| 초록 |
Graphene oxide is mass productive, water soluble two dimensional materials, which is promising for various applications. Because most of its bulk property is limited by its small flake size, introducing larger flake has widely studied. However, top-down synthesis method inevitably produces broad size range of graphene oxide. Here, we introduce a simple size selection method by liquid crystal property of graphene oxide. In specific concentration range, flakes less than 5 μm is spontaneously phase separated into isotropic phase while larger flakes with high aspect ratio remain in nematic phase. After discarding upper isotropic phase, separated large graphene oxide (sLGO) can be achieved. Nitrogen dopant type is highly dependent on size distribution of flakes. Quaternary dominant nitrogen doped sLGO film shows the lowest onset potential (-0.09V) on oxygen reduction reaction, indicating quaternary nitrogen as a major catalytic active site for oxygen reduction reaction. |
