State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, College of Energy Engineering, Zhejiang University, Hangzhou, Zhejiang Province, 310027, China.
Sci Rep. 2016 Dec 21;6:39689. doi: 10.1038/srep39689.
Graphene film has been demonstrated as promising active materials for electric double layer capacitors (EDLCs), mainly due to its excellent mechanical flexibility and freestanding morphology. In this work, the distribution and variation pattern of electrolyte ions in graphene-film based EDLC electrodes are investigated with a B magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. For neutral graphene films soaked with different amounts of electrolytes (1 M TEABF/ACN), weakly and strongly adsorbed anions are identified based on the resonances at different B chemical shifts. Unlike other porous carbonaceous materials, the strongly adsorbed anions are found as the major electrolyte anions components in graphene films. Further measurements on the ion population upon charging are carried out with applying different charging voltages on the graphene films. Results indicate that the charging process of graphene-film based EDLCs can be divided into two distinct charge storage stages (i.e., ejection of co-ions and adsorption of counter-ions) for different voltages. The as-obtained results will be useful for the design and fabrication of high performance graphene-film based EDLCs.
石墨烯薄膜因其优异的机械柔韧性和独立形态，已被证明是一种很有前途的双电层电容器（EDLC）的活性材料。在这项工作中，采用 B 魔角旋转核磁共振（MAS-NMR）光谱研究了基于石墨烯薄膜的 EDLC 电极中电解质离子的分布和变化模式。对于浸泡在不同电解质（1M TEABF/ACN）量的中性石墨烯薄膜，根据不同 B 化学位移处的共振，确定了弱吸附和强吸附阴离子。与其他多孔碳质材料不同，强吸附阴离子被发现是石墨烯薄膜中主要的电解质阴离子成分。通过在石墨烯薄膜上施加不同的充电电压，进一步测量了充电时的离子数量。结果表明，对于不同的电压，基于石墨烯薄膜的 EDLC 的充电过程可以分为两个不同的电荷存储阶段（即，共离子的逐出和反离子的吸附）。所得结果将有助于设计和制造高性能的基于石墨烯薄膜的 EDLC。
