Graphene oxide aided structural tailoring of 3-D N-doped amorphous carbon network for enhanced energy storage

Abstract

Organic aerogels are a class of material most suited for their transformation into electrically conducting porous carbon networks. Typically, polymeric aerogels are prepared via base- or acid-catalyzed polymerization of organic monomers. In this work, we report the first synthesis of graphene oxide (GO) induced gelation of poly(urethane–amide) networks which upon pyrolysis yield monolithic N-doped amorphous carbon/reduced GO (rGO) aerogels. Here GO plays a significant multifunctional role of (i) inducing the gelation of poly(urethane–amide) networks; and (ii) tailoring the physical properties of N-doped amorphous carbon–rGO aerogels. The resulting aerogels were characterized by X-ray diffraction (XRD), N₂ sorption porosimetry, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), Fourier-transform Raman spectroscopy (FT-Raman), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM) which support the formation of a highly porous carbon/rGO network. Importantly, the obtained N-doped amorphous carbon/rGO aerogels (0.76 wt% of GO) are electrically conducting with a pore volume, pore diameter and surface area of 0.39 cm³ g⁻¹ (69% mesopores), 36 nm and 260 m² g⁻¹ respectively. The significantly enhanced specific capacitance is derived from the tailored 3-D mesoporous structure of the N-doped amorphous carbon/rGO aerogels which consist of large pore volumes and a predominant number of accessible mesopores allowing a low resistance path for inward and outward diffusion of electrolyte ions and endowing a high charge storage capability resulting in a superior specific capacitance of 260 F g⁻¹. The nanoporous networks in the as-prepared N-doped amorphous carbon/rGO serve as channels for quick ionic and electronic conduction. In addition to the enhanced physical properties achieved by addition of a minimal amount of GO, the increased specific capacitance can also be credited to the effective N-doping in ACGA-2 resulting in alteration of the electronic structure of rGO with an increase in charge carrier density, and modification of interfacial and quantum capacitance.