Electrodeposition of cuprous oxide on a free-standing porous Cu framework for photoelectrochemical water splitting. - In: Meeting abstracts, ISSN 2151-2043, Bd. MA2020-02 (2020), 15, 1425
https://doi.org/10.1149/MA2020-02151425mtgabs
Investigation of the reaction kinetics of chromium(III) ions with carboxylic acids in aqueous solutions and the associated effects on chromium deposition. - In: Journal of the Electrochemical Society, ISSN 1945-7111, Bd. 167 (2020), 16, 162509, insges. 8 S.
Electroplated chromium is an important industrial coating. Both in the decorative and functional field, research is being carried out to develop trivalent chromium electrolytes. In this work, the interaction between CrIII ions and carboxylic acids (malonic acid, malic acid, oxalic acid and glycolic acid) is investigated. The use of carboxylic acids to improve the current efficiency in trivalent chromium plating baths has been known for a long time. But the thermodynamics and kinetics of the associated complexing reactions are not well understood. It is shown that the complexes form at different rates depending on the acid and its concentration and have a varying influence on chromium deposition. For the development of a technical bath, care must be taken to ensure that the molar ratios between chromium and carboxylic acids can be controlled. This is possible with the HPLC method presented here.
https://doi.org/10.1149/1945-7111/abd1f4
Electrogravimetry and structural properties of thin silicon layers deposited in sulfolane and ionic liquid electrolytes. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 12 (2020), 51, S. 57526-57538
Potentiostatic deposition of silicon is performed in sulfolane (SL) and ionic liquid (IL) electrolytes. Electrochemical quartz crystal microbalance with damping monitoring (EQCM-D) is used as main analytical tool for the characterization of the reduction process. The apparent molar mass (Mapp) is applied for in situ estimation of the layer contamination. By means of this approach, appropriate electrolyte composition and substrate type are selected to optimize the structural properties of the layers. The application of SL electrolyte results in silicon deposition with higher efficiency compared to the IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP][TFSI]. This has been associated with the instability of the IL in the presence of silicon tetrachloride and the enhanced incorporation of IL decomposition products into the growing silicon deposit. X-ray photoelectron spectroscopy (XPS) analysis supports the results about the layer composition, as suggested from the microgravimetric experiments. Attention has been given to the impact of practically relevant substrates (i.e., Cu, Ni, and vitreous carbon) on the reduction process. An effective deposition can be carried out on the metal electrodes in both electrolytes due to accelerated reaction kinetics for these types of substrates. However, on vitreous carbon (VC), a successful reduction of SiCl4 can only be accomplished in the IL, while the electroreduction process in SL is dominated by the decomposition of the electrolyte. For short deposition times, the scanning electron microscopy (SEM) images display rough morphologies in the nanometer range, which evolve further to structures with increased length scale of the surface roughness. The development of a rough interface during deposition, resulting in QCM damping at advanced stages of the process, is interpreted by a model accounting for the resistive force caused by the interaction of the liquid with a nonuniform layer interface. By using this approach, the individual contributions of the surface roughness and viscoelastic effects to the measured damping values are estimated.
https://doi.org/10.1021/acsami.0c14694
Trivalent chromium based conversion coatings containing cobalt on the zinc plated steel. - Ilmenau : Universitätsbibliothek, 2020. - 1 Online-Ressource (XVIII, 144 Blätter, Blatt XIX-XLVIII)
Technische Universität Ilmenau, Dissertation 2020
Im Zuge neuer EU-Direktiven wurde die Verwendung von Cr(VI)-Verbindungen stark reglementiert. In der Oberflächentechnik wurde daraufhin sechswertiges Chrom durch sicherere und gleichzeitig effektive Passivierungen auf Cr(III)-Basis ersetzt. Der Korrosionsschutz von Cr(VI)-Beschichtungen ohne Wärmebehandlung ist im Allgemeinen besser. In bisher durchgeführten Untersuchungen zeigte sich, dass durch Zusatz von Übergangsmetallionen der Korrosionsschutz der Cr(III)-Passivierungsschicht verbessert werden kann. In dieser Arbeit wird der Einfluss der Zusammensetzung von Cr(III)-Passivierung mit Kobaltanteil auf die Bildung und die Struktur von Konversionsschichten auf verzinkten Substraten untersucht. Auf den verzinkten Stahl wurden Modelllösungen mit zwei verschiedenen Komplexbildnern, nämlich Fluorid und Oxalat, mit und ohne Kobalt aufgetragen. Rasterelektronenmikroskopie (REM) und Rasterkraftmikroskopie zeigten Oberflächenmorphologien mit mikrostrukturellen Defekten. In Anwesenheit von Kobalt wurden die Schichten gleichmäßiger. Die elementare Zusammensetzung der Schichten wurde mit der Augerelektronenspektroskopie (AES) untersucht. Die Mengen an Cr und Co in den Beschichtungen wurden mit Hilfe der optischen Plasma-Emissionsspektroskopie (ICP-OES) bestimmt. Sowohl AES als auch ICP-OES zeigten Co-Gehalte in den Schichten. Mit Hilfe eines thermodynamischen Modells wurde die Konzentration von Cr(III)-, Zn(II)- und Co(II)-Spezies in der Behandlungslösung im pH-Bereich von 0,0 bis 14,0 und auch der minimale pH-Wert für die Abscheidung der Metallionen in der entsprechenden Lösung berechnet. Die Ergebnisse der Korrosionstests (Polarisationsmessung und elektrochemische Impedanzspektroskopie) legen nahe, dass die Bildung einer dichten Schicht für eine gute Korrosionsbeständigkeit entscheidend ist. Außerdem wurde der Bildungsmechanismus von Cr(VI) in den Schichten untersucht. Die Anwesenheit von Cr(VI) wurde mittels Spektrophotometrie nachgewiesen. Die Morphologie und Struktur der Filme wurden per REM beobachtet. Die Gesamtwassermenge in den Schichten wurde mittels Karl-Fischer-Titration gemessen. Es zeigte sich, dass die Morphologie des fluoridhaltigen Films mit einer hohen Dichte an Mikroporen die Wahrscheinlichkeit eines Wassereinschlusses erhöht. Dies führte zu einer Oxidation von Cr(III) zu Cr(VI) durch Sauerstoff in Gegenwart von Wasser bei erhöhten Temperaturen.
https://nbn-resolving.org/urn:nbn:de:gbv:ilm1-2020000368
Ni3N-coated Ni nanorod arrays for hydrogen and oxygen evolution in electrochemical water splitting. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 3 (2020), 11, S. 10986-10995
Im Titel ist "3" tiefgestellt
Designing high efficiency non-noble metal catalysts for electrochemical hydrogen and oxygen evolution reactions (HER and OER) is a challenging and promising task. In the present work, a large-scale self-supported black nickel sheet composed of nickel nanorod arrays (B-Ni) was successfully fabricated via electroplating with a nanostructured Si template assisted strategy, and Ni3N coating layer was coated on the structured surface followed by a nitrogen plasma treatment with different treatment durations. The black color is due to the immensely enhanced light absorption through the surface nanostructures with high aspect ratio. The samples show promising catalytic performance when used as electrochemical catalysts for both HER and OER in alkaline electrolyte. Benefiting from the nanostructure and the Ni3N coating, B-Ni_N2_10 min exhibits low onset potentials of 1.560 and 0.165 V at a current density of 10 mA/cm2 for OER and HER, respectively. The calculated electrochemical surface area (ECSA) for B-Ni is 10 times higher than the pristine Ni sheet (P-Ni), while after nitrogen plasma treatment, the ECSA for B-Ni_N2_10 min is 21 times higher than that of the P-Ni. In addition, all the catalysts show good electrochemical stabilities. All the improvements for the electrochemical performances suggest that nanostructured nickel nitride could be a promising inexpensive catalyst system for both OER and HER processes.
https://doi.org/10.1021/acsanm.0c02222
Physics-based modeling and parameter identification for lithium ion batteries under high current discharge conditions. - In: Journal of the Electrochemical Society, ISSN 1945-7111, Volume 167 (2020), number 14, 140549
Extreme scenarios of high discharge current must be understood for better battery management system design. Physics-based modeling can give a better insight into the battery response but can be challenging due to the large number of parameters. In this work, an electrochemical pseudo-2D model is developed and used in the parameter identification and validated under high current discharge conditions. Commercial 18650 cells with maximum rated current of 20 A (13.3 C) are characterized with discharge rates up to 40 C under controlled thermal conditions. The proposed three-step parameter identification procedure starts with the open circuit voltage being used to estimate the equilibrium potentials. In a second step, kinetic parameters are identified under high current aided by a parameter sensitivity analysis and parameter optimization with an evolutionary algorithm. The third step is the verification by comparing simulation results with measurements resulting in root main square error under 89 mV for currents until 26.6 C. Limits of the model are explored in the 33.3 C case, where a parameter re-fit shows that polarization effects change for very high current.
https://doi.org/10.1149/1945-7111/abc726
New electroplating processes from ionic liquids (GALACTIF) : subproject: Deposition of pure and alloyed refractory metals from ionic liquids
Verbundname: Neue galvanotechnische Beschichtungsprozesse aus ionischen Flüssigkeiten (GALACTIF); Teilvorhaben: Abscheidung von reinen und legierten Refraktärmetallschichten aus ionischen Flüssigkeiten : Laufzeit des Vorhabens: 01.06.2016-29.02.2020, Berichtzeitraum: 01.06.2016-29.02.2020. - Ilmenau : [Technische Universität Ilmenau, Fachgebiet Elektrochemie und Galvanotechnik]. - 1 Online-Ressource (69 Seiten, 4,26 MB)Förderkennzeichen BMBF 13XP5017F
https://doi.org/10.2314/KXP:1736013130
InP(100) surfaces for efficient photoelectrochemical water splitting. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), HL 34.2
Surface modification and charge carrier dynamics of materials and structures for semiconductor-based solar water splitting applications under operation conditions. - In: DPG-Frühjahrstagung (DPG Spring Meeting) of the Condensed Matter Section (SKM) together with the DPG Division Environmental Physics and the Working Groups Accelerator Physics; Equal Opportunities; Energy; Industry and Business; Physics, Modern IT and Artificial Intelligence, Young DPG, (2020), HL 75.25
Influence of thermal treatment on the magnetic properties and morphology of electrodeposited Fe-Co films. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 513 (2020), 167204
Fe-Co films were prepared by electrodeposition from an electrolyte containing citric acid and annealed afterwards at different temperatures up to 700 ˚C. The grain sizes of the deposits increased from 11 nm to 30 nm with increasing annealing temperature, which lead to changes in magnetic properties of deposits. SQUID measurements indicate that there is a difference between the coercive force, Hc, of the as deposited samples (17 Oe) and the heat-treated samples (25-40 Oe) with a measurement error of 1-2 Oe. The remnant magnetization, Mr, decreased from 190 ± 12 emu/cm^3 for the as deposited to 75 ± 5 emu/cm^3 for the annealed samples, respectively. The saturation magnetization, Ms, seems not to be influenced strongly by the thermal treatment, with the only exception for the samples annealed at 500 ˚C. Thus, Ms has a slightly decreasing tendency from 1880 ± 90 emu/cm^3 for the as-deposited samples to 1780 ± 85 emu/cm^3 for samples annealed at 700 ˚C. The biggest value for Ms (2100 ± 105 emu/cm^3) was obtained if the samples were annealed at 500 ˚C. The thermal treatment generated cracks in the deposits. Interestingly, these cracks had a regular rectangular shape only if the deposits were annealed at 600 ˚C. The coercivity of the layers annealed at 600 ˚C was lower compared to layers annealed at the other temperatures. Magnetic force microscopy measurements indicated the magnetic domain distribution and the topography of the annealed deposits. The deposits showed the best soft magnetic properties if annealed between 500 and 600 ˚C.
https://doi.org/10.1016/j.jmmm.2020.167204