efficient energy storage electrode material. Herein, a green one-pot hydrothermal synthesis strategy was employed to synthesize highly hydrophilic nitrogen-doped mesoporous graphene hydrogel. The morphological, structural, and compositional analyses were performed using FESEM, XRD, and XPS techniques. The as-prepared MGHG exhibits high wettability (contact angle = 58.9o), high surface area (318.226 m2/g), and an unprecedented nitrogen doping content of 2.95%. The fabricated MGHG was evaluated as a supercapacitor material in 1 M aqueous K2SO4 electrolyte, revealing a maximum specific capacitance of 595.7 F.g−1 with a low equivalent series resistance (0.1664 Ω) that is ascribed to the high porosity, high surface area, and the available nitrogen redox active sites. To further elucidate the electrochemical performance of MGHG, a symmetric supercapacitor device was assembled using MGHM as negative and positive electrodes. The fabricated device shows a maximum specific energy of 30 Wh kg−1 corresponding to a specific power 1000 W kg−1. The density functional theory (DFT) computations were utilized to better understand the high performance of the assembled devices. These superior results demonstrate the excellent performance of MGHG as a potential material for highly-performing supercapacitor devices with a potential window of 2.2 V.