@article {756,
	title = {Rate Constants of Electrochemical Reactions in a Lithium-Sulfur Cell Determined by Operando X-ray Absorption Spectroscopy},
	journal = {Journal of The Electrochemical Society},
	volume = {165},
	note = {{\textquoteright}doi: 10.1021/acsenergylett.0c01132\n - I.Am.Hydrogen{\textquoteright}
{\textquoteright}\n - jyoungstrom{\textquoteright}
{\textquoteright}Jason thinks this is great.\n~\n - jyoungstrom{\textquoteright}
{\textquoteright}\n - estechel{\textquoteright}
},
	pages = {A3487-A3495},
	abstract = {The reduction of sulfur during discharge in a lithium-sulfur (Li-S) cell is known to occur in a series of reaction steps that involve lithium polysulfide intermediates. We present an operando study of the discharge of a solid-state Li-S cell using X-ray absorption spectroscopy (XAS). In theory, the average chain length of the polysulfides, xavg,cell, at a given depth of discharge is determined by the number of electrons delivered to the sulfur cathode. The dependence of xavg,cell measured by XAS on the depth of discharge is in excellent agreement with theoretical predictions. XAS is also used to track the formation of Li2S, the final discharge product, as a function of depth of discharge. The XAS measurements were used to estimate rate constants of a series of simple reactions commonly accepted in literature.},
	issn = {0013-4651, 1945-7111},
	doi = {10.1149/2.0981814jes},
	url = {http://jes.ecsdl.org/content/165/14/A3487},
	author = {Dunyang Rita Wang and Deep B. Shah and Jacqueline A. Maslyn and Whitney S. Loo and Kevin H. Wujcik and Erik J. Nelson and Matthew J. Latimer and Jun Feng and David Prendergast and Tod A. Pascal and Nitash P. Balsara}
}
@article {757,
	title = {Structural Change of the Mn Cluster during the S2{\textrightarrow}S3 State Transition of the Oxygen-Evolving Complex of Photosystem II. Does It Reflect the Onset of Water/Substrate Oxidation? Determination by Mn X-ray Absorption Spectroscopy},
	journal = {Journal of the American Chemical Society},
	volume = {122},
	note = {{\textquoteright}doi: 10.1021/acsenergylett.0c01132\n - I.Am.Hydrogen{\textquoteright}
{\textquoteright}\n - jyoungstrom{\textquoteright}
{\textquoteright}Jason thinks this is great.\n~\n - jyoungstrom{\textquoteright}
{\textquoteright}\n - estechel{\textquoteright}
},
	pages = {3399-3412},
	abstract = {The oxygen-evolving complex of Photosystem II in plants and cyanobacteria catalyzes the oxidation of two water molecules to one molecule of dioxygen. A tetranuclear Mn complex is believed to cycle through five intermediate states (S0-S4) to couple the four-electron oxidation of water with the one-electron photochemistry occurring at the Photosystem II reaction center. We have used X-ray absorption spectroscopy to study the local structure of the Mn complex and have proposed a model for it, based on studies of the Mn K-edges and the extended X-ray absorption fine structure of the S1 and S2 states. The proposed model consists of two di-μ-oxo-bridged binuclear Mn units with Mn-Mn distances of \~{}2.7 {\r A} that are linked to each other by a mono-μ-oxo bridge with a Mn-Mn separation of \~{}3.3 {\r A}. The Mn-Mn distances are invariant in the native S1 and S2 states. This report describes the application of X-ray absorption spectroscopy to S3 samples created under physiological conditions with saturating flash illumination. Significant changes are observed in the Mn-Mn distances in the S3 state compared to the S1 and the S2 states. The two 2.7 {\r A} Mn-Mn distances that characterize the di-μ-oxo centers in the S1 and S2 states are lengthened to \~{}2.8 and 3.0 {\r A} in the S3 state, respectively. The 3.3 {\r A} Mn-Mn and Mn-Ca distances also increase by 0.04-0.2 {\r A}. These changes in Mn-Mn distances are interpreted as consequences of the onset of substrate/water oxidation in the S3 state. Mn-centered oxidation is evident during the S0{\textrightarrow}S1 and S1{\textrightarrow}S2 transitions. We propose that the changes in Mn-Mn distances during the S2{\textrightarrow}S3 transition are the result of ligand or water oxidation, leading to the formation of an oxyl radical intermediate formed at a bridging or terminal position. The reaction of the oxyl radical with OH-, H2O, or an oxo group during the subsequent S state conversion is proposed to lead to the formation of the O-O bond. Models that can account for changes in the Mn-Mn distances in the S3 state and the implications for the mechanism of water oxidation are discussed.},
	issn = {0002-7863},
	doi = {10.1021/ja992501u},
	url = {https://doi.org/10.1021/ja992501u},
	author = {Wenchuan Liang and Theo A. Roelofs and Roehl M. Cinco and Annette Rompel and Matthew J. Latimer and Wa O. Yu and Kenneth Sauer and Melvin P. Klein and Vittal K. Yachandra}
}
