An Effective Lithium Sulfide Encapsulation Strategy for Stable Lithium-Sulfur Batteries
Not provided.
Chemistry↗
SEARCH · Engineering Papers
Results for “date”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Single-Crystalline Ultrathin Co 3 O 4 Nanosheets with Massive Vacancy Defects for Enhanced Electrocatalysis
The role of vacancy defects is demonstrated to be positive in various energy-related processes. However, introducing vacancy defects into single-crystalline nanostructures with given facets and studying their defect effect on electrocatalytic properties remains a great challenge. Here this paper deliberately introduces oxygen defects into single-crystalline ultrathin Co 3 O 4 nanosheets with O-terminated {111} facets by mild solvothermal reduction using ethylene glycol under alkaline condition. As-prepared defect-rich Co 3 O 4 nanosheets show a low overpotential of 220 mV with a small Tafel slope of 49.1 mV dec -1 for the oxygen evolution reaction (OER), which is among the best Co-based OER catalysts to date and even more active than the state-of-the-art IrO 2 catalyst. Such vacancy defects are formed by balancing with reducing environments under solvothermal conditions, but are surprisingly stable even after 1000 cycles of scanning under OER working conditions. Density functional theory plus U calculation attributes the enhanced performance to the oxygen vacancies and consequently exposed second-layered Co metal sites, which leads to the lowered OER activation energy of 2.26 eV and improved electrical conductivity. Finally, this mild solvothermal reduction concept opens a new door for the understanding and future designing of advanced defect-based electrocatalysts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Another Strategy, Detouring Potential Decay by Fast Completion of Cation Mixing
Abstract not provided
Liu, Shuai↗
Bandgap Narrowing in Non‐Fullerene Acceptors: Single Atom Substitution Leads to High Optoelectronic Response Beyond 1000 nm
Abstract Two narrow bandgap non‐fullerene acceptors (NBG‐NFAs), namely, COTIC‐4F and SiOTIC‐4F, are designed and synthesized for the fabrication of efficient near‐infrared organic solar cells (OSCs). The chemical structures of the NBG‐NFAs contain a D′‐D‐D′ electron‐rich internal core based on a cyclopentadithiophene (or dithienosilole) (D) and alkoxythienyl (D′) core, end‐capped with the highly electron‐deficient unit 2‐(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐inden‐1‐ylidene)malononitrile (A), ultimately providing a A‐D′‐D‐D′‐A molecular configuration that enhances the intramolecular charge transfer characteristics of the excited states. One can thereby reduce the optical bandgap ( E g opt ) to as low as ≈1.10 eV, one of the smallest values for NFAs reported to date. In bulk‐heterojunction (BHJ) OSCs, NBG‐NFA blends with the polymer donor PTB7‐Th yield power conversion efficiencies (PCE) of up to 9.0%, which is particularly high when compared against a range of NBG BHJ blends. Most significantly, it is found that, despite the small energy loss ( E g opt − e V OC ) of 0.52 eV, the PTB7‐Th/NBG‐NFA bulk heterojunction blends can yield short‐circuit current densities of up to 22.8 mA cm −2 , suggesting that the design and application of NBG‐NFA materials have substantial potential to further improve the PCE of OSCs.
Lee, Jaewon↗
Improved Efficiency and Stability of Pb/Sn Binary Perovskite Solar Cells Fabricated by Galvanic Displacement Reaction
In this work, a simple and generally applicable method of fabricating efficient and stable Pb-Sn binary perovskite solar cells (PVSCs) based on a galvanic displacement reaction (GDR) is demonstrated. Different from the commonly used conventional approaches to form perovskite precursor solutions by mixing metal halides and organic halides such as PbI 2 , SnI 2 , MAI, FAI, etc., together, the precursor solutions are formulated by reacting pure Pb-based perovskite precursor solutions with fine Sn metal powders. After the ratios between Pb and Sn are optimized, high PCEs of 15.85% and 18.21% can be achieved for MAPb 0.4 Sn 0.6 I 3 and (FAPb 0.6 Sn 0.4 I 3 ) 0.85 (MAPb 0.6 Sn 0.4 Br 3 ) 0.15 based PVSCs, which are the highest PCEs among all values reported to date for Pb-Sn binary PVSCs. Moreover, the GDR perovskite-based PVSCs exhibit significantly improved ambient and thermal stability with encapsulation, which can retain more than 90% of their initial PCEs after being stored in ambient (relative humidity (RH) ≈50%) for 1000 h or being thermal annealed at 80 °C for more than 120 h in ambient conditions. These results demonstrate the advantage of using GDR to prepare tunable bandgap binary perovskites for devices with greatly improved performance and stability.
36 MATERIALS SCIENCE↗
Tailoring FeN 4 Sites with Edge Enrichment for Boosted Oxygen Reduction Performance in Proton Exchange Membrane Fuel Cell
Transition metal atoms with corresponding nitrogen-coordination (MNx moieties) are widely proposed as catalytic centers for the oxygen reduction reaction (ORR) in metal-nitrogen-carbon (M-N-C) catalysts. Here, an effective strategy that can tailor Fe-N-C catalysts to simultaneously enrich the number of active sites while boost their intrinsic activity and utilization is reported. This is achieved by edge engineering of FeN 4 sites via a simple ammonium chloride salt-assisted approach, where a high fraction of FeN 4 sites are preferentially generated and hosted in a graphene-like porous scaffold. Theoretical calculations demonstrate that the FeN 4 moieties with adjacent pore defects are likely to be more active than the non-defective configuration. Coupled with the facilitated accessibility of active sites, this prepared catalyst when applied in a practical H 2 -air proton exchange membrane fuel cell delivers a remarkable peak power density of 0.43 W cm -2 , ranking it as one of the most active M-N-C catalysts reported to date. This work presents a new avenue for boosting ORR activity by edge manipulation of FeN 4 sites.
29 ENERGY PLANNING, POLICY, AND ECONOMY↗
Optical Absorption-Based In Situ Characterization of Halide Perovskites
Halide perovskites have emerged as materials for high-performance optoelectronic devices. Often, progress made to date in terms of higher efficiency and stability is based on increasing material complexity, i.e., formation of multicomponent halide perovskites with multiple cations and anions. In this review article, the use of in situ optical methods, namely, photoluminescence (PL) and UV-vis, that provide access to the relevant time and length scales to ascertain chemistry–property relationships by monitoring evolving properties is discussed. Additionally, because halide perovskites are electron/ion conductors and prone to solid-state ion transport under various external stimuli, application of these optical methods in the context of ionic movement is described to reveal mechanistic insights. In conclusion, examples of using in situ PL and UV-vis to study degradation and phase transitions are reviewed to demonstrate the wealth of information that can be obtained regarding many different aspects of ongoing research activities in the field of halide perovskites.
36 MATERIALS SCIENCE↗
Enabling Deformable and Stretchable Batteries
Abstract Deformable energy storage devices are needed to power next‐generation wearable electronics that interface intimately with human skin. Currently, deformable energy storage devices demonstrate poor performance compared to their rigid lithium‐ion counterparts, forcing wearable manufacturers to design their devices around bulky battery compartments. However, technological advances to create deformable batteries at the component and device level have yielded continuous improvement in stretchable batteries over the last five years. In this Essay, the major strategies at the component and device level that have been successfully employed to create stretchable batteries are reviewed. The outstanding challenges facing deformable energy storage are also discussed, namely, energy density, packaging, delamination, device integration, and manufacturing. This Essay will give researchers who are interested in contributing to the development of deformable batteries a cursory understanding of the most successful strategies to date, and provide insights into the most important directions to pursue in the future.
Mackanic, David G.↗
A Fluorination Method for Improving Cation-Disordered Rocksalt Cathode Performance
In Li-rich cation-disordered rocksalt oxide cathodes (DRX), partial fluorine substitution in the oxygen anion sublattice can increase the capacity contribution from transition-metal (TM) redox while reducing that from the less reversible oxygen redox. To date, limited fluorination substitution has been achieved by introducing LiF precursor during the solid-state synthesis. To take full advantage of the fluorination effect, however, a higher F content is desired. In the present study, the successful use of a fluorinated polymeric precursor is reported to increase the F solubility in DRX and the incorporation of F content up to 10–12.5 at% into the rocksalt lattice of a model Li-Mn-Nb-O (LMNO) system, largely exceeding the 7.5 at% limit achieved with LiF synthesis. Higher F content in the fluorinated-DRX (F-DRX) significantly improves electrochemical performance, with a reversible discharge capacity of ≈255 mAh g –1 achieved at 10 at% of F substitution. After 30 cycles, up to a 40% increase in capacity retention is achieved through the fluorination. Overall, the study demonstrates the feasibility of using a new and effective fluorination process to synthesize advanced DRX cathode materials.
25 ENERGY STORAGE↗
Achieving High‐Performance and 2000 h Stability in Anion Exchange Membrane Fuel Cells by Manipulating Ionomer Properties and Electrode Optimization
The primary function of the ionomers that are incorporated into fuel cell electrode catalyst layers is to provide pathways for ion transport between the catalyst active sites and the electrolyte. This is influenced by many variables, including the ion-exchange capacity, water uptake, and molecular weight. In anion exchange membrane fuel cells (AEMFCs), controlling ionomer water uptake is particularly important and tailoring this property in each electrode is an important consideration when looking to maximize cell performance. In this study, three poly(norbornene) tetrablock copolymer ionomers with a range of physical properties are synthesized and incorporated into AEMFC anode and cathode electrodes. Systematic electrode engineering with these ionomers allows the peak power density to be increased by 100% (1.6 W cm -2 → 3.2 W cm -2 ) and the current density at 0.2 V to be increased by 59% (5.9 A cm -2 → 9.4 A cm -2 ). Moreover, the top-performing electrode configuration is tested in an operating AEMFC at the US Department of Energy defined current density of 600 mA cm -2 for 2000 h, showing a record-low voltage decay rate of 15.36 µV h -1 – only 3.65% –a over 2000 h. Here, this work sets a new bar for AEMFCs, reporting the best combination of performance and durability of any AEMFC to date.
08 HYDROGEN↗
Device Performance of Emerging Photovoltaic Materials (Version 1)
Abstract Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye‐sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi‐junction PVs. Nevertheless, it can be very time consuming to find or develop an up‐to‐date overview of the state‐of‐the‐art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state‐of‐the‐art emerging PVs.
36 MATERIALS SCIENCE↗
Revisiting Discharge Mechanism of CF x as a High Energy Density Cathode Material for Lithium Primary Battery
Lithium/fluorinated graphite (Li/CFx) primary batteries show great promise for applications in a wide range of energy storage systems due to their high energy density (>2100 Wh kg –1 ) and low self-discharge rate (<0.5% per year at 25 °C). While the electrochemical performance of the CF x cathode is indeed promising, the discharge reaction mechanism is not thoroughly understood to date. In this article, a multiscale investigation of the CF x discharge mechanism is performed using a novel cathode structure to minimize the carbon and fluorine additives for precise cathode characterizations. Titration gas chromatography, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, cross-sectional focused ion beam, high-resolution transmission electron microscopy, and scanning transmission electron microscopy with electron energy loss spectroscopy are utilized to investigate this system. Results show no metallic lithium deposition or intercalation during the discharge reaction. Crystalline lithium fluoride particles uniformly distributed with <10 nm sizes into the CF x layers, and carbon with lower sp2 content similar to the hard-carbon structure are the products during discharge. This article deepens the understanding of CF x as a high energy density cathode material and highlights the need for future investigations on primary battery materials to advance performance.
25 ENERGY STORAGE↗
High‐Performance and Durable Fuel Cells using Co/Sr‐Free Fluorite‐Based Mixed Conducting (Pr,Ce)O 2‐δ Cathode
Abstract A major challenge to overcome in demonstrating solid oxide fuel cells (SOFCs) to be suitable as efficient and environmentally friendly energy conversion devices capable of addressing pressing clean energy and environmental needs is to surmount chemical and thermo‐mechanical instabilities in their operational phase. To date, perovskite‐based mixed conducting cathodes, which include inherent Co and Sr elements for enhanced reactivity and conductivity, have been intensively studied. These Co/Sr‐based oxides, however, exhibit severe thermochemical expansion and suffer from Sr surface segregation, ultimately degrading the electrode performance. Here, high‐performance and durable SOFCs are demonstrated by employing a Co/Sr‐free fluorite‐based mixed conducting (Pr,Ce)O 2‐δ (PCO) cathode eminently compatible with fluorite‐based solid electrolytes. The nanocolumnar PCO electrode developed in this study provides not only a remarkable low level of electrode resistance (e.g., ≈0.05 Ω cm 2 at 600 °C) but also exceptional long‐term stability (e.g., a degradation rate 15 times slower compared to the state‐of‐the‐art La 0.6 Sr 0.4 CoO 3‐δ perovskite). The competitive peak power densities of an anode‐supported single cell with the PCO cathode are also successively achieved, recording a value of 0.92 W cm −2 at 600 °C. These findings herald the development of new Co/Sr‐free electrodes for SOFCs at intermediate temperatures.
30 DIRECT ENERGY CONVERSION↗
Unexpected Hole Doping of Graphene by Osmium Adatoms
Abstract The electronic transport of monolayer graphene devices is studied before and after in situ deposition of a sub‐monolayer coating of osmium adatoms. Unexpectedly, and unlike all other metallic adatoms studied to date, osmium adatoms shift the charge neutrality point to more positive gate voltages. This indicates that osmium adatoms act as electron acceptors and thus leave the graphene hole‐doped. Analysis of transport data suggest that Os adatoms behave as charged impurity scatterers, albeit with a surprisingly low charge‐doping efficiency. The charge neutrality point of graphene is found to vary non‐monotonically with gate voltage as the sample is warmed to room temperature, suggesting that osmium diffuses on the surface but is not completely removed.
Elias, Jamie A.↗
Water Oxidation by Ruthenium Complexes Incorporating Multifunctional Bipyridyl Diphosphonate Ligands
Abstract We describe herein the synthesis and characterization of ruthenium complexes with multifunctional bipyridyl diphosphonate ligands as well as initial water oxidation studies. In these complexes, the phosphonate groups provide redox‐potential leveling through charge compensation and σ donation to allow facile access to high oxidation states. These complexes display unique pH‐dependent electrochemistry associated with deprotonation of the phosphonic acid groups. The position of these groups allows them to shuttle protons in and out of the catalytic site and reduce activation barriers. A mechanism for water oxidation by these catalysts is proposed on the basis of experimental results and DFT calculations. The unprecedented attack of water at a neutral six‐coordinate [Ru IV ] center to yield an anionic seven‐coordinate [Ru IV −OH] − intermediate is one of the key steps of a single‐site mechanism in which all species are anionic or neutral. These complexes are among the fastest single‐site catalysts reported to date.
Xie, Yan↗
Discovery of a Highly Selective Glycogen Synthase Kinase‐3 Inhibitor (PF‐04802367) That Modulates Tau Phosphorylation in the Brain: Translation for PET Neuroimaging
Abstract Glycogen synthase kinase‐3 (GSK‐3) regulates multiple cellular processes in diabetes, oncology, and neurology. N ‐(3‐(1H‐1,2,4‐triazol‐1‐yl)propyl)‐5‐(3‐chloro‐4‐methoxyphenyl)oxazole‐4‐carboxamide (PF‐04802367 or PF‐367) has been identified as a highly potent inhibitor, which is among the most selective antagonists of GSK‐3 to date. Its efficacy was demonstrated in modulation of tau phosphorylation in vitro and in vivo. Whereas the kinetics of PF‐367 binding in brain tissues are too fast for an effective therapeutic agent, the pharmacokinetic profile of PF‐367 is ideal for discovery of radiopharmaceuticals for GSK‐3 in the central nervous system. A 11 C‐isotopologue of PF‐367 was synthesized and preliminary PET imaging studies in non‐human primates confirmed that we have overcome the two major obstacles for imaging GSK‐3, namely, reasonable brain permeability and displaceable binding.
Liang, Steven H.↗
Single‐Domain Ferromagnet of Noncentrosymmetric Uniaxial Magnetic Ions and Magnetoelectric Interaction
Abstract The feasibility of a single‐domain ferromagnet based on uniaxial magnetic ions was examined. For a noncentrosymmetric uniaxial magnetic ion of magnetic moment μ at a site of local electric dipole moment p , it is unknown to date whether μ prefers to be parallel or antiparallel to μ . The nature of this magnetoelectric interaction was probed in terms of analogical reasoning based on the Rashba effect and density functional theory (DFT) calculations. We show that μ and p prefer an antiparallel arrangement, predict that Fe‐doped CaZnOS is a single‐domain ferromagnet like a bar magnet, and find the probable cause for the ferromagnetism and weak magnetization hysteresis in Fe‐doped hexagonal ZnO and ZnS at very low dopant concentrations.
Koo, Hyun‐Joo↗
Chemical Origin of the Stability Difference between Cu(I)- and Ag(I)-Based Halide Double Perovskites
Recently, Cu(I)- and Ag(I)-based halide double perovskites have been proposed as promising candidates for overcoming the toxicity and instability issues inherent within the emerging Pb-based halide perovskite absorbers. However, up to date, only Ag(I)-based halide double perovskites have been experimentally synthesized; there are no reports on successful synthesis of Cu(I)-based analogues. In this study, we show that, owing to the much higher energy level for the Cu 3d 10 orbital than for the Ag 4d 10 orbital, Cu(I) atoms energetically favor 4-fold coordination, forming [CuX 4 ] tetrahedra (X = halogen), but not 6-fold coordination as required for [CuX 6 ] octahedra. In contrast, Ag(I) atoms can have both 6- and 4-fold coordination’s. Our density functional theory calculations reveal that the synthesis of Cu(I) halide double perovskites may instead lead to products containing [CuX 4 ] tetrahedra, as confirmed by our material synthesis efforts.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗