Morphological and compositional mapping of supersaturated AuNi alloy nanoparticles fabricated by solid state dewetting. - In: Applied surface science advances, ISSN 2666-5239, Bd. 4 (2021), 100082, insges. 6 S.
The solid state dewetting (SSD) of metallic bilayers is a straightforward method for the fabrication of alloy nanoparticles. In particular, alloys that present a gap of miscibility offer a rich phenomenology regarding not only the particle formation but also the composition of their phases. In the present work, AuNi precursor bilayers have been annealed at different temperatures and times to produce AuNi alloy nanoparticles. The evolution of the shape, size, and interparticle distance as well as the composition of the different phases formed in the nanoparticles, allow to unravel the role of the annealing temperatures and times for the fabrication of AuNi supersaturated alloys. Furthermore, the results offer a morphological and compositional map for the fabrication of AuNi alloys nanoparticles of different shapes, sizes, and compositions. Therefore, this map is a useful tool for the tailored design of supersaturated or decomposed nanoparticles by SSD.
https://doi.org/10.1016/j.apsadv.2021.100082
Achieving very high cycle fatigue performance of Au thin films for flexible electronic applications. - In: Journal of materials science & technology, ISSN 1941-1162, Bd. 89 (2021), S. 107-113
https://doi.org/10.1016/j.jmst.2021.02.025
Facile synthesis of a binder-free 3D Ni/NiO microwire network with a nanostructured fiber surface for a negative electrode in Li-ion battery. - In: Journal of applied electrochemistry, ISSN 1572-8838, Bd. 51 (2021), 5, S. 815-828
Binder-free Ni/NiO microwire hybrid network with a nanostructured surface is synthesized by employing a facile and low-cost method, involving one-pot synthesis of Ni microwires, followed by their partial oxidation in air atmosphere. A combination of imaging, diffraction, thermodynamic and electrochemical methods has been applied to reveal the impact of the synthesis conditions on the energy storage performance of the Ni/NiO microwire networks. The thermal conditions for the synthesis have been optimized by means of thermogravimetric (TGA/DSC) analysis, where an appropriate temperature (T = 400 ˚C) for obtaining a low-defect NiO phase has been determined. The performed electrochemical characterisation of the materials has shown that setting a low temperature for the synthesis enables high reversible capacity and better cycling stability of the binder-free materials. When the Ni/NiO network structures are deposited by a conventional slurry-based technology, involving polymer binder and conductive additive, the high capacity and cycling stability of the anodes are preserved, independent of the temperature conditions of synthesis. Electrochemical impedance spectroscopy is applied to support the interpretation of our results.
https://doi.org/10.1007/s10800-021-01541-5
Zweidimensionale Simulation von Hull-Zellen. - In: Galvanotechnik, ISSN 0016-4232, Bd. 112 (2021), 3, S. 301-311
Enhanced cycling performance of binder free silicon-based anode by application of electrochemically formed microporous substrate. - In: Electrochimica acta, ISSN 1873-3859, Bd. 380 (2021), 138216, S. 1-9
In this work, an electrochemically formed porous Cu current collector (p-Cu) is utilized for the development of a high-performance binder-free silicon anode. Two electrolyte compositions based on sulfolane (SL) and [BMP][TFSI] ionic liquid (IL) are implemented for silicon deposition. The electrochemical experiments confirm the advantages of applying the p-Cu structure in terms of specific capacity, rate capability, and long-term cycling, where the best electrochemical properties have been observed for the Si deposited from SL electrolyte. The Si-based p-Cu anodes formed in SL display stable 2500 mAh g^-1 reversible capacity during the first 250 cycles and promising capacity retention. Compared to this result, the cycling performance of the same type of material deposited on flat Cu foil (f-Cu) showed significantly reduced capacity (1400 mAh g^-1) and inferior cycling performance. The positive effect can be attributed to the improved mechanical stability of the active material and accelerated ionic transport in the porous structure of the anode. The improved functional properties of the electrochemically deposited Si from SL electrolyte in p-Cu samples compared to those obtained in IL can be ascribed to differences in the chemical composition. While the layers deposited in SL electrolyte involve Si domains incorporated in a matrix containing C and O that offer high mechanical stability, the Si material obtained in IL is additionally influenced by N and F chemical species, resulting from active IL decomposition. These differences in the chemical surrounding of the Si domains are the primary reason for the inferior electrochemical performance of the material deposited from [BMP][TFSI] electrolyte. XPS analysis shows that the initial composition of the as deposited layers, containing a considerable amount of elemental Si, is changed after lithiation and that the electrochemical activity of the anode is governed by switching between the intermediate redox states of Si, where the carbon-oxygen matrix is also involved.
https://doi.org/10.1016/j.electacta.2021.138216
Electrodeposition of cuprous oxide on a porous copper framework for an improved photoelectrochemical performance. - In: Journal of materials science, ISSN 1573-4803, Bd. 56 (2021), 20, S. 11866-11880
https://doi.org/10.1007/s10853-021-06058-y
Solid-state dewetting of gold on stochastically periodic SiO2 nanocolumns prepared by oblique angle deposition. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 13 (2021), 9, S. 11385-11395
Im Titel ist "2" tiefgestellt
https://doi.org/10.1021/acsami.0c19327
Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting. - In: Journal of physics, ISSN 1361-6463, Bd. 54 (2021), 19, 195101, S. 1-12
The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm^-2 at -1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the native layer at cathodic potentials higher than -1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting.
https://doi.org/10.1088/1361-6463/abdb69
Anti-corrosive siloxane coatings for improved long-term performance of supercapacitors with an aqueous electrolyte. - In: Electrochimica acta, ISSN 1873-3859, Bd. 372 (2021), 137840, S. 1-15
This paper reports on the impact that the corrosion of the stainless steel current collectors has on the performance fade of a symmetric, carbon/carbon electrochemical capacitor, operating with an aqueous electrolyte (1M Na2SO4). The results obtained by applying electrochemical ageing protocols (voltage-holding tests) confirm that the current collector of the positive electrode undergoes tremendous degradation during 200 h in the charged state. To prevent the detrimental impact of the corrosion, a hydrophobic siloxane coating has been successfully applied. In the case of siloxane-protected current collectors that are subjected to identical ageing protocols, no significant deterioration in the electrochemical capacitor performance was observed. The siloxane coating reduces the electrochemical corrosion rate of 316L stainless steel significantly, as the potentiodynamic polarization tests and the electrochemical impedance spectroscopy results show. The presence of the coating is demonstrated by the water contact angle measurements, atomic force microscopy and energy-dispersive X-ray spectroscopy analysis.
https://doi.org/10.1016/j.electacta.2021.137840
Layered WS2 thin films prepared by sulfurization of sputtered W films. - In: Applied surface science, Bd. 544 (2021), 148719
Im Titel ist "2" tiefgestellt
We present structural, optical and electrical investigations of layered WS2 films prepared on tungsten. A two-step technique has been used to synthesize layered WS2 films using sulfurization of W films sputtered with thinner (1 and 2 nm) and thicker (14 and 28 nm) thicknesses at 800 ˚C. XRD analysis revealed that the examined films are polycrystalline with texture and have a 2H-WS2 hexagonal microstructure. Using Raman spectroscopy with the 532 nm laser excitation, the presence of E12g and A1g vibration modes was observed and the layered nature of WS2 was confirmed. FE SEM observations showed two different surface morphologies. The samples grown on thinner W films were not compact over the surface and agglomeration of nanosize grains in combination of triangles and flakes was visible. In another group the surface was lamellar and contained plenty of nanorods embedded vertically and/or inclined at different angles to the surface. Layered WS2 films exhibited a direct band gap in the range of 2.1-2.5 eV and they were n-type semiconductors with the sheet resistance in the order of several MΩ at room temperature.
https://doi.org/10.1016/j.apsusc.2020.148719