Advanced investigations on the solid-liquid interaction between rGO films and aqueous electrolytes
Résumé
Reduced graphene oxide (rGO) has been studied in the recent years in different fields due a
combination of physicochemical properties which can be engineered to prepare films exhibiting large
electroactive surface area and high electrical conductivity. In the field of healthcare applications, rGO
films have been widely studied because of their biocompatibility and their chemical and biochemical
sensing capabilities [1]. In this respect, a fundamental understanding of key aspects such as the
evolution of the functional groups of rGO during the reduction process and the role of ionic diffusion
remains extremely relevant because their impact on the properties and the ultimate performance of
rGO-based devices.
In this work, combining different electrochemical as well as other spectroscopy techniques, we
investigate the solid-liquid interaction between rGO-based porous electrodes and aqueous electrolytes
containing a variety of ionic species (Li+, K+, Na+ and Cs+) as well as to evaluate the impact of the
reduction degree of the film on the ionic diffusion and kinetics. A combination of X-ray photoelectron
spectroscopy (XPS), contact angle, and Raman spectroscopy was used to characterize the evolution
of functional groups upon the reduction degree of rGO [2]. Using scanning electron microscope
(SEM) and quartz crystal microbalance with dissipation monitoring (QCM-D) we investigate
parameters such as roughness and distance between the stacked rGO flakes in the porous films. The
electrochemical properties of rGO are evaluated by cyclic voltammetry (CV) coupled with
electrochemical quartz crystal microbalance (EQCM) techniques. To study the dynamics of the ionic
transfer (charge and solvation effects) across the electrode-electrolyte interfaces we use the ACEQCM
technique. This technique combines electrochemical impedance spectroscopy (EIS) and fast
quartz crystal microbalance (QCM) to separate the contribution of different ionic species, thus
complementing the classical EQCM results [3]. This work aims at expanding the current
understanding of the properties of rGO-based porous films for their potential use as electrode material
in healthcare and energy storage applications.