Influence of the negative potential of molybdenum carbide derived carbon electrode on the in situ synchrotron radiation activated X-ray photoelectron spectra of 1-ethyl-3-methylimidazolium tetrafluoroborate

Kruusma, Jaanus; Tõnisoo, Arvo; Pärna, Rainer; Nõmmiste, E.; Tallo, Indrek; Romann, Tavo; Lust, Enn

doi:10.1016/j.electacta.2015.10.060

Cited by 32 publications

(27 citation statements)

References 36 publications

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“…Recently, we have applied the XPS method to study the properties of the carbon–IL interface in connection with its application in supercapacitors. [ 16–18 ] This work is a continuation of our previous experimental studies at the theoretical level. The XPS studies of the ILs referred to in this work were mainly carried out by the research groups led by Kötz, [ 19–21 ] License, [ 22–26 ] and Lust.…”

Section: Introductionmentioning

confidence: 69%

Calculation of core‐level electron spectra of ionic liquids

Lembinen

Nõmmiste

Ers

et al. 2020

Int J of Quantum Chemistry

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On the example of 40 ion pairs (5 cations times 8 anions), this study demonstrates how the core-level binding energy values can be calculated and used to plot theoretical spectra at low computational cost using density functional theory methods. Three approaches for obtaining the binding energy values are based on delta Kohn-Sham (ΔKS) calculations, 1s KS orbital energies, and atomic charges. The ΔKS results show reasonable agreement with the available experimental X-ray photoelectron data. The 1s KS orbital energies correlate well with the ΔKS results. Atomic charge correlation with ΔKS is improved by accounting for the charges of neighboring atoms. Assignment of binding energies to atoms and the applicability of the mentioned methods to model systems of ionic liquids are discussed. K E Y W O R D S core-level binding energy, delta Kohn-Sham, Green function, ionic liquid, X-ray photoelectron spectra

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Section: Introductionmentioning

confidence: 69%

Calculation of core‐level electron spectra of ionic liquids

Lembinen

Nõmmiste

Ers

et al. 2020

Int J of Quantum Chemistry

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“…It is remarkable that there was no increase in the C 5 PE signal proportion at E < −1.0 V compared with the non-polarized electrode, and oppositely to that observed for EMImBF 4 containing RTILs. 60,64 While the C(Mo 2 C) electrodes were of the same origin and handled before XPS analysis equally, very small changes in C 5 1s PE proportion could be explained by the absence of BF 4 − ions (or by very small amounts of unknown impurities that were dissolved in EMImBF 4 analyzed) in the EMImB(CN) 4 . (Thus, we propose that despite the C 5 1s XPS of EMImB(CN) 4 contains also the signal of the most distant CN − group carbon, i.e.…”

Section: Resultsmentioning

confidence: 99%

The Electrochemical Behavior of 1-Ethyl-3-Methyl Imidazolium Tetracyanoborate Visualized by In Situ X-ray Photoelectron Spectroscopy at the Negatively and Positively Polarized Micro-Mesoporous Carbon Electrode

Kruusma

Tõnisoo

Pärna

et al. 2017

J. Electrochem. Soc.

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The electrochemical properties of the C(Mo 2 C) | EMImB(CN) 4 system have been analyzed using cyclic voltammetry, in situ X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy techniques. The cyclic voltammetry and electrochemical impedance measurements indicated that the tetracyanoborate anions started to electrooxidize and electropolymerize at E = 2.12 V (vs. Ag/AgCl in EMImBF 4 ). However, despite of the formation of compact dielectric polymer layer at the micro-mesoporous C(Mo 2 C) electrode surface very slow electrochemical polymerization of tetracyanoborate anions continued further at E > 2.12 V leading to the blocking of the C(Mo 2 C) electrode porous structure and to the reduction of the electrochemically active surface area necessary for the construction of the high energy density supercapacitors. Thus, the tetracyanoborate anion based ionic liquids can be used as the electrolytes for the initial formation of the passivating solid-electrolyte interface for the very wide cell potential supercapacitor positive electrodes, as an electrolyte additives for the solid-electrolyte interface formation or for the correction of the solid-electrolyte interface damages. Room temperature ionic liquids (RTILs) are remarkable electrolytes (salts) being in a liquid form at or near the room temperature. This means that it is possible to construct the electrical energy storage systems without the need for the solvent characterized usually with high vapor pressure. [1][2][3][4][5][6][7][8][9] The application of the RTILs is also very welcome in the energy technology due to their good electrical conductivity and high electrochemical stability, 10-13 low volatility [14][15][16][17] and relatively high thermal stability. [18][19][20] One class of the electrical energy storing systems, where RTILs can be used, is the electrical double layer capacitors (EDLCs). 10,[21][22][23][24][25][26][27] The EDLCs with very high power and the energy densities are also called as supercapacitors. [28][29][30] Some RTILs and the electrode materials have been investigated and described so far 12,13,22,[24][25][26][27][28][29][30][31][32][33] and the studies of the possible candidates for the supercapacitor materials and the development process of higher power and the energy density systems is still intensive. One way to increase the EDLCs energy density stored is to apply higher cell potentials while the amount of charge stored in a capacitor is proportional to the square of the applied cell potential. [28][29][30]34 Therefore it is of a great interest to study RTILs as possible electrolytes for supercapacitors at high cell potential (i.e. high operating voltage).26,34-44 However, higher cell potential can initiate the start of the faradaic processes at the supercapacitor electrodes, leading to the degradation of the materials or even to the burst of the cell body. 1,13,[45][46][47][48][49][50][51][52][53][54][55][56] One of the most electrochemically stable RTILs is 1-ethyl-3-methylimidazolium tetracyanoborate (EMImB(CN)...

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“…34. For better understanding and more detailed discussion of the collected in situ XPS data, the elements, forming the EMIm + cation, have been numbered as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…increase of faradaic capacitance, has been observed for metal and carbon electrodes. 34,35 At higher cell potentials specific capacitance somewhat decreases (ca. 15-35%), and it was demonstrated by the electrochemical impedance data analysis that irreversible adsorption of I − anions at GDC electrode takes place decreasing the power density and increasing the characteristic time constant values compared with EDLC based on EMImBF 4 .…”

mentioning

confidence: 99%

Influence of Iodide Ions Concentration on the Stability of 1-Ethyl-3-methylimidazolium Tetrafluoroborate | Molybdenum Carbide Derived Carbon Electrode Interface

Kruusma

Tõnisoo

Pärna

et al. 2017

J. Electrochem. Soc.

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Influence of the iodide ions adsorption on the in situ measured X-ray photoelectron spectra of C 1s, N 1s, B 1s, F 1s and I 3d photoelectrons, indicating the changes in the chemical composition taking place at the carbon (C) | 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) + 1-ethyl-3-methylimidazolium iodide mixed ionic liquids interface, has been studied. Simultaneously, the stability of the formed C electrode | ionic liquid interface has been analyzed electrochemically. Electroreduction of the BF 4 − anion seems to start at less negative potential than the 1-ethyl-3-methylimidazolium (EMIm + ) cation. Addition of the I − ions to the EMImBF 4 initiates the electrochemical processes at C electrode at lower negative or positive potentials. However, intensity of the electrochemical reduction of EMIm + cation was suppressed. The experiments, performed in the vacuum conditions, indicated that slow faradaic oxidation processes started already at E ≥ 1.0 V (vs. Ag/AgCl in EMImBF 4 ). Our investigations clearly show that the formed passivating layer at the carbon electrode is unstable and decomposes slowly producing gaseous products. Based on the analysis of results collected the electrode materials for electrochemical double layer capacitors should be tested in the vacuum conditions in order to detect the early start of very slow faradaic processes producing gaseous products. Electrochemical double layer capacitors (EDLCs) are one of the electric charge storage systems. Very high specific capacitance values (from 75 to 175 F g −1 for aqueous and from 40 to 100 F g −1 for nonaqueous electrolytes based commercial EDLC cells, 1-3 and 100 -150 F g −1 for micro-mesoporous carbon electrodes or nonaqueous electrolytes and ionic liquid based EDLC cells 4-10 ) have been measured. These devices are also called as "supercapacitors" 1-3,11-17 and used as short term high electric power density systems or as filtering or stabilizing elements in the electric circuits.12,14 It should be noted that the EDLCs are composed of various electrode materials and electrolyte solutions (ionic liquids and non-aqueous solutions are often used [14][15][16][17] ). The power density of an EDLC depends on the mobility of the electrolyte ions (on the electric conductivity of a system 13,14 ) and the specific capacitance depends on the total gravimetric area of the electrode. To expand the specific capacitance of an EDLC the electrochemically active area and/or the applicable cell potential should be increased, because the energy and power densities are root functions of the cell potential.1-17 However, the value of the maximum achievable electrochemically active specific area is limited by the optimal pore diameter determined by the size of the dissolved electrolyte ions (solvated or partially desolvated 8 ) and the solvent molecules dimensions. Thus, the expansion of the applicable cell potential seems to be the only solution for the significant expansion of the EDLCs specific energy (measured in Wh kg −1 ) and specific power (measured i...

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Influence of the negative potential of molybdenum carbide derived carbon electrode on the in situ synchrotron radiation activated X-ray photoelectron spectra of 1-ethyl-3-methylimidazolium tetrafluoroborate

Cited by 32 publications

References 36 publications

Calculation of core‐level electron spectra of ionic liquids

Calculation of core‐level electron spectra of ionic liquids

The Electrochemical Behavior of 1-Ethyl-3-Methyl Imidazolium Tetracyanoborate Visualized by In Situ X-ray Photoelectron Spectroscopy at the Negatively and Positively Polarized Micro-Mesoporous Carbon Electrode

Influence of Iodide Ions Concentration on the Stability of 1-Ethyl-3-methylimidazolium Tetrafluoroborate | Molybdenum Carbide Derived Carbon Electrode Interface

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