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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Energy Where it Matters: Delivering Heat to the Membrane/Water Interface for Enhanced Thermal Desalination

The overall goal of the project is the development of a solar-driven membrane distillation (MD) process that can treat high salinity brines (>100 g/L) at a cost below $1.5/m3. The process relies on thermally and electrically conducting MD membranes that deliver solar heat directly to the membrane surface and prevent membrane fouling through the application of electrical potentials to the membrane surface.

14 SOLAR ENERGY↗
DOE OSTI2025

Controlling Interfacial Energetics and Charge Transfer Rates in 2D Semiconductors: Fundamental Studies en Route to Photoelectrochemical Energy Conversion Beyond the Shockley-Queisser Limit (Final Scientific/Technical Report)

Current photovoltaic and solar-to-fuel technologies do not fully utilize the energy of sunlight because excess photon energy above the semiconductor band gap is rapidly lost as heat through hot-carrier thermalization. Overcoming this loss mechanism is critical, as hot-carrier-based energy conversion systems are predicted to exceed the conventional efficiency limit of ~33%. This project advanced fundamental understanding of hot-carrier energy conversion in two-dimensional (2D) semiconductors, with a focus on monolayer MoS 2 . Using a combination of electrochemical microscopy and in situ ultrafast spectroscopic measurements, this research directly demonstrated hot-carrier extraction from monolayer MoS 2 photoelectrodes in proof-of-concept liquid junction solar cells. These measurements established that hot-carrier transfer can compete with ultrafast carrier cooling at solid–liquid interfaces, providing unambiguous experimental evidence that hot-carrier extraction is feasible in atomically thin semiconductors under operating photoelectrochemical conditions. Beyond demonstration, the project identified design rules for tuning hot-carrier extraction rates relative to cooling rates in 2D semiconductor photoelectrodes. The outcomes of this research provide foundational thermodynamic and kinetic insights for the rational design of next-generation hot-carrier-enabled solar energy conversion systems. These findings have broad implications for photoelectrochemical solar fuels production, electrocatalysis, and emerging energy conversion architectures that seek to harness nonequilibrium charge carriers for enhanced efficiency.

14 SOLAR ENERGY↗
DOE OSTI2022

Assessing the Role of the Support in Acetic Acid Hydrodeoxygenation Selectivity on Pt/TiO2

To produce drop-in quality biofuels following the thermochemical conversion of biomass via catalytic fast pyrolysis (CFP), hydrodeoxygenation (HDO) reactions can be performed to remove excess oxygen and create a more stable bio-oil product. HDO reactions involve co-feeding the CFP vapor-phase product and H2 gas over bi-functional catalysts, such as noble-metal catalysts supported on reducible metal oxides (e.g., Pt/TiO2). Recent model-compound studies, focusing on important classes of species in the CFP vapor mixture, have sought to determine the role of the various Pt/TiO2 actives sites (i.e., Pt-metal, TiO2-support, Pt-TiO2-interfacial sites) in producing the observed desired deoxygenation and undesired decarboxylation/decarbonylation products. One important class of compounds in the CFP vapor-phase product is carboxylic acids (e.g., acetic acid). Prior experimental work on acetic acid HDO (AA-HDO) found that Pt/C and Pt/TiO2 catalysts favored the formation of undesired C-C and desired C-O bond-dissociation products; however, the fundamental surface chemistry driving this shift in selectivity has not been established. This presentation employs atomic-scale modeling to determine, through comparisons of adsorption and reaction energetics, how Pt-metal, Pt-TiO2-interface, and interfacial-vacancy sites catalyze the competing reaction pathways for AA-HDO. Our analysis indicates that hydroxyl vacancies at the Pt-TiO2 interface are critical for lowering barriers for C-O bond-cleavage steps, such that they become favorable/competitive with respect to C-C bond-dissociation steps.

BIOMASS FUELS,INORGANIC, ORGANIC, PHYSICAL, AND AN↗
DOE OSTI2022

Exceptional Mineral Scaling Resistance from the Surface Gas Layer: Impacts of Surface Wetting Properties and the Gas Layer Charging Mechanism

Mineral scaling is a phenomenon that occurs on submerged surfaces in contact with saline solutions. In membrane desalination, heat exchangers, and marine structures, mineral scaling reduces process efficiency and eventually leads to process failure. Therefore, achieving long-term scaling resistance is beneficial to enhancing process performance and reducing operating and maintenance costs. While evidence shows that superhydrophobic surfaces may reduce mineral scaling kinetics, prolonged scaling resistance is limited due to the finite stability of the entrained gas layer present in a Cassie–Baxter wetting state. Additionally, superhydrophobic surfaces are not always feasible for all applications, but strategies for long-term scaling resistance with smooth or even hydrophilic surfaces are often overlooked. In this study, we elucidate the role of interfacial nanobubbles on the scaling kinetics of submerged surfaces of varied wetting properties, including those that do not entrain a gas layer. We show that both solution conditions and surface wetting properties that promote interfacial bubble formation enhances scaling resistance. In the absence of interfacial bubbles, scaling kinetics decrease as surface energy decreases, while the presence of bulk nanobubbles enhances the scaling resistance of the surface with any wetting property. The findings in this study allude to scaling mitigation strategies that are enabled by solution and surface properties that promote the formation and stability of interfacial gas layers and provide insights to surface and process design for greater scaling resistance.

calcite↗
DOE OSTI2021

Interfacial and Confinement-Mediated Organization of Gas Hydrates, Water, Organic Fluids, and Nanoparticles for the Utilization of Subsurface Energy and Geological Resources

Harnessing the subsurface geologic environments in an efficient and environmentally sustainable manner is challenged by uncertainties associated with predicting the fate of fluids and sustaining porosity and permeability in subsurface geologic environments. Some of these uncertainties arise from confined and interfacially induced structures of fluids in subsurface geologic environments. The formation of gas hydrates, phase transitions of confined fluids, assembly and deposition of heavy hydrocarbons, and the agglomeration and fate of nanoparticles in confined environments are summarized in this review. Nanoscale confinement contributes to anisotropic structures and dynamics of fluids, which is the basis for anomalous phase transition thermodynamics, reactivity, transport, and geomechanical behavior. In this review, we discuss the structures of confined fluids and deviation in observed properties from bulk fluids. The factors influencing the structures of confined fluids can be generally divided into two groups: (a) pore characteristics including pore size, pore surface chemistry, and pore geometry and (b) confined fluid/solid characteristics such as molecular structure, concentrations, charges, pore filling, and presence of additives. Scientific advancements and knowledge gaps in our understanding of the structures of confined fluids and the associated differences in observed properties compared to bulk fluids are discussed. Here, the phenomena discussed in this review are of particular relevance to our efforts in harnessing the subsurface environments for a low carbon future by increasing the utilization of geothermal energy, using CO 2 as a working fluid, and storing CO 2 in subsurface geologic environments.

42 ENGINEERING↗
DOE OSTI2021

Strong Fermi-level pinning at metal contacts to halide perovskites

The performance of halide perovskite-based electronic and optoelectronic devices is often related to interfacial charge transport. To shed light on the underlying physical and chemical properties of CH 3 NH 3 PbI 3 (MAPbI 3 ) in direct contact with common electrodes Al, Ti, Cr, Ag, and Au, the evolution of interfacial properties and Fermi level pinning is systematically studied. Given a unique experimental facility, pristine interfaces without any exposure to ambient air were prepared. We observe aggregation of substantial amounts of metallic lead (Pb 0 ) at the metal/MAPbI 3 interface, resulting from the interfacial reaction between the deposited metal and iodine ions from MAPbI 3 . It is found that the Schottky barrier height at the metal/MAPbI 3 interface is independent of the metal work function due to strong Fermi level pinning, possibly due to the metallic Pb 0 aggregates, which act as interfacial trap sites. The charge neutrality level of MAPbI 3 is consistent with the energy level of Pb 0 -related defects, indicating that Pb 0 interfacial trap states can be nonradiative recombination sites. Here this work underlines that control of chemical bonding at interfaces is a key factor for designing future halide perovskite-based devices.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Determining the Crosslinking and Degradation Reaction Kinetics in Photovoltaic Encapsulants Using Accelerated Aging: Preprint

Degradation of photovoltaic (PV) module encapsulant mechanical characteristics that lead to embrittlement and delamination remains a cause of failure in solar installations. A multiscale reliability model based on detailed molecular degradation reaction kinetics was previously published, connecting the encapsulant mechanical properties (elastic modulus, yield strength, and adhesion energy) to the degraded molecular structure and interfacial bond density to adjacent solar cell and glass substrates. The model, developed primarily for poly(ethylene-co-vinyl acetate) (EVA) encapsulants, remains to be experimentally validated. Determining the degradation and crosslinking kinetics of alternative encapsulants, such as polyolefin elastomer (POE) and EVA/POE/EVA composites (EPE), can further generalize the model. Importantly, the activation energy for crosslinking of fully cured PV encapsulant products from temperature or UV is presently unknown or unavailable. In this work, we subject EVA, POE, and EPE encapsulants to a set of accelerated aging conditions, varying the temperature, UV intensity, and relative humidity. We use DSC, FTIR, and Soxhlet extraction (gel content) to characterize the encapsulants' changing molecular structure. This allows for determination of the photochemical degradation and crosslinking kinetics of the encapsulants. Preliminary results show an increase in gel content (crosslinking) and a decrease in crystallinity of EVA, POE, and EPE encapsulants under hot-aerobic (90 deg C, 22% RH) and hot-anaerobic (90oC, sealed in N2 air) accelerated aging, even in the absence of UV and crosslinking initiating agents. For a least squares regression with an assumed first-order crosslinking kinetics, the crosslinking rate parameters were computed for the three encapsulants under hot-aerobic and hot-anaerobic aging conditions. FTIR analysis showed insignificant encapsulant degradation for hot-aerobic and hot-anaerobic aging, demonstrating the critical role of UV and moisture in accelerating degradation. Aging conditions with UV exposure and elevated humidity are presently in progress.

adhesion↗
DOE OSTI2020

Ambient pressure x-ray photoelectron spectroscopy study of water formation and adsorption under two-dimensional silica and aluminosilicate layers on Pd(111)

Ambient pressure x-ray photoelectron spectroscopy (AP-XPS) supported by density functional theory (DFT) calculations was used to characterize the interaction of water with two-dimensional (2D) silica and aluminosilicate bilayers on Pd(111). Starting with oxygen adsorbed at the SiO2/Pd interface, exposure to water caused the SiO 2 -derived XPS peaks to shift to higher binding energy and the removal of an O 1s feature associated with interfacial adsorbed oxygen. These observations were attributed to the formation of a mixed water–hydroxyl interface, which eliminates the interfacial dipolar layer, and its associated electrostatic potential, created by adsorbed oxygen. Interfacial oxygen also reacted with H 2 to produce adsorbed water which also caused an upward binding energy shift of the SiO 2 peaks. Spectra recorded under 0.5 Torr water revealed additional water adsorption and a further shift of the overlayer peaks to higher binding energy. Incorporating Al into the 2D material caused the bilayer peaks to shift to lower binding energy which could be explained by electron donation from the metal to the bilayer. Although the stronger interaction between the bilayer and Pd substrate should restrict interfacial adsorption and reaction, similar trends were observed for water and hydrogen exposure to interfacial adsorbed oxygen. Less water adsorption was observed at the aluminosilicate interface which is a consequence of Al strengthening the bond to the metal substrate. The results reveal how the sensitivity of XPS to interfacial dipoles can be exploited to distinguish reactions taking place in confined spaces under 2D layers and how tuning the composition of the 2D layer can impact such reactions.

Density functional theory↗
DOE OSTI2021

Formation of pyrophosphates across grain boundaries induces the formation of mismatched but oriented interfaces in silver phosphate polypods

The interfaces and their misfit defects determine the materials properties for a wide range of applications, such as electronic devices, photocatalysis, and mechanical engineering, etc. However, current understanding of atomic interfacial structures is limited. Here we discover a special interfacial structure, mismatched but oriented interface via two distinct facets. Transmission and scanning electron microscopy results suggest that, in Ag 3 PO 4 polypods structures, interfaces of {1 0 0} and {1 1 0}, ({1 0 0}/(1 1 0}), {1 0 0}/{1 1 1}, {1 1 0}/{1 1 1}, and {1 0 0}/{1 0 0}, etc., have a certain orientation relationship, corresponding to the energy minima and coincident site lattice of interfacial atoms as demonstrated by molecular dynamics simulations. Density functional theory demonstrates that the formation of pyrophosphate and/or phosphates rotation to bond across the interface compensate the lattice mismatch at the interfaces, as well as deformations of Ag-O bonds. Furthermore, our work opens up a new avenue for a much wider range of interfacial structures, allow for a higher diversity of structures, and shine light on tailoring crystal structures, morphologies, and the resulting properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Visualizing the SEI formation between lithium metal and solid-state electrolyte

The solid electrolyte interphase (SEI) is regarded as the most important factor affecting the durability of lithium-metal anode in all-solid-state batteries (ASSBs). Despite its significance, the nucleation and growth mechanism of SEI is not yet well understood. Here, we elucidate the thermodynamics and kinetics governing SEI formation at the Li|β-Li 3 PS 4 interface at the atomic scale via thermodynamic phase equilibrium analysis and machine-learning-potential-assisted molecular dynamics (MD) simulations. An accurate moment tensor potential using the machine-learning method is developed for a reactive model of Li|β-Li 3 PS 4 . This potential enabled us to perform large-scale MD simulations with the model size expanded to the experimental dimensions (~40 nm) while maintaining the same level of accuracy as density functional theory calculations. The results reveal a four-stage evolution process at the Li|β-Li 3 PS 4 interface, namely (i) fast ion diffusion, (ii) nucleation, (iii) Li 2 S growth, and (iv) stabilization. Notably, we demonstrate that the SEI can be categorized into crystalline and amorphous regions. The simulated SEI thickness, structure, and composition closely match experimental findings, validating the accuracy of the MD simulations. We further disclose the significant impact of ion diffusion kinetic limitations on the phase formation and crystallization of interfacial products. Furthermore, we shed light on the detailed potential energy (PE) distribution of lithium along the direction perpendicular to the interface. Finally, this information is crucial for better understanding interfacial ion mobility.

25 ENERGY STORAGE↗
DOE OSTI2023

First-principles study of interfaces in Al/SiC metal-matrix composite system

In this work, first-principles calculations were performed on the interfaces between Al and SiC, which is a widely used strengthening agent in aluminum metal-matrix-composites (Al/MMC). C-terminated interfaces have much larger work of adhesion than Si-terminated interfaces, indicating that the former has much stronger interfacial bonding. The electron localization function shows that the chemical bonding between Al and C has a strong covalent character, while the bonding between Al and Si is largely metallic. As a result of the vastly different chemical bonding, the work of adhesion for C-terminated interfaces increases with the number of dangling bonds at the interface, while the opposite trend was observed for Si-terminated interfaces. Additionally, the interface energy for Si-terminated interfaces is comparable to that for C-terminated interfaces, suggesting both types of terminations can coexist in the Al/SiC system.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Formation of Mn-rich interfacial phases in Co 2 Fe x Mn 1-x Si thin films

Here, we report the formation of Mn-rich regions at the interface of Co 2 Fe x Mn 1-x Si thin films grown on GaAs substrates by molecular beam epitaxy (MBE). Scanning transmission electron microscopy (STEM) with electron energy loss (EEL) spectrum imaging reveals that each interfacial region: (1) is 1–2 nm wide, (2) occurs irrespective of the Fe/Mn composition ratio and in both Co-rich and Co-poor films, and (3) displaces both Co and Fe indiscriminately. We also observe a Mn-depleted region in each film directly above each Mn-rich interfacial layer, roughly 3 nm in width in the x = 0 and x = 0.3 films, and 1 nm in the x = 0.7 (less Mn) film. We posit that growth energetics favor Mn diffusion to the interface even when there is no significant Ga interdiffusion into the epitaxial film. Element-specific X-ray magnetic circular dichroism (XMCD) measurements show larger Co, Fe, and Mn orbital to spin magnetic moment ratios compared to bulk values across the Co 2 Fe x Mn 1-x Si compositional range. The values lie between reported values for pure bulk and nanostructured Co, Fe, and Mn materials, corroborating the non-uniform, layered nature of the material on the nanoscale. Finally, SQUID magnetometry demonstrates that the films deviate from the Slater-Pauling rule for uniform films of both the expected and the measured composition. The results inform a need for care and increased scrutiny when forming Mn-based magnetic thin films on III-V semiconductors like GaAs, particularly when films are on the order of 5 nm or when interface composition is critical to spin transport or other device applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Interfacial electronic states of misfit heterostructure between hexagonal ZnO and cubic NiO

The combination of materials with dissimilar symmetries can induce a large amount of stress at the interfacial layer of films, thereby promoting the appearance of novel properties in related devices. The study of the interfacial state is critical for determining the inner mechanism. In this work, the misfit heterostructure between cubic NiO films and wurtzite ZnO is investigated. A NiO film grown using molecular beam epitaxy on a ZnO substrate shows a highly (100)-oriented texture featuring three domains with a rotation angle of 30°, which is in agreement with first principles calculations. Misfit-induced dislocations and lattice distortions within the interfacial layers of the NiO film give rise to interfacial electronic states, which are different from those in bulk; these electronic states are analyzed by in situ synchrotron-based x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, x-ray absorption spectroscopy, and ex situ electron energy loss spectroscopy. Additionally, the origin of these interfacial states is discussed. This work aims to provide insights for the integration of semiconducting hexagonal ZnO with other functional materials that have a cubic symmetry. Additionally, we investigate the integration of photon and electron-based techniques to explore the interfacial states of complex interfaces, which is an important aspect of material science.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Angstrom-Resolved Interfacial Structure in Buried Organic-Inorganic Junctions

Charge transport processes at interfaces which are governed by complex interfacial electronic structure play a crucial role in catalytic reactions, energy storage, photovoltaics, and many biological processes. Here, the first soft X-ray second harmonic generation (SXR-SHG) interfacial spectrum of a buried interface (boron/Parylene-N) is reported. SXR-SHG shows distinct spectral features that are not observed in X-ray absorption spectra, demonstrating its extraordinary interfacial sensitivity. Comparison to electronic structure calculations indicates a boron-organic separation distance of 1.9 {\AA}, wherein changes as small as 0.1 {\AA} result in easily detectable SXR-SHG spectral shifts (ca. 100s of meV). As SXR-SHG is inherently ultrafast and sensitive to individual atomic layers, it creates the possibility to study a variety of interfacial processes, e.g. catalysis, with ultrafast time resolution and bond specificity.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Structural and electrochemical evolution of alloy interfacial layers in anode-free solid-state batteries

“Anode-free” solid-state batteries feature high energy density since there is no anode active material. Although the beneficial effects of interfacial layers at the anode-solid electrolyte interface have been demonstrated, the mechanisms through which they influence lithium plating/stripping are unclear. Here, in this study, we reveal the evolution of 100-nm silver and gold interfacial layers during lithium plating/stripping using electrochemical methods, electron microscopy, X-ray microcomputed tomography, and modeling. The alloy layers improve Coulombic efficiency and resistance to short circuiting, even though the alloys form solute regions or particulates that detach from the current collector during plating. In situ electrochemical impedance spectroscopy shows that the alloys return to the interface and mitigate contact loss at the end of stripping, avoiding a critical vulnerability of anode-free cells. Contact retention is driven by even Li thickness that promotes spatially uniform stripping, as well as local alloy delithiation in response to current concentrations that homogenizes current and diminishes voiding.

25 ENERGY STORAGE↗
DOE OSTI2021

Interfacial stabilization for inverted perovskite solar cells with long-term stability

Perovskite solar cells (PSCs) commonly exhibit significant performance degradation due to ion migration through the top charge transport layer and ultimately metal electrode corrosion. Here, we demonstrate an interfacial management strategy using a boron chloride subphthalocyanine (Cl 6 SubPc)/fullerene electron-transport layer, which not only passivates the interfacial defects in the perovskite, but also suppresses halide diffusion as evidenced by multiple techniques, including visual element mapping by electron energy loss spectroscopy. As a result, we obtain inverted PSCs with an efficiency of 22.0% (21.3% certified), shelf life of 7000 h, Τ 80 of 816 h under damp heat stress (compared to less than 20 h without Cl 6 SubPc), and initial performance retention of 98% after 2000 h at 80 °C in inert environment, 90% after 2034 h of illumination and maximum power point tracking in ambient for encapsulated devices and 95% after 1272 h outdoor testing ISOS-O-1. Our strategy and results pave a new way to move PSCs forward to their potential commercialization solidly.

14 SOLAR ENERGY↗
DOE OSTI2025

Simulation insights into wetting properties of hydrogen-brine-clay for hydrogen geo-storage

Hydrogen geo-storage is attracting substantial interdisciplinary interest as a cost-effective and sustainable option for medium- and long-term storage. Hydrogen can be stored underground in diverse formations, including aquifers, salt caverns, and depleted oil and gas reservoirs. The wetting dynamics of the hydrogen-brine-rock system are critical for assessing both structural and residual storage capacities, and ensuring containment safety. Through molecular dynamics simulations, we explore how varying concentrations of cushion gases (CO 2 or CH 4 ) influence the wetting properties of hydrogen-brine-clay systems under geological conditions (15 MPa and 333 K). We employed models of talc and the hydroxylated basal face of kaolinite (kaoOH) as clay substrates. Our findings reveal that the effect of cushion gases on hydrogen-brine-clay wettability is strongly dependent on the clay-brine interactions. Notably, CO 2 and CH 4 reduce the water wettability of talc in hydrogen-brine-talc systems, while exerting no influence on the wettability of hydrogen-brine-kaoOH systems. Detailed analysis of free energy of cavity formation near clay surfaces, clay-brine interfacial tensions, and the Willard-Chandler surface for gas-brine interfaces elucidate the molecular mechanisms underlying wettability changes. Our simulations identify empirical correlations between wetting properties and the average free energy required to perturb a flat interface when clay-brine interactions are less dominant. Here, our thorough thermodynamic analysis of rock-fluid and fluid-fluid interactions, aligning with key experimental observations, underscores the utility of simulated interfacial properties in refining contact angle measurements and predicting experimentally relevant properties. These insights significantly enhance the assessment of gas geo-storage potential. Prospectively, the approaches and findings obtained from this study could form a basis for more advanced multiscale simulations that consider a range of geological and operational variables, potentially guiding the development and improvement of geo-storage systems in general, with a particular focus on hydrogen storage.

25 ENERGY STORAGE↗
DOE OSTI2022

Ultrahigh rate capability of manganese based olivine cathodes enabled by interfacial electron transport enhancement

In this study, manganese-based Olivine is a promising cathode candidate with high energy and low cost for Li-ion batteries (LIBs). Its rate capability and cyclability challenges still remain even with nano-size and carbon coating. Herein, an ultrahigh rate performance is achieved by introducing an affinitive conductor to enhance the interfacial electron transport of LiMn 0.7 Fe 0.3 PO 4 via Li 3 V 2 (PO 4 ) 3 . It is found that the Li 3 V 2 (PO 4 ) 3 facilitates sp 2 hybridization to form a highly conductive carbon coating during the carbonized process. The composite 0.9LiMn 0.7 -Fe 0.3 PO 4 .0.1Li 3 V 2 (PO 4 ) 3 can deliver a capacity of 90.9 mAh g -1 and power density of 11444 W kg -1 at 50 C-rate. Both in situ X-ray diffraction and conductive-atomic force microscopy are conducted to understand the synergetic effect between LiMn 0.7 Fe 0.3 PO 4 and Li 3 V 2 (PO 4 ) 3 . The results suggest that the interfacial electron transfer between LiMn 0.2 Fe 0.3 PO 4 particles and the electron conducting medium, such as binder/carbon black composite, is greatly improved so that the highly Li + conductive nature of olivine materials can be fully unleashed. This work demonstrates the importance of efficient interfacial electron transfer to the active cathode particles, and opens up a new venue for the rational design of high-energy and high-power batteries.

25 ENERGY STORAGE↗