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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 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Enhanced photocatalytic activities of commercial P25 TiO{sub 2} by trapping holes and transferring electrons for CO{sub 2} conversion and 2,4-dichlorophenol degradation

Graphical abstract: TiO{sub 2} Charge separation is enhanced by transferring electrons and trapping holes for improved photoactivities to convert CO{sub 2} and degrade pollutant. - Highlights: • P25 TiO{sub 2} is co-modified with chloride and phosphate anions, and then coupled with CQDs. • Photocatalytic activities for CO{sub 2} reduction and pollutant degradation are improved. • Improved photoactivities are attributed to the enhanced charge separation. • Modified chloride and phosphate anions could effectively trap photogenerated holes. • Coupled CQDs could facilitate photogenerated electrons transfer and separation. - Abstract: In this work, commercial P25 TiO{sub 2} was co-modified with chloride and phosphate anions by a simple impregnation method, and then coupled with carbon quantum dots with a wet-chemical process. It is demonstrated that the photocatalytic activities of P25 TiO{sub 2} for CO{sub 2} conversion and 2,4-dichlorophenol degradation are improved obviously after co-modifying chloride and phosphate anions and then coupling with carbon dots. It is confirmed that the modified chloride and phosphate anions could effectively trap photogenerated holes, while the coupled carbon dots could facilitate photogenerated electrons transfer based on the steady-state surface photovoltage spectra, I–V curves, the electrochemical impedance spectra and the formed ·OH amounts, implying that the photogenerated charge separation of P25 TiO{sub 2} is greatly enhanced, leading to the obviously-improved activities. This work would help us develop a much feasible route to improve the photocatalytic activities of P25 TiO{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Doping and energy band modulation of nanoporous electrodes for enhancing power conversion efficiency of dye-sensitized solar cells

Highlights: • Cd and La are co-doped into TiO{sub 2} by sol-gel method. • La dopant modulates particle size to enhance dye adsorption. • Cd dopant causes decrease in band gap of TiO{sub 2} and creates trap sites. • Only small amount of Cd dopant required for the favorable decrease in band gap. • 24% of efficiency increment for 0.1 mol% Cd-La TiO{sub 2} compared to pure TiO{sub 2}. - Abstract: This work report, for the first time, the co-doping of mesoporous TiO{sub 2} with Cd{sup 2+} and La{sup 3+} cations for improved performance of dye-sensitized solar cells (DSSCs). Cd{sup 2+} ions modify the TiO{sub 2} lattice interstitially and lower the band gap enabling better electron injection. La{sup 3+} ions, having a larger ionic radius compared to that of Ti{sup 4+} ions, occupy interstitial sites and modulate particle size which increase surface area, hence the dye adsorption. The result demonstrates that DSSC employed with 0.1 mol% Cd-La co-doped TiO{sub 2} anode an increase in power conversion efficiency of 24% compared to DSSC with pure TiO{sub 2} anode. The doping concentration has to remain low as not to completely transform the morphology of TiO{sub 2} and to decrease the number of oxygen vacancies forming trap sites for recombination. The selection of ionic radius of dopants is significant as they can modify the TiO{sub 2} lattice either by substitution or interstitial of titanium ions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Tailoring UV-blue sensitization effect in enhancing near infrared emission in X, Yb3+: CaGa2O4 (X = 0, Eu3+, Bi3+, Cr3+) phosphor for solar energy conversion

Highlights: • Intense NIR emission from Yb{sup 3+}:CaGa{sub 2}O{sub 4} phosphor, useful in Si solar cell materials. • Effect of different sensitizers (Eu{sup 3+}, Bi{sup 3+} and Cr{sup 3+} ions) on Yb{sup 3+} ion emission. • Among these, Cr{sup 3+}/ Yb{sup 3+}:CaGa{sub 2}O{sub 4} phosphor is comparatively better NIR emitter. • Study of decay curve and thermoluminescence for analizing energy transfer dynamics. • NIR persistent luminescence for nearly fifteen minutes with germanium doping. - Abstract: This work presents a strategy to modify the UV–vis part of solar spectrum into near infrared (NIR) region- an operational region for silicon solar cells. CaGa{sub 2}O{sub 4}, a wide band gap material, has been doped with Yb{sup 3+} ion and different sensitizers (Bi{sup 3+}, Eu{sup 3+} and Cr{sup 3+}) in order to probe the NIR emitting properties through downconversion (DC) process. Of these, Cr{sup 3+} ion serves the purpose of maximum conversion efficiency in a best way owing to its wide excitation spectrum spanning over the entire UV-blue region. The mechanisms involved in obtained results are supported by the decay curve measurement and energy transfer studies. Further, germainum ion is also doped to get long afterglow Yb{sup 3+} ion emission. This doping develops deep-traps that can store excitation energy and transfer it cooperatively via DC to Yb{sup 3+} for a longer time. Thus, the material is a promising spectral converter for c-Si solar cells and other photochemical processes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Highly sensitive up-conversion optical thermometry based on Yb3+-Er3+ co-doped NaLa(MoO4)2 green phosphors

Highlights: • Phosphors NaLa(MoO{sub 4}){sub 2}:Er{sup 3+}/Yb{sup 3+} UC with intense green emission were synthesized. • The thermometric property based on FIR {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} was evaluated. - Abstract: Pursuing highly sensitive thermometry is a permanent goal in recent scientific research, which can be achieved through Fluorescence intensity ratio (FIR) technique due to its fast response, excellent accuracy, high spatial resolution and tunable size. Herein, highly sensitive micro-thermometers based on FIR of the thermal coupled levels (TCLs) {sup 2}H{sub 11/2}/{sup 4}S{sub 3/2} → {sup 4}I{sub 15/2} from Er{sup 3+} in phosphors NaLa(MoO{sub 4}){sub 2}: Yb{sup 3+}/Er{sup 3+} up-conversion (UC) were developed, which emits dazzling green light with the excitation of 980 nm laser and its UC spectra consisted of intense green bands peaked at 530 and 552 nm and a negligible 658 nm red emission ({sup 4}F{sub 9/2} → {sup 4}I{sub 15/2}), respectively. The maximum absolute sensitivity approached to 0.023 K{sup -1} at 490 K through assessing FIR based on thermo-responsive green emissions. Results suggest the present green-emitting phosphors have great potential to serve as UC thermometers with high and stable sensitivity, which greatly meet the growing demand for sensing applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Stable bismuth-antimony alloy cathode with a conversion-dissolution/deposition mechanism for high-performance zinc batteries

Although a large number of intercalation cathode materials for aqueous Zn batteries have been reported, limited intercalation capacity precludes achieving a higher energy density. Here, for this work, we develop a high-performance aqueous Zn battery based on BiSb alloy (Bi 0.5 Sb 0.5 ) using a high-concentrated strong-basic polyelectrolyte. We demonstrate that a conversion-dissolution/deposition electrochemical mechanism (BiSb ↔ Bi + SbO 2 – ↔ Bi + SbO 3 – ↔ Bi 2 O 3 ) through in situ X-ray diffraction (XRD), Raman, and ex-situ X-ray photoelectron spectrometry (XPS) characterizations with the help of density functional theory calculations. The BiSb cathode delivers large capacity of 512 mAh g –1 at 0.3 Ag –1 and superior rate capability of 90 mAh g –1 even at 20 Ag –1 , and long-term cyclability with capacity retentions of 184 mAh g –1 after 600 cycles at 0.5 Ag –1 and 130 mAh g –1 after 1300 cycles at 1 Ag –1 . Remarkably, even at temperatures as low as –10 and –20 °C, capacities of 210 and 197 mAh g –1 are reserved at 1 Ag –1 , respectively. Moreover, the prepared pouch Zn//BiSb battery delivers a high energy density of 303 Wh kg –1 BiSb at 0.3 Ag –1 . When coupled with a high concentration polyelectrolyte, the Zn/BiSb battery exhibits an excellent performance over a wide temperature range (–40 to 40 °C). Our research reveals the metal cathode is promising for Zn batteries to achieve a high performance with the unique mechanism and alloys can be an effective approach to stabilize metal electrodes for cycling.

25 ENERGY STORAGE↗
DOE OSTI2022

Rationally designed negative electrode for selective CO 2 -to-CO conversion in protonic ceramic electrochemical cells

Protonic ceramic electrochemical cells (PCECs) are solid-state electrochemical devices that employ proton-conducting oxides as electrolytes, which offer a promising approach for electrification of chemical manufacturing, including CO 2 reduction to produce value-added chemicals (e.g., CO). The primary advantage of PCECs is their intermediate operating temperatures (300–600 °C), which thermodynamically and kinetically favor the CO 2 reduction chemistry at the negative electrode. However, the conventional negative electrodes of PCECs, such as BaZr 0.8–x Ce x Y 0.2 O 3-δ -Ni or BaZr 0.8–x Ce x Y 0.1 Yb 0.1 O 3-δ -Ni, cannot reduce CO 2 to either CH 4 or CO with a selectivity of >99 %, leading to the production of a CO and CH 4 mixture. Herein, an oxide-supported in-situ exsolved Ni-Fe alloyed nanoparticle electrocatalyst, Sr 2 Fe 1.4 Mo 0.5 O 6-δ -Ni0.175 (SFM-Ni0.175), is first employed as the negative electrode of PCECs. The PCECs equipped with this new negative electrode selectively favor the CO 2 -to-CO conversion. A selectivity of ~100 % toward CO has been demonstrated over a wide range of operating temperatures (400–600 °C) and applied potentials/current densities. The negative electrode demonstrated in this work fully suppresses the CH 4 production. In situ diffuse reflectance infrared spectroscopy (DRIFTS) was performed to probe the CO 2 reduction mechanisms over both SFM-Ni0.175 and the traditional negative electrode (BCZYYb7111 +Ni), which indicates SFM-Ni0.175 inhibits the formation of formate species, leading to selective production of CO. Finally, this work validates that PCECs equipped with the rationally designed negative electrode can selectively manufacture chemicals.

25 ENERGY STORAGE↗
DOE OSTI2025

Ab initio calculations of overlap integrals for μ → e conversion in nuclei

The rate for μ → e conversion in nuclei is set to provide the most stringent test of lepton-flavor symmetry and a window into physics beyond the Standard Model. However, to disentangle new lepton-flavor-violating interactions, in combination with information from μ → ey and μ → 3e, it is critical that uncertainties at each step of the analysis be controlled and fully quantified. In this regard, nuclear response functions related to the coupling to neutrons are notoriously problematic, since they are not directly constrained by experiment. We address these shortcomings by combining ab initio calculations with a recently improved determination of charge distributions from electron scattering by exploiting strong correlations among charge, point-proton, and point-neutron radii and densities. We present overlap integrals for 27 Al, 48 Ca, and 48 Ti including full covariance matrices, allowing, for the first time, for a comprehensive consideration of nuclear structure uncertainties in the interpretation of μ → e experiments.

ab initio calculations↗
DOE OSTI2025

Process and environmental safety of thermochemical conversion of biomass

Biomass presents a promising opportunity for converting waste into valuable energy, fuels, and chemicals through various thermochemical processes, including hydrothermal carbonization, hydrothermal liquefaction, pyrolysis, gasification, and combustion. However, these processes operate under extreme conditions, introducing significant safety hazards that necessitate meticulous management to prevent accidents. This review discusses potential hazards, risk mitigation strategies, and safety management practices, emphasizing the importance of integrated safety measures into the design and operation of these processes. It also highlights the critical need for robust safety engineering and environmental management strategies tailored to each thermo-chemical process. As these processes transition from laboratory to industrial scale, there is an imperative to develop a clear and concise pathway for emerging industries to achieve regulatory compliance, achieve safety certification, and enable effective stewardship of potential fugitive emissions. By addressing safety and environmental concerns, stakeholders can optimize economic benefits, rural development, and achieve sustained domestic energy generation benefits offered by biomass conversion technologies. Further research on plant design optimization, operational safety, environmental evaluation standardization, and innovative waste management solutions will support the safe and effective scaling of these technologies, ultimately contributing to sustainable management and resource recovery.

09 - BIOMASS FUELS↗
DOE OSTI2023

High-voltage monocrystalline Si photovoltaic minimodules based on poly -Si/SiO x passivating contacts for high-power laser power conversion

By using photovoltaic cells under high-intensity laser illumination, much higher photoconversion efficiencies are obtained than under the solar spectrum. Here we demonstrate a monocrystalline Si based minimodule to convert laser light into electricity using edge-illuminated Si "minicells" based on polysilicon on silicon oxide passivating contacts. Ten fully metallized devices were stacked in series and illuminated from the edge, creating a high-voltage, low-current minimodule that mitigates resistive and Auger-Meitner losses. The minimodule shows a high open-circuit voltage of >5 V when tested under 1-Sun illumination and >7 V at higher illumination intensities when tested with a flash simulator. The fill factor in these minimodules is limited by shunting at low illuminations but reaches a maximum of ~78% for higher illumination intensities >40 Suns (current density >1200 mA/cm 2 ), indicating that the minimodules are not limited by series resistance up to 40 Suns. Under 1000 nm monochromatic light, we measure efficiencies >40% at > 40 Suns equivalent illumination, showing the potential of passivated contact Si cells for laser power conversion.

14 SOLAR ENERGY↗
DOE OSTI2014

Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application

Highlights: • Concept to convert waste to valuable product is carried out in this study. • An industrially feasible and cost-effective approach was developed and optimized. • Highly crystalline and well-defined zeolite was produced under moderate conditions. • The zeolite derived from the bauxite tailings displayed high ion exchange capacity. • Bauxite tailings have potential application in heavy metal ions adsorbent. - Abstract: Bauxite tailings are a major type of solid wastes generated in the flotation process. The waste by-products caused significant environmental impact. To lessen this hazardous effect from poisonous mine tailings, a feasible and cost-effective solution was conceived and implemented. Our approach focused on reutilization of the bauxite tailings by converting it to 4A zeolite for reuse in diverse applications. Three steps were involved in the bauxite conversion: wet-chemistry, alkali fusion, and crystallization to remove impurities and to prepare porous 4A zeolite. It was found that the cubic 4A zeolite was single phase, in high purity, with high crystallinity and well-defined structure. Importantly, the 4A zeolite displayed maximum calcium ion exchange capacity averaged at 296 mg CaCO{sub 3}/g, comparable to commercially-available zeolite (310 mg CaCO{sub 3}/g) exchange capacity. Base on the optimal synthesis condition, the reaction yield of zeolite 4A from bauxite tailings achieved to about 38.43%, hence, this study will provide a new paradigm for remediation of bauxite tailings, further mitigating the environmental and health care concerns, particularly in the mainland of PR China.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Functional carbons and carbon nanohybrids for the catalytic conversion of biomass to renewable chemicals in the condensed phase

The production of chemicals from lignocellulosic biomass provides opportunities to synthesize chemicals with new functionalities and grow a more sustainable chemical industry. However, new challenges emerge as research transitions from petrochemistry to biorenewable chemistry. Compared to petrochemisty, the selective conversion of biomass-derived carbohydrates requires most catalytic reactions to take place at low temperatures (< 300°C) and in the condensed phase to prevent reactants and products from degrading. The stability of heterogeneous catalysts in liquid water above the normal boiling point represents one of the major challenges to overcome. Herein, we review some of the latest advances in the field with an emphasis on the role of carbon materials and carbon nanohybrids in addressing this challenge.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Integrated Approach to CO 2 Capture and Conversion to Cyclic Carbonates under Solvent- and Additive-Free Conditions Utilizing the CO 2 Capture Solvent EEMPA

An integrated CO 2 capture and conversion to materials (IC 3 M) implementation utilizing a CO 2 capture solvent is an efficient approach to reduce the amount of CO 2 in the atmosphere while producing value-added chemicals. In this work, we demonstrate that the advanced water-lean CO 2 capture solvent, N-(2-Ethoxyethyl)-3-morpholinopropan-1-amine (EEMPA), can catalyze the cycloaddition reaction between CO 2 and propylene oxide to produce the value-added chemical propylene carbonate in an IC 3 M fashion. When excess propylene oxide is used relative to EEMPA, yields as high as 75% with 85% selectivity toward propylene carbonate can be achieved under solvent-free conditions without the need of additives/cocatalysts. The reaction temperature (120 °C) is comparable to that used in the thermal regeneration of the capture solvent under industrial conditions. Formation of an undesired amino alcohol side product was observed, but it may be reversible or avoidable with continued research despite the unsuccessful initial attempts. Finally, we show that this can be applied to other epoxides for the production of various cyclic carbonates.

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

MZA: A Data Conversion Tool to Facilitate Software Development and Artificial Intelligence Research in Multidimensional Mass Spectrometry

Modern mass spectrometry-based workflows employing hybrid instrumentation and orthogonal separations collect multidimensional data, potentially allowing deeper understanding in omics studies through adoption of artificial intelligence methods. However, the large volume of these rich data challenges existing data storage and access technologies, therefore precluding informatics advancements. Here we present MZA™ (pronounced m-za), the mass-to-charge (m/z) generic data storage and access tool designed to facilitate software development and artificial intelligence research in multidimensional mass spectrometry measurements. Composed by a data conversion tool and a simple file structure based on the HDF5 format, MZA provides easy, cross-platform and efficient programmatic access to raw MS-data, enabling fast development of new tools in data science programming languages such as Python and R. The software executable and example Python and R scripts are freely available at https://github.com/PNNL-m-q/mza.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Relief Zones Enhance the Durability of Ultrathin Membranes in Electrochemical Conversion Devices

Premature failures in electrochemical conversion systems often result when membrane electrode assemblies (MEAs) use ultrathin (≤15 μm-thick) polymer electrolyte membranes, susceptible to mechanical degradation from stress concentrations arising from device-level integration. Herein, relief zones were developed to mitigate mechanical degradation by alleviating excess and nonuniform compression across active areas. Relief zones, created through ablation of carbonaceous diffusion media, enable seamless adaptation across MEA dimensions without need for hardware modifications. Demonstrated using fuel cells as a case study, accelerated stress tests revealed a 6-fold lifetime improvement (∼1500 h) compared to conventional edge-protected MEAs, decoupling device-level engineering effects from material limitations.

accelerated stress test↗
DOE OSTI2025

Compositionally Complex Spinel Oxides as Conversion Anodes for Lithium-Ion Batteries

Four different compositionally complex multicomponent M 3 O 4 spinels containing 5–8 distinct metals were prepared by a rapid combustion synthesis method or solvothermal synthesis. High resolution synchrotron X-ray diffraction patterns show that the materials consist primarily of spinel phases with small amounts of rock salt impurities, and, in several samples, a minor amount of contracted spinel phase. Materials were investigated as conversion anodes in lithium half-cells and delivered significantly higher capacities than two-component MgFe 2 O 4 made by combustion synthesis. X-ray absorption near-edge structure (XANES) was used to estimate the oxidation states of the metals in the pristine, lithiated (discharged) and delithiated (charged) materials to better understand the redox processes in half cells that led to the improvement. Co, Ni, and Zn are reduced to low oxidation states during lithiation (cell discharge) but are only partially oxidized. The presence of a conductive metallic network that forms after lithiation is thought to account for the improved electrochemical characteristics. Interestingly, in most of the samples, iron is not fully reduced during initial lithiation unlike what happens with a set of related high entropy spinel ferrites studied previously. Finally, the improved electrochemical properties of these materials illustrates both the advantages of complexity and the difficulties in predicting their behavior.

25 ENERGY STORAGE↗
DOE OSTI2025

Linking Pressure to Electrochemical Evolution in Solid-State Conversion Cathode Composites

Conversion-type cathodes, such as sulfur, FeS 2 , and FeF 3 , offer high theoretical capacities in solid-state lithium batteries but are hindered by substantial volume changes during cycling, leading to interfacial contact loss, crack formation, and microstructural degradation. Here, we investigate the relationships between electrochemical, mechanical, and structural evolution in solid-state electrode composites with these three active materials. Using real-time stack-pressure monitoring, synchrotron X-ray absorption spectroscopy, and electrokinetic modeling, we elucidate how stress evolution is linked to reversible and irreversible redox reactions. Nonlinear stack pressure evolution in cells with sulfur, FeS 2 , and FeF 3 electrode composites is found to arise from material-specific volume changes, the balance of volume change between the working and counter electrode, and the formation of distinct reaction intermediates. The three materials exhibit distinct stack pressure evolution, which is closely related to the different reaction processes in the materials, as demonstrated with X-ray absorption spectroscopy measurements. Through mesoscale modeling, we relate the experimental measurements to species evolution at the particle scale and track the dynamic coexistence of intermediate phases. Our findings highlight the importance of designing for volume changes of a given active material in solid-state battery systems.

batteries↗
DOE OSTI2018

Selectivity of Synthesis Gas Conversion to C 2+ Oxygenates on fcc(111) Transition-Metal Surfaces

Using a combined density functional theory and descriptor based microkinetic model approach, we predict production rate volcanos for higher oxygenate formation on (111) transition-metal surfaces. Despite their lower activity for CO conversion compared to stepped surfaces, (111) transition metal surfaces bring the potential for selectivity toward C 2+ oxygenates. As a result, the volcano plots can be used to rationalize and predict activity and selectivity trends for transition-metal-based catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Manifesto on the Thermochemistry of Nanoscale Redox Reactions for Energy Conversion

Advancements in the use of nanoscale materials for energy conversions will rely on a clear understanding of reaction thermochemistry. While band edge and Fermi energies can be rigorous thermodynamic descriptors of bulk materials, we show here that their application to nanoscale systems is problematic. A change of one electron at a 1000 atom nanoparticle or a localized surface site on a catalyst/electrode causes significant nuclear reorganization of the system. Electron transfer is often coupled with solvent reorganization and/or with the transfer of ions, including ion intercalation, surface binding, and movement within the surrounding double layer. These effects can be significant (even for some bulk materials). However, Fermi and band energies, as typically used, do not include the energetics of nuclear reorganizations or cation coupling. A comprehensive approach to nanoscale charge transfer thermodynamics must explicitly consider these effects in order to have a more complete understanding and greater control of nanoscale redox reactivity.

30 DIRECT ENERGY CONVERSION↗