A New Supercritical Phase and Fast Transport of Water in Two-Dimensions.

Wang, Zhihao; Liu, Yang; Li, Yong-Qiang; Qu, Yuanyuan; Zhou, Ruhong; Zhao, Mingwen; Li, Weifeng · Nano Lett · 2025

basic_science · Level V

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Abstract

Water structure and dynamics in confinement systems differ significantly from those in the bulk phase. Here, we report a new supercritical (SC) phase of water found in a 0.65 nm Au nanoslit. In this SC water, two metastable phases coexist, one shows solid-like (SL) behavior and the other is liquid-like (LL). Through calculating the isotherms in the "pressure-volume" plane, the critical point is determined to be at (<i>T</i><sub>c</sub>/K, <i>P</i><sub>c</sub>/MPa) = (262 ± 2, 14 ± 2). Under biased pressure, the LL domain can form a quick flow in the hydrophilic Au nanoslit, challenging the conventional wisdom that fast water transport can only occur in a hydrophobic environment. Instead, our results suggest that undercoordination is the key factor for efficient water transport. These findings contribute to a better understanding of the complicated water phase diagram and could find industrial potential for water treatment.