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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mineral Scaling in 3D Interfacial Solar Evaporators–A Challenge for Brine Treatment and Lithium Recovery

In this work, we analyzed the effects of mineral scaling on the performance of a 3D interfacial solar evaporator, with a focus on the cations relevant to lithium recovery from brackish water. The field has been rapidly moving toward resource recovery applications from brines with higher cation concentrations. However, the potential complications caused by common minerals in these brines other than NaCl have been largely overlooked. Therefore, in this study, we thoroughly examined the effects of two common cations (calcium and magnesium) on the long-term solar evaporation performance of a 3D graphene oxide stalk. The 3D stalk can achieve an evaporation flux as high as 17.8 kg m –2 h –1 under one-sun illumination, and accumulation of NaCl on the stalk surface has no impact. However, the presence of CaCl 2 and MgCl 2 significantly reduces the evaporative flux even in solutions lacking scale-forming anions. A close examination of scale formation during long-term evaporation experiments revealed that CaCl 2 and MgCl 2 tend to precipitate out within the stalk, thus blocking water transport through the stalk and significantly dropping the evaporation rates. These findings imply that research attention is needed to modify and optimize the internal water transport channels for 3D evaporators. Additionally, we emphasize the importance of testing realistic mixtures–including prominent divalent cations– and testing long-term operations in interfacial solar evaporation research and investigating approaches to mitigate the negative impacts of divalent cations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Molecular Properties and Chemical Transformations Near Interfaces

The properties of bulk water and aqueous solutions are known to change in the vicinity of an interface and/or in a confined environment, including the thermodynamics of ion selectivity at interfaces, transition states and pathways of chemical reactions, and nucleation events and phase growth. Here we describe joint progress in identifying unifying concepts about how air, liquid, and solid interfaces can alter molecular properties and chemical reactivity compared to bulk water and multicomponent solutions. Furthermore, we also discuss progress made in interfacial chemistry through advancements in new theory, molecular simulation, and experiments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Surfactant-Induced Interfacial Aggregation of Porphyrins for Structuring Color-Tunable Liquids

Locking nonequilibrium shapes of liquids into targeted architectures by interfacial jamming of nanoparticles is an emerging area in material science. 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (H 6 TPPS) shows three different aggregation states that present an absorption imaging platform to monitor the assembly and jamming of supramolecular polymer surfactants (SPSs) at the liquid/liquid interface. The interfacial interconversion of H 6 TPPS, specifically H 4 TPPS 2- dissolved in water, from J- to an H-aggregation was induced by strong electrostatic interactions with amine-terminated polystyrene dissolved in toluene at the water/toluene interface. We find that this resulted in color-tunable liquids due to interfacial jamming of the SPSs formed between H 4 TPPS 2- and amine-terminated polystyrene. However, the formed SPSs cannot lock in nonequilibrium shapes of liquids. In addition, a self-wrinkling behavior was observed when amphiphilic triblock copolymers of PS-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) were used to interact with H 4 TPPS 2- . Subsequently, the SPSs formed can lock in nonequilibrium shapes of liquids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Interfacial Properties of Gold and Cobalt Oxyhydroxide in Plasmon-Mediated Oxygen Evolution Reaction

Water electrolysis is one green approach of storing electrical energy within chemical bonds of the high-energy hydrogen gas (H2). The anodic reaction involved in the oxygen evolution reaction (OER) requires high kinetic overpotential on the overall rate of the process. Recently, plasmonic gold nanoparticles (Au NPs) have been added to enhance the charge transfer at the interface of the OER electrocatalysts and electrolyte under light illumination. However, mechanistic understanding of how Au NPs on the photo-assisted electrochemical process is still lacking. We applied a model system of plasmonic Au electrode and a cobalt (Co)-based OER electrocatalyst in alkaline electrolytes to investigate the plasmon-mediated OER process with (photo)electrochemical and spectroscopic studies. Our results demonstrated that the electrodeposited and surfactant-free plasmonic Au electrode could enhance the electrocatalytic performances of the Co-based electrocatalysts in the OER process with continuous visible and near infrared light illumination. Both the photothermal and energetic charge carriers were found to contribute to the enhanced OER performance based on the transient photocurrent studies, and the interfaces of Au and the Co-based electrocatalysts determined the enhancement mechanisms. The active phase of the cobalt based OER electrocatalyst at operating potentials was identified with electrochemical Raman measurements.

OER↗
DOE OSTI2022

Hydrodynamics of countercurrent flow in an additive-manufactured column with triply periodic minimal surfaces for carbon dioxide capture

Computational investigation of the countercurrent flows in an additively manufactured (AM) column packed with triply periodic minimal surface (TPMS) is challenging. Multiphase flow simulations using the volume of fluid (VOF) method can explain the column’s hydrodynamic characteristics, including interfacial area, liquid holdup, pressure drop, flow regime, etc. The interfacial area is a key factor dictating the mass transfer via the absorption process, and thereby the overall efficiency of the column. The impacts of a solvent's physical properties, liquid and gas loads, and contact angle on the hydrodynamics are extensively explored. The solvents include traditional solvent (monoethanolamine [MEA]) used in industry as well as a water-lean solvent (EEMPA) as prospective solvents for carbon capture. As expected, interfacial area and liquid holdup increase with increasing liquid loads (q L ). The EEMPA exhibits higher values for the interfacial area and liquid holdup compared to those for the MEA. The dry and wet pressure drops per unit length in the column at different gas loads (F G ) are calculated and further compared with the empirical correlations for traditional packings. At low gas loads, i.e., in the preloading regime, the predicted values of the wet and dry pressure drops match well with the corresponding values calculated from available correlations. The gas load has a marginal impact on the interfacial area at its lower value, but the higher value of F G (>2.18 $\sqrt{Pa}$) causes flooding in the column. The effect of varying contact angles on the interfacial area and liquid holdup in the preloading regime is also studied. Both interfacial area and liquid holdup decrease with the increase in the value of the contact angle. Altogether, the effect of the contact angle on interfacial area is more pronounced than other parameters influencing the interfacial area.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A Cast Net Thrown onto an Interface: Wrapping 3D Objects with an Interfacially Jammed Amphiphilic Sheet

Wrapping a 3D object with a 2D sheet is not uncommon, but the wrapping behavior becomes complex and interesting when the sheet is bestowed with strong interfacial activities. Amphiphilic lignin macromolecules, isolated from biomass, form a scalable thin surfactant sheet at an oil/water interface through the interfacial jamming process. The process marks three distinct stages of interfacial behavior: a) diffusive assembly, b) viscous assembly with retarded mobility, and c) flexible yet irreversibly jammed rigid sheets. The surfactant sheet wraps, traps, and promptly stabilizes both oil and water droplets in nonequilibrium morphologies upon environmental stimulus. Finally, beyond preserving exotic morphologies, the highly interfacially active surfactant sheet also participates in morphology evolution by creating a vanishing interfacial tension and driving interfacial instability around the wrapped content, leading to novel morphologies as well as many potential applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Aerosol Optical Tweezers Elucidate the Chemistry, Acidity, Phase Separations, and Morphology of Atmospheric Microdroplets

Aerosol particles represent unique chemical environments because of their high surface area-to-volume ratio that promotes the effects of interfacial chemistry in confined environments. Properties such as viscosity, diffusivity, water content, pH, and morphology—following liquid–liquid phase separation—can strongly alter how a particle interacts with condensable vapors and reactive trace gases, thus modifying its continual evolution and environmental effects. Our understanding of this chemical evolution of atmospheric particulate matter and its environmental impacts is largely limited by our ability to directly observe how these critical particle properties respond to the addition or reactive uptake of new chemical components. Aerosol optical tweezers (AOT) stably trap particles in focused laser beams, providing positional control and the retrieval of many of these critical properties required to understand and predict the chemistry of aerosolized microdroplets. The analytical power of the AOT stems from the retrieval of the cavity-enhanced Raman spectrum induced by the trapping laser. Analysis of the whispering gallery modes (WGMs) that resonate as a standing wave around the droplet’s interface, provide high accuracy measurements of the droplet’s size, refractive index (and thus a measurement of composition), and can distinguish between core–shell, partially engulfed, and homogeneous morphologies. In this study, we have advanced the ability to determine the properties of the core and shell phases in biphasic droplets, including obtaining high-accuracy pH measurements. These capabilities were applied to perform AOT physical chemistry experiments on authentic secondary organic aerosol (SOA) produced directly in the AOT chamber by ozonolysis of terpene vapors. The propensity of the SOA to phase separate as a shell from a wide range of nonpolar to polar core phases was observed, along with the discovery of a stable emulsified state of SOA particles in an aqueous salt droplet. Micron-thick SOA shells did not impede the gain or loss of water or squalane from the core to the surrounding air, indicating no significant diffusional limitations to condensational growth or partitioning even under dry conditions. These experiments formed the foundation of a new framework that predicts how the phase-separated morphology of complex aerosols containing organic carbon evolves during continual atmospheric oxidation processes. Increases in oxidation state will quickly drive conversion from a partially engulfed to core–shell morphology that has dramatically different chemical reactivity since the core phase is completely concealed by the shell. The recent advances in the experimental capabilities of the AOT technique such as presented here enable novel experimental methodologies that provide insights into the chemistry and multidimensional properties of aerosol microdroplets, and how these coevolve and respond to continual chemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Resolving Nanoscale Processes during Carbon Mineralization Using Identical Location Transmission Electron Microscopy

Basalt reservoirs offer the potential for carbon mineralization, aiding in achieving net-zero emissions. However, debates persist about microscopic crystallization mechanisms due to limited characterization techniques under high-temperature and pressure conditions. By using Identical Location Transmission Electron Microscopy (IL-TEM) and cryo-TEM, this study reveals nanoscale interfacial carbonation processes of forsterite and diopside nanoparticles in water-saturated supercritical carbon dioxide under realistic reservoir conditions. Further, both minerals undergo preferential metal cation dissolution into a thin water film, forming porous Si-rich amorphous layers, supporting the leached layer mechanism as the dominant mineral reactivity process. Diopside’s amorphous layer has lower porosity and growth rate relative to forsterite, likely related to the connectivity of silicate tetrahedra. Kinetically favorable nesquehonite and aragonite nanocrystals form on the amorphous layers. These findings support the development of accurate reservoir simulations and help enable commercial-scale carbon storage deployment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

CFA-17-12798: Nanostructured Ceramic Membranes for Enhanced Tritium Management

This project focuses on the novel use of interfacial hydrated layers in ionic conducting ceramic materials for tritiated water (HTO) adsorption and recovery. Low-temperature water adsorption properties of nanoscale structured ceramics combined with hydrogen isotope exchange in their hydrated layers could provide a low-cost and transformative avenue to address tritium management challenges.

08 HYDROGEN↗
NASA NTRS2005

Hydrophobic effect at aqueous interfaces

Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.

Pohorille, Andrew↗
DOE OSTI2020

Surface Chemistry of Liquid Bismuth under Oxygen and Water Vapor Studied by Ambient Pressure X-ray Photoelectron Spectroscopy

Bismuth (Bi) has a fairly low melting point of 544 K making it practical as a liquid metal medium in a number of applications. Under ambient atmospheric conditions the surface of solid Bi oxidizes. While the solid Bi interface has been fairly well characterized with surface science studies upon exposure to oxygen, to date little is known about the molecular level reactivity of the liquid interface. Here, using ambient pressure X-ray photoelectron spectroscopy the liquid-gas interfacial chemistry of Bi was examined upon exposure to oxygen gas and water vapor at 550 K up to a maximum pressure of 0.5 Torr. Water vapor remained unreactive towards the liquid interface over the entire pressure range. Oxygen remined unreactive up to 10 –4 Torr, whereas above this pressure oxidation was observed forming Bi 2 O 3 . The oxidation exposure onset was > 5 x 10 5 Langmuirs, significantly higher than what is required for solid Bi interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Bipolar membrane polarization behavior with systematically varied interfacial areas in the junction region

The palette of applications for bipolar membranes (BPMs) has expanded recently beyond electrodialysis as they are now being considered for fuel cell and electrolysis applications. Their deployment in emerging electrochemical technologies arises from the need to have a membrane separator that provides disparate pH environments and to prevent species crossover. Most materials research for BPMs has focused on water dissociation catalysts and less emphasis has been given to the design of the polycation–polyanion interface for improving BPM performance. Here, soft lithography fabricated a series of micropatterned BPMs with precise control over the interfacial area in the bipolar junction. Polarization experiments showed that a 2.28× increase in interfacial area led to a 250 mV reduction in the onset potential. Additionally, the same increase in interfacial area yielded marginal improvements in current density due to the junction region being under kinetics-diffusion control. A simple physics model based on the electric field of the junction region rationalized the reduction in the overpotential for water dissociation as a function of interfacial area. Finally, the soft lithography approach was also conducive for fabricating BPMs with different chemistries ranging from perfluorinated polymer backbones to alkaline stable poly(arylene) hydrocarbon polymers. These polymer chemistries are better suited for fuel cell and electrolysis applications. The BPM featuring the alkaline stable poly(terphenyl) anion exchange membrane had an onset potential of 0.84 V, which was near the thermodynamic limit, and was about 150 mV lower than a commercially available variant.

25 ENERGY STORAGE↗
DOE OSTI2022

Study on Emulsification/Demulsification Behavior and Mechanism of Produced Liquid from Polymer Flooding on Alaska North Slope

Heavy oil reservoirs on Alaska North Slope (ANS) are unconsolidated and contain abundant clay minerals, where the first-ever field pilot is currently implemented to validate the use of polymer floods for heavy oil enhanced oil recovery (EOR). The polymer molecules and/or fine clay particles carried with the produced liquid could potentially affect the oil/water separation, which is one of the major concerns for field operators. This dissertation aims to investigate the emulsification behavior of produced liquid, understand the emulsifying mechanism, and seek an adaptive and cost-effective method to treat the produced liquid from polymer flooding. Emulsions were prepared by mechanically mixing the actual heavy oil and the produced water from the pilot site, of which the stability was investigated by bottle test method or multiple light scattering method. Drop size distribution and interfacial properties were measured via microscope and pendant drop technique to probe the stability mechanism further. Results showed that oil-continuous or water-continuous emulsion could be generated depending on the water cut, clay types, clay concentration, and polymer concentration. In the crude oil/water system, the increasing water cut triggered the phase inversion of oil-continuous emulsion to water-continuous emulsion, resulting in faster separation and lower emulsion stability. Whereas, clay particles, no matter added to the oil or water phase, resulted in an unfavorable phase inversion from the loose water-continuous emulsion to the tight oil-continuous emulsion as clay concentration increased. For all four types of clay except Ca-montmorillonite, clay particles added to water led to an earlier phase inversion and higher emulsion stability than that added to the oil. The dual function of polymer on emulsion stability was observed. On the one hand, both sheared and unsheared polymer tended to convert the oil-continuous emulsion formed in either crude oil/water system or complex crude oil/water/clay particle system to the water-continuous emulsion, acting as a weak demulsifier to accelerate the oil/water separation. On the other hand, the addition of polymer to the water-continuous emulsion could result in enhanced emulsion stability, which is primarily attributed to the increased viscosity of the continuous phase and the decreased drop size of the dispersed oil phase. Particularly, the sheared polymer had a weaker ability to stabilize the o/w emulsion than the unsheared polymer due to the lower viscosity of the sheared polymer solution resulting from the breakdown of the polymer macromolecules. As for the chemical demulsification tests, the performance of demulsifiers showed a complex dependency upon the water cut, the shearing intensity, demulsifier type and dosage, and the polymer concentration. A compound emulsion breaker, E12+E18, exhibited the most satisfactory demulsification performance despite the varied test conditions. For severe water-continuous emulsions that might require a multi-fold dosage of demulsifier, a less expensive electrolyte, KCl, was proposed to be used in combination with demulsifier E12+E18 to improve the demulsification performance. In the proposed demulsifier formula, the effectiveness of the commercial demulsifier relied on its destructive effect on the interfacial film, while the efficacy of KCl was mainly dependent on its viscosity reduction effect on the continuous phase. This dissertation illustrates that intermediate layer elimination and water clarification are the major challenges for produced liquid treatment from polymer flooding. It also provides practical and theoretical guidance in advance for the demulsification strategy of the produced liquid from the ongoing first-ever polymer flooding pilot on ANS.

Chang, Hongli↗
DOE OSTI2022

Moisture Stability of Sulfide Solid-State Electrolytes

In this report we detail a comprehensive study on the moisture stability of sulfide solid-state electrolytes in dry room environments. Although sulfide SSEs have many favorable attributes, this class of materials suffers from poor stability with water. Sulfide SSEs react with water to form gaseous H 2 S and a variety of solid byproducts like Li 3 PO 4 and LiOH, which go on to increase the interfacial impedance of solid-state batteries. Lab-scale research typically utilizes gloveboxes with <1 ppm water, however, the large-scale manufacturing of Li-ion batteries occurs in –40°C dewpoint dry rooms with around 126 ppm water. Consequently, the moisture stability of sulfide SSEs must be addressed if the manufacture of solid-state batteries based on sulfide SSEs is to be scaled up. Here, we are the first to characterize the moisture stability of sulfide SSEs according to both H 2 S and the degradation of ionic conductivity at different moisture setpoints ranging from –76°C to –40°C dewpoint. A variety of different SSE compositions are studied; namely, (Li 2 S) 75 (P 2 S 5 ) 25 , (Li 2 S) 70 (P 2 S 5 ) 30 , (Li 2 O) 7 (Li 2 S) 68 (P 2 S 5 ) 25 , (Li 2 O) 7 (Li 2 S) 63 (P 2 S 5 ) 30 , and (Li 2 S) 75 (P 2 S 5 ) 25 + 20 mol% LiI. We find that moisture stability improves with 75 mol% Li2S modifier content and the introduction of a Li 2 O co-modifier. After a 30 min exposure in a –40°C dewpoint dry room environment we found that (Li 2 S) 75 (P 2 S 5 ) 25 + 20 mol% LiI powder generated 0.1 cc/g H 2 S and its ionic conductivity decreased by over 50%. However, when SSE powder was exposed as a slurry in a dodecane carrier the same SSE composition generated 0 cc/g H 2 S and its ionic conductivity only dropped by 14%. Our results show that sulfide SSEs have acceptable moisture stability when appropriately processed in a dry room environment.

25 ENERGY STORAGE↗
DOE OSTI2021

Influence of interfacial responses of Berea Sandstone in low-salinity waterflooding environments

Wetting conditions and fluid-fluid interfacial properties are essential to understanding oil recovery in the context of low-salinity and smart waterflooding. Many have deemed wettability alteration to be the dominant interaction, while some highlight the importance of fluid-fluid interactions. In some rock-fluid systems, benefits from the use of additives can arise to favor hydrocarbon production. Understanding the balance between the fluid-fluid and rock-fluid interactions when utilizing additives is crucial to evaluate benefits in improved efficiency. Ultimately, this understanding will shed light on recovery mechanisms. Regarding oil recovery, previous studies indicate that the injection of a naphthenic acid (NA) blend dissolved in an injection brine improves oil recovery in Berea Sandstone, particularly under low-salinity conditions. Interfacial rheology results for the brine-oil interface correlated well with the recovery response. This observation was speculated to serve as a potential improved recovery mechanism through oil-trapping suppression. However, the said studies did not evaluate potentially concurrent rock wettability alteration during recovery or the initial wetting condition. The purpose of this work is to determine the production behavior in systems with NAs, namely NA-10 (3-Cyclohexanepropinoic acid), NA-14 (Cyclopentane carboxylic acid), NA-18 (Cyclohexane carboxylic acid), and NA-mix (Naphthenic acid mixture), at different initial wetting conditions under spontaneous imbibition. In addition, we tested the NAs ability to alter wettability in Berea Sandstone and determine each “additive’s” capacity to improve recovery. Here, time-domain nuclear magnetic resonance (TD-NMR), contact angle, and Amott cell tests, i.e. spontaneous imbibition, were used to analyze the influence of the selected naphthenic acids on oil displacement under different initial wetting conditions. Our results indicate that individual naphthenic acids indeed have potential as additives in low-salinity waterflooding for oil-wet systems while negatively impacting recovery in water-wet systems. However, results suggest that the evolution of the interfacial properties and wettability conditions are equally important on the recovery behavior.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

The electrochemical production of rare earth metals (REMs) in ionic liquids (ILs) has received much attention as a promising, sustainable and replacement to the molten salt electrolysis. Water additives have been recently suggested as a strategy to overcome the limitations of the ionic liquid process, but without complete assessment of its overall viability for the REMs production. In this regard, a full investigation of water impact on dysprosium (Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid was carried out. Water introduction was revealed to involve an interplay of implications on the electrodeposition process, including coordination, speciation, reduction pathways, interfacial dynamics, nucleation and metal stability and purity. In highly dry conditions, the reduction occurs at very negative potentials (-3.3V) in a consecutive pathway, resulting in negligible metal electrodeposition (low rate and efficiency) at the electrode surface. Initial water introduction (<30% molar fraction) leads to partitioning of the Dy complex between water and IL coordinated speciation, giving rise to an additional wave at more positive potentials (-2.4V). Probing and quantification of the heterogeneous Dy speciation by spectroscopic analyses enabled the uncovering of the reduction mechanism and accurate evaluation of the mass transport properties. While lowering the reduction thermodynamics, water addition also improved the nucleation, deposition rate and faradaic efficiency. In spite of these benefits, stripping voltammetric analysis also indicated substantial chemical reactivity of the deposited Dy metal with water additives and/or electrolyte components, under extended timescales. Surface characterization of the obtained product confirmed limited Dy metal stability (mostly oxidized/fluorinated) and purity (~60%) in the studied system. Moreover, high water introduction (>30% molar fraction) was shown to trigger a fast hydrogen evolution reaction (HER), downgrading the robustness of system efficiency. We report the overall impact of water additives seems to engender both promoting and mitigating effects on the Dy electrodeposition process, making the case for more innovative strategies to be sought.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Altered morphology and diffusivity of water confined in MXenes: Machine learning–accelerated computations combined with experiments

Nanoconfined water exhibits unique properties compared to bulk water due to limited quantities, frustrated hydrogen bonding, and surface interactions, which are fundamental for energy storage and transport applications. We integrate machine learning–accelerated ab initio molecular dynamics with x-ray diffraction (XRD) and inelastic neutron scattering (INS) to systematically analyze the thermodynamic and dynamic behavior of water confined between functionalized (-F, -O, and -OH) two-dimensional (2D) Ti 3 C 2 T x MXene layers. As water intercalates between layers, the interlayer spacing exhibits layer-dependent staging characteristics. The water polarization can be flipped by the count and morphology of intercalated molecules interacting with MXene surface groups, resulting in varying electrostatic potential profiles. On the basis of interfacial electrostatic potential, hydrogen bond lifetime, and molecular orientation, we establish a linear combination of exponential model describing water diffusivity. These computational insights align well with experimental x-ray and neutron measurements, suggesting strategies for tuning water morphology and transport by tailoring MXene surface chemistry and water content for electrochemical energy storage and nanofluidic applications.

Tang, Jiawei [Southeast Univ., Nanjing (China)] (O↗