Liquid Crystal Size Selection of Large-Size Graphene Oxide for Size-Dependent N-Doping and Oxygen Reduction Catalysis

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• 作者：Kyung Eun Lee ; Ji Eun Kim ; Uday Narayan Maiti ; Joonwon Lim ; Jin Ok Hwang ; Jongwon Shim ; Jung Jae Oh ; Taeyeong Yun ; Sang Ouk Kim
• 刊名：ACS Nano
• 出版年：2014
• 出版时间：September 23, 2014
• 年：2014
• 卷：8
• 期：9
• 页码：9073-9080
• 全文大小：576K
• ISSN：1936-086X

文摘

Graphene oxide (GO) is aqueous-dispersible oxygenated graphene, which shows colloidal discotic liquid crystallinity. Many properties of GO-based materials, including electrical conductivity and mechanical properties, are limited by the small flake size of GO. Unfortunately, typical sonochemical exfoliation of GO from graphite generally leads to a broad size and shape distribution. Here, we introduce a facile size selection of large-size GO exploiting liquid crystallinity and investigate the size-dependent N-doping and oxygen reduction catalysis. In the biphasic GO dispersion where both isotropic and liquid crystalline phases are equilibrated, large-size GO flakes (>20 渭m) are spontaneously concentrated within the liquid crystalline phase. N-Doping and reduction of the size-selected GO exhibit that N-dopant type is highly dependent on GO flake size. Large-size GO demonstrates quaternary dominant N-doping and the lowest onset potential (鈭?.08 V) for oxygen reduction catalysis, signifying that quaternary N-dopants serve as principal catalytic sites in N-doped graphene.

Keywords:

graphene; liquid crystal; doping; oxygen reduction reaction; catalyst