期刊
ACS NANO
卷 8, 期 9, 页码 9073-9080出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn5024544
关键词
graphene; liquid crystal; doping; oxygen reduction reaction; catalyst
类别
资金
- Institute for Basic Science (IBS) [IBS-R004-G1-2014-a00]
- Asian Office of Aerospace Research and Development (AOARD) [AOARD-14-1403]
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 mu 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 (-0.08 V) for oxygen reduction catalysis, signifying that quaternary N-dopants serve as principal catalytic sites in N-doped graphene.
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