High pressure driven structural and electrochemical modifications in layered lithium transition metal intercalation oxides
Abstract not provided
Fell, C. R.↗
SEARCH · Engineering Papers
Results for “MODIFICATIONS”
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.
Co–salen complexes as catalysts for the asymmetric Henry reaction – reversed enantioselectivity through simple ligand modification
The asymmetric Henry reaction is an efficient method for the synthesis of enantioenriched nitro alcohols. Here, we investigated the catalytic activity and enantioselectivity of derivatives of Co–salen [salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamine] in this reaction. Tetrahydro-salen (salan) complexes displayed a reversed enantioselectivity compared to their Schiff-base counterparts. Oligomeric Co–salen catalysts showed a higher activity than their small molecule analogues, indicating a bimetallic pathway.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Deliberate modification of the solid electrolyte interphase (SEI) during lithiation of magnetite, Fe 3 O 4 : impact on electrochemistry
Here, magnetite is a conversion anode material displaying multi-electron transfer during lithiation and delithiation. The solid electrolyte interphase (SEI) on magnetite, Fe 3 O 4 , electrodes for lithium ion batteries was deliberately modified through the use of fluoroethylene carbonate (FEC) electrolyte additive, improving both capacity retention and rate capability. Analysis showed reduction of FEC at higher voltage compared to non-fluorinated solvents with formation of a modified lithium flouride containing electrode surface.
25 ENERGY STORAGE↗
Tuning the properties of metal–organic framework nodes as supports of single-site iridium catalysts: node modification by atomic layer deposition of aluminium
The metal–organic framework NU-1000, with Zr 6 -oxo, hydroxo, and aqua nodes, was modified by incorporation of hydroxylated Al( iii ) ions by ALD-like chemistry with [Al(CH 3 ) 2 (iso-propoxide)] 2 followed by steam (ALD = atomic layer deposition). Al ions were installed to the extent of approximately 7 per node. Single-site iridium diethylene complexes were anchored to the nodes of the modified and unmodified MOFs by reaction with Ir(C 2 H 4 ) 2 (acac) (acac = acetylacetonate) and converted to Ir(CO) 2 complexes by treatment with CO. Infrared spectra of these supported complexes show that incorporation of Al weakened the electron donor tendency of the MOF. Correspondingly, the catalytic activity of the initial supported iridium complexes for ethylene hydrogenation increased, as did the selectivity for ethylene dimerization. The results of density functional theory calculations with a simplified model of the nodes incorporating Al( iii ) ions are in qualitative agreement with some catalyst performance data.
catalysis (heterogeneous), materials and chemistry↗
Interface engineering through electron transport layer modification for high efficiency organic solar cells
Schematic of PTB7-Th:PCBM OSCs in an inverted geometry with ZnO, ZnO/Ba(OH) 2 and ZnO:Ba(OH) 2 nanocomposites as ETLs.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Revealing long- and short-range structural modifications within phosphorus-treated HZSM-5 zeolites by atom probe tomography, nuclear magnetic resonance and powder X-ray diffraction
In this study, the average and the local structure of phosphorus-treated HZSM-5 zeolites were investigated by means of atom probe tomography, powder X-ray diffraction (at ambient and cryogenic temperatures) and 1 H, 29 Si, 27 Al, and 31 P magic angle spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy. Phosphatation to yield a product with P/Al ≤ 1 followed by thermal treatment leads to breaking of the Si–OH–Al bridging groups, and subsequent partial dealumination of the zeolite framework, as shown by the contraction of the orthorhombic unit-cell volume and by the loss of tetrahedral framework Al, as observed in the 27 Al Multiple Quantum (MQ) MAS NMR spectrum. Most of the framework Al is present in an electronic environment distorted by the presence of phosphorus and appears not to be involved in classic Si–OH–Al Brønsted acid sites. The 31 P MAS NMR signals indicate that phosphorus interacts with the zeolitic framework to locally form silico-aluminophosphate (SAPO) domains and the presence of a new kind of acidic site was confirmed by the resonance at ~8.6 ppm in the 1 H MAS NMR spectra, attributed to P–OH groups. Increasing the phosphorus loading (P/Al >> 1) promotes further dealumination of the framework and cross-dehydroxylation between P–OH and Si–OH species, leading to the formation of a crystalline silicon orthophosphate phase. With decreasing Al content, the monoclinic HZSM-5 structure becomes preferred, especially at 85 K where the strain relaxation is higher. Nevertheless, the presence of a higher amount of silicophosphate impurities hinders the low-temperature strain release of the framework, indicating that some of these species are localized in the zeolite pores and contribute to the strain build up.
36 MATERIALS SCIENCE↗
Unexpected compositional and structural modification of CoPt 3 nanoparticles by extensive surface purification
We combined synchrotron small angle X-ray scattering, X-ray fluorescence and extended X-ray absorption fine structure spectroscopy to probe the structure of chemically synthesized CoPt 3 nanoparticles (NPs) after ligand removal via the commonly accepted solvent/nonsolvent approach. We showed that the improved catalytic activity of extensively purified NPs could not be explained only in terms of a “cleaner” surface. We found that extensive surface purification results in the substantial leaching of the Co atoms from the chemically synthesized CoPt 3 NPs transforming them into CoPt 3 /Pt core/shell structures with an unexpectedly thick (~0.5 nm) Pt shell. We indicated that the improved catalytic activity of extensively purified NPs in octyne hydrogenation reaction can be explained by the formation of CoPt 3 /Pt core/shell structures. Also, we demonstrated that drastic compositional and structural transformation of water transferred CoPt 3 NPs was rather a result of extensive removal of native ligands via a solvent/nonsolvent approach than leaching of cobalt atoms in aqueous media. We expect that these findings can be relevant to other transition metal based multicomponent NPs.
36 MATERIALS SCIENCE↗
Self-assembly of highly asymmetric, poly(ionic liquid)-rich diblock copolymers and the effects of simple structural modification on phase behaviour
A series of thermally processable, phase-separating diblock copolymers made via sequential ATRP of styrene and styrenic ionic liquid (IL) monomers with various alkyl imidazolium substituents were synthesized to cover a wide range of volume fractions, most notably those on the IL-rich side of the phase diagram. Small-angle X-ray scattering (SAXS) analysis was used to confirm melt-state (and glassy state) phase behavior in which all four classic equilibrium diblock copolymer morphologies – body-centered cubic spheres (S BCC ), hexagonally packed cylinders (Hex), lamellae (Lam), and notably, bicontinuous gyroid (Gyr) – were observed. These PS-PIL diblock copolymers were found to have a high degree of conformational asymmetry and/or electrostatic cohesion within the PIL block, highlighted by the shift of the Lam phase window with boundaries falling between f PIL = 0.31 and 0.55. Finally, variation of the alkyl group appeared to influence the strength of the Flory-like interaction parameter of the system, χ PS/PIL , such that simple substitution of methyl by n-butyl on the imidazolium IL substituent resulted in the emergence of the (notoriously segregation-sensitive) Gyr phase, superseding the persistent coexistence of Lam and Hex in the methyl-substituted imidazolium diblock copolymer phase diagram.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Modification of BiVO 4 /WO 3 composite photoelectrodes with Al 2 O 3 via chemical vapor deposition for highly efficient oxidative H 2 O 2 production from H 2 O
Efficient H 2 O 2 production on both the Al 2 O 3 /BiVO 4 /WO 3 photoanode and carbon cathode loaded with a biomass-derived cathode without external bias was demonstrated.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Promotion of oxygen reduction reaction on a double perovskite electrode by a water-induced surface modification
Highly efficient air electrodes are a key component of reversible fuel cells for energy storage and conversion; however, the development of efficient electrodes that are stable against water vapor remains a grand challenge. Here we report an air–electrode, composed of double perovskite material PrBa 0.8 Ca 0.2 Co 2 O 5+δ (PBCC) backbone coated with nanoparticles (NPs) of BaCoO 3-δ (BCO), that exhibits remarkable electrocatalytic activity for oxygen reduction reaction (ORR) while maintaining excellent tolerance to water vapor. When tested in a symmetrical cell exposed to wet air with 3 vol% H 2 O at 750 °C, the electrode shows an area specific resistance of ~0.03 Ω cm 2 in an extended period of time. The performance enhancement is attributed mainly to the electrocatalytic activity of the BCO NPs dispersed on the surface of the porous PBCC electrode. Moreover, in situ Raman spectroscopy is used to probe reaction intermediates (e.g., oxygen species) on electrode surfaces, as the electrochemical properties of the electrodes are characterized under the same conditions. The direct correlation between surface chemistry and electrochemical behavior of an electrode is vital to gaining insight into the mechanisms of the electrocatalytic processes in fuel cells and electrolysers.
25 ENERGY STORAGE↗
Divergent uranium- versus phosphorus-based reduction of Me 3 SiN 3 with steric modification of phosphido ligands
We describe an example of a two-electron metal- and ligand-based reduction of Me 3 SiN 3 using uranium( iv ) complexes with varying steric properties. With uranium-based reduction, a U( vi ) intermediate is isolated.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Enabling stable and high-rate cycling of a Ni-rich layered oxide cathode for lithium-ion batteries by modification with an artificial Li⁺-conducting cathode-electrolyte interphase
Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes are investigated to realize high energy density Li ion batteries for long life electric vehicle applications. However, capacity decay and thermal instability due to cathode-electrolyte interfacial degradation remain challenges that require sophisticated surface stabilization methods to address. Here, we propose a strategy, for the first time, to form an artificial Li + -conducting cathode-electrolyte interphase (ALCEI) on the NCM811 cathode surface using a nucleophilic reaction between polysulfides and vinylene carbonate (VC). Furthemore, the as-formed ALCEI layer simultaneously protects the NCM particles from electrolyte corrosion and facilitates Li + ion transport, thus enabling stable and high rate cycling of NCM811. As a result, the ALCEI-modified NCM811 cathode exhibits a high capacity (211.6 mA h g -1 at 0.1C), notable rate capability (134 mA h g -1 at 10C), and superior cycle stability (94.2% over 200 cycles at 1C). These results underscore the use of interfacial engineering in high voltage cathode material development and provide a feasible strategy for stabilizing Ni-rich cathode interfaces in practical Li ion battery applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Bandgap modification in 0D tellurium iodide perovskite derivatives via incorporation of polyiodide species
A family of zero dimensional tellurium( iv ) iodide perovskite derivatives, which demonstrate the presence of polyiodides (I 2 or I 3 − ) strongly affects the bandgap of these materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Metabolic Modification of Sphingobium lignivorans SYK-6 for Lignin Valorization Through the Discovery of an Unusual Transcriptional Repressor of Lignin-Derived Dimer Catabolism
Sphingobium lignivorans SYK-6 catabolizes guaiacylglycerol-..beta..-guaiacyl ether (GGE, a ..beta..-O-4-type dimer) and 1,2-diguaiacylpropane-1,3-diol (DGPD, a ..beta..-1-type dimer) derived from lignin. Recently, SLG_35860 containing TetR- and MarR-type transcriptional regulator motifs was suggested to be involved in the regulation of GGE and DGPD catabolism. Here we investigated the role of SLG_35860 in the transcriptional regulation of GGE and DGPD catabolism genes. SLG_35860 designated ligS repressed 11 genes involved in GGE and DGPD catabolism. LigS binds directly to specific sequences in the promoter region of each gene. The MarR domain was shown to be involved in these bindings; however, GGE, DGPD, and their metabolites did not function as effectors of LigS. We discovered unidentified compound(s) in the black liquor of oxygen-soda anthraquinone pulping of Japanese cedar that SYK-6 cannot metabolize and that acted as effector(s). Therefore, LigS constantly represses the transcription of the GGE and DGPD catabolism genes to low levels. Based on these findings, we examined the productivity of a polymer building block, 2-pyrone-4,6-dicarboxylic acid (PDC), from GGE, DGPD, and a GGE metabolite using an engineered ligS mutant. The rates of PDC production from each compound by this strain were 1.5-6.0 times higher than those of a PDC-producing strain carrying ligS.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Interface-driven enhancement of Nafion thin-film conductivity via controlled aminothiol modification
Interfacial design using strategically chosen linkers, like cysteamine, can effectively mitigate confinement effects in ionomer thin films and improve proton transport in targeted directions.
Acurio-Cerda, Karen [Department of Chemical and Bi↗
Chloride modification of vacuum-assisted blade-coated perovskite solar cells and mini-modules in ambient environment
Scalable deposition of perovskite thin films under ambient conditions remains a key challenge for the commercialization of perovskite photovoltaics, primarily due to the difficulty of controlling crystallization kinetics and suppressing non-radiative recombination during film formation. In this work, we present an effective strategy to modulate crystallization kinetics and non-radiative recombination in vacuum-quenched blade-coated perovskite films processed in air using chloride-based additives. By systematically comparing PbCl 2 and 3-chloropropylamine hydrochloride (Cl-PACl), we elucidate how different chloride incorporation pathways influence crystallization behavior and optoelectronic properties. In situ transmission and in situ photoluminescence measurements reveal that PbCl 2 acts as a transient additive that slows intermediate/perovskite phase formation while suppressing non-radiative recombination, leading to improved film quality. In contrast, Cl-PACl introduces additional trap states that deteriorate optoelectronic performance. As a result, PbCl 2 -modified perovskite solar cells achieve a champion power conversion efficiency (PCE) of 24.2% and remarkable operational stability, retaining over 90% of their initial performance after 800 hours of continuous illumination. Furthermore, we successfully scaled the process, fabricating a perovskite mini-module that delivered a champion efficiency of 18.0%. This study underscores the critical importance of coupling vacuum-assisted blade coating with transient additive engineering for achieving high-performance, stable, and scalable perovskite photovoltaics processed in ambient air.
14 SOLAR ENERGY↗