title: Sandwich-like nitrogen-doped porous carbon/graphene nanoflakes with high-rate capacitive performance.
abstract: Sandwich-like nitrogen-doped porous carbon/graphene nanoflakes (NPCFs) are prepared via a two-step approach, firstly by using in situ polymerization of pyrrole (Py) on the surface of graphene oxide (GO) and then by KOH activation under an Ar atmosphere. As the shape-directing agent and conductive matrix, graphene sheets play an important role in enhancing NPCFs' electrochemical performance. The NPCFs exhibit high specific surface area (2502 m(2) g(-1)), short ion diffusion path (ca. 30 nm), high conductivity (72 S m(-1)) and a considerable nitrogen level (6.3 wt%). These intriguing features render NPCFs a promising electrode material for electrochemical supercapacitors, which displays high specific capacitance (341 F g(-1)), excellent rate capability (over 71% retention ratio at 50 A g(-1)) and outstanding cycling stability (almost no capacitance loss after 2000 cycles) in a 30 wt% KOH aqueous electrolyte. Besides, the assembled symmetrical supercapacitor delivers a high gravimetric energy density of 11.3 Wh kg(-1) in an aqueous electrolyte and 66.4 Wh kg(-1) in an organic electrolyte.
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, China. xingwei@upc.edu.cn.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory for Heavy Oil Processing, PetroChina, Key Laboratory of Catalysis, China University of Petroleum, Qingdao 266580, China. zfyancat@upc.edu.cn.
authors.forename: Binglin
authors.initials: B
authors.lastname: Tao
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, China. xingwei@upc.edu.cn and State Key Laboratory for Heavy Oil Processing, PetroChina, Key Laboratory of Catalysis, China University of Petroleum, Qingdao 266580, China. zfyancat@upc.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Xing
authors.affiliation: School of Chemical Engineering, University of Adelaide, Adelaide SA 5005, Australia.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.affiliation: School of Science, China University of Petroleum, Qingdao 266580, China. xingwei@upc.edu.cn.
authors.forename: Qingzhong
authors.initials: Q
authors.lastname: Xue
authors.affiliation: State Key Laboratory for Heavy Oil Processing, PetroChina, Key Laboratory of Catalysis, China University of Petroleum, Qingdao 266580, China. zfyancat@upc.edu.cn.
authors.forename: Zifeng
authors.initials: Z
authors.lastname: Yan