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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Surface Reordering During Layer‐by‐Layer Growth on SrTiO 3

With the development of layer‐by‐layer growth techniques such as molecular beam epitaxy (MBE), it is now possible to construct materials with atomic‐level precision, with the layer sequence primarily determined by the growth recipe. However, materials can still restructure in the high‐temperature growth environment with surface thermodynamics strongly influencing growth behavior. Here, we demonstrate that growth on ${\rm SrTiO}_{3}$ (001), the principal platform for oxide electronics, does not occur in a layer‐by‐layer fashion but follows a more complex process in which a ${\rm TiO}_{2}$ plane continually diffuses toward the growth surface. Employing in situ synchrotron X‐ray scattering combined with ab initio thermodynamic calculations, we discover the existence of a stable ${\rm TiO}_{2}$ double‐layer structure on the pristine substrate and the occurrence of dynamic layer rearrangement during homoepitaxial growth by oxide MBE. Our findings suggest that the current methods used to precisely control ${\rm SrTiO}_{3}$ surfaces are limited, as well as our ability to dictate the composition of ultrathin films, resulting in important ramifications regarding the surface reactivity of perovskite materials grown on ${\rm SrTiO}_{3}$.

Coherent Bragg Rod Analysis↗
DOE OSTI2025

Tunable broadband luminescence in lead-free hybrid copper halides

Metal halides are an important class of optoelectronic materials combining exceptional optical and electronic properties. An inherent advantage of metal halides is their solution synthesis and processability, which render them as low-cost and environmentally friendly materials for a range of applications from photovoltaics and photodetection to solid-state lighting (SSL). Here, in this study, we synthesized three previously unreported lead-free organic–inorganic hybrid copper halides: (OA) 4 CuX 5 (X = Br, I; OA + = C 8 H 17 NH 3+ , n-octylammonium cation) and (HA) 2 CuI 3 (HA + = C 6 H 13 NH 3 + , n-hexylammonium cation), all of which exhibit broadband emissions arising from self-trapped excitons (STEs). Among these compounds, (OA) 4 CuI 5 demonstrates tunable dual-band white-light emission with a high color rendering index value of 91 at room temperature. Temperature-dependent photoluminescence measurements and first-principles calculations reveal distinct behaviors between the two emission states in (OA) 4 CuI 5 . These findings highlight the potential of copper halide compounds for optoelectronic applications, particularly in the development of environmentally friendly solid-state lighting technologies.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quantifying Size Effects on Thermal Transport in CsPbBr 3 Nanocrystal Films

Colloidal lead halide perovskite nanocrystals (LHP NCs) are promising semiconductor materials for optoelectronic applications due to their strong quantum confinement, near-unity photoluminescence quantum yields, and tunable emission characteristics. However, their modest thermal stability remains a challenge, particularly at smaller core diameters due to enhanced phonon scattering at inorganic core-organic ligand interfaces. In this work, we directly quantify size-dependent thermal conductivity (κ) in lecithin-capped CsPbBr 3 NC thin films using a transducer-free, vibrational pump–visible probe (VPVP) spectroscopy technique. A mid-infrared pump thermally excites the ligand shell, while a broadband probe tracks transient reflectance change correlated to lattice temperature decay. Finite-element modeling of the decay dynamics yields κ values from 0.13 to 0.16 W·m –1 ·K –1 for NC films with sub-10 nm core diameter, significantly lower than those of its bulk counterpart. A steep κ suppression with decreasing NC size emphasizes the dominant role of ligand shells and boundary effects in thermal transport.

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

Stability Enhancement in Na 0.67 Fe 0.2 Mn 0.8 O 2 Positive Electrodes via Spherical Coprecipitated Hydroxide Precursor Synthesis for Na-Ion Batteries

Mn/Fe-based layered transition metal oxides (LTMOs) are promising positive electrode materials for sodium-ion batteries (SIBs) due to their high abundance, low cost, and stable price fluctuations. At commercial scale, the fabrication of these materials commonly employs coprecipitation of hydroxide precursors, which allows for the scalable synthesis of uniform, dense particles with a tunable morphology. However, the common chelating agent (ammonia) forms unstable complexes with Fe 2+ ions, resulting in uncontrollable particle morphology and poor electrochemical properties. Here, in this study, three chelation strategies (no chelation, ammonia, oxalate) for Fe/Mn-based hydroxides are evaluated. It was found that oxalate chelation produced uniform, dense spherical hydroxide particles while particles via ammonia / no chelate routes exhibited no morphological control. The LTMOs synthesized from the oxalate-chelated hydroxide precursor formed uniform spherical particles, while the other two LTMOs showed greater variation in particle morphology. The oxalate-chelated LTMO electrode exhibited increased cycling stability due to reduced parasitic reactions with the electrolyte, as characterized by static leakage current measurements and electrochemical impedance spectroscopy.

25 ENERGY STORAGE↗
DOE OSTI2023

Phase engineering of layered anode materials during ion-intercalation in Van der Waal heterostructures

Transition metal dichalcogenides (TMDs) are a class of 2D materials demonstrating promising properties, such as high capacities and cycling stabilities, making them strong candidates to replace graphitic anodes in lithium-ion batteries. However, certain TMDs, for instance, MoS 2 , undergo a phase transformation from 2H to 1T during intercalation that can affect the mobility of the intercalating ions, the anode voltage, and the reversible capacity. In contrast, select TMDs, for instance, NbS 2 and VS 2 , resist this type of phase transformation during Li-ion intercalation. This manuscript uses density functional theory simulations to investigate the phase transformation of TMD heterostructures during Li-, Na-, and K-ion intercalation. The simulations suggest that while stacking MoS 2 layers with NbS 2 layers is unable to limit this 2H → 1T transformation in MoS 2 during Li-ion intercalation, the interfaces effectively stabilize the 2H phase of MoS 2 during Na- and K-ion intercalation. However, stacking MoS 2 layers with VS 2 is able to suppress the 2H → 1T transformation of MoS 2 during the intercalation of Li, Na, and K-ions. The creation of TMD heterostructures by stacking MoS 2 with layers of non-transforming TMDs also renders theoretical capacities and electrical conductivities that are higher than that of bulk MoS 2 .

25 ENERGY STORAGE↗
DOE OSTI2025

Halide segregation to boost all-solid-state lithium-chalcogen batteries

Mixing electroactive materials, solid-state electrolytes, and conductive carbon to fabricate composite electrodes is the most practiced but least understood process in all-solid-state batteries, which strongly dictates interfacial stability and charge transport. Here, we report on universal halide segregation at interfaces across various halogen-containing solid-state electrolytes and a family of high-energy chalcogen cathodes enabled by mechanochemical reaction during ultrahigh-speed mixing. Bulk and interface characterizations by multimodal synchrotron x-ray probes and cryo–transmission electron microscopy show that the in situ segregated lithium halide interfacial layers substantially boost effective ion transport and suppress the volume change of bulk chalcogen cathodes. Various all-solid-state lithium-chalcogen cells demonstrate utilization close to 100% and extraordinary cycling stability at commercial-level areal capacities.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Polymorphism and Phase Control in Dion–Jacobson 2D 3-(Aminomethyl)piperidinium-Based Metal Iodide Perovskites

Two-dimensional halide perovskites exhibit rich structural diversity and tunable optoelectronic properties, making them promising materials for energy, sensing, and photonic applications. In this work, we report the structural mapping of four distinct polymorphs, γ (P2 1 /c), β (P4/mbm), α (P4/mmm), and δ (Cmcm) in the two-dimensional iodoplumbate, iodostannate, and iodogermanate perovskite so-called Dion-Jacobson series (3AMP)MI4 (M = Sn, Pb, Ge), where 3AMP is 3-(aminomethyl)piperidinium. The phases exhibit systematic evolution in octahedral distortion, lattice symmetry, and metal–halide geometry, enabling structural control over optoelectronic properties. Notably, the α-phase of (3AMP)SnI 4 represents a rare, ambient-stable, high-symmetry structure for Sn-based perovskites, without a phase transition down to 100 K. Variable-temperature single-crystal diffraction, powder x-ray diffraction (PXRD), and calorimetry reveal metal- and temperature-dependent polymorph interconversions, including the emergence of long range supercell reflections in Pb-rich compositions at low temperature. Optical spectroscopy and photoelectron yield spectroscopy confirm band gap tunability and band alignment trends, highlighting symmetry-dependent shifts and anomalous band gap bowing in mixed-metal systems, verified by electronic structure calculations. Calculations additionally indicate that the higher symmetry phases have reduced electron and hole effective masses compared to the lower symmetry phases.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Efficient Mn 2+ Doping in Non-Stoichiometric Cesium Lead Bromide Perovskite Quantum Dots

Doping magnetic transition metal ions (e.g., Mn 2+ ) into colloidal quantum dots endows novel optical and magnetic properties to the host materials. CsPbBr 3 quantum dots (QDs) are emerging light-emitting materials with high structural and chemical flexibility in the visible spectral regime. However, efficiently doping Mn 2+ ions in CsPbBr 3 QDs remains challenging, especially when size confinement and ensemble uniformity are needed for understanding the underexplored exciton-dopant exchange interaction. Here, we introduce a doping mechanism based on electrostatic surface Mn 2+ adsorption that enables efficient Mn 2+ incorporation in strongly confined CsPbBr 3 QDs. The resultant QDs are found to have a Cs-deficient stoichiometry compared to their undoped counterparts. A redox reaction-based purification method was developed to remove Mn 2+ cations that are tightly adsorbed on the surface to determine the concentration of lattice-incorporated Mn 2+ . Our synthesis enables a Mn 2+ doping/alloying concentration of up to ∼44% with a Mn 2+ photoluminescence efficiency exceeding 90%. This allows for the determination of the intrinsic exciton-to-dopant energy transfer rate.

Hidayatova, Lamia [Univ. of Oklahoma, Norman, OK (↗
DOE OSTI2025

Solution‐Processed Spin‐Polarized Light‐Emitting Diodes of Colloidal Quantum Wells and Magnetic Nanoparticles

Electrical injection of spin-polarized carriers into semiconductors enables circularly-polarized emission from spin-polarized light-emitting diodes (spin-LEDs). The incredible level of tunability of magnetic and electronic properties in colloidal nanocrystals offers unprecedented opportunities for the modulation of polarization of light in solution-processed spin-LEDs based on magnetic nanoparticles unlike epitaxially grown spin-LEDs restricted by a very limited range of materials for their exploitation, and solution-processed spin-LEDs based on chiral molecules, which do not allow the modulation of polarization in general. Here, it is shown that electrical injection of spin-polarized electrons from magnetic Fe 3 O 4 nanoparticles into CdSe/CdZnS core/shell colloidal quantum wells (CQWs) in solution-processed LEDs that allows for polarization modulation of electroluminescence. In this structure, a monolayer of face-down oriented CQWs is deposited as an active layer to avoid polarization losses due to the hopping of the electrons between the CQWs before the radiative recombination process. In this solution-processed spin-LED, the circular polarization reaches 4.5% at 3 K and survives up to 100 K. A net circular polarization is observed at zero magnetic field up to 100 K because of the remnant magnetization of the Fe 3 O 4 nanoparticles. This new colloidal spin-LED architecture presents significant prospects for future solution-processed advanced opto-spintronic devices.

circularly polarized electroluminescence↗
DOE OSTI2026

Colloidal Synthesis of Palladium Nanocluster‐Decorated Cs 3 Sb 2 Cl 9 Perovskite Heterostructural Nanorods for Enhanced CO 2 Photoreduction

Developing efficient and sustainable photocatalysts for CO 2 reduction remains a significant challenge, particularly with environmentally benign materials. Here, in this study, we report the first one-step synthesis of metal–lead-free perovskite heterostructural nanocrystals by decorating Cs 3 Sb 2 Cl 9 perovskite nanorods with size-controlled Pd nanoclusters via a one-step hot-injection method. The resulting Pd-Cs 3 Sb 2 Cl 9 heteronanorods (HNRs) exhibit strong interfacial electronic coupling, enhanced charge separation, and excellent colloidal stability. Transient absorption spectroscopy and DFT calculations reveal a built-in electric field that drives directional electron transfer from the perovskite host to the Pd domains. Under UV irradiation, the Pd-Cs 3 Sb 2 Cl 9 HNRs demonstrate excellent CO 2 photoreduction activity with high CH 4 selectivity, achieving a record apparent quantum yield (AQY) of 2.62% among halide perovskite nanocrystal-based systems with a large electronic yield of 689.3 ± 12.2 µmol·g cat −1 . In situ spectroscopic monitoring and Gibbs free energy analysis further unveil a Pd-facilitated reaction pathway involving stabilization of key intermediates. This work introduces a new class of lead-free perovskite-based heterostructures through a facile one-step synthesis strategy and offers a new design principle for next-generation photocatalysts for solar fuel production.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Li 3.6 In 7 S 11.8 Cl: an air- and moisture-stable superionic conductor

Li 3.6 In 7 S 11.8 Cl has a face-centered cubic arrangement of S 2− /Cl − stabilized by Li + /In 3+ that form 3D ion conduction paths. The moisture stability and fast ion conduction make Li 3.6 In 7 S 11.8 Cl a promising electrolyte for solid-state batteries.

Oyekunle, Ifeoluwa P. [Department of Chemistry and↗
DOE OSTI2020

Size- and Temperature-Dependent Suppression of Phonon Thermal Conductivity in Carbon Nanotube Thermoelectric Films

Heat transport in nanoscale carbon materials such as carbon nanotubes and graphene is normally dominated by phonons. Here, measurements of in-plane thermal conductivity, electrical conductivity, and thermopower are presented from 77–350 K on two films with thickness <100 nm formed from semiconducting single-walled carbon nanotubes. These measurements are made with silicon–nitride membrane thermal isolation platforms. The two films, formed from disordered networks of tubes with differing tube and bundle size, have very different thermal conductivity. One film matches a simple model of heat conduction assuming constant phonon velocity and mean free path, and 3D Debye heat capacity with a Debye temperature of 770 K. The second film shows a more complicated temperature dependence, with a dramatic drop in a relatively narrow window near 200 K where phonon contributions to thermal conductivity essentially vanish. This causes a corresponding large increase in thermoelectric figure-of-merit at the same temperature. A better understanding of this behavior can allow significant improvement in thermoelectric efficiency of these low-cost earth-abundant, organic electronic materials. Finally, heat and charge conductivity near room temperature is also presented as a function of doping, which provides further information on the interaction of dopant molecules and phonon transport in disordered nanotube films.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Observation of Topological Spin Textures in Ferrimagnetic Mn 2 − x Zn x Sb

Ferrimagnets, which have both ferromagnetic and antiferromagnetic coupling, are attracting increased attention in the realm of spintronic devices due to advantages such as ultrafast dynamics and a suppressed skyrmion Hall effect. Thus, understanding the behavior of nontrivial spin textures in ferrimagnets is crucial; however, comprehensive reports on this topic remain limited. Here, the magnetic spin textures of ferrimagnetic Mn 2 − x Zn x Sb (x = 0.85) is explored as a function of temperature and applied magnetic field. The spin textures can be tuned to a variety of states, including stripes, skyrmion bags, and a skyrmion lattice. Chiral Néel-type magnetic structures are visualized using Lorentz transmission electron microscopy. Mn(I) ions are slightly shifted toward the Sb sites, which may be due to a strong electrostatic interaction between Mn and Sb ions. This local structural distortion breaks the inversion symmetry and introduces an effective Dzyaloshinkii–Moriya interaction. This work thus provides a pathway to use doping and heterogeneity in a ferrimagnet to control and generate chiral nontrivial spin textures.

Mn ion displacement↗
DOE OSTI2025

Decoding Antenna Behavior in Metal—Organic Frameworks

Metal–organic frameworks (MOFs) define a solid-state platform for developing artificial photosystems. Efficient anisotropic exciton migrations in these frameworks entail “antenna behavior” that can power up the distal interior reaction centers (RC), driving charge separation between donor-acceptor pairs. Reminiscent of the natural light-harvesting complex, such processes can achieve high quantum yield by exploiting the vast interior surface of the porous crystallites. It is important to understand the optimum positioning of the RC site relative to the anisotropic exciton migration path within these frameworks. The efficiency of such antenna behavior is probed here through Stern–Volmer (SV) type analysis with a series of node-anchored redox quenchers, ferrocene-carboxylate, ferrocene acetate, and dinitrobenzoate. Decoding various intrinsic processes, this work constructs a revised SV formalism in solid assembly that hosts ultrafast anisotropic exciton migration to account for the intrinsic exciton hopping rate from the extrinsic electron transfer rate, and the dimension of effective quenching. In conclusion, this transformative understanding can be applied to other relevant solid-state assemblies.

Saha, Bapan [Southern Illinois University, Carbond↗
DOE OSTI2025

An Oxygen‐Scavenger Sulfide Coating Enabling Long‐Term Stable Nickel‐Rich Cathodes

Oxygen release is a major issue associated with layer-structured metal oxide cathodes in lithium batteries, which can further cause a series of problems, such as irreversible phase transition, microcracking, and electrolyte decomposition. Eventually, these issues jointly result in cell performance degradation and safety hazards. Thus, it is very significant to tackle oxygen release for achieving long-term stable cyclability, but very challenging. Although intensive efforts have been invested to date, there still lacks a feasible solution. In this study, nanoscale ZrS 2 coatings are applied on prefabricated LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathodes directly via atomic layer deposition (ALD). Very encouragingly, we reveal that this ALD-deposited conformal ZrS 2 nanocoating can serve as an exceptional oxygen scavenger and then convert into a stable sulfate (Zr(SO 4 ) 2 ) coating. Such an in situ conversion is very beneficial and effective for protecting the electrolyte from decomposition. In addition, the resultant Zr(SO 4 ) 2 coating further inhibits undesirable reactions, stabilizes the interface between NMC811 and the electrolyte, suppresses microcracking, mitigates transition metal dissolution, and maintains the structural stability of the NMC811 cathode. Consequently, the ZrS 2 -coated NMC811 cathode has demonstrated extraordinary performance. Thus, this study advances the understanding of interface engineering while paving a new technical pathway for commercializing NMC811 cathodes.

Nickel-rich cathodes↗
DOE OSTI2025

Rapid synthesis of phase-engineered tungsten carbide electrocatalysts via flash joule heating for high-current-density hydrogen evolution

Fabricating durable and high-performance electrocatalysts operating at high current densities for industrial acidic hydrogen evolution remains a daunting challenge. Tailoring the phase composition of electrocatalysts is a promising strategy to harness synergistic effects and improve charge transfer, thereby optimizing their performance. Here, this work presents a fast, green method based on flash joule heating (FJH) to synthesize phase-engineered tungsten carbide electrocatalysts for the acidic hydrogen evolution reaction (HER) at high current densities. Tungsten carbide electrodes with varying FJH treatment durations (3, 10, 30, and 60 s) are fabricated to fine-tune the mixture of tungsten monocarbide (WC) and tungsten semicarbide (W 2 C) phases. Results show that samples with a 30-s treatment (TC-3) exhibit an optimal balance between these phases, leading to a low overpotential of 180.97 and 387 mV at current densities of 10 mA/cm 2 and 4 A/cm 2 , respectively. TC-3 exhibits significantly lower charge transfer resistance compared to the other electrocatalysts, which can be attributed to its optimal phase ratio. Notably, the TC-3 electrocatalyst remains stable for over 9 days at 4 A/cm 2 due to their controlled phases and excellent corrosion-resistant properties. This work highlights a new method to fabricate cost-effective, high-performance tungsten carbide electrocatalysts with well-controlled phase compositions.

Acidic hydrogen evolution reaction↗
DOE OSTI2025

Synthesis of multicomponent oxygen evolution reaction coatings via block copolymer templating with vapor- and solution-phase precursors

Porous mixed transition metal oxide heterostructures are promising electrocatalysts due to their high surface area. However, achieving conformal multicomponent oxide coatings with controlled nanoscale architectures remains challenging. Here, we report a synthesis strategy that integrates solution-based swelling infiltration (SBI) with gas-phase sequential infiltration synthesis (SIS) in a block copolymer template to fabricate porous, high-surface-area, conformal mixed-oxide electrocatalytic coatings. In this approach, a PS75-P4VP25 block copolymer (BCP) film is first infiltrated with transition metal acetylacetonate precursors via SBI, followed by exposure to gas phase precursors of ZnO via SIS process. Thermal annealing of the infiltrated BCP films converts them into all-inorganic Fe–ZnO, Fe–Co–ZnO, and Fe–Ni–ZnO coatings. Electrochemical testing on 70 nm thick conformal coatings demonstrates promising oxygen evolution reaction (OER) activity in alkaline media, with mass-specific current densities up to 1.0 × 10 5 mA/g at an overpotential of 330 mV (vs. RHE) at ultralow loading (~0.005 g/cm 2 ). Among the compositions, Fe–Co–ZnO and amorphous Fe–Ni–ZnO show the best OER performance, delivering current densities of 2.00 and 3.04 mA/cm 2 , respectively, compared to 1.52 mA/cm 2 for Fe–ZnO.. This work establishes SBI–SIS as a versatile route for fabricating nm-thin, high-performance multicomponent oxide heterostructures on cost-efficient supports, enabling efficient catalyst utilization in electrochemical energy conversion application.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗