Understanding how surface chemistry modulates confined electrolyte behavior is critical for advancing electrochemical, membrane, and nanofluidic technologies. Here, we present a comprehensive molecular dynamics study of aqueous NaCl solutions confined between graphene functionalized with -COOH, -OH, ═O, and -CH3 groups across multiple surface coverages and electrolyte concentrations. We systematically disentangle how functional group identity and abundance independently shape interfacial layering, ion adsorption, and water dynamics. Polar, hydrogen-bonding groups (-COOH, -OH) strongly structure the interface and suppress water mobility, while weakly polar (═O) and nonpolar groups (-CH3) lead to more diffuse, mobile profiles. Importantly, we show that functional group chemistry sets the morphology of interfacial structure, while coverage scales its intensity, a distinction that holds across electrolyte concentrations. These findings enable a quantitative framework for designing chemically heterogeneous surfaces that precisely modulate ion and solvent behavior in complex electrolyte environments.
Hess et al. (Wed,) studied this question.