Microscopic kinetics pathway of salt crystallization in graphene nanocapillaries

TL;DR

This study uncovers the atomistic mechanisms of NaCl crystallization within graphene nanocapillaries, revealing unique morphologies and phases influenced by confinement, with implications for materials design and crystallization theory.

Contribution

It provides the first detailed microscopic kinetic pathway of salt crystallization in graphene nanocapillaries, combining experimental and theoretical insights.

Findings

NaCl forms with a hexagonal morphology in confinement

A transitory graphite-like phase appears during crystallization

Confinement influences both kinetics and thermodynamics of crystallization

Abstract

The fundamental understanding of crystallization, in terms of microscopic kinetic and thermodynamic details, remains a key challenge in the physical sciences. Here, by using in situ graphene liquid cell transmission electron microscopy, we reveal the atomistic mechanism of NaCl crystallization from solutions confined within graphene cells. We find that rock salt NaCl forms with a peculiar hexagonal morphology. We also see the emergence of a transitory graphite-like phase, which may act as an intermediate in a two-step pathway. With the aid of density functional theory calculations, we propose that these observations result from a delicate balance between the substrate-solute interaction and thermodynamics under confinement. Our results highlight the impact of confinement on both the kinetics and thermodynamics of crystallization, offering new insights into heterogeneous crystallization theory and a potential avenue for materials design.