Chemically reduced graphene oxide/chitosan hybrid; a nanoscale “Fabric Starch”

Abstract

This work reports on the formation of reduced graphene oxide/chitosan, RGO/CS, (0.1–10 wt%) hybrids via L-ascorbic acid reduction of GO-CS aqueous suspensions. Hybrids at different synthesis steps and the constituent modifications are characterized by microstructural, spectroscopic and physical methods. CS undergoes chemical-structural changes, both by interaction with GO and in the course of the chemical reduction, so that eventually, whilst there is no evidence of CS presence in the final product, we find convincing proof of its transformation to a starch-like phase via a critical examination of XRD and ATR-FTIR analysis. Hybrids show significant modifications of morphology, pore texture, apparent surface area, conductivity, and packing density vs. the pristine RGO. We elucidate more subtle effects, affecting stacking and packing behavior, by examining the capacitive storage behavior of hybrid electrodes. The electrochemical study highlights, at the best composition, a remarkable enhancement of specific/volumetric capacitance (up to 30% and 90% increase, respectively) and of rate behavior, compared to pure RGO. Overall, we show that the functioning of CS in hybrid formation can be explained through the reactive attachment of CS molecules onto RGO sheets, forming a starch-like phase, which stiffens graphene layers mitigating crumpling, and allowing a denser packing without re-stacking.