TY - JOUR A1 - Koyutürk, B. A1 - Farber, E. A1 - Wagner, F. A1 - Fellinger, Tim-Patrick A1 - Eisenberg, D. T1 - A simple decagram-scale synthesis of an atomically dispersed, hierarchically porous Fe–N–C catalyst for acidic ORR JF - Journal of Materials Chemistry A N2 - Carbons doped with iron and nitrogen (Fe–N–Cs) are highly promising electrocatalysts for energy conversion reactions in the oxygen, nitrogen and carbon cycles. Containing no platinum group metals, they nevertheless compete with platinum-based catalysts in crucial fuel cell reactions, such as oxygen reduction in acid. Yet deployment of Fe–N–Cs in fuel cells requires also a flow-enhancing pore structure, and a scalable synthesis procedure – a rarely-met combination of requirements. We now report such a simple synthesis of over 10 g of an Fe–N–C catalyst with high activity towards oxygen reduction in acid. Atomically-dispersed Fe–N4 active sites were designed orthogonally and simultaneously with hierarchical micro-, meso- and macroporosity, by exploiting a dual role of magnesium ions during pyrolysis. Combining the “active site imprinting” and “self-templating” strategies in a single novel magnesium iminodiacetate precursor yielded a catalyst with high specific surface area (SSA > 1600 m2 g−1), a flow-enhancing hierarchical porosity, and high relative abundance of the most desirable D1-type Fe–N4 sites (43%, by Mössbauer spectroscopy at 4.2 K). Despite the relatively low iron contents, the catalysts feature halfwave potentials up to 0.70 V vs. RHE at pH 1 and a mass activity of 1.22 A g−1 at 0.8 V vs. RHE in RDE experiments. Thanks to the simple and scalable synthesis, this active and stable catalyst may serve as a workhorse in academic and industrial research into atomically-dispersed ORR electrocatalysis. KW - Catalysis KW - Fe-N-C catalysts KW - Fuel Cells KW - Electrochemistry PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550113 DO - https://doi.org/10.1039/d2ta00925k SN - 2050-7488 SP - 1 EP - 10 PB - Royal Society of Chemistry AN - OPUS4-55011 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Titirici, M. A1 - Baird, S. G. A1 - Sparks, T. D. A1 - Yang, S. M. A1 - Brandt-Talbot, A. A1 - Hosseinaei, O. A1 - Harper, D. P. A1 - Parker, R. M. A1 - Vignolini, S. A1 - Berglund, L. A. A1 - Li, Y. A1 - Gao, H.-L. A1 - Mao, L.-B. A1 - Yu, S.-H. A1 - Díez, N. A1 - Ferrero, G. A. A1 - Sevilla, M. A1 - Szilágyi, P. Á. A1 - Stubbs, C. J. A1 - Worch, J. C. A1 - Huang, Y. A1 - Luscombe, C. K. A1 - Lee, K.-Y. A1 - Luo, H. A1 - Platts, M. J. A1 - Tiwari, D. A1 - Kovalevskiy, D. A1 - Fermin, D. J. A1 - Au, H. A1 - Alptekin, H. A1 - Crespo-Ribadeneyra, M. A1 - Ting, V. P. A1 - Fellinger, Tim-Patrick A1 - Barrio, J. A1 - Westhead, O. A1 - Roy, C. A1 - Stephens, I. E. L. A1 - Nicolae, S. A. A1 - Sarma, S. C. A1 - Oates, R. P. A1 - Wang, C.-G. A1 - Li, Z. A1 - Loh, X. J. A1 - Myers, R. J. A1 - Heeren, N. A1 - Grégoire, A. A1 - Périssé, C. A1 - Zhao, X. A1 - Vodovotz, Y. A1 - Earley, B. A1 - Finnveden, G. A1 - Björklund, A. A1 - Harper, G. D. J. A1 - Walton, A. A1 - Anderson, P. A. T1 - The sustainable materials roadmap JF - Journal of physics: Materials N2 - Our ability to produce and transform engineered materials over the past 150 years is responsible for our high standards of living today, especially in the developed economies. Yet, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of economy, energy, and climate. We are at the point where something must drastically change, and it must change NOW. We must create more sustainable materials alternatives using natural raw materials and inspiration from Nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments based on reliable and relevant data to quantify sustainability. KW - Electrochemistry KW - Fe-N-C catalysts KW - Fuel cells KW - Catalysis PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550126 DO - https://doi.org/10.1088/2515-7639/ac4ee5 SN - 2515-7639 VL - 5 IS - 3 SP - 1 EP - 98 PB - IOP Publishing CY - Bristol AN - OPUS4-55012 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fritsch, Tobias A1 - Kurpiers, J. A1 - Roland, S. A1 - Tokmoldin, N. A1 - Shoaee, S. A1 - Ferron, T. A1 - Collins, B. A. A1 - Janietz, S. A1 - Vandewal, K. A1 - Fritsch, D. T1 - On the Interplay between CT and Singlet Exciton Emission in Organic Solar Cells with Small Driving Force and Its Impact on Voltage Loss JF - Advanced Energy Materials N2 - The interplay between free charge carriers, charge transfer (CT) states and singlet excitons (S1) determines the recombination pathway and the resulting open circuit voltage (VOC) of organic solar cells. By combining a well-aggregated low bandgap polymer with different blend ratios of the fullerenes PCBM and ICBA, the energy of the CT state (ECT) is varied by 130 meV while leaving the S1 energy of the polymer (ES1) unaffected. It is found that the polymer exciton dominates the radiative properties of the blend when ECT approaches ES1, while the VOC remains limited by the non-radiative decay of the CT state. It is concluded that an increasing strength of the exciton in the optical spectra of organic solar cells will generally decrease the non-radiative voltage loss because it lowers the radiative VOC limit (VOC,rad), but not because it is more emissive. The analysis further suggests that electronic coupling between the CT state and the S1 will not improve the VOC, but rather reduce the VOC,rad. It is anticipated that only at very low CT state absorption combined with a fairly high CT radiative efficiency the solar cell benefit from the radiative properties of the singlet excitons. KW - Organic Solar Cell KW - Open Circuit Voltage KW - Voltage Loss KW - Ternary PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552518 DO - https://doi.org/10.1002/aenm.202200641 SN - 1614-6832 SP - 1 EP - 11 PB - Wiley-VCH CY - Weinheim AN - OPUS4-55251 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Stamm, Michael A1 - Krankenhagen, Rainer T1 - Weather-dependent passive thermography of unheated wind turbine blades T2 - Proceedings, Thermosense: Thermal Infrared Applications XLIV N2 - Up to now, the inspection of wind turbines with industrial climbers has been considered ”state of the art”. However, ever-larger wind turbines and advancing digitization make modern and automated inspection methods indispensable. Passive thermography can serve as such a digital and atomized method while it is well known for its applications in the inspection of buildings or electrical circuits. However, its application relies on thermal gradients in the inspected object such that a temperature contrast exists between damaged and sound areas. This also holds for unheated structures like rotor blades of wind turbines which show no intrinsic temperature gradient and can hardly be heated. Under certain weather conditions with sufficient solar loading and diurnal temperature variations, passive thermography is suitable for the in-service inspection of rotor blades. However, for a reliable use of passive thermography on ”thermal passive” components, the incorporation of these environmental conditions in the planning and evaluation of thermal inspections is crucial. Additionally, the complex inner structure of wind turbine blades in comparison to other objects and buildings require a specific method referencing the individual rotor blades to each other. This allows the distinction between the thermal response of design-specific structural features and damages or irregularities between the three blades. We show thermal signatures of damage in rotor blades and contrast them with structural characteristics by comparing the three blades. In addition to measurements in industrial environments, laboratory measurements are shown and compared to simulations. The long-term goal is to simulate the influence of different weather parameters and thus gain a better understanding of measurements in the field. The results shown here can be seen as one step towards industrial application. T2 - SPIE Defense + Commercial Sensing CY - Orlando, Florida, USA DA - 03.04.2022 KW - Passive thermography KW - Wind energy KW - FEM simulations PY - 2022 DO - https://doi.org/10.1117/12.2618740 VL - 12109 SP - 1 EP - 8 PB - Society of Photo-Optical Instrumentation Engineers (SPIE) AN - OPUS4-54943 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Segovia, J. J. A1 - Tuma, Dirk A1 - Lozano-Martín, D. A1 - Moreau, A. A1 - Martín, M. C. A1 - Vega-Maza, D. T1 - Speed of sound data and acoustic virial coefficients of two binary (N2 + H2) mixtures at temperatures between (260 and 350) K and at pressures between (0.5 and 20) MPa JF - Journal of Chemical Thermodynamics N2 - This work aims to address the technical concerns related to the thermodynamic characterization of gas mixtures blended with hydrogen for the implementation of hydrogen as a new energy vector. For this purpose, new experimental speed of sound measurements have been done in gaseous and supercritical phases of two binary mixtures of nitrogen and hydrogen using the most accurate technique available, i.e., the spherical acoustic resonator, yielding an experimental expanded (k = 2) uncertainty of only 220 parts in 106 (0.022%). The measurements cover the pressure range between (0.5 and 20) MPa, the temperature range between (260 and 350) K, and the composition range with a nominal mole percentage of hydrogen of (5 and 10) mol%, respectively. From the speed of sound data sets, thermophysical properties that are relevant for the characterization of the mixture, namely the second βa and third γa acoustic virial coefficients, are derived. These results are thoroughly compared and discussed with the established reference mixture models valid for mixtures of nitrogen and hydrogen, such as the AGA8-DC92 EoS, the GERG-2008 EoS, and the recently developed adaptation of the GERG-2008 EoS, here denoted GERG-H2_improved EoS. Special attention has been given to the effect of hydrogen concentration on those properties, showing that only the GERG-H2_improved EoS is consistent with the data sets within the experimental uncertainty in most measuring conditions. KW - Speed of sound KW - Acoustic resonance KW - Binary gas mixture PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-551482 DO - https://doi.org/10.1016/j.jct.2022.106791 SN - 0021-9614 VL - 171 SP - 1 EP - 13 PB - Elsevier B. V. CY - Amsterdam AN - OPUS4-55148 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sachse, René A1 - Hodoroaba, Vasile-Dan A1 - Kraehnert, R. A1 - Hertwig, Andreas T1 - Multilevel effective material approximation for modeling ellipsometric measurements on complex porous thin films JF - Advanced optical technologies N2 - Catalysts are important components in chemical processes because they lower the activation energy and thus determine the rate, efficiency and selectivity of a chemical reaction. This property plays an important role in many of today’s processes, including the electrochemical splitting of water. Due to the continuous development of catalyst materials, they are becoming more complex, which makes a reliable evaluation of physicochemical properties challenging even for modern analytical measurement techniques and industrial manufacturing. We present a fast, vacuum-free and non-destructive analytical approach using multi-sample spectroscopic ellipsometry to determine relevant material parameters such as film thickness, porosity and composition of mesoporous IrOx–TiOy films. Mesoporous IrOx–TiOy films were deposited on Si wafers by sol–gel synthesis, varying the composition of the mixed oxide films between 0 and 100 wt%Ir. The ellipsometric modeling is based on an anisotropic Bruggeman effective medium approximation (a-BEMA) to determine the film thickness and volume fraction of the material and pores. The volume fraction of the material was again modeled using a Bruggeman EMA to determine the chemical composition of the materials. The ellipsometric fitting results were compared with complementary methods, such as scanning electron microscopy (SEM), electron probe microanalysis (EPMA) as well as environmental ellipsometric porosimetry (EEP). KW - Electrochemical catalysts KW - Mixed metal oxide KW - Multi-sample analysis KW - Spectroscopic ellipsometry KW - Thin mesoporous films PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-551026 DO - https://doi.org/10.1515/aot-2022-0007 SN - 2192-8584 SN - 2192-8576 VL - 11 IS - 3-4 (Topical issue: Ellipsometry) SP - 137 EP - 147 PB - De Gruyter CY - Berlin AN - OPUS4-55102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Jiang, C. A1 - Xie, G. A1 - Wu, Dejian A1 - Yan, T. A1 - Chen, S. A1 - Zhao, P. A1 - Wu, Z. A1 - Li, W. T1 - Experimental investigation on an energy-efficient floor heating system with intelligent control: A case study in Chengdu, China JF - Case Studies in Thermal Engineering N2 - The space heating system accounts for 20%~50% of building energy consumption, and may lead to energy waste due to unreasonable controls. In this study, an energy-efficient floor heating system with intelligent control was proposed to improve energy efficiency of the system. In order to validate the concept of the proposed intelligent control, an experimental system was designed and constructed in Chengdu, China. Temperature, control cycle and energy consumption were then studied under different control strategies. The result shows that a larger flow rate of supply water will result in a longer control cycle and a lower control frequency, i.e., the average control cycle at 7 L min−1 is 1.7 h during the test day, while it is 1.5 h at 5 L min−1. Moreover, adopting water with a higher temperature and flow rate could achieve a higher efficiency of the system. The energy consumptions in case 1 (5 L min−1, 50 °C), case 2 (5 L min−1, 55 °C), case 5 (7 L min−1, 55 °C) and case 6 (7 L min−1, 60 °C) are 4746 kJ, 3534 kJ, 3093 kJ and 3028 kJ, respectively. Based on the experimental data, the supply water temperature is suggested to set lower than 60 °C considering human comfort. KW - Floor heating KW - Intelligent control KW - Experimental KW - Energy consumption KW - Control strategy PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-550522 DO - https://doi.org/10.1016/j.csite.2021.101094 SN - 2214-157X VL - 26 SP - 1 EP - 14 PB - Elsevier Ltd. AN - OPUS4-55052 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hoffmann, H A1 - Paulisch, M C A1 - Gebhard, M A1 - Osiewacz, J A1 - Kutter, M A1 - Hilger, A A1 - Arlt, T A1 - Kardjilov, N A1 - Ellendorff, B A1 - Beckmann, F A1 - Markötter, Henning A1 - Luik, M A1 - Turek, T A1 - Manke, I A1 - Roth, C T1 - Development of a Modular Operando Cell for X-ray Imaging of Strongly Absorbing Silver-Based Gas Diffusion Electrodes JF - Journal of The Electrochemical Society N2 - Metal-based gas diffusion electrodes are utilized in chlor-alkali electrolysis or electrochemical reduction of carbon dioxide, allowing the reaction to proceed at high current densities. In contrast to planar electrodes and predominantly 2D designs, the industrially required high current densities can be achieved by intense contact between the gas and liquid phase with the catalytically active surfaces. An essential asset for the knowledge-based design of tailored electrodes is therefore in-depth information on electrolyte distribution and intrusion into the electrode’s porous structure. Lab-based and synchrotron radiography allow for monitoring this process operando. Herein, we describe the development of a cell design that can be modularly adapted and successfully used to monitor both the oxygen reduction reaction and the electrochemical reduction of CO2 as exemplary and currently very relevant examples of gas-liquid reactions by only minor modifications to the cell set-up. With the reported cell design, we were able to observe the electrolyte distribution within the gas diffusion electrode during cell operation in realistic conditions. KW - X-Ray imaging KW - Gas diffusion electrodes KW - Operando cell PY - 2022 DO - https://doi.org/10.1149/1945-7111/ac6220 VL - 169 IS - 4 SP - 044508 PB - IOP science AN - OPUS4-55027 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tuma, Dirk A1 - Shafi, P. M. A1 - Mohapatra, D. A1 - Reddy, V. P. A1 - Dhakal, G. A1 - Kumar, D. R. A1 - Brousse, T. A1 - Shim, J.-J. T1 - Sr- and Fe-substituted LaMnO3 Perovskite: Fundamental insight and possible use in asymmetric hybrid supercapacitor JF - Energy Storage Materials N2 - The symmetry or structural stability of ABO3-type perovskite oxides depends largely on the size of ‘A’ and ‘B’ cations, which determines the material properties. The partial substitution of these cations may be used to tune these properties. The ionic sizes and valence states of the cations play an important role in improving the prop- erties of perovskite. In this study, the substitution of La3+ with Sr2+ with a larger ionic radius and Mn3+ with Fe3+ with a similar ionic radius favored both the crystal symmetry and the mixed ionic–electronic conductivity of the perovskite. Electrodes based on La0.7Sr0.3Mn0.5Fe0.5O3 (LSMFO55) exhibited a faradaic behavior with a specific capacity of 330 C g−1 (92 mAh g−1 ) at 12C rate, while this electrode maintained a capacity of 259 C g−1 at 240C (charge or discharge in 15 s). Additionally, exohedral carbon nano-onions (CNO) were introduced as a negative electrode to design an asymmetric hybrid supercapacitor (AHS) with a widened cell voltage. The use of CNO as a negative electrode in the AHS improved the rate capability drastically compared to the use of rGO. This device maintained a good energy density even at an extra-high charging rate (600C) owing to its outstanding rate capability. The high-rate performance of the LSMFO55//CNO AHS can be elucidated by successful fabrication with a mixed ionic–electronic conductive positive electrode and a CNO negative electrode. Tuning the electronic and ionic conductivities by cationic substitution and adopting an appropriate carbon-derived negative electrode (such as CNO) can provide a practical high-rate hybrid device using various perovskites. KW - Perovskite KW - Carbon nano-onion KW - Supercapacitor PY - 2022 DO - https://doi.org/10.1016/j.ensm.2021.11.028 SN - 2405-8297 VL - 45 SP - 119 EP - 129 PB - Elsevier B. V. CY - Amsterdam AN - OPUS4-54882 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Porta-Velilla, L. A1 - Turan, N. A1 - Cubero, Á. A1 - Shao, W. A1 - Li, H. A1 - de la Fuente, G.F. A1 - Martínez, E. A1 - Larrea, Á. A1 - Castro, M. A1 - Koralay, H. A1 - Çavdar, Ş. A1 - Bonse, Jörn A1 - Angurel, L.A. T1 - Highly Regular Hexagonally-Arranged Nanostructures on Ni-W Alloy Tapes upon Irradiation with Ultrashort UV Laser Pulses JF - Nanomaterials N2 - Nickel tungsten alloy tapes (Ni—5 at% W, 10 mm wide, 80 µm thick, biaxially textured) used in second-generation high temperature superconductor (2G-HTS) technology were laser-processed in air with ultraviolet ps-laser pulses (355 nm wavelength, 300 ps pulse duration, 250–800 kHz pulse repetition frequency). By employing optimized surface scan-processing strategies, various laser-generated periodic surface structures were generated on the tapes. Particularly, distinct surface microstructures and nanostructures were formed. These included sub-wavelength-sized highly-regular hexagonally-arranged nano-protrusions, wavelength-sized line-grating-like laser-induced periodic surface structures (LIPSS, ripples), and larger irregular pyramidal microstructures. The induced surface morphology was characterized in depth by electron-based techniques, including scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), cross-sectional transmission electron microscopy (STEM/TEM) and energy dispersive X-ray spectrometry (EDS). The in-depth EBSD crystallographic analyses indicated a significant impact of the material initial grain orientation on the type of surface nanostructure and microstructure formed upon laser irradiation. Special emphasis was laid on high-resolution material analysis of the hexagonally-arranged nano-protrusions. Their formation mechanism is discussed on the basis of the interplay between electromagnetic scattering effects followed by hydrodynamic matter re-organization after the laser exposure. The temperature stability of the hexagonally-arranged nano-protrusion was explored in post-irradiation thermal annealing experiments, in order to qualify their suitability in 2G-HTS fabrication technology with initial steps deposition temperatures in the range of 773–873 K. KW - Laser-induced periodic surface structures (LIPSS) KW - Ultrashort laser processing KW - Hexagonally-arranged nano-protrusions KW - Second-generation high temperature superconductor technology KW - Electron microscopy PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-552551 DO - https://doi.org/10.3390/nano12142380 SN - 2079-4991 VL - 12 IS - 14 SP - 1 EP - 23 PB - MDPI CY - Basel, Switzerland AN - OPUS4-55255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -