Mechanically-Assisted Electrochemical Production of Graphene Oxide

Abstract

Graphene oxide (GO) is promising for a variety of applications due to its excellent dispersibility and processability. However, current chemical oxidation routes have several drawbacks, including the use of explosive oxidizing agents, residual metal ions contaminations, and the creation of irreparable hole defects on the GO sheet. The electrochemical exfoliation and oxidation of graphite is a potentially greener approach without the need for extensive purification steps. Most reported electrochemical methods employ a single preformed bulk graphite as electrode, which limits their scalability, reproducibility, and degree of oxidation. Herein, we reported a novel mechanically assisted electrochemical method to produce graphene oxide directly from graphite flakes. The electrochemically derived graphene oxide (EGO) shows a good degree of oxidation but with less physical defects than chemically derived graphene oxide (CGO). EGO has good dispersibility in water and various solvents and, in particular, displays better long-term stability in ethanol when compared with CGO. Notably, unlike conventional CGO, EGO can undergo facile thermal conversion at 200 °C in air to conductive thermally processed EGO, which is highly desirable for heat/chemical-sensitive applications.

Emerging 2D Materials Produced via Electrochemistry

“…The expanded graphitic flakes often drop off from the graphite electrodes in prior to the complete oxidation, leading to GO sheets with variable density of oxide groups from batch to batch. In 2016, Yu et al improved the anodic oxidation of graphite flakes in a confined metal mesh, using a mixture of 1.0 m H 2 SO 4 and saturated (NH 4 ) 2 SO 4 solution as electrolyte . The as‐prepared GO sheets displayed long‐term dispersibility in water, DMF, isopropyl alcohol and ethanol at high concentrations over 2.0 mg mL −1 .…”

Graphene Platelets and Their Polymer Composites: Fabrication, Structure, Properties, and Applications

“…c 1 ) Schematic and photographs of c 2 ) side view and c 3 ) top view of a mechanically assisted electrochemical exfoliation. (c 1 –c 3 ) Reproduced with permission . Copyright 2016, American Chemical Society.…”

“…A purpose‐designed mechanical process in an electrochemical reaction can relocate graphite flakes toward the working electrode, providing continual physical contact between graphite and the electrode. For example, Yu et al reported a mechanical‐assisted electrochemical exfoliation method that produced 66% monolayer graphene oxide . The experimental setup is shown in Figure c: graphite flakes connected with a titanium mesh as an electrode were placed inside a cylindrical tube as the working electrode.…”

Scalable Production of Graphene Oxide Using a 3D-Printed Packed-Bed Electrochemical Reactor with a Boron-Doped Diamond Electrode

“…AFM revealed that the majority of the graphene was exfoliated to a single layer, typically 1−1.2 nm thick, consistent with literature reports for CGO and EGO ( Figures 4A,C and S13A). 17,20,26 Mechanism of EGO Formation in the PBER. In order to better understand the mechanism of EGO formation in the PBER, the reaction in the tubular glass reactor was stopped approximately halfway through (i.e., after 11 h instead of the full 22.5 h).…”

“…To address this, we have previously reported a mechanically assisted production of EGO directly from loose graphite flakes, but that approach had a limited yield of ∼37% with respect to the starting graphite. 26 A second limitation/unanswered question surrounding the electrochemical approaches is their scalability. In past reports, the diameter of the starting graphite rod or thickness of the foil is usually held constant at a small scale without upscaling.…”