title: Interaction between nitrogen and sulfur in co-doped graphene and synergetic effect in supercapacitor.
abstract: The co-doping of graphene with nitrogen and sulfur was investigated aiming at understanding their interactions with the presence of oxygen in graphene. The co-doped graphene (NS-G) was synthesized via a one-pot hydrothermal route using graphene oxide as starting material and L-cysteine, an amino acid containing both N and S, as the doping agent. The obtained NS-G with a three-dimensional hierarchical structure containing both macropores and mesopores exhibited excellent mechanical stabilities under both wet and dry conditions. As compared to N or S singly doped graphene, the co-doped sample contains significantly higher concentrations of N and S species especially pyrollic N groups. The co-doped sample considerably outperformed the singly doped samples when used as free-standing electrode in supercapacitors due to enhanced pseudocapacitance. The simultaneous incorporation of S and N species with the presence of oxygen significantly modified the surface chemistry of carbon leading to considerably higher doping levels, although directly bonding between N and S is neither likely nor detected. Hence, the synergetic effect between N and S occurred through carbon atoms in neighboring hexagonal rings in a graphene sheet.
authors.affiliation: Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, 830046 Xinjiang, P. R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.affiliation: Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, 830046 Xinjiang, P. R. China.
authors.forename: Lu-Xiang
authors.initials: LX
authors.lastname: Wang
authors.affiliation: Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, 830046 Xinjiang, P. R. China.
authors.forename: Dong-Ling
authors.initials: DL
authors.lastname: Wu
authors.affiliation: Laboratory of Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum, Germany.
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.affiliation: Key Laboratory of Material and Technology for Clean Energy, Ministry of Education, Key Laboratory of Advanced Functional Materials, Autonomous Region, Institute of Applied Chemistry, Xinjiang University, 830046 Xinjiang, P. R. China.
authors.forename: Dian-Zeng
authors.initials: DZ
authors.lastname: Jia