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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Delineating the kinetic limitations of Mn 2+/3+ redox in LiMn x Fe 1−x PO 4 cathodes for lithium-ion batteries

LiMn x Fe 1−x PO 4 (LMFP) cathodes offer higher energy density than LiFePO 4 due to a higher operating voltage. However, the kinetic limitations of the Mn 2+/3+ redox couple in LMFP restrict its practically achievable capacity and hinder the ability to achieve high energy density. While the shortcomings of Mn 2+/3+ redox are recognized, its behavior and the factors that impact it remain to be fully understood. We present here an in-depth kinetics study of LMFP by utilizing novel techniques, such as chronoamperometry and galvanostatic electrochemical impedance spectroscopy. Compared to moderate-Mn LMFP (40–60% Mn), high-Mn LMFP (80% Mn) experiences reduced capacity, poor rate capability, and heightened impedance during Mn 2+/3+ redox. The oxidation of Mn 2+ to Mn 3+ becomes more resistive during charge due to the formation of Jahn–Teller active Mn 3+ and the increasing charge-transfer insulating behavior of Mn x Fe 1−x PO 4 . However, the impedance associated with Mn 3+ to Mn 2+ reduction remains constant during discharge in the entire region. The protracted Mn2+ oxidation in high-Mn LMFP results in excessive impedance compared to that in moderate-Mn LMFP, even at low C-rates and high cycling temperatures. Despite the promise of high energy density, the extreme kinetic limitations inherent to high-Mn LMFP present a barrier.

25 ENERGY STORAGE↗
DOE OSTI2026

Sequential surface synthesis of dispersed sub-nanometer iridium on titanium nitride for acidic water oxidation

Maximizing iridium utilization while maintaining high oxygen evolution reaction (OER) performance remains a persistent challenge in acidic water electrolysis. Immobilizing Ir on conductive, acid-stable supports is promising, yet simultaneously achieving sub-nanometer size, high area coverage, and strong electronic coupling is difficult. Here, we report a sequential surface synthesis on titanium nitride (TiN) that yields uniformly distributed sub-nanometer Ir arrays (∼0.7 nm). Our method uses ethylenediaminetetraacetic acid (EDTA) as a temporal scaffold: it chemisorbs to TiN to install dense chelating sites, captures Ir 3+ ions, and confines Ir cluster growth. A subsequent thermal treatment at 500 °C in a reducing atmosphere removes the ligand shell, while preserving ultrasmall particle size and establishing direct Ir–TiN electronic coupling. The optimized catalyst exhibits mixed Ir 0 /Ir x+ coordination with low charge-transfer resistance (R ct = 19.2 Ω), delivering a mass activity of 342 A g Ir −1 at 1.54 V in acidic electrolyte. In situ X-ray absorption spectroscopy reveals irreversible surface oxidation as the primary stability-limiting factor. This stepwise strategy provides a general framework for supported catalysts that maximize precious metal utilization via sub-nanometer dispersion.

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

Effect of ground-state charge transfer on photoexcited charge transfer in transition metal dichalcogenide heterostructures

We report an experimental investigation on the effect of ground-state charge transfer and its induced electric field on photoexcited charge transfer in van der Waals heterostructures. Two heterostructure samples were fabricated by stacking an undoped WSe 2 monolayer with either a Nb-doped or undoped MoSe 2 monolayer. While no ground-state charge transfer is expected in the MoSe 2 /WSe 2 heterostructure, the doped holes in the MoSe 2 :Nb/WSe 2 heterostructure can transfer to WSe 2 , creating a space-charge electric field. By comparing the photoluminescence and time-resolved differential reflectance of the two heterostructures, we find that photoexcited hole transfer from MoSe 2 to WSe 2 is largely blocked by this field, whereas photoexcited electron transfer from WSe 2 to MoSe 2 is less affected. Furthermore, these results provide insight into the impact of doping on the charge-transfer performance of van der Waals heterostructures.

2D materials↗
DOE OSTI2026

Excited-state vibronic coherences and intramolecular charge transfer dynamics of the photoinactive cyanobacteriochrome NpF2164g5

We have characterized the excited-state structural dynamics that follow optical excitation of the photoinactive cyanobacteriochrome (CBCR) NpF2164g5 to determine the first events along the photoisomerization reaction coordinate of the phycocyanobilin (PCB) chromophore in red-to-green photoactive CBCRs. Within 25 fs of photoexcitation to the first excited singlet state, S1, a cross peak begins to develop below the diagonal of the broadband two-dimensional electronic spectrum (2DES) owing to the formation of a twisted conformation of the PCB chromophore with an enhanced intramolecular charge-transfer (ICT) character. Excited-state coherent wavepacket motions, including a torsion of the methine bridge between rings C and D and the carbon–hydrogen out-of-plane (HOOP) wagging vibration, are rapidly damped as the cross peak forms. This finding supports an assignment of the torsional and HOOP modes to the reaction coordinate of a coherent nonadiabatic mechanism. The ICT process is accompanied by an ultrafast Stokes shift and rapidly damped oscillations at the torsional mode’s frequency, which are sensed by measurements of the energy gap of the cross peak using its first moment with respect to the detection frequency axis of the 2DES spectrum. Furthermore, these results have the further implication that polar side chains of nearby amino acid residues in the binding site of the PCB chromophore can manipulate the barrier height for photoisomerization in red-to-green photoactive CBCRs and in phytochromes by redistributing the π-electron density along the methine bridge between the C and D rings.

Charge transfer↗
DOE OSTI2026

Solvent effects on triplet yields in BODIPY-based photosensitizers

Here, we employ molecular dynamics simulations and quantum rate theories to elucidate the complex condensed-phase dynamics underpinning triplet-state formation in organic photosensitizers. Using models informed by first-principles calculations complete with a molecular representation of solvents of different polarities, we elucidate the interplay of the internal and environmental interactions underlying triplet yield. We find that triplet yields depend sensitively on the dielectric stabilization of the charge transfer intermediate that facilitates a transition into the triplet manifold. Our results illustrate the importance of molecularly detailed models in understanding the excited-state internal charge-transfer dynamics of photochemically relevant organic molecules.

Coello Escalante, Leonardo [University of Californ↗
DOE OSTI2026

Local Structural Coherence and Interfacial Charge Transfer in Cu 2 ⁢S/Mo⁢S 2 Heterostructure

Precise control over electronic coupling at nanoscale interfaces is critical for designing materials with tunable charge-transfer behavior and catalytic function. Heterostructures with locally coherent interfaces provide a platform for interrogating interfacial charge redistribution in coupled material systems. Here, we report Cu 2 ⁢S/Mo⁢S 2 heterostructures exhibiting nanoscale crystallographic alignment, which are synthesized through a rapid thermal transformation pathway. We employed electrochemical reduction reactions to probe interfacial charge transfer, revealing shifts in product distribution attributable to modified interfacial energetics, even in the absence of optimized catalytic performance. The observed formate Faradaic efficiency suggests that interfacial electronic modulation in the heterostructure shifts product selectivity towards formate, highlighting how interface-driven electronic modulation can direct reaction pathways and influence product selectivity. Optimizing catalyst loading, architecture, and reactor configuration will be critical for future improvement. Structural and compositional integrity were confirmed through powder x-ray diffraction, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Electron transfer between Cu 2 ⁢S and Mo⁢S 2 domains was further evaluated by electrochemical impedance spectroscopy, while selected-area electron diffraction revealed local crystallographic alignment consistent with a local epitaxial relationship at the Cu 2 S/Mo⁢S 2 heterointerface. To illustrate the broader applicability of this approach, a Zn⁢S/Mo⁢S 2 heterostructure was also synthesized using the same microwave strategy, confirming the generalizability of interfacial engineering principles across metal sulfide-Mo⁢S 2 systems. Collectively, these findings demonstrate that controlled local epitaxial alignment serves as an effective design principle for tuning interfacial energetics and catalytic reactivity in complex heterostructure materials.

carbon capture & utilization↗
DOE OSTI2024

Electronic structure, self-doping, and superconducting instability in the alternating single-layer trilayer stacking nickelates La 3 ⁢Ni 2 ⁢O 7

Motivated by the recently proposed alternating single-layer trilayer stacking structure for the nickelate La 3 ⁢Ni 2 ⁢O 7 , we comprehensively study this system using ab initio and random-phase approximation techniques. Here, our analysis unveils similarities between this novel La 3⁢ Ni 2 ⁢O 7 structure and other Ruddlesden-Popper nickelate superconductors, such as a similar charge-transfer gap value and orbital-selective behavior of the eg orbitals. Pressure primarily increases the bandwidths of the Ni e g bands, suggesting an enhancement of the itinerant properties of those e g states. By changing the cell volume ratio V/V 0 from 0.9 to 1.10, we found that the bilayer structure in La 3 ⁢Ni 2 ⁢O 7 always has lower energy than the single-layer trilayer stacking La 3 ⁢Ni 2 ⁢O 7 . In addition, we observe a “self-doping” effect (compared to the average 1.5 electrons per eg orbital per site of the entire structure) from the trilayer to the single-layer sublattices and this effect will be enhanced by overall electron doping. Moreover, we find a leading d x 2 -y 2 -wave pairing state that is restricted to the single layer. Because the effective coupling between the single layers is very weak, due to the nonsuperconducting trilayer in-between, this suggests that the superconducting transition temperature T c in this structure should be much lower than in the bilayer structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Electronic structure of the honeycomb iridate Cu 2 ⁢IrO 3 at high pressure

Cu 2 IrO 3 has attracted recent interest due to its proximity to the Kitaev quantum spin liquid state and the complex structural response observed at high pressures. We use x-ray spectroscopy and scattering as well as electrical transport techniques to unveil the electronic structure of Cu 2 IrO 3 at ambient and high pressures. Despite featuring a Ir 4+ J eff = 1/2 state at ambient pressure, Ir L 3 -edge resonant inelastic x-ray scattering reveals broadened electronic excitations that point to the importance of Ir 5d-Cu 3d interaction. High pressure first drives an Ir-Ir dimer state with collapsed < L · S > and < L z >/< S z >, signaling the formation of 5d molecular orbitals. A novel Cu → Ir charge transfer is observed above 30 GPa at low temperatures, leading to an approximate Ir 3+ and Cu 1.5+ valence, with persistent insulating electrical transport seemingly driven by charge segregation of Cu 1+ /Cu 2+ ions into distinct sites. Concomitant x-ray spectroscopy and diffraction measurements through different thermodynamic paths demonstrate a strong electron-lattice coupling, with J eff = 1/2 and Ir 3+ /Cu 1.5+ electronic states occurring only in phases 1 and 5, respectively. Remarkably, the charge-transfer state can only be reached if Cu 2 IrO 3 is pressurized at low temperature, suggesting that phonons play an important role in the inhibiting this phase. Furthermore, these results point to the choice of thermodynamic path across interplanar collapse transition as a key parameter to access novel states in intercalated iridates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Modeling a High-Temperature Electrochemically Driven Water-Gas-Shift Process Using a Mixed-Conducting Membrane without External Electrical Power

This paper develops a model to predict and interpret the performance of an elevated-temperature, electrochemical, membrane-assisted, water-gas-shift process. The process uses separated feed streams of H 2 O and CO to produce separated streams of H 2 and CO 2 , without an external electrical power source. The dense ceramic membrane is mixed ionic-electronic-conducting (MIEC) gadolinium-doped ceria (GDC) and the porous composite electrodes are Ni-YSZ. At elevated temperature, GDC conducts both oxygen ions and small polarons. The present process uses chemical potential to drive the process. Electrochemical oxidation of CO proceeds within the composite anode and H 2 O reduction proceeds within the composite cathode. At high temperature (e.g., T > 700 °C), GDC has significant electronic leakage in the form of a reduced-cerium small polaron, which supports the charge-transfer reactions. In a typical electrolyzer or fuel cell, this leakage is significantly problematic. However, the present process depends on the leakage current to complete the electrochemical circuit. Model development and validation is based on measured material properties and reactor performance. Potential applications include using CO-rich blast-furnace off gases in steel processing, producing separated streams of H 2 and CO 2 .

Zhu, Huayang↗
DOE OSTI2025

Modeling Electrodeposition in 3D Porous Architectures for Solid-State Li-Metal Batteries

Li-metal storage in three-dimensional (3D) electrodes is considered a potential dendrite-mitigation strategy. The large surface area and high porosity of these electrodes result in reduced local Li-plating current densities. The porous topology provides a scaffold for Li-deposition and stripping, maintaining both mechanical integrity and Li accessibility. The goal of this study is to understand how characteristics, such as geometry and material properties, affect the current distribution and deposition pattern. To this end, we developed a computational method to track material growth driven by electrodeposition within a complex geometry. This method ensures that the finite-element discretization remains conforming to the moving boundary while preserving an adequate mesh quality, and thus maintains solution accuracy. Using this new computational tool, we analyze the conditions under which porous anode architectures effectively expand the surface area of the charge-transfer interface, and self-regulate current density and dendrite growth.

3D electrode architectures↗
DOE OSTI2026

From Powder to Power: Tailored Pre-Milling Strategy that Optimizes Microstructure for Efficient Hydrogen Evolution

The hydrogen evolution reaction (HER) plays a critical role in enabling large-scale electrolytic hydrogen production and advancing future technologies and fuel production. Among non-precious metals, NiMo-based catalysts are particularly attractive due to their capability to promote both water dissociation and hydrogen adsorption in alkaline media. However, conventional NiMo catalysts often suffer from incomplete alloying, particle aggregation, weak metal–support interactions, and surface oxidation, which significantly limit active site utilization, electronic conductivity, and long-term stability. Herein, we report a scalable, solid-state, two-step ball milling strategy for constructing an efficient NiMo/C catalyst for the HER. Pre-milling the metal precursors prior to carbon incorporation promotes efficient solid-state activation, leading to the formation of uniformly alloyed, ultrafine, and defect-rich Ni–Mo nanoparticles with robust metal–carbon interfacial anchoring. Benefiting from this integrated structural design, the optimized NiMo/C catalyst exhibits low overpotentials and Tafel slopes, reduced charge-transfer resistance, and excellent durability under alkaline conditions. Comprehensive structural and surface analysis reveal that the enhanced HER performance can be attributed to the synergistic interplay of homogeneous Ni–Mo alloying, uniform nanoparticle dispersion on a defect-rich carbon scaffold, enhanced accessibility of catalytically active sites, and optimized electronic coupling that stabilizes the catalyst surface. This work highlights the two-step solid-state ball milling strategy as a simple, robust, and scalable route for the preparation of effective and durable non-precious metal HER electrocatalysts, offering practical insights toward large-scale and inexpensive hydrogen production.

Yang, Xiaoxuan [Oak Ridge National Laboratory (ORN↗
DOE OSTI2024

Theories of homogeneous and electrochemical electron transfer in complex media and interfaces (Final Technical Report)

This project makes the next step in establishing practical theories of charge transfer in complex media. The development of formal models is supported by extensive atomistic simulations, quantum calculations of force-field parameters, and direct measurements of charge-transfer spectra. All theory development is supported by experiment, extensive numerical simulations, and through external collaborations.

14 SOLAR ENERGY↗
DOE OSTI2025

Novel polyoxometalate based Catalytic Materials for Proton Exchange Membrane fuel cells

This research project will focus on the design and fabrication of cost-effective catalytic materials and substrates suitable for polymer-electrolyte membrane-based fuel cells. Our emphasis centers on the utilization of carbon-based substrates, where covalently binding catalysts offer enhancements in catalytic efficiency, including improved reactant absorption and enhanced charge-transfer interactions

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

Bimetallic Coinage Metal Complexes of Tetradentate ortho Ter arylene Ligands

The synthesis, structural and photophysical properties of five bimetallic coinage metal complexes of three tetradentate charge-transfer (CT) ligands are presented. The ligand structures incorporate donor/acceptor moieties electronically decoupled by ortho connection to a bridging biphenylene group. The M M distances observed in the crystal structures of the bimetallic complexes are shorter than the sum of the Van der Waals radii of the metal ions, suggesting stabilizing interactions between the d10 metal centers. Additionally, short distances between the bridging biphenylene and metal atoms suggest arylene metal interactions. Bimetallic Cu, Ag, and Au complexes of the ligand incorporating a carbazole donor and pyridyl acceptor (N2R22-) show absorption and emission energies that trend with the ionization potential of each metal, indicating metal character in the excited state. These properties contrast with our previously reported mononuclear Zn complex of N2R22-The structural and photophysical properties of five bimetallic d10 coinage metal complexes were presented. The M M distances observed in the crystal structures of the bimetallic complexes are shorter than the sum of the metals’ Van der Waals radii, suggesting attractive interactions between the d10 metal centers. Additionally, short distances between the bridging biphenylene and metal atoms suggest arylene metal interactions. The absorption and emission spectra of the bimetallic complexes redshift based on the oxidation potential of the metal ion. This suggests involvement of metal based orbitals in the excited state transitions of the bimetallic complexes, which was corroborated by molecular modeling. High photoluminescent quantum yields were observed in solution and in rigid media (up to PL = 0.75), and the excited state lifetimes in solution were found to exceed several microseconds.

Shariaty, Darius Allen [University of Southern Cal↗
DOE OSTI2024

Unraveling Electronic and Vibrational Coherences Following a Charge Transfer Process in a Photosystem II Reaction Center

A reaction center is a unique biological system that performs the initial charge separation within a Photosystem II (PSII) multiunit enzyme, which eventually drives the catalytic water-splitting in plants and algae. The possible role of quantum coherences coinciding with the energy and charge transfer processes in PSII reaction center is one of the active areas of research. Here, we study these quantum coherences by using a numerically exact method on an excitonic dimer model, including linear vibronic coupling and employing optimal parameters from experimental two-dimensional coherent spectroscopic measurements. This enables us to precisely capture the excitonic interaction between pigments and the dissipation of the energy from electronic and charge-transfer (CT) states to the protein environment. We employ the time nonlocal (TNL) quantum master equation to calculate the population dynamics, which yields numerically reliable results. The calculated results show that, due to the strong dissipation, the lifetime of electronic coherence is too short to have direct participation in the charge transfer processes. However, there are long-lived vibrational coherences present in the system at frequencies close to the excitionic energy gap. These are strongly coupled with the electronic coherences, which makes the detection of the electronic coherences with conventional techniques very challenging. Additionally, we unravel the strong excitonic interaction of radical pair (PD1 and PD2) in the reaction center, which results in a long-lived electronic coherence of >100 fs, even at room temperature. Our work provide important physical insight to the charge separation process in PSII reaction center, which may be helpful for better understanding of photophysical processes in other natural and artificial light-harvesting systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2026

X-ray characterization of fully-depleted p-channel Skipper-CCDs for the DarkNESS mission

The Dark matter Nanosatellite Equipped with Skipper Sensors (DarkNESS) mission is a 6U CubeSat designed to search for X-ray lines from decaying dark matter using Skipper-CCDs. Thick, fully-depleted p-channel Skipper-CCDs provide low readout noise and high quantum efficiency for 1-10 keV X-rays, but their X-ray performance has not yet been demonstrated in the space environment. DarkNESS will operate in low-Earth orbit, where trapped protons induce displacement damage in the sensor that increases charge-transfer inefficiency and degrades the X-ray energy resolution. This work measures the X-ray line response of Skipper-CCDs before and after proton irradiation and quantifies the associated degradation. A sensor was exposed to 217 MeV protons at a fluence of 8.4 x 10^10 protons cm^-2, corresponding to a displacement-damage dose more than an order of magnitude above the three-year expectation for representative mid-inclination and Sun-synchronous low-Earth orbits. A 55Fe source was used to compare the energy resolution of the beam-exposed quadrant to adjacent unexposed quadrants and a non-irradiated reference sensor. These measurements provide a quantitative assessment of radiation-induced spectral degradation in Skipper-CCDs and enable an estimate of the end-of-life X-ray energy resolution expected for DarkNESS operation in low-Earth orbit.

Alpine, Phoenix [Illinois U., Urbana] (ORCID:00090↗
DOE OSTI2026

Structural and Electrocatalytic Studies of Pulsed Laser Deposited Epitaxial RuO 2 Thin Films

Two sets of high-quality epitaxial ruthenium oxide (RuO 2 ) thin films with different thicknesses were synthesized in situ on cost-competitive sapphire substrates by using a pulsed laser deposition technique. The first set of films, with a thickness of 40 nm and a sheet resistance of 15.7 Ω/□, was prepared using 2100 laser pulses, while the second set of films, with a thickness of 87 nm and a sheet resistance of 6.7 Ω/□, was prepared using 4800 laser pulses. All other deposition parameters were kept the same. The post-deposition structural and morphological measurements showed that both sets of films grew at the same growth rate, had the same crystallinity, similar grain boundary density, and slightly different surface roughness. The thicker RuO 2 films achieved an overpotential of 280 mV for the oxygen evolution reaction at a current density of 100 μA/cm 2 , comparable to or exceeding the performance of films grown on more expensive substrates. Comparatively, the thinner RuO 2 films, which have a significantly higher charge transfer resistance (250 Ω versus 100 Ω for thick films), display a higher overpotential of 320 mV. These results indicate that the lower electrical resistance of thicker films promotes charge transfer through the film body, leading to superior electrocatalytic properties.

charge-transfer↗