top of page
Micro & Nano Physics Journal Logo.png

mnpl/3659/5548/2023/Quantum capacitance governs electrolyte conductivity in carbon nanotubes

Received 17, March 2023
Revised 26, May 2023
Accepted 29, July 2023

Heading 4


Mon Jul 31 2023 06:30:00 GMT+0000 (Coordinated Universal Time)

Make this article Open Accessed

Publisher Rating 10
Readers Rating 10
Citation (5)

Quantum capacitance governs electrolyte conductivity in carbon nanotubes

Th´eo Hennequin and Manoel Manghi∗ Laboratoire de Physique Th´eorique, Universit´e Paul Sabatier–Toulouse III, CNRS, France Adrien Noury, Fran¸cois Henn, Vincent Jourdain, and John Palmeri† Laboratoire Charles Coulomb, Universit´e de Montpellier, CNRS, France
Acknolowdgement NA

Keyword Highlighted

Quantum capacitance, carbon nanotubes, nano

Unlock Only

Read-only this publication

This option will drive you towards only the selected publication. If you want to save money then choose the full access plan from the right side.

Unlock all

Get access to entire database

This option will unlock the entire database of us to you without any limitations for a specific time period.
This offer is limited to 100000 clients if you make delay further, the offer slots will be booked soon. Afterwards, the prices will be 50% hiked.

In recent experiments, unprecedentedly large values for the conductivity of electrolytes through carbon nanotubes (CNTs) have been measured, possibly owing to flow slip and a high pore surface charge density whose origin is still unknown. By accounting for the coupling between the quantum CNT and the classical electrolyte-filled pore capacitances, we study the case where a gate voltage is applied to the CNT. The computed surface charge and conductivity dependence on reservoir salt concentration and gate voltage are intimately connected to the CNT electronic density of states. This approach provides key insight into why metallic CNTs have larger conductivities than semiconducting ones.

Although much experimental, theoretical, and molecular modeling effort has been devoted over the past years to understanding water and ion (electrolyte) transport through carbon nanotubes (CNTs) [1–3], the origin of the electric charge localized on the surface of industrially important CNT based nanofluidic systems still remains unclear (see Ref. [4] and references therein). It has already been proposed that this surface charge could arise from functional groups at the CNT entrances [5, 6] and/or the specific adsorption of ions, such as OH− [7]. Although the above cited studies lead to the conclusion that this surface charge plays a key role in governing ion transport in CNTs, it is difficult to regulate it directly and one is left to making inferences, for example by studying the variation of ionic conductance G with the pH or salt concentration, cs, of the external bulk reservoirs bounding the CNT. Intriguing results have been obtained, including a power law behavior, G ∝ c α s , with 1/2 ≤ α ≤ 1, which could be interpreted as the manifestation of an underlying surface charge regulation mechanism [8–10]. Through a simplified feasibility study we propose in this work that by biasing a CNT incorporated in a nanofluidic system via an applied gate voltage, Vg, and taking into account explicitly the quantum capacitance (QC) of the quasi-1D CNT structure as well as the nonlinear capacitance of the confined electrolyte ion the pore, it should be possible to quantify the CNT surface charge density σQ and establish a link between the intrinsic CNT electronic properties and ion transport through the same structure, such as the electrolyte conductance through the CNT. A major conclusion it that these intrinsic electronic properties will depend significantly, under certain conditions, on whether the CNT is metallic (M) or semiconducting (SC).