Spectra analysis of the XPS core and valence energy levels of polymers by an ab initio mo method using simple model molecules

Endo, Kazunaka; Inoue, Chiaki; Kobayashi, Naoya; Aida, Masayuki

doi:10.1016/0022-3697(94)90151-1

Cited by 50 publications

(32 citation statements)

References 15 publications

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“…3, 1995 The reason is as follows: The approximate linewidth which we used here corresponds to the experimental result that the linewidth of spectra in the inner valence energy levels is broader than in the outer energy levels. As mentioned in a previous paper, 17 the spectral linewidths below about 13 eV are determined by the splittings of many adjacent MO levels. By contrast, the linewidths in the range of l3-30eV are governed by the relaxation of the inner valence 2s electron states for the MO energy levels.…”

Section: Resultsmentioning

confidence: 99%

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Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

Inoue

Kaneda

Aida

et al. 1995

Polym J

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ABSTRACT:The X-ray photoelectron spectra (XPS) of polymers . (R=OH, COOH, and OCOCH3) and (CH 2---C(C H3)COOCH3).] were simulated by an ab initio MO method using model molecules of [H-(CH2---CHRh-H (R=OH, COOH, and OCOCH3) and H-(CH2---C(CH3)COOCH3)z-H], respectively. The calculated AI-K. photoelectron spectra were obtained using Gaussian functions of a fixed linewidth of 2.1 and 1.3 eV for core Oi, and C 1, energy levels, respectively, and given using Gaussian functions of a fixed approximate linewidth (O. l 5Ek) for valence energy levels. Ek= E~ -(EoKT + WD), where E~ is the eigenvalue of each MO and (E0 KT+ WD) is an approximate shift in the energy scale to account for sum of the difference due to the Koopmans' theorem and work function and other energy effects. We assumed that the sum corresponds to the shift we must apply before we can compare the calculated spectrum for the single model molecule with the observed spectrum for the solid. The theoretical spectra without considering the contraction factor in the energy scale showed fairly good agreement with the spectra of polymers as observed, although the shift values were used as 10, 26.5, and 21.5 eV for valence, core 0 1, and C1, core energy levels of the four polymers, respectively.KEY WORDS XPS / Ab initio MO / Spectral Simulation / Orbital Nature / Polymer / Poly(vinyl alcohol) / Poly(acrylic acid) / Poly(vinyl acetate) / Poly(methyl methacrylate) / The X-ray photoelectron spectroscopy (XPS) technique 1 • 2 from monochromatized X-ray radiation provided precise information on core level binding energies and linewidths, and recorded the distribution of the valence electronic levels which constitute a unique fingerprint of a compound. On the other hand, there have been many theoretical studies of the electronic structures of polymers by the ab initio and semi-empirical molecular orbital (MO) calculations. In these calculations, XPS core and ultraviolet-ray photoelectron spectroscopy (UPS) and XPS valence level studies 3 -20 of simple model oligomers of polymers showed from both theoretical and experimental viewpoints that information on the polymer molecular structure can be obtained through spectral analysis using MO calculations.To analyze photoelectron spectra of polymers, we need to estimate the wavefunction of the cationic state corresponding to each MO losing an electron after X-ray irradiation. Some studies 3 • 4 have shown that the core binding energies of poly(methyl methacrylate) (PMMA) using the monomer model molecules (methyl methacrylate and the substitution compounds) are in good accordance with the theoretical values as calculated by the delta self-consistent-field, ASCF, method. However, we can simulate the XPS with Koopmans' theorem and the usual MO calculations of the ground state using ab initio and semi-empirical MO methods. In previous papers, 15 -17 we used the shifts of about l O e V in the energy 300

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Section: Resultsmentioning

confidence: 99%

“…Tables II and III show the observed peaks, the Koopmans' value, the main AO for the PICS, the orbital nature and the functional group for PV A and PAA using the model trimer molecules (similar tables for PVAC and PMMA is omitted, as shown in a previous paper.) 17 • Shows the peak range. b Band NB mean bonding and non bonding, respectively.…”

Section: Resultsmentioning

confidence: 99%

Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

Inoue

Kaneda

Aida

et al. 1995

Polym J

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“…carbonates (∼532eV), 29 carboxylates or poly-ether polymers). 42 The same conclusion can be made while inspecting the C 1s spectrum, which displays the presence a wide range of species, such as CO x and CH x (e.g. ethers or carbonates).…”

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confidence: 81%

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

Guéguen

Novák

Berg

2016

J. Electrochem. Soc.

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The surface chemistry of the commonly employed positive electrode substrate Super C65 carbon was investigated during the 1 st cycle of a Li-O 2 battery with a typical ether electrolyte (0.2 M LiTFSI in Diglyme) by performing in situ online electrochemical mass spectrometry (OEMS), ex situ scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS). During discharge, a nanometer-thin (< 5 nm) layer of Li 2 O 2 forms homogeneously throughout the electrode before it is passivated at a final specific charge of ∼365 mAh/g. Higher discharge charge rates lead to thinner and more densely packed layers of Li 2 O 2 . Electrolyte decomposition also occurs in parallel, as evidenced by the continuous increase of LiF and sulfur containing species of the degraded LiTFSI salt. On charge, O 2 evolves initially according to a 2e − /O 2 rate, but as the cell over-potentials increase, O 2 evolution rate approaches 4e − /O 2 , thus demonstrating a significant extent of parasitic side-reactions. Unlike the discharge, the charge leads to inhomogeneous electrode reactions causing a continuous removal of Li 2 O 2 with no indication of LiO 2 or Li 2 O intermediates. The decomposition side-products formed during discharge are also removed and the spectra of the pristine electrode are nearly retained at a full charge. Our results show that the analysis of Li-O 2 battery chemistry requires broad approach based on the combination of various electrode surface sensitive techniques, such as XPS and OEMS, in order to provide further fundamental understanding of the mechanisms behind the complex electrochemistry involving the Li and O 2 as well as several other predominant degradation products of the electrode and electrolyte. Non-aqueous electrolyte based Li-O 2 batteries have been a subject of intensive research during the past years, mainly because of their high theoretical specific charge (∼1100 mAh/g Li2O2 ), which provide promising prospects for their implementation in future energy storage systems.1 Several challenges do however remain, of which the most notable are the low round-trip efficiency and poor cycling performance, both partly related to the electrode/electrolyte instability.2,3 On discharge of the Li-O 2 cell, gaseous oxygen dissolves in the electrolyte and is reduced at the positive porous electrode where it combines with Li + (from the negative Li metal electrode) to form solid Li 2 O 2 deposits according to forward reaction of 2Li + O 2 Li 2 O 2 . Upon charge, the reaction is reversed to release the initial reactants Li + and O 2 gas. Despite extensive research on several classes of electrodes and electrolytes (including carbons, gold, carbides, oxides substrates combined with carbonate, sulfoxide, [4][5][6] nitrile, 4,5,7 amide, ionic liquid 8,9 or ether 10-13 based electrolytes, to mention a few), no composition has so far displayed sufficient chemical stability toward the reduced oxygen species to sustain a satisfactory number of discharge/charge cycles.1 The cell failure has been...

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“…Single point energy calculations were run using the double-zeta valence plus polarization DGDVZP basis set [45] on the optimized model and density of state (DOS), MO compositions and overlap populations were calculated using the AOMix software [46]. Calculated VB spectra were adjusted by correcting the DOS levels by Scofield photoelectric cross-sections [47] according to the MO compositions at each energy level [48,49]. MO energy levels were also convoluted using a Gaussian/Lorentzian peak [50] with a 0.9 ratio and a 1. technique has been used extensively over the past 20 years with sufficient resolution to distinguish the major features specific to the materials being examined [48][49][50].…”

Section: Valence Band Modelingmentioning

confidence: 99%

Polymer nanocomposite – fiber model interphases: Influence of processing and interface chemistry on mechanical performance

Rider

Brack

et al. 2015

Chemical Engineering Journal

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Spectra analysis of the XPS core and valence energy levels of polymers by an ab initio mo method using simple model molecules

Cited by 50 publications

References 15 publications

Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle

Polymer nanocomposite – fiber model interphases: Influence of processing and interface chemistry on mechanical performance

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Spectra analysis of the XPS core and valence energy levels of polymers by an ab initio mo method using simple model molecules

Cited by 50 publications

References 15 publications

Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

Simulation of XPS of Poly(vinyl alcohol), Poly(acrylic acid), Poly(vinyl acetate), and Poly(methyl methacrylate) Polymers by an Ab Initio MO Method Using the Model Molecules

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O2Batteries during the 1st Cycle

Polymer nanocomposite – fiber model interphases: Influence of processing and interface chemistry on mechanical performance

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Product

Resources

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XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O₂Batteries during the 1st Cycle