Non-isothermal flow of an electrolyte in a charged nanochannel

Abstract

Electrokinetic flows are generally analyzed, assuming isothermal conditions even though such situations are hard to be achieved in practice. In this paper, the flow of a symmetric electrolyte in a charged nanochannel subjected to an axial temperature gradient is investigated using molecular dynamics simulations. We analyze the relative contribution of the Soret effect, the thermoelectric effect, and the double layer potential in the electrical double layer for various surface charges and temperature gradients. We find the flow driven by thermal gradient is analogous to electroosmotic flow. The thermophoretic motion of the electrolyte is significant for negative surface charge than the positive surface charge. The vibrational spectrum of graphene is calculated to delineate the effect of the surface charge polarity on the observed thermophoretic motion of the electrolyte. A unique structure of interfacial water layer is observed for the positive and negative surface charges. We attribute the presence of these structures to the differences in water-carbon interactions existing for various surface charge polarity. For an applied thermal gradient in the range 2.6 K nm−1 to 8 K nm−1, we observe a continuous net flow with average velocities reaching up to 9.4 m s−1 inside the channel for a negative surface charge of −0.101 C m−2. The results indicate that in a charged graphene-based nanochannel, temperature gradients can be employed to induce streaming current, depending on the relative influence of the Soret effect and the double layer potential.

Fast and versatile thermo-osmotic flows with a pinch of salt

“…Historically, the first experimental results on thermo-osmosis were published by Lippmann 9 and Aubert 10 at the beginning of the 20th century. Since then, a broad literature has been devoted to the study of aqueous solutions and various membranes, both from experiments [11][12][13][14][15] or molecular dynamics (MD) simulations [16][17][18][19][20] . Some disagreements have been reported for aqueous electrolytes, specifically in the flow direction (toward the hot side, so-called thermophilic flow, or toward the cold side, so-called thermophobic flow) for similar systems [21][22][23][24] , or on the relation between the flow amplitude and surface charge 13 .…”

Temperature-dependent differential capacitance of an ionic liquid-graphene-based supercapacitor

“…Theoretical and computational studies in recent years have provided insights into the microscopic details of interfacial systems, particularly the structure of electric double layers, their dynamics, and the capacitive properties in electric double-layer capacitors (EDLCs) using RTILs as electrolytes. [15][16][17][18][19][20][21][22] Intensive efforts have been made to enhance the performance of EDLCs utilizing carbon-based materials. 23 Various carbonbased materials have been suggested and utilized as electrodes.…”

“…Theoretical and computational studies in recent years have provided insights into the microscopic details of interfacial systems, particularly the structure of electric double layers, their dynamics, and the capacitive properties in electric double-layer capacitors (EDLCs) using RTILs as electrolytes. 15–22…”

Molecular Probe Embedded Porous Polymer Scaffold as Solid‐State Visual Sensor for Selective and Sequential Sensing of Ultra‐Trace Toxic Heavy Metal Ions in Environmental/Commercial Samples

“…Polymer monoliths favor better interaction with molecular probes focusing on target specificity and selectivity, with efficient regeneration/reusability. [ 17 ] However, the meticulous sensing performance of the literature‐reported solid‐state sensors shows detection on a particular analyte. [ 18–22 ]…”