Controlled Experiments and Optimized Theory of Absorption Spectra of Li Metal and Salts

Abstract: Investigations of Li metal and ionic compounds through experimental and theoretical spectroscopy has been of tremendous interest due to their prospective applications in Li-metal and Li-ion batteries. Li K-edge soft X-ray absorption spectroscopy (sXAS) provides the most direct spectroscopic characterization; unfortunately, due to the low core-level energy and the highly reactive surface, Li-K sXAS of Li metal has been extremely challenging, as evidenced by many controversial reports. Here, through controlled and ultra-high energy resolution experiments of two kinds of in-situ prepared samples, we report the intrinsic Li-K sXAS of Li-metal that displays a prominent leading peak, which has never been revealed before. Furthermore, theoretical simulations show that the Li-K sXAS is strongly affected by the response of the valence electrons to the core-hole due to the low number of valence electrons in Li. We successfully reproduce the Li-K sXAS by state-of-the-art calculations with considerations of a number of relevant parameters such as temperature, resolution, and especially contributions from transitions which are forbidden in the so-called single-particle treatment. Such a comparative experimental and theoretical investigation is further extended to a series of Li ionic compounds, which highlight the importance of considering the total and single-particle energies for obtaining an accurate alignment of the spectra. Our work provides the first reliable Li-K sXAS of Li metal surface with advanced theoretical calculations. The experimental and theoretical results provide a critical benchmark for studying Li surface chemistry in both metallic and ionic states.

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A High Energy-resolution Wavelength-dispersive Soft-X-ray Spectrometer for a Transmission Electron Microscope to Investigate Valence Electrons

Microscopy and Microanalysis ◽

10.1017/s1431927604883880 ◽

2004 ◽

Vol 10 (S02) ◽

pp. 1044-1045 ◽

Cited By ~ 1

Author(s):

Masami Terauchi

Keyword(s):

Electron Microscope ◽

Energy Resolution ◽

Transmission Electron Microscope ◽

High Energy ◽

High Energy Resolution ◽

X Ray ◽

Transmission Electron ◽

Valence Electrons

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

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Microcalorimeter EDS Measurements of Chemical Shifts in Fe Compounds

Microscopy and Microanalysis ◽

10.1017/s1431927600021103 ◽

1998 ◽

Vol 4 (S2) ◽

pp. 196-197 ◽

Cited By ~ 1

Author(s):

D. A. Wollman ◽

Dale E. Newbury ◽

G. C. Hilton ◽

K. D. Irwin ◽

L. L. Dulcie ◽

...

Keyword(s):

Chemical Shifts ◽

Energy Dispersive Spectrometer ◽

Emission Spectra ◽

High Energy ◽

Peak Position ◽

Binding Energies ◽

High Energy Resolution ◽

X Ray ◽

Valence Electrons ◽

Electron Binding Energies

We report measurements of chemical shifts in the Fe-L x-ray lines of different Fe compounds from xray emission spectra acquired using a microcalorimeter energy dispersive spectrometer (EDS). The observed changes in peak position and relative intensity of the Fe-L x-ray lines are in agreement with measurements obtained using a wavelength dispersive spectrometer (WDS), demonstrating the usefulness of microcalorimeter EDS for high-energy-resolution x-ray microanalysis.Chemical shifts result from changes in electron binding energies with the chemical environment of atoms. In x-ray spectra, chemical shifts lead to changes in x-ray peak positions, relative peak intensities, and peak shapes. These chemical bonding effects can be significant (with x-ray peak shifts on the order of 1 eV), particularly for x-ray lines resulting from transitions involving valence electrons of light elements such as B and C.

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High energy resolution spectrometer for the dedicated STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112725 ◽

1984 ◽

Vol 42 ◽

pp. 558-559 ◽

Cited By ~ 1

Author(s):

P.E. Batson

Keyword(s):

Collection Efficiency ◽

Core Loss ◽

Beam Current ◽

High Energy ◽

High Energy Resolution ◽

Acquisition Time ◽

Good Definition ◽

Loss Analysis ◽

Definition Of ◽

Acceleration Voltage

Use of the STEM to obtain precise electronic information has been hampered by the lack of energy loss analysis capable of a resolution and accuracy comparable to the 0.3eV energy width of the Field Emission Source. Recent work by Park, et. al. and earlier by Crewe, et. al. have promised magnetic sector devices that are capable of about 0.75eV resolution at collection angles (about 15mR) which are great enough to allow efficient use of the STEM probe current. These devices are also capable of 0.3eV resolution at smaller collection angles (4-5mR). The problem that arises, however, lies in the fact that, even with the collection efficiency approaching 1.0, several minutes of collection time are necessary for a good definition of a typical core loss or electronic transition. This is a result of the relatively small total beam current (1-10nA) that is available in the dedicated STEM. During this acquisition time, the STEM acceleration voltage may fluctuate by as much as 0.5-1.0V.

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Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

Nature Communications ◽

10.1038/s41467-020-20769-x ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Yanming Cai ◽

Jiaju Fu ◽

Yang Zhou ◽

Yu-Chung Chang ◽

Qianhao Min ◽

...

Keyword(s):

Energy Barrier ◽

Active Sites ◽

Theoretical Calculations ◽

High Energy ◽

Single Atom ◽

Faradaic Efficiency ◽

High Energy Barrier ◽

Catalytic Sites ◽

Electron Reduction ◽

First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

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New insights on Br speciation in volcanic glasses and structural controls on halogen degassing

American Mineralogist ◽

10.2138/am-2020-7273 ◽

2020 ◽

Vol 105 (6) ◽

pp. 795-802 ◽

Cited By ~ 3

Author(s):

Marion Louvel ◽

Anita Cadoux ◽

Richard A. Brooker ◽

Olivier Proux ◽

Jean-Louis Hazemann

Keyword(s):

Atmospheric Chemistry ◽

Divalent Cations ◽

Stratospheric Ozone ◽

High Energy ◽

Aluminosilicate Glass ◽

High Energy Resolution ◽

Magma Chambers ◽

Structural Controls ◽

Volcanic Glasses ◽

Melt Composition

Abstract The volcanic degassing of halogens, and especially of the heavier Br and I, received increased attention over the last 20 years due to their significant effect on atmospheric chemistry, notably the depletion of stratospheric ozone. While the effect of melt composition on halogen diffusion, solubility, or fluid-melt partitioning in crustal magma chambers has been thoroughly studied, structural controls on halogen incorporation in silicate melts remain poorly known, with only few studies available in simplified borosilicate or haplogranite compositions. Here, we demonstrate that high-energy resolution fluorescence detection X-ray absorption spectroscopy (HERFD-XAS) with a crystal analyzer spectrometer (CAS) is well-suited for the study of Br speciation in natural volcanic glasses which can contain lower Br concentrations than their laboratory analogs. Especially, HERFD-XAS results in sharper and better-resolved XANES and EXAFS features than previously reported and enables detection limits for EXAFS analysis down to 100 ppm when previous studies required Br concentrations above the 1000 ppm level. XANES and EXAFS analyses suggest important structural differences between synthetic haplogranitic glass, where Br is surrounded by Na and next-nearest oxygen neighbors, and natural volcanic glasses of basaltic to rhyodacitic compositions, where Br is incorporated in at least three distinct sites, surrounded by Na, K, or Ca. Similar environments, involving both alkali and alkaline earth metals have already been reported for Cl in Ca-bearing aluminosilicate glass and our study thus underlines that the association of Br with divalent cations (Ca2+) has been underestimated in the past due to the use of simplified laboratory analogs. Overall, similarities in Cl and Br structural environments over a large array of compositions (46–67 wt% SiO2) suggest that melt composition alone may not have a significant effect on halogen degassing and further support the coupled degassing of Cl and Br in volcanic systems.

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