TY - JOUR
T1 - Water Adsorption on Mica Surfaces with Hydrophilicity Tuned by Counterion Types (Na, K, and Cs) and Structural Fluorination
AU - Koishi, Ayumi
AU - Lee, Sang Soo
AU - Fenter, Paul
AU - Fernandez-Martinez, Alejandro
AU - Bourg, Ian C.
N1 - Publisher Copyright:
© 2022 American Chemical Society. All rights reserved.
PY - 2022/9/29
Y1 - 2022/9/29
N2 - The stability of adsorbed water films on mineral surfaces has far-reaching implications in the Earth, environmental, and materials sciences. Here, we use the basal plane of phlogopite mica, an atomically smooth surface of a natural mineral, to investigate water film structure and stability as a function of two features that modulate surface hydrophilicity: the type of adsorbed counterions (Na, K, and Cs) and the substitution of structural OH groups by F atoms. We use molecular dynamics simulations combined with in situ high-resolution X-ray reflectivity to examine surface hydration over a range of water loadings, from the adsorption of isolated water molecules to the formation of clusters and films. We identify four regimes characterized by distinct adsorption energetics and different sensitivities to cation type and mineral fluorination: from 0 to 0.5 monolayer film thickness, the hydration of adsorbed ions; from 0.5 to 1 monolayer, the hydration of uncharged regions of the siloxane surface; from 1 to 1.5 monolayer, the attachment of isolated water molecules on the surface of the first monolayer; and for >1.5 monolayer, the formation of an incipient electrical double layer at the mineral-water interface.
AB - The stability of adsorbed water films on mineral surfaces has far-reaching implications in the Earth, environmental, and materials sciences. Here, we use the basal plane of phlogopite mica, an atomically smooth surface of a natural mineral, to investigate water film structure and stability as a function of two features that modulate surface hydrophilicity: the type of adsorbed counterions (Na, K, and Cs) and the substitution of structural OH groups by F atoms. We use molecular dynamics simulations combined with in situ high-resolution X-ray reflectivity to examine surface hydration over a range of water loadings, from the adsorption of isolated water molecules to the formation of clusters and films. We identify four regimes characterized by distinct adsorption energetics and different sensitivities to cation type and mineral fluorination: from 0 to 0.5 monolayer film thickness, the hydration of adsorbed ions; from 0.5 to 1 monolayer, the hydration of uncharged regions of the siloxane surface; from 1 to 1.5 monolayer, the attachment of isolated water molecules on the surface of the first monolayer; and for >1.5 monolayer, the formation of an incipient electrical double layer at the mineral-water interface.
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U2 - 10.1021/acs.jpcc.2c04751
DO - 10.1021/acs.jpcc.2c04751
M3 - Article
C2 - 37881644
AN - SCOPUS:85138848615
SN - 1932-7447
VL - 126
SP - 16447
EP - 16460
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 38
ER -