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585 results on '"Shkrob, Ilya A."'

153. Efficient, rapid photooxidation of chemisorbed polyhydroxyl alcohols and carbohydrates by TiO2 nanoparticles in an aqueous solution

Author

Shkrob, Ilya A., Sauer, Myran C., Jr., and Gosztola, David

Subjects
Photochemistry -- Analysis, Electron-electron interactions -- Analysis, Titanium compounds -- Chemical properties, Titanium compounds -- Research, Chemicals, plastics and rubber industries
Abstract

Electron dynamics in aqueous anatase nanoparticles is studied in the presence of hole scavengers like chemisorbed polyols and carbohydrates. It is concluded that scavenging efficiency rapidly increases with the number of anchoring hydroxyl groups.

Published
2004

154. Hole scavenging and photo-stimulated recombination of electron-hole pairs in aqueous TiO2 nanoparticles

Author

Shkrob, Ilya A. and Sauer, Myran C., Jr.

Subjects
Photochemistry -- Analysis, Titanium -- Thermal properties, Titanium -- Research, Electron-positron interactions -- Analysis, Chemicals, plastics and rubber industries
Abstract

The rapid photobleaching caused by 532 and 1064 nm laser photoexcitation of trapped electrons generated by 355 nm photolysis of aqueous titania nanoparticles is studied. It is stated that this photobleaching is caused by rapid recombination of the resulting free electron and a trapped hole.

Published
2004

155. Ultrafast studies on the photophysics of matrix-isolated radical cations of polycyclic aromatic hydrocarbons

Author

Liang Zhao, An Dong Liu, Rui Lian, Trifunac, Alexander D., Shkrob, Ilya A., Crowell, Robert A., Pommeret, Stanislas, and Chronister, Eric L.

Subjects
Radicals (Chemistry) -- Research, Boric acid -- Research, Boric acid -- Optical properties, Polycyclic aromatic hydrocarbons -- Research, Polycyclic aromatic hydrocarbons -- Optical properties, Chemistry, Physical and theoretical -- Research, Chemicals, plastics and rubber industries
Abstract

Femtosecond and picosecond transient grating spectroscopy is used to study ultrafast relaxation dynamics for photoexcited PAH cations isolated in boric acid glass. No temperature dependence or isotope effect was observed for the fast component, whereas the slow component exhibits both the H/D isotope effect (1.1-1.3) and a strong temperature dependence (15 to 300 K).

Published
2004

157. Electron localization in solid acetonitrile

Author

Shkrob, Ilya A., Takeda, Keiji, and Williams, Ffrancon

Subjects
Anions -- Optical properties, Anions -- Research, Acetonitrile -- Optical properties, Acetonitrile -- Research, Solid state chemistry, Chemicals, plastics and rubber industries
Abstract

The use of EPR, optical spectroscopy and ab initio calculations, it is demonstrated that electron attachment to nitrile molecules causes bending of their CCN fragments to ca. 130 degrees centigrade. In the resulting radical anions, the NC-C bond is 6-8% longer than in the parent molecules, which accounts for the ease of C-C fragmentation of the radical anion upon photoexcitation.

Published
2002

158. General Impossibility to “Prescribe” Diffusion for a Geminate Pair in a Central Force Field and Peculiarities of Geminate Dynamics in Ionic Liquids

Author

Shkrob, Ilya A.

Abstract

Given the difficulty of obtaining analytical solutions for the diffusion of interacting geminate pairs of (ion) radicals in liquids, it is common, following the original treatment of Mozumder, to “prescribe” this diffusion. A demonstration is given that such a prescription is impossible for any interaction potential other than the Coulomb potential. This demonstration suggests the inadequacy of this common approach to modeling geminate pair and spur dynamics in the largest emerging class of organic solvents: room-temperature ionic liquids.

Published
2024
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161. The lightest organic radical cation for charge storage in redox flow batteries

Author

Huang, Jinhua, primary, Pan, Baofei, additional, Duan, Wentao, additional, Wei, Xiaoliang, additional, Assary, Rajeev S., additional, Su, Liang, additional, Brushett, Fikile R., additional, Cheng, Lei, additional, Liao, Chen, additional, Ferrandon, Magali S., additional, Wang, Wei, additional, Zhang, Zhengcheng, additional, Burrell, Anthony K., additional, Curtiss, Larry A., additional, Shkrob, Ilya A., additional, Moore, Jeffrey S., additional, and Zhang, Lu, additional

Published
2016
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173. Improved performance through tight coupling of redox cycles of sulfur and 2,6-polyanthraquinone in lithium–sulfur batteries.

Author

Connell, Justin G., Lau, Ka-Cheong, Shkrob, Ilya A., Zhang, Lu, Zhang, Zhengcheng, Liao, Chen, Dietz Rago, Nancy L., Hu, Bin, and Phelan, Daniel

Abstract

Lithium–sulfur (Li–S) batteries offer high theoretical capacity and energy density; however, complex nanoengineered cathodes have been required to suppress the unwanted polysulfide shuttling. The textural complexity of such electrodes hinders detailed understanding of their function, impeding the development of new materials. In this report, the redox-active polymer 2,6-polyanthraquinone (PAQ) was incorporated into the cathode. The presence of this polymer improves capacity retention in galvanostatic cycling and inhibits Li corrosion and S deposition. We show that redox reactions of this polymer are strongly coupled to the S redox cycle and hypothesize that the observed improvements in the performance originate from the electrocatalytic inhibition of polysulfide shuttling in this system. [ABSTRACT FROM AUTHOR]

Published
2017
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174. ChemicalWeathering of Layered Ni-Rich Oxide Electrode Materials: Evidence for Cation Exchange.

Author

Shkrob, Ilya A., Gilbert, James A., Phillips, Patrick J., Klie, Robert, Haasch, Richard T., Bareño, Javier, and Abraham, Daniel P.

Subjects
LITHIUM-ion batteries, OXIDE electrodes
Abstract

Lithiated ternary oxides containing nickel, cobalt, and manganese are intercalation compounds that are used as positive electrodes in high-energy lithium-ion batteries. These oxides undergo changes, when they are stored in humid air or exposed to moisture, that adversely affect their electrochemical performance. There is a newurgency to better understanding of these "weathering" mechanisms as manufacturing moves toward a more environmentally benign aqueous processing of the positive electrode. Delithiation of the oxide and the formation of lithium salts (such as hydroxides and carbonates) coating the surface, are known to occur during moisture exposure. The redox reactions which follow this delithiation are believed to trigger all the other transformations. In this article we suggest another possibility: namely, the proton - lithium exchange. We argue that this hypothesis provides a simple, comprehensive rationale for our observations, which include contraction of the c-axis (unit cell) lattice parameter, rock salt phase formation in the subsurface regions, presence of amorphous surface films, and the partial recovery of oxide capacity during electrochemical relithiation. The detrimental effects of water exposure need to be mitigated before aqueous processing of the positive electrode can find widespread adoption during cell manufacturing. [ABSTRACT FROM AUTHOR]

Published
2017
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175. Electron Photodetachment from Aqueous Anions. II. Ionic Strength Effect on Geminate Recombination Dynamics and Quantum Yield for Hydrated Electron

Author

Sauer, Myran C., Shkrob, Ilya A., Lian, Rui, Crowell, Robert A., Bartels, David M., and Bradforth, Stephen E.

Subjects
Chemical Physics (physics.chem-ph), Physics - Chemical Physics, FOS: Physical sciences, Optics (physics.optics), Physics - Optics
Abstract

In concentrated solutions of NaClO4 and Na2SO4, the quantum yield for free electron generated by detachment from photoexcited anions (such as I-, OH-, ClO^4-, and [SO3]^2-) linearly decreases by 6-12% per 1 M ionic strength. In 9 M sodium perchlorate solution, this quantum yield decreases by roughly an order of magnitude. Ultrafast kinetic studies of 200 nm photon induced electron detachment from Br-, HO- and [SO3]^2- suggest that the prompt yield of thermalized electron does not change in these solutions; rather, the ionic strength effect originates in more efficient recombination of geminate pairs. Within the framework of the recently proposed mean force potential (MFP) model of charge separation dynamics in such photosystems, the observed changes are interpreted as an increase in the short-range attractive potential between the geminate partners. Association of sodium cation(s) with the electron and the parent anion is suggested as the most likely cause for the observed modification of the MFP. Electron thermalization kinetics suggest that the cation associated with the parent anion (by ion pairing and/or ionic atmosphere interaction) is passed to the detached electron in the course of the photoreaction. The precise atomic-level mechanism for the ionic strength effect is presently unclear; any further advance is likely to require the development of an adequate quantum molecular dynamics model., 40 pages, 10 figures + supplement 2 pages, 9 figures; will be submitted, in a modified form, to J. Phys. Chem A

Published
2004

179. Aqueous Complexes for Efficient Size-based Separation of Americium from Curium

Author

Jensen, Mark P., primary, Chiarizia, Renato, additional, Shkrob, Ilya A., additional, Ulicki, Joseph S., additional, Spindler, Brian D., additional, Murphy, Daniel J., additional, Hossain, Mahmun, additional, Roca-Sabio, Adrián, additional, Platas-Iglesias, Carlos, additional, de Blas, Andrés, additional, and Rodríguez-Blas, Teresa, additional

Published
2014
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183. Visualizing electrode assembly movement and lithiation heterogeneity in lithium-metal batteries using operando energy dispersive X-ray diffraction.

Author

Shkrob, Ilya A., Badami, Pavan, Okasinski, John S., Rodrigues, Marco-Tulio F., and Abraham, Daniel P.

Subjects
*LITHIATION, *X-ray diffraction, *ELECTRODES, *ENERGY density, *X-ray crystallography, *LITHIUM cells
Abstract

There is renewed interest in Li-metal anodes in order to increase the energy density of battery cells. Here, we demonstrate an operando X-ray crystallography method to visualize lithiation gradients and electrode assembly movement during electrochemical cycling of a Li-metal cell containing a Ni–Mn–Co layered oxide cathode (NMC811). During charge, deposition of Li+ ions from the cathode increases the Li foil thickness; during discharge, the thickness decreases as Li+ ions are stripped off the foil. The resulting periodic movement is observed through tracking of Bragg peaks from the ordered phases of the cathode and separator. In addition to this 3.6 μm/mAh displacement, continuous mossy Li build-up on the anode causes an irreversible drift of the assembly, which is ∼11.3 μm/cycle. Furthermore, our data indicate significant lithiation gradients in the NMC811 cathode during the oxide relithiation, which is not observed during the delithiation. Energy dispersive X-ray diffraction profilometry used to follow electrode assembly movement and lithiation in the cathode. [Display omitted] • Method developed to determine NMC811 lithiation along the cathode cross-section. • Operando X-ray method determines electrode assembly movement during battery cycling. • Cathode-separator assembly moves 3.4 mm/mAh during the Li-plating/stripping process. • Irreversible drift of the cathode-separator assembly is 11.3 mm/cycle. • Cathode gradients are minimal during charge but noticeable during discharge. [ABSTRACT FROM AUTHOR]

Published
2023
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