Quantum capacitance governs electrolyte conductivity in carbon nanotubes

TL;DR

This paper investigates how quantum effects in carbon nanotubes influence electrolyte conductivity, revealing that electronic density states and gate voltage significantly affect surface charge and conductivity, especially distinguishing metallic from semi-conducting CNTs.

Contribution

It introduces a coupled quantum-classical model linking CNT electronic properties with electrolyte conductivity, explaining experimental observations and differences between metallic and semi-conducting CNTs.

Findings

Conductivity depends on reservoir salt concentration and gate voltage.

Metallic CNTs exhibit higher conductivity than semi-conducting ones.

Quantum capacitance effects are key to understanding electrolyte transport in CNTs.

Abstract

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 semi-conducting ones.