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- ItemSelf-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity(Weinheim : Wiley-VCH, 2023) Mohamed, Mana Abdirahman; Arnold, Stefanie; Janka, Oliver; Quade, Antje; Presser, Volker; Kickelbick, GuidoInorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C6H10N2]2[Mo8O26] ⋅ 6 H2O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C6H9N2]4[NH4]2[Mo7O24] ⋅ 3 H2O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g−1 at 100 mA g−1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li2MoO4 and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.
- ItemDye-Loaded Mechanochromic and pH-Responsive Elastomeric Opal Films(Weinheim : Wiley-VCH, 2021) Winter, Tamara; Boehm, Anna; Presser, Volker; Gallei, MarkusIn this work, the preparation and fabrication of elastomeric opal films revealing reversible mechanochromic and pH-responsive features are reported. The core–interlayer–shell (CIS) particles are synthesized via stepwise emulsion polymerization leading to hard core (polystyrene), crosslinked interlayer (poly(methyl methacrylate-co-allyl methacrylate), and soft poly(ethyl acrylate-co-butyl acrylate-co-(2-hydroxyethyl) methacrylate) shell particles featuring a size of 294.9 ± 14.8 nm. This particle architecture enables the application of the melt-shear organization technique leading to elastomeric opal films with orange, respectively, green brilliant reflection colors dependent on the angle of view. Moreover, the hydroxyl moieties as part of the particle shell are advantageously used for subsequent thermally induced crosslinking reactions enabling the preparation of reversibly tunable mechanochromic structural colors based on Bragg's law of diffraction. Additionally, the CIS particles can be loaded upon extrusion or chemically by a postfunctionalization strategy with organic dyes implying pH-responsive features. This convenient protocol for preparing multi-responsive, reversibly stretch-tunable opal films is expected to enable a new material family for anti-counterfeiting applications based on external triggers.
- ItemNanoporous Block Copolymer Membranes with Enhanced Solvent Resistance Via UV-Mediated Cross-Linking Strategies(Weinheim : Wiley-VCH, 2021) Frieß, Florian V.; Hu, Qiwei; Mayer, Jannik; Gemmer, Lea; Presser, Volker; Balzer, Bizan N.; Gallei, MarkusIn this work, a block copolymer (BCP) consisting of poly((butyl methacrylate-co-benzophenone methacrylate-co-methyl methacrylate)-block-(2-hydroxyethyl methacrylate)) (P(BMA-co-BPMA-co-MMA)-b-P(HEMA)) is prepared by a two-step atom-transfer radical polymerization (ATRP) procedure. BCP membranes are fabricated applying the self-assembly and nonsolvent induced phase separation (SNIPS) process from a ternary solvent mixture of tetrahydrofuran (THF), 1,4-dioxane, and dimethylformamide (DMF). The presence of a porous top layer of the integral asymmetric membrane featuring pores of about 30 nm is confirmed via scanning electron microscopy (SEM). UV-mediated cross-linking protocols for the nanoporous membrane are adjusted to maintain the open and isoporous top layer. The swelling capability of the noncross-linked and cross-linked BCP membranes is investigated in water, water/ethanol mixture (1:1), and pure ethanol using atomic force microscopy, proving a stabilizing effect of the UV cross-linking on the porous structures. Finally, the influence of the herein described cross-linking protocols on water-flux measurements for the obtained membranes is explored. As a result, an increased swelling resistance for all tested solvents is found, leading to an increased water flux compared to the pristine membrane. The herein established UV-mediated cross-linking protocol is expected to pave the way to a new generation of porous and stabilized membranes within the fields of separation technologies.
- ItemRings and Chains: Synthesis and Characterization of Polyferrocenylmethylene(Weinheim : Wiley-VCH, 2021) Winter, Tamara; Haider, Wasim; Schießer, Alexander; Presser, Volker; Gallei, Markus; Schäfer, AndréThe synthesis and characterization of polyferrocenylmethylene (PFM) starting from dilithium 2,2-bis(cyclopentadienide)propane and a Me2C[1]magnesocenophane is reported. Molecular weights of up to Mw = 11 700 g mol–1 featuring a dispersity, Ð, of 1.40 can be achieved. The material is studied by different methods comprising nuclear magnetic resonance (NMR) spectroscopy, matrix-assisted laser desorption/ionization time of flight (MALDI-ToF) mass spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements elucidating the molecular structure and thermal properties of these novel polymers. Moreover, cyclic voltammetry (CV) reveals quasi-reversible oxidation and reduction behavior and communication between the iron centers. Also, the crystal structure of a related cyclic hexamer is presented
- ItemTitanium Niobium Oxide Ti2 Nb10 O29 /Carbon Hybrid Electrodes Derived by Mechanochemically Synthesized Carbide for High-Performance Lithium-Ion Batteries(Weinheim : Wiley-VCH, 2021) Budak, Öznil; Srimuk, Pattarachai; Aslan, Mesut; Shim, Hwirim; Borchardt, Lars; Presser, VolkerThis work introduces the facile and scalable two-step synthesis of Ti2 Nb10 O29 (TNO)/carbon hybrid material as a promising anode for lithium-ion batteries (LIBs). The first step consisted of a mechanically induced self-sustaining reaction via ball-milling at room temperature to produce titanium niobium carbide with a Ti and Nb stoichiometric ratio of 1 to 5. The second step involved the oxidation of as-synthesized titanium niobium carbide to produce TNO. Synthetic air yielded fully oxidized TNO, while annealing in CO2 resulted in TNO/carbon hybrids. The electrochemical performance for the hybrid and non-hybrid electrodes was surveyed in a narrow potential window (1.0-2.5 V vs. Li/Li+ ) and a large potential window (0.05-2.5 V vs. Li/Li+ ). The best hybrid material displayed a specific capacity of 350 mAh g-1 at a rate of 0.01 A g-1 (144 mAh g-1 at 1 A g-1 ) in the large potential window regime. The electrochemical performance of hybrid materials was superior compared to non-hybrid materials for operation within the large potential window. Due to the advantage of carbon in hybrid material, the rate handling was faster than that of the non-hybrid one. The hybrid materials displayed robust cycling stability and maintained ca. 70 % of their initial capacities after 500 cycles. In contrast, only ca. 26 % of the initial capacity was maintained after the first 40 cycles for non-hybrid materials. We also applied our hybrid material as an anode in a full-cell lithium-ion battery by coupling it with commercial LiMn2 O4 .
- ItemUnraveling the Electrochemical Mechanism in Tin Oxide/MXene Nanocomposites as Highly Reversible Negative Electrodes for Lithium-Ion Batteries(Weinheim : Wiley-VCH, 2023) Gentile, Antonio; Arnold, Stefanie; Ferrara, Chiara; Marchionna, Stefano; Tang, Yushu; Maibach, Julia; Kübel, Christian; Presser, Volker; Ruffo, RiccardoLithium-ion batteries are constantly developing as the demands for power and energy storage increase. One promising approach to designing high-performance lithium-ion batteries is using conversion/alloying materials, such as SnO2. This class of materials does, in fact, present excellent performance and ease of preparation; however, it suffers from mechanical instabilities during cycling that impair its use. One way to overcome these problems is to prepare composites with bi-dimensional materials that stabilize them. Thus, over the past 10 years, two-dimensional materials with excellent transport properties (graphene, MXenes) have been developed that can be used synergistically with conversion materials to exploit both advantages. In this work, a 50/50 (by mass) SnO2/Ti3C2Tz nanocomposite is prepared and optimized as a negative electrode for lithium-ion batteries. The nanocomposite delivers over 500 mAh g−1 for 700 cycles at 0.1 A g−1 and demonstrates excellent rate capability, with 340 mAh g−1 at 8 A g−1. These results are due to the synergistic behavior of the two components of the nanocomposite, as demonstrated by ex situ chemical, structural, and morphological analyses. This knowledge allows, for the first time, to formulate a reaction mechanism with lithium-ions that provides partial reversibility of the conversion reaction with the formation of SnO.
- ItemLayered Nano‐Mosaic of Niobium Disulfide Heterostructures by Direct Sulfidation of Niobium Carbide MXenes for Hydrogen Evolution(Weinheim : Wiley-VCH, 2022) Husmann, Samantha; Torkamanzadeh, Mohammad; Liang, Kun; Majed, Ahmad; Dun, Chaochao; Urban, Jeffrey J.; Naguib, Michael; Presser, VolkerMXene-transition metal dichalcogenide (TMD) heterostructures are synthesized through a one-step heat treatment of Nb2C and Nb4C3. These MXenes are used without delamination or any pre-treatment. Heat treatments accomplish the sacrificial transformation of these MXenes into TMD (NbS2) at 700 and 900 °C under H2S. This work investigates, for the first time, the role of starting MXene phase in the derivative morphology. It is shown that while treatment of Nb2C at 700 °C leads to the formation of pillar-like structures on the parent MXene, Nb4C3 produces nano-mosaic layered NbS2. At 900 °C, both MXene phases, of the same transition metal, fully convert into nano-mosaic layered NbS2 preserving the parent MXene's layered morphology. When tested as electrodes for hydrogen evolution reaction, Nb4C3-derived hybrids show better performance than Nb2C derivatives. The Nb4C3-derived heterostructure exhibits a low overpotential of 198 mV at 10 mA cm−2 and a Tafel slope of 122 mV dec−1, with good cycling stability in an acidic electrolyte.
- ItemHydrogel-Based Flexible Energy Storage Using Electrodes Based on Polypyrrole and Carbon Threads(Weinheim : Wiley-VCH, 2023) Ruthes, Jean G. A.; Deller, Andrei E.; Pameté, Emmanuel; Riegel‐Vidotti, Izabel C.; Presser, Volker; Vidotti, MarcioDeveloping new flexible and electroactive materials is a significant challenge to producing safe, reliable, and environmentally friendly energy storage devices. This study introduces a promising electrolyte system that fulfills these requirements. First, polypyrrole (PPy) nanotubes are electropolymerized in graphite-thread electrodes using methyl orange (MO) templates in an acidic medium. The modification increases the conductivity and does not compromise the flexibility of the electrodes. Next, flexible supercapacitors are built using hydrogel prepared from poly(vinyl alcohol) (PVA)/sodium alginate (SA) obtained by freeze–thawing and swollen with ionic solutions as an electrolyte. The material exhibits a homogenous and porous hydrogel matrix allowing a high conductivity of 3.6 mS cm−1 as-prepared while displaying great versatility, changing its electrochemical and mechanical properties depending on the swollen electrolyte. Therefore, it allows its combination with modified graphite-thread electrodes into a quasi-solid electrochemical energy storage device, achieving a specific capacitance (Cs) value of 66 F g−1 at 0.5 A g−1. Finally, the flexible device exhibits specific energy and power values of 19.9 W kg−1 and 3.0 Wh kg−1, relying on the liquid phase in the hydrogel matrix produced from biodegradable polymers. This study shows an environment friendly, flexible, and tunable quasi-solid electrolyte, depending on a simple swell experiment to shape its properties according to its application.
- ItemNovel Sb−SnO2 Electrode with Ti3+ Self-Doped Urchin-Like Rutile TiO2 Nanoclusters as the Interlayer for the Effective Degradation of Dye Pollutants(Weinheim : Wiley-VCH, 2023) Man, Shuaishuai; Yin, Zehao; Zhou, Shanbin; Pameté, Emmanuel; Xu, Lei; Bao, Hebin; Yang, Wenjing; Mo, Zhihong; Presser, Volker; Li, XuemingStable and efficient SnO2 electrodes are very promising for effectively degrading refractory organic pollutants in wastewater treatment. In this regard, we firstly prepared Ti3+ self-doped urchin-like rutile TiO2 nanoclusters (TiO2-xNCs) on a Ti mesh substrate by hydrothermal and electroreduction to serve as an interlayer for the deposition of Sb−SnO2. The TiO2-xNCs/Sb−SnO2 anode exhibited a high oxygen evolution potential (2.63 V vs. SCE) and strong ⋅OH generation ability for the enhanced amount of absorbed oxygen species. Thus, the degradation results demonstrated its good rhodamine B (RhB), methylene blue (MB), alizarin yellow R (AYR), and methyl orange (MO) removal performance, with the rate constant increased 5.0, 1.9, 1.9, and 4.7 times, respectively, compared to the control Sb−SnO2 electrode. RhB and AYR degradation mechanisms are also proposed based on the results of high-performance liquid chromatography coupled with mass spectrometry and quenching experiments. More importantly, this unique rutile interlayer prolonged the anode lifetime sixfold, given its good lattice match with SnO2 and the three-dimensional concave–convex structure. Consequently, this work paves a new way for designing the crystal form and structure of the interlayers to obtain efficient and stable SnO2 electrodes for addressing dye wastewater problems.