Understanding the dynamics of confined electrolytes through graphene-based channels is essential in multiple fields of science including: (a) developing novel artificial membranes for drug delivery, DNA sequencing and water desalination and (b) developing quantum nanoelectronic devices. In this work, All-Atom molecular dynamics simulations are used to study the adsorption of confined NaCl electrolyte solutions in graphene (GR), hexagonal boron nitride (hBN) and combined GR-hBN-GR nano-channels over a wide range of electrolyte concentrations c∈(0.1,2) M. The behavior of electrolytes confined between these surfaces is analyzed by evaluating the ionic density profiles, Potential of Mean Force (PMF), net charge density and integrated charge. Although neither graphene nor hBN has net electric charge, we observed significant changes in the ionic structure including the enhanced accumulation of sodium and the depletion in chloride density close to the hBN interfaces at low salt concentration. However, increasing the salt concentration leads to accumulation of chloride close to hBN surfaces. Two different types of hBN-GR junctions are considered in this study: a) shuffle (zigzag bonds) and (b) glide (parallel bonds). High adsorption of sodium and chloride ions near shuffle GR-hBN-GR surfaces is observed due to electrostatic attraction forces between the sodium and nitrogen atoms and between chloride and boron atoms at hBN–graphene junctions across zigzag bonds. This study reveals that GR-hBN-GR with shuffle interface is highly advantageous in adsorbing sodium and chloride ions than graphene and hBN alone. To the best of our knowledge, this is the first study that elucidates the interaction between monovalent electrolytes and GR-hBN-GR heterostructures in a confined medium.

Electrolyte adsorption in graphene and hexagonal boron nitride nanochannels

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