Understanding Electric Field‐Dependent Structure Variation of Functional Ionic Liquids at the Electrode Interface

Qin, Jingyu; Wang, Mi; Wang, Yanlei; Wang, Chenlu; Lu, Yunliang; Huo, Feng; He, Hongyan

doi:10.1002/celc.202100135

Cited by 8 publications

(6 citation statements)

References 55 publications

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“…Considering the practical applications, the confined ILs always exist and play a predominant role because of the wide existence of nanochannel and nanospace within the solid catalysts or the electrodes. − The nanoscale confinement could greatly affect the structure and dynamic properties of ILs and other liquid compared with those in the bulk one. − For example, ILs can assemble to monolayer, bilayer, and sandwich structure in the two-dimensional (2D) bilayer graphene nanochannel (BLGC), and the self-diffusive coefficient can be decreased noticeably . As the size of BLGC decreases, the conformational entropy and free energy of ILs demonstrate a nonmonotonic behavior, showing the complex structure change of the confined ILs .…”

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confidence: 99%

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

Wang

et al. 2021

J. Phys. Chem. Lett.

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Revealing the structure and behavior of confined ionic liquids (ILs) is essential for their applications in green chemical processes. Here, we explore the electroconductivity (σ) and ionic correlation of imidazole ILs confined in graphene nanochannels via joint molecular dynamics simulation and theoretical analysis. The ideal and actual σ of ILs are first calculated, showing a growing tendency and up to the bulk value as the nanochannel size ranges from 1 to 10 nm. To account for the ionic correlation, the ionicity was determined by the ratio of the actual to ideal σ, reflecting the average fraction of free ions in the confined ILs. Amazingly, the ionicity of all three ILs shows an abnormal changing tendency, which first increases and reaches the maximum at 2 nm and then decreases to the bulk value. The conformational analysis, pair dissociating energy, and residence time are further obtained, proving that the abnormal enhanced ionicity should be attributed to the structure reconstruction of ILs near the graphene wall. The analytical model of ionicity herein can guide the rational design of efficient IL-based nanoporous electrodes and solid catalysts.

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confidence: 99%

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

Wang

et al. 2021

J. Phys. Chem. Lett.

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“… [11a] In addition to our own results, unusual assemblies of nonpolar fragments of ILs at electrified interfaces have recently been observed experimentally[ 2a , 6c , 29 ] and predicted in molecular dynamics calculations. [ 2a , 2b , 7b ]…”

Section: Resultsmentioning

confidence: 99%

CD Stretching Modes are Sensitive to the Microenvironment in Ionic Liquids

Sieling

Petersen

Alpers

et al. 2021

Chemistry A European J

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Knowledge of the structure of the electrical double layer in ionic liquids (IL) is crucial for their applications in electrochemical technologies. We report the synthesis and applicability of an imidazolium-based amphiphilic ionic liquid with a perdeuterated alkyl chain for studies of electric potential-dependent rearrangements, and changes in the microenvironment in a monolayer on a Au(111) surface. Electrochemical measurements show two states of the organization of ions on the electrode surface. In situ IR spectroscopy shows that the alkyl chains in imidazolium cations change their orientation depending on the adsorption state. The methylene-d 2 stretching modes in the perdeuterated IL display a reversible, potential-dependent appearance of a new band. The presence of this mode also depends on the anion in the IL. Supported by quantum chemical calculations, this new mode is assigned to a second ν as (CD 2 ) band in alkyl-chain fragments embedded in a polar environment of the anions/solvent present in the vicinity of the imidazolium cation and electrode. It is a measure of the potential-dependent segregation between polar and nonpolar environments in the layers of an IL closest to the electrode.

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“…A similar phenomenon has been found in previous research. 47 The MD snapshots of the CO 2 structure in the near-wall region at r = 20 Å are presented on the right of Figure 14. When the external potential is less than the critical value, the CO 2 is arranged approximately vertically at the electrode interface; otherwise, the CO 2 molecules are preferentially parallel to the electrode surface.…”

Section: Polarization Evolution In Edlmentioning

confidence: 99%

Molecular Understanding of Bilayer Structural Transition of CO₂ at the Ionic Liquid-Carbon Nanotube Electrode Interface

Chen,

Han,

et al. 2024

J. Phys. Chem. C

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In this paper, the atomistic-level descriptions of the electric double layer (EDL) formation of a CO2/ionic liquid (IL) on the carbon nanotube electrode are revealed by molecular dynamics simulations. The interfacial microenvironment and the orientation distribution depending on the pore radius and external potential are investigated. Throughout the evolution process, three different stages can be recognized by the variations of the coordination number and density distribution of cations. For small pore sizes, the interfacial structure is initially dominated by the nonelectrical force caused by the confinement effect; therefore, a similar density distribution of cation–anion ion pairs is observed in the vicinity of the electrode. With the increase of external potential, the cation [Bmim+] aggregates near the electrode, and the ion pairs are gradually separated by the CO2 molecule. Meanwhile, the coordination microenvironment of [Bmim+] is gradually occupied by the combination of [Bmim+] and CO2, and a steady EDL structure is formed. Once the external potential exceeds the critical value, the spontaneous charge separation phenomena can be determined by the interfacial density. With the decrease of pore radius, the critical potential for the transition becomes earlier. The EDL formation under potential polarization is associated with the simultaneous rearrangement of the orientation and mobility of [Bmim+] and CO2. The mobility and the orientation distribution determined from the MD simulations coincide well with the transition process. Once the transition is initiated, the orientation of CO2 changes from disordered to parallel to the electrode, while the imidazole ring of [Bmim+] is gradually oriented preferentially perpendicular to the electrode surface. On the other hand, the self-diffusion coefficient begins to decrease when structural transition is initiated. Once the transition process is completed, the value increases again, which reaffirms the microstructural evolution of EDL.

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Understanding Electric Field‐Dependent Structure Variation of Functional Ionic Liquids at the Electrode Interface

Cited by 8 publications

References 55 publications

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

CD Stretching Modes are Sensitive to the Microenvironment in Ionic Liquids

Molecular Understanding of Bilayer Structural Transition of CO₂ at the Ionic Liquid-Carbon Nanotube Electrode Interface

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Understanding Electric Field‐Dependent Structure Variation of Functional Ionic Liquids at the Electrode Interface

Cited by 8 publications

References 55 publications

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

Abnormal Enhanced Free Ions of Ionic Liquids Confined in Carbon Nanochannels

CD Stretching Modes are Sensitive to the Microenvironment in Ionic Liquids

Molecular Understanding of Bilayer Structural Transition of CO2 at the Ionic Liquid-Carbon Nanotube Electrode Interface

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Molecular Understanding of Bilayer Structural Transition of CO₂ at the Ionic Liquid-Carbon Nanotube Electrode Interface