Publikationen

Efficient separation of specific ions from aqueous media is crucial for advanced water treatment and resource recovery. Flow electrode capacitive deionization (FCDI) offers potential for selective ion removal through continuous operation. This study evaluates the performance of selective cation separation using a commercial activated carbon slurry in a multi-ion solution of monovalent (Li+, Na+, K+) and bivalent (Ca2+, Mg2+) cations. We assess ion removal and cation selectivity under different operational parameters, such as applied potential, slurry flow rate, and feed water flow rate. Our data show that bivalent cations, namely Ca2+ and Mg2+, are preferentially removal due to their higher charge-to-size ratio, aligning with hydrated ion sizes. The highest separation rate was observed for Ca2+ (5.7 μg cm−2 min−1), and the lowest for Li+ (0.2 μg cm−2 min−1). At the highest applied voltage (1.2 V), charge efficiencies reached 70 %, with an energy consumption of 41 Wh mol−1 for nearly complete cation removal. Optimal conditions were identified with a slurry flow rate of 6 mL min−1, feed water flow rate of 2 mL min−1, activated carbon content of 10 mass%, 1 mass% carbon black, and a cell voltage of 1.2 V. These findings highlight the importance of optimizing operational parameters to enhance ion removal.

Trotz erheblichen Interesses an heteroatomhaltigen konjugierten Polymeren sind Beispiele mit schwereren Elementen des p-Blocks im Konjugationspfad rar. Die kürzlich beschriebene Metathese schwererer acyclischer Diene (HADMET) ermöglichte die Synthese eines Ge=Ge-Doppelbindungen enthaltenden Polymers, wenn auch eines unlöslichen mit begrenztem Polymerisationsgrad. Durch Einführung langer Alkylketten erhielten wir nun lösliche Vertreter mit – nach diffusionsabhängiger NMR-Spektroskopie (DOSY) und dynamischer Lichtstreuung (DLS) – nahezu unendlichen Polymerisationsgraden. UV/Vis und NMR-Daten bestätigen das Vorliegen von σ,π-Konjugation entlang der Silylen-Phenylen-Verknüpfungen zwischen den Ge=Ge-Einheiten. Günstige intermolekulare Dispersionswechselwirkungen führen zu leiterartigen, zylindrischen Aggregaten, wie durch Röntgendiffraktometrie (XRD), Kleinwinkel-Röntgenstreuung (SAXS) und DLS bestätigt. AFM- und TEM-Bilder abgeschiedener dünner Schichten offenbaren eine lamellare Anordnung ausgedehnter Polymerbündel.

Despite considerable interest in heteroatom-containing conjugated polymers, there are only few examples with heavier p-block elements in the conjugation path. The recently reported heavier acyclic diene metathesis (HADMET) allowed for the synthesis of a polymer containing Ge=Ge double bonds—albeit insoluble and with limited degree of polymerization. By incorporation of long alkyl chains, we now obtained soluble representatives, which exhibit degrees of polymerization near infinity according to diffusion-ordered NMR spectroscopy (DOSY) and dynamic light scattering (DLS). UV/Vis and NMR data confirm the presence of σ,π-conjugation across the silylene-phenylene linkers between the Ge=Ge double bonds. Favorable intermolecular dispersion interactions lead to ladder-like cylindrical assemblies as confirmed by X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and DLS. AFM and TEM images of deposited thin films reveal lamellar ordering of extended polymer bundles.

This study explores the potential of re-purposing end-of-life commercial supercapacitors as electrochemical desalination cells, aligning with circular economy principles. A commercial 500-Farad supercapacitor was disassembled, and its carbon electrodes underwent various degrees of modification. The most straightforward modification involved NaOH-etching of the aluminum current collector to produce free-standing carbon films. More advanced modifications included CO2 activation and binder-added wet processing of the electrodes. When evaluated as electrodes for electrochemical desalination via capacitive deionization of low-salinity (20 mM) NaCl solutions, the minimally modified NaOH-etched carbon electrodes achieved an average desalination capacity of 5.8 mg g−1 and a charge efficiency of 80 %. In contrast, the CO2-activated, wet-processed electrodes demonstrated an improved desalination capacity of 7.9 mg g−1 and a charge efficiency above 90 % with stable performance over 20 cycles. These findings highlight the feasibility and effectiveness of recycling supercapacitors for sustainable water desalination applications, offering a promising avenue for resource recovery and re-purposing in pursuing environmental sustainability.

Organic materials have emerged as highly efficient electrodes for electrochemical energy storage, offering sustainable solutions independent from non-renewable resources. In this study, we showcase that mesoscale engineering can dramatically transform the electrochemical features of a molecular organic carboxylic anode. Through a sustainable, energy-efficient and environmentally benign self-assembly strategy, we developed a network of organic nanowires formed during water evaporation directly on the copper current collector, circumventing the need for harmful solvents, typically employed in such processes. The organic nanowire anode delivers high capacity and rate, reaching 1888 mA h g−1 at 0.1 A g−1 and maintaining 508 mA h g−1 at a specific current of 10 A g−1. Moreover, it exhibits superior thermal management during lithiation in comparison to graphite and other organic anodes. Comprehensive electrochemical evaluations and theoretical calculations reveal rapid charge transport mechanisms, with lithium diffusivity rates reaching 5 × 10−9 cm2 s−1, facilitating efficient and rapid interactions with 24 lithium atoms per molecule. Integrated as the negative electrode in a lithium-ion capacitor, paired with a commercially available porous carbon, the cell delivers a specific energy of 156 W h kg−1 at a specific power of 0.34 kW kg−1 and 60.2 W h kg−1 at 19.4 kW kg−1, establishing a benchmark among state-of-the-art systems in the field. These results underscore the critical role of supramolecular organization for optimizing the performance of organic electrode materials for practical and sustainable energy storage technologies.

Polyacrylamide (PAAm) hydrogels are widely adopted as 2D-model soft substrates for investigating cell-material interactions in a controlled in vitro environment. They offer facile synthesis, tunable physico-chemical properties, diverse biofunctionalization routes, optical transparency, mouldability in a range of geometries and shapes, and compatibility with living cells. PAAm hydrogels can be engineered to reconstruct physiologically relevant biointerfaces, like cell-matrix or cell–cell interfaces, featuring biochemical, mechanical, and topographical cues present in the extracellular environment. This Review provides a materials science perspective on PAAm material properties, fabrication, and modification strategies relevant to cell studies, highlighting their versatility and potential to address a wide range of biological questions. Current routes are presented to integrate cell-instructive features, such as 2D patterns, 2.5D surface topographies, or mechanical stiffness gradients. Finally, the recent advances are emphasized toward dynamic PAAm hydrogels with on-demand control over hydrogel properties as well as electrically conductive PAAm hydrogels for bioelectronics.

Fingertip friction is a key component of tactile perception. In active tactile exploration, friction forces depend on the applied normal force and on the sliding speed chosen. We have investigated whether humans perceive the speed dependence of friction for textured surfaces of materials, which show either increase or decrease of the friction coefficient with speed. Participants perceived the decrease or increase when the relative difference in friction coefficient between fast and slow sliding speed was more than 20 %. The fraction of comparison judgments which were in agreement with the measured difference in friction coefficient did not depend on variations in the applied normal force. The results indicate a perceptual constancy for fingertip friction with respect to self-generated variations of sliding speed and applied normal force.

Lithium-ion batteries (LIBs) are at the forefront of technological innovation in the current global energy-transition paradigm, driving surging demand for electric vehicles and renewable energy-storage solutions. Despite their widespread use and superior energy densities, the environmental footprint and resource scarcity associated with LIBs necessitate sustainable recycling strategies. This comprehensive review critically examines the existing landscape of battery recycling methodologies, including pyrometallurgical, hydrometallurgical, and direct recycling techniques, along with emerging approaches such as bioleaching and electrochemical separation. Our analysis not only underscores the environmental and efficiency challenges posed by conventional recycling methods but also highlights the promising potential of electrochemical techniques for enhancing selectivity, reducing energy consumption, and mitigating secondary waste production. By delving into recent advancements and juxtaposing various recycling methodologies, we pinpoint electrochemical recycling as a pivotal technology for efficiently recovering valuable metals, such as Li, Ni, Co, and Mn, from spent LIBs in an environmentally benign manner. Our discussion extends to the scalability, economic viability, and future directions of electrochemical recycling, and advocates for their integration into global battery-recycling infrastructure to address the dual challenges of resource depletion and environmental sustainability.

Cofactor regeneration systems are of major importance for the applicability of oxidoreductases in biocatalysis. Previously, geranylgeranyl reductases have been investigated for the enzymatic reduction of isolated C=C bonds. However, an enzymatic cofactor-regeneration system for in vitro use is lacking. In this work, we report a ferredoxin from the archaea Archaeoglobus fulgidus that regenerates the flavin of the corresponding geranylgeranyl reductase. The proteins were heterologously produced, and the regeneration was coupled to a ferredoxin reductase from Escherichia coli and a glucose dehydrogenase from Bacillus subtilis, thereby enabling the reduction of isolated C=C bonds by purified enzymes. The system was applied in crude, cell-free extracts and gave conversions comparable to those of a previous method using sodium dithionite for cofactor regeneration. Hence, an enzymatic approach to the reduction of isolated C=C bonds can be coupled with common systems for the regeneration of nicotinamide cofactors, thereby opening new perspectives for the application of geranylgeranyl reductases in biocatalysis.