Solvent granularity in the differential electrical capacitance of supercapacitor and mechanism analysis

Zhou, Shiqi

doi:10.1016/j.physa.2019.121905

Cited by 28 publications

(24 citation statements)

References 60 publications

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“…(1) The solvent crowding effect helps to raise the C d –σ curve, and the effect weakens and eventually disappears as the surface charge strength |σ| increases. This may be a general conclusion as a similar tendency is also found previously , in the case of restricted SPM (RSPM) electrolyte, where cations and anions have equal size, and the interionic non-HS neutral interaction is considered . However, the difference between the SPM and RSPM exists.…”

Section: Resultssupporting

confidence: 85%

“…It is analyzed that the curve rising is due to the solvent-induced depletion attraction between the ions (counterion and/ or co-ion) that increases the adsorption capacities of the ions. The present results, combined with previous works, 53,54 indicate that the solvent-induced depletion mechanism works for asymmetrical ion size cases and various other situations as well, such as equal ion size, different bulk concentrations, ion valences, interionic non-HS neutral interactions, and pore radii, therefore should be a general mechanism explanation for the C denhancing effect by the solvent crowding. It is exemplified that the C d -enhancing effect of the solvent crowding works only for lower surface charge density strength, upper limit of which is negatively correlated with the counterion size; this is so because the presence of the solvent reduces the available space for packing the ions, whereas small size of the ion plays an opposite role.…”

Section: Discussionsupporting

confidence: 83%

“…Above analysis applies to the situation when the co-ion size increases, and causes similar outcomes, as exemplified by the curves (Figure 1C) characterized with σ > 0 and c = 4 M and d + * = 1.2,1.4, and 1.6, respectively. As for the origin of the C d -enhancing effect due to the solvent crowding, as analyzed in the literature, 53,54 we think that it is the solvent-induced depletion attraction between the ions (counterion and/or co-ion) that increases the adsorption capacities of the ions and raises the C d . The present results only indicate that the solvent-induced depletion attraction may be a general mechanism explanation for the C d -enhancing effect by the solvent crowding.…”

Section: Resultsmentioning

confidence: 98%

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How Ion Size influences Energy Storage in Cylindrical Nanoporous Supercapacitors

Zhou

2019

J. Phys. Chem. C

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The present study is performed on the way and mechanism by which ion size changes curves of differential electrical capacitance (C d ) vs surface charge strength |σ| and energy storage density E vs applied voltage U of an electrical double layer (EDL) formed inside a cylindrical pore electrode. Several valuable findings are made. (i) The C d −|σ| curve generally rises as a result of solvent granularity, which combined with simultaneous higher ion (whether counter-or co-ion) size and higher electrolyte bulk concentration, causing obvious overall morphology change of the curve. (ii) Smaller counterion always raises greatly both C d and E, whereas the co-ion size only has a very weak influence on C d over a range of |σ| around zero, and has almost no influence on E. (iii) One higher counterion electrical valence helps in raising both C d and E, but the electrolyte bulk concentration has no obvious influence on both C d and E in the presence of a higher valence counterion. (iv) The change rate of E with σ exhibits an inflection point at an appropriately large value of |σ| if the counterion valence is not too high (for example, bivalence), and simultaneously the counterion diameter increases. The above findings and relevant mechanisms can be explained reasonably by the changes of ions local distributions in the EDL and their adsorption capacities.

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Section: Resultssupporting

confidence: 85%

Section: Discussionsupporting

confidence: 83%

Section: Resultsmentioning

confidence: 98%

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How Ion Size influences Energy Storage in Cylindrical Nanoporous Supercapacitors

Zhou

2019

J. Phys. Chem. C

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“…One of the most significant changes caused by the low

value is that both the

value and the

value reduce greatly with the low

value dropping. Generally speaking, previous studies indicate repeatedly [ 73 , 74 ] that the

value falls within order of magnitude of

for the normal aqueous

value, such as

, whereas for the low

value, as considered presently, such as

, the

value falls within order of magnitude of

. i.e., the

value goes down two orders of magnitude for approximately equal electrode potential.…”

Section: Resultsmentioning

confidence: 62%

“…This is another novel point of the present work as a considerable part of the works for the SC [ 16 , 70 , 71 , 72 , 73 ] employing aqueous electrolyte solution uses the

value corresponding to that of the bulk water. This is necessary because as the device size becomes smaller and smaller, amount of solvent adsorption near the interface tends to decrease [ 74 ]; moreover, correlation of the electric dipole perpendicular to the surface also decreases. It is the two factors [ 75 ] that leads to a decrease of the aqueous dielectric constant inside the pore.…”

Section: Introductionmentioning

confidence: 99%

On Capacitance and Energy Storage of Supercapacitor with Dielectric Constant Discontinuity

Zhou

2022

Nanomaterials

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The classical density functional theory (CDFT) is applied to investigate influences of electrode dielectric constant on specific differential capacitance Cd and specific energy storage E of a cylindrical electrode pore electrical double layer. Throughout all calculations the electrode dielectric constant varies from 5, corresponding to a dielectric electrode, to εwr = 108 corresponding to a metal electrode. Main findings are summarized as below. (i): By using a far smaller value of the solution relative dielectric constant εr = 10, which matches with the reality of extremely narrow tube, one discloses that a rather high saturation voltage is needed to attain the saturation energy storage in the ultra-small pore. (ii): Use of a realistic low εr = 10 value brings two obvious effects. First, influence of bulk electrolyte concentration on the Cd is rather small except when the electrode potential is around the zero charge potential; influence on the E curve is almost unobservable. Second, there remain the Cd and E enhancing effects caused by counter-ion valency rise, but strength of the effects reduces greatly with dropping of the εr value; in contrast, the Cd and E reducing effects coming from the counter-ion size enhancing remain significant enough for the low εr value. (iii) A large value of electrode relative dielectric constant εrw always reduces both the capacitance and energy storage; moreover, the effect of the εrw value gets eventually unobservable for small enough pore when the εrw value is beyond the scope corresponding to dielectric electrode. It is analyzed that the above effects take their rise in the repulsion and attraction on the counter-ions and co-ions caused by the electrode bound charges and a strengthened inter-counterion electrostatic repulsion originated in the low εr value.

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Application of differential transformation and Hermite wavelet methods for micropolar flow through a permeable channel

Vinod

Raghunatha

Kumar³

2023

Heat Trans

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In this study, micropolar fluid flow in a porous channel is investigated using the differential transform method (DTM) and the Hermite wavelet method (HWM). By exploiting Berman's similarity transformation, the governing partial differential equations are transformed into a system of nonlinear coupled ordinary differential equations (ODEs). The concepts of DTM and HWM are briefly introduced and employed to derive solutions of nonlinear coupled ODEs. Our results compared with solutions already existing in the literature. When we compare DTM and HWM, HWM is more efficient and also requires less time to maintain a higher level of accuracy. The results are presented to study the velocity and microrotation profiles for various physical parameters such as Reynolds number, coupling parameter, spin‐gradient viscosity parameter, and micropolar fluid constant. As an important result, increases in the values of the coupling parameter and micropolar fluid constant have different results in comparison with the spin‐gradient viscosity parameter increasing.

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Solvent granularity in the differential electrical capacitance of supercapacitor and mechanism analysis

Cited by 28 publications

References 60 publications

How Ion Size influences Energy Storage in Cylindrical Nanoporous Supercapacitors

How Ion Size influences Energy Storage in Cylindrical Nanoporous Supercapacitors

On Capacitance and Energy Storage of Supercapacitor with Dielectric Constant Discontinuity

Application of differential transformation and Hermite wavelet methods for micropolar flow through a permeable channel

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