SEARCH · Engineering Papers
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.
Bimetallic cooperativity is demonstrated with a Co/Zr complex featuring both nucleophilic Zr( iv ) oxo and redox active Co sites.
A review of micro to macro-scale activities, challenges and perspectives for redox flow battery modelling is presented.
The state-of-the-art advances of non-aqueous organic redox flow batteries for grid-scale energy storage were evaluated and summarized.
Ni-rich layered cathode materials are at the forefront to be deployed in high energy density Li-ion batteries for the automotive market. However, the intrinsic poor structural and interfacial stability during overcharging could trigger violent thermal failure, which severely limits their wide application. To protect the Ni-rich cathode from overcharging, we firstly report a redox-active cation, thioether-substituted diaminocyclopropenium, as an electrolyte additive to limit the cell voltage within the safe value during overcharging. The organic cation demonstrates a record-breaking electrochemical reversibility at ~4.55 V versus Li + /Li and solubility (0.5 M) in carbonate-based electrolyte. The protection capability of the additive was explored in two cell chemistries: a LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell and a LiNi 0.8 Co 0.15 Al 0.05 O 2 /silicon–graphene cell with areal capacities of ~2.2 mA h cm -2 and ~3 mA h cm -2 , respectively. With 0.2 M addition, the LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell survived 54 cycles at 0.2C with 100% overcharge. Moreover, the cell can carry an utmost 4.4 mA cm -2 (2C) with 100% overcharge and a maximum capacity of 7540% SOC at 0.2C.
Tetrapyrrole macrocycles serve a multitude of roles in biological systems, including oxygen transport by heme and light harvesting and charge separation by chlorophylls and bacteriochlorophylls. Synthetic tetrapyrroles are utilized in diverse applications ranging from solar-energy conversion to photomedicine. Nevertheless, students beginning tetrapyrrole research, as well as established practitioners, are often puzzled when comparing properties of related tetrapyrroles. Questions arise as to why optical spectra of two tetrapyrroles often shift in wavelength/energy in a direction opposite to that predicted by common chemical intuition based on the size of a π-electron system. Gouterman's four-orbital model provides a framework for understanding these optical properties. Similarly, it can be puzzling as to why the oxidation potentials differ significantly when comparing two related tetrapyrroles, yet the reduction potentials change very little or shift in the opposite direction. In order to understand these redox properties, it must be recognized that structural/electronic alterations affect the four frontier molecular orbitals (HOMO, LUMO, HOMO-1 and LUMO+1) unequally and in many cases the LUMO+1, and not the LUMO, may track the HOMO in energy. This perspective presents a fundamental framework concerning tetrapyrrole electronic properties that should provide a foundation for rational molecular design in tetrapyrrole science.
Electrochemical impedance measurements of NiO and α-Fe 2 O 3 films immersed in redox-inactive organic media depend on both film morphology and electronic structure.
The effect of Pd loading on the redox characteristics of a ceria support was examined using in situ Pd K-edge XAS, Ce L 3 -edge XAS and in situ X-ray diffraction techniques. Analysis of the data obtained from these techniques indicates that the onset temperature for the partial reduction of Ce(IV) to Ce(III), by exposure to H 2 , varies inversely with the loading of Pd. Whilst the onset and completion temperatures of the reduction of Ce(IV) to Ce(III) are different, both samples yield the same maximal fraction of Ce(III) formation independent of Pd loading. Furthermore, the partial reduction of Ce is found to be concurrent with the reduction of PdO and demonstrated that the presence of metallic Pd is necessary for the reduction of the CeO 2 support. Upon passivation by room temperature oxidation, a full oxidation of the reduced ceria support was observed. However, only a mild surface oxidation of Pd was identified. The mild passivation of the Pd is found to lead to a highly reactive sample upon a second reduction by H 2 . The onset of the reduction of Pd and Ce has been demonstrated to be independent of the Pd loading after a mild passivation with both samples exhibiting near room temperature reduction in the presence of H 2 .
The photo-response of the redox-active metal–organic framework has been systematically tuned by incorporating plasmonic Ag nanoparticles and tetrathiafulvalene radicals, resulting in efficient near-infrared photothermal conversion materials.
Redox-switchable carboranes electrochemically capture and release UO 2 2+ selectively from mixed metal aqueous solutions, mimicking in part spent nuclear fuel.
A unique copolymer combines ion-exchange groups and redox-active ferrocene groups to enable effective adsorption of rare earth element ions and fully electrochemically-controlled regeneration, without the use of hazardous chemicals.
Herein we describe a designed protein building block whose self-assembly behaviour is dually gated by the redox state of disulphide bonds and the identity of exogenous metal ions.
A microbial-based system for redox flow battery (RBF) electrolyte regeneration system to address failure mechanisms in RBF devices.
IR spectroscopy of a carbon–deuterium vibrational probe reveals that binding of the redox partner induces significant strengthening of the Cu-Cys89 bond in plastocyanin.
An ultra-stable reference electrode with novel design has been developed for scaled all-vanadium redox flow batteries, which demonstrates high accuracy and long-term stability over 500 charge–discharge cycles.
This report describes the first gram-scale synthesis of a nanocage that can host fullerenes (C 60 and C 70 ). The redox properties of the fullerenes are preserved in this host, enabling characterization of complexes with fulleride anions and dianions.
The use of sulfone-based redox mediators in electrocatalytic CO 2 reduction by Cr-centered complexes enhances the turnover frequencies at lower overpotentials via inner-sphere electron transfer and pancake bonding.
We highlight the status of, and propose future approaches for, rheological, electrochemical, and spectroscopic characterization of concentrated redoxmer electrolytes for energy storage, with an emphasis on nonaqueous redox flow batteries.
A novel simplicity-biased molecular structure generation method and Bayesian optimization based active learning have been used to discover a new class of heterocyclic molecules for organic non-aqueous redox flow batteries.