Water-Dispersed High-Quality Graphene: A Green Solution for Efficient Energy Storage Applications

Abstract

Graphene has been the subject of widespread research during the last decade because of its outstanding physical properties which make it an ideal nanoscale material to investigate fundamental properties. Such unique characteristics promote graphene as a functional material for the emergence of new disruptive technologies. Yet, to impact our daily-life products and devices, high-quality graphene needs to be produced in large quantities, using an environmentally-friendly protocol. In this context, the production of graphene which preserves its outstanding electronic properties using a green chemistry approach remains a key challenge. 2 Herein, we demonstrate an efficient electrochemical approach to obtain water-dispersed highquality graphene nanosheets. High-frequency (terahertz) conductivity measurements of the graphene nanosheets reveal high charge carrier mobility up to 1000 cm-2 V-1 s-1. The fine water dispersibility enables versatile functionalization of graphene, as demonstrated by the pseudocapacitive polydopamine coating of graphene nanosheets. Remarkably, the polydopamine functionalization causes a modest, i.e. 20%, reduction of charge carrier mobility. Thin film electrodes based on such hybrid materials for micro-supercapacitors exhibit excellent electrochemical performance, namely high volumetric capacitance of 340 F cm-3 and power density of 1000 W cm-3 , thus outperforming most of the reported graphene-based microsupercapacitors. These results highlight the potential for water-dispersed, high-quality graphene nanosheets as a novel materials platform for energy storage applications.

Emerging 2D Materials Produced via Electrochemistry

“…Especially, sodium chloride (0.05 m ) led to single/few‐layer graphene sheets with an average thickness of 2–3 nm, an I D / I G ratio of 0.8, and high C/O ratio of 16.7. Very recently, Liu et al found that alkaline electrolyte (pH = 13) composed of 0.1 m NaOH/Na 2 SO 4 mixture was very efficient to produce bilayer‐rich water‐dispersible graphene . The exfoliated sheets exhibit excellent charge transport properties, evidenced by a high mobility up to 1000 cm 2 V −1 s −1 based on the tetrahertz (THz) spectroscopy characterization.…”

Understanding Oxygen Bubble‐Triggered Exfoliation of Graphite Toward the Low‐Defect Graphene

“…[ 21,23,35 ] The stable D peak shows that only few defects are produced during the exfoliation process. [ 36 ] Compared to I 2D /I G ratio of chemical reduced graphene oxide and electrochemically efoliated graphene, [ 37 ] the value, ≈0.96, exhibits less defects in GNPs in this study. As shown in Figure 2e, I 2D /I G , 0.76, and I D /I G , 0.38, of GNPs‐20 after dispersion, demonstrates that the defects are formed in the post‐treatment process.…”

Recent Studies on Dispersion of Graphene–Polymer Composites

“…An activated water-based graphene dispersion with graphene concentration of about 20 mg/mL used as an electrode provided a specific capacitance value of 180 F/g at a specific current of 1 A/g [ 209 ]. High quality water-dispersed graphene with dopamine was used for energy storage applications [ 210 ]. rGO with PANI is used as an electrode material in supercapacitors [ 211 ].…”