Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface
Molecular dynamics simulations are carried out to investigate the structure and capacitance of the electrical double layers (EDLs) at the interface of vertically oriented graphene and ionic liquids [EMIM]+/[BF4]−. The distribution and migration of the ions in the EDL on the rough and non-rough elect...
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MDPI AG
2017-09-01
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| Online Access: | https://www.mdpi.com/2076-3417/7/9/939 |
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| author | Pengfei Lu Qiaobo Dai Liangyu Wu Xiangdong Liu |
| author_facet | Pengfei Lu Qiaobo Dai Liangyu Wu Xiangdong Liu |
| author_sort | Pengfei Lu |
| collection | DOAJ |
| description | Molecular dynamics simulations are carried out to investigate the structure and capacitance of the electrical double layers (EDLs) at the interface of vertically oriented graphene and ionic liquids [EMIM]+/[BF4]−. The distribution and migration of the ions in the EDL on the rough and non-rough electrode surfaces with different charge densities are compared and analyzed, and the effect of the electrode surface morphology on the capacitance of the EDL is clarified. The results suggest that alternate distributions of anions and cations in several consecutive layers are formed in the EDL on the electrode surface. When the electrode is charged, the layers of [BF4]− anions experience more significant migration than those of [EMIM]+ cations. These ion layers can be extended deeper into the bulk electrolyte solution by the stronger interaction of the rough electrode, compared to those on the non-rough electrode surface. The potential energy valley of ions on the neutral electrode surface establishes a potential energy difference to compensate the energy cost of the ion accumulation, and is capable of producing a potential drop across the EDL on the uncharged electrode surface. Due to the greater effective contact area between the ions and electrode, the rough electrode possesses a larger capacitance than the non-rough one. In addition, it is harder for the larger-sized [EMIM]+ cations to accumulate in the narrow grooves on the rough electrode, when compared with the smaller [BF4]−. Consequently, the double-hump-shaped C–V curve (which demonstrates the relationship between differential capacitance and potential drop across the EDL) for the rough electrode is asymmetric, where the capacitance increases more significantly when the electrode is positively charged. |
| first_indexed | 2024-04-13T01:45:06Z |
| format | Article |
| id | doaj.art-5ef00cd179d24a129403412a64355916 |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-04-13T01:45:06Z |
| publishDate | 2017-09-01 |
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| spelling | doaj.art-5ef00cd179d24a129403412a643559162022-12-22T03:08:04ZengMDPI AGApplied Sciences2076-34172017-09-017993910.3390/app7090939app7090939Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid InterfacePengfei Lu0Qiaobo Dai1Liangyu Wu2Xiangdong Liu3School of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225127, ChinaSchool of Energy and Environment, Southeast University, Nanjing 210096, ChinaSchool of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225127, ChinaSchool of Hydraulic, Energy and Power Engineering, Yangzhou University, Yangzhou 225127, ChinaMolecular dynamics simulations are carried out to investigate the structure and capacitance of the electrical double layers (EDLs) at the interface of vertically oriented graphene and ionic liquids [EMIM]+/[BF4]−. The distribution and migration of the ions in the EDL on the rough and non-rough electrode surfaces with different charge densities are compared and analyzed, and the effect of the electrode surface morphology on the capacitance of the EDL is clarified. The results suggest that alternate distributions of anions and cations in several consecutive layers are formed in the EDL on the electrode surface. When the electrode is charged, the layers of [BF4]− anions experience more significant migration than those of [EMIM]+ cations. These ion layers can be extended deeper into the bulk electrolyte solution by the stronger interaction of the rough electrode, compared to those on the non-rough electrode surface. The potential energy valley of ions on the neutral electrode surface establishes a potential energy difference to compensate the energy cost of the ion accumulation, and is capable of producing a potential drop across the EDL on the uncharged electrode surface. Due to the greater effective contact area between the ions and electrode, the rough electrode possesses a larger capacitance than the non-rough one. In addition, it is harder for the larger-sized [EMIM]+ cations to accumulate in the narrow grooves on the rough electrode, when compared with the smaller [BF4]−. Consequently, the double-hump-shaped C–V curve (which demonstrates the relationship between differential capacitance and potential drop across the EDL) for the rough electrode is asymmetric, where the capacitance increases more significantly when the electrode is positively charged.https://www.mdpi.com/2076-3417/7/9/939ionic liquidvertically oriented grapheneelectrical double layerscharge densitycapacitance |
| spellingShingle | Pengfei Lu Qiaobo Dai Liangyu Wu Xiangdong Liu Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface Applied Sciences ionic liquid vertically oriented graphene electrical double layers charge density capacitance |
| title | Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface |
| title_full | Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface |
| title_fullStr | Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface |
| title_full_unstemmed | Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface |
| title_short | Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface |
| title_sort | structure and capacitance of electrical double layers at the graphene ionic liquid interface |
| topic | ionic liquid vertically oriented graphene electrical double layers charge density capacitance |
| url | https://www.mdpi.com/2076-3417/7/9/939 |
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