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Synthesis of Edge-Selectively Functionalized Graphene Nanoplatelets and Its Application

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Title
Synthesis of Edge-Selectively Functionalized Graphene Nanoplatelets and Its Application
Author
Jeon, In-Yup
Advisor
Baek, Jong-Beom
Issue Date
2013-02
Publisher
Graduate School of UNIST
Abstract
I contrived a new method that was named edge-functionalized graphite (EFG). Unlike chemical oxidation method, this method can functionalize only an edge of graphite as it can retains superb properties of graphite. The new edge-functionalization was divided into two groups. One is to use organic wedges via Friedel-Crafts acylation reaction with poly(phosphoric acid) (PPA)/phosphorous pentoxide (P2O5) medium. There are wedges of organic materials such as organic molecule, linear macromolecular, dendritic macromolecular. The resultant showed an improved dispersibility in various common organic solvents because of organic wedges. And also, EFG could become films form via a simply heat-treatment. That was nitrogen doped graphene films to display outstanding electrocatalytic activity for oxygen reduction reaction (ORR). The other is to use a mechano-chemical cracking via ball milling. Graphite was broken by force energy of metal ball and broken graphite was functionalized with organic material and then exfoliated into graphene. The resultant is highly dispersible in various solvents to self-exfoliate into single- and few-layer (≤5 layers) graphene nanosheets (GNs). This method is effective, and eco-friendly, edge functionalization of graphite without the basal plane oxidation by ball milling. Therefore, the newly developed ball milling approach, involving neither hazardous chemicals nor tedious procedures, outperforms current processes for mass production of high-quality graphene nanosheets (GNs) at an unprecedented low cost. The resultants (EFGnPs) were also used as electrocatalysts for ORR in an alkaline electrolyte. It was found that the edge polar nature of the newly prepared EFGnPs without heteroatom doping into their basal plane played an important role in regulating the ORR efficiency with the electrocatalytic activity in the order of SGnP > CSGnP > CGnP > HGnP > pristine graphite. More importantly, the sulfur-containing SGnP and CSGnP were found to have a superior ORR performance to commercially available platinum-based electrocatalyst.
Description
Energy Conversion & Storage
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