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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Design Trade-Offs in Composite Fuel Cell Membranes: Effects of Reinforcement and Chemical Additives

Perfluorosulfonic acid (PFSA) membranes are critical components in proton exchange membrane fuel cells, where performance depends on balancing ionic conductivity, mechanical durability, and chemical stability. This study characterizes a composite membrane (NC700) featuring PFSA-impregnated expanded polytetrafluoroethylene (ePTFE) reinforcement and cerium-based radical scavengers, benchmarked against unreinforced NR211. Complementary techniques, including electron microscopy, X-ray scattering, infrared spectroscopy, thermogravimetric analysis, and dynamic mechanical analysis, identify the structural and compositional strategies employed in NC700. Water sorption isotherms reveal lower water uptake for NC700 across all conditions, attributed to reinforcement and cerium incorporation. Reinforcement reduces in-plane swelling from 11% to 2.1% at 90% RH, confirming strong swelling anisotropy, while maintaining mechanical properties at elevated temperatures. While the ionic conductivity of NC700 is approximately 10% lower than that of NR211, the reduced thickness yields a 40% decrease in calculated area-specific resistance, suggesting the composite architecture can favorably shift the conductivity-stability trade-off. The composite structure also reduces gas permeability, indicating potential for improved separator function alongside favorable transport properties. Systematic deconvolution of reinforcement and additive contributions shows that conductivity losses from cerium incorporation are largely offset by gains from the lower equivalent-weight polymer, providing quantitative relationships that may guide composite membrane design for fuel cells and other electrochemical applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Mathematical modeling of novel porous transport layer architectures for proton exchange membrane electrolysis cells

Thin foil based porous transport layers (PTLs) that contain highly structured pore arrays have shown promise as anode PTLs in proton exchange membrane electrolysis cells. These novel PTLs, fabricated with advanced manufacturing techniques, produce thin, tunable, multifunctional layers with reduced flow and interfacial resistances and high thermal and electric conductivities. To further optimize their design, it is important to understand their fundamental impact on the transport of protons, electrons, and liquid/vapor mixtures in the electrode. In this work, we develop a two-dimensional multiphysics model to simulate the coupled electrochemistry and multiphase transport in an electrolysis cell operated with the novel PTL architecture. The results show that larger pores improve access of water to the anode catalyst layer, which is beneficial for both the oxygen evolution reaction and membrane hydration. Larger pore sizes also improve oxygen gas transport from the catalyst layer, because generated oxygen gas is forced to travel in-plane through the anode catalyst layer until it reaches a pore opening that is connected to a channel. The discussed results confirm that the proposed thin foil based PTLs are fundamentally different from conventional PTLs, such as felts or layered meshes. The model developed in this work also provides generalizable insight into fundamental PEMEC phenomena, such as the competition between liquid and gas phase transport, membrane hydration and water management, and nonuniform electrochemical reactions, which are processes relevant to all PEMEC designs.

25 ENERGY STORAGE↗
DOE OSTI2024

Photoelectrochemical Proton-Coupled Electron Transfer of TiO 2 Thin Films on Silicon

TiO 2 thin films are often used as protective layers on semiconductors for applications in photovoltaics, molecule–semiconductor hybrid photoelectrodes, and more. Experiments reported here show that TiO 2 thin films on silicon are electrochemically and photoelectrochemically reduced in buffered acetonitrile at potentials relevant to photoelectrocatalysis of CO 2 reduction, N 2 reduction, and H 2 evolution. On both n-type Si and irradiated p-type Si, TiO 2 reduction is proton-coupled with a 1e – :1H + stoichiometry, as demonstrated by the Nernstian dependence of the Ti 4+/3+ E 1/2 on the buffer pK a . Experiments were conducted with and without illumination, and a photovoltage of ∼0.6 V was observed across 20 orders of magnitude in proton activity. The 4 nm films are almost stoichiometrically reduced under mild conditions. The reduced films catalytically transfer protons and electrons to hydrogen atom acceptors, based on cyclic voltammogram, bulk electrolysis, and other mechanistic evidence. TiO 2 /Si thus has the potential to photoelectrochemically generate high-energy H atom carriers. Characterization of the TiO 2 films after reduction reveals restructuring with the formation of islands, rendering TiO 2 films as a potentially poor choice as protecting films or catalyst supports under reducing and protic conditions. Altogether, this work demonstrates that atomic layer deposition TiO 2 films on silicon photoelectrodes undergo both chemical and morphological changes upon application of potentials only modestly negative of RHE in these media. While the results should serve as a cautionary tale for researchers aiming to immobilize molecular monolayers on “protective” metal oxides, the robust proton-coupled electron transfer reactivity of the films introduces opportunities for the photoelectrochemical generation of reactive charge-carrying mediators.

Electrodes↗
DOE OSTI2025

2025 ASMS Investigation of the Collision-Induced Dissociation Mechanism of Protonated TODGA with IRIS

Title (20 words): Investigation of the Collision-Induced Dissociation Mechanism of Protonated TODGA with IRIS Introduction (120 words): One of the challenges facing wide-spread adoption of nuclear power is the development of efficient separation processes for used nuclear fuel. The molecules in separation processes are subjected to an extreme environment due to the high radiation fields from the used fuel and highly acidic media used for fuel dissolution, which results in significant molecular degradation, leading to reduced process efficiency. These degradation products must be identified and studied so mitigation strategies can be developed to maintain process efficiency. However, complex systems can have many degradation products, complicating identification. Untargeted analysis tools could be used to understand radiation chemistry in complex systems. However, this would necessitate improved understanding of the gas-phase fragmentation mechanisms of fuel cycle molecules like tetraoctyldiglycolamide (TODGA). Methods (120 words): The gas-phase fragmentation of protonated TODGA was investigated using collision-induced dissociation (CID), resonance ejection, and infrared ion spectroscopy (IRIS). CID and resonance ejection experiments were conducted using a Bruker Daltonics (Bremen, Gemany) SolariX XR fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. IRIS spectra of protonated TODGA and its two CID fragmentation products were measured using a modified Bruker amaZon Speed ETD 3D quadrupole ion trap mass spectrometer coupled to the Free Electron Lasers for Infrared eXperiments (FELIX) free electron laser. Measured spectra were compared with density functional theory (DFT) calculations using the Gaussian 16, Revision C.02 software package with the ?B97X-D functional and def2-TZVPP basis sets. Candidate structures were generated using the CREST 3.0 conformational sampling software tool. Preliminary Data (300 words): Collision-induced dissociation of protonated TODGA ([C36H73N2O3]+, m/z=581.562) results two fragment ions, one at m/z=340.285 assigned as [C20H38NO3]+ and the other at m/z=312.290, assigned as [C19H38NO2]+. Based on the assigned formula and the structure of protonated TODGA, the fragment at m/z=340.285 is likely formed from elimination of neutral dioctylamine. Comparison of the IRIS spectrum of m/z=340.285 with DFT predictions suggests it contains a ring structure, and is assigned as N-octyl-N-(6-oxo-1,4-dioxan-2-ylidene)octan-1-aminium. Based on this structure and the structure of protonated TODGA, we hypothesize this fragment formed from elimination of neutral dioctylamine followed by a ring closure mechanism. Comparison of the IRIS spectrum of the fragment at m/z=312.290 with DFT predictions also indicated the presence of a ring structure, assigned as N-(1,3-dioxolan-4-ylidene)-N-octyloctan-1-aminium. This product could be formed from elimination of carbon monoxide from the ring of m/z=340.285 as a sequential fragmentation or formed directly from protonated TODGA via elimination of neutral N,N-dioctylformamide followed by a ring closure. Resonance ejection experiments where m/z=340 was continuously ejected from the IRC cell showed no decrease in intensity of m/z=312.290 across several collision energies, suggesting that the later, direct formation mechanism, dominates. The location of the ionizing proton in protonated TODGA is important for modeling the fragmentation mechanisms. DFT calculations suggested that the position of bands involving the coupled vibrations of the amide C—N and C=O bonds in TODGA are the most sensitive to proton location. Evaluation of the IRIS spectrum of protonated TODGA suggests that the ionizing proton is located between the two amid oxygens. This protonation location was calculated to lie approximately 30 kJ/mol lower in energy than the next lowest energy location, with the proton located solely on one of the amide oxygens. Novel aspect (20 words): Infrared ion spectroscopy combined with resonance ejection experiments and density functional theory to probe the collision-induced dissociation mechanism of tetraoctyldiglycolamide.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2026

𝐽/𝜓-meson–nucleon scattering length from threshold photoproduction on light nuclei

The quality of recent Short-Range Correlations/Color-Transparency (SRC/CT) Collaboration 𝐽/𝜓 photoproduction data off a 4 He target from Hall D at Jefferson Laboratory, combined with the feasibility of measuring the reaction close to the free-nucleon energy threshold, opens the door to using incoherent 𝐽/𝜓 photoproduction to explore a variety of interesting physics aspects. An example is the estimation of the 𝐽/𝜓 𝑝 scattering length |𝛼 𝐽/𝜓 𝑝 | on the bound proton, obtained using the vector meson dominance model. The new experiment E12–25–002, conducted by the SRC/CT Collaboration, was recently approved in Hall D with the GlueX spectrometer, which will significantly enhance the number of reconstructed 𝐽/𝜓 mesons. Using a plane-wave theoretical model to generate quasidata, we estimated that the experiment could achieve a result of |𝛼 𝐽/𝜓 𝑝 | = 3.08 ± 0.45 mfm. This value can be compared to an extraction based on the free proton data from the GlueX Collaboration, |𝛼 𝐽/𝜓 𝑝 | = 3.08 ± 0.55 mfm. A comparison between the two would provide an opportunity to evaluate the effects of medium modification in light nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Thermodynamic Modeling of Point Defects in Triple Conducting Perovskite Ba 0.95 La 0.05 FeO 3- $_δ$ with Incorporation of the Hydride Defect Formation Reaction for Solid Oxide Cells

Distinct from the proton defect, the hydride defect species may be present in certain perovskite materials in reducing environments such as in fuel electrodes of solid oxide cells (SOCs) or on the reducing side of ceramic membranes. A generalized defect thermodynamic model was developed for the triple-conducting perovskites (La,Ba)Fe 1-x M x O 3-δ (M = Y and Zr) to allow inclusion of the hydride defect formation reaction in addition to the other three main defect reactions, namely, the oxygen vacancy formation, hydration, and charge disproportionation reactions. This comprehensive defect model also allows the incorporation of polynomial functional forms of oxygen nonstoichiometry δ to describe the defect reaction energies and entropies and to enable refinements of the defect reaction equilibrium constants in the defect thermodynamic analysis. As a first step, the developed model is applied to the Ba 0.95 La 0.05 FeO 3-δ material as an illustrative system to obtain its Brouwer diagrams with both the proton and hydride defects in relevant SOC conditions, particularly for more reducing environments. In conclusion, the results provide direct guidance on the influence of electronic and ionic defect concentrations upon thermodynamic properties and ultimately on the performance of Ba 0.95 La 0.05 FeO 3-δ and potentially other (La,Ba)Fe 1-x M x O 3-δ perovskite materials involved in SOC applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Perovskite neural trees

Trees are used by animals, humans and machines to classify information and make decisions. Natural tree structures displayed by synapses of the brain involves potentiation and depression capable of branching and is essential for survival and learning. Demonstration of such features in synthetic matter is challenging due to the need to host a complex energy landscape capable of learning, memory and electrical interrogation. We report experimental realization of tree-like conductance states at room temperature in strongly correlated perovskite nickelates by modulating proton distribution under high speed electric pulses. This demonstration represents physical realization of ultrametric trees, a concept from number theory applied to the study of spin glasses in physics that inspired early neural network theory dating almost forty years ago. We apply the tree-like memory features in spiking neural networks to demonstrate high fidelity object recognition, and in future can open new directions for neuromorphic computing and artificial intelligence.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Giant isotope effect on phonon dispersion and thermal conductivity in methylammonium lead iodide

Lead halide perovskites are strong candidates for high-performance low-cost photovoltaics, light emission, and detection applications. A hot-phonon bottleneck effect significantly extends the cooling time of hot charge carriers, which thermalize through carrier–optic phonon scattering, followed by optic phonon decay to acoustic phonons and finally thermal conduction. To understand these processes, we adjust the lattice dynamics independently of electronics by changing isotopes. We show that doubling the mass of hydrogen in methylammonium lead iodide by replacing protons with deuterons causes a large 20 to 50% softening of the longitudinal acoustic phonons near zone boundaries, reduces thermal conductivity by ~50%, and slows carrier relaxation kinetics. Phonon softening is attributed to anticrossing with the slowed libration modes of the deuterated molecules and the reduced thermal conductivity to lowered phonon velocities. Our results reveal how tuning the organic molecule dynamics enables control of phonons important to thermal conductivity and the hot-phonon bottleneck.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electrochemical flow-cell for hydrogen production and nicotinamide dependent target reduction, and related methods and systems

Methods and systems for hydrogen production or production of a reduced target molecule are described, wherein a nicotinamide co-factor dependent membrane hydrogenase or a nicotinamide co-factor dependent membrane enzyme presented on a nanolipoprotein adsorbed onto an electrically conductive supporting structure, which can preferably be chemically inert, is contacted with protons or a target molecule to be reduced and nicotinamide cofactors in presence of an electric current and one or more electrically driven redox mediators. Methods and systems for production of hydrogen or a reduced target molecule are also described wherein a membrane-bound hydrogenase enzyme or enzyme capable or reducing a target molecule is contacted with protons or the target molecule, a nicotinamide co-factor and a nicotinamide co-factor dependent membrane hydrogenase presented on a nanolipoprotein particle for a time and under condition to allow hydrogen production or production of a reduced target molecule in presence of an electrical current and of an electrically driven redox mediator.

Hoeprich, Jr., Paul D.↗
DOE OSTI2022

Effects of EMIC Wave-Driven Proton Precipitation on the Ionosphere

In this report we investigate the proton precipitation caused by electromagnetic ion cyclotron (EMIC) waves and its impact on the ionosphere with the self-consistent ring current-atmosphere interactions model (RAM-SCBE) coupled with an ionospheric particle transport model Global Airglow (GLOW). The EMIC wave diffusion process causes significant precipitation of tens of keV protons, particularly in the afternoon to midnight sector. These precipitating energetic protons further impact the ionosphere-thermosphere and contribute to the ionization in the E/F regions. The integrated auroral conductance is significantly enhanced in the dusk-to-midnight sector. Although the EMIC waves do not directly interact with the ring current electrons, after the EMIC wave scattering included in the model, remarkable changes are found in the global distribution of precipitating electron flux. This means that the addition of proton precipitation driven by EMIC waves results in feedback effects on the ring current electron dynamics through the circulation system. Validation is also conducted by comparing the simulated precipitation flux and ionospheric electron density with observations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A TOPAS model for lens-based proton radiography

Abstract Objective. Proton Radiography can be used in conjunction with proton therapy for patient positioning, real-time estimates of stopping power, and adaptive therapy in regions with motion. The modeling capability shown here can be used to evaluate lens-based radiography as an instantaneous proton-based radiographic technique. The utilization of user-friendly Monte Carlo program TOPAS enables collaborators and other users to easily conduct medical- and therapy- based simulations of the Los Alamos Neutron Science Center (LANSCE). The resulting transport model is an open-source Monte Carlo package for simulations of proton and heavy ion therapy treatments and concurrent particle imaging. Approach. The four-quadrupole, magnetic lens system of the 800-MeV proton beamline at LANSCE is modeled in TOPAS. Several imaging and contrast objects were modelled to assess transmission at energies from 230–930 MeV and different levels of particle collimation. At different proton energies, the strength of the magnetic field was scaled according to βγ, the inverse product of particle relativistic velocity and particle momentum. Main results. Materials with high atomic number, Z, (gold, gallium, bone-equivalent) generated more contrast than materials with low-Z (water, lung-equivalent, adipose-equivalent). A 5-mrad collimator was beneficial for tissue-to-contrast agent contrast, while a 10-mrad collimator was best to distinguish between different high-Z materials. Assessment with a step-wedge phantom showed water-equivalent path length did not scale directly according to predicted values but could be mapped more accurately with calibration. Poor image quality was observed at low energies (230 MeV), but improved as proton energy increased, with sub-mm resolution at 630 MeV. Significance. Proton radiography becomes viable for shallow bone structures at 330 MeV, and for deeper structures at 630 MeV. Visibility improves with use of high-Z contrast agents. This modality may be particularly viable at carbon therapy centers with accelerators capable of delivering high energy protons and could be performed with carbon therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Durable, High-Performance Unitized Reversible Fuel Cells Based on Proton Conductors

The main objective of this project was to develop robust, highly efficient, and economically viable H + -conducting membrane-based, unitized reversible fuel cell (H-URFC) technology for large-scale co-located energy storage and power generation. Another objective of this project is to gain a profound understanding of the degradation mechanisms of key stack materials and interfaces using various in situ, ex situ, and operando measurements guided by theoretical analysis. Nanostructured components will be integrated into cell design and the interfaces between electrodes and electrolyte will be modified with active bi-functional catalysts and protective coatings in order to achieve >70% roundtrip efficiency at 1 A/cm2 in both the fuel cell and the electrolysis modes. The end goal of the project is to advance the technology to the point that a university-industry collaboration can be established to scale up the technology for early adoption, and eventually enabling a pathway to large-scale energy storage that utilizes chemical storage and conversion for electrical grid balancing.

08 HYDROGEN↗
DOE OSTI2026

Hydrogen defects in LaBi 2 O 4 X (X = Cl, Br, and I) Sillén oxyhalide phases and their impacts on ionic transport

Sillén oxyhalides have recently emerged as promising materials for both photocatalytic and ionic transport applications, yet the role of likely-ubiquitous hydrogen-related defects in these layered compounds remains largely unexplored. Here, we employ first-principles defect calculations to investigate incorporation energetics for hydrogen- and oxygen-related defects, as well as their migration barriers in LaBi 2 O 4 X (X = Cl, Br, I) phases. We find that hydrogen interstitials, particularly protonic species (H i + ), are readily accommodated within the open Bi–O layers. Protons compete with oxygen vacancy donors (V O 2+ ) and charge-compensate with oxygen interstitial acceptors (O i 2− ). By linking hydrogen defect formation to water- and oxygen-related redox equilibria, we reveal that V O 2+ facilitates H i + incorporation, while O i 2− promotes interstitial hydroxide formation, establishing a direct connection between proton and oxide-ion transport. Calculated migration barriers indicate that ionic diffusion is confined to Bi–O layers with low barriers of 0.20–0.25 eV for H i + and 0.14–0.25 eV for V O 2+ , suggesting that the materials contain intrinsic pathways for mixed ionic conduction. These results provide a microscopic picture of hydrogen behavior in Sillén oxyhalides and point to design strategies for integrating protonic and oxide-ion transport in layered oxyhalide electrolytes. Band-edge alignment analysis shows that LaBi 2 O 4 I provides the optimal combination of hydrogen solubility, oxygen defect stability, and mixed ionic conductivity, highlighting its potential for low-temperature electrochemical and energy-conversion applications. Overall, this work establishes the defect-driven origin of hydrogen transport in Sillén oxyhalides and expands their applicability beyond photocatalysis to mixed ionic conduction and hydrogen electrochemistry.

Energy - Conversion↗
DOE OSTI2021

Search for dark matter in association with an energetic photon in pp collisions at $ \sqrt{s} $ = 13 TeV with the ATLAS detector

A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at s√ = 13 TeV. The data, collected during 2015–2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb -1 . No deviations from the predictions of the Standard Model are observed and 95% confidence-level upper limits between 2.45 fb and 0.5 fb are set on the visible cross section for contributions from physics beyond the Standard Model, in different ranges of the missing transverse momentum. The results are interpreted as 95% confidence-level limits in models where weakly interacting dark-matter candidates are pair-produced via an s-channel axial-vector or vector mediator. Dark-matter candidates with masses up to 415 (580) GeV are excluded for axial-vector (vector) mediators, while the maximum excluded mass of the mediator is 1460 (1470) GeV. In addition, the results are expressed in terms of 95% confidence-level limits on the parameters of a model with an axion-like particle produced in association with a photon, and are used to constrain the coupling g a Z γ of an axion-like particle to the electroweak gauge bosons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Gating choreography and mechanism of the human proton-activated chloride channel $\mathrm{ASOR}$

The proton-activated chloride channel ASOR (TMEM206/PAC) permeates anions across cellular membranes in response to acidification, thereby enhancing acid-induced cell death and regulating endocytosis. The molecular mechanisms of pH-dependent control are not understood, in part because structural information for an activated conformation of ASOR is lacking. Here, we reconstitute function from purified protein and present a 3.1-Å-resolution cryo–electron microscopy structure of human ASOR at acidic pH in an activated conformation. The work contextualizes a previous acidic pH structure as a desensitized conformation. Combined with electrophysiological studies and high-resolution structures of resting and desensitized states, the work reveals mechanisms of proton sensing and ion pore gating. Clusters of extracellular acidic residues function as pH sensors and coalesce when protonated. Ensuing conformational changes induce metamorphosis of transmembrane helices to fashion an ion conduction pathway unique to the activated conformation. The studies identify a new paradigm of channel gating in this ubiquitous ion channel.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Structural characterization of ligand binding and pH-specific enzymatic activity of mouse Acidic Mammalian Chitinase

Chitin is an abundant biopolymer and pathogen-associated molecular pattern that stimulates a host innate immune response. Mammals express chitin-binding and chitin-degrading proteins to remove chitin from the body. One of these proteins, Acidic Mammalian Chitinase (AMCase), is an enzyme known for its ability to function under acidic conditions in the stomach but is also active in tissues with more neutral pHs, such as the lung. Here, we used a combination of biochemical, structural, and computational modeling approaches to examine how the mouse homolog (mAMCase) can act in both acidic and neutral environments. We measured kinetic properties of mAMCase activity across a broad pH range, quantifying its unusual dual activity optima at pH 2 and 7. We also solved high-resolution crystal structures of mAMCase in complex with oligomeric GlcNAcn, the building block of chitin, where we identified extensive conformational ligand heterogeneity. Leveraging these data, we conducted molecular dynamics simulations that suggest how a key catalytic residue could be protonated via distinct mechanisms in each of the two environmental pH ranges. These results integrate structural, biochemical, and computational approaches to deliver a more complete understanding of the catalytic mechanism governing mAMCase activity at different pH. Engineering proteins with tunable pH optima may provide new opportunities to develop improved enzyme variants, including AMCase, for therapeutic purposes in chitin degradation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Characterization of laser-accelerated proton beams from a 0.5 kJ sub-picosecond laser for radiography applications

Laser-accelerated ion beams show promise for many applications, including high-resolution flash imaging of static or dynamic objects in next-generation radiography to probe materials and plasmas in extreme environments and inertial confinement fusion. To scale up ion beam production for radiography applications, we conducted experiments using sub-picosecond lasers up to 0.5 kJ at the OMEGA-EP facility to characterize proton beams from solid targets, primarily CH/CD sub-micron thin films from which ion beams were also used for static and dynamic radiography for the first time. For standalone sub-micron thin CH films, the highest detected proton energy is in the range of 72–97 MeV. Proton beams with highest energy near or above 60 MeV at full laser energy and similar beam profiles are also measured from low-density CD foams and flat CH foil target of micrometer-scale thickness. The ~ 700–800 nm CH/CD foils achieve the highest ion yield among the targets tested. For sub-micron thin films, the laser prepulse can expand the target and lead to complex interactions, which is simulated using coupled hydrodynamic and two-step kinetic models. Simulations suggest the presence of a micrometer-scale preplasma plateau with near-critical density and further indicate that target normal sheath acceleration, electron heating from Relativistic transparency in the preplasma plateau, and background proton reflection from carbon ion front at the rear side contribute to the resulting proton spectrum from these sub-micron thin targets at various stages. These proton beams show strong potential for radiography and for production of secondary sources.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Modeling High Current Pulsed Discharge in AA Battery Cathodes: The Effect of Localized Charging during Rest

During high current operation, substantial heterogeneity develops within battery cathodes, particularly when their thickness is large. Heterogeneity relaxation during subsequent rest is important for understanding battery performance under pulsed conditions. Localized charge balancing phenomena within batteries at zero net current are not well understood and merit investigation. In this work, the heterogeneity within cathodes of commercial alkaline Zn–MnO 2 batteries is measured during discharge and monitored during rest using energy dispersive X-ray diffraction (EDXRD). Significant gradients in protonation form during discharge and partially relax under rest. It is demonstrated that the proton gradient relaxation is through local redox activity at zero net current, where local (de)protonation works to redistribute charge across the cathode thickness. To support this redox-based relaxation, a fundamental kinetic study on prismatic MnO 2 cathodes is conducted to determine an appropriate model to describe both discharge and charge kinetics of MnO 2 . These kinetics are incorporated into a computational model to simulate the proton gradient formation and partial relaxation under identical discharge conditions as the operando EDXRD experiments. Model and experimental data are found to be in excellent agreement, correctly predicting localized charge balancing at rest.

Batteries↗