title: Nitrogen-doped graphene for high-performance ultracapacitors and the importance of nitrogen-doped sites at basal planes.
abstract: Although various carbon nanomaterials including activated carbon, carbon nanotubes, and graphene have been successfully demonstrated for high-performance ultracapacitors, their capacitances need to be improved further for wider and more challenging applications. Herein, using nitrogen-doped graphene produced by a simple plasma process, we developed ultracapacitors whose capacitances (∼280 F/g(electrode)) are about 4 times larger than those of pristine graphene based counterparts without sacrificing other essential and useful properties for ultracapacitor operations including excellent cycle life (>200,000), high power capability, and compatibility with flexible substrates. While we were trying to understand the improved capacitance using scanning photoemission microscopy with a capability of probing local nitrogen-carbon bonding configurations within a single sheet of graphene, we observed interesting microscopic features of N-configurations: N-doped sites even at basal planes, distinctive distributions of N-configurations between edges and basal planes, and their distinctive evolutions with plasma duration. The local N-configuration mappings during plasma treatment, alongside binding energy calculated by density functional theory, revealed that the origin of the improved capacitance is a certain N-configuration at basal planes.
authors: Department of Materials Science and Engineering, Korea Advanced Institute of Science & Technology, 373-1, Guseong Dong, Yuseong Gu, Daejeon 305-701, Republic of Korea.
authors: Hyung Mo
authors: HM
authors: Jeong
authors: Jung Woo
authors: JW
authors: Lee
authors: Weon Ho
authors: WH
authors: Shin
authors: Yoon Jeong
authors: YJ
authors: Choi
authors: Hyun Joon
authors: HJ
authors: Shin
authors: Jeung Ku
authors: JK
authors: Kang
authors: Jang Wook
authors: JW
authors: Choi