Mechanochemical polymerization – controlling a polycondensation reaction between a diamine and a dialdehyde in a ball mill

The mechanochemical polycondensation between a diamine and a dialdehyde constitutes a sustainable alternative to classical solvent-based polymerization reactions. This process not only allows for a higher conversion and a shorter reaction time as compared to standard solvent-based syntheses of this conjugated polymer, but the reaction can also be adjusted by the energy introduced via the ball mill

Titanium Niobium Oxide Ti2 Nb10 O29 /Carbon Hybrid Electrodes Derived by Mechanochemically Synthesized Carbide for High-Performance Lithium-Ion Batteries

This work introduces the facile and scalable two‐step synthesis of Ti2Nb10O29 (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 LiMn2O4

The mechanochemical Scholl reaction – a solvent-free and versatile graphitization tool

Herein, we report on the mechanochemical Scholl reaction of dendritic oligophenylene precursors to produce benchmark nanographenes such as hexa-peri-hexabenzocoronene (HBC), triangular shaped C60 and expanded C222 under solvent-free conditions. The solvent-free approach overcomes the bottleneck of solubility limitation in this well-known and powerful reaction. The mechanochemical approach allows tracking the reaction process by in situ pressure measurements. The quality of produced nanographenes has been confirmed by MALDI-TOF mass spectrometry and UV-Vis absorption spectroscopy. This approach paves the way towards gram scale and environmentally benign synthesis of extended nanographenes and possibly graphene nanoribbons suitable for application in carbon based electronics or energy applications

Textural Characterization of Micro- and Mesoporous Carbons Using Combined Gas Adsorption and n-Nonane Preadsorption

Porous carbon and carbide materials with different structures were characterized using adsorption of nitrogen at 77.4 K before and after preadsorption of n-nonane. The selective blocking of the microporosity with n-nonane shows that ordered mesoporous silicon carbide material (OM-SiC) is almost exclusively mesoporous whereas the ordered mesoporous carbon CMK-3 contains a significant amount of micropores (25%). The insertion of micropores into OM-SiC using selective extraction of silicon by hot chlorine gas leads to the formation of ordered mesoporous carbide-derived carbon (OM-CDC) with a hierarchical pore structure and significantly higher micropore volume as compared to CMK-3, whereas a CDC material from a nonporous precursor is exclusively microporous. Volumes of narrow micropores, calculated by adsorption of carbon dioxide at 273 K, are in linear correlation with the volumes blocked by n-nonane. Argon adsorption measurements at 87.3 K allow for precise and reliable calculation of the pore size distribution of the materials using density functional theory (DFT) methods

Methane Hydrate in Confined Spaces: An Alternative Storage System

Methane hydrate inheres the great potential to be a nature‐inspired alternative for chemical energy storage, as it allows to store large amounts of methane in a dense solid phase. The embedment of methane hydrate in the confined environment of porous materials can be capitalized for potential applications as its physicochemical properties, such as the formation kinetics or pressure and temperature stability, are significantly changed compared to the bulk system. We review this topic from a materials scientific perspective by considering porous carbons, silica, clays, zeolites, and polymers as host structures for methane hydrate formation. We discuss the contribution of advanced characterization techniques and theoretical simulations towards the elucidation of the methane hydrate formation and dissociation process within the confined space. We outline the scientific challenges this system is currently facing and look on possible future applications for this technology.L.B. gratefully acknowledges the Daimler und Benz Stiftung (award number 32–01/16) and the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF) for support of the Mechanocarb project (award number 03SF0498). M.E.C. acknowledges the Alexander von Humboldt foundation for financial support. J.S.A. acknowledges financial support from MINECO (Project MAT2016-80285-P) and Generalitat Valenciana (PROMETEOII/2014/004)

Carbon onion / sulfur hybrid cathodes via inverse vulcanization for lithium sulfur batteries

A sulfur–1,3-diisopropenylbenzene copolymer was synthesized by ring-opening radical polymerization and hybridized with carbon onions at different loading levels. The carbon onion mixing was assisted by shear in a two-roll mill to capitalize on the softened state of the copolymer. The sulfur copolymer and the hybrids were thoroughly characterized in structure and chemical composition, and finally tested by electrochemical benchmarking. An enhancement of specific capacity was observed over 140 cycles at higher content of carbon onions in the hybrid electrodes. The copolymer hybrids demonstrate a maximum initial specific capacity of 1150 mA h gsulfur−1 (850 mA h gelectrode−1) and a low decay of capacity to reach 790 mA h gsulfur−1 (585 mA h gelectrode−1) after 140 charge/discharge cycles. All carbon onion/sulfur copolymer hybrid electrodes yielded high chemical stability, stable electrochemical performance superior to conventional melt-infiltrated reference samples having similar sulfur and carbon onion content. The amount of carbon onions embedded in the sulfur copolymer has a strong influence on the specific capacity, as they effectively stabilize the sulfur copolymer and sterically hinder the recombination of sulfur species to the S8 configuration

The mechanochemical Friedel‐Crafts polymerization as a solvent‐free cross‐linking approach toward microporous polymers

Herein we report the mechanochemical Friedel‐Crafts alkylation of 1,3,5‐triphenylbenzene (TPB) with two organochloride cross‐linking agents, dichloromethane (DCM) and chloroform (CHCl₃), respectively. During a thorough milling parameter evaluation, the DCM‐linked polymers were found to be flexible and extremely sensitive toward parameter changes, which even enables the synthesis of a polymer with a SSABET of 1670 m²/g, on par with the solution‐based reference. Contrary, CHCl₃‐linked polymers are exhibiting a rigid structure, with a high porosity that is widely unaffected by parameter changes. As a result, a polymer with a SSABET of 1280 m²/g could be generated in as little as 30 minutes, outperforming the reported literature analogue in terms of synthesis time and SSABET. To underline the environmental benefits of our fast and solvent‐free synthesis approach, the green metrics are discussed, revealing an enhancement of the mass intensity, mass productivity and the E‐factor, as well as of synthesis time and the work‐up in comparison to the classical synthesis. Therefore, the mechanochemical polymerization is presented as a versatile tool, enabling the generation of highly porous polymers within short reaction times, with a minimal use of chlorinated cross‐linker and with the possibility of a post polymerization modification

Illuminating solid gas storage in confined spaces – methane hydrate formation in porous model carbons

Methane hydrate nucleation and growth in porous model carbon materials illuminates the way towards the design of an optimized solid-based methane storage technology. High-pressure methane adsorption studies on pre-humidified carbons with well-defined and uniform porosity show that methane hydrate formation in confined nanospace can take place at relatively low pressures, even below 3 MPa CH4, depending on the pore size and the adsorption temperature. The methane hydrate nucleation and growth is highly promoted at temperatures below the water freezing point, due to the lower activation energy in ice vs. liquid water. The methane storage capacity via hydrate formation increases with an increase in the pore size up to an optimum value for the 25 nm pore size model-carbon, with a 173% improvement in the adsorption capacity as compared to the dry sample. Synchrotron X-ray powder diffraction measurements (SXRPD) confirm the formation of methane hydrates with a sI structure, in close agreement with natural hydrates. Furthermore, SXRPD data anticipate a certain contraction of the unit cell parameter for methane hydrates grown in small pores.L. B. gratefully acknowledges the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF) for support of the Mechanocarb project (award number 03SF0498). J. S. A. acknowledges financial support from MINECO (project MAT-2013-45008-p) and Generalitat Valenciana (PROMETEOII/2014/004). V. B. thanks the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF) for financial support (project No. 05K13OD3)