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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

In Situ Conversion of Artificial Proton‐Rich Shell to Inorganic Maskant Toward Stable Single‐Crystal Ni‐Rich Cathode

Single-crystal high-nickel oxide with an integral structure can prevent intergranular cracks and the associated detrimental reactions. Yet, its low surface-to-volume ratio makes surficial degradation a more critical factor in electrochemical performance. Herein, artificial proton-rich (ammonium bicarbonate) shell is successfully introduced on the nickel-rich LiNi 0.92 Co 0.06 Mn 0.02 O 2 single crystals for in situ electrochemically conversing into inorganic maskant to enhance stability of cathode. The process is that the surficial enriched proton, once released from the ammonium bicarbonate shell (proton reservoir) during 1st charge, is immediately captured by LiPF 6 , in situ electrochemically conversing to LiF and Li 3 PO 4 sub-nano particle dense maskant (sub-nano F-&P-maskant). The in situ formed compact nano F-&P-maskant significantly resists the cathode against electrolyte attack and improves the surface stability of particles during long-term cycling. Consequently, this surface modification enables 95% capacity retention after 100 cycles at a high voltage of 4.5 V in the half cell and 83% capacity retention after 800 cycles in the full cell. In conclusion, this work demonstrates a strategy for reconstructing the protective layer using the rational design of surficial enriched proton shells for advanced lithium batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Anion Reactivity in Cation‐Disordered Rocksalt Cathode Materials: The Influence of Fluorine Substitution

Abstract The demand for high energy‐density, mass‐producible cathode materials has spurred the exploration of new material structures and compositions. Lithium‐excess, cation‐disordered rocksalt (DRX) materials are a new class of transition metal oxides that display high capacity and environmental friendly composition. These materials achieve their high capacities partially through oxygen redox, which leads to oxygen loss and detrimental reactivity with the electrolyte. It has previously been shown that oxygen loss can be suppressed by partial substitution of the lattice oxygen for fluorine, but the explicit mechanism behind this effect remains unknown. In this work, differential electrochemical mass spectrometry (DEMS) and titration mass spectrometry are used to quantify the primary electrochemical reactions occurring during the first cycle in DRX materials. Comparing a DRX oxide and a DRX oxyfluoride, it is shown that fluorination limits oxygen redox and suppresses oxygen loss. Additionally, DEMS is coupled with fluoride‐scavenging to demonstrate that small amounts of fluorine dissolve from DRX oxyfluorides during the first cycle. Finally, these techniques are extended over the first several cycles, demonstrating that CO 2 evolution persists and fluoride dissolution continues to a diminishing extent during the first few cycles. These findings motivate surface modifications to control interfacial reactivity and improve long‐term cycling.

Crafton, Matthew J.↗
DOE OSTI2024

Li Stripping Behavior of Anode‐Free Solid‐State Batteries Under Intermittent‐Current Discharge Conditions

Anode‐free manufacturing holds promise to enable high energy densities and lower Lithium (Li)‐metal solid‐state batteries (LMSSBs). Nevertheless, in contrast to thick Li foil (>50 µm), the stripping capacity of in situ‐formed Li (10–30 µm) is limited due to diminished creep flow, resulting in reduced accessible capacity. This study explores the correlation between stripping capacity and surface roughness of garnet Li 7 La 3 Zr 2 O 12 (LLZO) solid electrolyte. The results reveal that stripping capacity can be enhanced through the surface modification of solid electrolytes. Additionally, this study scrutinizes the stripping behavior of in situ Li under intermittent‐current discharge conditions, which are more relevant to the operational conditions of electric vehicles (EVs). It is demonstrated that, when compared to constant‐current stripping, intermittent‐current stripping effectively suppresses void formation and enhances the stripping capacity of in situ Li by 40%. It is considered that the intermittent current inhibits the accumulation of Li vacancies, thereby delaying the void formation. These findings provide valuable insights into the development of high‐performance anode‐free LMSSBs for EVs.

25 ENERGY STORAGE↗
DOE OSTI2023

Pathways Toward Efficient and Durable Anion Exchange Membrane Water Electrolyzers Enabled By Electro‐Active Porous Transport Layers

Abstract Green hydrogen, produced via water electrolysis using renewable electricity, will play a crucial role in decarbonizing industrial and heavy‐duty transportation sectors. Anion exchange membrane water electrolyzers (AEMWEs) can overcome many of the performance and cost limitations of incumbent technologies, however, still suffer from durability challenges due to oxidative instability of anion‐exchange ionomers. Herein, the use of an electro‐active porous transport layer as anode (PTL‐electrode) is demonstrated to enable efficient and durable AEMWEs. The stainless‐steel PTL‐electrodes are shown to have superior performance and durability compared to traditional catalyst layers containing ionomer and nanoparticle catalysts. An AEMWE cell operating at 2 A cm −2 for over 600 h exhibited a degradation rate of just 5 µV h −1 . During operation, the surface composition of the stainless steel transforms into a mixture of iron and nickel oxyhydroxides, contributing to enhanced oxygen‐evolution reaction activity. The combination of experimental work and modeling elucidates how the bulk structure of the PTL‐electrode offers an additional design dimension to further improve electrolyzer performance. Lastly, a surface modification strategy is applied to a PTL‐electrode to achieve an even higher performing AEMWE (2.3 vs 2.0 A cm −2 at 1.8 V). Overall, this work lays out pathways toward more efficient, durable, and affordable AEMWEs.

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

Advancing Insights into Electrochemical Pre‐Treatments of Supported Nanoparticle Electrocatalysts by Combining a Design of Experiments Strategy with In Situ Characterization

Activation, break-in, and/or pre-treatment protocols are generally applied to energy conversion devices before regular operation to reach stable performance. There remains much to understand about the relationships among physical properties, performance, and electrochemical pre-treatments. Here, a design-of-experiments (DoE) strategy is employed to address this gap by demonstrating the influence of five pre-treatment parameters for carbon-supported Pt-nanoparticle catalysts on the electrocatalytic oxygen reduction reaction (ORR). A subset of pre-treatments, developed using a central composite design, are tested in a flow cell combined with an inductively-coupled plasma mass spectrometer (on-line ICP-MS). The DoE-based approach facilitates comprehensive insights from two orders of magnitude fewer experiments than a conventional grid search. The coupled on-line ICP-MS setup enables effective catalysis and real-time catalyst dissolution data. Leveraging insights from DoE for on-line ICP-MS and additional characterization, a model is built between the degradation of a multi-dimensional supported Pt surface, its performance, and applied electrochemical parameters. These investigations identify surface modifications, such as oxidation, and subsequent restructuring of Pt during pre-treatment as a primary cause of performance deterioration during ORR. By combining DoE with advanced characterization techniques, a powerful approach is demonstrated to gain a mechanistic understanding of pre-treatment protocols that can be broadly adapted to various reaction chemistries.

Platinum↗
DOE OSTI2024

Engineering Active Sites of Metal/Metal Oxide Catalysts by Oxide Ligand Overlayers

Abstract Engineering sites of supported metal catalysts is essential to enhancing activity and selectivity. Such enhancement is typically achieved by particle size modification, surface alloying, or attaching molecular ligands. Yet, control strategies for complex, multifunctional molecules and catalysts, where selectivity is crucial, are lacking. Here, we demonstrate that submonolayer WO x with tunable coverage preferentially decorates well‐coordinated Pt terrace sites as a stable ligand. By combining experimental kinetics with probe molecules, in situ spectroscopies, and first‐principles modeling, we show that the WO x coverage on Pt modifies the metal‐to‐acid site balance while retaining the acid strength intact and results in optimal reactivity for metal‐acid catalyzed reactions at a specific metal, size, and support‐dependent WO x coverage. The oxide can also alter the reactant adsorption mode, reversing selectivity and pathways from terrace‐ to step‐dominated, as evidenced in furfural decarbonylation and hydrogenation. The insights open avenues for improving metal/metal oxide catalysts beyond the specific system.

Zhou, Jiahua↗
DOE OSTI2025

Technical Routes to Achieve High Circular Polarized Luminescence in Chiral Perovskites: A Mini‐Review

Chiral hybrid organic-inorganic perovskites (HOIPs) have emerged as promising materials for optoelectronic and spintronic applications, leveraging unique properties such as circularly polarized luminescence (CPL), circularly polarized nonlinear optical (NLO) emission, and chiral-induced spin selectivity (CISS). However, challenges remain in stabilizing these materials under environmental stresses and precisely controlling chirality for scalable use. This review summarizes five main strategies to induce chirality in HOIPs, i.e., direct incorporation of chiral cations, surface modification with chiral ligands, ion doping, template-induced chirality, and chiral metasurfaces. Each approach offers distinct advantages for optimizing CPL efficiency and device stability, paving the way for next-generation applications in CPL detectors, information encryption, spintronic devices, etc.

14 SOLAR ENERGY↗
DOE OSTI2020

Energetic Tug-of-War between Pt and Leaky TiO 2 : Positive and Negative Effects on the Function of Molecularly-Modified p -Si(111)|TiO 2 |Pt Photocathodes

Photoelectrochemical solar energy conversion to chemical products is a promising avenue towards renewable fuels, and TiO 2 deposition on semiconductor photocathodes is a widespread surface protection strategy. However, the electronic, thermodynamic, and kinetic effects of protection layers on interfacial energetics remains poorly understood. Here, electrochemical data (photocurrent onset and flatband potentials) of p-Si(111)|TiO 2 |Pt is collected in contact with an outer-sphere redox couple. We find that onset potentials shift negatively as a function of increasing oxide thickness, but this effect is not reflected in the flatband potentials. This reveals the mechanism of these shifts is kinetic rather than thermodynamic,and suggests that hole leakage through the TiO 2 is responsible. When Pt nanoparticles are deposited onto the TiO 2 , positive shifts in both the onset and flatband potentials are observed, revealing Pt catalysts are beneficial for more than just increased catalytic rates. These results highlight the importance of understanding the effects of surface modifications on the energetics at the interface in both catalytic and simple electron transfer systems.

14 SOLAR ENERGY↗
DOE OSTI2022

Hydrothermal synthesis of chiral carbon dots

Abstract Nanocolloids that are cumulatively referred to as nanocarbons, attracted significant attention during the last decade because of facile synthesis methods, water solubility, tunable photoluminescence, easy surface modification, and high biocompatibility. Among the latest development in this reserach area are chiral nanocarbons exemplified by chiral carbon dots (CDots). They are expected to have applications in sensing, catalysis, imaging, and nanomedicine. However, the current methods of CDots synthesis show often contradictory chemical/optical properties and structural information that required a systematic study with careful structural evaluation. Here, we investigate and optimize chiroptical activity and photoluminescence of L‐ and D‐ CDots obtained by hydrothermal carbonization of L‐ and D‐ cysteine, respectively. Nuclear magnetic resonance spectroscopy demonstrates that they are formed via gradual dehydrogenation and condensation reactions of the starting amino acid leading to particles with a wide spectrum of functional groups including aromatic cycles. We found that the chiroptical activity of CDots has an inverse correlation with the synthesis duration and temperature, whereas the photoluminescence intensity has a direct one, which is associated with degree of carbonization. Also, our studies show that the hydrothermal synthesis of cysteine in the presence of boric acid leads to the formation of CDots rather than boron nitride nanoparticles as was previously proposed in several reports. These results can be used to design chiral carbon‐based nanoparticles with optimal chemical, chiroptical, and photoluminescent properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Evidence of plasma‐driven decomposition of common plastics exposed to an atmospheric nonthermal discharge

Abstract A nonthermal, pulsed spark discharge is applied to three polymer powders in Ar and Ar– gas mixtures. Hydrogen is introduced to assess plasma‐driven decomposition. Gaseous decomposition products, including methane, acetylene, and ethylene, are observed with Fourier‐transform infrared (FTIR). Surface modifications are observed on the residual polymer via attenuated total internal reflection‐FTIR. Time‐averaged rotational, vibrational, and excitation temperatures are characterized in the discharge. The plasma density is found to be around , with rotational and vibrational temperatures ranging from 1500 to 2200 K and an excitation temperature of 1–2 eV. While spark properties did not change with either gas composition or polymer composition, it was determined that the addition of hydrogen promoted higher concentrations of gaseous phase products (promoting hydrogenolysis).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Activating Layered Metal Oxide Nanomaterials via Structural Engineering as Biodegradable Nanoagents for Photothermal Cancer Therapy

Layered metal oxides including MoO 3 and WO 3 have been widely explored for biological applications owing to their excellent biocompatibility, low toxicity, and easy preparation. However, they normally exhibit weak or negligible near-infrared (NIR) absorption and thus are inefficient for photo-induced biomedical applications. Herein, the structural engineering of layered MoO 3 and WO 3 nanostructures is first reported to activate their NIR-II absorption for efficient photothermal cancer therapy in the NIR-II window. White-colored micrometre-long MoO 3 nanobelts are transformed into blue-colored short, thin, defective, interlayer gap-expanded MoO 3–x nanobelts with a strong NIR-II absorption via the simple lithium treatment. The blue MoO 3–x nanobelts exhibit a large extinction coefficient of 18.2 L g –1 cm –1 and high photothermal conversion efficiency of 46.9% at 1064 nm. After surface modification, the MoO 3–x nanobelts can be used as a robust nanoagent for photoacoustic imaging-guided photothermal therapy to achieve efficient cancer cell ablation and tumor eradication under irradiation by a 1064 nm laser. Importantly, the biodegradable MoO 3–x nanobelts can be rapidly degraded and excreted from body. We report the study highlights that the structural engineering of layered metal oxides is a powerful strategy to tune their properties and thus boost their performances in given applications.

36 MATERIALS SCIENCE↗
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 OSTI2025

Cooperative and bifunctional Ga-Ca-Cr 2 O 3 @CaO structured monoliths as versatile platform for reactive capture of CO 2 and its subsequent conversion to ethylene

Cooperative and bifunctional materials (BFMs) that integrate adsorbents and catalysts offer a promising strategy for the reactive capture of CO 2 to produce valuable fuels and chemicals. In this study, we developed structured BFMs via 3D printing that combine CaO as an adsorbent with Ga–Ca–Cr 2 O 3 metal oxides as the catalyst for the reactive capture of CO 2 and its subsequent conversion to C 2 H 4 via the oxidative dehydrogenation of C 2 H 6 (CO 2 -ODHE). Three different Ga–Ca compositions were used to modify the catalyst surface characteristics and enhance C 2 H 4 selectivity. In these formulations, Ga ions stabilize the oxygen lattice of the BFM, while Ca ions interact strongly with Cr to form CaCrO 4 , thereby altering the oxygen species and enhancing the material’s basic properties. Under adsorption–reaction conditions at 600–650 °C, the optimal BFM achieved an excellent C 2 H 4 selectivity of 96.4 %, attributed to a balanced redox process and improved basicity that facilitate efficient C 2 H 6 conversion and rapid desorption of C 2 H 4 without excessive oxidation. Overall, this work provides new insights into the formulation of BFMs monoliths and highlights the critical role of catalytic surface modification in enhancing C 2 H 4 selectivity in the CO 2 -ODHE reactive capture process.

C2H4 production↗
DOE OSTI2021

A bifunctional zeolitic porous liquid with incompatible Lewis pairs for antagonistic cascade catalysis

The emergence of porous liquids (PLs) opened opportunities to form unique antagonistic systems capable of fulfilling cascade reactions promoted by incompatible active sites in one pot, which is a long-term challenging subject in catalysis. Herein, unique bifunctional type III PL-based systems were facilely fabricated via assembly of zeolite nanosheets with ionic liquids. Rational structural design afforded PLs that feature high zeolite concentration, stable dispersion after 2 years, abundant cavity distribution, and involvement of antagonistic groups (acid and base sites) in separated and active form via steric hindrance control and electronic repulsion regulation. These unique properties worked cooperatively to fulfill the cascade deacetalization-Knoevenagel/Aldol condensation in one pot with superior catalytic efficiency outperforming the traditional systems. The key to success lies in the formation of bifunctional composites, transformation of zeolite from heterogeneous to homogeneous via surface modification, as well as rapid mass transfer ensured by the rigid porous architecture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Development of an anti-clogging perforated plate atomizer for a zero liquid discharge humidification-dehumidification desalination system

An anti-clogging perforated plate atomizer is designed for high temperature and salinity applications in a novel solar-powered zero liquid discharge humidification-dehumidification desalination system (US Patent Application US62882953). Herein this paper presents a detailed discussion on its design, and operation. Experiments are performed on seven atomizers to study the effect of design, and operating parameters on spray cone angle, and average droplet diameter. Spray cone angle remains constant with change in air mass flux, and increases with increasing orifice diameter, and manifold diameter. It also increases initially with water mass flow rate, and manifold height, before attaining a constant value. Average droplet diameter increases with increasing water mass flow rate, and decreasing air mass flux, orifice diameter, and manifold diameter. Further, anti-clogging performance of the atomizer is tested with hypersaline water of 100,000 ppm total dissolved solid (NaCl) at elevated temperatures such as air at 175 °C and saline water at 45 °C. Results show no clogging for 2–13 h of operation. Near-complete suppression of atomizer clogging makes our new additively-manufactured perforated plate atomizer an ideal fit for high salinity, and zero liquid discharge humidification-dehumidification desalination systems. Additionally, its open-surface design allows additional surface modifications to further reduce clogging, and enhance self-cleaning characteristics.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Artificial cathode electrolyte interphase for improving high voltage cycling stability of thick electrode with Co-free 5 V spinel oxides

Spinel-type cathode LiNi 0.5 Mn 1.5 O 4 (LNMO) has intrigued the transportation industry due to its high operating voltage and total elimination of the expensive cobalt element. However, LNMO cathode with high mass loading (> 3 mAh/cm 2 in areal capacity) has suffered from excessive capacity degradation upon long cycling. Here, a robust Al 2 O 3 surface layer is introduced to the thick LNMO electrode via atomic layer deposition (ALD). The capacity retention in full cells with the graphite anode is improved from 46.3% to 75.3% after 300 cycles with cutoff voltage up to 4.85 V, while enabling average Coulombic efficiency of 99.9% during the cycling. The post-mortem analyses reveal that the Al 2 O 3 surface layer would convert to Al-O-F /Al-F species upon cycling, offering stable interphase to protect the cathode material. Furthermore, these results demonstrate the significance of surface modification enabling high voltage cathode for next-generation LIBs.

25 ENERGY STORAGE↗
DOE OSTI2021

Role of mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9-δ barrier layer on the promotion of SOFC performance

The cathode activity in a solid oxide fuel cell can be promoted by introducing various catalysts to reduce its polarization resistance towards oxygen reduction, and thus improve cell performance. Here, in this work, the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) cathode surface is modified by the infiltration of Pr 6 O 11 and the power density at 0.8 V and 750 °C is improved by 21%. Moreover, by replacing the traditional barrier layer Gd 0.2 Ce 0.8 O 1.9 with mixed conducting Pr 0.1 Gd 0.1 Ce 0.8 O 1.9 (PGCO), the power density increases by 38%. The ohmic resistance is dramatically reduced by applying the PGCO interlayer. The distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased, attributing to the mixed conduction nature in PrO x . An increase of power density, ~0.358 W/cm 2 (71%) at 0.8 V, is achieved with the implementation of both surface modification and buffer layer engineering.

08 HYDROGEN↗