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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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Salt-Induced Liquid?Liquid Phase Separation and Interfacial Crystal Formation in Poly(N-isopropylacr
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Improving Solar Cell Performance Using Quantum Dot Triad Charge-Separation Engines
Here, we use kinetic modeling to explore the current–voltage, power–voltage, and power conversion efficiency characteristics of quantum dot dyads and triads as possible light absorption and charge separation engines in quantum dot, bulk heterojunction solar cells. The external and internal power conversion quantum efficiencies are significantly enhanced by introducing a third quantum dot between the donor and acceptor quantum dots. Given the constraint of comparable charge-recombination and charge-separation rates, open-circuit voltages for triads are predicted to be about 10%–17% larger than those for dyads, and short-circuit currents for triads are about 400% larger than those for dyads. These improvements in the efficiencies can be further enhanced by tuning the band-edge energy offset of the middle-position quantum dot from its neighbors. The band-edge energies of the middle quantum dot should be tuned so that they form a cascading band-edge energy alignment from the band-edge energies of the left CdTe QD to the right CdSe QD. To produce the most favorable solar cell performance, the middle quantum dot’s conduction (valence) band edge should be closer to the right quantum dot’s band edge when the charge recombination rates are low (high) and near the conduction (valence) band edge of the left quantum dot when the charge recombination rates are high (low). This analysis identifies prime strategies to design multi-QD assemblies for solar energy harvesting and conversion.
Synthesis and Characterization of Thiazolium-Based Room Temperature Ionic Liquids for Gas Separations
A series of novel thiazolium-bis(triflamide) based ionic liquids has been synthesized and characterized. Physicochemical properties of the ionic liquids such as thermal stability, phase transitions, and infrared spectra were analyzed and compared to the imidazolium-based congeners. Several unique classes of ancillary substitutions are examined with respect to impacts on overall structure, in addition to their carbon dioxide absorption properties in supported ionic-liquid membranes for gas separation.
A Superacid-Catalyzed Synthesis of Porous Membranes Based on Triazine Frameworks for CO2 Separation
A general strategy for the synthesis of porous, fluorescent, triazine-framework-based membranes with intrinsic porosity through an aromatic nitrile trimerization reaction is presented. The essence of this strategy lies in the use of a superacid to catalyze the cross-linking reaction efficiently at a low temperature, allowing porous polymer membrane architectures to be facilely derived. With fiinctionalized triazine units, the membrane exhibits an increased selectivity for membrane separation of CO2 over N-2. The good ideal CO2/N-2 selectivity of 29 +/- 2 was achieved with a CO2 permeability of 518 +/- 25 barrer. Through this general synthesis protocol, a new class of porous polymer membranes with tunable functionalities and porosities can be derived, significantly expanding the currently limited library of polymers with intrinsic microporosity for synthesizing functional membranes in separation, catalysis, and energy storage/conversion.
Photoinduced Dynamics of Charge Separation: From Photosynthesis to Polymer–Fullerene Bulk Heterojunctions
Understanding charge separation and charge transport is crucial for improving the efficiency of organic solar cells. Their active media are based on organic molecules and polymers, serving as both light-absorbing and transport layers. The charge-transfer (CT) states play an important role, being intermediate for free carrier generation and charge recombination. Here, we use light-induced electron paramagnetic resonance spectroscopy to study the CT dynamics in blends of the polymers P3HT, PCDTBT, and PTB7 with the fullerene derivative C-60-PCBM. Time-resolved EPR measurements show strong spin-polarization patterns for all polymer-fullerene blends, confirming predominant generation of singlet CT states and partial orientation ordering near the donor-acceptor interface. These observations allow a comparison with charge separation processes in molecular donor-acceptor systems and in natural and artificial photosynthetic assemblies, and thus the elucidation of the initial steps of sequential CT in organic photovoltaic materials.
Large-Scale Computational Screening of Zeolites for Ethane/Ethene Separation
Large-scale computational screening of thirty thousand zeolite structures was conducted to find optimal structures for seperation of ethane/ethene mixtures. Efficient grand canonical Monte Carlo (GCMC) simulations were performed with graphics processing units (GPUs) to obtain pure component adsorption isotherms for both ethane and ethene. We have utilized the ideal adsorbed solution theory (LAST) to obtain the mixture isotherms, which were used to evaluate the performance of each zeolite structure based on its working capacity and selectivity. In our analysis, we have determined that specific arrangements of zeolite framework atoms create sites for the preferential adsorption of ethane over ethene. The majority of optimum separation materials can be identified by utilizing this knowledge and screening structures for the presence of this feature will enable the efficient selection of promising candidate materials for ethane/ethene separation prior to performing molecular simulations.
Solvent-mediated charge separation drives alternative hydrogenation path of furanics in liquid water
Compared to the vapour phase, liquid-phase heterogeneous catalysis provides additional degrees of freedom for reaction engineering, but the multifaceted solvent effects complicate analysis of the reaction mechanism. Here, using furfural as an example, we reveal the important role of water-mediated protonation in a typical hydrogenation reaction over a supported Pd catalyst. Depending on the solvent, we have observed different reaction orders with respect to the partial pressure of H 2 , as well as distinct selectivity towards hydrogenation of the conjugated C=O and C=C double bonds. Free energy calculations show that H 2 O participates directly in the kinetically relevant reaction step and provides an additional channel for hydrogenation of the aldehyde group, in which hydrogen bypasses the direct surface reaction via a hydrogen-bonded water network. In conclusion, this solution-mediated reaction pathway shows the potential role of the solvent for tuning the selectivity of metal-catalysed hydrogenation when charge separation on the metal surface is feasible.
Stability of polymeric separators in lithium metal batteries in a low voltage environment
Separators can largely affect the coulombic efficiency and cycling stability of lithium metal anode, especially when using the LiPF 6 electrolyte.
A molecular basis to rare earth separations for recycling: tuning the TriNOx ligand properties for improved performance
A methoxy-substituted tripodal hydroxylamine ligand, H 3 TriNOx OMe , was synthesized and coordinated to rare earth cations for separation purposes.
Non-phase-separated 2D B–C–N alloys via molecule-like carbon doping in 2D BN: atomic structures and optoelectronic properties
A new way to overcome the phase-separation problem to fabricate 2D B–C–N via molecule-like carbon doping in 2D BN.
One-of-a-kind: a microporous metal–organic framework capable of adsorptive separation of linear, mono- and di-branched alkane isomers via temperature- and adsorbate-dependent molecular sieving
Clean separation of linear, monobranched, and dibranched alkanes is achieved using a flexible, microporous metal–organic framework (MOF).
Production of high-yield short-chain oligomers from cellulose via selective hydrolysis in molten salt hydrates and separation
Stepwise process of cellulose being hydrolyzed into oligomers in MSH followed by product separation.
Heterometal incorporation in NH2-MIL-125(Ti) and its participation in the photoinduced charge-separated excited state
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Facile one-pot synthesis of PdM (M = Ag, Ni, Cu, Y) nanowires for use in mixed matrix membranes for efficient hydrogen separation
A general synthesis method is demonstrated for producing PdM (M= Ag, Cu, Ni, and Y) nanowire networks. As a prototypical application, these nanowires are incorporated into polybenzimidazole to create mixed matrix membranes for H 2 /CO 2 separation.
Cost and energy efficient cyclic separation of 5-hydroxymethyl furfural from an aqueous solution
Selective separation of HMF from the aqueous phase and integration with downstream reactions via a two-stage adsorption and desorption scheme.
Separation of short-chain glucan oligomers from molten salt hydrate and hydrolysis to glucose
Glucan oligomers obtained from cellulose hydrolysis in molten salt hydrate can be separated using anti-solvent precipitation with a high efficiency.
Probing ultrafast charge separation at organic donor/acceptor interfaces by a femtosecond electric field meter
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