Vertically Oriented Propylene Carbonate Molecules and Tetraethyl Ammonium Ions in Carbon Slit Pores

Fukano, Masafumi; Fujimori, Toshihiko; Ségalini, Julie; Iwama, Etsuro; Taberna, Pierre‐Louis; Iiyama, Taku; Ohba, Tomonori; Kanoh, Hirofumi; Gogotsi, Yury; Simon, Patrice; Kaneko, Katsumi

doi:10.1021/jp311896q

Cited by 26 publications

(29 citation statements)

References 24 publications

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“…Under the steady-state conditions employed here, and in contrast to dynamic measurements performed in other EQCM studies, solvent molecules will have time to reorder so that they can take up less space. We note that the ordering of propylene carbonate solvent molecules within micropores has recently been observed by X-ray total scattering experiments 30 . Pair distribution function analysis identified a shortening of the average intermolecular distance by approximately 0.05 Å as compared with bulk solution, interpreted as a densification of the packing of the propylene carbonate molecules through vertical alignment.…”

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confidence: 54%

In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors

et al. 2015

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Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results show that charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

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confidence: 54%

In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors

et al. 2015

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“…Indeed, recent X-ray diffraction experiments have indicated vertical ordering of solvent molecules in small micropores during charging. 69 …”

Section: Ex Situ Solid-state Nmr Methods For Studying Supercapacitor mentioning

confidence: 99%

Solid-state NMR studies of supercapacitors

Griffin

Forse

Grey

2016

Solid State Nuclear Magnetic Resonance

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Electrochemical double-layer capacitors, or 'supercapacitors' are attracting increasing attention as high-power energy storage devices for a wide range of technological applications. These devices store charge through electrostatic interactions between liquid electrolyte ions and the surfaces of porous carbon electrodes. However, many aspects of the fundamental mechanism of supercapacitance are still not well understood, and there is a lack of experimental techniques which are capable of studying working devices. Recently, solid-state NMR has emerged as a powerful tool for studying the local environments and behaviour of electrolyte ions in supercapacitor electrodes. In this Trends article, we review these recent developments and applications. We first discuss the basic principles underlying the mechanism of supercapacitance, as well as the key NMR observables that are relevant to the study of supercapacitor electrodes.We then review some practical aspects of the study of working devices using ex situ and in situ methodologies and explain the key advances that these techniques have allowed on the study of supercapacitor charging mechanisms. NMR experiments have revealed that the pores of the carbon electrodes contain a significant number of electrolyte ions in the absence of any charging potential. This has important implications for the molecular mechanisms of supercapacitance, as charge can be stored by different ion adsorption/desorption processes. Crucially, we show how in situ NMR experiments can be used to quantitatively study and characterise the charging mechanism, with the experiments providing the most detailed picture of charge storage to date, offering the opportunity to design enhanced devices. Finally, an outlook for future directions for solid-state NMR in supercapacitor research is offered.3

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“…222 Later, they used the same methodology to analyze organic electrolytes (TEABF 4 in propylene carbonate) confined in the micropores of CDC and activated carbon fiber (ACF). 223 Fig. 12a shows the synchrotron XRD patterns of porous carbons and porous carbons impregnated with the electrolyte.…”

Section: Other Ex Situ and In Situ Characterization Techniquesmentioning

confidence: 99%