Mechanistic Investigation of Electrostatic Field‐Enhanced Water Evaporation

Abstract

Investigations on external electrostatic field (EEF)-enhanced liquid water evaporation have been reported decades ago, which suggest that molecular alignment and polarization tuned by EEF accelerating the phase change process could be responsible for EEF-enhanced water evaporation. However, a detailed study revealing the role of EEF in altering the intermolecular and intramolecular water structure is lacking. Herein, an EEF is proved to tune water state by accelerating the thermal movement of water molecules, lowering the molecular escaping energy, and loosening the hydrogen bond structure. The detailed mechanisms and field interactions (heat and electrostatic) are investigated by in situ Raman characterizations and molecular dynamic simulations, which reveal that an EEF can effectively reduce the free energy barrier of water evaporation and then increase the evaporated water molecule flux. As a proof of concept, an EEF is integrated into an interfacial two-dimentional solar steam generator, enhancing the efficiency by up to 15.6%. Similar to a catalyst lowing activation energy and enhancing kinetics of a chemical reaction, the EEF enhances water state tuning, lowers evaporation enthalpy, and then boosts steam generation rate with negligible additional energy consumption, which can serve as a generic method for water evaporation enhancement in water harvesting, purification, and beyond.

A Wave‐Driven Piezoelectric Solar Evaporator for Water Purification

“…[32] Uniform and alternating electric fields have been found to improve water evaporation in previous studies. [33][34][35][36] Unfortunately, the direct application of electricity to facilitate water evaporation cannot be regarded as an equivalent substitute for hydrogels because of its high cost and violation of the intention of green and sustainable development. Notably, oceans include various energy resources, such as tidal energy, wave energy, and ocean current energy.…”

MXenes—An Emerging Class of 2D Materials for Solar Water Desalination: Feasibility and Recent Advances

“…Furthermore, Li's group demonstrated the first example of increasing the water evaporation rate through external electrostatic field (EEF) for the MXene‐based evaporator (CAM membrane). [ 120 ] They found the presence of EEF can change the structure and state of water molecules (accelerated translation and collision of water molecules, weakened hydrogen bonding, and formation of small clusters by water molecules), reduce the water vaporization enthalpy, and thus endow the evaporator with better water production performance. Figure 6c shows the water mass loss over time for the CAM membrane evaporators under different light illumination and EEF conditions.…”

“…Reproduced under terms of the CC‐BY license. [ 120 ] Copyright 2021, The Authors. Published by Wiley‐VCH GmbH.…”

Interfacial Solar Steam/Vapor Generation for Heating and Cooling

“…Benefit from improving heat localization at the liquid surface through material design, >90% solar to vapor conversion efficiency under 1 Sun can be realized. [ 8–63 ] In the process of solar steam/vapor conversion, in addition to achieving water purification through evaporation and condensation, it is also accompanied by energy conversion. Specifically, evaporation is a process of taking away energy (e.g., the evaporation of 1 g of water needs to take away about 2260 kJ of energy at 100 °C), that is, cooling.…”