Bipolar exfoliation and in-situ deposition of high-quality reduced graphene

Abstract

Commercially-available graphene/graphene oxide (GO) materials are mostly produced based on top-down wet chemical and/or electrochemical approaches for (i) exfoliation of GO from graphite sources and (ii) reduction of exfoliated GO into graphene or reduced graphene oxide (rGO). In the wet chemical processes such as Hummers method and modified Hummers method, strong oxidizing agents in a strong acidic medium are typically used for the production of GO, and strong reducing agents are typically used for the formation of rGO. These sets of reactions can introduce relatively high amounts of defects into the rGO sheets and produce toxic chemicals. The majority of commercially-available materials are actually graphite microplates with less than 10% graphene content, and none of the samples have more than 50% graphene content. On the other hand, the electrochemical techniques have been increasingly employed in graphene mass production with the advantages of high production yield of relatively high purity products in simple and cost-effective ways. The electrochemical approaches are typically based on intercalating molecules or charged ions between the graphene layers of a graphite electrode to facilitate the exfoliation and collection of the graphene nanosheets from the solution. Although the anodic approach is more common due to the higher efficiency of intercalation and expansion, the cathodic exfoliation is more desired in order to avoid unwanted chemical functionalization and damage to the graphite basal plane that occur during the anodic exfoliation.The FIU invention uses bipolar electrochemistry (BPE) to provide a single-step and controllable process for simultaneously exfoliating a graphite source and depositing both graphene oxide and reduced graphene oxide layers on conductive substrates. A bipolar electrochemical cell is used for a three-in-one deposition and can include two wired pieces of graphite to monitor the amount of current that passes through the bipolar electrode. Upon the application of the direct current (DC) voltage across the feeding electrodes, several electrochemical processes take place, resulting in a three-in-one in situ exfoliation, reduction, and deposition in a single step and in an environmental friendly manner to directly form functional graphene-based electrodes.

Benefit

· Fabrication of high-quality graphene · Economical, safe, and easy to control · Environmentally friendly compared to existing methods · Assist in mass production of graphene-based devices

Market Application

Energy storage, optical and electronic devices, sensors for biomedical applications.

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