Understanding Capacitance Variation in Sub-nanometer Pores by <i>in Situ</i> Tuning of Interlayer Constrictions

Galhena, D Thanuja L; Bayer, Bernhard C.; Hofmann, Stephan; Amaratunga, G.A.J.

doi:10.1021/acsnano.5b05819

Cited by 71 publications

(49 citation statements)

References 53 publications

(145 reference statements)

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“…It has been shown that the maximum volumetric capacitance was achieved when the carbon pore size matched that of the adsorbing electrolyte ions. [25][26][27][28][29] The development of in situ experimental techniques, including the electrochemical quartz crystal microbalance [30][31][32] (EQCM) and small-angle X-ray scattering [33][34][35] (SAXS), has radically modified understanding of charge storage mechanisms and ion dynamics in nanoporous carbon-based supercapacitors in aqueous electrolytes. Recently, Prehal et al [33] used SAXS to characterize ion adsorption mechanisms in confined pores and the effects of different microporous carbons on the capacitance.…”

Section: Doi: 101002/smll201801897mentioning

confidence: 99%

“…Following this study, the origin of the anomalous increase in capacitance has received considerable attention. It has been shown that the maximum volumetric capacitance was achieved when the carbon pore size matched that of the adsorbing electrolyte ions . The development of in situ experimental techniques, including the electrochemical quartz crystal microbalance (EQCM) and small‐angle X‐ray scattering (SAXS), has radically modified understanding of charge storage mechanisms and ion dynamics in nanoporous carbon‐based supercapacitors in aqueous electrolytes.…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

Zhou

Hou

Luan

et al. 2018

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A full understanding of ion transport in porous carbon electrodes is essential for achieving effective energy storage in their applications as electrochemical supercapacitors. It is generally accepted that pores in the size range below 0.5 nm are inaccessible to electrolyte ions and lower the capacitance of carbon materials. Here, nitrogen-doped carbon with ultra-micropores smaller than 0.4 nm with a narrow size distribution, which represents the first example of electrode materials made entirely from ultra-microporous carbon, is prepared. An in situ electrochemical quartz crystal microbalance technique to study the effects of the ultra-micropores on charge storage in supercapacitors is used. It is found that ultra-micropores smaller than 0.4 nm are accessible to small electrolyte ions, and the area capacitance of obtained sample reaches the ultrahigh value of 330 µF cm , significantly higher than that of previously reported carbon-based materials. The findings provide a better understanding of the correlation between ultra-micropore structure and capacitance and open new avenues for design and development of carbon materials for the next generation of high energy density supercapacitors.

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Section: Doi: 101002/smll201801897mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

Zhou

Hou

Luan

et al. 2018

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“…water and acetonitrile). [21][22][23] Moreover, the sizes of slit pores provided by the interlayers of GO are "flexible" as they depend on the nature of the solvent along with the sizes of intercalated ions/molecules. 2,[24][25][26][27][28] Graphite/graphene oxides are commonly produced via the strong oxidation of graphite (e.g., using the Brodie or Hummers methods 29,30 ) and inherit the layered structure of pristine graphite.…”

Section: Introductionmentioning

confidence: 99%

Exactly matched pore size for the intercalation of electrolyte ions determined using the tunable swelling of graphite oxide in supercapacitor electrodes

et al. 2018

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The intercalation of solvent molecules and ions into sub-nanometer-sized pores is one of the most disputed subjects in the electrochemical energy storage applications of porous materials. Here, we demonstrate that the temperature-and concentration-dependent swelling of graphite oxide (GO) can be used to determine the smallest pore size required for the intercalation of electrolyte ions into hydrophilic pores. The structure of Brodie graphite oxide (BGO) in acetonitrile can be temperature-switched between the ambient one-layer solvate with an interlayer distance of ∼8.9 Å and the two-layer solvate (∼12.5 Å) at low temperature, thus providing slit pores of approximately 2.5 and 6 Å. Using in situ synchrotron radiation X-ray diffraction (XRD) and the temperature dependence of capacitance in supercapacitor devices, we found that solvated tetraethylammonium tetrafluoroborate (TEA-BF 4 ) ions do not penetrate into both the 2.5 and 6 Å slit pores formed by BGO interlayers. However, increasing the electrolyte concentration results in the formation of a new phase at low temperature. This phase shows a distinct interlayer distance of ∼15-16.6 Å, which corresponds to the insertion of partly desolvated TEA-BF 4 ions. Therefore, the remarkable ability of the GO structure to adopt variable interlayer distances allows for the determination of pore sizes that are optimal for solvated TEA-BF 4 ions (about 9-10 Å). The intercalation of TEA-BF 4 ions into the BGO structure is also detected as an anomaly in the temperature dependence of supercapacitor performance. The BGO structure remains to be expanded, even after the removal of acetonitrile, adopting an interlayer distance of ∼10 Å. † Electronic supplementary information (ESI) available. See

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“…Completely dried GO was used for further characterization and supercapacitor electrode fabrication. As produced, completely dried GO was characterized using different complementary methods 2 and used for activated carbon (AC)/r-GO electrode fabrication. The results clearly confirmed the successful fabrication of GO decorated with hydroxyl, carbonyl, ether, and carboxyl groups, which in its restacked dried form keeps an interlayer distance of ∼0.79 nm.…”

Section: Methodsmentioning

confidence: 99%

“…Because electrode materials are the key components to the performance of supercapacitors, rationally designing and fabricating high-quality electrode materials play a decisive role in developing next-generation high-performance supercapacitors. 2−4 …”

Section: Introductionmentioning

confidence: 99%

Reduced Graphene Oxide as a Monolithic Multifunctional Conductive Binder for Activated Carbon Supercapacitors

et al. 2018

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Using reduced graphene oxide (r-GO) as a multifunctional conductive binder, a simple, cost-effective, and environmentally friendly approach is developed to fabricate activated carbon/reduced graphene oxide (AC/r-GO) composite electrodes for supercapacitors with outstanding performance. In such a composite, r-GO provides several much needed critical functions: r-GO not only serves as the binder material improving the AC particle/particle cohesion and electrode-film/substrate adhesion but also improves the electrical conductivity of the composite and provides additional surfaces for ion adsorption. Furthermore, during electrode fabrication, initial GO precursor functions as an effective dispersant for AC, resulting in a stable electrode material slurry. Employing characterization by advanced microscopy techniques, we show that AC and r-GO assemble into an interconnected network structure, resulting in a composite with high specific capacitance, excellent rate capability, and long cycling life stability. Such high-performance electrodes coupled with their relatively simple, scalable, and low-cost fabrication process thereby provide a clear pathway toward large-scale implementation of supercapacitors.

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Understanding Capacitance Variation in Sub-nanometer Pores by in Situ Tuning of Interlayer Constrictions

Cited by 71 publications

References 53 publications

Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

Exactly matched pore size for the intercalation of electrolyte ions determined using the tunable swelling of graphite oxide in supercapacitor electrodes

Reduced Graphene Oxide as a Monolithic Multifunctional Conductive Binder for Activated Carbon Supercapacitors

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