Super-tough MXene-functionalized graphene sheets

Tianzhu Zhou,Antoni P Tomsia,Mingzhu Li,Ray H Baughman,Lei Jiang,Eduardo Saiz,Qunfeng Cheng,Yanlei Wang,Chao Wu,Shaoli Fang

doi:10.1038/s41467-020-15991-6

Abstract

Flexible reduced graphene oxide (rGO) sheets are being considered for applications in portable electrical devices and flexible energy storage systems. However, the poor mechanical properties and electrical conductivities of rGO sheets are limiting factors for the development of such devices. Here we use MXene (M) nanosheets to functionalize graphene oxide platelets through Ti-O-C covalent bonding to obtain MrGO sheets. A MrGO sheet was crosslinked by a conjugated molecule (1-aminopyrene-disuccinimidyl suberate, AD). The incorporation of MXene nanosheets and AD molecules reduces the voids within the graphene sheet and improves the alignment of graphene platelets, resulting in much higher compactness and high toughness. In situ Raman spectroscopy and molecular dynamics simulations reveal the synergistic interfacial interaction mechanisms of Ti-O-C covalent bonding, sliding of MXene nanosheets, and π-π bridging. Furthermore, a supercapacitor based on our super-tough MXene-functionalized graphene sheets provides a combination of energy and power densities that are high for flexible supercapacitors.

Highlights

Flexible reduced graphene oxide sheets are being considered for applications in portable electrical devices and flexible energy storage systems
The fabrication of a free-standing MrGO-AD sheet is schematically illustrated in Supplementary Fig. 1
Our obtained MXene nanosheets show the expected hexagonal structure for the basal planes, high crystallinity, and the absence of nanometer-scale defects that are noticeable in high-resolution transmission electron microscopy (HR-TEM) images and selected-area electron diffraction patterns (Supplementary Fig. 6)

Summary

Results

Synthesis and characterization of the graphene sheet. The fabrication of a free-standing MrGO-AD sheet is schematically illustrated in Supplementary Fig. 1. Elemental mapping spectra by energy-dispersive spectroscopy (for C, O, Ti, and N) in the cross-section of a MrGO-AD sheet show uniform distribution of long-chain AD molecules and MXene nanosheets (Supplementary Fig. 9). These results further confirm that the MXene nanosheets have been successfully introduced within the layers of rGO platelets. Since this scattering increases with increasing MXene content and since the scattering contribution from a MXene layer is much greater than from a rGO layer, we assume that this scattering is due to various localized regions in which one or more MXene layers are associated with rGO layers

D G MrGO-AD

Discussion

Methods