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Asymmetrical Zn thin foil|carbon cloth two-electrode cells based on 1 M Zn(ClO4)2 aqueous solution have been tested using cyclic voltammetry, constant current charge/discharge, and electrochemical impedance methods. The Ragone plots have been calculated from constant power measurements data. Very high gravimetric and volumetric energy densities at moderate gravimetric and volumetric power densities have been calculated, nearly 2–3 times higher than those for the best sol–gel method prepared two carbon electrode single cells. It was found that even at high power density (10 kW kg−1), the energy density values are comparable with the results for best CDC and sol–gel methods prepared carbon materials based supercapacitors. It has been observed that studied asymmetrical two-electrode cells demonstrated higher energy densities (~ 70 W h kg−1) than the ionic liquid based symmetrical cells what show energy density up to 47 W h kg−1 and capacitance ~ 120 F g−1. However, the power densities and relaxation times for Zn(ClO4)2 aqueous electrolyte based supercapacitors still need to be increased and decreased, respectively, to meet the needs of very quick short pulses high power energy storage applications.
Jaanus Eskusson; Thomas Thomberg; Tavo Romann; Karmen Lust; Enn Lust; Alar Jänes. Zn(ClO4)2 aqueous solution–based Zn thin foil|carbon cloth two-electrode single-cell characteristics. Journal of Solid State Electrochemistry 2021, 1 -12.
AMA StyleJaanus Eskusson, Thomas Thomberg, Tavo Romann, Karmen Lust, Enn Lust, Alar Jänes. Zn(ClO4)2 aqueous solution–based Zn thin foil|carbon cloth two-electrode single-cell characteristics. Journal of Solid State Electrochemistry. 2021; ():1-12.
Chicago/Turabian StyleJaanus Eskusson; Thomas Thomberg; Tavo Romann; Karmen Lust; Enn Lust; Alar Jänes. 2021. "Zn(ClO4)2 aqueous solution–based Zn thin foil|carbon cloth two-electrode single-cell characteristics." Journal of Solid State Electrochemistry , no. : 1-12.
The adsorption of I− anions on the Bi(111) single-crystal plane from solutions in vinylene carbonate has been investigated with impedance measurement method. Both electrode charge and electrode potential were applied as the independent electrical variables in the calculations of the ionic charge due to the specific adsorption following the mixed-electrolyte method. The Gibbs energy of I− anion adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the standard Gibbs energy values obtained at constant electrode potential and at constant electrode charge are coincident and the Gibbs energy of I− anion adsorption increases weakly in the sequence of carbonates: vinylene carbonate < ethylene carbonate < propylene carbonate, but adsorption of I− is lower than from gamma-butyrolactone. The electrosorption valency values have been calculated and it was found that this parameter increases in the same sequence of solvents as the Gibbs energy of adsorption of I− anions.
Mart Väärtnõu; Enn Lust. Adsorption of iodide ions at the Bi | vinylene carbonate interface. Journal of Solid State Electrochemistry 2021, 1 -8.
AMA StyleMart Väärtnõu, Enn Lust. Adsorption of iodide ions at the Bi | vinylene carbonate interface. Journal of Solid State Electrochemistry. 2021; ():1-8.
Chicago/Turabian StyleMart Väärtnõu; Enn Lust. 2021. "Adsorption of iodide ions at the Bi | vinylene carbonate interface." Journal of Solid State Electrochemistry , no. : 1-8.
In this work we have studied the effect of 1 M bis(trifluoromethanesulfonyl)imide metallic salts in acetonitrile (1 M MeTFSI, where Me = Li, Na, K, Cs or Mg) as an electrolyte for electrochemical capacitors (ECs), using computational quantum mechanical modelling, Raman analysis, cyclic voltammetry, electrochemical impedance spectroscopy and constant power methods. Also, the ionic conductivities of 1 M MeTFSI in AN have been measured and discussed. The ECs based on the 1 M KTFSI in AN electrolyte deliver the higher power density and energy density compared to other MeTFSI based electrolytes and showing excellent characteristics applicable in high energy and power EC devices.
T. Romann; J. Eskusson; T. Thomberg; E. Lust; A. Jänes. Bis(trifluoromethanesulfonyl)imide Metallic Salts Based Electrolytes for Electrochemical Capacitor Application: Theoretical vs Experimental Performance. Journal of The Electrochemical Society 2021, 168, 070528 .
AMA StyleT. Romann, J. Eskusson, T. Thomberg, E. Lust, A. Jänes. Bis(trifluoromethanesulfonyl)imide Metallic Salts Based Electrolytes for Electrochemical Capacitor Application: Theoretical vs Experimental Performance. Journal of The Electrochemical Society. 2021; 168 (7):070528.
Chicago/Turabian StyleT. Romann; J. Eskusson; T. Thomberg; E. Lust; A. Jänes. 2021. "Bis(trifluoromethanesulfonyl)imide Metallic Salts Based Electrolytes for Electrochemical Capacitor Application: Theoretical vs Experimental Performance." Journal of The Electrochemical Society 168, no. 7: 070528.
In this study, several peat-derived carbons (PDC) were synthesized using various carbonization protocols. It was found that depending on the carbonization method, carbons with very different surface morphologies, elemental compositions, porosities, and oxygen reduction reaction (ORR) activities were obtained. Five carbons were used as carbon supports to synthesize Co-N/PDC catalysts, and five different ORR catalysts were acquired. The surface analysis revealed that a higher nitrogen content, number of surface oxide defects, and higher specific surface area lead to higher ORR activity of the Co-N/PDC catalysts in acidic solution. The catalyst Co-N/C-2(ZnCl2), which was synthesized from ZnCl2-activated and pyrolyzed peat, showed the highest ORR activity in both rotating disk electrode and polymer electrolyte membrane fuel cell tests. A maximum power density value of 210 mW cm−2 has been obtained. The results of this study indicate that PDCs are promising candidates for the synthesis of active non-platinum group metal type catalysts.
Rutha Jäger; Patrick Teppor; Maarja Paalo; Meelis Härmas; Anu Adamson; Olga Volobujeva; Eneli Härk; Zdravko Kochovski; Tavo Romann; Riinu Härmas; Jaan Aruväli; Arvo Kikas; Enn Lust. Synthesis and Characterization of Cobalt and Nitrogen Co-Doped Peat-Derived Carbon Catalysts for Oxygen Reduction in Acidic Media. Catalysts 2021, 11, 715 .
AMA StyleRutha Jäger, Patrick Teppor, Maarja Paalo, Meelis Härmas, Anu Adamson, Olga Volobujeva, Eneli Härk, Zdravko Kochovski, Tavo Romann, Riinu Härmas, Jaan Aruväli, Arvo Kikas, Enn Lust. Synthesis and Characterization of Cobalt and Nitrogen Co-Doped Peat-Derived Carbon Catalysts for Oxygen Reduction in Acidic Media. Catalysts. 2021; 11 (6):715.
Chicago/Turabian StyleRutha Jäger; Patrick Teppor; Maarja Paalo; Meelis Härmas; Anu Adamson; Olga Volobujeva; Eneli Härk; Zdravko Kochovski; Tavo Romann; Riinu Härmas; Jaan Aruväli; Arvo Kikas; Enn Lust. 2021. "Synthesis and Characterization of Cobalt and Nitrogen Co-Doped Peat-Derived Carbon Catalysts for Oxygen Reduction in Acidic Media." Catalysts 11, no. 6: 715.
Estonian phosphorite ore contains trace amounts of rare earth elements (REEs), many other d-metals, and some radioactive elements. Rare earth elements, Mo, V, etc. might be economically exploitable, while some radioactive and toxic elements should be removed before any other downstream processing for environmental and nutritional safety reasons. All untreated hazardous elements remain in landfilled waste in much higher concentration than they occur naturally. To resolve this problem U, Th, and Tl were removed from phosphorite ore at first using liquid extraction. In the next step, REE were isolated from raffinate. Nitrated Aliquat 336 (A336[NO3]) and Bis(2-ethylhexyl) Phosphate (D2EHPA) were used in liquid extraction for comparison. An improved method for exclusive separation of radioactive elements and REEs from phosphorite ore in 2-steps has been developed, exploiting liquid extraction at different pH values.
Silvester Jürjo; Liis Siinor; Carolin Siimenson; Päärn Paiste; Enn Lust. Two-Step Solvent Extraction of Radioactive Elements and Rare Earths from Estonian Phosphorite Ore Using Nitrated Aliquat 336 and Bis(2-ethylhexyl) Phosphate. Minerals 2021, 11, 388 .
AMA StyleSilvester Jürjo, Liis Siinor, Carolin Siimenson, Päärn Paiste, Enn Lust. Two-Step Solvent Extraction of Radioactive Elements and Rare Earths from Estonian Phosphorite Ore Using Nitrated Aliquat 336 and Bis(2-ethylhexyl) Phosphate. Minerals. 2021; 11 (4):388.
Chicago/Turabian StyleSilvester Jürjo; Liis Siinor; Carolin Siimenson; Päärn Paiste; Enn Lust. 2021. "Two-Step Solvent Extraction of Radioactive Elements and Rare Earths from Estonian Phosphorite Ore Using Nitrated Aliquat 336 and Bis(2-ethylhexyl) Phosphate." Minerals 11, no. 4: 388.
Quick characterization methods to determine the structure of carbon materials are sought after for a wide array of technical applications. In this study we present the combined analysis of the structure of carbide-derived carbons (CDCs) with Raman spectroscopy and wide-angle X-ray scattering (WAXS) methods. We present the optimal deconvolution method to be used for the detailed analysis of Raman spectroscopy data of CDCs and comparison to corresponding WAXS results is made. For a broad set of CDCs both WAXS and Raman spectroscopy data showed that the average graphene layer extent increases with synthesis temperature of CDC, while the coherent domain lengths obtained from Raman spectroscopy higher by an average of 4.4 nm. In addition, the presence of correlations between the parameters (D-band width and the parameter A ∑D/A ∑G) from Raman spectroscopy and the synthesis temperature are established. Based on the WAXS and Raman spectra data analysis the strong influence of the precursor carbide structure on the graphitization pathway is shown.
Riinu Härmas; Rasmus Palm; Heisi Kurig; Laura Puusepp; Torben Pfaff; Tavo Romann; Jaan Aruväli; Indrek Tallo; Thomas Thomberg; Alar Jänes; Enn Lust. Carbide-Derived Carbons: WAXS and Raman Spectra for Detailed Structural Analysis. C 2021, 7, 29 .
AMA StyleRiinu Härmas, Rasmus Palm, Heisi Kurig, Laura Puusepp, Torben Pfaff, Tavo Romann, Jaan Aruväli, Indrek Tallo, Thomas Thomberg, Alar Jänes, Enn Lust. Carbide-Derived Carbons: WAXS and Raman Spectra for Detailed Structural Analysis. C. 2021; 7 (1):29.
Chicago/Turabian StyleRiinu Härmas; Rasmus Palm; Heisi Kurig; Laura Puusepp; Torben Pfaff; Tavo Romann; Jaan Aruväli; Indrek Tallo; Thomas Thomberg; Alar Jänes; Enn Lust. 2021. "Carbide-Derived Carbons: WAXS and Raman Spectra for Detailed Structural Analysis." C 7, no. 1: 29.
In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film Ni−Ce0.9Gd0.1O2−δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H2 pressures and at different electrochemical conditions at around 650 °C. The possible redox reactions on the anode surface (Ni2+↔Ni0,Ce4+↔Ce3+) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the Ce3d and Ni2p photoelectron spectra caused by electrode potential and H2 pressure variations were observed and estimated by curve fitting procedure. The O1s and valence band photoelectron signals were used for depth probing of the chemical composition and redox changes at Ni-GDC and for studying the influence of the electrochemical polarization on the chemical state of Ni-GDC surface atoms. As a result changes in oxidation state of electrode surface atoms caused by electrode polarization and oxide ion flux through the membrane were detected with simultaneous significant variation of electrochemical impedance.
Kuno Kooser; Tanel Käämbre; Mihkel Vestli; Urmas Joost; Samuli Urpelainen; Mati Kook; Fabrice Bournel; Jean-Jacques Gallet; Enn Lust; Edwin Kukk; Gunnar Nurk. Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode. International Journal of Hydrogen Energy 2020, 45, 25286 -25298.
AMA StyleKuno Kooser, Tanel Käämbre, Mihkel Vestli, Urmas Joost, Samuli Urpelainen, Mati Kook, Fabrice Bournel, Jean-Jacques Gallet, Enn Lust, Edwin Kukk, Gunnar Nurk. Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode. International Journal of Hydrogen Energy. 2020; 45 (46):25286-25298.
Chicago/Turabian StyleKuno Kooser; Tanel Käämbre; Mihkel Vestli; Urmas Joost; Samuli Urpelainen; Mati Kook; Fabrice Bournel; Jean-Jacques Gallet; Enn Lust; Edwin Kukk; Gunnar Nurk. 2020. "Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode." International Journal of Hydrogen Energy 45, no. 46: 25286-25298.
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.
Meeri Lembinen; Ergo Nõmmiste; Heigo Ers; Borja Docampo‐Álvarez; Jaanus Kruusma; Enn Lust; Vladislav B. Ivaništšev. Calculation of core‐level electron spectra of ionic liquids. International Journal of Quantum Chemistry 2020, 120, 1 .
AMA StyleMeeri Lembinen, Ergo Nõmmiste, Heigo Ers, Borja Docampo‐Álvarez, Jaanus Kruusma, Enn Lust, Vladislav B. Ivaništšev. Calculation of core‐level electron spectra of ionic liquids. International Journal of Quantum Chemistry. 2020; 120 (14):1.
Chicago/Turabian StyleMeeri Lembinen; Ergo Nõmmiste; Heigo Ers; Borja Docampo‐Álvarez; Jaanus Kruusma; Enn Lust; Vladislav B. Ivaništšev. 2020. "Calculation of core‐level electron spectra of ionic liquids." International Journal of Quantum Chemistry 120, no. 14: 1.
For the first time, a novel peat-derived carbon (PDC) was used to synthesize an active non-platinum group metal type catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The obtained catalyst exhibited a smaller specific surface area and was more graphitic compared to a catalyst synthesized identically but using carbide-derived carbon (CDC) instead of PDC. Due to the organic nature of the used peat, the PDC contained numerous additives. In 0.1 M KOH, both the PDC and CDC-based catalysts displayed ORR activity comparable to Pt/Vulcan. Additionally, equally high OER activities of 1.59 V vs RHE at 10 mA cm-2 were reached for both catalysts studied. Considering the remarkable bifunctional activity of the PDC-based catalyst, it can be concluded that PDC is an exceptionally promising carbon support material for ORR and OER catalysts.
P. Teppor; R. Jäger; M. Paalo; R. Palm; O. Volobujeva; E. Härk; Z. Kochovski; T. Romann; R. Härmas; J. Aruväli; Arvo Kikas; E. Lust. Peat-derived carbon-based non-platinum group metal type catalyst for oxygen reduction and evolution reactions. Electrochemistry Communications 2020, 113, 106700 .
AMA StyleP. Teppor, R. Jäger, M. Paalo, R. Palm, O. Volobujeva, E. Härk, Z. Kochovski, T. Romann, R. Härmas, J. Aruväli, Arvo Kikas, E. Lust. Peat-derived carbon-based non-platinum group metal type catalyst for oxygen reduction and evolution reactions. Electrochemistry Communications. 2020; 113 ():106700.
Chicago/Turabian StyleP. Teppor; R. Jäger; M. Paalo; R. Palm; O. Volobujeva; E. Härk; Z. Kochovski; T. Romann; R. Härmas; J. Aruväli; Arvo Kikas; E. Lust. 2020. "Peat-derived carbon-based non-platinum group metal type catalyst for oxygen reduction and evolution reactions." Electrochemistry Communications 113, no. : 106700.
The influence of various synthesis conditions of a metal-nitrogen-carbon (M-N/C) catalyst material on oxygen reduction reaction (ORR) kinetics is discussed. Seven M-N/C catalysts based on cobalt are obtained by changing various synthesis conditions, such as the mixing environment, pyrolysis gas, and post-treatment. The ORR activity and stability measurements are performed using the classical three-electrode configuration in a 0.1 M HClO4 solution. The most active and stable ORR catalyst proves to be the material obtained by mixing a cobalt salt, 2,2'-bipyridine, and a high surface area silicon carbide derived carbon together in water and pyrolyzing the mixture in argon. In a fuel cell test, however, a maximum power density value of 135 mW cm−2 is achieved with the catalyst mixed together in a planetary ball-mill at a low catalyst loading of 1.0 ± 0.1 mg cm−2 and at a test cell temperature of 60 oC despite of the fact that preparing the catalyst via dry ball-milling reduces the surface area of the material roughly 40% more than in the case of using a solution-based method. Consequently, mixing the catalyst precursors together without any additional chemicals in a planetary ball-mill instead of in a solution appears to be the most promising choice.
Patrick Teppor; Rutha Jäger; Eneli Härk; Silver Sepp; Mati Kook; Olga Volobujeva; Päärn Paiste; Zdravko Kochovski; Indrek Tallo; Enn Lust. Exploring Different Synthesis Parameters for the Preparation of Metal-Nitrogen-Carbon Type Oxygen Reduction Catalysts. Journal of The Electrochemical Society 2020, 167, 054513 .
AMA StylePatrick Teppor, Rutha Jäger, Eneli Härk, Silver Sepp, Mati Kook, Olga Volobujeva, Päärn Paiste, Zdravko Kochovski, Indrek Tallo, Enn Lust. Exploring Different Synthesis Parameters for the Preparation of Metal-Nitrogen-Carbon Type Oxygen Reduction Catalysts. Journal of The Electrochemical Society. 2020; 167 (5):054513.
Chicago/Turabian StylePatrick Teppor; Rutha Jäger; Eneli Härk; Silver Sepp; Mati Kook; Olga Volobujeva; Päärn Paiste; Zdravko Kochovski; Indrek Tallo; Enn Lust. 2020. "Exploring Different Synthesis Parameters for the Preparation of Metal-Nitrogen-Carbon Type Oxygen Reduction Catalysts." Journal of The Electrochemical Society 167, no. 5: 054513.
Influence of A-site deficiency and chemical composition of B-site (concentration of Ni, Mn, and Cr) on electrochemical performance of hydrogen electrode in (La1-xSrx)yCr0.5-zMn0.5-wNiz+wO3-δ|(Sc2O3)0.10(CeO2)0.01(ZrO2)0.89|La0.8Sr0.2FeO3-δ reversible solid oxide fuel cell has been studied. Electrochemical characterization has been carried out in fuel cell and electrolysis regimes. Results indicate that in fuel cell regime most notable limiting steps were detected around 0.5 Hz frequency range and were attributed to gas-solid adsorption-desorption processes. pO2 variation in the oxygen electrode compartment led to small variations in a total impedance of single cells but was not the limiting process. In electrolysis mode, the dissociative adsorption was shown as an important limiting stage and limitations in kinetic region of charge transfer step were remarkable. Increase of A-site deficiency caused a significant increase in high-frequency series resistance as well as some increase of total polarization resistance. Variation in B-site composition had a significant influence on electrochemical performance with very different frequency dependence of impedance. Highest current density values of 0.27 and 0.66 A cm−2 at unit cell potentials of 0.9 and 1.5 V, respectively, at 850°C were measured for La0.75Sr0.25Cr0.3Mn0.5Ni0.2O3-δ (fuel cell mode) and (La0.8Sr0.2)xCr0.49Mn0.49Ni0.02O3-δ (electrolysis mode) in hydrogen fuel gas with pH2O = 0.03 and 0.30 atm, respectively.
M. Maide; P. Paiste; P. Möller; E. Lust; G. Nurk. Influence of A- and B-Site Modifications of (La1-xSrx)yCr0.5-zMn0.5-wNiz+wO3-δ on Electrochemical Impedance Characteristics of Reversible Solid Oxide Cell. Journal of The Electrochemical Society 2019, 166, F1148 -F1156.
AMA StyleM. Maide, P. Paiste, P. Möller, E. Lust, G. Nurk. Influence of A- and B-Site Modifications of (La1-xSrx)yCr0.5-zMn0.5-wNiz+wO3-δ on Electrochemical Impedance Characteristics of Reversible Solid Oxide Cell. Journal of The Electrochemical Society. 2019; 166 (15):F1148-F1156.
Chicago/Turabian StyleM. Maide; P. Paiste; P. Möller; E. Lust; G. Nurk. 2019. "Influence of A- and B-Site Modifications of (La1-xSrx)yCr0.5-zMn0.5-wNiz+wO3-δ on Electrochemical Impedance Characteristics of Reversible Solid Oxide Cell." Journal of The Electrochemical Society 166, no. 15: F1148-F1156.
Platinum-praseodymium oxide complex catalysts on carbon support material have been synthesized at different conditions. Various physical methods have been used to characterize the studied materials. The catalytic activity toward methanol electrooxidation was studied using electrochemical methods and results were compared to a platinum-cerium oxide containing catalyst as well as Pt-C catalysts. High activity toward methanol electrooxidation was observed for the synthesized platinum-praseodymium oxide complex catalysts.
Peeter Valk; Jaak Nerut; Rait Kanarbik; Jaan Aruväli; Päärn Paiste; Indrek Tallo; Enn Lust. Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Electrooxidation. Journal of The Electrochemical Society 2019, 166, F1062 -F1069.
AMA StylePeeter Valk, Jaak Nerut, Rait Kanarbik, Jaan Aruväli, Päärn Paiste, Indrek Tallo, Enn Lust. Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Electrooxidation. Journal of The Electrochemical Society. 2019; 166 (14):F1062-F1069.
Chicago/Turabian StylePeeter Valk; Jaak Nerut; Rait Kanarbik; Jaan Aruväli; Päärn Paiste; Indrek Tallo; Enn Lust. 2019. "Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Electrooxidation." Journal of The Electrochemical Society 166, no. 14: F1062-F1069.
The adsorption of Br− anions on the Bi(111) single crystal plane from solutions in propylene carbonate and gamma-valerolactone has been investigated with impedance measurements. The ionic charge due to the specific adsorption has been obtained using the mixed-electrolyte method applied for both electrode charge and electrode potential as the independent electrical variables. The Gibbs energy of Br− anions adsorption has been calculated using the virial adsorption isotherm. It was found that under comparable conditions, the standard Gibbs energy values obtained at constant electrode potential and at constant electrode charge, are coincident and the Gibbs energy of Br− anion adsorption increases in the sequence of solvents: ethanol < propylene carbonate < gamma-valerolactone. The electrosorption valency values have been calculated and it was found that this parameter increases in the sequence: propylene carbonate ≤ ethanol < gamma-valerolactone.
Mart Väärtnõu; Enn Lust. Adsorption of bromide ions at the Bi | gamma-valerolactone and Bi | propylene carbonate interfaces. Journal of Electroanalytical Chemistry 2019, 851, 113438 .
AMA StyleMart Väärtnõu, Enn Lust. Adsorption of bromide ions at the Bi | gamma-valerolactone and Bi | propylene carbonate interfaces. Journal of Electroanalytical Chemistry. 2019; 851 ():113438.
Chicago/Turabian StyleMart Väärtnõu; Enn Lust. 2019. "Adsorption of bromide ions at the Bi | gamma-valerolactone and Bi | propylene carbonate interfaces." Journal of Electroanalytical Chemistry 851, no. : 113438.
The electrical double layer capacitors (EDLC) based on hierarchical micro-mesoporous sol-gel TiC derived carbon (SgTiC-CDC) electrodes and 1-ethyl-3-methylimidazolium tetrafluoroborate (EtMeImBF4) and 1M Et3MeNBF4 + acetonitrile (AN) as the electrolytes were tested to establish the electrochemical characteristics and region of ideal polarizability. The precursors for the micro-mesoporous carbon electrodes were synthesized via modified sol-gel synthesis process. Compared to traditional titanium carbide derived carbons, where precursor carbide is commercially available, the sol-gel TiC derived hierarchical carbon materials exhibit larger specific density functional theory (DFT) surface areas (up to 1700 m2 g−1) and an unique pore size distribution with more mesopores between 2 and 10 nm. The electrochemical properties of the EDLCs were investigated using the cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge/discharge and constant power discharge methods. The EDLCs demonstrated nearly ideal capacitive behavior even at very high charging/discharging currents (10 A g−1) and cell potential scan rates (500 mV s−1). The EDLCs completed from SgTiC-CDC materials and EtMeImBF4 and Et3MeNBF4 + AN show good energy efficiencies (varying from 93% to 95% at current 1 A g−1) and coulombic efficiency values exceeded 99%. Thus, the EDLCs completed are very promising devices for extremely high power/energy density applications.
M. Paalo; I. Tallo; T. Thomberg; A. Jänes; E. Lust. Enhanced Power Performance of Highly Mesoporous Sol-Gel TiC Derived Carbons in Ionic Liquid and Non-Aqueous Electrolyte Based Capacitors. Journal of The Electrochemical Society 2019, 166, A2887 -A2895.
AMA StyleM. Paalo, I. Tallo, T. Thomberg, A. Jänes, E. Lust. Enhanced Power Performance of Highly Mesoporous Sol-Gel TiC Derived Carbons in Ionic Liquid and Non-Aqueous Electrolyte Based Capacitors. Journal of The Electrochemical Society. 2019; 166 (13):A2887-A2895.
Chicago/Turabian StyleM. Paalo; I. Tallo; T. Thomberg; A. Jänes; E. Lust. 2019. "Enhanced Power Performance of Highly Mesoporous Sol-Gel TiC Derived Carbons in Ionic Liquid and Non-Aqueous Electrolyte Based Capacitors." Journal of The Electrochemical Society 166, no. 13: A2887-A2895.
Hydrogen adsorption in highly porous carbon with well-defined pores, with three different shapes, and different sizes ranging from sub-to nanometers is investigated. Using a combined approach of volumetric gas adsorption method and in-situ quasi-elastic neutron scattering method the relationship between final macroscopic intake properties, details of the local adsorbent structure and the molecular behaviour of confined hydrogen are established. It is shown that sub-nanometer pores of spherical and cylindrical shape strongly limit the diffusion of H2, and thus, enhance the H2 storage capability of carbons with well-tailored pore structure. In mesoporous carbide-derived carbon, the formation of a hydrogen layer with reduced mobility close to the pore walls is observed. With the increase in the amount of confined hydrogen and the occupation of the centre pore area, the mobility of confined hydrogen increases in a jump–like fashion. Surprisingly, the increase of hydrogen diffusion is also observed at higher hydrogen loadings, indicating that cooperative H2–H2 interactions might play a role.
Riinu Härmas; Rasmus Palm; Margarita Russina; Heisi Kurig; Veronika Grzimek; Eneli Härk; Miriam Koppel; Indrek Tallo; Maarja Paalo; Ove Oll; Jan Embs; Enn Lust. Transport properties of H2 confined in carbide-derived carbons with different pore shapes and sizes. Carbon 2019, 155, 122 -128.
AMA StyleRiinu Härmas, Rasmus Palm, Margarita Russina, Heisi Kurig, Veronika Grzimek, Eneli Härk, Miriam Koppel, Indrek Tallo, Maarja Paalo, Ove Oll, Jan Embs, Enn Lust. Transport properties of H2 confined in carbide-derived carbons with different pore shapes and sizes. Carbon. 2019; 155 ():122-128.
Chicago/Turabian StyleRiinu Härmas; Rasmus Palm; Margarita Russina; Heisi Kurig; Veronika Grzimek; Eneli Härk; Miriam Koppel; Indrek Tallo; Maarja Paalo; Ove Oll; Jan Embs; Enn Lust. 2019. "Transport properties of H2 confined in carbide-derived carbons with different pore shapes and sizes." Carbon 155, no. : 122-128.
Cost-effective methods need to be developed to lower the price of Na-ion battery (NIB) materials. This paper reports a proof-of-concept study of using a novel approach to the glycine-nitrate process (GNP) to synthesize sodium vanadium phosphate (Na3V2(PO4)3 or NVP) materials with both high-energy (102 mAh g−1 at C/20) and high-power characteristics (60 mAh g−1 at 20 C). Glucose-derived hard carbons (GDHCs) were optimized to reduce both sloping and irreversible capacity. The best results were achieved for electrodes with active material heat treated at 1400 °C and reduced Super P additive. Sloping region capacity 90 mAh g−1, irreversible capacity 47 mAh g−1, discharge capacity 272 mAh g−1 (of which plateau 155 mAh g−1) and 1st cycle coulombic efficiency (CE) 85% were demonstrated. GDHC||NVP full cell achieved 80 mAh g−1 (reversible) by NVP mass out of which 60 mAh g−1 was the plateau (3.4 V) region capacity. Full cell specific energy and energy density reached 189 Wh kg−1 and 104 Wh dm−3, respectively. After 80 cycles, including rate testing from C/20 to 10 C, the cell cycled at 65 mAh g−1 with 99.7% CE. With further optimization, this method can have very high industrial potential.
Ronald Väli; Jaan Aruväli; Meelis Härmas; Alar Jänes; Enn Lust. Glycine-Nitrate Process for Synthesis of Na3V2(PO4)3 Cathode Material and Optimization of Glucose-Derived Hard Carbon Anode Material for Characterization in Full Cells. Batteries 2019, 5, 56 .
AMA StyleRonald Väli, Jaan Aruväli, Meelis Härmas, Alar Jänes, Enn Lust. Glycine-Nitrate Process for Synthesis of Na3V2(PO4)3 Cathode Material and Optimization of Glucose-Derived Hard Carbon Anode Material for Characterization in Full Cells. Batteries. 2019; 5 (3):56.
Chicago/Turabian StyleRonald Väli; Jaan Aruväli; Meelis Härmas; Alar Jänes; Enn Lust. 2019. "Glycine-Nitrate Process for Synthesis of Na3V2(PO4)3 Cathode Material and Optimization of Glucose-Derived Hard Carbon Anode Material for Characterization in Full Cells." Batteries 5, no. 3: 56.
The adsorption characteristics and organic adlayer formation properties of bipyridine molecules at semi-metallic Sb(111) electrodes in an aqueous electrolyte solution are studied by means of in situ scanning tunnelling microscopy (STM), cyclic voltammetry and electrochemical impedance spectroscopy. The capacitance–potential response shows a small capacitance hump for 4,4′-bipyridine (BP) adsorption at the Sb(111) interface, the position of which is slightly dependent on the electrolyte pH. No such capacitance vs. potential curve feature was observed for the adsorption of 2,2′-BP at Sb(111). STM measurements show a clean initial surface structure for the 4,4′-BP system and a higher level of noise interference in the case of the 2,2′-BP│Sb(111) system. The atomic resolution of the Sb(111) structure can be measured for both 2,2′-BP and 4,4′-BP additives and the formation of adsorbed molecular rows can be observed for the 4,4′-BP additive at the Sb(111) surface. The surface coverage of the molecules and the gaps between them suggest that 4,4′-BP is adsorbed in bi-protonated form with solvated anions stabilizing the adlayer structure. The reduction of BP molecules starts negative polarization and is significantly both pH- and potential-dependent. The formation of non-structured deposits is seen as a result of this process, which is deemed to be irreversible.
Georg Gorbatovski; Ove Oll; Heili Kasuk; Piret Pikma; Enn Lust. In situ scanning tunneling microscopy study of bipyridine adsorption at semi-metallic Sb(111) plane. Electrochemistry Communications 2019, 105, 106500 .
AMA StyleGeorg Gorbatovski, Ove Oll, Heili Kasuk, Piret Pikma, Enn Lust. In situ scanning tunneling microscopy study of bipyridine adsorption at semi-metallic Sb(111) plane. Electrochemistry Communications. 2019; 105 ():106500.
Chicago/Turabian StyleGeorg Gorbatovski; Ove Oll; Heili Kasuk; Piret Pikma; Enn Lust. 2019. "In situ scanning tunneling microscopy study of bipyridine adsorption at semi-metallic Sb(111) plane." Electrochemistry Communications 105, no. : 106500.
Electrical double layer characteristics and specific adsorption of anions at Bi and Cd single crystal planes from aprotic and other non-aqueous electrolytes, as well as mixtures of surface-inactive and surface-active ionic liquids have been studied and analysed. Strong influence of sp-metal electronic characteristics (concentration of charge carriers, effective mass of electrons) on the potential of zero charge and differential capacitance values have been demonstrated. Influence of solvent chemical composition and dielectric characteristics on the surface activity and Gibbs adsorption energy values of anions at sp-metal single crystal planes has been demonstrated. Influence of ionic liquid anion composition on the specific adsorption characteristic time constant at Bi(hkl) and Cd(0001) single crystal electrodes in comparison with aprotic and non-aqueous solvent based electrolytes demonstrates the role of the solvent properties on the adsorption process characteristics. The non-aqueous solvent (acetonitrile, ethylene carbonate, propylene carbonate and gamma-butyrolactone) based electrolytes, ionic liquids and ionic liquid mixtures discussed are important electrolytes applicable in electrical double layer capacitors, secondary-ion batteries and other electrochemical devices. Appreciable increase of specific energy and power densities has been demonstrated for supercapacitors with ionic liquid electrolytes containing iodide and bromide anions, development of which was based on the adsorption data collected and discussed.
Ove Oll; Mart Väärtnõu; Georg Gorbatovski; Jinfeng Zhao; Carolin Siimenson; Liis Siinor; Karmen Lust; Tavo Romann; Piret Pikma; Enn Lust. Adsorption of anions on bismuth and cadmium single crystal plane electrodes from various solvents and ionic liquid mixtures. Electrochimica Acta 2019, 319, 895 -908.
AMA StyleOve Oll, Mart Väärtnõu, Georg Gorbatovski, Jinfeng Zhao, Carolin Siimenson, Liis Siinor, Karmen Lust, Tavo Romann, Piret Pikma, Enn Lust. Adsorption of anions on bismuth and cadmium single crystal plane electrodes from various solvents and ionic liquid mixtures. Electrochimica Acta. 2019; 319 ():895-908.
Chicago/Turabian StyleOve Oll; Mart Väärtnõu; Georg Gorbatovski; Jinfeng Zhao; Carolin Siimenson; Liis Siinor; Karmen Lust; Tavo Romann; Piret Pikma; Enn Lust. 2019. "Adsorption of anions on bismuth and cadmium single crystal plane electrodes from various solvents and ionic liquid mixtures." Electrochimica Acta 319, no. : 895-908.
EDLCs based on micro-mesoporous carbon electrodes prepared from steam and CO2-steam co-activated SiC-CDCs and room-temperature ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as an electrolyte were tested to establish the electrochemical power and energy densities and region of ideal polarizability. Cyclic voltammetry, constant current charge/discharge (CC/CD), electrochemical impedance spectroscopy (EIS) and constant power discharging methods have been applied to establish the electrochemical characteristics of EDLCs completed. The highest capacitance value of 162 F g−1 at 3.6 V has been established by EIS for the SiC-CDC material, which was activated with steam at 1000°C and cleaned with molecular H2. The capacitance values for other materials prepared using the steam activation process at different temperatures were only slightly lower. The calculated coulombic efficiency values from constant current discharge/charge data for all the systems remained within the range from 97.0 to 98.5% and from 99.3 to 100% at current densities 0.1 A g−1 and 1 A g−1, respectively. The coulombic efficiencies calculated from integrated cyclic voltammetry plots varied from 97 to 98 and from 99 to 100% at potential scan rates 5 and 50 mV s−1, respectively, showing that the steam activated SiC-CDC materials are very promising for various high energy density storage/generation applications.
E. Tee; I. Tallo; E. Lust; A. Jänes; T. Thomberg. Electrical Double Layer Capacitors Based on Steam and CO2-Steam Co-Activated Carbon Electrodes and Ionic Liquid Electrolyte. Journal of The Electrochemical Society 2019, 166, A1558 -A1567.
AMA StyleE. Tee, I. Tallo, E. Lust, A. Jänes, T. Thomberg. Electrical Double Layer Capacitors Based on Steam and CO2-Steam Co-Activated Carbon Electrodes and Ionic Liquid Electrolyte. Journal of The Electrochemical Society. 2019; 166 (8):A1558-A1567.
Chicago/Turabian StyleE. Tee; I. Tallo; E. Lust; A. Jänes; T. Thomberg. 2019. "Electrical Double Layer Capacitors Based on Steam and CO2-Steam Co-Activated Carbon Electrodes and Ionic Liquid Electrolyte." Journal of The Electrochemical Society 166, no. 8: A1558-A1567.
Mechanisms of ion insertion in hard carbon and the corresponding structural impact on the graphene layer.
Jette K. Mathiesen; Ronald Väli; Meelis Härmas; Enn Lust; Jon Fold von Bülow; Kirsten M. Ø. Jensen; Poul Norby. Following the in-plane disorder of sodiated hard carbon through operando total scattering. Journal of Materials Chemistry A 2019, 7, 11709 -11717.
AMA StyleJette K. Mathiesen, Ronald Väli, Meelis Härmas, Enn Lust, Jon Fold von Bülow, Kirsten M. Ø. Jensen, Poul Norby. Following the in-plane disorder of sodiated hard carbon through operando total scattering. Journal of Materials Chemistry A. 2019; 7 (19):11709-11717.
Chicago/Turabian StyleJette K. Mathiesen; Ronald Väli; Meelis Härmas; Enn Lust; Jon Fold von Bülow; Kirsten M. Ø. Jensen; Poul Norby. 2019. "Following the in-plane disorder of sodiated hard carbon through operando total scattering." Journal of Materials Chemistry A 7, no. 19: 11709-11717.