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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Quantification of [MTBD][beti] loading and its effects on Pt/HSC electrode performance in hydrogen fuel cells

High surface area carbon-supported platinum catalysts (Pt/HSC) are widely used in polymer electrolyte membrane fuel cells but often suffer from limited proton and oxygen transport within porous domains. To address these challenges, we integrate the ionic liquid [MTBD][beti] into Pt/HSC catalyst layers using two deposition methods-one-pot and sequential deposition-to tune IL distribution within micropores and mesopores. A combination of ex situ and in operando techniques were employed to elucidate electrode structure-performance relationships across a range of IL loadings. Sequential deposition achieved more efficient pore filling and higher IL retention at lower IL:C ratios, enabling enhanced proton conductivity and protection of active sites. Compared to the IL-free Pt/HSC, IL-modified electrodes demonstrated up to 28% improvement in mass activity and enhanced high-current-density performance under low relative humidity, while maintaining comparable performance under humidified conditions. Electrochemical impedance spectroscopy and CO displacement experiments reveal that improvements are linked to reduced ionic resistance and lower sulfonate adsorption on Pt sites, rather than changes in electrochemical surface area. However, excessive IL loading leads to mass transport losses. These results highlight the importance of selective pore filling and efficient IL distribution in achieving kinetic gains without compromising ionic and gas transport.

08 HYDROGEN↗
DOE OSTI2023

Development of Metal-Free Photocatalysts

Solar fuels show great promise as clean, sustainable energy sources; however, established technologies are still plagued by high price, toxicity concerns, or low efficiencies. There is a critical need for inexpensive, benign materials that can effectively harness the sun’s energy. The overarching objective of this project is to evaluate the compatibility of novel material combinations for use as metal-free, heterojunction photocatalysts. Our central hypothesis is that by tuning the electronic structure of individual components in hybrid composites, via selective chemical modifications and physical stimuli to the interface, we can improve the photocatalytic properties of the overall assembly. We will determine factors that affect energy band gaps and band edge positions in isolated photocatalyst systems as well as explore routes to modulate heterojunction band alignments in composite assemblies. Our results will predict accessible pathways for charge carriers in new composite photocatalysts, facilitating access to more of the solar spectrum via inexpensive, environmentally-friendly material combinations.

14 SOLAR ENERGY↗
DOE OSTI2025

National User Resource for Biological Accelerator Mass Spectrometry (Final Report)

The National User Resource for Biological Accelerator Mass Spectrometry (User Resource) will provide isotopic analysis (primarily radiocarbon or 14C) by accelerator mass spectrometry (AMS) for NIH- funded researchers across the United States and will be the only User Resource of its type in the United States. The User Resource will provide measurement capability and expertise to a research community that requires highly sensitive, quantitative isotope analyses. Since commissioning a new accelerator mass spectrometer in June 2014, we have measured over 4000 samples a year for collaborators and service users. The User Resource will enable us to continue to meet these research needs, as well as provide for new users whose research programs would benefit from AMS as a measurement tool. The User Resource’s forte will be ultra-high sensitivity quantitation of radiocarbon and selected other radioisotopes for research studies where isotopes are required. Radioisotope labeling studies have been and will continue to be an important tool for addressing many complex biomedical science problems. AMS is a specialized and unique type of mass spectrometry that provides absolute quantitation of radiocarbon and other relevant radioisotopes with extreme sensitivity, having limits of detection in real samples on the order of a few attomol/mg of sample at measurement precisions of ~3%. It is the only instrumental method capable of quantifying radioisotope-labeled agents routinely in real-world samples with such precision and sensitivity. The sensitivity of AMS allows for the quantification of radiolabeled metabolites in extremely complex matrices of cells and organisms at very low concentrations and in small samples. AMS allows studies to be conducted without perturbing metabolism leading to more relevant quantification of metabolic rates and pathways. In addition, it enables quantification of pharmacokinetic and metabolic properties of toxicants at environmentally relevant concentrations in model systems as well as the ability to quantify pharmacokinetics and other molecular endpoints directly in humans. Such quantitative assessments can 1) improve risk assessment for toxicants, 2) address safety and efficacy considerations for therapeutic entities, 3) deepen understanding of xenobiotic and intermediary metabolism, 4) help understand the interactions between critical molecular pathways, and 5) improve efforts to model and predict various metabolic and biological states. These capabilities have been applied in a number of areas including research in carcinogenesis, toxicology, nutrition, pharmacology/drug development and basic biological science. As a NIGMS National Resource the National User Resource for Biological Accelerator Mass Spectrometry will help NIH funded scientists achieve a deeper understanding of the etiology of human health concerns by (1) enabling the quantification of pharmacokinetics and other molecular endpoints directly in humans; (2) offering the ability to conduct quantitative studies using biologics such as proteins or lipids, and thereby reducing the amount of radioisotope usage in biomedical labs; and (3) enabling more relevant studies of metabolic pathways in health and disease through the use of much lower, more biologically-relevant, concentrations of metabolic substrates in cells and intact organisms. Such studies support NIGMS’s basic biomedical research areas that contribute to the understanding of fundamental cellular and physiological principles and enable research supported by the Biophysics, Biomedical Technology, and Computational Biosciences (BBCB); Genetics and Molecular, Cellular, and Developmental Biology (GMCDB); Pharmacology, Physiology, Biological Chemistry (PPBC) and Training, Workforce Development, and Diversity (TWD) Divisions. Over the next five years, our goals are to: 1. Improve the efficiency of operation for AMS measurements through installation of new interfaces to our AMS systems, technical modifications to improve gas accepting ion source efficiency and upgrading our data analysis software for improved ease of use and data reporting. 2. Increase the accessibility and visibility of ultra-sensitive 14C measurements for the biomedical research community by training of new investigators and expanding our national user base. 3. Provide high throughput, ultra-sensitive 14C analysis for the NIGMS and NIH user community.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Further Development of the Tamped Richtmyer-Meshkov Instability Method and Application to Molybdenum Dynamic Strength Calibration and Tabulation

The high pressure and high strain rate dynamic strength of Mo is experimentally and computationally investigated in the 3–20 GPa stress, 50–600 C temperature, and 10 5 –10 6 /s strain rate regimes using a modified tamped Richtmyer-Meshkov instability (RMI) method. Modifications to the tamped RMI method include a method to determine loading states during strain, a new strength calibration function based on interface shape, and a robust uncertainty quantification method. These modifications improve fidelity of the tamped RMI method, allowing evaluation of the compensating effects of pressure hardening, strain rate hardening, strain hardening, and thermal softening. The new calibration function based on interface shape is not limited to sinusoidal corrugations and could be applied to additional interface shapes. Plate impact experiments are performed at Argonne National Laboratory’s Advanced Photon Source’s Dynamic Compression Sector operated by Washington State University (DCS), driving a planar shock front through a corrugated Mo-D 2 O or Mo-C 8 F 18 interface, forcing the corrugation to significantly deform. The extent of interfacial deformation, RMI growth, is experimentally observed using X-ray phase contrast imaging at the DCS. RMI jet lengths and jet shapes are extracted from the experimental radiographs, then used to calibrate numerical simulations performed with the Sandia National Laboratories (SNL) hydrocode CTH. Mo yield strength, Y, as a function of shock pressure, P, strain rate, $\dot{\varepsilon }$, accumulated strain, ϵ, relative volumetric compression, RD , and temperature, T , is determined for each impact experiment and presented. The calibrated Mo yield strength values range 1.2–1.8 GPa, with strength generally decreasing as the impact stress increases. This trend is likely caused by thermal softening or strain localization. The tabular yield strength versus loading condition data presented in this paper can be used to fit complex strength models.

Voorhees, T. J. [Sandia National Lab. (SNL-CA), Li↗
DOE OSTI2021

Oxygen vacancy induced electronic structure modification of KTaO 3

The observation of a metallic interface between band insulators LaAlO 3 and SrTiO 3 has led to massive efforts to understand the origin of the phenomenon as well as to search for other systems hosting such two-dimensional electron gases (2-DEGs). However, the understanding of the origin of the 2-DEG is very often hindered as several possible mechanisms such as polar catastrophe, cationic intermixing, and oxygen vacancy (OV) can be operative simultaneously. The presence of a heavy element makes the KTaO 3 (KTO) based 2-DEG a potential platform to investigate spin-orbit coupling driven novel electronic and magnetic phenomena. In this work, we investigate the sole effect of OV in KTO, which makes KTO metallic. O K-edge x-ray absorption spectroscopy measurements find that OV dopes electrons in Ta t * 2g antibonding states. Photoluminescence measurements reveal the existence of a highly localized deep midgap state in oxygen-deficient KTO. Our detailed ab initio calculations demonstrate that such deep midgap state arises due to the linear clustering of OVs around Ta. Finally, our present work emphasizes that we must pay attention to the possible presence of OVs in interpreting emergent behavior of KTO-based heterostructures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Performance improvement of proton exchange membrane water electrolysis by surface modification of porous transport layers

Proton exchange membrane water electrolysis (PEMWE) is a promising option for hydrogen production from a variety of energy sources. Cost-effective production of hydrogen with PEMWE requires reduction of costly precious metals as well as optimization of the components and interfaces in the cell. The interface between the platinum-coated titanium porous transport layer (PTL) and catalyst layer (CL) significantly impacts the performance of the electrolyzer cell. Here, we report on two PTL modification methods, mechanical abrasion and chemical etching, which we find improve PEMWE performance by lowering the resistance of the PTL/CL interface. The PTL surface modifications enabled performance improvements up to 77 mV at 4 A cm −2 and reduction of the high frequency resistance, demonstrating that the resistance of the PTL/CL interface is a significant factor in the cell performance. The PTL surface roughness was varied using abrasive materials ranging from 0.1 to 140 μm in grain sizes and chemical etching was found to also increase the surface roughness. The surface roughness was quantified using confocal laser microscopy and the surface oxidation was measured using X-ray photoemission spectroscopy. These results demonstrate that both increasing surface roughness and oxide removal contribute to lowering the PTL/CL interfacial resistance and increasing cell performance.

08 HYDROGEN↗
DOE OSTI2021

Tailoring Interfaces in Solid-State Batteries Using Interfacial Thermochemistry and Band Alignment

Solid-state lithium ion batteries have enhanced thermal stability compared to batteries using liquid electrolytes. Although their practical implementation is limited by undesired side reactions between the electrode and electrolyte, different modification strategies have been proposed to stabilize these reactive interfaces. These approaches have been primarily based upon bulk materials properties, however, which may not necessarily be representative of the chemistry at the solid/solid interface. In this work, first principles calculations and X-ray scattering experiments are used to elucidate molecular-level reactivity and develop design principles for tailored interfaces based on surface and interfacial properties. Because of its well-known instability, the interface between the Li metal anode and the lithium lanthanum titanate (LLTO) solid electrolyte is applied as a model system. Density functional theory calculations are used to describe bulk, surface, and interfacial thermochemistry of the Li/LLTO system, and interfacial reconstruction is probed using ab initio molecular dynamics. These simulations of the Li/LLTO interface demonstrate facile decomposition concomitant with reduction of Ti 4+ ions. Based on further insights from computational analysis of the surface band edge positions, La 2 O 3 is proposed as an interlayer coating and is shown to provide an energetic barrier for interfacial charge transfer and decomposition reactions from X-ray reflectivity measurements and theoretical calculations. The findings in this work suggest that design strategies based on surface and interfacial properties can be used to kinetically stabilize electrode/electrolyte interfaces in solid-state batteries.

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

Co‐Doping Approach for Enhanced Electron Extraction to TiO 2 for Stable Inorganic Perovskite Solar Cells

Inorganic perovskite CsPbI 3 solar cells hold great potential for improving the operational stability of perovskite photovoltaics. However, electron extraction is limited by the low conductivity of TiO 2 , representing a bottleneck for achieving stable performance. In this study, a co‐doping strategy for TiO 2 using Nb(V) and Sn(IV), which reduces the material's work function by 80 meV compared to Nb(V) mono‐doped TiO 2 , is introduced. To gain fundamental understanding of the processes at the interfaces between the perovskite and charge‐selective layer, transient surface photovoltage measurements are applied, revealing the beneficial effect of the energetic and structural modification on electron extraction across the CsPbI 3 /TiO 2 interface. Using 2D drift‐diffusion simulations, it is found that co‐doping reduces the interface hole recombination velocity by two orders of magnitude, increasing the concentration of extracted electrons by 20%. When integrated into n–i–p solar cells, co‐doped TiO 2 enhances the projected T S80 lifetimes under continuous AM1.5G illumination by a factor of 25 compared to mono‐doped TiO 2 . This study provides fundamental insights into interfacial charge extraction and its correlation with operational stability of perovskite solar cells, offering potential applications for other charge‐selective contacts.

14 SOLAR ENERGY↗
DOE OSTI2022

A Polymer Canvas with the Stiffness of the Bone Matrix to Study and Control Mesenchymal Stem Cell Response

Reproducing in vitro the complex multiscale physical features of human tissues creates novel biomedical opportunities and fundamental understanding of cell–environment interfaces and interactions. While stiffness has been recognized as a key driver of cell behavior, systematic studies on the role of stiffness have been limited to values in the KPa–MPa range, significantly below the stiffness of bone. Here, in this work, a platform enabling the tuning of the stiffness of a biocompatible polymeric interface up to values characteristic of human bone is reported, which are in the GPa range, by using extremely thin polymer films on glass and cross-linking the films using ultraviolet (UV) light irradiation. It is shown that a higher stiffness is related to better adhesion, proliferation, and osteogenic differentiation, and that it is possible to switch on/off cell attachment and growth by solely tuning the stiffness of the interface, without any surface chemistry or topography modification. Since the stiffness is tuned directly by UV irradiation, this platform is ideal for rapid and simple fabrication of stiffness patterns and gradients, thus representing an innovative tool for combinatorial studies of the synergistic effect of tissue environmental cues on cell behavior, and creates new opportunities for next-generation biosensors, single-cell patterning, and lab-on-a-chip devices.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

SNL-NJOY-2016

This is a wrapper around the LANL NJOY-2016 code that interfaces with extended code capabilities and minor modification of the LANL NJOY-2016 code that supports modeling radiation damage to materials. The NJOY Nuclear Data Processing System is a modular computer code designed to read evaluated data in ENDF format, transform the data in various ways, and output the results as libraries designed to be used in various applications. The wrapper provided here permits Sandia-specific control parameters to be used in the input data file. The modifications incorporated here enhance the ability of NJOY to address material damage response functions for many materials, e.g. to include the NRT and arc-dpa forms of the damage energy in addition to the default NJOY-2016 implementation of the sharp-threshold Kinchin-Pease threshold energy treatment. All of the modifications provided here are being made available to the GitHub-based NJOY-2016 code. As useful enhancements found here are incorporated into the baseline NJOY-2016 code, they will be eliminated from this version so as to maintain our compatibility with the baseline NJOY-2016 code. SAND2020-13060 M Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA00035

Griffin, Patrick↗
DOE OSTI2021

Sulfur Poisoning and Performance Recovery of SOFC Air Electrodes

The sulfur poisoning and performance recovery of the state-of-the-art SOFC cathodes (La 0 . 80 Sr 0 . 20 ) 0 . 95 MnO 3 ± δ (LSM) and (La 0 . 60 Sr 0 . 40 ) 0 . 95 Co 0 . 20 Fe 0 . 80 O 3 – δ (LSCF), have been studied. Electrochemical impedance spectroscopy measurements of LSCF|GDC and LSM|YSZ half-cells are carried out in alternating atmospheres of air and SO 2 –air at 700°C for hundreds of hours. In the presence of SO 2 , the electrochemical performance of both the cells decays with ohmic and non-ohmic losses, owing to the absorption and chemical interaction of SO 2 with the electrodes. In LSCF, the SrO segregated on the surface tends to absorb and react with SO 2 , forming SrSO 4 followed by the exsolution of Co-Fe. As for LSM, SO 2 is absorbed onto the Sr-rich areas of LSM, including the active reaction sites near the TPBs, leading to Sr exsolution and SrSO 4 formation, leaving a Sr-deficient LSM. During the subsequent exposure to air, the performance of the sulfur-contaminated LSM is almost restored. The LSM particles, exposed to alternating atmospheres of air and SO 2 -air during the electrochemical tests, show a relatively clean surface with sparsely distributed SrSO 4 particles, indicating a high stability against sulfur poisoning. It is suggested that the loosely adsorbed SO 2 at the TPBs is readily swept away by the SO 2 -free air flow, recovering its ORR activity, whereas the Sr-deficient LSM due to Sr-exsolution stays modified, contributing to the incomplete performance restoration. Unlike the case of LSM, the performance of the sulfur-poisoned LSCF partially recovers during the subsequent exposure to air. Correspondingly, the LSCF particles have a modified morphology covered with numerous nanoparticles, mostly SrSO 4 , showing the irreversible aspect of the sulfur poisoning. The morphology modification is not concentrated near the electrode/electrolyte interface but over the entire cathode, indicating that the degree of recovery from sulfur poisoning is closely related to the presence of SrO and chemical activity of Sr in the electrodes at the solid-gas interface. These results also show the potential application of LSM for a sulfur sensor available in high-temperature harsh conditions.

25 ENERGY STORAGE↗
DOE OSTI2021

In situ investigation of conducting interface formation in $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ heterostructure

The high-mobility conducting interface (CI) between LaAlO 3 (LAO) and SrTiO 3 (STO) has revealed many fascinating phenomena, including exotic magnetism and superconductivity. But, the formation mechanism of the CI has not been conclusively explained. Here, using in situ angle-resolved photoemission spectroscopy, we elucidated the mechanisms for the CI formation. In as-grown samples, we observed a built-in potential (V bi ) proportional to the polar LAO thickness starting from the first unit cell (UC) with CI formation appearing above 3 UCs. However, we found that the V bi is removed by synchrotron ultraviolet (UV)-irradiation; The built-in potential is recovered by oxygen gas (O 2 (g))-exposure. Furthermore, after UV-irradiation, the CI appears even below 3UC of LAO. Here, our results demonstrate not only the V bi -driven CI formation in as-grown LAO/STO, but also a new route to control of the interface state by UV lithographic patterning or other surface modification.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Phosphonic-Acid-Reinforced Polymer Hole Transport Layers for Deployable p-i-n Perovskite Photovoltaics

The long-term durability prospects of halide perovskite solar cells are rapidly improving; however, the interface between the hole transport layer (HTL) and the perovskite remains a source of degradation. Alone, polymer- or carbazole-based HTLs suffer from incomplete coverage of the underlying indium tin oxide glass, leading to degradation and compromised performance. Here, we show a multi-HTL approach whereby a polymer HTL is reinforced using a phosphonic acid modification leading to better protection of the buried perovskite interface and more columnar growth of perovskite film, resulting in an ~40-mV open-circuit voltage (VOC) improvement indicative of suppressed interfacial recombination across multiple p-i-n device architectures. Solar cells with this reinforced HTL show higher tolerance to several accelerated stress tests. We report, among the best durabilities for unencapsulated cells, a T90 ~3,000 h (T80 ~5,900 h) at 65 degrees C under continuous 1.2 sun AM 1.5G illumination and maximum power point tracking, representing a nearly 4-fold increase compared with [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz)-only devices. Furthermore, we deployed a device with this reinforced HTL on a cube satellite, with long-duration operational space testing results exceeding T80 for the complete mission duration of ~100 days in low Earth orbit.

14 SOLAR ENERGY↗
DOE OSTI2024

Nanoporous Materials Genome Center Final Technical Report

Nanoporous materials (NPMs), including zeolites/zeotypes, metal-organic frameworks (MOFs), covalent organic frameworks, polymers with intrinsic microporosity, and molecular cages, possess enormous potential in diverse areas relevant to the DOE Office of Science Basic Energy Sciences (BES) mission and objectives. The Nanoporous Materials Genome Center (NMGC) has developed exascale-ready software, computational/theoretical chemistry methods, and data-driven science approaches that enable (i) the de-novo design of functional NPMs for chemical separation and catalysis tasks of increasing complexity, (ii) the discovery of the most promising functional NPMs from databases of synthesized and hypothetical adsorbent structures and the optimization of process conditions for specific applications, and (iii) the microscopic-level understanding of the fundamental interactions underlying the function of NPMs including hierarchical architectures, composite materials, responsive frameworks that may undergo phase transitions or post-synthetic modifications, and materials containing defects, partial disorder, or interfaces. A pivotal part of the NMGC project has been a tight collaboration between leading experimental groups for synthesis and characterization of NPMs and of computational groups that allowed for iterative feedback. The NMGC project has resulted in the publication of more than 290 research and review articles including more than 60 publications in high-impact journals and more than 15 journal covers. NMGC publications have already received more than 20,000 citations (with more than 3,000 citations per year in 2021, 2022, and 2023) and contribute to an h-index of more than 72. The NMGC award has supported collaborative research involving 28 research groups and contributed to the training of more than 40 postdocs, more than 60 graduate students, and more than 20 undergraduate students with broad expertise in data-driven science approaches, computational chemistry methods, and high-performance computing, in addition to the skills to thrive in an integrated experimental and computational research environment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Upgrade of Core Conduction Cooldown Test Facility Control System

The CCCTF was designed and installed at ORNL in the 1990s for high-temperature gas-cooled reactor accident simulation. It is located within a modular hot cell housed in the IFEL facility. In 2008 and 2009, modifications were made to the CCCTF in preparation for AGR safety testing. A new airlock was designed and installed to better support periodic exchange of the fission product deposition cups while maintaining the fuel at safety test temperature, and modifications were made to add routines to the existing user interface software for computer-controlled automation of the He sweep gas flow and liquid nitrogen supply to the 85Kr cold traps. However, the furnace control hardware and software remained essentially unchanged. At the conclusion of the AGR-1 and AGR-2 PIE campaigns, continued use of the CCCTF was in question because of the gradual obsolescence of the hardware and software used to control the furnace and ancillary systems that make up the CCCTF. Therefore, an effort was undertaken to replace all the obsolete components with new hardware and update the software to increase system reliability and ensure this capability’s maintenance for future research and fuel qualification efforts. The modifications included creating a new National Instruments (NI) LabVIEW-based control system with a graphical user interface (GUI).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

3D Tomography insights on particle-particle bonding in cold spray

The conditions of the target surface during cold spray affect deformation and bonding. While surface preparation can influence the adhesion of the first particles, such modification is not relevant to the particle-particle interfaces that dominate the growth of a coating. Here we study two-particle Cu stacks produced with a single-particle launch apparatus and compare them to single-particle experiments on a clean polished substrate. Serial cross-sectioning using microtomography permits a systematic evaluation and quantification of bonding at the particle-particle interfaces. We observe that the top particle in the two-particle stacks is much more flattened compared to single impacts on the polished substrate. Although the resulting interfacial area expansion is comparable to that of single impacts at the same velocities, bonding at the particle-particle interfaces is significantly less (never exceeding 18% even around the “optimal” velocity for bonding). Lastly, we find that hydrodynamic jetting, a form of localization known to promote adhesion in cold spray, is hindered for impacts on top of a prior particle deposition. Here, the results point to a need for future studies that separately consider topography and mechanical properties of substrates in the pursuit of optimal bonding.

Bonding↗
DOE OSTI2021

Self-Healing, Improved Efficiency Solid State Rechargeable Li/I 2 Based Battery

Solid state electrolytes are receiving significant interest due to the prospect of improved safety, however, addressing the incidence and consequence of internal short circuits remains an important issue. In this study, a battery based on a LiI-LiI(HPN) 2 solid state electrolyte demonstrated self-healing after internal shorting where the cells recovered and continued to cycle effectively. The functional rechargeable electrochemistry of the self-forming Li/I 2 -based battery was investigated through interfacial modification by inclusion of Li metal (at the negative interface), and/or fabricated carbon nanotube substrates at the positive interface. A cell design with lithium metal at the negative and a carbon substrate at the positive interface produced Coulombic efficiencies > 90% over 60 cycles. Finally, the beneficial effects of moderately elevated temperature were established where a 10 °C temperature increase led to ~5× lower resistance.

25 ENERGY STORAGE↗
DOE OSTI2026

Modulating Mid-Gap Electronic States Through Site-Selective Modification in B-Pbx/B'-CuyV2O5/CdS Heterostructures for Photocatalytic Hydrogen Evolution

We interfaced ..beta..-Pbx/..beta..'-CuyV2O5 compounds, with varying stoichiometries of precisely positioned Pb-ions (x) and Cu-ions (y) in interstitial sites along a tunnel-structured ?-V2O5 framework, with cysteine-capped CdS (cysCdS) quantum dots (QDs) to yield heterostructured photocatalysts. ..beta..-Pbx/..beta..'-CuyV2O5 compounds exhibit midgap electronic states with orbital contributions from both Cu 3d and stereochemically active Pb 6s states that show distinctive light-initiated reactivity with photoexcited QDs. ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures were prepared by linker-assisted assembly (LAA). Scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy revealed that cysCdS QDs were deposited onto surfaces of ..beta..-Pbx/..beta..'-CuyV2O5 via LAA. HAXPES revealed that the site-selective positioning of Pb-ions and Cu-ions promoted close energetic alignment of the midgap states of ..beta..-Pbx/..beta..'-CuyV2O5 compounds with the valence-band maximum of cysCdS QDs. Transient absorption spectroscopy revealed that photogenerated holes were transferred from CdS QDs to midgap states of ..beta..-Pbx/..beta..'-CuyV2O5 compounds on time scales <50 ps. Finally, photoelectrochemical and photochemical experiments revealed that ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures promoted the photocatalytic reduction of H+ to H2. In photoelectrochemical experiments, under oxidative conditions, for all ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures, H2 was evolved at a Pt counter electrode while a sacrificial donor was oxidized at the heterostructure-functionalized working electrode. In contrast, under reductive conditions, for ..beta..-Pb0.152V2O5/CdS and ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures, H2 was evolved at the working electrode. In photochemical experiments, dispersed ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures promoted the reduction of H+ to H2 under white-light illumination; ..beta..'-Cu0.55V2O5/CdS and ..beta..-Pbx/..beta..'-CuyV2O5/CdS heterostructures, for which midgap states have Cu 3d orbital character, generated 2-fold more H2 than ..beta..-Pb0.152V2O5/CdS heterostructures. Cu-ion insertion thus appends additional acceptor surface states that improve ligand-mediated hole transfer from photoexcited QDs, but such states are intrinsically limited in mediating hole transport to the substrate as a result of the low mobility of holes in narrow Cu 3d-states. Our results reveal that the density and orbital character of midgap states of ..beta..-Pbx/..beta..'-CuyV2O5 compounds, tunable through recently developed site-selective ion insertion strategies, determine efficiencies of charge-transfer and charge-transport mechanisms that underpin photocatalysis.

36 MATERIALS SCIENCE↗