Bochum, Germany
Bochum, Germany

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Rincon R.A.,Ruhr University Bochum | Battistel A.,Ruhr University Bochum | Ventosa E.,Ruhr University Bochum | Chen X.,Ruhr University Bochum | And 3 more authors.
ChemSusChem | Year: 2015

Cavity microelectrodes were used as a binder-free platform to evaluate oxygen evolution reaction (OER) electrocatalysts with respect to gas bubble formation and departure. Electrochemical noise measurements were performed by using RuO2 as a benchmark catalyst and the perovskite La0.58Sr0.4Fe0.8Co0.2O3 as a non-noble metal OER catalyst with lower intrinsic conductivity. Changes in the current during the OER originate from variations in electrolyte resistance during the formation of the gas phase and partial coverage of the active area. Fluctuations observed in current and conductance transients were used to establish the contribution from the ohmic overpotential and to determine the characteristic frequency of oxygen evolution. The proposed quantitative determination of gas bubble growth and departure opens up the route for a rational interface design by considering gas bubble growth and departure as a main contributing factor to the overall electrocatalytic activity at high current densities. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Moellmer J.,Institute fur Nichtklassische Chemie E.V. | Moeller A.,Institute fur Nichtklassische Chemie E.V. | Dreisbach F.,Universitatsstr 142 | Glaeser R.,Institute fur Nichtklassische Chemie E.V. | And 2 more authors.
Microporous and Mesoporous Materials | Year: 2011

High pressure adsorption phenomena are discussed for different gases on HKUST-1 (Cu3(BTC)2, commercially available product BasoliteTM C300). Sorption isotherms for hydrogen, nitrogen, methane and carbon dioxide on HKUST-1 were measured in the temperature range of 273-343 K and at pressures up to 50 MPa. The calculated surface excess adsorption capacities for all four adsorptive are one of the highest reported in the literature for HKUST-1 samples. All surface excess data were further calculated from the experimental data by using the helium buoyancy correction. A detailed description was given. Also a procedure to calculate the absolute amount adsorbed from the surface excess amount by using two different models is shown. Using one model, the density and the volume of the adsorbed phase can be calculated. The density of the adsorbed phase ρads corresponds to the liquid density of the adsorptive at its boiling point ρ liq,BP. In case of hydrogen no excess maximum was found up to 50 MPa, so that one model could not be applied. Finally, the isosteric heat of adsorption for each gas was calculated by using the Clausius-Clapeyron equation. © 2010 Elsevier Inc. All rights reserved.


Lincke J.,University of Leipzig | Lassig D.,University of Leipzig | Moellmer J.,Institute fur Nichtklassische Chemie E.V. | Reichenbach C.,University of Leipzig | And 6 more authors.
Microporous and Mesoporous Materials | Year: 2011

Synthesis and crystal structure of a novel copper-based MOF material are presented. The tetragonal crystal structure of [∞3(Cu4( μ4-O)(μ2-OH)2(Me2trzpba) 4] possesses a calculated solvent-accessible pore volume of 57%. Besides the preparation of single crystals, synthesis routes to microcrystalline materials are reported. While PXRD measurements ensure the phase purity of the as-synthesized material, TD-PXRD measurements and coupled DTA-TG-MS analysis confirm the stability of the network up to 230 °C. The pore volume of the microcrystalline material determined by nitrogen adsorption at 77 K depends on the synthetic conditions applied. After synthesis in DMF/H2O/MeOH the pores are blocked for nitrogen, whereas they are accessible for nitrogen after synthesis in H2O/EtOH and subsequent MeOH Soxhleth extraction. The corresponding experimental pore volume was determined by nitrogen adsorption to be VPore=0.58cm3g-1. In order to characterize the new material and to show its adsorption potential, comprehensive adsorption studies with different adsorptives such as nitrogen, argon, carbon dioxide, methanol and methane at different temperatures were carried out. Unusual adsorption-desorption isotherms with one or two hysteresis loops are found - a remarkable feature of the new flexible MOF material. © 2010 Elsevier Inc.


Noth S.,Universitatsstr 142 | Edelbrunner J.,Universitatsstr 142 | Iossifidis I.,Ruhr University Bochum
IEEE Conference on Intelligent Transportation Systems, Proceedings, ITSC | Year: 2012

Advanced Driver Assistant Systems act, by definition in natural, often poorly structured, environments and are supposed to closely interact with human operators. Both, natural environments as well as human behaviour have no inherent metric and can not be modelled/measured in the classical way physically plausibly behaving systems are described. © 2012 IEEE.


Mishra P.,Indian Institute of Technology Guwahati | Mekala S.,Indian Institute of Technology Guwahati | Dreisbach F.,Universitatsstr 142 | Mandal B.,Indian Institute of Technology Guwahati | Gumma S.,Indian Institute of Technology Guwahati
Separation and Purification Technology | Year: 2012

In this work, we report the gas adsorption properties of a zinc based metal organic framework, (Zn 2(bdc) 2(dabco)(H 2O) 0.5(DMF) 4), more commonly known as ZnDABCO. Equilibrium adsorption isotherms for four industrially relevant gases (CO 2, CO, CH 4 and N 2) were measured up to 26 bar at three different temperatures (294, 314 and 350 K) using a standard gravimetric method. The isotherms were modeled using modified virial equation. Ideal Adsorbed Solution Theory (IAST) was used to predict selectivity of binary mixtures. The results indicate that absence of open metal centers in the ZnDABCO framework, results in lower capacities and adsorption enthalpies when compared to MOFs like CuBTC and MIL-101. The small values of adsorption enthalpy and Henry constant should make it easier to regenerate the adsorbent. IAST predicts an increase in the selectivity of CO 2 over the other three gases, with increasing pressure and CO 2 mole-fraction; this phenomenon is attributed to the increase in lateral interactions between the adsorbed CO 2 molecules. IAST predictions also indicate that this framework shows selectivity for CH 4 over CO. © 2011 Elsevier B.V. All rights reserved.


Harte R.,University of Wuppertal | Hoffer R.,Ruhr University Bochum | Kratzig W.B.,Kratzig and Partner Ingenieurgesellschaft mbH | Mark P.,Ruhr University Bochum | Niemann H.-J.,Universitatsstr 142
Engineering Structures | Year: 2013

Solar updraft power technology will generate highly sustainable electricity in world-wide deserts in future. It will overcome certain deficits of present renewable energy technologies. In several countries, such power plants are in pre-design stage, forming an important contribution of structural engineering to future energy supply. The present manuscript starts with the working principles of solar updraft power plants, followed by explaining climatic and wind-technologic design assumptions. Then the central solar updraft chimney - the power tower - is treated in more detail: a thin ring-stiffened RC shell of extreme height, forming the utmost structural challenge of such plants. This part is followed by technical requirements for the collector constructions, by far the largest glass-covered areas ever built, and of the wind-loading on the glazing. Then, further design aspects are extracted by the durability requirements for at least 100. years of operation in extreme desert climates. The paper closes with some cost estimates for the generated electricity. © 2013 Elsevier Ltd.


Nebel M.,Ruhr University Bochum | Nebel M.,Universitatsstr 142 | Erichsen T.,Universitatsstr 142 | Schuhmann W.,Ruhr University Bochum
Beilstein Journal of Nanotechnology | Year: 2014

Multidimensional shearforce-based constant-distance mode scanning electrochemical microscopy (4D SF/CD-SECM) was utilized for the investigation of the activity distribution of oxygen reduction catalysts. Carbon-supported Pt model catalyst powders have been immobilized in recessed microelectrodes and compared to a spot preparation technique. Microcavities serve as platform for the binder-free catalyst sample preparation exhibiting beneficial properties for constant-distance mode SECM imaging concerning modified surface area and catalyst loading. The integration of the redox competition mode of SECM into the detection scheme of the 4D SF/CD mode is demonstrated for specifically adapting high-resolution SECM experiments to powder-based catalyst preparations. © 2014 Nebel et al.


Wollmann P.,TU Dresden | Leistner M.,Fraunhofer Institute for Material and Beam Technology | Grahlert W.,Fraunhofer Institute for Material and Beam Technology | Throl O.,TU Dresden | And 3 more authors.
Microporous and Mesoporous Materials | Year: 2012

The demand for fast screening methods in modern materials chemistry led to the development of a room temperature operated high-throughput tool for adsorption screening. Within five minutes a porosity screening of a large sample pool can be realized. Using a variety of different porous materials (activated carbons, porous polymers, metal-organic frameworks, zeolites) and the test gas n-butane, the reliability of the new instrument is shown. Furthermore, possible applications in the determination of n-butane capacities and BET surface areas are given as well as the application in synthesis or product control. The presented data exhibit high quality factors for the correlation of integrated signal intensity (heat of adsorption) and specific surface areas (above 0.97). As an example for the applicability of other gases that can be used with this tool, screening measurements using cyclohexane as test gas are also presented. The developed automated screening tool is an important step to overcome the bottle-neck between high-throughput syntheses technologies developed in the last decades and measurement of adsorption properties. © 2011 Elsevier Inc. All rights reserved.


Wollmann P.,TU Dresden | Leistner M.,Fraunhofer Institute for Material and Beam Technology | Stoeck U.,TU Dresden | Grunker R.,TU Dresden | And 8 more authors.
Chemical Communications | Year: 2011

A new tool (Infrasorb-12) for the screening of porosity is described, identifying high surface area materials in a very short time with high accuracy. Further, an example for the application of the tool in the discovery of new cobalt-based metal-organic frameworks is given. © 2011 The Royal Society of Chemistry.


Niemann H.-J.,Ruhr University Bochum | Diburg S.,Universitatsstr 142
Computers and Structures | Year: 2013

The "Comité Européen de Normalisation" developed unified technical standards for application within the EU. The Eurocode EN 1990 is the basic document regarding the requirements for structural reliability. The code is based on the partial factor method. The Gumbel Type I probability distribution is applied to predict extreme values of climatic actions. The authors extend this approach to the generalised Gumbel distribution allowing including an upper limit of the climatic variable. For estimating the distribution parameters, a statistical methodology called ProGumbel has been developed. The implications for statistical analyses of wind speeds and determination of design wind speeds are discussed. © 2013 Elsevier Ltd.

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