Insights Into Janus Interfaces with Ordered Micro/Nanostructures for Low‐Temperature Differential Evaporation

Abstract

Low‐temperature differential evaporation constitutes a promising direction for energy‐saving desalination. Herein, a novel Janus interfacial structure with well‐ordered micro/nanopores is developed. Fabricated Janus interfacial structure can weak the water intermolecular forces and pump water to the hydrophilic–hydrophobic junction. Within well‐ordered nanochannels, the increased curvature of the meniscus increases the ratio of thin water layers, thereby enhancing microscale heat transfer at the heated walls; in addition, the smaller nanopores limit the development of microscale vortices at the liquid–gas interface and prevent back mixing of intermediate water at the interface, which possess the nanoscale effect on intensifying the interfacial evaporation. These effects are validated by theoretical and experimental studies. Optimized Janus (20 nm)95°/25° structure exhibits evaporation fluxes up to 2.4 kg m−2 h−1 at 45 °C (feed side)/25 °C (permeate side, ambient pressure), as the theoretical evaporation enthalpy is only 30% of that for direct evaporation. The unique Janus structure simultaneously inhibits salt accumulation and achieve self‐cleaning, thereby maintaining steady performance during 480 h of continuous desalination and 50 cycles of batch operation. This work highlights a promising structural design strategy for separation materials with specific micro/nanoscopic topologies to achieve high performance thermally driven desalination applications.