The Effect of Surface Entropy on the Heat of Non-Wetting Liquid Intrusion into Nanopores

Abstract

On-demand access to renewable and environmentally friendly energy sources is critical to address current and future energy needs. To achieve this, the development of new mechanisms of efficient thermal energy storage (TES) is important to improve the overall energy storage capacity. Demonstrated here is the ideal concept that the thermal effect of developing a solid–liquid interface between a non-wetting liquid and hydrophobic nanoporous material can store heat to supplement current TES technologies. The fundamental macroscopic property of a liquid’s surface entropy and its relationship to its solid surface are one of the keys to predict the magnitude of the thermal effect by the development of the liquid–solid interface in a nanoscale environment—driven through applied pressure. Demonstrated here is this correlation of these properties with the direct measurement of the thermal effect of non-wetting liquids intruding into hydrophobic nanoporous materials. It is shown that the model can resonably predict the heat of intrusion into rigid mesoporous silica and some microporous zeolite when the temperature dependence of the contact angle is applied. Conversely, intrusion into flexible microporous metal–organic frameworks requires further improvement. The reported results with further development have the potential to lead to the development of a new supplementary method and mechanim for TES.

Compact Thermal Actuation by Water and Flexible Hydrophobic Nanopore

“…Moreover, thermodynamic estimations suggest that using high-surfaceentropy liquids together with nanoporous materials with high surface areas (of 1000 m 2 /g and more) results in large quantities of heat absorbed/generated during intrusion/ extrusion comparable with current thermal energy storage methods. 45 Such an advancement would considerably improve the efficiency of the proposed thermal actuator according to eqs 7 and 8.…”

“…It should be noted that, even though the majority of the studied systems feature endothermic intrusion and exothermic extrusion, it is not the general case. When a pore is large enough for a macroscopic description to be appropriate, thermodynamics suggest that intrusion/extrusion can be endothermic or exothermic depending on the contact angle and surface entropy. , It was also demonstrated experimentally that increasing viscosity can turn the intrusion process from endothermic to exothermic . For microporous materials endothermic intrusion and exothermic extrusion was reported for MFI zeolites, − while opposite signs of thermal effects were recorded for chabazite zeolite .…”

Tuning Wetting–Dewetting Thermomechanical Energy for Hydrophobic Nanopores via Preferential Intrusion

“…The smallest pore orifice size of ZIF-8 is 0.34 nm with a surface area of 1800 m 2 g –1 . This material had been used in previous investigations. , For the 11.5 wt % KBr solution, 100 g of KBr solid was purchased from Chempure and placed in a vacuum oven overnight at 200 °C and 11 mbar. Once the solid was cooled, 11.5 g was weighed into a bottle with 88.5 g of distilled and degassed water.…”

Quality-dependent performance of hydrophobic ZIF-67 upon high-pressure water intrusion–extrusion process

“…Additionally, heat from the environment is harvested if the process is endothermic. 26,31,32 At least part of these energies can be converted into electricity via triboelectric effects. 33…”