An aqueous cathodic delamination route towards high quality graphene flakes for oil sorption and electrochemical charge storage applications

Abstract

The electrochemical exfoliation of graphite in aqueous medium stands out as an attractive, scalable approach for the production of graphenes for different applications, due to its simplicity, cost-effectiveness and environmental friendliness. In particular, cathodic exfoliation in water should allow access to high quality, non-oxidized graphene flakes, as it avoids the intrinsic oxidizing conditions that typically plague the anodic route, but this possibility has been limited by a poor intercalation ability of aqueous cations. Here, we demonstrate that with a proper choice of starting graphite and electrolyte, high quality graphene flakes can be obtained in substantial yields via cathodic delamination in water. Graphites having some pre-expanded edges and interlayer voids (e.g., graphite foil) were found to be critical for a successful exfoliation.Large differences in the efficiency of a range of aqueous quaternary ammonium-based electrolytes were observed, quantitatively compared and rationalized on the basis of their chemical structure. Graphene yields up to 40-50 wt% were attained with the most efficient cations (tetrapropylammonium and hexyltrimethylammonium). Hydrophobic sponges made up of cathodic graphene-coated melamine foam exhibited a notable capacity towards the sorption of oils and organic solvents from water with good reusability. Hybrids comprised of cathodically exfoliated graphite and a small amount of vertically oriented cobalt oxide nanosheets displayed good electrochemical charge storage behavior. Overall, the ability to access graphene flakes in considerable yields by the aqueous cathodic route disclosed here should raise the prospects of cathodic exfoliation as a competitive method for the industrial manufacturing of high quality graphene for practical applications.

Fast Synthesis of Graphene Oxide−β-Lactam as a Residue-Free Environmental Bacterial Inhibitor

“…The first step was electrochemical exfoliating graphite into GO sheets using low voltage and low current with Cl 2 as the oxidant. 18 The ketene groups on GO with ketenyl stretching appeared at 2100−2200 cm −1 in the infrared spectra. GOβL was obtained by reacting ketene and azomethine-H in the second step via a [2 + 2] cycloaddition reaction.…”

“…GOβL was prepared using a rapid method. The first step was electrochemical exfoliating graphite into GO sheets using low voltage and low current with Cl 2 as the oxidant . The ketene groups on GO with ketenyl stretching appeared at 2100–2200 cm –1 in the infrared spectra.…”

Easy and Support-Free Synthesis of Bimetallic Borates for Boosting the Oxygen Evolution Reaction

“…The oxidative conditions in the OER experiments generate a slight modification of the surface chemistry of Ni@CoB i . This effect is probably produced by the intercalation of the electrolyte into the material, which generates a higher exposed area and increases the gravimetric capacitance . In addition, the Faradaic efficiency of all materials was studied and is shown in Figure S13.…”

Simultaneous Anodic and Cathodic Exfoliation of Graphite Electrodes in an Aqueous Solution of Inorganic Salt

“…The positive bias voltage at the anode results in water oxidation producing O 2 gas and associated oxygen radicals, hence oxygen containing groups with C−O bonds are typically evident in this graphene [12d,16] . In contrast, the cathodic bias voltage at graphite cathode is a reductive process that is not expected to introduce additional oxygen functionalities in cathodic exfoliated graphene [15,17] . Upon applying a sufficiently high negative potential, intercalation of K + occurs.…”

“…[12d,16] In contrast, the cathodic bias voltage at graphite cathode is a reductive process that is not expected to introduce additional oxygen functionalities in cathodic exfoliated graphene. [15,17] Upon applying a sufficiently high negative potential, intercalation of K + occurs. The essential role of K + in the intercalation process is evident since it needs to be sufficiently high in concentration (at least 0.4 M K 2 SO 4 , Figure S2b), and potential of À 4 V to enable exfoliation (Figure S1).…”