Heisi Kurig

Electrochemical Characteristics of Carbide-Derived Carbon ∣ 1 -Ethyl-3-methylimidazolium Tetrafluoroborate Supercapacitor Cells

Supercapacitor (SC) cells based on microporous titanium carbide-derived carbon [C(TiC)] electrodes in room temperature ionic liquid (I-ethyl-3-methylimidazolium tetrafluoroborate) have been tested by cyclic voltammetry, constant current charge/discharge, and electrochemical impedance methods at temperatures from 25 to 80°C. The limits of ideal polarizability, low frequency limiting capacitance and series resistance, time constant, complex power components, time stability, and other characteristics have been calculated and discussed. The influence of temperature on the cell capacitance, characteristic time constant values, and region of ideal polarizability has been analyzed. The comparatively high energy (40 Wh kg -1 ) and power (130 kW kg -1 ) densities per active C(TiC) weight have been calculated, weakly depending on temperature, if T ≤ 59°C. A comparison of the results to the corresponding data for the C(TiC)|1 M(C 2 H 5 ) 3 CH 3 NBF 4 + acetonitrile system indicates that 1-ethyl-3-methylimidazolium tetrafluoroborate|carbide-derived carbon SC cells demonstrate lower power densities, a narrower region of ideal polarizability, and a lower constant current cyclability at higher charge/discharge rates.

Influence of Mesoporous Separator Properties on the Parameters of Electrical Double-Layer Capacitor Single Cells

The specific surface area, pore size distribution function, micropore and mesopore volume, and area values have been obtained by gas adsorption/absorption method for various separator materials prepared from polypropylene, cellulose, and poly(vinylidene fluoride). Electrical double-layer capacitors (EDLCs) based on the two identical ideally polarizable nanoporous carbide-derived carbon electrodes and different mesoporous separator materials in 1 M (C 2 H 5 ) 3 CH 3 NBF 4 acetonitrile solution have been tested by cyclic voltammetry and electrochemical impedance methods. The limits of ideal polarizability, low-frequency limiting capacitance and series resistance, time constant, complex power components, and electrolyte conductivity in the separator matrix have been obtained and discussed. The model of Srinivasan and Weidner [J. Electrochem. Soc., 146, 1650 (1999)] has been modified by introducing into it the very high-frequency constant phase and charge-transfer resistance elements. The applicability limits of the modified model have been tested. Noticeable influence of separator chemical composition, thickness, specific surface area, and pore size distribution on the characteristics of the EDLC single cells have been found.

Advanced nanostructured carbon materials for electrical double layer capacitors

Thermodynamical and electrochemical characteristics for the non-aqueous electrolyte nanostructured carbide-derived carbon (CDC), activated carbon cloth (ACC) or commercial activated nanoporous carbon RP-20 (from Kuraray Chemical Co.) interface have been established by XRD, Raman spectroscopy, BET, cyclic voltammetry and electrochemical impedance spectroscopy. The gas adsorption measurement data have been used for the obtaining the specific surface area, pore size distribution, nanopore volume and other characteristics, dependent on the nanostructured carbon used (nanopores are pores in the range of 2 nm and below — i.e. micropores according to IUPAC classification).

Neutron Scattering Applications to Hydrogen Storage Materials

Volume 27 • Number 1 • 2016 Neutron News 14 A Fourth International School on Neutron Scattering Applications to Hydrogen Storage Materials was held August 17–26 in Helmholtz-Zentrum-Berlin (HZB). This summer school is organized in cooperation by the HZB and the University of Tartu (UT, Estonia) with the main aim to give an overview of the hydrogen energy technology, storage materials, research techniques and the most important highlights form the latest discoveries in science. Eight students from all over the World (as originating from Germany, Russia, Estonia, Italy, Romania, Slovakia, Mexico, and Kazakhstan) participated the courses and practical works. Lectures were given by Margarita Russina (HZB), Heisi Kurig (UT), D. Wallacher (HZB), R. Svetogorov (NRC Kurchatov Institute), and D. Többens (HZB) covering a large variety of subjects. At the beginning, the basic facts about hydrogen economy, use as a fuel, and storage were introduced to students. Then an overview of hydrogen storage materials, like amorphous carbons, hydrides, and metallic organic frame works, was given. Also, different experimental techniques for research were covered to give a complete summary on the topic of summer school. The lectures were accompanied by various practical works. Students carried out gas adsorption measurements and analysis of obtained data on a metal-organic frame work (Cu3BTC2). The aim was to characterize the material and measure the hydrogen up-take of the material. Also, neutron diffraction experiment was performed under the supervision of Dr. Alexandra Franz on instrument FIREPOD. The diffraction pattern of (Cu3BTC2) was measured at different hydrogen pressures to give students the possibility to comprehend how neutron scattering experiments are planned and performed for metal-organic frameworks. Previously measured diffraction pattern of another MOF–CAU1 was used to make a structure refi nement. The aim was to localize and refi ne positions of the D2 molecules inside the structure. The students got two different patterns measured at pressures corresponding to a different number of absorbed deuterium molecules. They also got two structure solutions for each pressure as a starting model for further refi nement. Students were asked to compare the results, given by the different starting models, choose the best of them and describe it. All students achieved reasonable results and learned to make the refi nements of such structures in a relatively short period of time. The summer school did not lack social events or the possibility to evolve scientifi c discussions. On the Wednesday (August 19th) an evening gathering was organized along with a poster session. There students had Neutron Scattering Applications to Hydrogen Storage Materials

3rd School on Neutron Scattering Applications to Hydrogen Storage Materials

Neutron News Volume 26 • Number 1 • 2015 17 T third international school on “Neutron Scattering Applications to Hydrogen Storage Materials” was held from August 20–29, 2014 at the Helmholtz-Zentrum Berlin (HZB). The school was organized jointly by the HZB, University of Potsdam (Germany) and the University of Tartu (Estonia) The team in charge included Margarita Russina (HZB) and Moritz-C. Schlegel (HZB) with help of their colleagues Daniel Többens (HZB), Dirk Wallacher (HZB) and Heisi Kurig (University of Tartu, Estonia) The goal of the school was to give a basic knowledge of neutron scattering and diffraction, to show how these techniques can be applied and what kind of information can be obtained. 13 PhD students and postdocs from over the world were invited to the HZB campus to participate on lectures and hands on practical exercises. In the beginning of the school small projects were distributed to the participants they had to complete using their new knowledge and skills. In the courses the students were fi rst given an overview of the hydrogen storage technology with particular focus on materials-based storage. In this way, relevant basics such as energy density, kinetics and reversibility were introduced and different mechanisms of storage explained. The properties of various classes of hydrogen storage materials were illustrated by Margarita Russina and the guest lecturers of the school Heisi Kurig and Helge Reinsch from University of Oslo, Norway. Afterwards the students learned the fundamentals of neutron scattering, in particular diffraction methods. Using various examples, Moritz-C. Schlegel and Daniel Többens demonstrated how neutron scattering and diffraction can be applied to analysis of hydrogen storage materials and which kind of questions these studies can answer. Finally, an introduction about the applications and the principles of gas-sorption analysis were given by lecture of Dirk Wallacher. A student Roman Svetogorov from the NRC Kurchatov Institute in Moscow, Russia, commented the lectures: “It was very useful and I learned a lot about the methods and materials I did not know before.” The lectures were complemented by practical exercises using gas adsorption and in-situ diffraction analysis at the HZB synchrotron BESSY II. Using a famous fl exible metallic organic framework as an example of storage materials, the students fi rst investigated the gas sorption properties at various temperatures. Based on this information they conducted in-situ Xray diffraction analysis at the X-ray diffractometer KMC-2. Daniel Többens gave an introduction in structure refi nement techniques and explained the advantages of combining ab-initio refi nements and the Rietveld method. Applying these techniques to the data measured, Moritz-C. Schlegel explained them how to determine and refi ne the positions of confi ned hydrogen inside the porous framework. “It is the real work you do if you do measurements at a synchrotron [...] and we could see in real time how the measurements are done, so that was really interesting and useful,” said a student Luca Silva from FRM II in Munich, Germany. On the last day of the school the participants gave short talks about the collected data and results, followed by discussions and reports of their impressions during the last days. The next international school “Neutron Scattering Applications to Hydrogen Storage Materials” will be held again September 2015 at the HZB (see also Neutron News events calendar). We kindly invite you to participate and hope to see you in Berlin!